JPH05282006A - Position proportional controller - Google Patents

Abstract

PURPOSE:To obtain the position proportional controller which is small in the ON/OFF frequency of a relay and good in process controllability. CONSTITUTION:When an open-side relay 6 and a closed-side relay 7 are turned on and off to drive a motor 4 and a valve 3 is opened and closed by this motor 4, the rate of variation in manipulated variable indicating opening and closure is detected and the blind sector a1, and operation gaps b1, b2, and b22 of each relay are corrected according to the detection result. Consequently, the life of the relay is prolonged and the process controllability is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position-proportional control controller used for driving and controlling a motor for opening / closing a valve etc. by ON / OFF controlling an open side relay and a close side relay. is there.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram showing a process control system when a temperature control of a process 2 is performed using a conventional position proportional control controller 1. In the figure, a process 2 is heated by burning a fuel such as gas supplied through a valve 3. The valve 3 is controlled to open / close by a motor 4 such as a modtrol motor via a link mechanism or the like. The motor 4 is controlled in forward / reverse rotation by an open side relay 6 as a first relay and a close side relay 7 as a second relay which are turned on / off by an opening / closing operation control section 5 in the position proportional control controller 1. As a result, the valve 3 is operated to the open side or the closed side. The opening degree of the valve 3 by the motor 4 is detected by the opening degree sensor 8 provided in the motor 4. The detected opening is input to the opening input processing circuit 9, sampled at a predetermined cycle, and input to the opening / closing operation control unit 5.

On the other hand, the temperature of the process 2 is measured by the temperature sensor 10.
The temperature input processing circuit 1 detects the detected temperature.
1 is input, sampled at a predetermined cycle, and added to the PID control circuit 12. The PID control circuit 12 has a temperature P
A predetermined P / I / D calculation process is performed using V and the temperature target value SP set by the temperature target setter 13 to manipulate the manipulated variable MV.
Is sent to the opening / closing operation control unit 5.

Based on the MV and the opening, the opening / closing operation controller 5 opens the relay 6 so that the MV becomes equal to the opening.
Alternatively, by controlling ON / OFF of the closing side relay 7,
Control is performed to keep the temperature of the process 2 substantially constant.

FIG. 4 shows a method of controlling the open side relay 6 and the close side relay 7 by the opening / closing operation control section 5. Each relay 6,7
Is turned on / off when the deviation MFB between the opening degree and the manipulated variable MV exceeds a certain value, but a certain dead zone a with respect to the MFB.
0 is set. Within this a0, each relay 6,
An open side dead zone a1 and a closed side dead zone a2 for 7 are set, and normally a1 = a2 = a0 / 2.
Further, constant operation gaps b1 and b2 (= b1) when the relays 6 and 7 are turned from ON to OFF are set.

The relays 6 and 7 are controlled as follows. Open-side relay 6 ON when opening -MV <-a0 / 2 Open-MV> -a0 / 2 + b1 OFF When closed-side relay 7 Open-MV> a0 / 2 ON opening- OFF when MV <a0 / 2-b2 Except for the above, neither ON nor OFF is applied to the open side and the closed side.

Next, the operation of a concrete example will be described. If left open for a long time with constant opening, process 2
It is assumed that the relationship between the temperature PV and the opening is as follows.

[0008]

[Table 1]

Now, set the target value SP = 600 ° C. and P
-It is assumed that the I and D constants are set to values suitable for the process system, PV is substantially equal to SP, and PI is
Both MV and opening degree by D calculation are 61%,
It shall be in a stable control state.

Now, when PV rises and exceeds SP, M
Although V drops slowly, there is a dead zone a0, so the opening is not corrected immediately and remains at 61%. P
Since V remains higher than SP, MV further decreases, and when the difference MFB between MV and the opening exceeds 1/2 of the dead zone a0, the closing relay 7 is turned on to correct the opening. Become. Since the opening degree up to that time is 61%, if the dead zone is 4%, the closing side relay 7 is turned on when the MV is 59%, and if the dead zone is 10%, the closing side relay is turned on when the MV is 56%. In either case, when the opening degree coincides with MV, the closing side relay 7 is turned from ON to OFF, and the opening degree correction is completed.

Since the current opening is too small for PV = SP, PV starts to drop. PV <SP,
Even if the MV rises, there is a dead zone, so the opening is not corrected immediately. If the dead zone is 4% and the opening is 59%, MV
When it reaches 61%, the open side relay 6 is turned on. If the dead zone is 10% and the opening degree is 56%, the open-side relay 6 is turned on when the MV becomes 61%. In both cases, when the opening degree matches MV, the open-side relay 6 turns from ON to OFF.

The above operation is repeated, but PV is SP
Since it takes time until the opening is actually corrected after it becomes larger or smaller, the PV further rises or falls during this period, and the value of PV fluctuates. In that case, the larger the dead zone a0, the larger the degree of correction of the opening degree, and the larger the amplitude of the waviness of PV.

