RU2258950C2 - Adaptive system for controlling object with variable transporting delay - Google Patents

Abstract

FIELD: automatics.

SUBSTANCE: system has set-point device, first adder, adjusting means, first object model, first delay element, second object model, adjustment block, processed product movement indicator, first quantizer, compensation adjusting means, second adder, multiplier, extrapolator, comparison element, second quantizer, second delay element, first, second, third and fourth keys.

EFFECT: higher speed of operation, higher efficiency, broader functional capabilities.

5 dwg

Description

The invention relates to automation, in particular to adaptive automatic control systems, is intended to control objects with variable transport delay under random disturbances and can be used in production lines of textile, light and chemical industries.

A device is known for controlling an object with delay (Smith controller) [1], which includes a typical controller, an object model without delay, a delay element, first, second, and third adders.

In this system, high performance is ensured by predicting the reaction of the object to the control action using the model without delay. In this case, the signal from the output of the model is fed to the input of the regulator, usually a typical one.

The disadvantage of such a system is a significant deterioration in accuracy and speed, even with small variations in the parameters of the control object, especially the delay. In addition, the speed of such a system during the development of perturbations is limited to a value of 1.5-2 of the delay interval.

Also known is a control system for a tumble-spreading machine (SCM) [2], which is an object with a transport delay. This system includes sensors for fabric parameters (width, density, humidity), a direct control channel, a feedback channel with a proportional-integral (PI) controller, as well as a temperature control subsystem in the drying chamber of the machine.

In this system, high performance during the processing of disturbances is ensured by a direct channel with a compensation regulator, and stabilization accuracy is ensured by a feedback channel.

However, such a system requires a long adjustment when changing the parameters of the control object, for example, when changing the article number of the processed fabric. In addition, the presence of a feedback channel with the PI controller leads to a transient process with a duration of 5-6 delay intervals when the system is turned on.

The closest technical solution is an adaptive control system for objects with delay [3], which contains a master, adder, controller and object, as well as two object models (two predictors), a delay element, and a model tuning unit.

In this system, high performance is ensured through the use of an object model without delay, the signal of which is fed to the input of the controller, and adaptation to changing object parameters is provided by the tuner.

The disadvantage of this system is the speed limit when working out disturbances with a value of 1.5-2 of the delay interval and the deterioration of the quality of regulation when changing the delay value of the object.

The technical result of the invention consists in increasing the speed of the system when working out disturbances, providing adaptation to changing the delay value and transmission coefficients of the object, reducing the duration of transients when the system is turned on.

To achieve a technical result, the system consisting of a setter, a first adder, a regulator, a first object model and a first delay element connected in series, a second object model, a tuner and an object with variable delay, additionally includes a displacement sensor for the processed product, a first quantizer, a compensation controller, second adder, multiplier, extrapolator, comparison element, second quantizer, second delay element, first, second, third and fourth keys.

A disturbance signal is applied to the first input of the first quantizer, and the second input is connected to the output of the displacement sensor, the output of the compensation controller is connected to the first input of the second adder, the output of which is connected to the first input of the multiplier, the output of the extrapolator is connected to the first input of the control object, the second input of which acts the above disturbance signal. The first input of the tuner is connected to the output of the first quantizer, the second input is to the output of the second quantizer, and the third input is to the output of the displacement sensor, the first output of the tuner is connected to the second input of the multiplier, while the first input of the second quantizer is connected to the output of the control object, the second input - with the output of the displacement sensor. The input of the comparison element is connected to the second input of the tuner, and the output is connected to the control inputs of the first, second, third, and fourth keys. The output of the second quantizer through the fourth key is connected to the second input of the first adder, the third input of which through the third key is connected to the output of the second delay element, the fourth input is connected to the output of the first delay element, the fifth input is the output of the first model of the object, the second input of the second adder is through the first the key is connected to the master, the third input through the second key is connected to the output of the controller, the input of the second model of the object is connected to the output of the controller, and the output to the input of the second delay element.

Comparative analysis with the prototype showed that the proposed control system is distinguished by the presence of a displacement sensor, first and second quantizers, a compensation regulator, a second adder, a multiplier, an extrapolator, a comparison element, a second delay element, the first, second, third and fourth key elements, as well as relationships between them, namely the following.

The first quantizer, the compensation regulator, the second adder, the multiplier and the extrapolator connected in series form a direct channel of compensation of perturbations. The introduction of such a channel into the delayed control system makes it possible to achieve maximum speed when processing disturbing influences.

The use of combined controllers in delayed control systems is a well-known technical solution. However, in this case, the introduction of new elements and the relationships between them ensures the adaptation of the system to changes in the parameters of the object, as well as the stability of self-tuning processes.

The multiplier, the second input of which is connected to the first output of the tuner, provides the adjustment of the compensation regulator when changing the transfer coefficient of the object. In this case, the criterion is the transmission coefficient of the system along the perturbation transmission channel, which during the tuning process is reduced to zero.

The use of the first, second, third and fourth keys that control the comparison unit ensures that the Smith controller is disconnected from the object in the setup mode, and the second model with the second delay element is connected instead. This solution allows you to ensure the stability of the tuning process, as well as to eliminate transient processes when switching the system to operating mode.

