JP2000010602A - Pid control method and its controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To execute proper and stable control by performing PID control operation after a value corresponding to a deviation between a current value detected from a controller object and a target setting value is multiplied by a PID parameter when the deviation is larger than a specified value and performing the PID control operation corresponding to the deviation when it is smaller than the specified value. SOLUTION: An operated deviation ε is compared with the specified value and it is discriminated whether the deviation ε is larger than the specified value or not (S25). When the deviation value εis larger than the specified value as a result of discrimination, a value (f) preset corresponding to a deviation (%) is multiplied by the PID parameter P×f (P), I×f (I), D×f (D)} (S26) and after wards, the PID operation is performed corresponding to that multiplied value (S27). Control output is operated so that a current flow rate value PV can be kept at a setting flow rate value SV (S28). When the deviation ε is smaller than the specified value, on the other hand, PID control operation is performed corresponding to the deviation (S27). Control output is operated so that the current flow rate value PV can be kept at the setting flow rate value SV (S28).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a PID control method applied to, for example, a flow rate control in which the amount of water supplied from a reservoir to a demand destination is maintained within a predetermined range by adjusting an opening of a water supply valve. It relates to the control controller.

[0002]

2. Description of the Related Art As shown in a time chart of FIG. 5, a conventional general control method of this kind detects a current value PV of a control object at predetermined predetermined cycles, and detects the detected current value PV. And a set value S preset as a target value
The absolute value of the deviation ε (= PV−SV) from V (hereinafter referred to as deviation) is calculated, and when the calculated deviation ε exceeds a dead zone which is an allowable range, the magnitude of the deviation ε A control method has been adopted in which a PID control operation is performed in response to the control signal and a control signal is output to a control target device such as a valve so that the deviation ε converges within a certain allowable range.

[0003]

However, according to the conventional PID control method as described above, when the deviation ε is large, the output time of the control signal, for example, the opening and closing operation of the valve is considered in the case of a water valve. Because the time t becomes longer,
There was a possibility that the amount of water supplied to the demand destination temporarily increased or decreased extremely, causing a water hammer phenomenon.

The present invention has been made in view of the above-described circumstances. Even when the deviation is large, the control output time to the controlled device is kept short to prevent the occurrence of a water hammer phenomenon and the like, and it is appropriate and stable. PID that can perform control
It is an object to provide a control method and a controller for the control.

[0005]

In order to achieve the above object, a PID control method according to the present invention calculates a deviation between a current value detected from a control target and a target set value, and calculates the deviation. Is determined to be greater than or equal to a specified value,
When the difference is equal to or more than the specified value, the PID parameter is multiplied by a value set according to the deviation amount, and then a PID control operation is performed to output a control signal. And performs a PID control operation to output a control signal.

A PID control controller according to the present invention includes a means for detecting a current value of a control object, a means for presetting a target set value, and a means for presetting a detected current value of the control object. Means for calculating a deviation from the set value, and determining means for determining whether or not the calculated deviation is equal to or greater than a specified value. Means for multiplying the PID parameter by a value set accordingly, and the PID parameter according to the multiplied value or, if the absolute value of the deviation is less than a specified value in the determination result, according to the absolute value of the deviation.
And a PID control calculating means for performing a control calculation and outputting a control signal.

According to the present invention having the above-described configuration, a deviation between the detected current value of the control target and a preset set value is calculated, and when the calculated deviation is equal to or greater than a specified value. It is determined whether there is. If the result of the determination indicates that the deviation is equal to or greater than a specified value, a value set in accordance with the deviation amount is multiplied by the PID parameter, and a PID control operation is performed in accordance with the multiplied value. Is output, and if the deviation is less than the specified value in the above determination result, PID control calculation is performed in accordance with the deviation, a control signal is output, and control is performed such that the deviation converges within an allowable range. Do. As a result, when the deviation is larger than the specified value, the output time of the control signal is suppressed to be short, and the occurrence of a bad situation such as a water hammer phenomenon caused by an unduly long operation time of the controlled device such as a valve is suppressed. In addition, appropriate and stable control can always be performed.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a piping system when the PID control method according to the present invention is applied to flow control by opening and closing a water supply valve.

In FIG. 1, reference numeral 1 denotes a water distribution reservoir to which a water supply pipe 2 to a destination of tap water is connected. The water supply pipe 2 is provided with a water supply valve 3 serving as a device to be controlled. A motor 4 for driving and adjusting the opening of the water valve 3 is connected to the water valve 3, and an opening detector 5 for detecting the current opening of the water valve 3 and a difference between the front and rear of the valve 3 are provided. A differential pressure detector 6 for detecting pressure is provided.

