JP3212336B2 - Limit value control method for PI controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic control system which is designed to meet a specific target. In particular, the present invention relates to a control method configured to perform variable control of a time integration term in accordance with a control state.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram of a conventional PI controller, in which 100 is an arithmetic unit, 101a is a gain setting unit that creates a proportional multiple of a deviation, 102a is an integrator that creates a time integral of the deviation, 101b. And 102b are first and second manipulated variable calculators for giving respective limit values, 103 is an adder for adding outputs from the two manipulated variable calculators, and 104 is a first and a second for giving limit values to the added values. It is a three-operation-amount calculator, and the operation of the PI controller is generally well-known. However, in the conventional method, an addition value is simply created. Here, if FIG. However, the case where the added value does not reach the limit value is shown.

[0003]

(Equation 1)

Here, PIout is an output of the PI controller, K is a constant of a proportional term, and error indicates a deviation between a target value and an actual value. PIout is an operation amount sent to 105 (control target system).

The output A in the block diagram of FIG. 3 is the output of the PI controller. This output is the manipulated variable of the automatic control system. When the system is in a stable state, that is, when the target value matches the actual value, the deviation error, which is the input of the PI controller, is usually zero. When a deviation occurs in FIG. 3, the output A of the PI controller becomes a numerical value represented by Expression 1. Here, the integral value of error indicating the time integral term of the deviation increases as the time during which the deviation occurs is long. Further, in order for the integrated value output of the error to be 0, the polarity of the deviation must be opposite to the polarity of the current integrated value of the error. This will be described with reference to the operation waveform diagram of FIG. 4. Even if the target value and the actual value match at point 3a and [deviation = 0], the output of the PI controller has an error integral. [A = 0] is not obtained, and a hatched portion as shown in FIG. 4C is formed.
At this point, since the PI controller still has an output, the response becomes poor as a control system. When an output value obtained by adding the proportional multiplication term and the time integration term is obtained as shown in the operation waveform diagram of FIG. 5C, the output A of the PI controller at point 4a is changed to the manipulated variable of FIG. The limit value provided by the calculator 104 is reached. In this state, at point 4b in FIG. 5, the output A is still at the limit value due to the time integration term even though the deviation has become zero at point 4b in FIG. Will be given. This also results in poor response as a control system. 4B, when the polarity of the deviation is inverted, the polarity of the proportional multiple is also inverted. Therefore, since the difference does not remain even after the polarity of the deviation is inverted as in the case of the time integration term, the influence on the response of the control system is little. As described above, in the PI controller, since the time integration term has a delay with respect to the change in the polarity of the deviation, there is a problem that the entire control system is delayed.

[0005]

In order to improve the delay of the time integration term of the PI controller, a new limit circuit is provided for the circuit performing the time integration operation, and a circuit for operating the limit circuit is provided. Install. Further, a circuit for changing the limit value of the limit circuit is provided. That is, a first manipulated variable calculator for proportionally multiplying a deviation between a target value and an actually measured value and providing a limit value of the output multiplied by the proportionality, and a second operation amount for providing a limit value of an output of an integrator obtained by time-integrating the deviation. In a PI control device comprising an operation amount calculator and a third operation amount calculator giving a limit value to an added value obtained by adding the outputs of the respective operation amount calculators, A subtractor for subtracting the output of the first manipulated variable calculator, a fourth manipulated variable calculator for providing a limit value to the output of the adder for adding the output of the subtractor and the output of the integrator, and the integrator And a switch for releasing the deviation inputted to the second manipulated variable calculator and releasing the output of the second manipulated variable calculator to input the output of the fourth manipulated variable calculator to the third manipulated variable calculator. The limit value of the calculator is stored in the first operation. By setting the value lower than the limit value of the variable calculator, the output of the integrator stored by switching the switch is kept low, and by providing this output to the third manipulated variable calculator, the time integral of the deviation is reduced. , There is no response delay due to the time integral term.

[0006]

The operation will be described in conjunction with the embodiment described below.

1 is a block diagram in which a time integral term control circuit is added to a PI controller control system according to the present invention. FIG. 2 is an operation waveform diagram showing an example of each section of the PI controller according to the present invention. The same part as the controller is 1
00, 101a, 101b, 102b, 103, 105
And these operations are the same as those described in the prior art. In FIG. 1, a calculator 100 calculates a deviation error from a target value and an actual value of the system 105, and calculates a gain setter 101a, a first manipulated variable calculator 101b, an integrator 1
02a and the second manipulated variable calculator 102b calculate the proportional multiplication term and the time integral term, respectively, and give limits. Adder 10
3 synthesizes them, and the third manipulated variable calculator 104 limits the output of the adder 103. The subtractor subtracts the output of the first manipulated variable meter 101b from the output A1 of the third manipulated variable calculator 104, and supplies the output to the fourth manipulated variable calculator 107 and the switch S3. The fourth manipulated variable calculator 107 is a part that gives a limit value of the time integral term set lower than the new limit value of the first manipulated variable calculator. The gain setting unit 106 and the setting unit 109 give an initial value of the time integration term. S1, S2, and S3 are switches, and each switch is cut in the blackout direction at the same time as the hatched portion of the third manipulated variable calculator 104, that is, when the output from the adder 103 reaches the limit value. To be replaced. Here, the gain setting units 101a, 101
K1 and K2 of 6 are arbitrary constants. Next, the operation will be described. When the input value to the third manipulated variable calculator (PI addition value output limiter) 104 reaches the limit value (shaded portion), the changeover switches S1, S2, S3
To switch to the blackout direction. As a result, the output of the time integration term (FIG. 1, AI) changes to the following equations (2) and (3).

