JPH04294402A - Pid control device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is applied to a controller that controls phenomena such as temperature, humidity, and pressure in an electric furnace according to a preset program pattern. P to correct parameters
This relates to an ID control device.

0002

2. Description of the Related Art Fixed value or program controllers are often used, for example, when various heat treatments such as electric furnaces are to be controlled. In this controller, fixed value or trapezoidal control is performed according to a preset program pattern as shown in FIG. 3, for example. To explain further, the deviation obtained by comparing the measured value PV from a thermocouple installed in the electric furnace with the set value SV according to a preset program pattern is calculated by PID, and the output after this PID calculation is performed. Phenomena such as temperature, humidity, and pressure inside the electric furnace were controlled based on the manipulated variable MV.

0003

[Problems to be Solved by the Invention] This type of controller uses PID calculations to control each phenomenon in the electric furnace so that the measured value PV converges to the set value SV and there is no deviation. However, in reality, it takes time for the measured value PV to converge to the set value SV and stabilize due to the influence of disturbances, resulting in control errors due to overshoot OS or undershoot US as shown in the figure. A stable state always occurred. Control errors caused by overshoot OS or undershoot US are most disliked in the control of this type of controller, and there are problems such as a large amount of wasted energy being consumed by this error.

[0004] Furthermore, since each parameter of the PID constant changes depending on the controlled object, the operator
Each parameter of the PID constant in the controller was adjusted. However, since the degree to which overshoot OS or undershoot US occurs is determined by the adjustment, accurate adjustment is always required and adjustment time is required, which places a burden on the operator.

The present invention has been made in view of the above-mentioned problems, and is capable of reducing the degree of occurrence of overshoot or undershoot for any controlled object, and also makes it possible to reduce the amount of adjustment of the PID constant. It is an object of the present invention to provide a PID control device that can perform adjustment without strictness, shorten adjustment time, and reduce the burden on the operator.

[0006]

[Means for Solving the Problems] In order to achieve the above object, a PID control device according to the present invention performs a PID calculation on the deviation between a preset setting value and a measured value from a controlled object. PI that outputs the manipulated variable corresponding to the result
The present invention is characterized by comprising a D control means and a fuzzy control means for correcting and outputting the operation amount of the PID control means from the state of the set value and the measured value according to a predetermined fuzzy rule.

[0007]

[Operation] The PID control means performs PID calculation of the deviation between the preset setting value and the measured value from the controlled object.
A manipulated variable corresponding to the result of the D calculation is output to the fuzzy control means. The fuzzy control means corrects and outputs the manipulated variable based on the set value and measured value according to a predetermined fuzzy rule.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing an embodiment of a PID control device according to the present invention. P according to this example
The ID control device is applied, for example, to a controller that controls phenomena such as temperature, humidity, and pressure in an electric furnace as a control target, and corrects the manipulated variable obtained by PID calculation when controlling each phenomenon. It is configured to include a PID control means 1 and a fuzzy control means 2.

The PID control means 1 receives as control objects, for example, a measured value PV from a thermocouple disposed in an electric furnace, and, for example, a set value SV of a preset program pattern. Deviation E between PV and set value SV
(=SV-PV), and a manipulated variable mv (corresponding to, for example, electric power for driving a heater in an electric furnace) based on this deviation E is output to the fuzzy control means 2.

The fuzzy control means 2 is connected in series after the PID control means 1, and similarly to the PID control means 1, the measured value PV and set value SV are input thereto. In this fuzzy control means 2, for example, when a deviation E occurs between the measured value PV and the set value SV, the degree of increase/decrease in the manipulated variable mv from the PID control means 1 is determined according to a predetermined fuzzy rule. The final manipulated variable MV is calculated from the state of
is output to the outside. In addition, the measured value PV and set value SV
If there is no deviation E between the two, the manipulated variable mv input from the PID control means 1 is output as is.

Next, the operation of the PID control device configured as described above will be explained with reference to FIG. Now, as an example of a fuzzy rule: (1) If the deviation E is positive, increase the amount of operation. (2) If the deviation E is zero, the manipulated variable is maintained as it is. (3) If the deviation E is negative, reduce the manipulated variable. It is assumed that a deviation E=+3 occurs between the measured value PV input to the PID control means 1 and the set value SV.

