Development of a system for automatic control of a technological system. Development of an automated control system for the technological process of natural gas purification. control of the current value of the measured pressure
Technological parameters, objects of automatic control systems. Sensor and transducer concepts. Displacement transducers. Differential and bridge circuits for connecting sensors. Sensors of physical quantities - temperature, pressure, mechanical forces. Monitoring of media levels. Classification and diagrams of level gauges. Methods for controlling the flow rate of liquid media. Variable level and variable differential pressure flowmeters. Rotameters. Electromagnetic flowmeters. Implementation of flow meters and scope.Methods for controlling the density of suspensions. Manometric, weight and radioisotope density meters. Control of the viscosity and composition of suspensions. Automatic granulometers, analyzers. Moisture meters for enrichment products.
7.1 General characteristics of control systems. Sensors and Transducers
Automatic control is based on continuous and accurate measurement of input and output technological parameters of the beneficiation process.
It is necessary to distinguish between the main output parameters of the process (or a specific machine) that characterize the ultimate goal of the process, for example, the qualitative and quantitative indicators of processed products, and intermediate (indirect) technological parameters that determine the conditions of the process, the operating modes of the equipment. For example, for the process of coal beneficiation in a jigging machine, the main output parameters may be the yield and ash content of the products produced. At the same time, these indicators are influenced by a number of intermediate factors, for example, the height and looseness of the bed in the jig.
In addition, there are a number of parameters that characterize the technical condition technological equipment... For example, the temperature of the bearings of technological mechanisms; parameters of centralized liquid lubrication of bearings; condition of reloading nodes and elements of flow-transport systems; the presence of material on the conveyor belt; the presence of metal objects on the conveyor belt, the levels of material and slurry in containers; duration of work and downtime of technological mechanisms, etc.
A particular difficulty is caused by automatic on-line control of technological parameters that determine the characteristics of raw materials and processing products, such as ash content, material composition of ore, degree of opening of mineral grains, grain size and fractional composition of materials, degree of oxidation of the surface of grains, etc. These indicators are either controlled with insufficient accuracy or not controlled at all.
A large number of physical and chemical quantities that determine the modes of processing of raw materials are controlled with sufficient accuracy. These include the density and ionic composition of the pulp, volumetric and mass flow rates of technological streams, reagents, fuel, air; food levels in machines and apparatus, ambient temperature, pressure and vacuum in apparatus, food moisture, etc.
Thus, the variety of technological parameters, their importance in the management of enrichment processes require the development of reliably operating control systems, where the on-line measurement of physicochemical quantities is based on a variety of principles.
It should be noted that the reliability of the parameter control systems mainly determines the operability of the automatic process control systems.
Automatic control systems are the main source of information in production management, including in automated control systems and process control systems.
Sensors and Transducers
The main element of automatic control systems, which determines the reliability and performance of the entire system, is a sensor that is in direct contact with the controlled environment.
A sensor is an automation element that converts a monitored parameter into a signal suitable for entering it into a monitoring or control system.
A typical automatic control system generally includes a primary measuring transducer (sensor), a secondary transducer, an information (signal) transmission line and a recording device (Fig. 7.1). Often, the control system has only a sensitive element, a transducer, an information transmission line and a secondary (recording) device.
The sensor, as a rule, contains a sensitive element that senses the value of the measured parameter, and in some cases converts it into a signal convenient for remote transmission to a recording device, and, if necessary, to a control system.
An example of a sensing element would be the diaphragm of a differential pressure gauge that measures the pressure difference across an object. The movement of the diaphragm caused by the force from the pressure difference is converted by an additional element (transducer) into an electrical signal, which is easily transmitted to the recorder.
Another example of a sensor is a thermocouple, where the functions of a sensing element and a transducer are combined, since an electrical signal is generated at the cold ends of the thermocouple, which is proportional to the measured temperature.
More details about sensors of specific parameters will be described below.
Transducers are classified into homogeneous and non-homogeneous. The first have the same physical nature of the input and output values. For example, amplifiers, transformers, rectifiers - convert electrical quantities into electrical ones with other parameters.
Among the heterogeneous ones, the largest group is made up of converters of non-electrical quantities into electrical ones (thermocouples, thermistors, strain gauges, piezoelectric elements, etc.).
According to the type of output quantity, these converters are divided into two groups: generator ones, having an active electrical quantity at the output - EMF and parametric ones - with a passive output quantity in the form of R, L or C.
Displacement transducers. The most widespread are parametric transducers of mechanical movement. These include R (resistor), L (inductive) and C (capacitive) converters. These elements change in proportion to the input displacement the output value: electrical resistance R, inductance L and capacitance C (Fig. 7.2).
An inductive transducer can be made in the form of a coil with a mid-point tap and a plunger (core) moving inside.
The converters under consideration are usually connected to control systems using bridge circuits. A displacement transducer is connected to one of the bridge arms (Fig. 7.3 a). Then the output voltage (U out) taken from the tops bridge A-B, will change when the transformer work item is moved and can be evaluated by the expression:
The supply voltage of the bridge (U feed) can be constant (with Z i = R i) or alternating (with Z i = 1 / (Cω) or Z i = Lω) current with frequency ω.
Thermistors, strain and photoresistors can be connected to a bridge circuit with R elements, i.e. transducers whose output signal is a change in the active resistance R.
A widely used inductive converter is usually connected to an alternating current bridge circuit formed by a transformer (Fig. 7.3 b). The output voltage in this case is allocated on the resistor R included in the diagonal of the bridge.
A special group is made up of widely used induction converters - differential-transformer and ferro-dynamic (Fig. 7.4). These are generator converters.
The output signal (U out) of these converters is generated in the form of an alternating current voltage, which eliminates the need to use bridge circuits and additional converters.
The differential principle of the formation of the output signal in the transformer converter (Fig. 6.4 a) is based on the use of two secondary windings connected towards each other. Here, the output signal is the vector difference of the voltages arising in the secondary windings when the supply voltage U pit is applied, while the output voltage carries two information: the absolute value of the voltage - about the magnitude of the plunger movement, and the phase - the direction of its movement:
Ū out = Ū 1 - Ū 2 = kX in,
where k is the coefficient of proportionality;
X in - input signal (plunger movement).
The differential principle of the formation of the output signal doubles the sensitivity of the converter, since when the plunger is moved, for example, upward, the voltage in the upper winding (Ū 1) increases due to an increase in the transformation ratio, the voltage in the lower winding (Ū 2) decreases by the same amount ...
Differential transformer converters are widely used in control and regulation systems due to their reliability and simplicity. They are placed in primary and secondary instruments for measuring pressure, flow, levels, etc.
Ferrodynamic converters (PF) of angular displacements are more complex (Fig. 7.4 b and 7.5).
Here, in the air gap of the magnetic circuit (1), a cylindrical core (2) with a winding in the form of a frame is placed. The core is installed with cores and can be rotated through a small angle α in within ± 20 о. The excitation winding of the converter (w 1) is supplied AC voltage 12 - 60 V, resulting in a magnetic flux that crosses the area of the frame (5). A current is induced in its winding, the voltage of which (Ū out), other things being equal, is proportional to the angle of rotation of the frame (α in), and the voltage phase changes when the frame is turned to one side or the other from the neutral position (parallel to the magnetic flux).
The static characteristics of the PF converters are shown in Fig. 7.6.
Characteristic 1 has a converter without a bias winding (W cm). If the zero value of the output signal needs to be obtained not on average, but in one of the extreme positions of the frame, the bias winding should be connected in series with the frame.
In this case, the output signal is the sum of the voltages taken from the frame and the bias winding, which corresponds to the characteristic 2 or 2 ", if you change the connection of the bias winding to antiphase.
An important property of a ferrodynamic converter is the ability to change the slope of the characteristic. This is achieved by changing the size of the air gap (δ) between the stationary (3) and movable (4) plungers of the magnetic circuit, screwing in or unscrewing the latter.
The considered properties of PF converters are used in the construction of relatively complex control systems with the implementation of the simplest computational operations.
General industrial sensors of physical quantities.
The efficiency of enrichment processes largely depends on technological modes, which in turn are determined by the values of the parameters that affect these processes. The variety of enrichment processes determines a large number of technological parameters that require their control. To control some physical quantities, it is enough to have a standard sensor with a secondary device (for example, a thermocouple - an automatic potentiometer), for others additional devices and converters are required (density meters, flow meters, ash meters, etc.).
Among the large number of industrial sensors, one can single out sensors that are widely used in various industries as independent sources of information and as components of more complex sensors.
In this subsection, we will consider the most simple common industrial sensors of physical quantities.
Temperature sensors. Monitoring the thermal modes of operation of boilers, drying plants, some friction units of machines allows you to obtain important information necessary to control the operation of these objects.
Gauge thermometers... This device includes a sensing element (thermal balloon) and an indicating device connected by a capillary tube and filled with a working substance. The principle of operation is based on a change in the pressure of the working substance in a closed thermometer system depending on the temperature.
Depending on the state of aggregation of the working substance, liquid (mercury, xylene, alcohols), gas (nitrogen, helium) and steam (saturated vapor of a low-boiling liquid) manometric thermometers are distinguished.
The pressure of the working substance is fixed by a manometric element - a tubular spring, which unwinds when the pressure rises in a closed system.
Depending on the type of working substance of the thermometer, the temperature measurement range is from - 50 o to +1300 o C. The devices can be equipped with signal contacts, a recording device.
Thermistors (thermoresistances). The principle of operation is based on the property of metals or semiconductors ( thermistors) change its electrical resistance with a change in temperature. This dependence for thermistors has the form:
where R 0 – conductor resistance at T 0 = 293 0 K;
α Т - temperature coefficient of resistance
Sensitive metal elements are made in the form of wire coils or spirals, mainly of two metals - copper (for low temperatures - up to 180 ° C) and platinum (from -250 ° to 1300 ° C), placed in a metal protective casing.
To register the controlled temperature, the thermistor, as a primary sensor, is connected to an automatic AC bridge (secondary device), this issue will be discussed below.
Dynamically, thermistors can be represented by a first-order aperiodic link with a transfer function W (p) = k / (Tp + 1), if the time constant of the sensor ( T) is much less than the time constant of the object of regulation (control), it is permissible to take this element as a proportional link.
Thermocouples. To measure temperatures in large ranges and over 1000 ° C, thermoelectric thermometers (thermocouples) are usually used.
The principle of operation of thermocouples is based on the effect of DC EMF on the free (cold) ends of two dissimilar soldered conductors (hot junction), provided that the temperature of the cold ends differs from the junction temperature. The magnitude of the EMF is proportional to the difference between these temperatures, and the magnitude and range of measured temperatures depends on the material of the electrodes. The electrodes with porcelain beads strung on them are placed in protective fittings.
The thermocouples are connected to the recording device with special thermocouple wires. A millivoltmeter with a certain graduation or an automatic DC bridge (potentiometer) can be used as a recording device.
When calculating control systems, thermocouples can be represented, like thermistors, as a first-order aperiodic link or proportional.
The industry produces various types of thermocouples (Table 7.1).
Table 7.1 Characteristics of thermocouples
Pressure Sensors. Pressure (vacuum) and differential pressure sensors received the widest application in the mining and processing industry, both general industrial sensors and as components of more complex control systems for such parameters as slurry density, media flow rate, liquid media level, suspension viscosity, etc.
Gauge pressure measuring instruments are called manometers or pressure gauges, for measuring vacuum pressure (below atmospheric pressure, vacuum) - with vacuum gauges or traction gauges, for simultaneous measurement of excess and vacuum pressure - with manovacuum gauges or traction pressure gauges.
