JPH01158501A - Control device - Google Patents

Abstract

PURPOSE:To automatically set a correct stable manipulated variable without adding the judgement of a user by discriminating the stable condition of a controlled variable obtained prescribed time interval by a detecting means and holding the manipulated variable as a stable manipulated variable. CONSTITUTION:A manipulated variable is calculated by the operation including an integration manipulated variable with a control means 4, given to an output means 3 and the control is executed. Then, a stable condition discriminating means 5 discriminates whether or not the manipulated variable obtained from a detecting means 1 is in a stable control area, and at the time of the stable control condition, the then integrating manipulated variable is written as the stable manipulated variable to a non-volatile storing means 6. At the time of the re-input of the power source, for the then stable manipulated variable, the manipulated variable is calculated by the control means 4 as the initial value of the integrating manipulated variable and the operation is executed by the output means 3. Thus, the stable manipulated variable is automatically updated and the stable manipulated variable with a high accuracy can be set.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a control device that controls a controlled object by operations including an integral operation, and particularly to a control device characterized by setting an initial value of an integral operation.

[Prior art and its problems]

(Prior Art) As a conventional control device for a continuous time controlled object such as a temperature control device, a PID control device that performs PID control is widely used. When starting up a PID control device, the integral operation starts when the proportional band is entered, but if the initial value of the integral operation amount is made equal to the control amount in the steady state, there will be almost no overshoot and a short settling time will be achieved. The controlled object can be stabilized in time. However, if the initial value of the integral manipulated variable is larger than the control amount in the steady state, overshoot will occur, and if it is smaller, the settling time will become longer.

In order to solve this problem, for example, Japanese Patent Application Laid-Open No. 59-8
As shown in No. 001, when a steady state is entered, the manipulated variable at that time is stored as a stable manipulated variable (anti-reset value), and the next time the system is started up, the stable manipulated variable is integrated. A control device is known that improves settling characteristics by using it as an initial value of a manipulated variable.

(Problem to be Solved by the Invention) However, in such a conventional PID control device in which an anti-reset value is set, the user must determine whether or not the controlled object is in a stable control state. Therefore, it is necessary to constantly monitor whether it is in a stable state. Also, since this criterion differs depending on the user,
The value held as the anti-reset value also differs depending on the user.

Moreover, if there is an error in the setting method, the correct value cannot be set. Furthermore, once the anti-reset value has been set, if a permanent disturbance occurs or the characteristics of the system change due to a change in the set value, the previously written anti-reset value will no longer be the optimal value. However, in this case, since the anti-reset value is not changed, there is a drawback that a large overshoot may occur when the power is turned on or the control characteristics may be disturbed.

[Purpose of the invention]

The present invention has been made in view of the problems of conventional control devices that maintain anti-reset values. The technical challenge is to

[Structure and effects of the invention]

(Means for Solving the Problems) The present invention is a control device that controls a controlled object by an operation including an integral operation, and as shown in FIG. , an input means 2 for inputting a target set value, an output means 3 for performing a control operation on the controlled object, and a manipulated variable is determined by an operation including the integral manipulated variable with the stable manipulated variable as an integral initial value based on the set value of the input means. A control means 4 for outputting an output, a stable state determining means 5 for determining a stable control state when the control amount obtained by the predetermined time detecting means is within a stable region, and a stable state determining means 5 for determining a stable state when the stable state determining means determines that a stable state is established. It is characterized by comprising a non-volatile storage means 6 that holds the manipulated variable applied to the controlled object as a stable manipulated variable.

(Operation) According to the present invention having such features, after the start of the operation, the control means calculates the manipulated variable by an operation including the integral manipulated variable, and provides it to the output means to perform control.

At that time, the stable state determining means determines whether the manipulated variable obtained from the detection means is within the stable control region, and if it is in the stable control state, the integral manipulated variable at that time is stored in the nonvolatile storage means as stable. Written as a manipulated variable.

When the power is turned on again, the stable operation amount at that time is used as the initial value of the integral operation amount to calculate the operation amount by the control means, and the output means performs the operation.

(Effects of the Invention) Therefore, according to the present invention, there is no need to determine whether or not the controlled object has reached a stable control state and set a stable operation amount, and the operation amount to be maintained can be written without individual differences. operation becomes unnecessary. If the stable control state is maintained, the stable manipulated variable is automatically updated, so even if a permanent disturbance occurs in the controlled object or the set value is changed, it is possible to set a stable manipulated variable with high accuracy. . Furthermore, since this stable operation amount is written in a non-volatile storage means, its value is retained even when the power is turned off.