The use of a displacement sensor and quantizers with a variable quantization period allows the system to be adapted to change the delay time of the control object. In this case, the delay time of the first and second delay elements is set in relative units — quantization periods.

Thus, the noted differences of the proposed device from analogues and prototype are significant.

The block diagram of the adaptive control system (Fig. 1) includes a first quantizer 1, a compensation regulator 2, a second adder 3, a multiplier 4, an extrapolator 5, a control object 6, a displacement sensor 7, a tuner 8, a comparison unit 9, a second quantizer 10 , master 11, first key 12, second key 13, first adder 14, controller 15, first object model 16 and first delay element 17, second object model 18 and second delay element 19, third key 20 and fourth key 21.

A disturbing effect is applied to the first input of the first quantizer 1, the second input (control input) of which is connected to the output of the displacement sensor 7. The digital signal of the first quantizer passes through the compensation regulator 2, the second adder 3, the multiplier 4, and the extrapolator 5. The output of the compensation regulator 2 connected to the first input of the second adder 3, the second input of which through the first (normally closed) key 12 is connected to the output of the setter 11, and the third input through the second (normally open) key 13 is connected to the output of the regulator 15. The signal from the output of the second adder 3 passes through a multiplier 4 and an extrapolator 5, the output of which is connected to the input of the object 6. The output of the object 6 is connected to the first input of the second quantizer 10, the second input of which receives the signal of the displacement sensor 7.

The output of the master 11 is connected to the first input of the first adder 14, which is connected in series with the controller 15, the first model of the object 16 and the first delay element 17. The output of the controller 15 is also connected to the input of the second model of the object 18, the output of which is connected to the input of the second delay element 19. The second input of the first adder 14 through the fourth (normally open) key 21 is connected to the output of the second quantizer 10, the third input through the third (normally closed) key 20 is with the output of the second delay element 19, the fourth input is with the output of th delay element 17, the fifth input - with the output of the first model object 16.

The first and second inputs of tuner 8 are connected to the outputs of the first (1) and second (10) quantizers, respectively, the third input is connected to the output of the displacement sensor 7, the first output of block 8 is connected to the second input of the multiplier 4, and the second output is connected to the input of the comparison unit 9 whose output is connected to the control inputs of the first (12), second (13), third (20) and fourth (21) keys.

The control object 6 consists of a link without delay with the transfer function H ₀₁ (s) and a link of transport delay with the transfer function H ₀₂ (s) connected in series. The control signal u (s) is supplied to the first input of object 6, and a disturbance signal x (s) is supplied to the second input:

where y (s) is the signal at the output of the object; K ₁ and K ₂ - transmission coefficients; T ₁ - time constant; τ is the delay time, s is the Laplace argument.

The transfer function of the compensation controller 2 is inverse to the transfer function of the control object H ₀₁ (s):

H _KR (z) = I / H ₀₁ (z); H ₀₁ (z) = Z {H ₀₁ (s) H _e (s)}, (2)

where Z is the symbol of the conditional z - transformation (according to the tables); H _e (s) = (1st- ^sTo ) / s is the transfer function of the extrapolator; T _about - period of time quantization. Given expression (1) we get

H _KR (z) = 1-dz ^-1 , (3)

where d = T / T _o - time constant.

Block 8 provides the adjustment of the gain of the compensation regulator K _R [i] in accordance with the recurrence expression

- оценка коэффициента передачи системы по возмущению ΔК=1-К_RК_o; i - номер периода квантования. Оценки

вычисляются методом наименьших квадратов (МНК)where h is a coefficient that sets the pace of tuning;

- assessment of the transmission coefficient of the system perturbation ΔK = 1-K _R To _o ; i is the number of the quantization period. Grades

are calculated by the least squares method (OLS)

- на второй выход блока.where x [i, j] is the disturbing effect on the object; y [i, j] is the signal at the output of the object; j is the number of samples, n is the number of samples within the quantization period; m = int (τ / Т _o ) is the relative value of the delay. The value of K _R [i] is supplied to the first output of block 8, and the value

- to the second output of the block.

формируется на втором выходе блока настройки 8 и сравнивается блоком 9 с уровнем значимости δК. При условии

блок 9 замыкает первый (12) и третий (20) и размыкает второй (13) и четвертый (21) ключи. При этом объект управления 6 исключается из контура обратной связи и вместо него включается вторая модель 18 и второй элемент задержки 19. На объект воздействуют сигналы компенсационного регулятора 2 и задатчика 11, объединенные вторым сумматором 3. Настройка компенсационного регулятора осуществляется блоком 8, на каждом шаге вычисляется МНК - оценка коэффициента

и коррекция величины К_R[i]. Как только оценка становится незначимой, блок 9 переключает структуру системы и переводит ее в рабочий режим.In setup mode, the system operates as follows. Estimation of the system transmission coefficient over the disturbance channel

is formed at the second output of tuner 8 and is compared by block 9 with a significance level of δK. On condition

block 9 closes the first (12) and third (20) and opens the second (13) and fourth (21) keys. In this case, the control object 6 is excluded from the feedback loop and the second model 18 and the second delay element 19 are turned on. The signals of the compensation regulator 2 and the setpoint switch 11, combined by the second adder 3, act on the object. The compensation regulator is set by block 8, at each step it is calculated MNC - coefficient estimation

and correction of the quantity K _R [i]. As soon as the assessment becomes insignificant, block 9 switches the structure of the system and puts it into operation.