The most widely used sensors are spring type (deformation) with elastic sensitive elements in the form of a manometric spring (Fig. 7.7 a), a flexible membrane (Fig. 7.7 b) and a flexible bellows.
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To transmit readings to a recording device, a displacement transducer can be built into the manometers. The figure shows induction-transformer converters (2), the plungers of which are connected to the sensitive elements (1 and 2).
Instruments for measuring the difference between two pressures (differential) are called differential pressure gauges or differential pressure gauges (Fig. 7.8). Here, the pressure acts on the sensing element from both sides, these devices have two inlet connections for supplying higher (+ P) and lower (-P) pressures.
Differential pressure gauges can be divided into two main groups: liquid and spring. By the type of sensing element, the most common among spring ones are membrane (Fig. 7.8a), bellows (Fig. 7.8 b), among liquid ones - bell ones (Fig. 7.8 c).
The membrane block (Fig. 7.8 a) is usually filled with distilled water.
Bell differential pressure gauges, in which the sensitive element is a bell partially submerged upside down in transformer oil, are the most sensitive. They are used to measure small pressure drops in the range of 0 - 400 Pa, for example, to monitor the vacuum in the furnaces of drying and boiler plants.
The considered differential pressure gauges are scaleless; the controlled parameter is recorded by secondary devices, which receive an electrical signal from the corresponding displacement transducers.
Mechanical force sensors. These sensors include sensors containing an elastic element and a displacement transducer, strain gauge, piezoelectric and a number of others (Fig. 7.9).
The principle of operation of these sensors is clear from the figure. Note that a sensor with an elastic element can work with a secondary device - an AC compensator, a strain gauge sensor - with an AC bridge, piezometric - with a DC bridge. This issue will be discussed in more detail in subsequent sections.
A strain gauge sensor is a substrate on which several turns of a thin wire (special alloy) or metal foil are glued as shown in Fig. 7.9b. The sensor is glued to the sensitive element that perceives the load F, with the orientation of the long axis of the sensor along the line of action of the controlled force. This element can be any structure under the influence of the force F and operating within the elastic deformation. The strain gauge also undergoes the same deformation, while the sensor conductor is lengthened or shortened along the long axis of its installation. The latter leads to a change in its ohmic resistance according to the formula R = ρl / S known from electrical engineering.
We add here that the considered sensors can be used to control the performance of belt conveyors (Figure 7.10 a), measure the mass of vehicles (cars, railway cars, Figure 7.10 b), the mass of material in bunkers, etc.
Assessment of the conveyor performance is based on weighing a specific section of the belt loaded with material at a constant speed of its movement. The vertical movement of the weighing platform (2), mounted on elastic ties, caused by the mass of the material on the belt, is transmitted to the plunger of the induction-transformer converter (ITP), which generates information to the secondary device (U out).
For weighing railway cars, loaded vehicles, the weighing platform (4) is based on strain gauge blocks (5), which are metal supports with glued strain gauges, which experience elastic deformation depending on the weight of the weighing object.
The material of the topic of the lecture contains the content of the following questions: the structure of the process control system; purpose, goals and functions of the process control system; examples of information and control process control systems; main types of APCS; the composition of the APCS.
The structure of the process control system. See also the content of lectures 1, 2,3.
When building tools for modern industrial automation(usually in the form of an automated process control system) a hierarchical information structure is used with the use of computing facilities of various capacities at different levels. An approximate general modern structure of a process control system is shown in Figure 14.1:
IP - measuring transducers (sensors), IM - actuators, PLC-programmable logic controller, PLC - programmable (customizable) controller, INP - intelligent measuring transducers, InIM - intelligent actuators, Modem - signal modulator / demodulator, TO - hardware (hardware, "hardware"), IO - information support (databases), software - software, KO - communication support (serial port and software). PEP - user software, PEP - manufacturer's software, Ind - indicator.
Figure 14.1 - Typical functional diagram of a modern APCS.
At present, APCS are usually implemented according to the following schemes:
at the lower level, several PLCs with sensors and actuators connected to them,
at the top level - one (possibly several) operator (work) stations (automated workstations (AWP) of the operator).
1-level (local system) containing a PLC or a monoblock configurable controller (MNC) providing indication and signaling of the state of the monitored or regulated TP on the front panel,
2-tier (centralized system), including:
Usually a workstation or AWP is a computer in a special industrial design, with special software - a data collection and visualization system (SCADA systems).
APCS shown in figure 14.2
Figure 14.2 - Typical functional diagram of a single-level automatic control system of ACS.
The main functions of the elements:
reception of discrete signals from converters of technological equipment,
analog-to-digital conversion (ADC) of analog signals coming to inputs from converters,
scaling and digital filtering of data after the ADC,
processing of the received data according to the program of functioning,
generation (in accordance with the program) of discrete control signals and their supply to executive devices,
digital-to-analog conversion (DAC) of output information data into output analog signals,
supply of control signals to the corresponding actuators,
protection against loss of performance due to processor freezing using a watchdog timer,
preservation of performance in the event of a temporary power outage (due to an uninterruptible power supply with a battery of sufficient capacity),
monitoring the performance of the sensors and the reliability of the measured values,
indication of current and integral values of measured values,
control signaling of the state of the controlled process,
control light and symbol signaling of the controller state,
possibility of configuration (setting parameters) via a PC connected to a special port.
Converters (Pr):
conversion of the measured value (temperature, pressure, displacement, etc.) into a continuous or pulse (for PLC counting inputs) electrical signal.
Executive devices (IU):
conversion of control electrical continuous or pulse signals into mechanical movement of actuators, electronic control of current in power circuits, etc.
Matching device (if necessary):
galvanic or other types of isolation between PLCs and actuators (IU),
coordination of the permissible values of the output current of the PLC control channels and the current required for the normal operation of the DUT.
If the number of channels of one PLC is insufficient, a distributed I / O scheme is used using other (controlled, slave PLCs) or additional I / O controllers (modules).
A typical functional diagram of a single-levelAPCSwith distributed I / O shown in figure 14.3 :
Figure 14.3 - Typical functional diagram of a single-level APCS with distributed I / O
A typical functional diagram of a 2-level APCS is shown in Figure 14.4.
Figure 14.4 - Typical functional diagram of a 2-level APCS
All PLCs and workstations are united by an industrial information network that ensures continuous data exchange. Advantages: allows you to distribute tasks between the nodes of the system, increasing the reliability of its operation.
The main functions of the lower level:
collection, electrical filtering and ADC signals from converters (sensors);
implementation of local ACS of the technological process in the scope of the PLC functions of a single-level system;
implementation of emergency and warning signaling;
organization of a system of protection and blocking;
exchange of current data with a higher-level PC via an industrial network at the request of a PC.
Top-level main functions:
visualization of the state of the technological process;
current registration of technological process characteristics;
operational analysis of the condition of the equipment and technological process;
registration of operator's actions, including in case of emergency messages;
archiving and long-term storage of the values of the protocols of the technological process;
implementation of the "advisor system" algorithms;
supervisory management;
storage and maintenance of databases:
parameters of technical processes,
critical parameters of equipment,
signs of emergency conditions technological process,
the composition of operators allowed to work with the system (their passwords),
Thus, the lower level implements the algorithms management equipment, the upper one - the solution of strategic issues of operation. For example, the decision to turn on or off the pump is made at the upper level, and the supply of all necessary control signals, checking the status of the pump, the implementation of the blocking mechanism is performed at the lower level.
Hierarchical structure Process control system implies:
the flow of commands is directed from the top level to the bottom,
the lower one responds to the upper one according to its requests.
This ensures predictable behavior of the PLC in the event of a failure of the upper layer or the fieldbus, since such faults are perceived by the lower layer as the absence of new commands and requests.
When configuring the PLC, it is set: until what time after receiving the last request the PLC continues to operate, maintaining the last specified mode, after which it switches to the operating mode required for this emergency situation.
For example, the structure of the organization of the process control system of some concrete production at concrete mixing plants, according to the logic of construction, can be divided into two main levels:
the lower level - the level of the task implementation based on industrial controllers (PLC);
the upper level is the level of implementation of the task of visualizing the processes occurring during the production of concrete at a batching plant (SCADA).
At the lower level, the system solves the following main tasks:
collection of primary information from the executive units of the BSU;
analysis of the collected information;
working out the logic of the technological process in the production of concrete, taking into account all modern requirements;
issuance of control actions to executive devices.
At the top level, the system solves other tasks:
visualization of the main technological parameters from the batching plant (the state of the executive bodies, the current consumption of the mixer, the weight of the dosed materials, etc.);
archiving of all parameters of the concrete production process;
issuance of commands for the impact by the executive bodies of the BSU;
issuing commands to change the parameters of external influences;
development and storage of concrete mix recipes.
Appointment of the process control system. A The SUTP is designed to develop and implement control actions on the technological control object.
A technological control object (APCS) is a set of technological equipment and implemented on it in accordance with the relevant instructions or regulations of the technological process for the production of products, intermediate products, products or energy,
Technological control objects include:
technological units and installations (groups of machines) that implement an independent technological process;
separate production (workshops, sections), if the management of this production is mainly technological in nature, that is, it consists in the implementation of rational modes of operation of interconnected technological equipment (units, sections).
Jointly functioning TOU and the APCS control them form an automated technological complex (ATC). In mechanical engineering and other discrete industries, flexible manufacturing systems (FPS) act as ATC.
The terms APCS, TOU and ATK should be used only in the given combinations. The totality of other control systems with their control of technological equipment is not an ATC. The control system in other cases (not in the ATC) is not a process control system, etc. An automated process control system is an organizational and technical system for managing an object as a whole in accordance with the adopted control criterion (criteria), in which the collection and processing of the necessary information is carried out using computer technology.
The above wording emphasizes:
firstly, the use of modern computer technology in the process control system;
secondly, the role of a person in the system as a subject of labor, taking meaningful participation in the development of management decisions;
thirdly, that an automated process control system is a system that processes technological and technical and economic information;
fourthly, that the purpose of the functioning of the process control system is to optimize the operation of the technological object of control in accordance with the accepted criterion (criteria) of control by the appropriate choice of control actions.
Control criterion in the process control system, this is a ratio that characterizes the degree of achievement of control objectives (the quality of functioning of the technological control object as a whole) and takes various numerical values depending on the control actions used. It follows that the criterion is usually a technical and economic criterion (for example, the cost of the output product at a given quality, the performance of the TOU at a given quality of the output product, etc.) or a technical indicator (process parameter, characteristics of the output product).
In the event that the TOU is controlled by the APCS, all the operational personnel of the TOU participating in management and all the controls provided for by the documentation for the APCS and interacting during the management of the TOU are part of the system, regardless of which way (new construction or modernization of the control system) was created ATK.
The process control system is created by capital construction, because Regardless of the scope of delivery, for its commissioning, it is necessary to carry out construction, installation and commissioning work at the facility.
Process control system as a component common system management of an industrial enterprise is intended for the purposeful management of technological processes and the provision of adjacent and higher management systems of operational and reliable technical and economic information. The process control systems created for the objects of the main and (or) auxiliary production represent the lower level of automated control systems at the enterprise.
APCS can be used to manage individual industries that include interconnected TOUs, including those controlled by their own low-level APCS.
For objects with a discrete nature of production, flexible production systems can include automated systems for technological preparation of production (or their corresponding subsystems) and computer-aided design technology (CAD technology).
