Development of a structural diagram of the ASU MKT. Drawing up a functional diagram and description of the main functional units of the ACS Block diagram of automated monitoring and control systems

Lecture 9

When developing an automation project, first of all, it is necessary to decide from what places certain parts of the object will be controlled, where will be located control points, operator rooms, what should be the relationship between them, i.e. it is necessary to resolve the issues of choosing a management structure. The control structure is understood as a set of parts of an automatic system, into which it can be divided according to a certain criterion, as well as the ways of transmission of influences between them. A graphical representation of a management structure is called a structural diagram. Although the initial data for the selection of the management structure and its hierarchy with varying degrees of detail are negotiated by the customer when issuing the design assignment, the complete management structure should be developed by the design organization.

In the very general view the block diagram of the automation system is shown in Figure 9.1. The automation system consists of an automation object and a control system for this object. Due to a certain interaction between the automation object and the control system, the automation system as a whole provides the required result of the object functioning, characterized by parameters x 1 x 2 ... x n

The operation of a complex automation object is characterized by a number of auxiliary parameters y 1, y 2, ..., y j, which must also be monitored and regulated.

During operation, the object receives disturbing influences f 1, f 2, ..., f i, causing deviations of the parameters x 1, x 2, x n from their required values. Information about the current values ​​x 1, x 2, x n, y 1, y 2, yn enters the control system and is compared with the prescribed values ​​gj, g 2, ..., gk, as a result of which the control system generates control actions E 1, E 2, ..., E m to compensate for deviations in the output parameters.

Figure 9.1 - Block diagram of the automation system

The choice of the control structure for the object of automation has a significant impact on the efficiency of its work, reducing the relative cost of the control system, its reliability, maintainability, etc.

In general, any system can be represented:

· Constructive structure;

· Functional structure;

· Algorithmic structure.

In the constructive structure of the system, each of its parts is an independent constructive whole (Figure 9.1).

The constructive scheme contains:

· Object and automation system;

· Information and control flows.

In the algorithmic structure, each part is designed to perform a specific algorithm for transforming the input signal, which is part of the entire algorithm for the functioning of the system.

The designer develops an algorithmic block diagram (ACC) of the automation object based on differential equations or graphical characteristics. The automation object is represented in the form of several links with various transfer functions interconnected. In ACC, individual links may not have physical integrity, but their connection (the scheme as a whole) in terms of static and dynamic properties, according to the algorithm of functioning, should be equivalent to the automation object. Figure 9.2 shows an example of an ACS ACS.

Figure 9.2 - Algorithmic block diagram, presented in the form of simple links

In a functional structure, each part is designed to perform a specific function.

In automation projects, structural structural diagrams with elements of functional signs are depicted. Full information about the functional structure with an indication of local control loops, control channels and process control are given in functional diagrams (lecture 10).

The structural diagram of the APCS is developed at the "Project" stage in a two-stage design and corresponds to the composition of the system. As an example, Figure 9.3 shows a block diagram of sulfuric acid production management.

Figure 9.3 - Fragment of the structural diagram of the management and control of sulfuric acid production:

1 - communication line with the workshop chemical laboratory; 2 - communication line with points of control and management of the acid section; 3 - communication line with the point of control and management of III and IV technological lines

The structural diagram shows in a general form the main project decisions on the functional, organizational and technical structures of the APCS in compliance with the hierarchy of the system and the relationships between the control and management points, operational personnel and the technological control object. The principles of organizing the operational management of a technological object, the composition and designation of individual elements of the structural diagram, adopted during the implementation of the structural diagram, should be retained in all project documents on the APCS.

Table 9.1 - Functions of the APCS and their symbols in Figure 9.3

The block diagram shows the following elements:

1. technological divisions (departments, sections, workshops, production);

2. control and management points (local boards, operator and dispatch points, block boards, etc.);

3. technological personnel (operational) and additional special services providing operational management;

4. main functions and technical means ensuring their implementation at each control and management point;

5. the relationship between subdivisions and with the superior ACS.

