JPS5941004A - Process control device - Google Patents

Abstract

PURPOSE:To shorten the time required for the complete setting of control for disturbance by automatically switching a feedback control system and a feedforward control system to control a process. CONSTITUTION:When a disturbance signal is changed like figure A, dynamic compensating signal is suddenly changed and exceeds the prescribed range of a proportional discriminating part 20, so that a switch is turned from on to off like figure B. Receiving the switching, a one-shot circuit is actuated and a one-shot switch 24 is connected only once as shown in the figure C. If it is defined that the size of variation of a static characteristic compensating signal due to the variation of disturbance is A as shown in the figure D and the difference of a set value SV and a process value PV, i.e. the size of a control deviation proportional signal, is B, an operation signal excluding the dynamic characteristic compensating part is increased up to A+B as shown in figure E when the disturbance is suddenly changed, and the signal is fixed only a feedforward control section. Therefore, a speed/position type signal converting part 14 receives a signal from an adding part 13 and outputs the operation signal shown by the figure E.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a process control device, and particularly to a process control device that controls a process by automatically switching between a feedback control system and a feed-forward control system.

[Technical field of invention]

Feedback control plays an important role in process control equipment, but this control method focuses only on control results, and performs corrective control only after a control deviation occurs based on the results. Sudden change in disturbance such as
It has a major unavoidable flaw in that control over C is disrupted.

A process control device that improves the controllability of disturbances by combining feedforward control with feedback control that measures the disturbance and compensates for the effect of the disturbance in advance before it appears (control amount 1). There is.

The configuration of this prior art is shown in FIG. In the figure, the feedback control system consists of a set value signal SV and a process value signal P.
A deviation signal 10 is taken out from the difference with V and inputted into the adjustment section 11, and an adjustment output signal is determined by the adjustment section 11 so that this deviation becomes zero. This adjustment output signal is switch 1
2, an adder 13, a speed/position converter 14 that converts and outputs a velocity-type input signal into a position-type signal, and another adder 15. is controlled to the set value S■.

In contrast, the feed 7-ard control system multiplies the disturbance signal by a coefficient in a coefficient unit 17 to obtain a disturbance compensation signal Dn. General 2 of the feedforward model is expressed as TD = time constant T between disturbance → controlled variable, = time constant T between operation signal → controlled variable = gain, and when G1 is modified, the static characteristic compensation is Since it can be decomposed into 1 and 3 for dynamic characteristic compensation, the signal for static characteristic compensation is taken out from the converter 18 which converts the position type signal into a 1,000 T9·S velocity type signal, and the signal for dynamic characteristic compensation is extracted from the incomplete differentiator 19. Find the minutes. The speed type static object compensation signal 4n obtained from the converting section 18 that converts the input signal of the position type signal into a speed type signal is added to the speed type adjustment signal in the adding section 13.

The dynamic characteristic compensation signal En obtained from the incomplete differentiator 19 as a dynamic characteristic compensation component is added to the position type adjustment signal in another adder 15.

Then, in order to separate the feedforward control system by adding a feedforward control system to the feedback control system, the dynamic characteristic compensation signal is led to the comparison/determination section 20 and compared with a predetermined level Xo.
The switch 12 is switched from closed to open by the output of this discriminator corresponding to the input signal exceeding o.

That is, (2) when 1Enl≧Xo, the switch 12 is non-conductive (B); when (En)<Xo, the switch 12 is treated as conductive.

Finally, 9 (in the case of At, only feedforward control,
In case (g), the process is controlled by a combination of controls such as feedforward controller feedback control.

〔problem〕

In a process control device that selectively connects a feed forward control system to a feed forward control system, controllability is improved, but if a step disturbance occurs when there is a control deviation signal, the control The control deviation corresponding to the deviation signal remains as is, resulting in a delay in control convergence. In particular, in actual process control devices, there are many cases where step-like disturbances occur in a state where there is a control deviation, so there are many parts where the transient quality is degraded. In addition, as the process speeds up and C is increased, control deviations that appear for a longer period of time will result in more areas where transient quality has deteriorated.

Therefore, in response to the trend of speeding up processes and intensifying changes in load, a process control device that incorporates a feedforward control system into a feedback control system cannot be evaluated as having satisfactory control.

[Purpose of the invention]

The object of the present invention is to provide a process control device that eliminates the drawbacks of the prior art.

[Summary of the invention]

When a sudden change in disturbance occurs and the feedback control is disconnected, a signal proportional to the control deviation is added to the speed shadow signal for static characteristic compensation of the feedforward control in the direction in which the control deviation disappears only once. Configure it to settle in a short time.