The organization of the interaction of the APCS with the higher levels of management is determined by the presence of an automated enterprise management system (APCS) and automated operational dispatch control systems (ASODU) at an industrial enterprise.
If they are available, the process control system together with them form an integrated automated control system (IACS). In this case, the APCS receives tasks and restrictions from the corresponding subsystems of the APCS or enterprise management services directly or through the OSODU (the range of products or products to be produced, the volume of production, technical and economic indicators, characterize the quality of the ATC functioning, information on the availability of resources) and provides training and transferring to these systems the technical and economic information necessary for their operation, in particular about the results of the ATC operation, the main indicators of the products, the operational demand for resources, the state of the ATC (the state of the equipment, the course of the technological process, its technical and economic indicators, etc.) ,
If the enterprise has automated systems for technical and technological preparation of production, the necessary interaction of the process control system with these systems should be provided. At the same time, the APCS will receive from them the technical, technological and other information necessary to ensure the specified performance of technological processes, and send the actual operational information necessary for their functioning to the named systems.
When creating an integrated product quality management system at an enterprise, automated process control systems act as its executive subsystems that ensure the specified quality of TOU products and the preparation of operational factual information about the progress of technological processes (statistical control, etc.)
Goals and functions of the process control system. When creating an automated process control system, the specific goals of the functioning of the system and its purpose in the general management structure of the enterprise must be determined.
Examples of such goals can serve:
saving fuel, raw materials, materials and other production resources;
ensuring the safety of the operation of the facility;
improving the quality of the output product or ensuring the specified values of the parameters of the output products (product);
reducing the cost of human labor;
achievement of optimal loading (use) of equipment;
optimization of operating modes of technological equipment (including processing routes in discrete industries), etc.
The achievement of the set goals is carried out by the system through the implementation of the totality of its functions.
The APCS function is a set of system actions that ensure the achievement of a particular control goal.
In this case, the set of actions of the system is understood as the sequence of operations and procedures described in the operational documentation, performed by the elements of the system for its implementation.
The particular goal of the functioning of the process control system is the goal of functioning or the result of its decomposition, for which it is possible to determine the complete set of actions of the system elements, sufficient to achieve this goal.
The functions of the process control system according to the direction of action (purpose of the function) are divided into main and auxiliary, and according to the content of these actions - on managing and informational.
TO the main(consumer) functions of the process control system include functions aimed at achieving the goals of the system functioning, carrying out control actions on the TOU and (or) the exchange of information with adjacent control systems. Usually, they also include information functions that provide the operating personnel of the ATK with the information they need to control the technological process of production.
TO subsidiary the functions of the process control system include functions aimed at achieving the required quality of functioning (reliability, accuracy, etc.) of the system, implementing control and management of its work.
TO manager the functions of the process control system include functions, the content of each of which is the development and implementation of control actions on the corresponding control object - TOU or part of it for the main functions and on the control system or part of it for the auxiliary ones. For example:
basic management functions;
regulation (stabilization) of individual technological variables;
single-cycle logical control of operations or devices (protection);
programmed logical control of technological devices;
optimal control of TOU;
adaptive control of TOU, etc .;
auxiliary control functions;
reconfiguration of the computer complex (network) of the process control system;
emergency shutdown of APCS equipment;
switching technical means Process control system for emergency power supply, etc.
TO information The functions of the APCS include functions, the content of each of which is to receive and transform information about the state of the TOU or APCS and its presentation to adjacent systems or to the operational personnel of the ATC. For example, the main information functions:
control and measurement of technological parameters;
indirect measurement of process parameters (internal variables, technical and economic indicators);
preparation and transmission of information to snow control systems, etc .;
auxiliary information functions:
control of the state of the control system equipment;
determination of indicators characterizing the quality of functioning of the process control system or its parts (in particular, the operating personnel of the process control system), etc.
The main types of APCS Distinguishes between two modes of implementation of system functions: automated and auto- depending on the degree of participation of people in the performance of these functions. For the controlling functions, the automated mode is characterized by human participation in the development (adoption) of decisions and their implementation. In this case, the following options are distinguished:
mode indirect control when computer facilities change the settings and (or) settings of local automatic control (regulation) systems ( supervisory or cascade control);
mode direct(direct) digital control ( NCU) when the control computing device directly affects the actuators.
« manual»A mode in which a set of technical means provides operational personnel with control and measuring information about the state of the TOU, and the choice and implementation of control actions remotely or locally is made by a human operator;
mode " advisor», In which a complex of technical means develops recommendations for management, and the decision on their use is implemented by operational personnel;
« dialogue mode»When the operating personnel has the opportunity to correct the formulation and conditions of the problem solved by the complex of technical means of the system when developing recommendations for managing the object;
« auto mode", In which the control function is carried out automatically (without human intervention). At the same time, a distinction is made between:
On the day of information functions, the automated implementation mode provides for the participation of people in operations to receive and process information. In automatic mode, all the necessary information processing procedures are implemented without human participation.
Let us consider in more detail the control schemes in the process control system.
Control in data acquisition mode. After the identification stage, it is necessary to choose a TP control scheme, which, as a rule, is built taking into account the application of control principles that determine the mode of operation of the APCS. The simplest and historically the first was the TP control scheme in data collection mode... In this case, the ACS is connected to the process in the manner selected by the process engineer (Figure 14.5).
The variables of interest to the process engineer are converted into digital form, perceived by the input system and placed in memory PPK (computer)... The values at this stage are digital representations of the voltage generated by the sensors. These values are converted into engineering units according to the appropriate formulas. For example, to calculate the temperature measured with a thermocouple, the formula T = A * U 2 + B * U + C can be used, where U is the voltage from the output of the thermocouple; A, B and C are coefficients. The calculation results are recorded by the output devices of the process control system for subsequent use by the process engineer. The main purpose of data collection is to study TA in different conditions. As a result, the process engineer gets the opportunity to build and (or) refine the mathematical model of the TP, which needs to be controlled. Data collection does not have a direct impact on the TP, it found a cautious approach to the implementation of management methods based on the use of computers. However, even in the most complex TP control schemes, the data collection system for the purposes of analysis and refinement of the TP model is used as one of the mandatory control subcircuits.
Figure 14.5 - Data collection system
Operator advisor control. This mode assumes that the ACS as part of the APCS operates in the rhythm of the TP in an open loop (in real time), i.e. the outputs of the process control system are not associated with the TP management bodies. Control actions are actually carried out by the operator-technologist, receiving instructions from the control panel (Figure 14.6).
Figure 14.6 - Process control system in operator advisor mode
All necessary control actions are calculated by the PPC in accordance with the TP model, the calculation results are presented to the operator in printed form (or in the form of messages on the display). The operator controls the process by changing the setpoints of the regulators. Regulators are the means of maintaining optimal control of TP, and the operator plays the role of a follower and control link. The process control system plays the role of a device that guides the operator unmistakably and continuously in his efforts to optimize the process.
The scheme of the advisor system coincides with the scheme of the information collection and processing system. The ways of organizing the functioning of the information-advising system are as follows:
the calculation of control actions is performed when the parameters of the controlled process deviate from the specified technological modes, which are initiated by the dispatcher program containing a subroutine for analyzing the state of the controlled process;
the calculation of control actions is initiated by the operator in the form of a request, when the operator has the opportunity to enter additional data necessary for the calculation, which cannot be obtained by measuring the parameters of the controlled process or contained in the system as reference.
These systems are used when a careful approach to formal decisions is required. This is due to the uncertainty in the mathematical description of the controlled process:
the mathematical model does not fully describe the technological (production) process, since it takes into account only a part of the control and controlled parameters;
the mathematical model is adequate to the controlled process only in a narrow range of technological parameters;
management criteria are qualitative in nature and vary significantly depending on a large number of external factors.
The uncertainty of the description may be due to insufficient knowledge of the technological process or the implementation of an adequate model will require the use of an expensive PPC.
With a large variety and amount of additional data, the operator's communication with the control panel is built in the form of a dialogue. For example, alternative points are included in the algorithm for calculating the technological mode, after which the calculation process can continue according to one of several alternative options. If the logic of the algorithm leads the calculation process to a certain point, then the calculation is interrupted and the operator is sent a request for additional information, on the basis of which one of the alternative ways of continuing the calculation is selected. PPK plays in this case a passive role associated with the processing of a large amount of information and its presentation in a compact form, and the decision-making function is assigned to the operator.
The main disadvantage of this control scheme is the constant presence of a person in the control circuit. With a large number of input and output variables, such a control scheme cannot be applied due to the limited psychophysical capabilities of a person. However, this type of control also has advantages. It satisfies the requirements for a prudent approach to new management methods. The advisor mode provides good opportunities to test new TP models; the operator can be a process engineer who has a "fine feeling" for the process. He will surely find an incorrect combination of settings, which may be produced by an incompletely debugged process control program. In addition, the APCS can monitor the occurrence of emergencies, so that the operator can pay more attention to working with the settings, while the APCS monitors a greater number of emergencies than the operator.
Supervisory management. In this scheme, the process control system is used in a closed loop, i.e. the settings for the regulators are set directly by the system (Figure 14.7).
Figure 14.7 - Supervisory control scheme
The task of the supervisory control mode is to maintain the TP near the optimal operating point by means of operational impact on it. This is one of the main advantages of this mode. The operation of the input part of the system and the calculation of control actions differ little from the operation of the control system in the advisor mode. However, after the calculated values of the setpoints, the latter are converted into values that can be used to change the settings of the regulators.
If the regulators perceive voltages, then the values generated by the computer must be converted into binary codes, which, using a digital-to-analog converter, are converted into voltages of the corresponding level and sign. Optimization of TP in this mode is performed periodically, for example. once a day. New coefficients have to be introduced into the control loop equations. This is done by the operator through the keyboard, or by reading the results of new calculations performed on a computer of a higher level. After that, the process control system is able to work without outside interference for a long time. Examples of process control systems in supervisory mode.
Management of the automated transport and storage system. The computer issues the addresses of the rack cells, and the local automation system of stacker cranes works out their movement in accordance with these addresses.
Melting furnace control. The computer generates the values of the settings for the electric mode, and the local automation controls the switches of the transformer according to the commands of the computer.
CNC machines controlled by interpolator.
Thus, supervisory control systems operating in the supervisory control mode ( supervisor- a control program or a complex of programs, a dispatcher program), is intended for organizing a multi-program mode of operation of the PPK and is a two-level hierarchical system with wide capabilities and increased reliability. The control program determines the order of execution of programs and subroutines and manages the loading of the control panel devices.
In a supervisory control system, part of the parameters of the controlled process and logic-command control are controlled by local automatic controllers (AR) and PPK, processing the measurement information, calculates and sets the optimal settings of these controllers. The rest of the parameters are controlled by the control panel in the direct digital control mode. The input information is the values of some controlled parameters measured by the DN sensors of the local regulators; monitored parameters of the state of the controlled process, measured by the sensors DK. The lower level, directly related to the technological process, forms local regulators of individual technological parameters. According to the data received from the Dy and Dk sensors through a device for communicating with the object, the PPC generates setpoint values in the form of signals that go directly to the inputs of the automatic control systems.
Direct digital control. At the NCU, the signals used to actuate the control bodies come directly from the process control system, and the regulators are generally excluded from the system. The concept of NCU, if necessary, allows you to replace the standard laws of regulation with the so-called. optimal with a given structure and algorithm. For example, an algorithm for optimal performance can be implemented, etc.
The process control system calculates the real impacts and transmits the corresponding signals directly to the control bodies. The NCU diagram is shown in Figure 14.8.
