Control device and control method

Abstract

To provide a control device that is able to inhibit overshoot.SOLUTION: A control device 1, by which an amount of control of a control object 13 is changed by an amount of operation to make the amount of control equal to a target value, includes: first control means 4a that executes control at least two times in ascending order of an intermediate target value so that the amount of control reaches at least two intermediate target values smaller than the target value; first calculation means 4b that calculates, as an average amount of operation, an average value of amounts of operation within a predetermined time after the amount of control reaches the intermediate target values due to the first control means 4a; second calculation means 4c that, based on the average amount of operation calculated by the first calculation means 4b, calculates an estimated amount of operation when the amount of control reaches the target value; and second control means 4d that executes control using the estimated amount of operation.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a control device and a control method for controlling physical quantities such as temperature, flow rate, humidity, and pressure of a controlled object such as an electric furnace, a flow rate system, or a chemical reaction system to target values. [Background technology]

[0002] For example, in an electric furnace, a regulator is generally known as a control device that compares the temperature inside the furnace with a target value and performs calculations according to the deviation to control a heating means such as a heater.

[0003] Incidentally, digital controllers are equipped with an auto-tuning function that automatically calculates and sets the PID constants according to the controlled object.This auto-tuning function employs the limit cycle method, in which the controller is temporarily used as an on-off controller, and the manipulated variable is alternately output at 100% and 0% by on / off operation, and the PID constants are calculated from the period and amplitude of the hunting that occurs in the controlled object.

[0004] As the above-mentioned limit cycle method, the present applicant has proposed a control device that determines a PID constant from a cycling (limit cycle) waveform near a set value and determines a manipulated variable, as disclosed in the following Patent Document 1. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 7-13608 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the above-mentioned limit cycle method, if the PID constants are not appropriately determined, a phenomenon called overshooting occurs in which the controlled variable exceeds the target value. When this overshooting occurs, excessive stress is applied to the controlled object (e.g., manufactured products), which causes a problem of a decrease in yield, and therefore there is a need to suppress the overshooting.

[0007] Therefore, the present invention has been made in consideration of the above problems, and an object of the present invention is to provide a control device and a control method capable of suppressing overshoot. [Means for solving the problem]

[0008] In order to achieve the above object, a control device according to a first aspect of the present invention is a control device that changes a control amount of a control target according to an operation amount, and causes the control amount to coincide with a target value, PID control is performed at least twice in order of increasing intermediate target values ​​so that the controlled variable reaches at least two intermediate target values ​​that are set smaller than the target value, and the PID control is performed after the controlled variable reaches the intermediate target value. The first step until stability A first control means that continues for a predetermined time; After the control amount for each of the PID controls by the first control means has reached the intermediate target value, 1. A first calculation means for calculating an average value of an operation amount within a predetermined time as an average operation amount; a second calculation means for calculating a manipulation amount corresponding to the target value on an approximation line of a function formula created from an average manipulation amount for each of the PID control calculated by the first calculation means, as an estimated manipulation amount when the controlled amount reaches the target value; A second control means for performing control using the estimated manipulated variable; The second control means Second a third control means for finely adjusting the manipulated variable so that the controlled variable coincides with the target value after performing control for a predetermined time; The present invention is characterized by comprising:

[0010] Claim 2The control device according to claim 1 In the control device, The fine adjustment control is characterized in that it is integral control.

[0011] The control method according to claim 3 is a control method for changing a control amount of a control target according to an operation amount to make the control amount coincide with a target value, PID control is performed at least twice in order of increasing intermediate target values ​​so that the controlled variable reaches at least two intermediate target values ​​that are set smaller than the target value, and the PID control is performed after the controlled variable reaches the intermediate target value. The first step until stability continuing for a predetermined time; After the control amount for each PID control reaches the intermediate target value, 1. calculating an average value of the operation amount within a predetermined time as an average operation amount; calculating a manipulated variable corresponding to the target value on an approximation line of a function equation created from the average manipulated variable for each of the PID controls as an estimated manipulated variable when the controlled variable reaches the target value; performing control using the estimated manipulated variable; A manipulated variable corresponding to the target value on the approximation line is Second a step of finely adjusting and controlling the manipulated variable so that the controlled variable coincides with the target value after performing control for a predetermined time; The present invention is characterized by comprising:

[0013] Claim 4 The control method described in claim 3 In the control method of The fine adjustment control is characterized in that it is integral control. Effect of the Invention

