Control system and control method

Abstract

To obtain good control characteristics for a control object having strong nonlinear characteristics.SOLUTION: An industrial PC 1 generates time-series data of a control amount and an operation amount corresponding to an ideal control response, transmits the data of the control amount, and simultaneously transmits data of an operation amount change width calculated from the data of the operation amount. A PID controller 2 is provided with a reception unit 29 which receives a transmitted control amount as a reference set value and receives an operation amount change width as a change width of a feedforward control operation amount, a feedforward addition unit 25 which adds the change width of the feedforward control operation amount to the first operation amount before one control cycle to obtain a second operation amount, a feedback addition unit 26 which calculates the change width of the feedback control operation amount by performing speed-type PID calculation based on the reference set value and the measured value of the control amount and adds the second operation amount to this change width to obtain a first operation amount, and an operation amount output unit 28 which outputs the first operation amount to a control target.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a control system and a control method that uses both feedback control and feedforward control. [Background technology]

[0002] Regarding PID control, a technique for automatically adjusting PID parameters to maintain optimal control performance when a set value SP is changed has been disclosed (see Patent Document 1). This PID parameter adjustment technique is applicable to a temperature regulator, which is a PID controller for controlling temperature. In addition, this is a method for searching for PID parameters so as to follow a target trajectory of a controlled variable PV, and theoretically, this method assumes a controlled object with linear characteristics.

[0003] A linear characteristic is a characteristic in which the relationship between the theoretical manipulated variable MV and the output action to the actual controlled object is linear when the output value of the theoretical manipulated variable MV is 0% to 100% on the horizontal axis of a graph and the output action to the actual controlled object is 0% to 100% on the vertical axis as shown in Fig. 21. However, for example, a slightly nonlinear characteristic (weakly nonlinear characteristic) as shown in Fig. 22 can be applied to the technology disclosed in Patent Document 1 as an allowable range for PID control.

[0004] The method disclosed in Patent Document 1 cannot maintain good PID control performance for a control target with strongly nonlinear characteristics in which the relationship between theory and reality is as shown in Fig. 23. Such strongly nonlinear characteristics appear in temperature control systems that use special electric heaters, or flow control systems or pressure control systems that control fluids with valves.

[0005] 24 to 26 show the results of simulations when the operating amount MV (heater output) is 0% and the controlled amount PV (temperature) is heated to different target temperatures (set values ​​SP) by PID control from a state where the operating amount MV (heater output) is 0% and the controlled amount PV (temperature) is stabilized at 50°C. In these simulations, when heating from 50°C to 150°C as shown in Fig. 24, the PID parameters are adjusted so that the controlled amount PV follows the target temperature.

[0006] Here, when the temperature is raised from 50°C to 250°C as shown in Fig. 25, if the PID parameters are the same as in Fig. 24, the controlled variable PV will fluctuate up and down. Similarly, when the temperature is raised from 50°C to 350°C as shown in Fig. 26, if the PID parameters are the same as in Fig. 24, the controlled variable PV will fluctuate even more up and down. The reason that the controlled variable PV fluctuates up and down is that, as shown in Fig. 27, the theoretical and actual slopes of the manipulated variable MV for maintaining each target temperature in Figs. 24 to 26 (approximately 70% in Fig. 24, approximately 80% in Fig. 25, and approximately 90% in Fig. 26) are different, and the greater the slope, the more likely it is that the controlled variable PV will fluctuate up and down.

[0007] As described above, it is difficult to obtain good control characteristics with PID control, for example, for a control target with strongly nonlinear characteristics. On the other hand, in order to maintain stable and safe control operation, the PID control loop is executed with a PID controller (such as a temperature controller) dedicated to PID calculation, which is also a standard instrumentation concept in industry, especially within manufacturing equipment. In other words, the limitations of PID control must be overcome while maintaining the reasons why PID controllers should be used, and improvements are required. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent No. 4223894 Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention has been made to solve the above-mentioned problems, and has an object to provide a control system and a control method that can obtain good control characteristics for a controlled object having strongly nonlinear characteristics. [Means for solving the problem]

[0010] The control system of the present invention is composed of a host device and a PID controller, the host device includes an ideal response generating unit configured to generate time series data of a controlled variable and time series data of a manipulated variable corresponding to an ideal control response, a memory unit configured to store the time series data of the controlled variable and the time series data of the manipulated variable, and a transmission unit configured to sequentially extract, at a specified timing, data of the controlled variable for each control cycle from the time series data stored in the memory unit and transmit the data to the PID controller, and at the same time, sequentially extract data of the manipulated variable for each control cycle from the time series data stored in the memory unit and transmit data of a manipulated variable change range calculated from the extracted data to the PID controller. The PID controller receives the controlled variable transmitted from the host device as a new value of a reference set value, and transmits the data of the controlled variable change range calculated from the extracted data to the PID controller. a control variable acquisition unit configured to acquire a measured value of a control variable; a feedforward adder configured to calculate a value obtained by adding the change width of the feedforward control control variable received by the receiver to a first control variable one control cycle before as a second control variable; a feedback adder configured to use the reference setting value and the measured value of the control variable as inputs, to calculate a change width of a feedback control control control variable by performing a speed-type PID calculation, and to calculate a value obtained by adding the change width of the feedback control control variable to the second control variable as a new value of the first control variable; and a control variable output unit configured to output the first control variable calculated by the feedback adder to a control target.