Figure 14.8 - Diagram of direct digital control (NCU)
The settings are entered into the ACS by an operator or a computer that performs calculations to optimize the process. In the presence of an NCU system, the operator must be able to change the setpoints, control some selected variables, vary the ranges of permissible change of the measured variables, change the settings, and generally must have access to the control program.
One of the main advantages of the NCU mode is the ability to change control algorithms for loops by simply making changes to the stored program. The most obvious disadvantage of the NTSU manifests itself in the event of a computer failure.
Thus, the systems direct digital control(NCU) or direct digital control (NCU, DDC). The PPC directly generates optimal control actions and, with the help of appropriate converters, transmits control commands to the actuators. Direct digital control mode allows:
exclude local regulators with a configurable setpoint;
apply more effective principles of regulation and management and choose their best option;
implement optimizing functions and adapt to change external environment and variable parameters of the control object;
reduce costs for Maintenance and unify controls and controls.
This control principle is used in CNC machines. The operator must be able to change the setpoints, control the output parameters of the process, vary the ranges of permissible change of variables, change the settings, have access to the control program in such systems, it is easier to implement the modes of starting and stopping processes, switching from manual control to automatic, switching operations of actuators. The main disadvantage of such systems is that the reliability of the entire complex is determined by the reliability of communication devices with the object and the control panel, and in case of failure, the object loses control, which leads to an accident. A way out of this situation is the organization of computer redundancy, the replacement of one computer with a system of machines, etc.
The composition of the APCS. The performance of the functions of the process control system is achieved through the interaction of its following components:
technical support (TO),
software (software),
information support (IO),
organizational support (OO),
operational personnel (OP).
These five components and form the composition of the process control system. Sometimes other types of software are considered, for example, linguistic, mathematical, algorithmic, but they are considered as software components, etc.
Technical support APCS is a complete set of technical means (including computer equipment), sufficient for the operation of the APCS and for the system to perform all its functions. Note. Regulatory bodies are not part of the TO APCS.
The complex of the selected technical means should provide such a system of measurements in the conditions of functioning of the APCS, which, in turn, provide the necessary accuracy, speed, sensitivity and reliability in accordance with the specified metrological, operational and economic characteristics. Technical means can be grouped according to operational characteristics, control functions, information characteristics, structural similarity. The most convenient is the classification of technical means according to information characteristics. In connection with the above, the complex of technical means must contain:
means for obtaining information about the state of the control object and means for entering into the system (input converters, sensors), providing transformation input information to standard signals and codes;
means for intermediate information conversion, providing interconnection between devices with different signals;
output converters, means of information output and control, converting machine information into various forms necessary for controlling the technological process;
means of formation and transmission of information, ensuring the movement of information in space;
means of fixing information, ensuring the movement of information in time;
information processing facilities;
means of local regulation and control;
computer facilities;
means of presenting information to operational personnel;
executive devices;
means of transferring information to adjacent ACS and ACS of other levels;
devices, devices for adjusting and checking the system performance;
documentation technology, including the means of creating and destroying documents;
office and archival equipment;
auxiliary equipment;
materials and tools.
Auxiliary technical means ensure the implementation of secondary management processes: copying, printing, processing correspondence, creating conditions for the normal work of management personnel, maintaining technical means in good condition and their functioning. The creation of standard APCS is currently impossible due to a significant discrepancy in the organizational systems of enterprise management.
The technical means of the automated process control system must comply with the requirements of GOSTs, which are aimed at ensuring various compatibility of the automation object. These requirements are subdivided into groups.
Information... Provide informational compatibility of technical means with each other and with service personnel.
Organizational... Process control structure, control technology, technical means must correspond to each other before and after the implementation of the APCS, for which it is necessary to ensure:
Compliance of the structures of the CTS - the structure of the object management;
Automated execution of basic functions, information extraction, transmission, processing, data output;
the possibility of modifying the KTS;
the possibility of creating organizational systems for monitoring the work of the CCC;
the possibility of creating personnel control systems.
3. Mathematical. Smoothing of inconsistencies in the work of technical means with information can be performed using programs for transcoding, translation, and reshaping of layouts. This leads to the following requirements for the software:
quick solution of the main tasks of the APCS;
simplification of communication between the staff and the CCC;
the possibility of informational docking of various technical means.
4. Technical requirements:
the required performance for the timely solution of the tasks of the automated process control system;
adaptability to the conditions of the external environment of the enterprise;
reliability and maintainability;
the use of unified, commercially available blocks;
ease of operation and maintenance;
technical compatibility of funds based on a common element and design base;
requirements of ergonomics, technical aesthetics.
5. Economic requirements for technical means:
minimum capital investment for the creation of a CTS;
minimum production areas for the placement of CTS;
minimum costs for auxiliary equipment.
6. Reliability APCS. When considering the technical support, the issue of the reliability of the APCS is also considered. In this case, it is necessary to conduct a study of the APCS, highlighting the following points:
complexity (a large number of different technical means and personnel);
multifunctionality;
multidirectional use of elements in the system;
multiplicity of failure modes ( causes of occurrence, effects);
the relationship between reliability and economic efficiency;
dependence of reliability on technical operation;
dependence of reliability on CTS and the structure of algorithms;
8) the impact of personnel on reliability.
The level of operational reliability of the APCS is determined by such factors as:
the composition and structure of the technical means used;
modes, parameters of maintenance and recovery;
operating conditions of the system and its individual components;
Software APCS is a set of programs and operational software documentation required to implement the functions of an automated control system technological process the specified mode of functioning of the complex of technical means of the process control system.
APCS software is subdivided into general software (OPO) and special software (SPO).
TO common The software of the process control system includes that part of the software that is supplied complete with computer equipment or purchased ready-made in specialized funds of algorithms and programs. The OPO APCS includes programs used for developing programs, assembling software, organizing the functioning of a computing complex, and other utility and standard programs (for example, organizing programs, translating programs, libraries of standard programs, etc.). OPO APCS is manufactured and supplied in the form of products for industrial and technical purposes by manufacturers of BT equipment (see clause 1.4.7).
TO special APCS software includes that part of the software that is developed when creating a specific system (systems) and includes programs for the implementation of the main (control and information) and auxiliary (ensuring the specified functioning of the CTS system, checking the correctness of information input, monitoring the operation of the CTS system, etc.) of the functions of the process control system. Special software for the process control system is developed on the basis of and using software. Individual programs or open source software for the process control system as a whole can be manufactured and delivered in the form of software as products for industrial and technical purposes.
The software includes general software supplied with computer facilities, including organizing programs, dispatcher programs, translating programs, operating systems, libraries of standard programs, as well as special software that implements the functions of a specific system, ensures the functioning KTS, including hardware.
Mathematical, algorithmic support. As you know, a model is an image of an object of research, reflecting the essential properties, characteristics, parameters, interconnections of an object. One of the methods for studying processes or phenomena in an automated process control system is the method of mathematical modeling, i.e. by building their mathematical models and analyzing these models. A kind of mathematical modeling is simulation, which uses direct substitution of numbers that simulate external influences, parameters and process variables using the UVC. To carry out simulation studies, it is necessary to develop an algorithm. The algorithms used in APCS are characterized by the following features:
temporary connection of the algorithm with the controlled process;
storage of working programs in the operating memory of the UVK for access to them at any time;
excess of the proportion of logical operations;
division of algorithms into functional parts;
implementation of time-sharing algorithms at UVK.
Taking into account the time factor in control algorithms comes down to the need to fix the time of receiving information into the system, the time of issuing messages by the operator to form control actions, and predicting the state of the control object. It is necessary to ensure the timely processing of signals from the UVC associated with the controlled object. This is achieved by compiling the most efficient algorithms in terms of speed, implemented on high-speed UVK.
The second feature of the APCS algorithms implies stringent requirements for the amount of memory required for the implementation of the algorithm, for the coherence of the algorithm.
The third feature of the algorithms is due to the fact that technological processes are controlled on the basis of decisions made based on the results of comparing various events, comparing the values of object parameters, checking the fulfillment of various conditions and restrictions.
The use of the fourth feature of the ACS TP algorithms allows the developer to formulate several system tasks, and then combine the developed algorithms for these tasks into a single system. The degree of interconnection between the tasks of the APCS can be different and depends on the specific control object.
To take into account the fifth feature of control algorithms, it is necessary to develop real-time operating systems and plan the sequence of loading modules that implement the algorithms of the tasks of the automated process control system, their execution depending on the priorities.
At the stage of development of the automated process control system, measuring information systems are created, which provide complete and timely control of the operating mode of the units, allowing you to analyze the progress of the technological process and accelerate the solution of optimal control problems. The functions of centralized control systems are reduced to solving the following tasks:
determination of current and predicted values of quantities;
determination of indicators depending on a number of measured values;
detection of events that are violations and malfunctions in production.
The general model of the problem in assessing the current values of the measured quantities and the TPE calculated from them in the centralized control system can be represented as follows: a set of quantities and indicators that must be determined in the control object is set, the required accuracy of their assessment is indicated, there is a set of sensors that are installed on automated object. Then the general problem of evaluating the value of an individual quantity is formulated as follows: for each individual quantity, it is required to find a group of sensors, the frequency of their polling and an algorithm for processing the signals received from them, as a result of which the value of this quantity is determined with a given accuracy.
Mathematical methods such as linear programming, dynamic programming, optimization methods, convex programming, combinatorial programming, and nonlinear programming are used to solve problems in an automated process control system. Methods for constructing a mathematical description of an object are the Monte Carlo method, mathematical statistics, experiment planning theory, queuing theory, graph theory, systems of algebraic and differential equations.
Information Support APCS includes: a list and characteristics of signals that characterize the state of the ATC:
Description of the principles (rules) of classification and coding of information and a list of classification groupings,
descriptions of arrays of information, forms of documents for video frames used in the system,
normative reference (conditionally constant) information used during the operation of the system.
Part organizational support APCS includes a description of the APCS (functional, technical and organizational structure of the system) and instructions for operating personnel, necessary and sufficient for its functioning as part of the ATC.
Organizational support includes a description of the functional, technical, organizational structures of the system, instructions and regulations for operating personnel on the work of the APCS. It contains a set of rules and regulations that ensure the required interaction of operational personnel with each other and with a set of tools.
Thus, the organizational structure of management is the relationship between the people involved in the operation of the facility. The personnel engaged in operational management maintains the technological process within the specified norms, ensures the fulfillment of the production plan, controls the operation of technological equipment, and monitors the conditions for the safe conduct of the process.
The operating personnel of the APCS ensures the correct functioning of the CCS of the APCS, keeps records and reports. The APCS receives from the higher level of management production tasks, the criteria for the implementation of these tasks, transfers to higher levels of management information about the performance of tasks, quantitative and qualitative indicators of products and the functioning of the automated technological complex.
For analysis organizational structure and determining the optimal construction of internal relationships using methods of group dynamics. In this case, the methods and techniques of social psychology are usually used. The studies carried out made it possible to formulate the requirements necessary for organizing a group of operational technological personnel:
all production information should be transmitted only through the manager;
one subordinate should have no more than one immediate supervisor;
in the production cycle, only subordinates of one manager interact with each other informationally.