The functions of the APCS are encrypted and indicated in the diagram as numbers. Symbols of the APCS functions in Figure 9.3 are shown in Table 9.1.

The structural diagram of the automation system is carried out by nodes and includes all elements of the system from the sensor to the regulating body with an indication of the location, showing their interrelationships.

A structural diagram is intended for general acquaintance with the system (Fig. 6.2). Structural scheme - it is a diagram that defines the main functional parts of the product, their purpose and relationships.

Structure - it is a set of parts of an automated system, into which it can be divided according to a certain criterion, as well as ways of transferring influence between them. In general, any system can be represented by the following structures:

• ? constructive - when each part of the system is an independent constructive whole;
• ? functional - when each part of the system is designed to perform a specific function (complete information about the functional structure, indicating the control loops, is given on the automation diagram);

Rice. 6.2.

? algorithmic - when each part of the system is designed to perform a certain algorithm for transforming the input value, which is part of the operation algorithm.

It should be noted that structural diagrams may not be provided for simple automation objects.

Requirements for these schemes are established by RTM 252.40 “Automated control systems for technological processes. Structural schemes of management and control ". According to this document, structural structural diagrams contain: technological subdivisions of the automation object; points

control and management, including those that are not part of the project being developed, but have a connection with the projected system; technical staff and services that ensure the operational management and normal functioning of the technological facility; the main functions and technical means ensuring their implementation at each point of control and management; the relationship between the parts of the automation object.

The elements of the structural diagram are depicted as rectangles. Separate functional services and officials allowed to be depicted in a circle. The structure of this section is revealed inside the rectangles. The functions of the automated process control system are indicated by symbols, the decoding of which is given in the table above the main inscription along the width of the inscription. The relationship between the elements of the structural diagram is depicted by solid lines, mergers and branches - by broken lines. The thickness of the lines is as follows: conventional images - 0.5 mm, communication lines - 1 mm, the rest - 0.2 ... 0.3 mm. The sizes of the elements of structural diagrams are not regulated and are chosen at the discretion.

The example (Fig. 6.2) shows a fragment of the implementation of the design scheme for the management and control of a water treatment plant. In the lower part, the technological divisions of the automation object are disclosed; in the rectangles of the middle part - the main functions and technical means of the local control points of the units; in the upper part - the functions and technical means of the centralized control point of the station. Since the diagram occupies several sheets, the transitions of the communication lines to the subsequent sheets are indicated and a break in the rectangle revealing the structure of the automation object is shown.

The communication lines between the individual elements of the control system can indicate the direction of the transmitted information or control actions; if necessary, communication lines can be marked with letter designations of the type of communication, for example: K - control, C - signaling, remote control - remote control, AR - automatic regulation, DS - dispatch communication, PGS - industrial telephone (loudspeaker) communication, etc.

In general, a block diagram of a single-loop system automatic control is shown in Figure 1.1. The automatic control system consists of an automation object and a control system for this object. Due to a certain interaction between the automation object and the control scheme, the automation system as a whole provides the required result of the object's functioning, characterizing its output parameters and characteristics.

Any technological process is characterized by certain physical quantities (parameters). For the rational course of the technological process, some of its parameters must be kept constant, and some must be changed according to a certain law. During the operation of an object controlled by an automation system, the main task is to maintain rational conditions for the flow of the technological process.

Let us consider the basic principles of constructing the structures of local automatic control systems. With automatic control, as a rule, tasks of three types are solved.

The first type of tasks includes maintaining one or more technological parameters at a given level. Automatic control systems, critical tasks of this type are called stabilization systems. Examples of stabilization systems are systems for regulating the temperature and humidity of air in air conditioning installations, the pressure and temperature of superheated steam in boilers, the number of revolutions in steam and gas turbines, electric motors, etc.

The second type of problem is the maintenance of correspondence between two dependent or one dependent and other independent quantities. Systems that regulate ratios are called tracking automatic systems, for example, automatic systems for regulating the fuel-air ratio in the process of fuel combustion or the ratio of steam consumption-water consumption when feeding boilers with water, etc.