[0011] In addition, in one configuration example of the control system of the present invention, the PID controller further includes a limit processing unit configured to output a third manipulated variable obtained by limiting the first manipulated variable calculated by the feedback adder to a value within a range between a manipulated variable upper limit value and a manipulated variable lower limit value, and the transmission unit of the host device transmits, at the specified timing, the manipulated variable upper limit value and the manipulated variable lower limit value, which are assumed to be within an error range of the manipulated variable for each control cycle, to the PID controller together with the control variable data and the manipulated variable change range data, the receiving unit of the PID controller receives the manipulated variable upper limit value and the manipulated variable lower limit value transmitted from the host device as new values ​​to be used in the limit processing unit, and the manipulated variable output unit of the PID controller outputs the third manipulated variable to a control object instead of outputting the first manipulated variable to the control object.

[0012] Furthermore, in one configuration example of the control system of the present invention, when adding the change range of the feedback control operation amount to the second operation amount, the feedback addition unit adds proportional and differential action components of the change range of the feedback control operation amount to the second operation amount, and further adds an integral action component of the change range of the feedback control operation amount to the second operation amount only when the addition result is within a range between the operation amount upper limit value and the operation amount lower limit value. Moreover, in one configuration example of the control system of the present invention, the transmission unit sets a value obtained by adding an upward margin value to the operation amount for each control cycle as the operation amount upper limit value, and sets a value obtained by subtracting a downward margin value from the operation amount for each control cycle as the operation amount lower limit value. In addition, in one configuration example of the control system of the present invention, the ideal response generating unit is characterized in that it generates time series data of controlled variables and time series data of manipulated variables corresponding to an ideal control response by utilizing a virtual controlled object model for reproducing the behavior of the controlled object on a computer.

[0013] Further, a control method of the present invention includes a first step in which a host device generates time series data of a controlled variable and time series data of a manipulated variable corresponding to an ideal control response, a second step in which the host device stores the time series data of the controlled variable and the time series data of the manipulated variable, and a third step in which the host device sequentially extracts data of the controlled variable for each control cycle from the time series data stored in the second step at a specified timing and sequentially transmits the data to a PID controller, and at the same time sequentially extracts data of the manipulated variable for each control cycle from the time series data stored in the second step and sequentially transmits data of a manipulated variable change range calculated from the extracted data to the PID controller, and the PID controller receives the controlled variable transmitted from the host device as a new value of a reference set value and transmits the data of the manipulated variable change range calculated from the extracted data to the PID controller. a fourth step of receiving the measured manipulated variable change range as a new value of the change range of the feedforward control manipulated variable by the PID controller; a fifth step of the PID controller acquiring a measured value of the controlled variable; a sixth step of the PID controller calculating a value obtained by adding the change range of the feedforward control manipulated variable to a first manipulated variable one control cycle ago as a second manipulated variable; a seventh step of the PID controller using the reference set value and the measured value of the controlled variable as inputs to calculate a change range of the feedback control manipulated variable by performing a speed-type PID calculation, and calculating a value obtained by adding the change range of the feedback control manipulated variable to the second manipulated variable as a new value of the first manipulated variable; and an eighth step of the PID controller outputting the first manipulated variable calculated in the seventh step to a control target.

[0014] Moreover, one configuration example of the control method of the present invention further includes a ninth step of outputting a third manipulated variable obtained by limiting the first manipulated variable calculated in the seventh step to a value within a range between an upper manipulated variable value and a lower manipulated variable value, the third step including a step of transmitting, at the specified timing, the manipulated variable upper limit value and the manipulated variable lower limit value assuming an error range of the manipulated variable for each control cycle, together with data on the controlled variable and data on the manipulated variable change range, to the PID controller, the fourth step including a step of receiving the manipulated variable upper limit value and the manipulated variable lower limit value transmitted from the host device as new values ​​to be used in the ninth step, and the eighth step including a step of outputting the third manipulated variable to the control object instead of outputting the first manipulated variable to the control object.

[0015] Furthermore, in one configuration example of the control method of the present invention, the seventh step is characterized in that, when adding the change range of the feedback control operation amount to the second operation amount, the seventh step includes a step of adding proportional and differential action components of the change range of the feedback control operation amount to the second operation amount, and further adding an integral action component of the change range of the feedback control operation amount to the second operation amount only when the addition result is within a range between the operation amount upper limit value and the operation amount lower limit value. Moreover, in one configuration example of the control method of the present invention, the third step is characterized by including a step of setting a value obtained by adding an upward side margin value to the operation amount for each control cycle as the operation amount upper limit value, and setting a value obtained by subtracting a downward side margin value from the operation amount for each control cycle as the operation amount lower limit value. Moreover, in one configuration example of the control method of the present invention, the first step is characterized by including a step of generating time series data of a controlled variable and time series data of a manipulated variable corresponding to an ideal control response by utilizing a virtual controlled object model for reproducing the behavior of the controlled object on a computer. Effect of the Invention