Maintenance departments perform work at all stages of creating an automated process control system (design, implementation, operation), their main functions are:
Ensuring the operation of systems in accordance with the rules and requirements of technical documentation;
provision of current and planned repairs of technical means of APCS;
conducting, together with the developers, testing of the automated process control system;
conducting research to determine the economic efficiency of the system;
development and implementation of measures for the further development of the system;
Advanced training of the employees of the APCS service, study and generalization of operating experience. To perform the functions, the technologist-operator must be presented with technical and software
means providing, depending on the characteristics of the technological process, the required sets of the following information messages:
indication of measured values of parameters on call;
indication and change of the set limits of the process parameters control;
sound signaling and indication of deviations of parameters beyond the regulatory limits;
sound signaling and indication of deviations of the rate of change of parameters from the set values;
displaying the state of the technological process and equipment on the control object diagram;
registration of tendencies of change of parameters;
operational registration of violations of the technological process and operator actions.
Information Support(AND ABOUT) includes a system for coding technological and technical and economic information, reference and operational information, contains a description of all signals and codes used to communicate technical means. The codes used must include a minimum number of characters, have a logical structure and meet other coding requirements. The forms of the output documents and information representations should not cause difficulties in their use.
When developing and implementing a system of IO APCS, it is necessary to take into account the principles of organizing the process control, which correspond to the following stages.
Determination of APCS subsystems and types of management decisions for which it is necessary to provide scientific and technical information. The results of this stage are used to determine the optimal structure of information arrays, to identify the characteristics of the expected flow of requests.
Determination of the main groups of information consumers. Consumers of information are classified according to their participation in the preparation and adoption management decisions associated with the organization of the technological process. The accumulation of information is carried out taking into account types of tasks solved in process control. The consumer can get information on the associated technological areas, and conditions are created for the redistribution of information when needs change.
Study of information needs.
Study of streams of scientific and technical information required for process management, is based on the results of the analysis of management tasks. Along with the streams of documentary information, facts reflecting the experience of this and similar enterprises are analyzed.
Development of information retrieval systems for process control.
Automated systems are characterized by information processing processes - transformation, transmission, storage, perception. When controlling a technological process, information is transmitted and the control system processes input information into output information. At the same time, control and regulation are necessary, consisting in comparing information about the results of the previous stage of activity with information corresponding to the conditions for achieving the goal, in assessing the mismatch between them and developing a correcting output signal. The mismatch is caused by internal and external disturbing influences of a random nature. The process of transmitting information assumes the presence of a source of information and a receiver.
To ensure human participation in the control of the technological process, it is necessary to document the information. Subsequent analyzes require the accumulation of statistical raw data by recording the states and values of the process parameters over time. On the basis of this, compliance with the technological process, product quality is checked, the actions of personnel in emergency situations are monitored, and the search for ways to improve the process is carried out.
When developing information support for APCS related to documentation and registration, it is necessary:
determine the type of registered parameters, place and form of registration;
choose the time factor of registration;
to minimize the number of registered parameters for reasons of necessity and sufficiency for operational actions and analysis;
unify document formats, their structure;
enter special details;
resolve issues of classification of documents and routes of their movement;
determine the amount of information in documents, establish the place and terms of storage of documents.
The system must transmit information flows in the communication channels of the APCS with the required quality of information from the place of its formation to the place of its reception and use. To do this, the following requirements must be met:
timeliness of information delivery;
fidelity of transmission - no distortion, loss;
reliability of functioning;
unity of time in the system;
the possibility of technical implementation;
ensuring the economic acceptability of information requirements. In addition, the system should provide for:
regulation of information flows;
the possibility of carrying out external relations;
the possibility of expanding the APCS;
convenience of human participation in the analysis and control of the process.
The main characteristics of information flow include:
control object (source of information);
the purpose of the information;
information format;
volumetric flow characteristics;
frequency of occurrence of information;
an object using information.
If necessary, the flow characteristics are detailed by specifying:
type of information;
the name of the controlled parameter;
the range of variation of the parameter in time;
the number of parameters of the same name at the object;
conditions for displaying information;
speed of information generation.
The main information characteristics of the communication channel include:
the location of the beginning and end of the communication channel;
the form of the transmitted information;
transmission channel structure - sensor, encoder, modulator, communication line, demodulator, decoder, display device;
communication channel type - telephone, mechanical;
transmission speed and volume of information;
ways of transforming information;
channel bandwidth;
signal volume and capacity of the communication channel;
noise immunity;
information and hardware redundancy of the channel;
reliability of communication and transmission over the channel;
signal attenuation level in the channel;
informational coordination of the links of the channel;
transmission channel mobility.
A time indication of information can be added to the APCS, which assumes a unified time system with a centralized reference scale. A characteristic feature of the information links of the APCS is the action in real time. The use of a unified time reference system ensures the following tasks:
documenting the time of reception, transmission of information;
logging of events occurring in the APCS;
analysis of production situations by time (order of receipt, duration);
accounting of the time of information passage through communication channels and the time of information processing;
management of the sequence of reception, transmission, processing of information;
setting a sequence of control actions within a single time scale;
display of a single time within the area of operation of the APCS.
When creating an automated process control system, the main attention is paid to signals associated with the interaction of individual elements. Signals of human interaction with technical means and of some technical means with other technical means are subject to study. In this regard, the following groups of signals and codes are considered:
The first group is stylized languages that provide economical input of data into technical means and their output to the operator. By the nature of the information, technical and economic data are distinguished.
The second group solves the problems of data transmission and docking of technical means. Here, the main problem is the fidelity of the message transmission, for which error-correcting codes are used. Information compatibility of technical means is ensured by installing additional matching equipment, using auxiliary data transcoding programs.
The third group is machine languages. Usually, binary codes are used with data security elements on a digital module, with the addition of a check digit.
General technical requirements for automated process control systems for information support:
maximum simplification of information coding due to code designations and repetition codes;
ensuring ease of decoding of output documents and forms;
3) information compatibility of APCS with adjacent systems in terms of content, coding, and form of information presentation;
4) the possibility of making changes to previously transmitted information;
5) ensuring the reliability of the system's performance of its functions due to the noise immunity of information.
The APCS personnel interacts with the CCC, perceiving and entering technological and economic information. In addition, the operator interacts with other operators and higher-level personnel. To facilitate these links, measures are being taken to formalize information flows, compress and streamline them. The computer transmits information to the operator in the form of light signals, images, printed documents, sound signals.
When the operator interacts with the UVK, it is necessary to ensure:
Visual display of the functional and technological diagram of the control object, information about its state in the scope of functions assigned to the operator;
display of the connection and the nature of the interaction of the control object with the external environment;
signaling about violations in the operation of the facility;
Quick identification and elimination of faults.
Separate groups of elements, the most essential for the control and management of an object, are usually distinguished by size, shape, and color. The technical means used for the automation of control allow information to be entered only in a certain predetermined form. This leads to the need to encode information. The exchange of data between the functional blocks of the control system should be carried out with complete semantic messages. Messages are transmitted in two separate data streams: information and control.
Information flow signals are divided into groups:
service.
measured parameter;
measuring range;
states of functional blocks of the system;
addresses (belonging of the measured parameter to a certain block);
To protect against errors in the exchange of information through communication channels at the input and output of the equipment, redundant codes should be used with their parity, cyclicity, iteration, repeatability. Information security issues are related to ensuring the reliability of the control system, the forms of information presentation. The information must be protected from distortion and from misuse. Information protection methods depend on the operations performed, on the equipment used
Operational staff The APCS consists of ATC operator technologists who control the operation and control of the TOU using information and recommendations for rational management developed by the APCS automation systems, and the APCS operating personnel, ensuring the correct functioning of the APCS hardware and software complex. Maintenance personnel are not included in the operational personnel of the process control system.
During the process of designing the process control system, mathematical and linguistic support is developed, which are not explicitly included in the functioning system. The software for the process control system is a set of methods, models and algorithms used in the system. The software for the process control system is implemented in the form of special software programs. The linguistic support of the process control system is a combination of linguistic means for communication of the operating personnel of the process control system with the means of the VT system. The description of the language means is included in the operational documentation of the organizational and software of the system. Metrological support of an automated process control system is a set of works, design solutions and hardware and software aimed at ensuring the specified accuracy characteristics of the system functions, implemented on the basis of measurement information.
The operating personnel include technologists-operators of the automated technological complex, who control the technological object, and the operating personnel of the automated process control system, which ensures the functioning of the system. Operational personnel can work in and out of the control loop. In the first case, the management functions are implemented according to the recommendations issued by the CCC. In the second case, the operating personnel sets the operating mode for the system, controls the operation of the system and, if necessary, takes over the management of the technological object. Repair services are not part of the process control system.
The dispatching service in the automated process control system is located at the junction of technological process control and production management. Operator and dispatch centers of the automated control system provide an economical combination of the capabilities of the operating personnel and the capabilities of the technical means.
In the organizational structures of the operational management of the enterprise, the following types of operational management points have become widespread:
Local control posts. The control is carried out by separate mechanisms and units, serviced by foremen, teams, apparatchiks or linemen.
Operator stations are the lower stage of the system for collecting, transmitting technological information and managing the facility; they are organized in sections, departments, workshops. Here, the tasks of maintaining a given technological regime, optimizing the technological process, ensuring the rhythm of equipment operation, eliminating deviations in the production process, preventing and eliminating emergency conditions are solved. Information to the operator's stations comes from sensors or from local control posts and is reproduced in full. The operator's station also receives planned, normative, directive information from higher levels of management. Operators perform the following functions:
control of the technological process and equipment at the site;
maintaining a given technological regime;
ensuring the fulfillment of a shift task;
ensuring the rhythm of the equipment;
elimination of process deviations, prevention of accidents;
control of the availability of stocks of raw materials and materials;
fulfillment of orders of the superior dispatcher;
control over the work of linemen.
3. Dispatching points. At the control points, production and statistical information is collected, which is necessary to determine the TP of the process, the possibility of its optimization depending on the quality of raw materials, reserves, resources, and the tasks of operational control, accounting, technical and economic analysis, management on a scale of sites, shop are also solved. The main task of management at this stage is the distribution and coordination of material and energy flows to obtain maximum production efficiency. The functions of the shift dispatchers of the workshop are:
1) ensuring the implementation of shift tasks;
2) operational control of the technological process in accordance with the tasks and using the available technical means;
coordination of the work of the shop sections;
remote control of flow-transport systems;
control over the work of operating personnel.
4. Central control points:
ensuring the implementation of operational plans;
control and management of the progress of the implementation of shift and daily planned assignments for the shops and the enterprise;
collection, preliminary processing of information about the state of the technological process, fixing deviations from the planned indicators;
coordination of the work of the shops and services of the enterprise;
formation of reporting information on the progress of implementation of planned tasks, the state of the technological process, equipment, stocks.
The solution to these tasks is ensured by performing the following functions:
collection, transmission, reception of information, its primary processing, reduction to a form convenient for operational control and accounting;
control of equipment operation, implementation of shift and daily plans of workshops;
elimination of emergency situations;
control over time and reasons for equipment downtime;
accounting of materials, fuel, energy consumption;
coordination of production activities of shops, services of the enterprise;
Control over the implementation of the instructions of the company's management.
The dispatch service in the APCS is designed to solve the following problems:
1) operational accounting:
production output per hour, shift, day;
shipment of products by type for periods;
residues of manufactured products;
the number of violations of technological regimes;
equipment downtime due to reasons for periods;
equipment operation time for periods;
the number of equipment shutdowns between repairs;
consumption of raw materials, materials, resources for periods.