The third type of tasks includes the change in the controlled value over time according to a certain law. Systems that solve this type of problem are called software control systems. A typical example of this type of system is a temperature control system for heat treatment metal.

V last years Extreme (search) automatic systems are widely used, which ensure the maximum positive effect of the functioning of a technological object with minimum consumption of raw materials, energy, etc.

The set of technical means, with the help of which one or several controlled quantities without the participation of a human operator, are brought into line with their constant or changing according to a certain law set values ​​by developing an effect on the controlled values ​​as a result of comparing their actual values ​​with the set ones, is called an automatic control system ( ACP) or automatic control system. It follows from the definition that, in the general case, the following elements should be included in the simplest ACP:

control object (OU), characterized by an adjustable value x n. x (t);

a measuring device (IU) that measures the controlled value and converts it into a form convenient for further conversion or for remote transmission;

a setting device (ZU), in which the setpoint signal is set, which determines the setpoint or the law of variation of the controlled value;

a comparison device (CS), in which the actual value of the controlled variable x is compared with the prescribed value g (t) and,

a deviation is detected (g (t) - x (t));

a regulating device (RU), which, when a deviation (ε) arrives at its input, generates a regulating action that must be applied to the control object in order to eliminate the existing deviation of the controlled variable x from the prescribed value g (t);

executive mechanism (MI). At the outlet of the reactor plant, the control action has a small power and is issued in a form that is not generally suitable for direct action on the control object. Either an increase in the regulatory impact or transformation into a convenient form x p is required. For this, special actuators are used, which are the executive output devices of the regulating element;

regulatory body (RO). Actuators cannot directly affect the controlled variable. Therefore, the objects of regulation are supplied with special regulating bodies of RO, through which the IM acts on the regulated value;

communication lines through which signals are transmitted from element to element in an automatic system.

As an example, consider the enlarged block diagram of automatic control (Figure 1.1). In the diagram, the output parameters are the result of the operation of the controlled object, designated x 1, x 2, ……… x n. In addition to these basic parameters, the operation of automation objects is characterized by a number of auxiliary parameters (at 1, at 2, ……. At n), which must be monitored and regulated, for example, kept constant.

Figure 1.1. Block diagram of automatic control

In the process of operation, the control object receives disturbing influences f1…. fn, causing deviations of the parameters х1 …… .хn from their rational values. Information about the current values ​​of x tech and y tech enters the control system and is compared with their prescribed values ​​(setpoints) g1 …… gn, as a result of which the control system exerts control actions Е1… ..Еn on the object aimed at compensating for the deviations of the current output parameters from the set values.

According to the structure of the automatic control system, the automation object can be, in special cases, single-level centralized, single-level decentralized and multi-level. At the same time, single-level control systems are called systems in which the object is controlled from one control point or from several independent ones. Single-tier systems in which control is carried out from one control point are called centralized. Single-tier systems in which individual parts of a complex object are controlled from independent control points are called decentralized.

2.2 Functional - technological schemes automatic control

Functional-technological scheme is the main technical document that defines the functional-block structure of the devices of nodes and elements of the automatic control system, regulation of the technological process (operations) and control of its parameters, as well as equipping the control object with devices and automation equipment. Also, diagrams are often referred to simply as automation diagrams. The composition and implementation rules are dictated by the requirements of the standards (see Chapter 1).

The functional and technological scheme of automation is performed on one drawing, in which the symbols depict technological equipment, transport lines and pipelines, instrumentation and automation equipment with an indication of the connections between them. Auxiliary devices (power supplies, relays, circuit breakers, switches, fuses, etc.) are not shown on the diagrams.

Automation functional diagrams are associated with production technology and technological equipment, therefore, the diagram shows the location technological equipment simplified, not to scale, but taking into account the actual configuration.

In addition to technological equipment, on functional automation diagrams in accordance with standards, simplified (two-line) and conditionally (single-line) transport lines for various purposes are depicted.

Both the construction and the study of technical documentation schemes must be carried out in a certain sequence.