Therefore, it is possible to obtain the effect that control is not disrupted when recovering from a power outage.

[Explanation of Examples]

(Configuration of Embodiment) FIG. 2 is a block diagram showing the configuration of a temperature control device according to an embodiment of the present invention. In this figure, temperature control device 10
is assumed to control the temperature of a controlled object 11, for example, an electric furnace, and a detector 12 detects the temperature. An amplifier 13 that amplifies the output of the detector 12, an A/D converter 14 that converts the amplified output into a digital value, and a central processing unit (hereinafter referred to as C
(referred to as pu)15. It has an output operation section 16 which is an output means 3 for heating the heating furnace which is the controlled object 11 according to the operation amount of the CPU 15 . Here, the CPU 15 includes a target value setting device 17 for setting a target value of the controlled variable. A parameter setter 18 is provided for setting PID parameters and stable operation parameters. A numerical display 19 is also provided to display detected temperatures, set values, and the like. The CPU 15 has a read-only memory (hereinafter referred to as ROM) as a storage means.
20. Random access memory (hereinafter referred to as RAM)
21 is connected. Also provided is a backup memory 22 which is a non-volatile storage means 6 that retains predetermined set values even when the power is turned off.

FIG. 3 is a memory map showing the storage contents of the RAM 21 and the backup memory 22. The RAM 21 stores the temperature input value given from the A/D converter 14 at every predetermined sampling time, the deviation e from the target setting value, the PID control operation amount M, the PID control proportional term operation amount Mp, and the differential term operation i.
1Md has an area for storing the integral term manipulated variable Mi, Mio, which is a stable manipulated variable, and the PID parameter of the PID constant.

Set target value, set value, stability area Bs, stability time T
It has areas for storing co, l, and stability time counter Tc, respectively. Here, the backup memory 22 is provided with an area for storing stable operation parameters such as the same stable operation amount Mio, PID parameter, target value set value, stable region Bs and stable time Tco.

(Operation of this embodiment) The control operation by the PID control device is expressed as eM=Kp-e+ΣKi-e+Kd-t, where M is the operation amount and e is the deviation. Here, Kp is a proportional gain, Ki is an integral gain, and Kd is a differential gain. Since the deviation e and de/dt are approximately zero in a stable control state, the above equation becomes as follows.

M=ΣKi −e = Mi.

Here, Mio is an integral value that reaches a stable control state.

Therefore, if this integral value Mio is used as the initial integral value when the power is turned on again and the PID control operation is performed when the power is turned on again, control will be performed to reduce the magnitude of the overshoot that occurred last time, and the control operation will be performed quickly. can be brought to a stable state. In the present invention, this stabilizing operation 1M1o is stored in advance.

Next, the operation of this embodiment will be explained with reference to the flowchart of FIG. 4.5 and the time chart of FIG. 6.

When the operation starts at time tl, first in step 31 it is checked whether the control operation mode is set. If it is not the controlled operation mode, the process proceeds to Step 7 32, where PID parameters and stable operation parameters, that is, the range of the stability region Bs and the stability time counter Tco are inputted. If it is the controlled operation mode, the process advances to step 33 and the temperature of the controlled object 11 is acquired from the A/D converter 14. Then, in step 34, the deviation e from the set target value is calculated, and the process proceeds to step 35, where it is checked whether this deviation is within the proportional band P. If it is not within the proportional band, set the operation iM to 100% as shown in Figure 6 (al, (b)).
If it is within the proportional band, step 37)
Then, the operation amount M of the PID control is calculated as in the previous part based on the set PID parameter. This operation amount M
When the stable manipulated variable Mio is set in advance when calculating the stable manipulated variable Mio, the stable manipulated variable Mio is used as the initial value of the integral manipulated variable. Then, the process proceeds to step 38, where the operation amount is given to the output operation section 16 to heat the controlled object 11, and PID control is performed. Therefore, if the target value is in a sufficiently high temperature range after the power is turned on, the manipulated variable will remain at 100% within a predetermined period, and after that it will gradually decrease until it reaches a steady state, which will result in an approximately constant P■D. The control operation amount is given to the controlled object 11. Here CPU15
In steps 33 to 38, the manipulated variable M is determined by an operation including an integral operation using the stable manipulated variable Mio as an integral initial value using the target value set value and the set PID parameter.
The function of the control means 4 to calculate is achieved. In this way, as shown in FIG. 6(a), the control amount gradually approaches the set target value after the power is turned on.