2) operational analysis:
analysis of the implementation of the plan, detection of interference;
assessment of pre-emergency situations, identification of trends;
determination of changes in the rhythm of production;
analysis of the state of equipment and the reasons for downtime;
identification of bottlenecks and reserves;
analysis of trends in TPE;
analysis of trends in stocks, vehicles;
determination of the availability of energy resources;
control of production, shipment, residuals of finished products;
analysis of the implementation of the production plan, taking into account deviations;
analysis of technological parameters, product quality;
assessment of deviations of product parameters from the required ones;
analysis of the actual values of technological parameters;
analysis of deviations of technological parameters;
analysis of operation and types of equipment downtime;
identification of deviations from the norms of consumption of raw materials, energy resources;
analysis of the quality of raw materials, resources;
determination of stocks of raw materials, vehicles;
analysis of TEP for periods;
identification of deviations of TPE from the standards.
3) operational planning:
production output for periods;
elements of production for periods;
production of products and consumption of production elements.
4) operational forecasting:
production output for the period;
anticipation of emergency situations;
calculation of TEP.
5) operational management:
coordination of loads of performers, equipment, transport;
prevention of emergency situations;
adjustment of equipment repair schedules;
changing the operating modes of the equipment.
The dispatcher's work requires a high speed of making optimal decisions, for which it is necessary to prepare in advance a set of basic situations and the best decisions for each situation. For production, it is advisable to develop a technological process for the work of each dispatcher. At the beginning, the main functions and tasks to be performed by the dispatcher are determined, an enlarged technology of the dispatcher's work is drawn up. Then, on the basis of the enlarged technology, detailed control flow charts are developed. The structure of dispatching control is determined by the organizational structure of the enterprise, the permissible degree of centralization of control for a given production.
With a centralized control system in the shops, a number of operator points are organized, allowing them to be controlled in accordance with the instructions of the enterprise management.
Operators in the process control system carry out control of technological objects. They can operate in and out of the control loop. In the control loop, the operator performs control functions using the recommendations for rational control developed by technical means. Outside the control loop, the operator sets the operating modes for the system, controls the operation of the system and, if necessary (emergency, failure), takes over the control of the technological object. The work of an operator in an automated process control system is characterized by the presence of complex equipment, large flows of information, and limited time for making decisions.
The complexity of the operator's work in an automated process control system is determined by the need to study the technology of a controlled process, a large number of instrumentation and controls located on the control panel, and a significant psychological load. When managing a technological object, the operator provides:
Consolidation of technical knowledge on the site (equipment, modes), communication with other sites; location of control devices, control, protection, alarm;
tracking the progress of the technological process;
assessment of the quality of automation, stabilization of parameters, the nature of external disturbances;
Remote control in various situations, regulation of parameters in conditions of solving flow problems, minimization of the number of devices;
carrying out actions to turn on and off auxiliary equipment;
formation of messages to operating personnel;
diagnostics of malfunctions and their elimination;
fast reading of instrument readings.
Main literature
Fedorov Yu.N. Process Control Engineer's Handbook: Design and Development. - M .: Infra-Engineering, 2008 .-- 928 p.
Nesterov A.L. Design of process control systems: Methodological guide. Book 1. - SPb .: DEAN Publishing House, - 2006 .-- 757 p.
Nesterov A.L. Design of process control systems: Methodological guide. Book 2. - SPb .: DEAN Publishing House, - 2009 .-- 944 p.
Industry-wide guiding methodological materials on the creation and application of automated control systems for technological processes in industries (ORMM - 3 APCS), - M .: GKNT. 1986
additional literature
Materials (edit) information portals: www.kazatomprom.kz, www.kipiasoft.com, www.automatization.ru, www.scada.ru, www.automation-drives.ru, www.siemens.com, www.ad.siemens.de
Introduction 2
1. Development of a structural diagram 6
2. Development of electrical circuit diagram 8
3. Calculated part 11
4. Design development 16
Conclusion 19
List of sources used 20
Appendix A - List of Elements
Introduction
Measuring and controlling temperature is one of the most important tasks of a person, both in the production process and in everyday life, since many processes are regulated by temperature, for example:
Heating regulation based on the measurement of the temperature difference between the heating medium at the inlet and outlet, as well as the difference between the indoor and outdoor temperatures;
Regulation of water temperature in washing machine;
Temperature control of an electric iron, electric stove, oven, etc .;
Temperature control of the nodes of a personal computer.
In addition, other parameters such as flow, level, etc. can be indirectly determined by measuring the temperature.
Electronic systems for automatic temperature control are widespread, they are used in warehouses finished products, food products, medicines, in chambers for growing mushrooms, in industrial premises, as well as in the premises of farms, poultry houses, greenhouses.
Automatic control systems are designed to control technological processes, while the nature of the behavior and their parameters are known. In this case, the control object is considered as deterministic.
These systems control the relationship between the current (measured) state of the object and the established “norm of behavior according to the known mathematical model of the object. Based on the results of processing the information received, a judgment is issued on the state of the objects of control. Thus, the task of the SAC is to assign an object to one of the possible qualitative states, and not to obtain quantitative information about the object, which is typical for IS.
In SAK, thanks to the transition from measurement absolute values to relative (as a percentage of "normal" value), the work efficiency is significantly increased. With this method of quantitative assessment, the SAC operator receives information in units that directly characterize the level of danger in the behavior of the controlled object or process.
Automated control systems in flexibleproduction systems (FPS)
SAC GPS is its most important module, since it is it that determines the possibilities of implementing an unmanned production process.
SAK solves the following tasks:
- obtaining and presenting information about the properties, technical condition and spatial location of monitored objects and the state of technology O logical environment;
- comparison of the actual values of the parameters with the specified ones;
- transmission of information about mismatches for decision-making at various levels of SBS management;
- obtaining and presenting information about the performance of functions.
SAK provides: the possibility of automatic restructuring of control means within a given nomenclature of controlled objects; correspondence of the dynamic characteristics of the SAC to the dynamic properties of the controlled objects; completeness and reliability of control, including control of transformation and transmission of information; reliability of controls.
In terms of the impact on the object, control can be active and passive. The most expedient and promising is the active control of product parameters and modes of technological processes and environments in the processing zone, since it allows them to be regulated or controlled and to exclude (reduce) the appearance of defects.
Rice. 1.1 - Relationship between the SAC and the GPS elements
1 - material flows; 2 - control signals; 3 - control and measurement information.
Typical structure SAC (Fig. 1.2) flexible manufacturing systems includes three levels. The upper level provides general control of the aggregate of the flexible production module and coordinates them, reconfigures and repairs, issues information to the control panel of flexible production systems, receives, processes and summarizes information coming from the middle level; control of the volume and quality of products and tools; control over the execution of a set of operations performed by flexible production modules (FPM).
Rice. 1.2 - Structure of SAC in GPS
The middle level provides control of the PMG and the presentation of generalized information on the properties, technical condition and spatial location of the controlled objects and components of the PMG to the upper level. At the same time, the following tasks are solved: quality control of the manufactured product at the PMG, self-control and control of the functioning of a lower level; processing information about the parameters of the technological environment.
The lower level provides control of processing and assembly objects, technical condition and spatial arrangement of the components of the PMG (CNC machines, PR). At this level, the SAC solves the following tasks: input and output control of the production facility; receiving and processing information about the controlled parameters of the processing or assembly object during processing; transfer of information to the middle level; control over the implementation of transitions. The control means at the lower level are positioning sensors and control of the technological environment (temperature, pressure, speed, humidity), etc.
In this case, the measurement parameters can be separated both in time and in space. So some of the parameters can be controlled in the processing area, another - during transportation, the third - during storage, etc.
In principle, it is possible to divide control between different processing cells and build it according to one of the following principles: with rechecking of control parameters on the next cell in whole or in part; with the division of the complete group of checked -irel meters between the output of the previous and the input of the next cells; with the absence of repeated control at the entrance of the next cell.
Control in the processing zone includes control of the correct installation and fixation of the workpiece in the clamping device of the machine, and in the case of active control, a number of geometric (dimensional and shape parameters) characteristics.
To ensure product quality, not only the parameters of the product are controlled, but also a number of parameters of the tool (change, degree of wear, blade temperature), machine (clamping and positioning of the workpiece, absence of foreign objects in the processing zone, deformation of machine parts), processing mode (force, speed , cutting power, torque, feed and depth of cut), the process medium (temperature and flow rate of the coolant, external influences, including vibration, temperature, air pressure and humidity) and supporting systems.
The monitored parameters of the technical means of the GPS, according to the functional attribute, can be divided into the parameters of the intended purpose, power supply, operating modes, readiness for work, control circuits, safety, as well as parameters that determine the operability and reliability of the elements of the GPS.
The upper-level computer makes a decision on the operation mode of the SAC based on information from automatic cells and provides periodic self-control of its work.
In the reconfiguration mode, the control information is fed to the upper-level computer, which makes a decision on reconfiguring the control system at the middle and lower levels. The computer of the lower level establishes a set of controlled parameters and functions of processing objects and control standards.
Emergency mode is initiated by any level of BAC. At the lower level, it is caused by an increase in the permissible level of rejects, a deviation from the norm of the parameters of the PMG or the controls themselves.
The nominal operating mode of the SAC. The signal about the emergency state from each level is transmitted to the higher one displayed on the control panel of the GPS.
Software SAK (PO) consists of:
- Software for monitoring the progress of the manufacturing process at specific workplaces of the GPS;
- Control system software as a control subsystem:
- The SAK software implements the following functions:
- Automatic collection of information about the actual release of parts on controlled equipment;
- Automatic accounting of equipment downtime and differentiation for reasons;
- A documented call to the repair services of the workshop;
- Issuance of operational information about the progress of production, downtime to the line personnel of the shop during the shift;
- Automatic reception and processing of information about the dimensions of parts for TP control;
- Automatic processing of acceptance control information.
SAK are divided into several classes, which are designed to measure the geometric, physical and mechanical parameters of parts and assembly units and electrical parameters and characteristics.
1 Development of an electrical block diagram
The electrical structural diagram is presented in the graphic part of the course project BKKP.023619.100 E1.
According to the terms of course design, the developed scheme must meet the following requirements:
Device name -automatic control systems
Adjustable (monitored) parameter - temperature;
Thermoelectric sensor;
Type, family of control device - microcontroller NEC
Executive (regulating) device - DC motor;
Alarm - light
Electronic key - bipolar transistor;
Supply voltage - 220 V, 50 Hz;
Power consumed by the executive device - 20 W;
Additional requirements forthe condition of course design:
Constructive design - panel board
Indication of set and actual temperatures - digital (3 digits)
When the temperature drops beyond the set limit, an alarm is triggered and the fan motor is turned off.
Operating temperature range: 100 ... 300 o C
The devices included in the circuit perform the following functions:
Converter AC / DC accepts an AC input voltage, outputs a stabilized DC voltage with a high degree of accuracy.
The voltage-to-current converter is designed to convert the AC voltage into a unified DC output signal (4… 20mA);
Electronic key - used for switching the control circuit;
DC motor - adjusts the temperature value at the output of the circuit;
Fan - controls the temperature range;
Light alarm - turns on when the temperature drops beyond the set limit;
Reference voltage source - to power the ADC in the microcontroller.
- Scheme work:
The circuit is powered from a 220 V mains source with an industrial frequency of 50 Hz. An AC is used to power the circuit elements. DC converter. With two output channels 12V, 24V.
24V is required for power supplyconverter voltage current (PNT).
12V is needed to power the DC motor.
The microcontroller is powered by a voltage of 5 V, from a stabilizer microcircuit DA 2.
The operation of the system is activated by closing the switch SA1.
Signals are received at the inputs of the MC, one of them from the operator's console, the second from the sensor.