Process parameters that are subject to automatic control and regulation;

Functional management structure;

Control loops;

Availability of protection and alarm and adopted blocking mechanisms;

Organization of control and management points;

Technical means of automation, with the help of which the functions of monitoring, signaling, automatic regulation and control are solved.

For this, it is necessary to know the principles of constructing automatic control systems for technological control and conventional images of technological equipment, pipelines, instruments and automation equipment, functional links between individual devices and automation equipment and have an idea of ​​the nature of the technological process and the interaction of individual installations and units of technological equipment.

On a functional diagram, communication lines and pipelines are often shown in a single-line image. The designation of the transported medium can be either digital or alphanumeric. (For example: 1.1 or B1). The first number or letter indicates the type of the transported medium, and the subsequent number - its purpose. Digital or alphanumeric designations are presented on the shelves of leader lines or above the transport line (pipeline), and, if necessary, in the breaks of the transport lines (the adopted designations are explained in drawings or in text documents (see Table 1.1.). technological objects show those control and shut-off valves, technological devices that are directly involved in the control and management of the process, as well as selective (sensors), shut-off and regulating bodies necessary to determine the relative location of the sampling points (sensor installation points), as well as measurement or control parameters (see Table 1.2).

Complete devices (centralized control machines, control machines, semi-sets of telemechanics, etc.) are designated by a rectangle of arbitrary dimensions with an indication of the type of device inside the rectangle (according to the manufacturer's documentation).

V individual cases some elements of technological equipment are also shown in the diagrams in the form of rectangles, indicating the names of these elements. At the same time, near the sensors, selective, receiving and other devices similar in purpose, indicate the name of the technological equipment to which they belong.

Table 1.1. Designation of transport lines of pipelines according to GOST 14.202 - 69

Table 1.2. Symbols of process valves

Name	Designation according to GOST 14.202 - 69
Shut-off straight-through valve (gate valve)
Electrically operated valve
Three-way valve
safety valve
Rotary shutter (damper, gate)
Diaphragm actuator
Table 1.3. Output electrical switching elements
Name	Designation according to GOST 2.755 - 87
Contact for switching a high-current circuit (contactor contact)
Closing contact
NC contact

To make it easier to read the diagrams on pipelines and other transport lines, arrows are put down indicating the direction of movement of the substance.

In the functional and technological scheme, as well as at the image of the pipeline through which the substance leaves this system, a corresponding inscription is made, for example: "From the absorption shop", "From pumps", "To the polymerization scheme".

Figure 1.2. Image of sensors and selected devices (fragment)

Conventional graphic designations of automation tools are given in tables 1.2., 1.3., 1.4 .. Conventional graphic designations of electrical equipment used in functional automation diagrams should be depicted in accordance with the standards (Table 1.3.). In the absence of standard symbols for any automatic devices, you should accept your symbols and explain them with an inscription on the diagram. The thickness of the lines of these designations should be 0.5 - 0.6 mm, except for the horizontal dividing line in the conventional image of the device installed on the shield, the thickness of which is 0.2 - 0.3 mm.

The sampling device for all permanently connected devices does not have a special designation, but is a thin solid line connecting the process pipeline or apparatus with the device (Fig. 1.2. Devices 2 and 3a). If it is necessary to indicate the exact location of the sampling device or the measuring point (inside the graphic designation of the technological device), at the end, a circle with a diameter of 2 mm is shown in bold (Fig. 1.2 devices 1 and 4a).

Table 2.4. Conventional graphic symbols of automation equipment and devices

Name	Designation according to GOST 21.404 - 85
Primary measuring transducer (sensor) or device installed on site (on a technological line, apparatus, wall, floor, column, metal structure). Basic Allowed
Panel-mounted device, remote control Basic Permissible
Selection device without permanent connection of the device
Actuating mechanism
Travel switch
Electric bell, siren, beep
Electric heater: a) resistance, c) induction
Recording device
Incandescent lamp, gas discharge (signal)
Three-phase electric machine (M - engine, G - generator)
Electric DC machine (engine M, generator G)

To obtain a complete (freely readable) designation of a device or other automation tool, a letter symbol is entered into its conventional graphic image in the form of a circle or oval, which determines the purpose, functions performed, characteristics and operating parameters. In this case, the location of the letter determines its meaning. Thus, the letters given in Table 1.5 are the main parameters and functions, and the letters given in Table 1.6 specify the function, the parameter.

