From Big Medical Encyclopedia

CONTROL SYSTEM — functionally organized dynamic system (technical, social, biological etc.), in a cut the management processes providing achievement of goals are carried out. In the structural relation of S. at. it is subdivided into two parts — managing and managed (see. Management ). A managing part is called the actuation device, and managed — object of management. If management processes in technical system are made without participation of the person, it is called an automatic control system, and with the assistance of the person — automated control system (see). Sometimes in rather simple technical systems the private purpose of management consisting in automatic maintenance on a fixed level of any characteristics (signals, variables) in object of management is considered. In this case speak about system of automatic control. Such system consists of regulators and an adjustable object. For designation of nek-ry types of systems, including biological, often instead of the term «control system» use the term «system of regulation» (see. Regulation, in biological systems ).

In the actuation device C. at. special signals form — i.e. managing influences, to-rye arrive on entrances of an object of management and change its state in the necessary direction. These signals create so-called feedforwards. Managing influences in S. at. can be developed as on the basis of information on a condition of external objects (in relation to object of management), and on the basis of information on a current status of the object of management arriving on channels feed-back (see). Page at., the managements functioning without information on a current status of an object, i.e. without a feed-back, are called opened, and functioning in the presence of such information — closed.

Difficult S. at. usually have the hierarchical organization with a set of the coordinated levels. At each level the mechanisms of management forming in S. at function. complete system of straight lines and feed-backs. Therefore difficult S. at. sometimes are called multicoherent.

For the description of functioning of S. at. in to cybernetics (see) concepts of stability, sensitivity and quality of system are used.

Stability in a broad sense is understood as property C. at. to be returned from the indignant states in initial or close to initial the set mode after the external indignation which caused a deviation ceases to work (acts). Page at. it is unstable if after removal of indignation it is not capable to revert to the original state.

S.'s sensitivity at. characterizes extent of change of its mode under the influence of permanent indignation. When at constant action of any indignation the arising mode differs from initial a little, say that the control system has small sensitivity.

S.'s quality at. (i.e. degree of compliance of this S. at. to the tasks which are carried out by it) it is estimated on the basis of the criteria elaborated in advance. The system, management processes in a cut provide achievement of the best (limit, maximum or minimum) values of indicators, is called optimum. E.g., technical S. at., realizing the most bystry achievement of a goal, are called optimum on speed.

Often in the course of S.'s functioning at. nek-ry parameters of the actuation device at change of conditions of the environment automatically change for the purpose of improvement of quality of management. Such S. at. are called adaptive; adaptive control systems are capable to support an optimality of system in the conditions of the changing environment.

In the theory of automatic control a problem of designing of S. at. the problem of studying of real S. is called meeting the set requirements of stability and quality a problem of synthesis, and at. and obtaining its quantitative characteristics — a task of the analysis. At the solution of these tasks various are used mathematical methods (see).

For a long time a task of the analysis of S. at. decided by means of a so-called method of a black box when S.'s functioning at. it was described by means of the ratios connecting among themselves directly entrances and S.'s exits at. After limitation of this method suitable only for the description and a research of rather simple systems was found out, began to use a method of space of states. In this method exits of system do not contact directly its entrances, and at first for the set structure the condition of system, i.e. the minimum set of numbers is determined by entrance signals, to-ry allows at a task of future entrances of system always to define values of all its future exits. Mathematically S. at. describe two systems of the equations. The first, S. describing a state at., includes only the differential equations (the so-called equation of a state), and the second — only the algebraic equations giving the chance on the current values of entrances and states to define all exits (the equation of exits).

S., various by the nature, at. have a big variety of properties. In particular, for biol. systems (see. Biological system ) hierarchical structures of evolutionarily developed mechanisms of management are characteristic. The exchange processes which are the cornerstone of life activity are regulated by biochemical mechanisms of management of a metabolic sistekhma of an organism; processes of supply with substances and energy — mechanisms of management fiziol. level; processes of self-reproduction, growth and ontogenesis — genetic mechanisms of management.

The tendency to difficult S.' creation was outlined at., in to-rykh at the same time work as technical, and biol. control elements. In person — the car systems (see) biol. characteristics of the person operator are designed to provide the best functioning of a machine component C. at. In engineering and physiological S. at., napr, in systems life support (see), during the use artificial organs (see), interaction technical and fiziol. mechanisms of management it is aimed at providing the best functioning biol. a component of system — i.e. a human body.

See also System , Systems analysis , Management .

Bibliography: Winer N. Cybernetics, the lane with English, M., 1968; Novoseltsev V. N. Theory of management and biosystem, Analysis of sokhranitelny properties, M., 1978.

V. N. Novoseltsev.