[0016] According to the present invention, by providing an ideal response generating unit, a storage unit, and a transmitting unit in the host device, and providing a receiving unit, a controlled variable acquiring unit, a feedforward adding unit, a feedback adding unit, and a manipulated variable output unit in the PID controller, it is possible to obtain good control characteristics for a controlled object with strongly nonlinear characteristics while efficiently utilizing the PID controller. Also, in the present invention, good control characteristics can be obtained while suppressing an increase in the amount of calculation and memory of the PID controller, so that instrumentation that is easy to maintain stable continuity can be realized. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a block diagram showing a configuration of a control system according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram for explaining communication between an industrial PC and a PID controller according to an embodiment of the present invention, and an outline of calculations in the PID controller. [Diagram 3] FIG. 3 is a flowchart illustrating the operation of the industrial PC according to the embodiment of the present invention. [Figure 4] FIG. 4 is a flowchart illustrating the operation of the PID controller according to the embodiment of the present invention. [Diagram 5] FIG. 5 is a diagram showing changes in the controlled variable and the manipulated variable that correspond to an ideal control response. [Figure 6] FIG. 6 is a diagram showing changes in the controlled variable and the manipulated variable that correspond to an ideal control response. [Figure 7] FIG. 7 is a diagram showing changes in the controlled variable and the manipulated variable that correspond to an ideal control response. [Figure 8] FIG. 8 is a diagram showing the result of executing only feedforward control on a control target with a strong nonlinear characteristic. [Figure 9] FIG. 9 is a diagram showing the result of executing only feedforward control on a control target with a strong nonlinear characteristic. [Figure 10] FIG. 10 is a diagram showing the result of executing only feedforward control on a control target with a strong nonlinear characteristic. [Figure 11]FIG. 11 is a diagram showing a simulation result of the control according to the embodiment of the present invention. [Figure 12] FIG. 12 is a diagram showing a simulation result of the control according to the embodiment of the present invention. [Figure 13] FIG. 13 is a diagram showing a simulation result of the control according to the embodiment of the present invention. [Figure 14] FIG. 14 is a diagram showing a simulation result of the control according to the embodiment of the present invention. [Figure 15] FIG. 15 is a diagram showing a simulation result of the control according to the embodiment of the present invention. [Figure 16] FIG. 16 is a diagram showing a simulation result of the control according to the embodiment of the present invention. [Figure 17] FIG. 17 is a diagram showing a simulation result when limit processing using the manipulated variable upper limit value and the manipulated variable lower limit value is not executed in the embodiment of the present invention. [Figure 18] FIG. 18 is a diagram showing a simulation result when limit processing using the manipulated variable upper limit value and the manipulated variable lower limit value is not executed in the embodiment of the present invention. [Figure 19] FIG. 19 is a diagram showing a simulation result when limit processing using the manipulated variable upper limit value and the manipulated variable lower limit value is not executed in the embodiment of the present invention. [Figure 20] FIG. 20 is a block diagram showing an example of the configuration of a computer that realizes a control system according to an embodiment of the present invention. [Figure 21] FIG. 21 is a diagram for explaining a control target of linear characteristics. [Figure 22] FIG. 22 is a diagram for explaining a control target having weakly nonlinear characteristics. [Figure 23] FIG. 23 is a diagram for explaining a control target having a strongly nonlinear characteristic. [Figure 24] FIG. 24 is a diagram showing a simulation result of PID control for a control target having a strongly nonlinear characteristic. [Diagram 25] FIG. 25 is a diagram showing a simulation result of PID control for a control target having a strongly nonlinear characteristic. [Figure 26] FIG. 26 is a diagram showing a simulation result of PID control for a control target having a strongly nonlinear characteristic. [Figure 27] FIG. 27 is a diagram for explaining the reason why the controlled variable fluctuates up and down in PID control for a controlled object with nonlinear characteristics. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] [Principle of the invention] It is possible to obtain changes in the controlled variable PV and the manipulated variable MV that are close to the ideal control response by using a simulation that uses a controlled object model (a virtual controlled object that reproduces the behavior of the controlled object on a computer based on mathematical formulas such as differential equations) that may include strongly nonlinear characteristics, or by using a control trial that uses an actual controlled object.

[0019] Therefore, if the time series data of the controlled variable PV obtained by simulation or control trial is used as the reference set value SP, and the time series data of the manipulated variable MV is used as the manipulated variable MV_f for feedforward control, it is in principle possible to realize feedback control (PID control) that follows the reference set value SP even for a controlled object with strongly nonlinear characteristics.

[0020] Incidentally, the execution of simulations using the control target model and the storage of numerous time-series data sets assuming various conditions should be performed by an industrial personal computer (IPC) or other device at a higher level than a PID controller (a local controller with limited calculation functions for the purpose of continued stability) such as a temperature regulator, making it necessary to distribute the placement of each function block.

[0021] Therefore, the inventors noticed that temperature controllers generally use a speed-type PID calculation rule because the temperature control itself settles at an arbitrary equilibrium point depending on the heat retention of the device housing. They then came to the conclusion that a configuration having an external input of the manipulated variable change width ΔMV_f is suitable for the temperature controller. By using this configuration as a basis, the amount of calculation and memory of the PID controller (temperature controller, etc.) itself can be reduced as much as possible, making it possible to improve the instrumentation to one that is easy to maintain stable continuity while dealing with strongly nonlinear characteristics.

[0022] [Example] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. This embodiment corresponds to the principle of the invention, but will be described as a configuration in which, in addition to the basic configuration, a function that does not impede stable continuity and is rather preferable is added.

[0023] Fig. 1 is a block diagram showing the configuration of a control system according to this embodiment. The control system comprises an industrial PC 1 (host device) and a PID controller 2. The industrial PC 1 comprises an ideal response generating unit 10 which generates time series data of a controlled variable PV and time series data of a manipulated variable MV corresponding to an ideal control response, a controlled variable change storage unit 11 which stores the time series data of the controlled variable PV, a manipulated variable change storage unit 12 which stores the time series data of the manipulated variable MV, a controlled variable output unit 13 which, at a specified timing, sequentially extracts data of the controlled variable PV for each control period from the time series data stored in the storage unit 11 and sequentially transmits the data to the PID controller 2, and a controlled variable output unit 14 which, at a specified timing, sequentially extracts data of the controlled variable PV for each control period from the time series data stored in the storage unit 12 and transmits the data to the PID controller 2. the control amount MV for each control cycle from the control amount MV output section 14, which sequentially extracts data on the control amount MV for each control cycle from the control amount MV output section 14 and sequentially transmits data on the control amount change width ΔMV calculated from the extracted data to the PID controller 2; a control amount upper limit value output section 15 which transmits a control amount upper limit value OH_x assuming an error range of the control amount MV for each control cycle to the PID controller 2 at a specified timing; and a control amount lower limit value output section 16 which transmits a control amount lower limit value OL_x assuming an error range of the control amount MV for each control cycle to the PID controller 2 at a specified timing.