[0014] According to the present invention, after an estimated manipulated variable corresponding to a target value is calculated and controlled, the manipulated variable is fine-tuned so that the controlled variable coincides with the target value, thereby making it possible to suppress overshoot. [Brief description of the drawings]

[0015] [Figure 1] 1 is a block diagram showing a schematic configuration of a control device according to the present invention; [Diagram 2] FIG. 2 is a diagram showing an example of a timing chart of tuning and control by the control device and control method according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0017] As shown in FIG. 1, the control device 1 of this embodiment is a regulator that uses physical quantities such as temperature, flow rate, humidity, and pressure of a control object, such as an electric furnace, a flow rate system, or a chemical reaction system, as control quantities, and changes this control quantity according to an operation quantity to match the control quantity with a target value, and is generally configured with an operation display unit 2, a memory unit 3, and a control unit 4 as components for performing tuning and control.

[0018] Here, as shown in FIG. 1, the control target is an electric furnace 13 having a heating means 11 such as a heater and a temperature sensor 12 installed inside the furnace, and the heating means 11 is controlled by driving an actuator (not shown) with a manipulated variable MV so that the furnace temperature detected by the temperature sensor 12 (controlled variable PV) coincides with a target temperature (target value SV).

[0019] The operation and display unit 2 is equipped with various keys provided on the front of the device, and displays such as LCD and LED. The operation and display unit 2 issues an instruction to start tuning, sets the PID constant at the start of tuning, the target value SV, multiple intermediate target values ​​(for example, an intermediate target value SV1 with a load factor of 60% and an intermediate target value SV2 with a load factor of 80% with respect to the target value SV), and predetermined times T1, T2, and T3 (described later). In addition to displaying the setting screen, the operation and display unit 2 also displays the target value SV and the controlled variable PV, various data such as program patterns, and various monitor displays such as bar graphs and trends.

[0020] The memory unit 3 stores various information related to the control of the furnace temperature of the electric furnace 13, including the setting values ​​(PID constants, target value SV, intermediate target values ​​SV1, SV2, specified times T1, T2, T3) set by operating the operation display unit 2, the estimated operating volume MV3 described later, and the approximation line according to equation (1).

[0021] The control unit 4 comprehensively controls the control device 1 based on the set values ​​set by operating the operation display unit 2, various information stored in the memory unit 3, and the temperature inside the electric furnace detected by the temperature sensor 12 of the electric furnace 13. The control unit 4 includes a first control means 4a, a first calculation means 4b, and a second calculation means 4c as components for performing tuning, and includes a second control means 4d and a third control means 4e as components for performing control to adjust the controlled variable PV so that it coincides with the target value SV.

[0022] The first control means 4a controls the heating means 11 by driving the actuator with the manipulated variable MV in the order of increasing intermediate target values ​​so that the controlled variable PV reaches a plurality of intermediate target values ​​set by operation of the operation display unit 2.

[0023] Specifically, for example, when an intermediate target value SV1 with a load factor of 60% and an intermediate target value SV2 with a load factor of 80% are set for the target value SV, the first control means 4a first drives the actuator with the manipulated variable MV to PID-control the heating means 11 so that the temperature (controlled variable PV) of the temperature sensor 12 of the electric furnace 13 reaches the intermediate target value SV1 with a load factor of 60%. After that, the first control means 4a drives the actuator with the manipulated variable MV to PID-control the heating means 11 so that the temperature (controlled variable PV) of the temperature sensor 12 of the electric furnace 13 reaches the intermediate target value SV2 with a load factor of 80%. Note that the control of the heating means 11 by driving the actuator is not limited to PID control.

[0024] The first calculation means 4b calculates, as an average manipulated variable, an average value of the manipulated variables MV within a predetermined time after the controlled variables PV reach their respective intermediate target values ​​by the first control means 4a.

[0025] Specifically, for example, when an intermediate target value SV1 with a load rate of 60% and an intermediate target value SV2 with a load rate of 80% are set with respect to the target value SV, the first calculation means 4b calculates, as the average operated amount MV1, the average value of the operated amount MV within a predetermined time T1 after the controlled amount PV reaches the intermediate target value SV1 with a load rate of 60% with respect to the target value SV. Also, the first calculation means 4b calculates, as the average operated amount MV2, the average value of the operated amount MV within a predetermined time T2 after the controlled amount PV reaches the intermediate target value SV2 with a load rate of 80% with respect to the target value SV.