, блок 9 замыкает второй (13) и четвертый (21) и размыкает первый (12) и третий (20) ключи. При этом вместо второй модели 18 и второго элемента задержки 19 в контур обратной связи включается объект управления 6. В результате образуется комбинированная система управления с прямым и обратным каналами. Прямой канал системы обеспечивает эффективную компенсацию возмущений, а канал обратной связи - сведение к нулю статической ошибки. Применение второй модели объекта (18) и второго элемента задержки (19) позволяет устранить переходный процесс при переключении структуры системы.In operating mode, at

, block 9 closes the second (13) and fourth (21) and opens the first (12) and third (20) keys. Moreover, instead of the second model 18 and the second delay element 19, a control object 6 is included in the feedback loop. As a result, a combined control system with forward and reverse channels is formed. The direct channel of the system provides effective compensation of disturbances, and the feedback channel - reducing to zero the static error. The use of the second model of the object (18) and the second delay element (19) eliminates the transition process when switching the structure of the system.

When the delay (transport speed) changes, the pulse repetition period of the sensor 7 changes, which control the quantizers 1 and 10. Thus, by changing the quantization period, the digital system is tuned to the actual delay value of the control object.

The simulation results of the adaptive control system of the object with delay under the action of disturbances are presented in figure 2, figure 3, figure 4 and figure 5. The perturbing effect at the input of the control object (figure 2) is a random recovery process, which is superimposed on a Gaussian random process.

The graph of the change in the transmission coefficient of the compensation regulator K _R - is shown in Fig.4, and the graph of the change in the transmission coefficient of the system along the disturbance channel ΔK - in Fig.5. Analysis of the graphs shows that the transition process in the adaptation circuit is completed in a time equal to 4 ÷ 5 delay intervals, the overshoot does not exceed 10%.

Transient characteristics of the adaptive control system of the object with delay are shown in figure 3. The moment of completion of the adaptation process is indicated by a dash-dotted line, while connecting the Smith controller does not cause a transition process in the system. The tuned system almost completely eliminates the influence of disturbances on the controlled quantity. This is due to the high speed of the direct compensation channel, the regulation time of which is equal to the quantization period T _o . A change in the set density value at time t = 200 s illustrates the dynamic properties of the feedback loop of the system. The transition process in the circuit is completed in a time equal to 1.5 delay intervals, and the overshoot does not exceed 1 ÷ 2%.

Thus, the proposed system provides high accuracy and speed as when compensating for disturbances, and when working out the driving action. In addition, the system provides adaptation to changing the transmission coefficients and the delay time of the control object.

Sources of information

1. Guretsky X. Analysis and synthesis of control systems with delay. - M.: Mechanical Engineering, 1974. - 328 p.

2. Automatic control of technological processes of finishing production. / L.I. Belenky, L.A. Omelyanchuk, S.S. Shvyrev. - M .: Legprombytizdat, 1990 .-- 208 p.

3. A.S. 968788 USSR, MKI G 05 V 13/02. Adaptive control system for objects with variable delay. / A.A. Moskalenko et al. // Discoveries. Inventions 1982 - No. 39.

Claims (1)

An adaptive control system for an object with a variable transport delay, comprising a controller, a first adder, a regulator, a first object model, a first delay element connected in series, a tuner, a second object model, and a variable delay control object that is affected by a disturbance, characterized in that the system additionally includes a first quantizer, a compensation regulator, a second adder, a multiplier and an extrapolator connected in series, a pulse displacement sensor the processed product, the comparison unit, the second quantizer, the second delay element, the first, second, third and fourth keys, moreover, a disturbance signal is applied to the first input of the first quantizer, and the second input is connected to the output of the pulse sensor for moving the processed product, the output of the compensation regulator is connected to the first input of the second adder, the output of which is connected to the first input of the multiplier, the output of the extrapolator is connected to the input of the control object, the first input of the tuner is connected to the output of the first antitator, the second input with the output of the second quantizer, and the third input with the output of the pulse sensor for moving the processed product, the first output of the tuner is connected to the second input of the multiplier, while the first input of the second quantizer is connected to the output of the control object, the second input to the output of the sensor moving, and the output through the fourth key is connected to the second input of the first adder, the third input of which through the third key is connected to the output of the second delay element, the fourth input is connected to the output of the first element delays, the fifth input - with the output of the first model of the object, the second input of the second adder through the first key connected to the master, the third input through the second key connected to the output of the controller, the input of the second model of the object connected to the output of the controller, and the output to the input of the second delay element, the input of the comparison unit is connected to the second output of the tuner, and the output is connected to the control inputs of the first, second, third, and fourth keys.

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