JP3791289B2 - Proportional motion controller - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a proportional operation controller having means for automatically correcting an offset amount, and more particularly to a proportional operation temperature controller.
[0002]
[Prior art]
As a conventional technology, as a controller for continuously controlling the operation amount of the controlled object, a proportional motion controller (P motion controller), a proportional + integral motion controller (PI motion controller), a proportional + integral + differential motion controller A meter (PID motion controller) is generally used.
Since an offset amount is generally generated in the P operation controller, an operator manually operates and sets a manual reset amount. In particular, when a target value to be controlled is changed or when a process characteristic to be controlled changes, an offset amount is generated. Therefore, the manual reset amount is manipulated each time.
[0003]
For this reason, a controller having an integral operation such as a PI operation controller or a PID operation controller is generally used as a process control controller, and the P operation controller has an extremely large dead time. It has been used relatively limitedly when the stability of the control system is difficult to achieve due to strong non-linear factors.
However, PI and PID controllers with integral operation require adjustment to match the PID parameters to the characteristics of the controlled object, for example, the limit sensitivity method in order to measure the stability of the control system. I need knowledge. These adjustments are generally performed when the plant is started up.
[0004]
[Problems to be solved by the invention]
However, since the thermal time constant of the controlled object is large in furnace temperature control, etc., the control can be stabilized with a high proportional gain, and even when used as a P motion controller, the maximum offset generated is proportional. It falls within 1 / gain (ie proportional band) or less. In view of this point and the point that a control system can be easily and inexpensively constructed, a P-motion controller has been relatively useful. The generated offset amount has been corrected by adjusting the manual reset amount by the operator as necessary.
[0005]
Also, from customers using PI and PID controllers with integral operation, overshoot due to reset windup phenomenon due to integral operation, especially when starting and stopping furnace temperature control such as in batch processes (Fig. 4. Because of the saturation phenomenon of the manipulated variable MV, the problem of the control amount PV overshooting by ΔX from the target value SV at the start of control, or the movement of the control operation is not intuitive, so no specialized knowledge is required There is a demand for the development of a P-motion controller that does not require adjustment of the manual reset amount.
[0006]
The present invention has been made in view of the above points, and an object of the present invention is to provide a proportional motion controller that solves the above-described problems and automatically processes the adjustment of the manual reset amount under a certain condition. It is in.
[0007]
[Means for Solving the Problems]
According to the present invention, the proportional motion controller inputs a control amount from a controlled object, compares the target value of the target value setting means with the control amount, forms a control deviation, and is proportional to the control deviation. A proportional circuit that multiplies the gain, a manual reset circuit that adds a manual reset amount to the control signal of this proportional circuit to form the manipulated variable MV, and a manual reset amount automatically when the controller is in proportional operation. And an automatic MV correction means for correcting the control deviation in the zero direction by correcting the control deviation.
[0008]
The automatic MV correction means includes a first detection means for detecting that the control enters the first steady state and the offset amount is equal to or greater than a predetermined value when the controller is operating as a proportional operation. An integration circuit which is activated by one detection means and inputs a control signal and performs an integration operation in a preset integration time; and the control operation is switched to a proportional + integration operation to control the controlled object, and this control is in the second steady state. And a second detecting means for detecting that the amount of entering offset is corrected to zero.
[0009]
With this configuration, the manual reset amount of the manual reset circuit can be corrected by the second detection unit by the difference between the operation amount in the second steady state and the operation amount in the first steady state, and the integration circuit can be reset. As a result, the newly set manual reset amount can continue the control in a state where the offset amount is close to zero unless a new disturbance occurs in the control target when the control target is operated with this target value. In particular, when the control is a batch process or the like, it is possible to repeatedly perform good control without generating an offset amount.
[0010]
The automatic MV correction means outputs a pulse signal at an interval proportional to the up / down counter instead of the manual reset circuit and the time divided by the control signal obtained by multiplying the integration time by the control gain multiplied by the control gain instead of the integration circuit. And a gate circuit for controlling the pulse signal.
With this configuration, when the control by the first detection means enters the first steady state and the offset amount is greater than or equal to a predetermined value, the output of the pulse transmission circuit is input to the up / down counter and the operation mode of the controller is proportional. + When the integration operation is performed and the control enters the second steady state by the second detection means, the output of the pulse transmission circuit can stop the input to the up / down counter and the operation mode of the controller can be set to the proportional operation. . In this configuration, when the operation mode of the controller changes from the proportional operation to the proportional + integral operation and further returns to the proportional operation, the controller can be switched without changing the operation amount without giving an impact.