The master device (operator panel) are buttons SB1 "More", SB2 "Less", SB3 "Job", which are connected to the inputs of the microcontroller NEC , respectively P45, P44, P43.
The operator sets the required temperature value through the control panel. The value is written through the arithmetic logic unit to register1. Thus, the counting limits are set.
The second, analog signal, frommeasuring transducer with a fixed temperature measuring range -converter voltage current (PNT), entering the input ANI 0 of the microcontroller, is converted by the built-in ADC into a discrete (digital code), then enters the memory register 2, and is stored until the comparison signal arrives.
The values of register1 and register2 are compared on a digital comparator, and in case of a decrease in the actual value over the set value, the EC closes, an alarm is triggered and the fan motor is turned off. And in the case of normal operation: set and actual values are the same, the fan monitors the temperature range.
Also, the signal from registers 1 and 2 is fed to the mode sampling circuit, and then to the decoder, which is needed to display the temperature values on the digital display.
2. Development of an electrical circuit diagram
The electrical schematic diagram is shown in the drawing BKKP.023619.100 E3.
The stand voltage is 220V 50Hz.
However, a voltage of a lower level is used directly to power the circuit elements. To provide such power, the circuit uses AC- DC converter series TDK lambda LWD 15. With two output channels of voltage 12V, 24V. I chose this converter based on the required parameters, low cost and versatility. The work of the system is activated by closing the switch. SA 1.
To display the work of the stand there is an indicator HL 1.
The operator panel contains 3 buttons KM1-1:
By pressing the SB1 button - the operator increases the temperature value, and the indication displays the set value at the time of input.
Pressing the SB2 button - the operator decreases the set temperature value and the indication displays the set value at the time of input,
Pressing SB3 - the operator confirms the set temperature.
A thermal converter with a unified output signal of the KTXA type measures the temperature.The primary thermal converter (PP) is completed with a measuring transducer (MT), which is located in the terminal head and provides continuous temperature conversion into a unified output current signal 4-20 mA, which is fed to the microcontroller input.
The primary thermal converters are thermoelectric converters KTHA, KTKhK, KTNN, KTZhK modifications 01.XX;
To complete the primary thermal converters, a measuring transducer with a fixed temperature measurement range - PNT was used.
I chose PNT type KTHA 01.06-U10 - IT-T 310 - 20 - 800.cl.0.5; (0 ... 500) ° С, 4-20 mA- cable thermal converter chromel-alumel graduation, constructive modification 01.06-U10, terminal head made of polymer material with PNT measuring transducer, working junction is insulated(AND), heat-resistant cover(Т 310) with a diameter of 20 mm. installation length ( L) 800 mm. Transmitter type PNT, accuracy class 1 in the temperature range O - 500 ° C. Unified output signal 4-20 mA.
The LED of the brand is used as a light signaling AL308.
Digital indication - ALS 324 A with a common cathode.
Microcircuit stabilizer KR142en5a, required to power the microcontroller NEC.
I chose an electronic key on a bipolar transistor KT805 A. Since its parameters satisfy the condition.
The central and main element is the microcontroller NEC 78K0S / KA1 + series. I chose this MK because oflow cost, the required number of pins and the required parameters. MK NEC has a standard structure. It contains a processor, internal read-only memory for storing a program (IROM in NEC terminology), internal random access memory for data storage (IRAM), and a set of peripherals.
Some characteristicsmicrocontroller NEC 78K0S / KA1 + series.
Figure 2.1 - assignment of microcontroller pins NEC
Reference voltage source (RON) DA 1 used to power the ADC as part of the microcontroller.ION is connected to the reference voltage input AVref.
ION MAX6125 I have chosen based on the necessary requirements. U in: 2.7 ... 12.6 V, U out: 2.450 ... 2.550 V.
Below are the ION of the company MAX , for clarity.
Figure 2.2 - a visual diagram of the company ION connection MAX
3. Calculated part
3.1.1. Electronic key calculation
Figure 3.1 - Calculated scheme
Diode VD 1 performs the function of protecting the switching device: DC motor M. I chose the KD 105B diode because of the suitable parameters and examples of other circuits.
3.1.2. We calculate the parameters of the circuit to select the transistor.
3.1.3. We calculate the rated load current according to the formula:
(3.1)
3.1.4. We calculate the collector current taking into account the starting mode according to the formula:
(3.2)
3.1.3. Initial data
Collector supply voltage U pit = 12 V.
Load current I n = 3.3 A.
U o out DD 1< 0,6В
U 1 out DD 1 = U pit - 0.7 = 4.3V (3.3)
We choose a bipolar silicon transistor KT 838 A by load current and supply voltage.
Bipolar silicon transistor KT 838A has the following parameters:
H21 e = 150 - 3000
Uke us = 5V
Ube us = 1.5V
Uke max = 150 V
Ik max = 5 A
Pk max = 250 W
U be pore = 1.5V
Calculation procedure
3.1.4 At the output of the microcontroller DD 1 discrete signal 0 or 1. When the signal level is low, the transistor VT 1 must be securely closed, fully open at a high level and in saturation mode. To do the first:
U o out DD 1< U бэ порог. (3.4)
0.6V< 1,5В.
3.1.5. We calculate the base current at which its saturation mode is provided according to the formula:
(3.5)
3.1.6 Calculate the current flowing through the resistor R 11
(3.6)
K - base current safety factor, taking into account the aging of the transistor K = 1.3
3.1.7. We calculate the resistance of the resistor R 11
(3.7)
Choosing the resistance of the resistor R 11 from the standard range of nominal resistance values, equal to R = 75Ω.
R 11
Resistor C2-33N-0.25- 75 Ohm - 5% ОЖО.468.552 TU
3.1.8. We calculate the power of the resistor R 11
(3.8)
Choosing a resistor R 11 0.1 W
3.1.9. Finding the power dissipated by the transistor
(3.11)
Since P VT 1< P k max , а именно: 16.5 watts< 250 Вт, транзистор выбран правильно.
3.1.11. Since u bae us = 1.5 V, then we take the switching voltage of the transistor from the closed state to the open
(3.12)
and the switching voltage from open to closed
(3.13)
The corresponding base currents will be I b + = I b - = 0.039A
(3.14)
- calculation of light signaling:
U pit
Figure 1.3 - Calculated circuit
3.2.1. Initial data:
Supply voltage: U pit = 5 V
AL 308 LED, with parameters:
Forward voltage drop across the LED: Upr = 2 V
Nominal LED forward current: Ipr.nom. = 10 mA
Calculation procedure
3.2.2. We calculate the resistance of the resistor R 9, according to the formula:
R 9 = (3.13)
R 9 =
3.2.3 Choosing resistance R 9 from a number of standard, equal to 300 Ohm
According to the results of calculations, we choose as a resistor R 9
C 2-33-0.125- 300 Ohm ± 5% ОЖО.467.173.TU
3.3. We calculate the parameters of the resistor R 7 , which is located at the entrance of the MK ANI 0 and we exit from PNT:
3.3.1. Knowing the unified current signal, which is 5 ... 20mA and the supply voltage equal to 5V, using the Ohm's law formula, we find the resistance:
4 Design development
4.1 Calculating the dimensions of the printed circuit board
A printed circuit board is a rectangular plate made of electrical insulating material, used as a base for the installation and mechanical fastening of hinged radioelements, as well as for their electrical connection to each other by means of printed wiring.
For the manufacture of printed circuit boards, foil-clad fiberglass is most often used. The dimensions of each side must be multiples of: 2.5, 5, 10 with a length of up to 100, 350 and more than 350 mm, respectively. Maximum size any of the sides cannot exceed 470 mm, and the aspect ratio must be no more than 3: 1.
Determining the dimensions of the board is reduced to finding the total installation areas of small-sized, medium-sized and large-sized elements. And for this you need to know the overall dimensions of each element. Small-sized include all miniature elements, namely, resistors (P ≤ 0.5 W), small-sized capacitors, diodes, etc. To medium-sized ones - microcircuits in rectangular cases, resistors (P ≥ 0.5 W), electrolytic capacitors, etc. Large-sized ones - variable resistors and capacitors, semiconductor devices on radiators, etc.
The overall dimensions, as well as the installation area of all elements that are located on the board, are shown in Table 4.1.
Table 4.1 - Overall dimensions of elements and their installation area
|
Element designation |
Item type |
Overall dimensions, mm 2 |
Quantity, pcs |
Installation area, mm 2 |
Dimensions (edit) |
2 |
|||||
|
R1-R6, R8, R10, R12, R13 |
C1-4 |
6 x 2.3 |
mg |
||
|
R7, R9, R11 |
S2-33 |
7 x 3 |
mg |
||
|
KT502V |
5.2 x 5.2 |
27,04 |
mg |
||
|
VT 2- VT 4 |
KT3142A |
5x5 |
mg |
||
|
VD 1 |
KD 105B |
7 x 4.5 |
31,5 |
mg |
|
|
MAX6125 |
3 x 2.6 |
7, 8 |
Wed |
||
|
kr142en5a |
16.5 x 10.7 |
176,6 |
Wed |
||
|
78K0S / KA1 + |
6.6 x 8.1 |
53,9 |
Wed |
||
|
HC -49 U |
11x5 |
mg |
|||
|
C1, C5 |
K50 - 6 |
4 x 7 |
cr |
Continuation of table 4.
|
C2, C 3, C 4 |
K73-17 |
8 x 12 |
cr |
||
|
C6, C7 |
KM-5B |
4.5x 6 |
mg |
||
|
HG1-HG3 |
ALS 324 A |
19.5 x10.2 |
596,7 |
cr |
Find the area occupied by elements of one type of dimension
S mg = 138 + 63 + 27.04 + 75 + 31.5 + 55 + 54 = 393.54 mm 2 (6)
S cr = 176.6 + 7.8 + 53.9 + 56 + 288 + 596.7 = 1179 mm 2
According to the data given in table 4.1, we calculate the area of the installation area
S mz = 4 ∙ S mg + 3 ∙ S sg + 1.5 ∙ S kg, (4.1)
where S мз - the area of the calculated mounting area;
S mg - total area occupied by small-sized radioelements, cm 2 ;
S cr - total area occupied by medium-sized radioelements, cm 2 ;
S kg - total area occupied by large-sized radioelements, cm 2 .
S mz = 4∙ (393,54) + 3∙ (1179) = 5111.16 mm 2 = 51.1 cm 2
The area of the printed circuit board must not be less than 52 cm 2 .
5. Development of the stand design
The drawing of the view block is presented in the graphic part of the course project BKKP.023619.100 VO
When developing a structure, the following basic requirements must be taken into account:
The design of the device must be suitable for the operating conditions
The device and its parts should not be overloaded during operation from exposure to current, vibration, temperature and other loads. The elements of devices must withstand their permissible values for a certain time, subject to failure-free operation.
Most of the parts are mounted on printed circuit board from one-sided foil fiberglass. It is reinforced inside the case, where the power supply is also placed. The device controls are located on the front panel. Toggle switch “mains”, fuses, light signaling, digital indication, buttons.
The automatic control system is housed in the case Bopla model NGS 9806 c the changes and overall dimensions 170x93x90 made of plastic.
There are mounting holes on the body for panel mounting.
The front panel contains: LED, digital indication, light signaling, and button modules.
The L2T-1-1 toggle switch has only two positions: on - the upward position of the toggle switch, off - the downward position of the toggle switch. A terminal block is attached to the rear wall of the case for connecting the converter, PNT, fan motor to electrical network 220 V 50 Hz.Power is connected via a standard cord with a plug.