Then, in the fuzzy control means 2, first,
Find the degree of agreement for each rule. That is, in rule (1), since the deviation is +3, the degree W is 0.6 from the membership function A1 (see FIG. 2(a)). Next, in rule (2), since the deviation is +3, the degree W is 0.4 from the membership function A2 (see FIG. 2(b)). Furthermore, in rule (3), since the deviation is +3, the degree W is 0 from the membership function A3 (Figure 2(c)
reference).

[0013] Then, each rule (1), (2), (3)
When the obtained degrees are applied to the conclusion part of , the membership functions of the conclusion part become membership functions B1, B2, and B3 cut exactly by the degree W. Next, each rule (1), (2), (3) of the conclusion section cut by degree W
Membership functions B1, B2, and B3 are combined into one as shown in FIG. 2(d), and the center of gravity of the area of the enclosed boundary portion is determined. Then, the obtained center of gravity is vertically lowered toward the manipulated variable axis (X-axis), and the intersection with the manipulated variable axis becomes the final corrected manipulated variable MV.

Therefore, in the embodiment described above, the manipulated variable m based on the result of PID calculation in the PID control means 1
Since v can be corrected and finely adjusted by the fuzzy control means 2, the rise time is faster than before even when changing the set value of the PID constant, and overshoot OS or undershoot US is avoided for any controlled object. The degree to which this occurs can be reduced, and the measured value can be quickly converged to the set value.

Furthermore, even if an unstable state occurs due to disturbance when the control is stable, the control can be brought to a stable state in a short time. Furthermore, since the operator can set each parameter of the PID constant roughly and not so strictly, the setting time can be shortened compared to the conventional method, and the work burden on the operator can be reduced.

Furthermore, by using the fuzzy control means 2 that employs fuzzy rules, the device according to the present embodiment has a vast knowledge base for controlling according to the state. There is no need to incorporate adjustment rules, the knowledge base can be made smaller, and the entire device can be made smaller. Further, the PID control means 1 and the fuzzy control means 2 can be further miniaturized by incorporating them into memory using a microprocessor or the like.

By the way, in the above-mentioned embodiment, by changing the adjustment rule of the fuzzy control means 2, it is possible to stabilize systems ranging from systems with slow control responses such as temperature to systems with fast control responses such as flow rate and pressure. control. For example, when controlling a program pattern,
Add the following fuzzy rule (see Figure 3). (1A) If the previous set value change was positive and the current set value change remains the same, reduce the manipulated variable. (2A) If the previous set value change was negative and the current set value change remains the same, increase the manipulated variable. (3A) If the previous set value change remains the same and the current set value change is positive, increase the manipulated variable. (4A) If the previous set value change remains the same and the current set value change is negative, reduce the manipulated variable. In addition, stable control can be achieved even for control in which set values change from moment to moment, such as in continuous furnaces, tunnel furnaces, and the like. Furthermore, stable control can be similarly performed in cascade connection control, constant value control, and the like.

[0018]

As explained above, according to the PID control device of the present invention, the degree of occurrence of overshoot or undershoot for all controlled objects is reduced, and measured values can quickly converge to set values. be able to. Further, the PID constant can be adjusted roughly and not so strictly, the adjustment time can be shortened, and the burden on the operator can be reduced.

[Brief explanation of drawings]

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

[Fig. 2] A diagram for explaining the operation of the fuzzy control means based on fuzzy rules in the same device.

[Fig. 3] A diagram showing an example of the transition of the control amount with respect to the temperature program pattern controlled by the controller.

[Explanation of symbols]

1 PID control means 2 Fuzzy control means SV setting value PV measurement value E Deviation MV correction operation amount

Claims (1)

[Claims] 1. PID control means for performing a PID calculation on a deviation between a preset setting value and a measured value from a controlled object, and outputting a manipulated variable corresponding to the PID calculation result;
A PID control device comprising fuzzy control means for correcting and outputting the operation amount of the PID control means from the state of the set value and measured value according to a predetermined fuzzy rule.