[0011]
Further, a selection unit that does not activate the operation of the automatic MV correction unit can be provided.
With such a configuration, when the mode for automatically starting the automatic MV correction unit is selected by the selection unit, when the control enters the first steady state by the first detection unit and the offset amount is equal to or greater than a predetermined value, A manual reset amount correcting operation for automatically correcting the offset amount can be performed. In addition to changing the target value, this correction operation can be effectively performed even for a steady disturbance such as a load fluctuation of the control target.
Further, when the automatic MV correction unit is selected to be stopped by the selection unit, the automatic MV correction unit can be stopped from starting automatically.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a block circuit diagram of a proportional operation controller according to an embodiment of the present invention, FIG. 2 is an explanatory diagram for explaining the operation principle, and FIG. 3 is a block circuit diagram of a proportional operation controller according to another embodiment.
In FIG. 1, a proportional motion controller 1 according to the present invention receives a control amount PV from a control target (not shown), compares the target value SV of the target value setting means 11 with the control amount PV, and calculates a control deviation XW. And a proportional circuit 12 for multiplying the control deviation XW by a proportional gain Kp, a manual reset circuit 26 for adding a manual reset amount BAL to the control signal KpXW of the proportional circuit 12 to form an operation amount MV, and a controller And an automatic MV correction means 2 that automatically corrects the manual reset amount BAL and corrects the control deviation XW in the zero direction when 1 is in proportional operation.
[0013]
This automatic MV correction means 2 is a first detection means for detecting 22b that when the controller 1 is operated as a proportional operation, the control enters the first steady state 22a and the offset amount is equal to or greater than a predetermined value. 22, an integration circuit 24 that is activated by the first detection means 22 and inputs a control signal KpXW to perform an integration operation with a predetermined integration time Ti, and the control object is controlled by switching the control operation to proportional + integration operation The second detection means 23 for detecting that this control has entered the second steady state 23a and the offset amount has been corrected to zero can be provided.
[0014]
With this configuration, the second manual detecting circuit 23 sets the new manual reset amount BAL2 of the manual reset circuit 26 by the difference (MV2−MV1) between the operation amount MV2 in the second steady state 23a and the operation amount MV1 in the first steady state. The manual reset amount is corrected to BAL1, and the integration value of the integration circuit 24 is reset to zero. As a result, when the control target is operated with this target value SV, the newly set manual reset amount BAL2 may continue control with an offset amount close to zero unless a new disturbance occurs in the control target. it can. In particular, when the control is a batch process or the like, it is possible to repeatedly perform good control without generating an offset amount.
[0015]
【Example】
Example 1
The details of the proportional motion controller of the present invention will be further described with reference to FIGS.
The controller according to the present invention is basically provided with a PI operation adjusting unit that performs control by PI operation, is normally controlled by P operation, and the offset amount is constantly generated by the first detection means above a specified value. At this time, the control is switched to the PI operation to correct the offset amount to zero, the manual reset circuit 26 is corrected to the new manual reset amount BAL2, the integration operation is stopped, and the P operation control is restored.
[0016]
FIG. 1 shows an embodiment of such a configuration. In FIG. 1, a P operation adjusting unit inputs a control amount PV from a control target, and a target value setting means 11 (for example, in a digital controller, a numerical value setting by a keyboard or setting by a push button and a counter and display by a display device). Comparing the target value SV with the control amount PV to form a control deviation XW, multiplying the control deviation XW by the proportional gain Kp, and adding the manual reset amount BAL to the control signal KpXW of this proportional circuit 12 And a manual reset circuit 26 that constitutes the operation amount MV.
[0017]
In addition, the PI operation adjusting unit switches the switching control circuit 25 to the above-described P operation adjusting unit when the first detection means 22 is operated, and inputs the control signal KpXW to perform the integration operation with a preset integration time Ti. Is added to the control signal KpXW at the addition point 14 to form a PI operation circuit, and a manual reset amount BAL is added to form an operation amount MV. .
[0018]
The automatic MV correction means 2 monitors the target value SV and the control amount PV or the control deviation XW, and the response time detector 21 for detecting the response time of the control system and the controller 1 are in proportional operation. When the control system enters the first steady state (22a), the first detection means 22 detects (22b) that the offset amount is greater than or equal to a predetermined value, and the control operation is switched to the PI operation to be controlled. The second detection means 23 for detecting that the control enters the second steady state (23a) and the offset amount is corrected to zero, and the integration circuit 24 is constituted by the first detection means 22 and the second detection means 23. And a switching control circuit 25 that rewrites the manual reset amount BAL of the manual reset circuit 26 to a new manual reset amount BAL2.