[0024] The control amount change memory unit 11 and the operation amount change memory unit 12 constitute a memory unit 17, and the control amount output unit 13, the operation amount change range output unit 14, the operation amount upper limit value output unit 15, and the operation amount lower limit value output unit 16 constitute a transmission unit 18.

[0025] The PID controller 2 includes a set value input unit 20 that receives the controlled variable PV transmitted from the industrial PC 1 as a new value of the reference set value SP_r, a controlled variable change range input unit 21 that receives the controlled variable change range ΔMV transmitted from the industrial PC 1 as a new value of the change range ΔMV_f of the feedforward control controlled variable, a controlled variable upper limit value input unit 22 that receives the controlled variable upper limit value OH_x transmitted from the industrial PC 1, a controlled variable lower limit value input unit 23 that receives the controlled variable lower limit value OL_x transmitted from the industrial PC 1, a controlled variable acquisition unit 24 that acquires a measured value of the controlled variable PV, and a controlled variable MV_z (second controlled variable) that is a value obtained by adding the change range ΔMV_f of the feedforward control controlled variable to the controlled variable MV_x' (first controlled variable) one control cycle before. a feedback adder 26 that uses a reference set value SP_r and a measurement value of the controlled variable PV as inputs, performs a speed-type PID calculation to calculate a change range ΔMV_b of the feedback control controlled variable, and calculates a value obtained by adding the change range ΔMV_b of the feedback control controlled variable to the controlled variable MV_z obtained by the feedforward adder 25 as a new value of the controlled variable MV_x'; a limit processing unit 27 that outputs a controlled variable MV (third controlled variable) obtained by limiting the controlled variable MV_x' calculated by the feedback adder 26 to a value within the range between a controlled variable upper limit value OH_x and a controlled variable lower limit value OL_x; and a controlled variable output unit 28 that outputs the controlled variable MV obtained by the limit processing unit 27 to the controlled object.

[0026] The set value input section 20 , the operation amount change range input section 21 , the operation amount upper limit value input section 22 , and the operation amount lower limit value input section 23 constitute a receiving section 29 . The transmitter 18 and the receiver 29 may transmit and receive data via wired communication or wireless communication. The present invention is not limited to a specific communication standard, and any appropriate communication standard may be appropriately selected to realize communication between the industrial PC 1 and the PID controller 2.

[0027] FIG. 2 is a diagram for explaining the communication between the industrial PC 1 and the PID controller 2, and an outline of the calculation in the PID controller 2. FIG.

[0028] The ideal response generating unit 10 of the industrial PC 1 generates data on the time change of the controlled variable PV corresponding to the ideal control response and data on the time change of the manipulated variable MV output to the controlled object at the time of this control response (step S100 in FIG. 3). The ideal response generating unit 10 may search for an optimal solution in a simulation using a controlled object model that may include a strongly nonlinear characteristic, or may issue an automatic trial command for control using an actual controlled object, thereby obtaining a change in the controlled variable PV and a change in the manipulated variable MV that are close to the ideal control response. In the present invention, the method of generating data by the ideal response generating unit 10 is not particularly limited.

[0029] The ideal response generator 10 generates time series data of the controlled variable PV and time series data of the manipulated variable MV for each preset control condition. The control condition usually refers to the condition of changing the set value SP (the set value SP before the change and the set value SP after the change) assumed in the temperature rise control using, for example, the PID controller 2 (temperature regulator).

[0030] The generated time series data of the controlled variable PV and the time series data of the manipulated variable MV each have time information (time stamp) added, with the start time of the control action being time 0. The time interval of the generated time series data is preferably the same as the control period of the PID controller 2, but may be a time interval shorter than the control period.

[0031] The controlled variable change storage unit 11 stores a set of time-series data of the controlled variable PV generated for each control condition by the ideal response generating unit 10 (step S101 in FIG. 3). An ID corresponding to the control condition is added to the data set generated for each control condition by the ideal response generating unit 10. The controlled variable change storage unit 11 stores this ID together with the data set.

[0032] Meanwhile, the manipulated variable change storage unit 12 stores a set of time-series data of the manipulated variable MV generated for each control condition by the ideal response generator 10 (step S102 in FIG. 3). As described above, an ID corresponding to the control condition is added to the data set generated for each control condition by the ideal response generator 10. The manipulated variable change storage unit 12 stores this ID together with the data set.

[0033] The ideal response generator 10 must end data generation when a specified end time has elapsed from the point in time when the controlled variable PV stabilizes after the set value SP is changed. The reason for this is that if data generation continues, the storage capacity of the controlled variable change storage unit 11 and the manipulated variable change storage unit 12 will become enormous.