[0026] The predetermined time T1 is set to the time until the controlled variable PV reaches an intermediate target value SV1 with a load factor of 60% relative to the target value SV and stabilizes, and the predetermined time T2 is set to the time until the controlled variable PV reaches an intermediate target value SV2 with a load factor of 80% relative to the target value SV and stabilizes.

[0027] The second calculation means 4c calculates the manipulated variable MV corresponding to the target value SV on the approximation line based on the average manipulated variable calculated by the first calculation means 4b, as an estimated manipulated variable when the controlled variable PV reaches the target value SV.

[0028] Specifically, for example, when an intermediate target value SV1 with a load factor of 60% and an intermediate target value SV2 with a load factor of 80% are set for the target value SV, the second calculation means 4c creates a linear function formula (1): y = 5 (MV2-MV1) x + MV2-4 (MV2-MV1) from the two average operation amounts MV1 and MV2 calculated by the first calculation means 4b. This linear function formula (1) is created by substituting a = 5 (MV2-MV1) and b = MV2-4 (MV2-MV1) into y = ax + b when the two average operation amounts MV1 = 0.6 × a + b and MV2 = 0.8 × a + b. Then, the operation amount MV corresponding to the target value SV on the approximation line according to this linear function formula (1) is calculated as the estimated operation amount MV3 when the controlled variable PV reaches the target value SV.

[0029] The above-mentioned approximation line is expressed by the equation (1) of a linear function created from the two average operation amounts MV1 and MV2, but is not limited to the equation (1) of a linear function. For example, when three or more intermediate target values ​​are set, the accuracy can be further improved by using an approximation line expressed by a quadratic function created from these three or more intermediate target values.

[0030] The second control means 4d controls the heating means 11 by driving the actuator with the estimated manipulated variable MV3 based on the fixed value calculated by the second calculation means 4c.

[0031] After the second control means 4d controls the heating means 11 with the estimated operation amount MV3 for a predetermined time T3, the third control means 4e fine-tunes the operation amount MV by integral control in addition to the estimated operation amount MV3 so that the control amount PV coincides with the target value SV, and drives the actuator to control the heating means 11.

[0032] Next, the tuning and control method performed by the control device 1 configured as above will be described with reference to FIG.

[0033] First, the PID constants are arbitrarily set by operating the operation display unit 2, and the target value SV, the manipulated variable MV, and the intermediate target value are set. Here, as the intermediate target values, a load factor of 60% of the target value SV is set as the intermediate target value SV1, and a load factor of 80% of the target value SV is set as the intermediate target value SV2.

[0034] After completing the above settings, when tuning is started by operating the operation display unit 2, the first control means 4a of the control unit 4 drives the actuator with the manipulated variable MV to PID-control the heating means 11 so that the temperature inside the electric furnace 13 reaches an intermediate target value SV1=0.6×SV[%] with a load factor of 60% of the target value SV, as shown in section (A) of Fig. 2. This PID control sets the manipulated variable MV by the controlled variable PV, and continues for a predetermined time T1 after the controlled variable PV reaches the intermediate target value SV1.

[0035] Then, the first calculation means 4b of the control unit 4 calculates the average value of the manipulated variable MV within a predetermined time T1 after the controlled variable PV reaches the intermediate target value SV1 as the average manipulated variable MV1. Specifically, if the number of samples in the predetermined time T1 is n1, the average manipulated variable MV1 is calculated as Σ(MVn1) / n1[%].

[0036] Next, the first control means 4a of the control unit 4 drives the actuator with the manipulated variable MV to PID-control the heating means 11 so that the temperature inside the electric furnace 13 reaches an intermediate target value SV2=0.8×SV[%] with a load factor of 80% of the target value SV, as shown in section (b) of Fig. 2. This PID control sets the manipulated variable MV based on the controlled variable PV, and continues for a predetermined time T2 after the controlled variable PV reaches the intermediate target value SV2.

[0037] Then, the first calculation means 4b of the control unit 4 calculates the average value of the manipulated variable MV within a predetermined time T2 after the controlled variable PV reaches the intermediate target value SV2 as the average manipulated variable MV2. Specifically, if the number of samples in the predetermined time T2 is n2, the average manipulated variable MV2 is calculated as Σ(MVn2) / n2[%].

[0038] Next, the second calculation means 4c of the control unit 4 creates an approximation line of a linear function from the average manipulated variables MV1 and MV2. Specifically, if MV1=0.6×a+b and MV2=0.8×a+b, then a=5(MV2-MV1) and b=MV2-4(MV2-MV1). These a and b are substituted into y=ax+b to create an approximation line of the linear function equation (1) consisting of y=5(MV2-MV1)x+MV2-4(MV2-MV1).

