SU1386957A1 - Self-adjusting combined control system - Google Patents

Abstract

The invention relates to the field of automatic control systems and can be used to control objects in the chemical and other sectors of the invention. The purpose of the invention is to improve the accuracy of the system under conditions of a nonstationary static characteristic of the control object and a high level of disturbances of considerable intensity acting on it. The system contains an error meter 1, a controller 2, multiplication blocks 3 and 24, adders 4 and 9, a control object 5, a self-tuning block 6, a correction filter 7, an external disturbance sensor 8. The system is built on the basis of the combined principle and includes open and closed control loops, an open loop self-tuning unit and a circuit for stabilizing the transfer ratio of the open-loop system. An open loop, including blocks 8, 7, 4 and 5, is designed to compensate for controlled disturbances. The self-tuning unit 6 improves the quality of the open loop operation under the conditions of non-stationarity of the static characteristic of the object. The chain of stabilization of the transmission ratio of an open-loop system, including blocks 8, 9, 7, 3, and 24, improves the quality of operation of the closed control loop with constant settings of the controller and control of the non-stationary object according to the static characteristic. 5 il. Sfi (L with s 00 O5 with SP

Description

The invention relates to automatic control systems and can be used to control objects in the chemical and other industrial sectors.

The purpose of the invention is to improve the accuracy of the system under the conditions of a non-stationary control object and a high level of disturbances acting on it.

FIG. 1 is a block diagram of the proposed self-adjusting combined control system in FIG. 2 is a block diagram of the system; in FIG. 3 is a block diagram of the implementation of the logical blocks of the system of FIG. 4 - schematic diagram of the pneumatic B-controller; Figure 5 is an electrical PID controller circuit.

The system includes an error meter 1, a regulator 2, a block 3 more, Less - a button for selecting the sign

0

five

0

UjCt) - open loop output signal; x, (t) is the main controlled disturbance, x (t) is the input of the object through the control channel y (t) is the output of the control object}) is the output signal of the memory block; (i) the output signal of the third block of the lazy module i b.y, (t) is the output signal of the first block of the selection module, byj, (t.) is the output signal of the second block of the block module; uy, (t) is the output signal of the fourth module of the selection module; Р - signal proportional to the current value of the adjustable parameter; RK command signal, - ДД - adjustable choke di - adjustable choke, Pgtix - output signal of the regulatorJ П - external switch of the type of work; R, A - Manual mode of operation of the controller, Automatic, Pain

scissor, adder 4, control object 5, self-tuning unit 6, correction filter 7, external disturbance sensor 8, adder 9, multiplication unit 10, module allocation unit 11, differentiation unit 12, module selection 13, differentiation unit 15, selection block 15 module, logical blocks 17-19, module allocation block 20, division block 21, controllable key 22, memory block 23 and multiplication unit 24.

The block diagram of the implementation of the logical blocks of the system includes a comparator 25, a control key 26, a comparator 27, a control key 28, a comparator 29, a control key 30, a comparator 31 and a control key 32.

The schematic diagram of the pneumatic PI controller includes a comparison element 33, a throttle adder 34, a comparison element 35, a power amplifier 36, a comparison element 37, a capacity 38, a shut-off valve 39, and a tripping relay 40,

FIG. 1-5, the following notation is accepted: g (t) - specifying effect; (t) is the deviation of the output signal of the object from the task; C is the control signal; Cj, - the task for the first logical block C, - the task for the second logical block Cj - the task for the third logical block- C 5 - the task for the fourth logical block; U, (t) is the output of the second multiplication unit; Ur, d (t) - output signal of the third block yj.i: -: o

 increments of the output signal in the manual control mode; U is the voltage of the internal power source; Р (J 2. РЭ windings and relay contacts; Rp, Ср - resistor and capacitor of the manual control integrator -, + Ug; -UM - reference voltage J MCD - drift compensation module, D (- two-anode zener diode; A , -A - operational integrated amplifiers; Ru - high-resistance variable resistor of the integrator; Sc - capacitor of the integrator; IC - output signal of the integrator (I-component); K - total proportionality factor of the regulator,

oa; and

peed

- total signal P. I. D

constituents of the law of regulation; Rffls Сф - resistor and capacity of aperiodic link (filter); U - controller output limiter}

and

ogre

- output signal limiter;

-and,

five

0

five

D, D, - diodes; - and „4, - and 64 — signals for limiting the output of the manual control integrator at the lower and upper levels; - the signal of the mismatch of the given and current values of the parameter} K, - electronic analog key.

I

Closed loop control

contains series-connected blocks 1-5, covered by negative feedback.

An open control loop includes series-connected blocks of 8, 7, 4, and 5. The control signals 1 and the closed and open circuits are respectively signal 31

ly Vt (t) and). An open loop self-tuning block contains blocks 11–20. Stabilization circuits of an open-loop transmission transmission system include blocks 8, 9, 7, 3, and 24.