[0034] Next, at a specified timing (YES in step S103 in FIG. 3), the controlled variable output unit 13 selects a specified data set from the time series data sets of the controlled variable PV stored in the controlled variable change storage unit 11. The controlled variable output unit 13 sequentially extracts data of the controlled variable PV for each control cycle of the PID controller 2 from the selected data set and sequentially transmits the data to the PID controller 2. At this time, the controlled variable output unit 13 transmits the data of the controlled variable PV for each control cycle so that the time interval indicated by the time stamp value of the data sequentially transmitted by the controlled variable output unit 13 matches the control cycle of the PID controller 2 (step S104 in FIG. 3).

[0035] The manipulated variable change width output unit 14 selects a specified data set from the time series data set of the manipulated variable MV stored in the manipulated variable change storage unit 12 at a specified timing. The manipulated variable change width output unit 14 sequentially extracts data of the manipulated variable MV for each control cycle of the PID controller 2 from the selected data set, and sequentially transmits the manipulated variable change width ΔMV per control cycle calculated from the extracted data to the PID controller 2. At this time, the manipulated variable change width output unit 14 transmits data of the manipulated variable change width ΔMV for each control cycle so that the time indicated by the time stamp value of the data of the controlled variable PV transmitted by the controlled variable output unit 13 is the same as the time indicated by the time stamp value of the data transmitted by the manipulated variable change width output unit 14 (step S105 in FIG. 3). As a result, the time interval indicated by the time stamp value of the data sequentially transmitted by the manipulated variable change width output unit 14 coincides with the control cycle of the PID controller 2.

[0036] The manipulated variable change range ΔMV is the difference from the manipulated variable MV one control cycle ago. The manipulated variable change range output unit 14 may calculate the manipulated variable change range ΔMV one by one from the selected data set. For example, if the manipulated variable MV at time t is 0, the manipulated variable MV at time t+1 is 1, the manipulated variable MV at time t+2 is 3, the manipulated variable MV at time t+3 is 4, and the manipulated variable MV at time t+4 is 2, the manipulated variable change range ΔMV at times t, t+1, t+2, t+3, and t+4 can be calculated as ΔMV=0, 1, 2, 1, and -2.

[0037] In addition, if the PID controller 2 has a data buffer, the control amount output unit 13 and the operation amount change range output unit 14 may transmit data on multiple control amounts PV and multiple operation amount MV that can be stored in the data buffer together.

[0038] The manipulated variable upper limit value output unit 15 calculates the manipulated variable upper limit value OH_x assuming an error range of the manipulated variable MV (the manipulated variable MV on which the manipulated variable change range ΔMV is based and has the same time stamp value as the controlled variable PV transmitted by the controlled variable output unit 13) for each control period extracted by the manipulated variable change range output unit 14 from a specified data set at a specified timing. The manipulated variable upper limit value output unit 15 transmits the manipulated variable upper limit value OH_x to the PID controller 2 so that the time indicated by the time stamp value of the data of the controlled variable PV transmitted by the controlled variable output unit 13 is the same as the time indicated by the time stamp value (the time stamp value of the manipulated variable MV extracted from the data set by the manipulated variable change range output unit 14) added to the manipulated variable upper limit value OH_x transmitted by itself (step S106 in FIG. 3). As a result, the time interval indicated by the time stamp value of the data sequentially transmitted by the manipulated variable upper limit value output unit 15 coincides with the control period of the PID controller 2.

[0039] The simplest process is to predefine an upward margin centered on the manipulated variable MV. The manipulated variable upper limit value output unit 15 may transmit, as the manipulated variable upper limit value OH_x, a value obtained by adding the upward margin value to the manipulated variable MV for each control cycle extracted by the manipulated variable change range output unit 14 from a prescribed data set.

[0040] The manipulated variable lower limit output unit 16 calculates the manipulated variable lower limit value OL_x assuming an error range of the manipulated variable MV (the manipulated variable MV on which the manipulated variable change range ΔMV is based and has the same time stamp value as the controlled variable PV transmitted by the controlled variable output unit 13) for each control period extracted by the manipulated variable change range output unit 14 from a specified data set at a specified timing. The manipulated variable lower limit output unit 16 transmits the manipulated variable lower limit value OL_x to the PID controller 2 so that the time indicated by the time stamp value of the data of the controlled variable PV transmitted by the controlled variable output unit 13 is the same as the time indicated by the time stamp value (the time stamp value of the manipulated variable MV extracted from the data set by the manipulated variable change range output unit 14) added to the manipulated variable lower limit value OL_x transmitted by itself (step S107 in FIG. 3). As a result, the time interval indicated by the time stamp value of the data sequentially transmitted by the manipulated variable lower limit output unit 16 coincides with the control period of the PID controller 2.

[0041] The simplest process is to predefine a downward margin centered on the manipulated variable MV. The manipulated variable lower limit value output unit 16 may transmit, as the manipulated variable lower limit value OL_x, a value obtained by subtracting the downward margin value from the manipulated variable MV for each control cycle extracted by the manipulated variable change range output unit 14 from a prescribed data set.

[0042] It is not necessary for the upward margin value and the downward margin value to be fixed values, and as described below, the upward margin value and the downward margin value may each be changed according to the elapsed time from the time when the set value SP was changed.

[0043] The control amount output unit 13, the operation amount change range output unit 14, the operation amount upper limit value output unit 15, and the operation amount lower limit value output unit 16 repeatedly execute the processing of steps S104 to S107 until the specified data sets stored in the control amount change memory unit 11 and the operation amount change memory unit 12 are completely transmitted (YES in step S108 in Figure 3).