[0019]
The operation will be described with reference to FIG. In FIG. 2, the horizontal axis is the time axis, the vertical axis of FIG. 2A is the target value SV and the controlled variable PV on the same scale, and the vertical axis of FIG. 2B is the manipulated variable. Now, the target value SV is changed at time t0, or the controller 1 is put into automatic operation by the P operation. Since the deviation between the target value SV and the control amount PV is large, the manipulated variable MV takes the maximum value and is in a saturated state. In this state, when a certain time L has elapsed, the control amount PV changes. Since this fixed time L is used as a condition for determining whether or not the control system, which will be described later, has entered a steady state, it is measured at least at the initial stage of operation start and data is held in the storage circuit. The measurement of the certain time L is measured by the response time detection unit 21 as, for example, the time until the change amount ΔPV of the control amount changes by 5% of the change amount of the target value SV.
[0020]
Then, the rate of change of the control amount PV and the manipulated variable MV decreases at time t1 in the P operation operation, and takes a substantially constant value between times t1 and t2 illustrated by 2L, so that the first steady state 22a is obtained. When it is detected that the offset amount ΔXW at this time is larger than a predetermined threshold value, the first detection means 22 detects the occurrence of steady offset.
[0021]
At time t2, the switching control circuit 25 switches the control operation of the controller 1 to the PI operation. Specifically, the control signal KpXW is input to the integration circuit 24, and the integration output 24a, the control signal KpXW, and the manual reset circuit are input. It is controlled by the sum signal of 26 manual reset amounts BAL1, and the offset amount ΔXW is controlled to be zero. The second detection means 23 detects that the offset amount ΔXW has become substantially zero and has continued for a certain time (for example, 2L), so that the second detection means 23 detects that the second steady state 23a is present, and the switching control circuit 25 And the new manual reset amount BAL2 of the manual reset circuit 26 is corrected to the old manual reset amount BAL1 by the difference (MV2−MV1) between the operation amount MV2 in the second steady state 23a and the operation amount MV1 in the first steady state. The integration value of the integration circuit 24 is reset to zero, and the control operation of the controller 1 is switched again to the P operation.
[0022]
As a result, when the control target is operated with the target value SV, the newly set manual reset amount BAL2 can continue control with the offset amount close to zero as long as no new disturbance occurs in the control target. . In particular, when the control is a batch process or the like, it is possible to repeatedly perform good control without generating an offset amount.
(Example 2)
In FIG. 3, as another embodiment according to the present invention, the automatic MV correction means 2A includes an up / down counter (U / DC) 27 in place of the manual reset circuit 26 in FIG. 1 and an integration time Ti in place of the integration circuit 24. A pulse transmission circuit 24A that outputs a pulse signal having a pulse interval obtained by converting the time obtained by dividing the signal by the control signal KpXW into one pulse of the manipulated variable, and a gate circuit 28 that controls the pulse signal. it can.
[0023]
With this configuration, when the control system enters the first steady state 22a by the first detecting means 22 and the offset amount is equal to or greater than a predetermined threshold value, the output of the pulse transmission circuit 24A is a gate circuit 28 represented by a switch in the illustrated example. To the up / down counter 27, the operation mode of the controller 1 can be set to the proportional + integral operation.
When the control system enters the second steady state 23a by the second detecting means 23, the output of the pulse transmission circuit 24A is blocked by the gate circuit 28 and the input to the up / down counter is stopped to change the operation mode of the controller. Proportional operation can be achieved. In this configuration, when the operation mode of the controller 1 is switched from the proportional operation to the proportional + integral operation and then returned to the proportional operation, this switching operation can be performed simply by controlling the pulse input to the counter 27. It is possible to change the quantity without changing the output OUT.
[0024]
Further, it is possible to provide a selection means 29 shown by a switch 29 that does not activate the operation of the automatic MV correction means 2, 2A.
With this configuration, when the selection unit 29 selects a mode in which the automatic MV correction unit 2 or 2A is automatically activated, the control unit enters the first steady state 22a by the first detection unit 22 and the offset amount ΔXW is determined in advance. When the value is equal to or greater than 22b, a manual reset amount BAL correction operation for automatically correcting the offset amount ΔXW can be performed. In addition to the change of the target value SV, this correction operation can be effectively performed even for a steady disturbance such as a load fluctuation of the control target.