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 2, circuit elements that perform the same functions as those in FIG. Then, a signal proportional to the control deviation signal is obtained.

The output signal of the comparison/discrimination section 20 is input to the one-shot circuit 22, and when the dynamic characteristic compensation signal exceeds a predetermined range, the switch 24 of the one-shot circuit 22 is made conductive only once, and the signal is proportional to the control deviation signal. The adder 23 is configured to add the signal to the static characteristic compensation signal.

The operation of the process control device configured as described above will be explained with reference to FIG. 3.

Figure 3 shows the waveforms of various parts when the disturbance signal changes in a stepwise manner. exceeds the predetermined range, the switch 16 is turned from on to off as shown in FIG. 3B. Further, in response to this signal, the one-shot circuit 22 is activated, and the one-shot switch 24 is made conductive only once as shown in FIG. 3C.

Let the magnitude of the change in the static characteristic compensation signal due to the change in the disturbance signal be A as shown in the third diagram, and set value S and process value P.
If the difference in V, that is, the magnitude of the control deviation proportional signal, is B, then
As shown in FIG. 3B, the operation signal that does not include the dynamic characteristic compensation becomes the foot price in the section of A+H where the increase is only controlled by feed-furd control at the moment when the disturbance suddenly changes. That is, the velocity shadow signal/position signal converter 14 converts the
The signal obtained by adding the Vn signal to the previous input MVH-1 continues to be output to the output side, and even if tMNn becomes zero next time, the velocity shadow signal/position signal converter 14 outputs MVn+1MV. A signal of χO) is generated. As a result, an operation signal as shown in FIG. 3E is output.

After that, when the dynamic characteristic compensation signal becomes lower than the discrimination level, the switch 12 is closed, and a combination of feedforward control and feedback control is performed, and the set value and the process value become equal.

As is clear from this, during feedforward control, the operation signal is obtained from a signal that is the sum of the control deviation proportional signal and the static characteristic compensation signal of the disturbance signal, so when the disturbance occurs and feedforward control ends, the control deviation is There will be no such thing as just one remaining.

〔Effect of the invention〕

According to the present invention, even if there is a control deviation during the feedford control, it is possible to prevent the control deviation from remaining at the end of the feedford control, so that the time required for the control to completely settle due to disturbance can be shortened. In process control where disturbances occur in a state where there is a control deviation, the present invention is effective because the time required for complete settling is short, such as speeding up the process and increasing load fluctuations. If there is even a slight disturbance in transient control, a large amount of products with degraded quality will be produced, leading to increased losses, but if this application is adopted, these losses can be reduced to 11 yen. It can be stopped. Additionally, the present application is applicable to any process control and has a wide range of uses. Although the control deviation signal is applied to the adding section 23 via a one-shot switch, the present invention is not limited to this, and it is of course possible to use the adjustment signal of the adjustment section 11 in place of the control deviation signal. That's true.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a conventional process control system that performs control by selectively switching between a feedback control system and a feedback control system, and FIG. 2 is a block diagram showing the configuration of the present invention. , FIG. 3 is a diagram showing waveforms at various parts in FIG. 2. 11...Adjustment unit 14...Velocity shadow signal/position signal conversion unit 17.
... Coefficient 18 ... Position shadow signal/velocity type 1st signal conversion unit 19
....Incomplete differentiation section 20...Comparison/discrimination section 22...One-shot circuit 23...Addition section 24...One-shot switch 12・・・・・・
・Switch 16...Process

Claims (1)

[Scope of Claims] (1) A feedback control system that controls the process after converting the adjustment signal calculated from the target value and the control amount in a velocity shadow signal/position signal converter; A feed-furd control system in which a disturbance signal that is input to a speed type signal converter and an incomplete differentiator and becomes a speed shadow signal is added to an adjustment signal, and a disturbance signal in an incompletely differentiated state is added to a position shadow signal. , a switching unit that switches the feedback control system to the feed 7-ard control using a discrimination signal generated when the incomplete differential signal exceeds a predetermined level; and a switching unit that switches the feedback control system to the feed 7-ard control using the discrimination signal; The deviation signal component or adjustment signal of the speed shadow signal/
A process control device comprising means for inputting an input to the input side of a position signal conversion circuit. e) The means recited in claim 1 includes a monostable multivibrator, and inputs the deviation signal component or adjustment signal to the speed shadow signal/position signal conversion circuit only once during feed control. Characteristic process control equipment. (3) The deviation signal component described in claim 1 is:
A process control device characterized in that it also includes a deviation signal multiplied by a coefficient using a coefficient multiplier.