[0044] It is desirable for the controlled variable PV, the manipulated variable change range ΔMV, the manipulated variable upper limit OH_x, and the manipulated variable lower limit OL_x, which require data synchronization, i.e., the same time stamp values, to arrive at the PID controller 2 simultaneously, but a time lag in their arrival is acceptable. If this time lag is a small amount of time relative to the control period (e.g., 1 second) of the PID controller 2, there is no practical problem. This completes the operation on the industrial PC 1 side, and the industrial PC 1 waits until the next specified timing.

[0045] Here, the above-mentioned prescribed timing and prescribed data set will be explained. For example, when an operator of the industrial PC 1 manually changes the set value SP of the PID controller 2, the timing when the operator instructs to change the set value SP becomes the prescribed timing, and the data set (control conditions) instructed by the operator becomes the prescribed data set.

[0046] Furthermore, for example, when temperature control of a heating furnace or the like is automatically performed according to predetermined schedule information, the timing of changing the set value SP determined by the schedule information becomes the specified timing, and the data set (control conditions) determined by the schedule information becomes the specified data set.

[0047] Fig. 4 is a flowchart explaining the operation of the PID controller 2. The set value input unit 20 of the PID controller 2 receives the controlled variable PV transmitted from the industrial PC 1 as a new value of the reference set value SP_r (step S200 in Fig. 4). The simplest processing is to receive data of one controlled variable PV for each control cycle of the PID controller 2.

[0048] The manipulated variable change range input unit 21 receives the manipulated variable change range ΔMV transmitted from the industrial PC 1 as a new value of the feedforward control manipulated variable change range ΔMV_f (FIG. 4, step S201). The simplest processing is to receive one data value of the manipulated variable change range ΔMV for each control cycle of the PID controller 2.

[0049] The manipulated variable upper limit input unit 22 receives the manipulated variable upper limit value OH_x transmitted from the industrial PC 1 as a new value to be used in the limit processing unit 27 (step S202 in FIG. 4). The manipulated variable lower limit input unit 23 receives the manipulated variable lower limit value OL_x transmitted from the industrial PC 1 as a new value to be used in the limit processing unit 27 (step S203 in FIG. 4). The initial value of the manipulated variable upper limit value OH_x previously set in the PID controller 2 is 100%, and the initial value of the manipulated variable lower limit value OL_x is 0%.

[0050] In addition, when a data buffer is provided in the PID controller 2, and the control quantity output unit 13, the operating quantity change range output unit 14, the operating quantity upper limit value output unit 15, and the operating quantity lower limit value output unit 16 transmit data on a plurality of control quantities PV, a plurality of operating quantity MV, a plurality of operating quantity upper values ​​OH_x, and a plurality of operating quantity lower limit values ​​OL_x, which can be stored in the data buffer, together, the set value input unit 20, the operating quantity change range input unit 21, the operating quantity upper limit value input unit 22, and the operating quantity lower limit value input unit 23 may extract each of the data on the control quantity PV, the operating quantity change range ΔMV, the operating quantity upper limit value OH_x, and the operating quantity lower limit value OL_x stored in the data buffer one by one for each control period of the PID controller 2.

[0051] The controlled variable acquisition unit 24 acquires a measured value of the controlled variable PV (Step S204 in FIG. 4). In the case of temperature control using the PID controller 2 (temperature regulator), the value of the controlled variable PV is acquired from a temperature sensor.

[0052] Next, as shown in equation (1), the feedforward adder 25 adds the change width ΔMV_f of the feedforward control operation amount received by the operation amount change width input unit 21 to the operation amount MV_x calculated by the feedback adder 26 one control cycle ago (the value of MV_x' one control cycle ago, described later), and sets this value as the operation amount MV_z (step S205 in Figure 4). MV_z = MV_x + ΔMV_f (1)

[0053] The feedback adder 26 receives the reference set value SP_r and the measured value of the controlled variable PV as input, and calculates the change range ΔMV_b of the feedback control manipulated variable by performing a speed-type PID calculation such as the transfer function equation shown in equation (2) so that the measured value of the controlled variable PV matches the reference set value SP_r (step S206 in FIG. 4). ΔMV_b=Kp{ΔEr+(1 / Ti)Er+TdΔ 2 Er} ···(2)

[0054] In formula (2), Er is the control deviation, which is the difference SP_r-PV between the reference set value SP_r and the measured value of the controlled variable PV. ΔEr is the first-order difference of the control deviation Er (the amount of change in the deviation Er per one control cycle), Δ 2 Er is the second difference of the control deviation Er (the amount of change in the deviation Er per control cycle), Kp is the proportional gain of the PID parameters, Ti is the integral time of the PID parameters, and Td is the differential time of the PID parameters. Note that the proportional gain Kp has a relationship with the proportional band Pb of Kp=100 / Pb.

[0055] As shown in equation (3), the feedback adder 26 adds the change width ΔMV_b of the feedback control manipulated variable to the manipulated variable MV_z calculated by the feedforward adder 25, and sets the result as the manipulated variable MV_x' (step S207 in FIG. 4). MV_x' = MV_z + ΔMV_b (3)

[0056] In addition, when the feedback addition unit 26 adds the change width ΔMV_b of the feedback control operation amount to the operation amount MV_z, it preferably performs the addition of the proportional action (P action) and the derivative action (D action) prior to the addition of the integral action (I action), and performs the addition of the integral action when the result of the addition of the proportional action and the derivative action is within the range of the operation amount upper limit value OH_x and the operation amount lower limit value OL_x received by the operation amount upper limit value input unit 22 and the operation amount lower limit value input unit 23, thereby obtaining the effect of anti-reset windup processing (processing to prevent unnecessary accumulation of integral action).