[0039] Then, the second calculation means 4c of the control unit 4 calculates the operation amount MV corresponding to the target value SV on the approximation line according to the created linear function equation (1) as the estimated operation amount MV3 when the controlled amount PV reaches the target value SV. That is, according to the linear function equation (1), the estimated operation amount MV3=5(MV2-MV1)+MV2-4(MV2-MV1)[%] is obtained, and therefore the average operation amounts MV1 and MV2 calculated by the first calculation means 4b are substituted to calculate the estimated operation amount MV3.

[0040] Then, the second control means 4d of the control unit 4 continues to output the operation amount MV as the estimated operation amount MV3 for a predetermined time T3, as shown in section (c) of Figure 2, and drives the actuator with the estimated operation amount MV3 to control the heating means 11.

[0041] Furthermore, as shown in section (d) of Fig. 2, when the control based on the estimated manipulated variable MV3 has elapsed for a predetermined time T3, the third control means 4e of the control unit 4 starts integral control in addition to the estimated manipulated variable MV3, thereby performing fine adjustment control of the manipulated variable MV. This executes control so that the controlled variable PV coincides with the target value SV while suppressing overshooting.

[0042] Incidentally, in the above-mentioned embodiment, the tuning and control of a control device that controls the temperature inside the electric furnace 13 to the target value SV has been described as an example of a controlled object, but the present invention is not limited to this. For example, the present invention can be used as tuning and control of a control device that controls physical quantities such as flow rate, humidity, and pressure in a flow rate system or a chemical reaction system to target values.

[0043] As described above, according to the present embodiment, after an estimated manipulated variable corresponding to a target value is calculated and controlled through tuning and control, the manipulated variable is fine-tuned so that the controlled variable coincides with the target value. This makes it possible to suppress overshooting and perform tuning and control without the controlled variable exceeding the target value.

[0044] Although the best mode of the control device and control method according to the present invention has been described above, the present invention is not limited by the description and drawings of this mode. In other words, all other modes, examples, and operation techniques made by those skilled in the art based on this mode are naturally included in the scope of the present invention. [Explanation of symbols]

[0045] 1 Control device 2 Operation display section 3 Storage section 4. Control Unit 4a First control means 4b First calculation means 4c Second calculation means 4d Second control means 4e Third control means 11 Heating means 12 Temperature Sensor 13 Electric furnace (control object)

Claims

1. A control device that changes a control amount of a control target according to an operation amount to make the control amount coincide with a target value, a first control means for performing PID control at least twice in order of increasing intermediate target values ​​so that the controlled variable reaches at least two intermediate target values ​​that are set smaller than the target value, and for continuing the PID control for a first predetermined time until the controlled variable becomes stable after reaching the intermediate target values; a first calculation means for calculating an average manipulated variable as an average manipulated variable within the first predetermined time after the controlled variable for each of the PID control by the first control means has reached the intermediate target value; a second calculation means for calculating a manipulation amount corresponding to the target value on an approximation line of a function equation created from an average manipulation amount for each of the PID control calculated by the first calculation means, as an estimated manipulation amount when the controlled amount reaches the target value; A second control means for performing control using the estimated manipulated variable; a third control means for finely adjusting the manipulated variable so that the controlled variable coincides with the target value after the second control means has performed control for a second predetermined time; A control device comprising:

2. 2. The control device according to claim 1, wherein the fine adjustment control is integral control.

3. A control method for changing a control amount of a control target based on an operation amount to make the control amount coincide with a target value, comprising the steps of: performing PID control at least twice in order of increasing intermediate target values ​​so that the controlled variable reaches at least two intermediate target values ​​that are set smaller than the target value, and continuing the PID control for a first predetermined time until the controlled variable is stabilized after reaching the intermediate target values; calculating an average value of an operation amount within the first predetermined time after the control amount for each of the PID control has reached the intermediate target value as an average operation amount; calculating a manipulated variable corresponding to the target value on an approximation line of a function equation created from the average manipulated variable for each of the PID control as an estimated manipulated variable when the controlled variable reaches the target value; performing control using the estimated manipulated variable; a step of performing control for a second predetermined time with a manipulated variable corresponding to the target value on the approximation line, and then fine-tuning the manipulated variable so that the controlled variable coincides with the target value; A control method comprising:

4. 4. The method of claim 3, wherein the fine-tuning control is integral control.

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