JPS62298802A - Automatic adjusting method for control constant of pid controller - Google Patents

Abstract

PURPOSE:To improve the controllability of a control system by decreasing a proportional gain when a vibration period is a constant rate smaller than the integration time of a PID controller. CONSTITUTION:A manipulated variable (u) outputted by a PID controller 1 is inputted to a controller system 2, whose output (y) is inputted to the PID controller 1 as deviation (e) which is a difference from a target value (r), thus constituting a feedback control loop. The deviation (e) is inputted to an automatic control constant adjustment part 3, which determines the proportional gain Kp to automatically adjust the control constant of the PID controller 1. At this time, when the period (p) of vibrations caused by transient deviation is smaller than the integration time Ti set in the PID controller and short, the proportional gain Kp outputted by the automatic control constant adjustment part 3 is decreased by a constant rate, and consequently an automatic adjustment is performed without causing any oscillation state and there is no deterioration in the controllability due to the adjustment.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention Industrial Field of Application The present invention is directed to a feedback control system using a proportional, integral, and differential (PID) regulator, in which a controller is used to track changes in the characteristics of a controlled object. The present invention relates to a method for automatically adjusting control constants of a PID adjuster, which automatically adjusts control constants of a PID adjuster to optimal values.

Prior Art In the conventional automatic control constant adjustment method of a PID controller, -, P
Proportional control is performed by setting the integral time T of the XD controller to infinity and the differential time Td to zero, gradually increasing the proportional gain Kp to generate an oscillation state, and from the proportional gain Kpo1 and period Pu in this oscillation state, the optimal The proportional gain Kp of
, ,integration time T10. The differential time Tdt is Kpt= o, e X Kpo---(1) Tlt=0
．． 6×−・・・・・・(2) Tdt= 0.125X
Pu--(3) [Ziegfier
-Nlcho°C B (Ziegler-Nichols) limit sensitivity method].

Problems to be Solved by the Invention However, in this automatic adjustment method of control constants, it is necessary to bring the control system into an oscillation state for adjustment, which has the problem of poor controllability. .

The present invention has been made in view of this point, and an object of the present invention is to automatically adjust control constants without causing the control system to enter an oscillation state.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a system in which the period of vibration generated due to the occurrence of a transient deviation is less than or equal to a certain ratio of the integration time set in the PID controller. If it is short, the proportional gain is decreased by a fixed ratio.

Function: In the present invention, by determining the control constant using the method described above, automatic adjustment can be performed without causing an oscillation state, and there is no deterioration in controllability for adjustment.

Embodiment FIG. 1 is a block diagram showing an embodiment of a control system using the method for automatically adjusting control constants of a PID controller according to the present invention.

In FIG. 1, 1 is a PID controller, 2 is a controlled object, and 3 is a PID controller.
is a control constant automatic adjustment section, in which the manipulated variable U output from the PID controller 1 is input to the controlled object 2, and the output y of the controlled object 2 is expressed as the deviation e which is the difference from the target value r.
The signal is input to the D controller 1, and a feedback control loop is configured.

Furthermore, the deviation e is input to the control constant automatic adjustment section 3, where the proportional gain Kp is determined, and the control constant of the PID regulator 1 is automatically adjusted.

Next, a method of adjusting the control constant automatic adjustment section 3 will be explained.

In Fig. 1, when the target value r changes or the output y changes due to disturbance, a transient deviation e occurs, and the controlled object 2
If the control constant of the PID regulator 10 is inappropriate for the characteristic, the deviation e will not settle quickly and vibration will occur. This vibration is -σt e=A・explISIN(ωt+ψ)−・river・(4)
It is expressed as

here, e: deviation A: amplitude σ: Attenuation constant t: time ω: Angular frequency ψ: phase angle It is.

In order to find the relationship between the damping constant σ and the angular frequency ω and the control constant, a numerical experiment was conducted on vibration generation while changing the target value r.

5"-" However, the integral time T4 and differential time Td of the PID controller 1 are fixed, and the characteristics of the controlled object 2 are a dead time + linear lag system, and the value of the process gain plus one time constant T1 dead time is as follows. I made it like the table.

The vibration waveforms in Experiment 1 are shown in FIGS. 2a to 2, and the relationship between the damping constant σ and angular frequency ω of these vibrations and the proportional gain Kp is shown in FIG.

In Figure 3, the proportional gain K has a value of 1.0 on the vertical axis.
Let p be the oscillation proportional gain Kp0, and the relationship between the value obtained by dividing the proportional gain Kp by the oscillation proportional gain Kp0, the damping constant σ, and the angular frequency ω, and the relationship between the value obtained by dividing the period p by the integration time Ti. The experiment is shown in Figure 4.

6...-1 It can be seen that the experimental points exist almost on one straight line regarding the damping constant σ and the angular frequency ω in the bag diagram.

The regression equation based on the least squares method for this experimental point is as follows.

Here, a: Coefficient (a p-10.590) b: Coefficient (b
p-1,696).

The relationship between the damping constant σ, the angular frequency ω, and the damping coefficient ξ is as follows.It is known that the square control area is minimized when the damping coefficient ξ is 0.5 (Automatic Control Handbook). Fundamentals Edition 1984) l From formula (6), when -Uπ vertical axis eXpω in Fig. 4 is 0.163, the square control area becomes minimum, and the corresponding horizontal axis Kp/Kpo (l-j: 0.
It becomes 472.

7...- On the other hand, the value obtained by dividing the period p in Fig. 4 by the integration time T,
The relationship with the horizontal axis Kp/Kpo is that for all experiments, if the proportional gain Kp is larger than the appropriate value, the period p
This shows that T becomes smaller with respect to the integration time T.

From the above, when the period p is shorter than the integral time Ti set in the PID controller by a fixed ratio or less, controllability is improved by reducing the proportional gain Kp by a fixed ratio.

Effects of the Invention As described above, according to the present invention, the control constant of the PID regulator can be determined only by the period of vibration, and furthermore, since automatic adjustment can be performed without causing an oscillation state, the controllability for adjustment is improved. It does not cause any deterioration and is extremely useful in practice.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of a control system using the automatic control constant adjustment method for a PID controller of the present invention. Fig. 3 is a characteristic diagram showing the relationship between the vibration damping constant and angular frequency of Fig. 2 and the proportional gain from Fig. 2a, and Fig. 4 shows the relationship between the proportional gain and the oscillation proportional gain. FIG. 7 is a characteristic diagram showing the relationship between the divided value, the attenuation constant, and the angular frequency, and the relationship between the period divided by the integral time over all experiments. 1... PID controller, 2... Controlled object, 3... Control constant automatic adjustment unit. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 (b) Figure 2 (C) (d) Figure 2 (e) c) Figure 2 ('J) (h) KP= 6. o 72 = 033 Tj =
0(j)

Claims (1)

[Claims] The period of vibration caused by the transient deviation is
A method for automatically adjusting a control constant of a PID controller, characterized in that when the integration time set in the PID controller is shorter than a certain ratio, the proportional gain is reduced by a certain ratio.