Reference numeral 7 denotes a valve controller which receives an opening signal from the opening detector 5 and a differential pressure signal from the differential pressure detector 6 to calculate a current flow value PV, and outputs a control target value. The flow rate set value SV previously set and input to the setting device 8 is input, and the controller 7 performs a control operation at predetermined intervals.

Next, the operation of the flow rate control device for opening and closing the water supply valve having the above configuration will be described with reference to the flowchart shown in FIG. During the control cycle, the flow rate set value SV is read into the controller 7, and the current differential pressure detected by the differential pressure detector 6 and the current opening of the water valve 3 detected by the opening degree detector 5 at that time. The flow rate current value PV obtained by the calculation of the degree is read, and the deviation ε between the read flow set value SV and the flow rate current value PV is calculated (steps S21 to S24).

Next, as shown in FIG. 3, the calculated deviation ε is compared with the specified values (+ A and −A) to determine whether the deviation ε is equal to or more than the specified values (+ A and −A). (Step S25), and when the deviation ε is equal to or greater than the specified value as a result of the determination, as shown in FIG. 4, the deviation amount (%)
After multiplying {P × f (P), I × f (I), and D × f (D)} by the PID parameter with a value f set in advance according to (step S26), PID control calculation is performed (step S27), and the current flow rate value PV
A control output (operating time) is calculated such that is maintained at the flow rate set value SV, and the control signal is output to the motor 4 of the water valve 3 (steps S28 and S2).
9).

On the other hand, if the result of the determination in step S25 indicates that the deviation ε is less than the specified value, the above-described step S26
, The PID control calculation is performed according to the deviation ε (step S27), and the flow rate current value P
A control output (operating time) for maintaining V at the flow rate set value SV is calculated, and the control signal is output to the motor 4 of the water valve 3 (steps S28 and S2).
9).

As described above, when the deviation ε is larger than the specified values (+ A and −A) (the hatched portion in FIG. 3), the PID parameter is multiplied by a value preset according to the deviation. Thereafter, by performing PID control calculation, the control output time of the water valve 3 with respect to the motor 4
That is, since the operation time t of the valve 3 is shortened by Δt as compared with the related art, it is possible to suppress the occurrence of a water hammer phenomenon due to a temporary extreme increase or decrease in the amount of water supplied to a demand destination. The flow rate can always be controlled appropriately and stably.

In the above-described embodiment, the case where the control target device is the water supply valve 3 has been described. However, the present invention can be applied to the control of any control target device other than the above. It is effective.

[0016]

As described above, according to the present invention, when the deviation between the current value and the set value is equal to or greater than the specified value, the PID parameter is multiplied by the value set according to the deviation amount, Since the control signal is output by performing the PID control operation according to the multiplied value, the output time of the control signal when the deviation is larger than the specified value can be reduced, and therefore, the control of the valve and the like can be suppressed. It is possible to suppress the occurrence of a water hammer phenomenon or the like due to the operation time of the target device being unduly lengthened, and it is possible to always perform appropriate and stable control.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a piping system of a flow rate control device for opening and closing a water supply valve to which a PID control method according to the present invention is applied.

FIG. 2 is a flowchart illustrating an operation of the flow control device in the embodiment.

FIG. 3 is a time chart of the above operation.

FIG. 4 is a diagram illustrating an example of a multiplication value of a PID parameter with respect to a deviation in the same operation.

FIG. 5 is a time chart of an operation according to a conventional PID control method.

[Explanation of symbols]

 3 Water supply valve (example of controlled device) 5 Opening detector 6 Differential pressure detector 7 Valve controller PV Flow rate present value SV Flow rate setting value ε Deviation

Claims (2)

[Claims] An absolute value of a deviation between a current value detected from a control target and a target set value is calculated, and it is determined whether or not the absolute value of the deviation is equal to or greater than a specified value. If it is above, after multiplying the PID parameter by a value set in accordance with the deviation amount, a PID control operation is performed and a control signal is output. A PID control operation and outputting a control signal. 2. A means for detecting a current value of a control object, a means for presetting a target set value, and an absolute value of a deviation between the detected current value of the control object and a preset set value. Means for calculating; determining means for determining whether the calculated absolute value of the deviation is greater than or equal to a specified value; PID is set value
Means for multiplying the parameter; and, when the absolute value of the deviation is less than a specified value in the above determination result, performing a PID control operation in accordance with the absolute value of the deviation and outputting a control signal. A PID control controller, comprising: