JPS62298804A - Automatic adjusting method for control constant of pid controller - Google Patents

Abstract

PURPOSE:To improve the controllability of a control system by increasing a proportional gain when a vibration period P is more than a constant rate longer than the integration time of a PID controller. CONSTITUTION:A manipulated variable (u) outputted by the PID controller 1 is inputted to a controlled 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. Further, the deviation (e) is inputted to an automatic 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 due to transient deviation is more than the constant rate longer than the integration time Ti set in the PID controller, the proportional gain Kp is increased by a constant rate. Consequently, the automatic adjustment is performed without causing any oscillation state, so deterioration in controllability due to the adjustment is precluded.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention Industrial Field of Application The present invention tracks changes in the characteristics of a controlled object in a feed pack control system using a proportional, integral, differential (PID) controller. 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 for a PID controller, proportional control is performed by setting the integral time Ti of the regulator to infinity and the differential time Td to zero from P, and gradually increasing the proportional gain Kp-2.\-7. A large comb generates an oscillation state, and from the proportional gain Kpo1 and period Pu in this oscillation state, the optimal proportional gain Kp, integral time T, and differential time Tdt are determined as Kpt-0,6×Kpo... 1) Tit=0
．． To 6×...(2) Tdt-0,125X Pu-(3) [Ziegjl! er-N1cho
I! , s (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 the control constants as soon as the control system is brought into an oscillation state. .

Means to Solve the Problem In order to solve the above problem, the present invention provides a method in which the period of vibration generated due to the occurrence of a transient deviation is longer than a certain ratio of the integration time set in the PID controller. In this case, the proportional gain is increased by a certain ratio to improve controllability.

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.
There is no deterioration in controllability due to 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.
It is input to the D regulator 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 K 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
With respect to the characteristics, if the control constant of the PID regulator 1 is inappropriate, the deviation e will not settle quickly and vibration will occur. This vibration is -σt e =A @exp @5IN(0)
t+ψ) −(4).

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.

However, the integral time T0 and differential time Td of the PID controller 1 are fixed, the characteristics of the controlled object 2 are dead time + 1st order delay system, and the value of 1 time constant T1 dead time in the process gain is as shown in the table below. did.

The vibration waveforms in Experiment 1 are shown in FIGS. 2A to 2C, 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 Kpo, and the relationship between the proportional gain Kp divided by the oscillation proportional gain Kp0, the damping constant σ and the angular frequency ω, and the relationship between the period P divided by the integration time T i are all The experiment is shown in Figure 4.

6. Regarding the attenuation constant σ and the angular frequency ω in FIG. 4, it can be seen that the experimental points exist almost on one straight line. The regression equation based on the least squares method for this experimental point is as follows.

here a: Coefficient (ap=-0,590) b: Coefficient (bp=1.596) It is.

The relationship between the damping constant σ, the angular frequency ω, and the damping coefficient ξ is as follows. It is known that when the damping coefficient ξ is 0.5, the square control area is the minimum, and (automatic control ...Ndopsoku Basic Edition 1984), from equation (6), the vertical axis -eX in Figure 4
When pω" is 0.163, the square control area is minimum,
The corresponding horizontal axis Kp/Kpo is 0.472.

On the other hand, the value obtained by dividing the period P in FIG. 4 by the integration time Ti,
The relationship with the horizontal axis Kp/Kpo shows that in all experiments, when the proportional gain Kp is smaller than the appropriate value, the period P increases rapidly with respect to the integration time Ti.

From the above, when the period P is longer than the integral time T1 set in the PID controller by a certain ratio or more, controllability is improved by increasing the proportional gain Kp by a certain ratio.

Effects of the Invention As described above, according to the present invention, the control constant of the PID regulator can be determined only from the period of vibration, and furthermore, since it can be automatically adjusted without causing an oscillation state, it is possible to control the control constant for adjustment. It does not cause any deterioration in sex and is extremely useful for practical purposes.

[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, and FIG. In the trench, the vibration waveform diagram obtained by changing the proportional gain, Figure 3 is a characteristic diagram showing the relationship between the vibration damping constant of Figure 2 β from Figure 2 a, the angular frequency, and the proportional gain, Figure 4 The figure is a characteristic diagram showing the relationship between the value obtained by dividing the proportional gain by the oscillation proportional gain, the damping constant, and the angular frequency, and the relationship between the value obtained by dividing the period by the integral time, over all experiments. 1... PID controller, 2... Controlled object, 3...
...Control constant automatic adjustment section. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 (S9 +1JI (b) Figure 2 (C) (Z9 Figure 2 (zo) Figure 2 CI) (/I) Figure 2

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 longer than a certain ratio, a proportional gain is increased by a certain ratio.