[0013]

Since the control by the conventional position proportional control controller 1 is performed as described above, if the setting of the dead zone a0 is small, the difference between the operation amount MV and the opening becomes small. As a result, the controllability of the process 2 is improved, but the open-side relay 6 and the close-side relay 7 are frequently turned on and off, and the life of the relay is shortened. On the contrary, if the dead zone is set to a large value, the ON / OFF frequency of the open side relay 6 and the close side relay 7 becomes low, and the life of the relay becomes long, but the process value causes hunting in proportion to the dead zone, and It becomes a phenomenon.

If the operating gaps b1 and b2 are set too small, the opening easily goes out of the dead zone again due to a small change in MV after the opening enters the dead zone and the relay is turned off. The ON / OFF frequency of the relay increases and the life of the relay shortens. On the other hand, if the operating gaps b1 and b2 are set too large, the condition that the relay remains on and the dead zone is sufficiently large or the sampling cycle is sufficiently short is satisfied even though the opening is in the dead zone. If it is not, the opening will pass the dead zone and the relay on the opposite side will be easily turned on repeatedly, the on / off frequency of the relay will increase and the life of the relay will be shortened.

In order to improve the process controllability and prolong the life of the relay, it is effective to set the dead band to be small by setting the sampling period short and set the operation gap to be large, but to shorten the sampling period. Has a limit.
Therefore, at present, the settings of the dead zone and the operating gap are determined by a compromise between controllability and process controllability.

The present invention has been made in order to solve the above problems, and reduces the ON / OFF frequency of the relay when the manipulated variable is suddenly changed, without shortening the sampling period, to operate the relay. An object of the present invention is to provide a position proportional control controller capable of improving the controllability of the process when the amount is changing slowly.

[0017]

The position proportional control controller according to the present invention is adapted to change the dead zone and the width of the operation gap according to the change rate dMV of the manipulated variable MV.

[0018]

When the manipulated variable MV is decreasing, the open side dead zone a1 is enlarged and the closing side operation gap b2 is enlarged, and when the MV is increasing, the close side dead zone a2 is increased.
And the open side operation gap b1 are increased, the ON / OFF frequency of the relay is reduced and the process controllability is improved.

[0019]

[Embodiment] In this embodiment, in the opening / closing operation control unit 5,
The rate of change dMV of the manipulated variable MV (the speed at which MV changes) is detected, and the dead zones a1 on the open side and the closed side are detected according to this dMV.
The operation gaps a1 and the open and closed operation gaps b1 and b2 are corrected in the following cases. Here, α: dead zone correction coefficient (α>
0), β: Operating clearance correction coefficient due to MV change (β>
0), b11: open side operation gap in which b1 is corrected, b22:
Let b2 be the closed side operation gap corrected.

When dMV = 0 (when there is no change in MV) a1 = a0 / 2 a2 = a0 / 2 b1 = b2 That is, the same control as in FIG. 4 described above is performed.

When dMV <0 (when MV is decreasing) a1 = (1 / 2-αdMV) a0 a2 = a0 / 2 b11 = b1 b22 = (1-βdMV) b2

That is, as shown in FIG. 1, the open side dead zone a1
To the negative side to make it difficult for the open side relay 6 to turn on, and to increase the close side operation gap b22 to increase the close side relay 7
Makes it difficult to turn off. The larger | dMV |, the dead zone a
1 and the rate of expansion of the closing side operation gap b22 also increase.

When dMV> 0 (when MV is increasing) a1 = a0 / 2 a2 = (1/2 + αdMV) a0 b11 = (1 + βdMV) b1 b22 = b2

That is, as shown in FIG. 2, the closing side dead zone a2
To the positive side to make it difficult for the closing side relay 7 to turn on, and to increase the opening side operation gap b11 to increase the opening side relay 6
Makes it difficult to turn off. The larger | dMV |, the dead zone a
2 and the expansion rate of the open side operation gap b11 also increase.

[0025]

According to the present invention, the dead zone on the open side / closed side and the operation gap are changed according to the change of the operation amount, so that the process controllability can be improved without particularly shortening the sampling cycle. The effect is improved and the life of the relay can be extended.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a control operation of a position proportional control controller according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of another control operation of the controller.

FIG. 3 is a block diagram of a process control system using a conventional position proportional control controller.

FIG. 4 is an explanatory diagram of a control operation of the controller.

[Explanation of symbols]

 1 Position proportional control controller 4 Motor 5 Open / close operation control unit (correction means) 6 Open side relay (first relay) 7 Closed side relay (second relay) MV operation amount dMV Change rate of operation amount MFB Deviation a1 Open Side dead zone a2 Closed side dead zone b1, b11 Open side operation gap b2, b22 Closed side operation gap

Claims (1)

[Claims] 1. A first relay and a second relay are turned on.
In the position proportional control control valve that controls the drive of the motor 4 by performing the off control so that the drive amount of the motor and the operation amount MV for instructing the drive amount are substantially the same, the rate of change of the operation amount is Accordingly, the position proportional control controller is provided with a correction means for correcting the dead zone and the operation gap of the first and second relays.