JPH0797285B2 - Process control equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a process control device that controls a process to be controlled by using a feedback controller and a feedforward controller.

[Technical background of the invention and its problems] Regarding the arithmetic expression of the control constant of the feedback / feedforward servo system that suppresses the disturbance and causes the output to follow the target value signal, the method of Park et al. , Suzuki, Fujii: Design of Multivariable Linear Optimal Tracking System with Integral Controller, Proceedings of the Society of Instrument and Control Engineers, Vol, 10, No.1,197
2) is known. That is, the dynamic characteristic of the controlled object is expressed as x (t) = A · x (t) + B · u (t) (1) y (t) = C · x (t) (2) In addition to being described by the state equation, an expanded system including an integral controller and a feedforward compensator is used to calculate the operation signal that minimizes the evaluation function using the solution matrix of the Riccati equation. Here, y (t) is an output, x (t) is a state quantity, u (t) is an input, and A, B, and C are n × n, n × m, and P ×, respectively.
It is a matrix of n.

However, it is difficult to accurately measure the dynamic characteristics of an actual controlled object in the form of a state equation, and Riccat
This method is practically problematic because it is not easy to obtain the i equation efficiently.

On the other hand, Mr. Kitamori said (Design method of control system based on partial knowledge of controlled object, Transactions of the Society of Instrument and Control Engineers, Vol.15, N
o.4,1979), the control system model Gm (s), , And proposes a method of calculating the control constants of the I-PD control system and the PID control system so as to match this model. It can be said that this method is highly practical because the compensator can be constructed based on the low-frequency parameters of the controlled object that are relatively easy to identify, and also based on the available measurement signals. However, these are basically proposals of the calculation method of the control constant of the feedback compensation calculator, and the design of the zero point that contributes to the improvement of the quick response to the target value of the control system, that is, the control constant of the feedforward compensation calculator. Does not show any specific calculation method.

[Object of the Invention]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a process control device which has a means for calculating a control constant of a feedback control system and a feedforward control system while improving a quick response to a target value based on partial knowledge of a controlled object. I am trying.

[Outline of Invention]

A process control device according to the present invention includes a main control computing unit that inputs an output signal of a process to be controlled and a target value signal and outputs a first operation signal, and a second control unit that inputs the target value signal. A feed-forward compensation calculation unit that outputs the operation signal, a feedback compensation calculation unit that inputs the output signal of the process and outputs a third operation signal, and the first
To a third operation signal, the addition / subtraction unit for adding / subtracting the operation signal of the controlled object, the transfer function parameter input operation unit for inputting the parameter of the transfer function of the controlled object, the main control operation unit, the feed A design parameter input calculation unit for inputting the order of the transfer function according to each control mode of the forward compensation calculation unit and the feedback compensation calculation unit, and the parameter of the reference model of the control system having a zero point, and the transfer function parameter input calculation Section and the signal from the design parameter input operation section are input, and the transfer function of the control system including the controlled object, the main control operation section, the feedforward compensation operation section, the feedback compensation operation section, and the addition / subtraction section is transferred to the reference model. The main control computing unit, feedforward compensation computing unit, feedback compensation It is obtained and a control constant computing unit for calculating the respective control constants calculation unit.

〔The invention's effect〕

In the feedback / feedforward control system,
Not only the feedback compensation computing unit, but also the control constants of the feedforward compensation computing unit can be computed only by simple four-step arithmetic operations based on partial model matching, so that the computing unit can be significantly reduced. Further, the feedforward compensation can improve the quick response of the control system because there is a component that directly acts on the operating end with respect to the change in the target value. Further, since the feedforward compensation works outside the feedback compensation, there is an advantage that the suppression force against disturbance is not deteriorated at all.

Example of Invention

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a schematic configuration of a process control device according to an embodiment of the present invention.

In the figure, a portion 1 surrounded by a chain double-dashed line shows a feedback / feedforward controller, and 2 shows a controlled object.