[0025]
Further, when the automatic MV correction means 2 and 2A are selected to be stopped by the selection means 29, the automatic MV correction means 2 and 2A can be stopped from starting automatically.
Further, when the controller 1 of the present invention is configured using, for example, a central processing unit CPU such as a microcomputer and a memory device, the setting means 11, the proportional circuit 12, the addition points 13 and 14, the manual reset circuit 26, Automatic MV correction means 2, 2A, response time detection unit 21, first detection means 22, second detection means 23, integration circuit 24, pulse transmission circuit 24A, switching control circuit 25, up / down counter 27, gate circuit 28 are software Can be processed. Accordingly, in FIG. 1 and FIG. 3, the output unit 15 is illustrated. However, when the output of the controller 1 is, for example, a current output of 4 to 20 mA, the manipulated variable MV data is converted to analog via the digital / analog converter DAC The operation end can be controlled by converting it into a quantity. In electric furnace temperature control, etc., the ON / OFF conduction ratio is controlled using the manipulated variable MV data, and the heating power to the heater is controlled by the ON / OFF ratio control of a control device such as a relay. Can do.
[0026]
【The invention's effect】
As described above, by using the proportional motion controller according to the present invention, it is always used as a proportional motion controller, and only when the offset occurs in a steady state, is switched to the proportional + integral motion controller to correct the offset. It is possible to provide a proportional motion controller that prevents the occurrence of offset by correcting the manual reset amount to the operation amount at the time and returning to the proportional motion controller.
[Brief description of the drawings]
FIG. 1 is a block circuit diagram of a proportional operation controller as one embodiment of the present invention. FIG. 2 is an explanatory diagram for explaining the operation principle. FIG. 3 is a block circuit diagram of a proportional operation controller according to another embodiment. 4] Control characteristics diagram according to the prior art [Explanation of symbols]
1 Proportional motion controller
11 Target value setting method
12 Proportional circuit
13,14 Additional points
15 Output unit 2,2A Automatic MV correction means
21 Response time detector
22 First detection means
22a First steady state detection
22b Offset detection
23 Second detection means
24 Integration circuit
24A pulse generator
25 Switching control circuit
26 Manual reset circuit
27 Up / down counter
28 Gate circuit
29 Selection methods
SV target value
PV control amount
BAL, BAL1, BAL2 Manual reset amount
MV, MV1, MV1 manipulated variable
Kp proportional gain
Ti integration time ΔXW Offset amount L Response time
t0, t1, t2, t3 time

Claims (3)

A control amount from a control target is input, a target value of the target value setting means is compared with the control amount to form a control deviation, and a proportional circuit that multiplies the control deviation by a proportional gain, and a control signal of the proportional circuit In a proportional operation controller comprising a manual reset circuit that configures an operation amount MV by adding a manual reset amount to
Automatic MV correction means that automatically corrects the manual reset amount and corrects the control deviation in the zero direction when the controller is in proportional operation,
The automatic MV correction means includes a first detection means for detecting that the control enters the first steady state and the offset amount is equal to or greater than a predetermined value when the controller is operated as a proportional operation. An integration circuit which is activated by the detection means and inputs a control signal to perform an integration operation with a preset integration time, and the control object is controlled by switching the control operation to proportional + integration operation, and this control enters the second steady state. Second detecting means for detecting that the offset amount has been corrected to zero, and the second detecting means converts the manual reset amount of the manual reset circuit into the second steady state operation amount and the first steady state operation amount. Correct the difference with, and reset the integration circuit,
Proportional motion controller characterized by that. The proportional motion controller according to claim 1,
The automatic MV correction means is a pulse that outputs a pulse signal at intervals proportional to the up / down counter instead of the manual reset circuit and the time divided by the control signal obtained by multiplying the integral time by the control gain and the integral deviation instead of the integrator circuit. A transmission circuit and a gate circuit for controlling the pulse signal;
When the control enters the first steady state by the first detection means and the offset amount is equal to or greater than a predetermined value, the output of the pulse transmission circuit is input to the up / down counter to change the operation mode of the controller to proportional + integral operation. When the control enters the second steady state by the second detection means, the output of the pulse transmission circuit stops the input to the up / down counter and the operation mode of the controller is set to the proportional operation.
Proportional motion controller characterized by that. The proportional motion controller according to claim 1 or 2,
A selection unit that does not activate the operation of the automatic MV correction unit;
Proportional motion controller characterized by that.

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