Control Computer

a computer functioning in the control circuit of a process, machine, or system. Control computers receive and process information in the control process and generate control information in the form of text, tables, or graphics printed on paper or displayed on a screen or in the form of signals fed to the actuating mechanisms of the controlled object.

Control computers are primarily designed to ensure the optimum functioning of the controlled object. Control with the aid of such a computer is based on a mathematical description of the behavior of objects (seeALGORITHMIC DESCRIPTION OF PROCESSES and MATHEMATICAL MODEL). Control computers feature all the basic components found in any computer, such as a processor and a memory; in addition, they are equipped with devices for interfacing with the controlled object. These devices feed data to the processor that have been received from the sensors that measure quantities characterizing the state of the controlled object; they also provide for the output of control signals to the actuating mechanisms and for various signal and conversion devices.

Control computers may be general-purpose or special-purpose types. The latter are designed to perform tasks in systems that control a small, previously defined set of objects or processes. General-purpose control computers have technical parameters and capabilities that enable them to be used in virtually any control system.

Depending on the data presentation form, control computers may be classified as digital, analogue, or hybrid (digital-analogue) types. Digital control computers are superior to analogue computers in accuracy of control, but they are inferior in speed of action. In hybrid control computers, digital and analogue computing devices function in combination, which allows maximum use of the advantages of each.

Control computers are the central link in automatic control systems. They process information on current values of and changes in physical quantities characterizing the controlled object, and they produce control signals that ensure operation in the specified regime. In some automated production control systems, the control computer typically functions in the capacity of a consultant, providing the human operator with information on the state of the controlled object and recommendations for the optimization of the control process or, less often, it may provide direct control. Control computers may also be classified according to purpose or field of use, such as general industry, the aerospace industry, or transportation.

The use of control computers began in the early 1950’s with the development of onboard computers for military aviation. One of the first onboard control computers—Digitac (USA, 1952)—was designed to provide automatic control of the flight and landing of an airplane and to perform navigation and bombing tasks. Containing approximately 260 subminiature vacuum tubes and 1,300 semiconductor diodes, it had a volume of 150 cubic decimeters and a weight of 150 kg. The first transistorized onboard control computers were developed in the mid-1950’s, and integrated microcircuits were first used in the early 1960’s, several models of which possessed relatively high processing capabilities. An example of the latter type was the Univac 1824 (USA, 1963), which consisted of an arithmetic-logic unit, a memory unit, a data input-output block, and a power supply. The Univac 1824 had a volume of 4.1 cubic decimeters, a weight of 7 kg, and a power rating of 53 watts, with no cooling or ventilation system required. The computer contained 1,243 integrated microcircuits.

In the early 1960’s control computers were used in systems to control continuous technological processes, for example, the RW 300 control computer (USA), which was used to control technological processes in the production of ammonia. In such control systems, the signals generated by the computer were converted from digital to analogue form and were fed to the control inputs of the actuating mechanisms as electrical signals. Direct digital, or numerical, control of continuous technological processes was first applied in 1962 in the USSR (in the Avtooperator system at the Lisichansk Chemical Combine) and in Great Britain (in the Argus-221 control system at the soda plant in the city of Fleet-wood). The Dnepr, Dnepr-2, VNIIEM-1, VNIIEM-3, UM-INKh, and other computers were developed in the USSR in the 1960’s for the control of continuous technological processes.

In the mid-1960’s the production of one-off models of control computers shifted to the production of integrated systems, or complexes. Such systems consist of a set of computing devices, means of communication between the human operator and the control system, interfacing devices linking the computer to the controlled object, and means of internal and external communication. An example of such a control computer complex is the model M-6000, part’of the aggregated system of computer technology devices (ASVT) developed in the USSR (in series production since 1969). The ASVT consists of a range of modules from which control systems of various designs may be constructed. Computer complexes are designed for the collection and primary processing of data in the control of various technological processes, scientific experiments, and the like. The M-6000 control computer consists of a general-purpose digital processor, data input-output devices, aggregate modules for the input and output of analogue and digital signals, and aggregate modules for the organization of internal communications and communications with other systems.

Industrial enterprises use the ASVT to construct multilevel automated control systems. Relatively simple control computers are used at the lowest level of such a system, such as the model M-6010 microprogram control device and the model M-40 machine for centralized control; they provide direct control of a production process. At the middle level, such control computers as the M-6000 and M-400 handle more difficult control tasks, such as those connected with the optimization of a group of production processes. These control computers are connected in turn with the system’s central link, which controls the operation of the entire system, including production accounting, and planning. Larger control computers are usually used at this level, for example, the models M-4030 and M-7000.

An important trend in the development of control computers is the integration of functional modules in order to satisfy the need for uniform input and output parameters, standardized information links between modules, and standardized software. Under these circumstances it becomes feasible to assemble various computing systems to meet the requirements of individual customers. Such requirements are partially met by the Hewlett-Packard-9600 (USA) computing system, designed for various measurements and automatic control. The heart of the system is a functionally unified module consisting of a microprogram processor integrated with other functional modules.

Special control systems are used for the centralized automatic control of widely separated groups of objects; they include a data-processing center, equipped with a high-capacity computer, and central and peripheral control systems interconnected by standardized communications systems. The use of a high-capacity computer in the data-processing center allows the processing of information arriving from central control systems, which operate in real time, as well as the remote entry of tasks into the central control systems. The latter are connected with the data-processing center and with the peripheral systems directly controlling the objects.

Much attention is currently being focused on increasing the operational reliability of control computers while simultaneously reducing the cost, weight, and size. Efforts are also being made to increase the reliability of the means used to obtain, convert, and transmit information.