The feedback / feedforward controller 1 feeds back the output y (t) of the controlled object 2 and inputs the target value r (t) to generate the final operation signal u (t). Main controller 3 for inputting e (t)
And a feedforward compensation calculator 4 for the output y (t)
And a feedforward compensation calculator 5 for the target value r (t)
And include. A portion 6 surrounded by a two-dot chain line is a control constant calculation device. The control constant calculator 6 inputs a transfer function parameter input calculator (GPIN) 7 for inputting parameters of a transfer function Gp (s) of the controlled object 2, a parameter of a reference model and an order of a compensation calculator. Design parameter input calculator (DPI) 8 and control constant calculator (CP) that calculates control constants based on partial model matching
D) 9 and the output of GPIN7 and the output of DPI8 are CP
By inputting to D9, the control constants of each compensation calculator and the main controller of the feedback / feedforward controller 1 are output.

Next, the calculation of each control constant in the control constant calculation device 6 will be described.

Now, the transfer function Gp (s) of the controlled object 2 is GPIN7 is g ₀ , g ₁ , g ₂ , g
Enter each parameter of ₃ . Next, the DPI8 is a reference model Mr (s) expressing the control specifications of the servo system, , Α ₂ , α ₃ , α ₄ ……, β ₁ , β ₂ …… and the transfer function C of the main controller 3, feedback compensation calculator 4 and feedforward compensation calculator 5
(s) / s, F _B (s), F _F (s), Enter the orders n _C , n _B , and n _F of.

Then, the CPD 9 has gi (i = 0,1,2, ...) And αi (i = 2,
3, ...), βi (i = 1, 2, ...) And n _C , n _B , n _F , the following control constants C ₀ , C ₁ , C ₂ , ..., _C n _{C B0} , _{B1, ......, B n B F1} , F2, ......, calculates the _F n _F. For example, n _C = 0, n _B = 1, n _F = 0,
If α ₂ , α ₃ , α ₄ , and β ₁ are satisfied, the target value r (t)
To the output y (t), Becomes Therefore, when the denominator and the numerator are grouped for each power of s and matched with the reference model of Expression (5), the result is as follows.

Therefore, by equating the denominator comrades and the numerator comrades on both sides, the following equation is obtained.

Here, in the equation (6), n _C = 0, n _B = 1 and n _F =
When set to 0, the relationship of the following equation can be obtained from the equation (9).

From equation (10), the following design rule is derived.

That is, when the order of each compensation arithmetic unit is set, the control constants of not only the feedback system but also the feedback system are calculated by simple arithmetic operations such as the equation (11).

Next, the result of controlling the process using this control device will be described.

In this control device, a feedforward I-PD control system is constructed by setting n _C = 0, n _B = 1 and n _F = 0. FIG. 2 is a block diagram thereof. Using the process parameters, each control constant is calculated by equation (11) and set in each compensation calculator. FIG. 3 shows the response waveform of this control system. Then, FIG. 3 (a) shows the response of the output y (t) when the disturbance is set to d (t) = 0 and the target value r (t) is changed in unit step at t = 0. The dotted line is the output response when there is no feedforward control system, and the solid line is the output response when the designed feedforward control system is used. Thus, it can be seen that the quick response is improved. FIG. 3B is a response waveform of the output when the target value is r (t) = 0 and the disturbance d (t) is changed by a unit step at time t = 0. Good regulation waveforms are obtained with or without a feedforward control system. In the present invention, the order n can be arbitrarily selected depending on the control mode of the target process such as the PID control system and the I-PD control system. For example, in the case of a PID control system, n _c as described above
= 2, n _s = 1, n _F = 1 and, in the case of the I-PD control system, n _c
= 0, n _s = 1, n _F = 1.

The present invention is not limited to the above embodiment. That is, the control system of FIG. 2 can be configured by a feedforward PID control system that performs equivalent conversion. Here, 3-2 is a target value filter, and 3-1 is a PID controller. Kc, Ti, Td are from C ₀ , C ₁ , C ₂ to (12)
It can be calculated by the relation of formula.

In addition, the control system in FIGS. 1 and 2 has a structure in which no steady deviation remains for the step target value and the step disturbance, but a steady deviation remains for the ramp target value and the lamp disturbance. I will end up. In such a case, n = 2 may be set in the control system shown in FIG. However, in this system, each compensation calculation polynomial C (s) of the main controller 3, the feedforward compensator 5, and the feedback compensator 4,
F _F (s) and F _B (s) are respectively Is.