[0057] That is, the component ΔMV_b_pd of the proportional action and the differential action of the change range ΔMV_b of the feedback control manipulated variable is expressed by equation (4), and the component ΔMV_b_i of the integral action (I action) is expressed by equation (5). ΔMV_b_pd=Kp(ΔEr+TdΔ 2 Er) ···(4) ΔMV_b_i = Kp(1 / Ti)Er (5)

[0058] Therefore, the sum MV_z' of the manipulated variable MV_z and ΔMV_b_pd is expressed by equation (6). MV_z' = MV_z + ΔMV_pd (6)

[0059] When the addition result MV_z' is greater than or equal to the operating volume lower limit value OL_x and less than or equal to the operating volume upper limit value OH_x, the feedback addition unit 26 further adds the integral action component ΔMV_b_i of the change range ΔMV_b of the feedback control operating volume to the addition result MV_z', as shown in equation (7), and determines the result as the operating volume MV_x'. MV_x'=MV_z'+ΔMV_b_i ···(7)

[0060] Furthermore, when the addition result MV_z' is less than the manipulated variable lower limit value OL_x or greater than the manipulated variable upper limit value OH_x, the feedback adder 26 does not add ΔMV_b_i, and sets the addition result MV_z' as the manipulated variable MV_x' as it is. MV_x' = MV_z' (8)

[0061] Since the feedforward control operation amount change width ΔMV_f specific to the present invention has already been added by the process of formula (1), the effect of minimizing the amount of calculation required to achieve consistency with the limit process in the subsequent stage can be obtained by the process described in formulas (4) to (8). However, the addition condition of the integral action may be added as appropriate.

[0062] The limit processing unit 27 outputs an operation amount MV obtained by limiting the operation amount MV_x’ calculated by the feedback addition unit 26 to a value that is greater than or equal to the operation amount lower limit value OL_x and less than or equal to the operation amount upper limit value OH_x (step S208 in FIG. 4). That is, when the operation amount MV_x’ is smaller than the operation amount lower limit value OL_x (MV_x’ < OL_x), the limit processing unit 27 sets the operation amount MV = OL_x; when the operation amount MV_x’ is greater than the operation amount upper limit value OH_x (MV_x’ > OH_x), the limit processing unit 27 sets the operation amount MV = OH_x; and when the operation amount MV_x’ is greater than or equal to the operation amount lower limit value OL_x and less than or equal to the operation amount upper limit value OH_x (OL_x ≤ MV_x’ ≤ OH_x), the limit processing unit 27 sets the operation amount MV = MV_x’.

[0063] Normally, limit processing with a standard operation amount upper limit value of 100% and an operation amount lower limit value of 0% for the thermostat is further executed. That is, when the operation amount MV is smaller than the operation amount lower limit value of 0%, the limit processing unit 27 sets the operation amount MV to 0%; when the operation amount MV is greater than the operation amount upper limit value of 100%, the limit processing unit 27 sets the operation amount MV to 100%.

[0064] The operation amount output unit 28 outputs the operation amount MV that has been limit-processed by the limit processing unit 27 to the control target (step S209 in FIG. 4). The output destination of the operation amount MV is an operation unit (not shown) such as a heater or a valve. In the case of a heater, the actual output destination of the operation amount MV is a power regulator (not shown) that supplies power to the heater.

[0065] The PID controller 2 executes the processing of steps S200 to S209 for each control cycle until the control is terminated by a command from an operator (YES in step S210 in FIG. 4).

[0066] However, the set value input unit 20, the operation amount change width input unit 21, the operation amount upper limit value input unit 22, and the operation amount lower limit value input unit 23 stop updating the reference set value SP_r, the change width ΔMV_f of the feedforward control operation amount, the operation amount upper limit value OH_x, and the operation amount lower limit value OL_x when a certain continuous time has elapsed since the measured value of the control amount PV was tuned (YES in step S211 in FIG. 4) (step S212 in FIG. 4).

[0067] As a result, the reference set value SP_r, the change range ΔMV_f of the feedforward control manipulated variable, the manipulated variable upper limit value OH_x, and the manipulated variable lower limit value OL_x are fixed to the values ​​received one control cycle ago. However, the manipulated variable upper limit value input unit 22 may return the manipulated variable upper limit value OH_x to its initial value (100%), and the manipulated variable lower limit value input unit 23 may return the manipulated variable lower limit value OL_x to its initial value (0%).

[0068] The above duration needs to be set so that the updates of the reference set value SP_r, the change range ΔMV_f of the feedforward control manipulated variable, the manipulated variable upper limit value OH_x, and the manipulated variable lower limit value OL_x stop before data transmission from the industrial PC 1 ends.

[0069] Thereafter, the processes of steps S204 to S209 are executed every control period until the next specified timing occurs and the processes of steps S200 to S203 are resumed.

[0070] Next, the effect of this embodiment will be described with reference to an example (simulation) of application to a controlled object with strongly nonlinear characteristics shown in Fig. 23. Here, the ideal response generating unit 10 generates time series data of the controlled variable PV and time series data of the manipulated variable MV that correspond to an ideal control response by a simulation using a controlled object model.