The system solves the problem of controlling a non-stationary object, which in general can be described by the equation

|: a.) + y (t) K, (t)

+ djt) f, (t),

de a ;, K (t), dp (t) - object parameters

that control j y (t) is adjustable

value;

x (t) is the input signal of the object (control action);

XI (t) - the main external controlled disturbance (disturbance on the load) j

f (t) is the external uncontrolled disturbance.

The following types of non-stationary objects are considered.

TO,". d

waicc

(2)

Equations (1) and (2) describe the motion of objects that are nonstationary in statistical characteristics. The control task is to reduce the regulation error to a given value.

iy (t) g (t) -y (t)

| by (t) S,

where o, is some given positive value.

The system works as follows.

Consider the consistent operation of the system circuits. An open loop forms a control signal proportional to the magnitude of the main external disturbance, (t). For this c. block 21, a signal is generated of the ratio of quantities proportional to the input variables, which, through control

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The user key 22 enters memory block 23. The signals arriving at the first and second inputs of the divider 21 are proportionally applied in practice (as applied, for example, to the field of chemical technology) to dosages of the reagent and the raw material, respectively. Therefore, the signal ratio entering the unit

1Q 23 of memory, in proportion to the ratio of the dosages of the reagent and raw materials. The input signal of dividing unit 21 in memory unit 23 is recorded only when the unit 6 of the self-control unit -J5 makes a control signal C to open the key 22. The output signal K | j, (t) of the memory unit 23 arrives in multiplication unit 24, in which the for-. Open loop output (U) (t) is measured.

Thus, the output signal of the sensor 8 is multiplied in block 7 by a certain amount (the transfer coefficient of block 7), which, between the interventions of the self-tuning corrective

filter 7 is a constant value and is stored in memory block 23. When block 7 is self-tuning, its transmission coefficient changes abruptly 3Q figuratively, since

The state of the object quasi-statistics, the new ratio of the input signals of the divider 21, proportional to the current ratio of the dosages of the reagent and the raw materials, is passed through the key 22 and stored in the memory block 23. During the operation of the system, all changes in the value of x, (t) in a certain ratio, equal to the transfer coefficient of block 7, are tracked by the value U2 (t). Thus, the correction filter 7 is a proportional link with a variable transmission coefficient, which has a slice of 40

45

but constant character.

Block 6 self-tuning works as follows (Fig. 2).

Block 16 is used to determine the moment of self-tuning. In blocks 17-19, the conditions of the quasistatics of the control object are checked. The operations performed in blocks 16-19 are described respectively by formulas (3) - (6).

| U, (t) | / & y (t) /

 s

(3) (4)

(five)

dt

.c,

(6)

The signal U, (t) represents the response of the closed loop of the system to the action of all types of disturbances that change the output of the object. If the modulus of the specified value obtained in block 20 exceeds a certain specified GO value (formula (3)) and the object is in the state of quasistatics, i.e. the conditions (formulas (4) - (6)) are satisfied, then the control signal C passes the first 16, second 17, third T8 and fourth 19 logic blocks and arrives at the control input of the key 22. At the same time, the signal C enters through the second input to controller 2, where the integral component of the signal U, (t) is zeroed. Let controller 2 implement the PID control law, then

and, (t) B, uy (t) + B ,, | uy (e) (t) 1

+ B,

where in(,

dt b

J

K (t)

g

KB adjustable controller settings. As a result of the act of self-adjustment of the correction filter 7, the value of U (t) is determined by the formula

U, (t) B, y (t) + B, fAlltj K (t) (8)

The transition of the control system to a new value of the transfer coefficient of the correction filter does not cause disturbance of the input signal x (t) of object 5. Indeed, when the conditions checked in blocks 16-19 of the system are fulfilled, signal C opens key 22, resulting in signal x (t ) after subtracting from it in the adder 9 the value of and d (t), passes the division block 21, the key 22, is recorded in the memory block 23, passes the multiplication block 24 and as a signal U (t) goes to the second input of the first adder 4 The operation of zeroing the I-component causes the condition the test in the first logic block 16 is not executed, as a result of which C 1: drive C does not pass logical blocks 16-19 and the control key 22 is closed. Thus, in block 23 Ps1m ty a new value of the transfer coefficient of the correction filter 7 is written. At the same time, the first output

the signal of regulator 2 is reduced, and the output signal of the open circuit is increased by the value of the I-component from the output of the regulator, which took place in the output of the regulator before the self-tuning.

The second output of regulator 2 is determined by expression (8), i.e. It represents the PD component of the signal U, (t) multiplied by the value of K (s). Signal (t) is subtracted in adder 9 from signal x (t). This eliminates the double summation of the PD component

15 of the output of the controller 2 in the adder 4 and, therefore, the disturbance of the input object.