Now, during operation in such a controlled operation mode, an interrupt process shown in FIG. 5 is executed by an interrupt every predetermined time, for example, every two seconds. When this interrupt processing is started, first in step 41 it is checked whether the deviation e is within a preset stability region Bs. If it is not within this range, the stability time counter Tc is cleared and the process ends. Then, as shown in FIG. 6 (al), time t2
In the interrupt processing after entering the stable region Bs, the process proceeds from step 41 to step 43, where the counter Tc is incremented. The process then proceeds to step 44 to check whether the counter Tc has reached a preset stabilization time Tco, for example 16. If this value has not been reached, the interrupt processing is terminated. and stability time counter T
At time t3 when the count value of c reaches 16, step 44
The process then proceeds to step 45, where the integral manipulated variable Mi at that time is set in the stable manipulated variable storage area Mio. Further, the process proceeds to step 46, where the stable operation amount Mio, PID parameter, target value set value, stable region Bs, and stable time T are determined at this time.
The stable operation parameters of co are set in the backup memory 22. Then, the process proceeds to step 47, where the stabilization time counter Tc is set to the stabilization time TcoO value, and this interrupt processing is ended. Time t4 when this interrupt processing is executed next
Since the deviation e is within the stable region Bs, step 4 is performed again.
Processes 3 to 47 are executed, and the integral operation amount Mi at that time is
is written in the stable operation amount Mio area, and the counter Tc is fixed to the stable time TcoO value.

Therefore, the rule? As long as I-1 is within the stable region Bs, the stable manipulated variable Mio is rewritten every interrupt time and is held in the nonvolatile bank-up memory 22. Here, the CPU 15 achieves the function of the stable state determining means 5 that determines whether the controlled object is in a stable control state in steps 41 to 44.

Next, when the power is turned off and then turned on again, the value of the stable manipulated variable at this time is used as the initial value of the integral, so the controlled object can be controlled to the target value with almost no overshoot, as shown in Figure 7. Can be done. If the controlled object itself changes due to some fluctuation after reaching the stable region, or if the characteristics of the system change due to changes in set values, etc., the integral manipulated variable in the stable state after the change is stored as the stable manipulated variable. , it is possible to control the controlled object using the optimal initial integral value when recovering from a momentary power outage or the like. If the initial value of the integral operation amount is not set, the same curve as shown in FIG. 6(a) will be formed the next time the power is turned on, and an overshoot will occur.

Although this embodiment has been described with respect to a PID control device, the present invention can be applied to other control devices that perform integral operations, such as an I-PD control device.

Further, in this embodiment, the stability region Bs and stability time Tco, which are stable operation parameters, are inputted from the parameter setter 18, but it is also possible to set these values in advance on the apparatus side.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the functional configuration of a control device according to the present invention, FIG. 2 is a block diagram showing the configuration of a temperature control device according to an embodiment of the present invention, and FIG. 3 is a memory map thereof.
FIG. 4 is a flowchart showing the operation of this embodiment, FIG. 5 is a flowchart showing its interrupt processing operation, FIG. 6 is a time chart showing changes in the control amount and operation amount after the start of the operation, and FIG. 7 is a flowchart showing the operation of this embodiment. 5 is a time chart showing the operation when the power is turned on again. 1---1.Detection means 2.....-Manual means 3
----Output means 4---Control means
5-- Stable operation determination means 6-- Storage means 11-- Controlled object 12-- Detector 15-- CPU 16-- Output operation Section 17---Target value setter IL-...
・Parameter setter 21-...-RAM 22
-11111 Backup Memory Patent Applicant Tateishi Electric Co., Ltd. Agent Patent Attorney Yoshiki Okamoto (and 1 other person) Figure 1 Figure 4 Figure 5 Figure 6 Figure 7 Now

Claims (1)

[Claims] (1) A detection means for detecting a controlled variable in a controlled object, an input means for inputting a target set value, an output means for performing a control operation on the controlled object, and integrating a stable manipulated variable based on the set value of the input means. a control means for outputting a manipulated variable by an operation including an integral manipulated variable as an initial value; a stable state determining means for determining a stable control state when the controlled variable obtained by the detecting means is within a stable region for a predetermined period of time; 1. A control device comprising: nonvolatile storage means for retaining a manipulated variable applied to a controlled object as a stable manipulated variable when a stable state is determined by a stable state determining means.