Table 1.5. Designation of the main measured parameters in automation schemes

To designate manual control, use the letter H. To designate values ​​that are not provided for by the standard, reserve letters can be used: A, B, C, I, N, O, Y, Z (the letter X is not recommended). The used spare letters must be deciphered by an inscription on the free field of the scheme.

Below are the designations of the clarifying values ​​of the measured values.

Table 1.6. Additional letter symbols

The letter that serves to clarify the measured value is placed after the letter denoting the measured value, for example P, D, - the pressure difference (differential).

The functions performed by the devices for displaying information are denoted by Latin letters (see table 2.7).

Table 1.7. Function letters

Additionally, designations with the letters E, G, V can be used.

All of the above letter designations are affixed to the upper part of the circle denoting the device (device).

If several letters are used to designate one device, then the order of their arrangement after the first, denoting the measured value, should be, for example: TIR - a device for measuring and recording temperature, PR - a device for recording pressure.

When designating devices made in the form of separate blocks and intended for manual operations, the letter H is put in the first place.

For example, in Fig. 1.2 shows an automation diagram using recording devices for temperature and pressure difference, where, to form the symbol of the device (set), in the upper part of the circle indicate the functional purpose, and in the lower part of the circle place its reference designation (alphanumeric or digital - 1, 2, 4a, 4b, 3a, 3b). Thus, all elements of one set, i.e. one functional group of devices (primary, intermediate and transmitting measuring transducers, measuring device, regulating device, actuator, regulating body) are designated by the same number. In this case, the number 1 is assigned to the first (left) set, the number 2 to the second, etc.

To distinguish the elements of one set, an alphabetic index is placed next to the number (the letters Z and O, the outline of which is similar to the outline of the numbers, is not recommended): for the primary transducer (sensing element) - index "a", for the transmitting transducer - "b" , at the measuring device - "in", etc. Thus, for one set, the full designation of the primary measuring transducer will be 1a, the transmitting measuring transducer 1b, the measuring (secondary) device 1c, etc. the height of the figure is 3.5 mm, the height of the letter is 2.5 mm.

According to the requirements for the functioning greenhouse facilities with convection heat exchange and an irrigation system, the automation scheme for the technological process of growing agricultural products in stationary block greenhouses can be represented in the form of a functional automation scheme shown in Fig. 3.1.

On the automation diagram (see Fig. 3.1), the following designations are adopted:

• 1 - Electric supply ventilation damper;
• 2 - Circulating fan;
• 3 - heating element;
• 4 - Electric exhaust ventilation damper;
• 5 - Solenoid valve of the irrigation circuit;
• 6 - Nozzles of the irrigation system (watering);
• 7 - Sensor for opening doors (or windows);
• 8, 9 - Soil moisture sensor;
• 10 - Air humidity and temperature meter.

On the basis of the developed automation scheme, it is advisable to design the architecture of the control system according to a three-level scheme. At the first (lower) level, the collection of technological information from the measuring transducers and the control of the actuators and relay automatics installed in the place are provided. The signals from the temperature and humidity measuring transducers are processed by a programmable logic controller (PLC).

On the basis of the developed automation scheme, it is advisable to design the architecture of the control system according to a three-level scheme. At the first (lower) level, the collection of technological information from the measuring transducers and the control of the actuators and relay automatics installed in the place are provided. The signals from the temperature and humidity measuring transducers are processed by the PLC. According to the given algorithm for controlling the microclimate mode, it generates control signals to the actuators of the control loops. The second level provides program control for a given technological process of growing agricultural crops from the operator's station. The software system automatically checks and controls the temperature, humidity level in the chamber and on the ground surface using sensors and a heating pipe valve, as well as a humidification system. The equipment of this level includes the control panel and PLC installed in the control room. The industrial computer is connected by a Profibus DP network with distributed equipment and is connected to the local segment of the greenhouse economy via Ethernet at the third level.