In general, if the order of the larger of the disturbance is n _e in the target value which is the exogenous signal, then the steady deviation can be made zero by setting n = n _e +1 (13).
However, the order of the step signal is n _e = 0 and that of the ramp signal is n _e = 1. By configuring as shown in FIG. 5 even for such a high-order exogenous signal, it is possible to obtain a control device in which the steady-state deviation is zero. Further, it can be realized not only for a control system using a continuous operation element but also for a discrete value system such as a digital process controller incorporating a microcomputer.

[Brief description of drawings]

FIG. 1 is a block diagram of a control device according to an embodiment of the present invention, FIG. 2 is a block diagram of a feedforward / IPD control system of the device, and FIG. 3 is a response waveform of the control system. Fig. 4 and Fig. 4 are block diagram of target value filter and feedforward PID control system equivalent to Fig. 2, and Fig. 5 is feedforward I in which steady deviation does not remain for high-order exogenous signals. FIG. 3 is a block diagram of a PD control system. 3 ... Main controller, 4 ... Feedback compensation calculator, 5
...... Feed-forward compensation calculator, 6 ...... Control constant calculator, 7 ...... Transfer function parameter input calculator, 8 ......
Design parameter input calculator, 9 ... Control constant calculator.

Claims (1)

[Claims] 1. A main control arithmetic unit for inputting an output signal of a process to be controlled and a target value signal to output a first operation signal; and a main control arithmetic unit for inputting the target value signal to output a second operation signal. A feed-forward compensation calculation unit that outputs, a feedback compensation calculation unit that inputs the output signal of the process and outputs a third operation signal, and an operation of the controlled object by adding and subtracting the first to third operation signals. An adder / subtractor that generates a signal, and the transfer function Gp of the controlled object expressed by the following equation (1)
The transfer function parameter input operation unit for inputting the parameters g ₀ , g ₁ , g ₂ , ... Of (s), and the transfer function C (s) / s of the main control operation unit expressed by the following equation (2). , The transfer function F _F (s) of the feedforward compensation calculation unit expressed by the following equation (3), and the following (4)
Each order nc, nF, n according to the control mode of the transfer function F _B (s) of the feedback compensation calculation unit represented by the formula
The parameters α ₂ , α ₃ , α ₄ , ... Of B and the reference model Mr (s) of the control system having a zero represented by the following equation (5)
And β ₁ , β ₂ , ..., A design parameter input operation unit, the transfer function parameter input operation unit, and the parameters g ₀ , g ₁ , input from the design parameter input operation unit.
Introducing g ₂ , ..., α ₂ , α ₃ , α ₄ , ..., β ₁ , β ₂ , ... and the orders nc, nF, nB, the transfer functions Gp (s), C
(S) / s, F _F (s), and F _B (s) are used to match the transfer function of the actual control system with the reference model Mr (s), whereby the main control calculation unit , Control constants C ₀ , C ₁ , C ₂ , ... C _{nc of} the feedforward compensation calculation unit and the feedback compensation calculation unit, respectively.
f _F0 , f _F1 , f _F2 , ... f _{F nF} , f _B0 , f _B1 , f _B2 , ... f _{B nB} . Gp (s) = 1 / (g ₀ + g ₁ s + g ₂ s ² + g ₃ s ³ + ...) ...
(1) C (s) / s = (C 0 + C 1 s + C 2 s 2 + ...... + C nc s nc)
/ s… (2) F _F (s) = f _F0 + f _F1 s + f _F2 s ² + …… + f _{F nF} s ^nF
… (3) F _B (s) = f _B0 + f _B1 s + f _B2 S ² …… + f _{B nB} s ^nB …
(4) Mr (s) = {1 + β ₁ (σs) + α ₂ β ₂ (σs) ² + ...
…} / {1 + σs + α ₂ (σs) ² + α ₃ (σs) ³ + α ₄
(Σs) ⁴ + ...} (5) where σ: reference model used for design s: differential operator