The printed circuit assembly is attached to the body using four M3-1.5 GOST17473-72 screws, which are cut through the board into the body projections. These protrusions are cast together with the body.
AC-DC company converter TDK - lambda LWD series 15 is attached to the bottom wall of the case with 4 screws M3-1.5 GOST 17473-72.
Conclusion
In this course project, an automatic temperature control system was developed, during the development, the parameters of the given devices were calculated, in particular, an electronic key, a resistor for a light alarm and a resistor at the output of the PNT. In addition, the dimensions of the printed circuit board were calculated. All elements of the system are widely used, readily available for purchase and interchangeable, which ensures high maintainability of the circuit.
The graphic part of the course project is represented by an electrical structural diagram and an electrical schematic diagram of the stand and a general drawing.
When designing a course project, a text editor was used Microsoft Word 2007 and graphic editor Splan 7.0
List of sources used
1 Industrial electronics and microelectronics: Galkin V.I., Pelevin
E.V. Textbook. - Minsk: Belarus. 2000 - 350 p .: ill.
2 Printed boards. Technical requirements TT600.059.008
3 Rules for the implementation of electrical circuits GOST 2.702-75
4 Fundamentals of automation / E.M. Gordin - M .: Mechanical Engineering, 1978 - 304p.
5 Semiconductor devices: Handbook / V.I. Galkin, A.A. Bulychev,
P.N. Lyamin. - Minsk: Belarus, 1994 - 347
6 Diodes: Handbook O.P. Grigoriev, V.Ya. Zamyatin, B.V. Kondrat'ev,
S.L. Pozhidaev. Radio and communication, 1990.
7 Resistors, capacitors, transformers, chokes, switching
REA devices: Ref. N.M. Akimov, E.P. Vashchukov, V.A.Prokhorenko,
Yu.P. Khodorenok. - Minsk: Belarus, 1994.
8 Semiconductor devices: Handbook V.I. Galkin, A.L.Bulychev,
P.M. Lyamin. - Minsk: Belarus, 1994.
9 Usatenko S.T., Kachenok T.K., Terekhova M.V. Execution of electrical circuits according to ESKD: Handbook. Moscow: Standards Publishing House, 1989.
10 OST45.010.030-92 Forming of leads and installation of electronic products on printed circuit boards.
11 STP 1.001-2001 Rules for drawing up an explanatory note for 1 course and diploma project.
12 Information from the sitehttp://baza-referat.ru/Automated_control_Systems
13 Information from the sitehttp://forum.eldigi.ru/index.php?showtopic=2
Technological requirements for the development of automatic control systems
When creating automatic control systems for technological processes of agricultural production, one of the most critical stages is the development of the optimal, that is, the most effective version of the technological process to be automated.
Due to the fact that agriculture is characterized by a variety of industries and a variety of technological processes, the development of an optimal technological process in each specific case is a very difficult task. The development of unified agricultural production processes contributes to the success of the development of optimal technological processes suitable for automation. Therefore, very relevant, especially in terms of translation Agriculture on an industrial basis, is the problem of typification, universalization and even standardization of agricultural technological processes and technology.
The transfer of agriculture to an industrial basis is closely related to the processes of concentration and intensification of production. In these conditions, when, along with large flows of raw materials, energy, labor, there is a large flow of interconnected information, accurate and correct understanding of this information, making appropriate optimal decisions and, in general, full-fledged production management are possible only with the use of methods and means of automation. However, the application of the achievements of automation requires a certain technological preparation of production processes.
The experience of re-equipping the leading sectors of the national economy shows that the effectiveness of automation depends on the interrelated solution of three main tasks: 1) the development of new technological processes and their typification; 2) creation of technological equipment, which ensures high-quality performance of a typed technological process; 3) development of algorithms effective management technological processes, operations and equipment using technical means of automation.
The solution of the first problem requires special knowledge and the necessary experience to determine the specified parameters of accuracy, productivity, methods of processing, transportation, storage, to create methods of typing technological processes, etc. fully master the basics of technological science.
It is advisable to start typing the technological process in agricultural production with the drawing up of the so-called technological chain.
The technological chain reflects the interconnection of technological processes, individual operations and modes of machines involved in their implementation. For example, the technological chain of post-harvest processing of grain in the flow includes the following operations: delivery of grain from the combine, weighing grain, unloading it, transportation by elevator, primary cleaning from large impurities on rotary machines, transportation by elevator, drying, cooling, transportation by elevator, secondary cleaning from small impurities, transportation by auger, sorting on triremes, collecting in a bunker, weighing, transporting to a warehouse, weighing and storing.
The technological chain allows you to identify the order of operation of machines in accordance with the requirements of the process, the amount of work on operations, the required number of machines, to establish the optimal aggregation and the permissible degree of typification of technological processes. Thus, the technological chain makes it possible to deeply penetrate the very technology of the process in all its aspects.
Starting the development of automatic control systems, the developer must study the automation object well, fully understand all possible modes of operation.
It should be borne in mind that the development of automatic control systems for an object is often necessary for production different levels development. In this regard, the degree of automation and the totality of operations and modes are determined by the level of development of the production itself. Consequently, any technological process can be divided into operations in different ways. But with this division, the developer must always answer the following basic questions.
1. What is the purpose and task of the automatic control system?
2. What blocks make up the control object?
3. What functional and control connections are there between the blocks that determine the future system?
4. What are the modes of the control object and its blocks and how many technologically permissible transitions between these modes?
5. What specific algorithms describe this or that mode?
6. What sensors and actuators can be used for this system?
7. What mathematical equations describe the interaction of control signals and disturbance signals that characterize a particular mode of operation of the systems?
After analyzing technological processes or individual operations, it is necessary to establish the entire volume of information parameters characterizing the technology and all their interrelationships.
The information accumulated according to the questions posed should be reflected in a compact and convenient form for further work. This is what makes it possible to identify a list of information parameters.
The classification of information parameters and the technological chain make it possible to draw up a block diagram of a control system, which is a combination of a control object and a control device.
It should be borne in mind that incomplete and inaccurate processing of all information leads to its distortion at the following levels, to a delay in making decisions and measures to coordinate the actions of installations, production lines, workshops and, as a result, to an increase in production costs, a decrease in profitability, product damage etc.
- Bykov Ivan Andreevich, bachelor, student
- Volzhsky Polytechnic Institute (branch) Volgograd State Technical University
- NATURAL GAS
- AUTOMATION
- PROCESS
- CLEANING
This publication is devoted to the development of a control system for the technological process of natural gas purification, in order to increase economic efficiency, located at the OJSC "Volzhsky Orgsintez" enterprise. In this work, an automatic control system was developed by replacing outdated components with modern ones, using an OWEN PLC 160 microprocessor controller as a basis for an automatic control system.
- Development of an automated control system for the technological process of ammonia synthesis
- On the possibility of using a filler for lubricants to improve the running-in of friction pairs
- Development of an automated control system for the technological process of air separation
- Development of an automated control system for the production of lubricating-cooling liquid
The use of natural gas without purification in the technological process is impractical. The impurities contained in it, in particular, ethane, propane and higher-range hydrocarbons, hydrogen sulfide are incompatible with the normal operation of the cyanide gas generator and lead to carbonization and poisoning of the platinum catalyst. Therefore, there is a need for preliminary purification of natural gas.
Automation of the natural gas purification process improves the quality of regulation, improves the working conditions of workers, since the use of automation makes it possible to reduce to a minimum the stay of workers in production facilities
Figure 1. Process flow diagram for natural gas purification.
Key performance indicators:
- End product quality: concentration of impurities in the gas
- Productivity: the amount of gas per unit of time
- Economic costs: consumption of natural gas, consumption of nitrogen, water and electricity
Adsorbents used in flue gas cleaning processes must meet the appropriate requirements:
- have a high adsorption capacity when absorbing contaminants with small accumulations of them in gas mixtures;
- have high selectivity;
- have high mechanical strength;
- have the ability to recover;
- have a low cost.
The main industrial adsorbents are porous bodies with a large volume of micropores. The characteristics of adsorbents are determined by the nature of the material from which they are made and the porous internal structure.
Management objectives: to maintain the concentration of harmful impurities in the gas at a minimum level with the optimal amount of purified gas obtained and minimum process costs, provided that the process must be trouble-free, safe and continuous.
Selection of adjustable parameters
The quality is not subject to regulation, since there are no automation tools for measuring the concentration of impurities in the gas.
Parameters influencing the technological process:
- natural gas consumption;
- water consumption;
- nitrogen consumption;
- temperature of natural gas leaving the refrigerator;
- dampers pressure;
- pressure in the collectors.
The monitored parameters are selected from the following considerations: with a minimum number of them, they should give maximum information about the process.
First of all, all adjustable parameters are subject to control: pressure in dampers, temperature of natural gas at the outlet of the refrigerator, pressure in collectors, pressure difference in adsorbers.
The parameters are subject to control, the current value of which must be known to calculate the technical and economic indicators: the consumption of water, nitrogen, purge gas, natural gas, the temperature of the compressor motor.
When choosing the parameters to be signaled, it is necessary to analyze the facility for fire and explosion safety and identify parameters that can lead to an emergency situation in the facility.
When choosing technical means in this project, the use of the following elements is proposed:
Thermocouples with a unified output signal Metran - 280Ex are used as temperature sensors. Metran-150 Ex pressure transducers are used as gauge pressure transducers, designed for continuous conversion of excess pressure into a unified output current signal. An Emerson Rosemount8800D Ex flowmeter was selected for flow measurement. MIM-250 actuators are used to introduce a regulatory effect. A frequency converter of the HYUNDAI N700E-2200HF type was selected as an electric drive for the compressor. The EP-Ex electro-pneumatic converter is used to convert a unified continuous DC signal into a unified proportional pneumatic continuous signal. The passive barrier of spark protection BIP-1 is used to ensure the intrinsic safety of the circuits of the EP-Ex electro-pneumatic converters and the EP-Ex electro-pneumatic positioners located in the explosive zone. To power the sensors, as well as the controller modules, a DLP180-24 24V DC / 7.5A power supply unit from TDK-Lambda was selected. To control and regulate the technological parameters of the process, a programmable logic controller PLC160 from OWEN is selected.
When determining the performance indicators of the process, it was concluded that the main performance indicator is the quality of the resulting product at the exit from the control object. The OWEN PLC 160 was chosen as the regulating controller, which provides the specified regulation of the process of obtaining hydrogen cyanide.
In comparison with the current system, the main problems of optimization of the control system were formed and solved, such as the compilation of a mathematical model of the control object. An analysis of the observability and controllability of the object of management was carried out, an analysis of the quality of management of the object. The calculation of the tuning coefficients P–, PI–, PID – regulators was carried out, the modeling of the control process was carried out. In the course of calculations, it was found that the PID controller has the best control quality indicators.
Bibliography
- Shuvalov V.V., Ogadzhanov G.A., Golubyatnikov V.A. Automation of production processes in chemical industry... - M .: Chemistry 1991 .-- S. 480.
- Kutepov A.M., Bondareva T.I., Berengerten M.G. General chemical technology. - M.: Higher school, 1990 .-- 387 p.
- Automated control systems in industry: textbook. allowance / M. A. Trushnikov [and others]; VPI (branch) VolgSTU. - Volgograd: VolgGTU, 2010 .-- 97 p.
- Fundamentals of automation of typical technological processes in the chemical industry and in mechanical engineering: textbook. allowance / MA Trushnikov [and others]; VPI (branch) VolgSTU. - Volgograd: VolgGTU, 2012 .-- 107 p.
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