At the third (upper) level, centralized processing of information about the technological process is carried out at the enterprise via the Ethernet network. Information processing includes monitoring the progress of the technological process, the flow rate of the coolant, logging, archiving and operational control.

The block diagram of the automated control system for the technological process of regulating the climate inside the greenhouse environment is shown in Fig. 3.2.

Figure 3.1 -Automated greenhouse microclimate control system

Figure 3.2 - Block diagram of the ACS MKT

The development of automated process control systems at the present stage is associated with the widespread use of microprocessors and microcomputers for control, the cost of which becomes lower every year in comparison with the total costs of creating control systems. Before the advent of microprocessors, the evolution of process control systems was accompanied by an increase in the degree of centralization. However, the capabilities of centralized systems are now already limited and do not meet modern requirements for reliability, flexibility, cost of communication systems and software.

The transition from centralized control systems to decentralized ones is also caused by an increase in the power of individual technological units, their complication, increased requirements for speed and accuracy for their operation. The centralization of control systems is economically justified with a relatively small information capacity (the number of control and regulation channels) of the TOU and its territorial concentration. With a large number of control, regulation and control channels, a large length of communication lines in the APCS, the decentralization of the control system structure becomes a fundamental method of increasing the survivability of the APCS, reducing the cost and operating costs.

The most promising direction of decentralization of APCS should be recognized automated control processes with a distributed architecture, based on the functional-target and topological decentralization of the control object.

Functional and targeted decentralization- This is the division of a complex process or system into smaller parts - subprocesses or subsystems according to a functional characteristic (for example, redistribution of a technological process, modes of operation of units, etc.), which have independent goals of functioning.

Topological decentralization means the possibility of territorial (spatial) division of the process into functional-target sub-processes. With optimal topological decentralization, the number of distributed APCS subsystems is chosen so as to minimize the total length of communication lines, which together with local control subsystems form a network structure.

The technical basis of modern distributed control systems, which made it possible to implement such systems, are microprocessors and microprocessor systems.

The microprocessor system performs the functions of data collection, regulation and control, visualization of all information in the database, changing settings, parameters of algorithms and the algorithms themselves, optimization, etc. The use of microprocessors (including microcomputers) for solving the listed tasks makes it possible to achieve the following goals:

a) replace analogue technology with digital where the transition to digital means improves accuracy, expands functionality and increases the flexibility of control systems;

b) replace hardware with rigid logic with programmable (with the ability to change the program) devices, or microcontrollers;

c) replace one mini-computer with a system of several microcomputers when it is necessary to provide decentralized control of production or technological process with increased reliability and survivability, or when the capabilities of the mini-computer are not fully used.

Microprocessor systems can perform in the subsystems of a distributed APCS all the typical functions of monitoring, measuring, regulating, controlling, and presenting information to the operator.

In distributed process control systems, three topological structures of interaction of subsystems are generally accepted: star-shaped (radial); ring (loop); bus (trunk) or combinations thereof. Organization of communication with sensors and actuators is individual and predominantly radial.

Figure 3.5 shows the topology options for distributed process control systems.

Figure 3.5 - Typical structures of distributed APCS:

a - radial, b - main line, c - annular

The radial structure of the interaction of subsystems (Figure 3.5, a) reflects the traditionally used method of connecting devices with dedicated communication lines and is characterized by the following features:

a) there are separate, unconnected lines connecting the central subsystem (CPU) with the local automation systems of the aircraft i;

b) it is technically easy to implement interface devices US 1-US m of local automation. The central communication device USC is a set of modules of the US i type according to the number of lines or a rather complex device for multiplexing information transmission channels;

c) the maximum exchange rates on individual lines are provided with a sufficiently high performance of computing devices at the CPU level;

d) the reliability of the communication subsystem largely depends on the reliability and survivability of the CPU hardware. Failure of the CPU practically destroys the exchange subsystem, since all information flows are closed through the upper level.