That is, Equations 1 to 3 are transformed and derived as follows. When the switches S1, S2, and S3 are switched at the same time, "error" is set to "0". This is intended to stop the integration operation when the output of the PI controller reaches the limit value. At this point, the integrator 102a has accumulated as indicated. Therefore, this accumulated amount is set as the initial value “C”. As a result, in the equation (2), 0dt is "0" even after time integration, and becomes the equation (3).

(Equation 2)

(Equation 3)

Here, A1 is the output of the PI controller according to the present invention, and AP is the output of the term proportional to the deviation. K2
Is a proportional gain setting device (usually 1). In FIG. 1, A1
Becomes equal to the limit value (the shaded portion 104) given by the third manipulated variable calculator 104, the time integration term stops the integration operation so that the deviation does not increase any more, and the gain becomes a proportional multiple term corresponding to the equation (3). It is provided by the setting device 106.
In a system where the output of the PI controller reaches the limit value, the deviation may be large.
It is necessary to increase the ratio of the proportional double term to the output of the controller. Therefore, A1-AP is calculated by the subtractor 108,
The output of the time integral term is sent to the fourth manipulated variable calculator (limiter) 107 so as to limit the output by (A1-AP). Here, the adder 103 receives the signal (A1) from the fourth manipulated variable calculator 107.
−AP), only the number of APs is sent, so that an increase or decrease in APs can be prioritized. That is, the time integration term is controlled by (A1-AP) by changing the AP. FIG.
FIG. 7 is a diagram of an output waveform of the PI controller in a case where the element of the present invention is added to the output waveform of the conventional PI controller of FIG. 5, and when the addition term reaches the limit value at the point 5a, time integration is performed. The term is given a new limit value, which is changed by the output of the proportional multiplication term until point 5b where the summation term in FIG. 2 (c) begins to fall from the limit. This is shown by the thick dotted line in FIG. FIG. 2 (b) shows the output of the time integration term with thicker dotted and solid lines. As a result, FIG. 2 (c) shows the output of the PI controller of the present invention, and the output of the addition term clearly approaches to zero earlier as compared to FIG. 5 (c).

[0009]

As described above, according to the present invention, when a PI controller including the method of the present invention is used, the occurrence of a response delay due to the time integral term is reduced, and the method is extremely useful.

[0010]

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of a limit value control of a PI controller according to the present invention.

FIG. 2 is an operation waveform diagram of each part of a PI controller according to the present invention.

FIG. 3 is a block diagram of a conventional PI controller.

FIG. 4 shows operation waveforms of respective parts of a conventional PI controller.

FIG. 5 is an operation waveform diagram of each part of a conventional PI controller. You.

[0011]

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 arithmetic unit 101a gain setting unit 101b first manipulated variable calculator 102a integrator 102b second manipulated variable calculator 103 adder 104 third manipulated variable calculator 105 system 106 gain setter 107 fourth manipulated variable calculation Device 108 subtractor 109 setting device

Claims (1)

(57) [Claims] 1. A first manipulated variable calculator that proportionally multiplies a deviation between a target value and an actual measurement value and provides a limit value of the output that is proportionally multiplied, and provides a limit value of an output of an integrator that integrates the deviation with respect to time. In a PI control device comprising a second manipulated variable calculator and a third manipulated variable calculator giving a limit value to an added value obtained by adding outputs of the respective manipulated variable calculators, A subtractor for subtracting the output of the first manipulated variable calculator from the output, a fourth manipulated variable calculator for providing a limit value to the output of the adder for adding the output of the subtractor and the output of the integrator, A switch that releases the deviation input to the integrator and releases the output of the second manipulated variable calculator to input the output of the fourth manipulated variable calculator to the third manipulated variable calculator. 4 The limit value of the manipulated variable calculator is By setting the value lower than the limit value of the manipulated variable calculator, the output of the integrator stored by switching the switch is suppressed low, and this output is given to the third manipulated variable calculator to reduce the time integral of the deviation. A limit value control method for a PI controller, wherein there is no response delay due to a time integration term.