The circuit connecting the second output of the regulator 2 to the second input of the adder

20 9, it allows to increase the System Operational Accuracy by eliminating disturbance of the object's input upon adaptation of filter 7, when the PD component of U, (t) is different from zero. With

25 the further operation of the system, the value (7) U, (t), as the reaction of the closed loop of the system to the deviation y (t) from the task, varies. When the module of the specified signal is given &

Q value C, an analysis is made of the conditions for the quasistatics of the control object. When a quasistatic state of the object occurs, the following filter adaptation action 7 is performed.

Co, C, C, C values are a priori adjustable parameters of block 6. Changing the output of controller 2 over time characterizes the change in the dynamic characteristics of the control channel and / or the external conditions of the system. The magnitude of the signal modulus u, (t) in the state of object 5 quasistatics characterizes the degree of mismatch of the control signal x (s) to the value of the main controlled disturbance x, (t) in the current conditions of the system operation. The act of self-tuning filter 7 increases the quality of compensation at the input of the perturbation object X | (t) and, consequently, the quality of the entire system as a whole, since the part of the perturbations that previously passed through the object increased the variance of the output parameter

55 and loaded feedback will be compensated at the input.

Open-loop stabilization circuits include

35

40

45

50

71

blocks 8, 9, 21-24, and 3, and their corresponding connections. The task of stabilizing the transmission coefficient of an open-loop system is considered as part of the problem formulated above (formulas (1) and (2)). Let) be the statistical characteristic of the control object 5 (non-stationary transfer coefficient), Kp of the transfer coefficient of the controller 2, Kpc (t) is the transfer coefficient of the open system. Multiplication unit 3 is represented as an amplifier, the variable gain of which replaces the second input signal of the block 3. The stabilization problem Kp (t) can be formulated

 K / mime - KMCTK.C}

Kpg ,. const,

TO

K, 6 Kp (t) K.

pc (t) Kp ,, - K (t) -K, (t),

It is required to provide,, where K, are the limiting values of the value (t), Yu, K, are the limit values of the specific value Kpc (t) j 0 - some given positive number.

- The self-tuning circuits of the K value used in the system make it possible to solve this problem.

Let t; . (, 2, ..., p) are the moments of the quasistatics of the control object. For the moment t;

KpK (t;) K ,, (t;). K (t, -),

where Kp | (t;) is the transfer coefficient of the open loop system. For time t,

K (t.4,) K, (t;). E .;

where Γ, is some quantity. Then

Kp, (t; ,,) K, (t;). C, -K (t, 4,).

As a result of the self-tuning of the filter transfer coefficient 7

,four,

one

those. within a certain permissible error, the system by means of block 6 ensures the constancy of the coefficient

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open loop transmission.

Therefore, 5 Kpjtu,) Kp, (t;).

For an open system at time tj (in the absence of block 3)

Kpc (t;) Kp ,,. K (t,) For the moment t ;; Kp (t; ..) Kp.K; (t;), e,

Comparing the last two expressions, taking into account the above expression for K., (T, -.,), It follows that in order to stabilize the value of K (t), it is sufficient to multiply it by the value of K (p (t).) 3 (Fig. 2) can be written for

20

Kpjt;) Kp ,, - K (t;) - K ,, ()

where (t; i.), for the moment t, vi (within the limits of allowable error of self-tuning)

Kpc (4.,) - K; ,,. K () r,

those. Krs (t, 4,) (i: Kp (t;). Thus, the use of these self-tuning circuits allows us to solve the problem of stabilizing the Kpc (t) value formulated above.

The third multiplication unit 24 (FIG. 2) is designed to ensure that the PD components of the output signal of the controller are equal when they are mutually compensated in cy matte 9.

Claims (1)

Invention Formula Self-tuning with a com- system. Binated control, containing the error meter, the first input of which is connected to the system input, the controller, the first and second adders, the control object, the self-tuning unit, the external disturbance sensor, the division unit, the control key, the memory unit, the first and second multiplication units, the output of the second multiplication unit is connected to the first input of the first adder, the output of which is connected to the first input of the second adder connected by an output to the input of a divisible division unit, the output of which is connected to the information input of a control key connected to the output through a memory block to the first the input of the second multiplication unit, the second input of which is connected to the input of the divider of the division unit and to the output of the external disturbance sensor, the output of the control object is connected to the output of the system and to the second input The mismatch connected by the output To the first input of the self-tuning unit and to the information input of the controller, the control input of which is connected to the control input of the controlled key and to the output of the self-tuning unit, in order to improve the accuracy the system under the conditions of an unsteady control object with a high level of disturbances acting on it, a third multiplication unit is additionally inserted into it, connected by an output to the second input of the second adder, the first input of the second multiplying unit ene with first inputs of first and third multipliers, the second inputs of blocks which are respectively connected to first and second outputs of the regulator, a first multiplication block connected to the second output in the course of the self-tuning unit and to the second input of the adder rtepBo- connected to the input output control object. ABOUT External circuits 5