A distributed system with a radial structure is a two-level system, where at the lower level in the subsystems the necessary control, regulation, and control functions are implemented, and at the second level, in the central processor, a coordinating microcomputer (or mini-computer), in addition to coordinating the work of microcomputers-satellites, optimizes the control tasks of the TOC, energy distribution, controls the technological process as a whole, calculates technical and economic indicators, etc. The entire database in a distributed system with a radial structure must be accessible by the coordinating microcomputer for control applications at the upper level. As a consequence, the coordinating microcomputer operates in real time and must be controlled using high-level languages.

Figure 3.5 (b, c) shows the ring and bus topologies of level interaction. These structures have a number of advantages over radial ones:

a) the operability of the communication subsystem, which includes the channel and communication devices, does not depend on the operability of the technical means at the automation levels;

b) it is possible to connect additional devices and control the entire subsystem using special tools;

c) significantly lower costs of cable products are required.

Due to the exchange of information between the aircraft i through the communication channel and the US ("each with each"), there is an additional possibility of dynamic redistribution of the coordination functions of the joint operation of aircraft subsystems on the lower levels in the event of a CPU failure. The bus (to a lesser extent, ring) structure provides a broadcast mode of exchange between subsystems, which is an important advantage when implementing group control commands. At the same time, the bus and ring architectures are already placing significantly higher demands on the "intelligence" of the interface devices, and, consequently, increased one-time costs for the implementation of the core network.

Comparing the ring and bus topologies of the communication subsystem, it should be noted that the organization of the ring structure is less expensive than the bus one. However, the reliability of the entire subsystem with a ring communication system is determined by the reliability of each interface device and each section of communication lines. To increase survivability, it is necessary to use double rings or additional communication lines with bypass routes. The performance of the physical transmission channel for a transformer-decoupled bus architecture does not depend on the serviceability of the interface devices, however, as for the ring, the failure of any interface device in the worst case leads to a complete autonomous work the failed node of the subsystem, i.e., to the loss of control function from the CPU level by the automation of the failed node.

An explicit method of increasing the survivability of the entire automation system in the event of a failure of the matching devices in the communication subsystem is to duplicate the matching devices in the nodes of the subsystem. In a ring structure, this approach is already implied when organizing double rings and detours. If the reliability of the continuous physical channel for the lower topology is not in doubt, then only the interface devices can be duplicated without the use of a redundant trunk cable.

A cheaper way to improve the reliability of the communication subsystem is to use combined structures that combine the advantages of radial and ring (trunk) topologies. For a ring, the number of radial bonds can be limited to two or three lines, the implementation of which provides a simple and inexpensive solution.

Assessment of such indicators of distributed process control systems, such as economic(costs for cable products, cable tracing, development or purchase of network facilities, including communication devices, etc.), functional(the use of group transfer operations, the exchange rate, the ability to exchange "each with each"), as well as indicators of unification and possibilities of evolution networks (the possibility of simple inclusion of additional subscriber nodes, tendencies to use in APCS) and indicators network reliability(failure of the communication channel and communication or interface devices), allows us to draw the following conclusions:

a) the most promising in terms of development and use is the backbone organization of the communication subsystem;

b) the functionality of the backbone topology is not inferior to the capabilities of the ring and radial;

c) the reliability indicators of the backbone structure are quite satisfactory;

d) the backbone topology of a distributed APCS requires large one-time costs for the creation and implementation of a communication channel and interface devices.

Largely due to these features of the backbone structure and modular organization of hardware and software in modern process control systems trunk-modular principle constructing technical support found preferential distribution.

The use of microprocessors and microcomputers makes it possible to effectively and economically implement the principle of functional and topological decentralization of the APCS. Thus, it is possible to significantly increase the reliability and survivability of the system, reduce expensive communication lines, ensure the flexibility of operation and expand the field of application in the national economy of complexes of technical means, the main element of which is a microcomputer or microprocessor. In such distributed control systems, it becomes very important interface standardization, i.e. the establishment and application of uniform norms, requirements and rules that guarantee the informational integration of technical means in the standard structures of the APCS.