JPH06131001A - Controller - Google Patents

Abstract

PURPOSE:To provide the controller which lowers an initial set value, and can reduce an overshoot, etc. CONSTITUTION:A target set value SV is inputted, an initial set value SVO being lower than this set value SV is generated, a set value signal SV' which becomes the target set value SV as the lapse of time is generated by a set value generating means 1, this set value signal SV' and a measured value PV from a control object 3 are compared and a control signal MV is generated by a control means 2, and an overshoot, etc., are prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a controller for controlling a process amount such as temperature of a controlled object.

[0002]

2. Description of the Related Art PID represented by feedback control
When performing constant value control or program control,
Normally, a target set value is directly input to perform PID control or the like.

[0003]

However, the PID
There was a problem that overshooting and undershooting to some extent could not be avoided only by control, and cycling was likely to occur.

SUMMARY OF THE INVENTION In view of the above points, an object of the present invention is to provide a control device in which an initial set value is set low to reduce overshoot and the like.

[0005]

SUMMARY OF THE INVENTION According to the present invention, a target set value is input, an initial set value lower than the target set value is generated, and the set value signal becomes the target set value over time. And a control means for generating a control signal by comparing a set value signal of the set value generating means with a measured value from a controlled object.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a structural explanatory view showing an embodiment of the present invention.

In the figure, 1 is a set value generating means for inputting a target set value SV and performing a predetermined calculation to generate a set value signal SV '. 2 is a set value S of the set value generating means 2.
V ′ is compared with the measured value PV of the controlled variable of the controlled object 3 to obtain P
It is a control means that performs ID calculation and the like to generate a control signal MV in the controlled object 3 and control it. Further, in the set value generating means 1, in order to calculate an optimum PID constant or the like for the controlled object 1, it is determined from the time until the measured value rises by giving a step signal to the controlled object 3 by the control means 2 or the like. Waste time L,
Parameters such as the time constant T obtained from the time required to reach a predetermined measurement value are input. Note that the on / off control may be performed to determine the dead time L, the time constant T, etc. from the cycling.

Next, a diagram showing a change of the set value signal PV 'in FIG. 2 with respect to time t will be described.

The set value generating means 1 sets a target set value S
When V is input, as shown in FIG. 2, a set value signal SV0 lower than the target set value PV is generated at time t = 0, and the set value SV becomes the target set value SV over time. The signal SV 'is generated.

Here, if the time to reach the target value SV is t1, it may be defined as a function t1 = f (T) (1) of the time constant T such as t1 = T or 2T.

The initial set value PV0 is set to a value close to the target set value SV (waveform A when the waste time L of the controlled object 1 is small, because overshooting and damping are difficult when the waste time L is small). ), When the dead time L is large, it is easy to overshoot and dump, so
The control is performed with a value (waveform B) far from the target set value SV. For example, the initial measured value at t = 0 is PV0, and the initial set value SV0 is, for example, SV0 = SV- (SV-PV0) .L / T (2) SV0 = SV- (SV-PV0) g ( L) (3) If defined as a function of the dead time L, the initial set value SV0 becomes a value far closer than the target set value SV according to the magnitude of the waste time. L / T = 1, g (L) =
In 1, the equations (2) and (3) are SV0 = PV0.

If the target set value SV is linearly reached at time t1 from the initial set value SV0, the set value signal SV is expressed by the following expression using the expression (1).

SV ′ = [(SV−SV0) / t1] t + SV0 (4) SV ′ = (SV−PV0) g (L) t / f (T) + SV0 (5) Thus, the set value generating means 1 And the parameters (T, L
Etc.), the set value SV ′ that gradually reaches the target value SV from the initial set value SV0 lower than the target value SV is generated by using the initial measured value PV0 and the like, and is used for control. There are few undershoots,
In addition, there is little damping and the like, and a good control result is obtained.

In the above equations (2) and (3), g
The upper and lower initial set values SV0 by (L) etc. and the time to be the target value by f (T) in the equation (1) can be arbitrarily selected. It may be a non-linear function (waveform C) like an expression.

SV ′ = (SV−PV0) h (L, T, t) + SV0 (6) where h (L, T, t) is an arbitrary function. The above arithmetic control and the like may be executed by a microcomputer or the like.

[0016]

As described above, according to the present invention, the control device is designed to set the target set value with the lapse of time from the initial set value lower than the target set value. It is possible to prevent such problems, reduce damping, and perform highly accurate control.

[Brief description of drawings]

FIG. 1 is a structural explanatory view showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram of signals of set values according to the present invention.

[Explanation of symbols]

 1 set value generating means 2 control means 3 controlled object SV target set value SV 'set value signal PV measured value MV control signal

Claims (1)

[Claims] 1. Set value generating means for inputting a target set value, generating an initial set value lower than the target set value, and generating a set value signal which becomes the target set value over time. A control device comprising: a control means for generating a control signal by comparing a set value signal of the set value generating means with a measured value from a controlled object.