[0071] If the nonlinear characteristic of FIG. 23 is modeled, the manipulated variable MV in the settled state after the temperature rise can be obtained from the model for the temperature rise control shown in FIG. 24 to FIG. 26, so simple data such as those shown in FIG. 5 to FIG. 7 can be generated. FIG. 5 shows the change in the controlled variable PV (temperature) and the change in the manipulated variable MV corresponding to the ideal control response when the temperature is raised from 50°C to 150°C as shown in FIG. 24. FIG. 6 shows the change in the controlled variable PV and the change in the manipulated variable MV corresponding to the ideal control response when the temperature is raised from 50°C to 250°C as shown in FIG. 25. FIG. 7 shows the change in the controlled variable PV and the change in the manipulated variable MV corresponding to the ideal control response when the temperature is raised from 50°C to 350°C as shown in FIG. 26.

[0072] The controlled variable change storage unit 11 stores a set of time series data of the controlled variable PV generated for each control condition by the ideal response generation unit 10. The manipulated variable change storage unit 12 stores a set of time series data of the manipulated variable MV generated for each control condition by the ideal response generation unit 10. An ID corresponding to the control condition is added to the data set generated for each control condition by the ideal response generation unit 10. In the example of Figs. 5 to 7, different IDs are assigned to the data set when the temperature is increased from 50°C to 150°C, the data set when the temperature is increased from 50°C to 250°C, and the data set when the temperature is increased from 50°C to 350°C. 5 to 7, the change in the set value SP is also shown for convenience, but it is not necessary to store the set value SP.

[0073] Here, we will explain practical problems when the changes in the manipulated variable MV shown in Figures 5 to 7 are performed only by feedforward control, that is, when not combined with the feedback control of the PID controller 2. The strongly nonlinear characteristics of the controlled object are generally characteristics that appear when several types of complex characteristics overlap, and do not involve high-precision reproducibility. Therefore, Figures 8 to 10 show the results of performing only feedforward control with a 3% error between the model and the actual object.

[0074] Fig. 8 shows the results of only executing feedforward control when the temperature is raised from 50°C to 150°C. Fig. 9 shows the results of only executing feedforward control when the temperature is raised from 50°C to 250°C. Fig. 10 shows the results of only executing feedforward control when the temperature is raised from 50°C to 350°C. When only feedforward control is executed, an error occurs in the manipulated variable MV in the settled state after the temperature is raised, and it can be seen that an offset remains in the set value SP and the controlled variable PV, as shown in Figs. 8 to 10.

[0075] Next, a case where this embodiment is applied will be described. As shown in Fig. 2, an important feature of this embodiment is that a data set of an ideal control response is stored in the industrial PC 1, and data of the controlled variable PV is transmitted from the upper side as data of the reference set value SP_r of the PID controller 2. Another important feature is that the manipulated variable change range ΔMV is transmitted from the upper side as the change range ΔMV_f of the feedforward control manipulated variable of the PID controller 2 for adaptation to the speed-type PID calculation.

[0076] In the examples of Figures 5 to 7, ΔMV_f = 0.0 except for two instances: the increase in the manipulated variable at time 100 seconds and the decrease in the manipulated variable at time 150 seconds. Although this is almost impossible in reality, if the model error is 0%, the exact same results as in Figures 5 to 7 will be obtained. In other words, feedback control becomes unnecessary.

[0077] Therefore, the error between the controlled object model used in the simulation by the ideal response generating unit 10 and the actual object is set to 5%, and the feedforward control and feedback control are operated simultaneously. As for the feedback control, as shown in Fig. 24 to Fig. 26, unnecessary fluctuations in the manipulated variable MV occur depending on the target temperature, so it is preferable to regulate it by the manipulated variable upper limit value OH_x and the manipulated variable lower limit value OL_x.

[0078] Specifically, up to 150 seconds (50 seconds after the set value SP is changed), the upper margin value and the lower margin value are each set to 10% of the manipulated variable MV of the ideal control response, and after 150 seconds, the upper margin value and the lower margin value are each set to 5%. The results of this embodiment, which includes these processes, are shown in Figures 11 to 16.

[0079] Fig. 11 shows changes in the reference set value SP_r, the measured value of the controlled variable PV, and the controlled variable MV output by the controlled variable output unit 28 when the temperature is raised from 50°C to 150°C. Fig. 12 shows changes in the reference set value SP_r, the measured value of the controlled variable PV, and the controlled variable MV output by the controlled variable output unit 28 when the temperature is raised from 50°C to 250°C. Fig. 13 shows changes in the reference set value SP_r, the measured value of the controlled variable PV, and the controlled variable MV output by the controlled variable output unit 28 when the temperature is raised from 50°C to 350°C.

[0080] Fig. 14 shows changes in the manipulated variable MV, manipulated variable upper limit value OH_x, and manipulated variable lower limit value OL_x output by the manipulated variable output unit 28 when the temperature is raised from 50°C to 150°C. Fig. 15 shows changes in the manipulated variable MV, manipulated variable upper limit value OH_x, and manipulated variable lower limit value OL_x output by the manipulated variable output unit 28 when the temperature is raised from 50°C to 250°C. Fig. 16 shows changes in the manipulated variable MV, manipulated variable upper limit value OH_x, and manipulated variable lower limit value OL_x output by the manipulated variable output unit 28 when the temperature is raised from 50°C to 350°C.

[0081] 11 to 16, this embodiment can also handle control objects with strongly nonlinear characteristics, and the amount of calculation and memory required by the PID controller 2 itself is reduced as much as possible, making it possible to realize instrumentation that is easy to maintain stable continuity.

[0082] For reference, the results when limit processing using the manipulated variable upper limit value OH_x and the manipulated variable lower limit value OL_x is not executed are shown in Figures 17 to 19. Since there is no effect of regulation by limit processing, more unnecessary up and down fluctuations due to the strong nonlinear characteristics of the controlled object occur than in the cases of Figures 11 to 16, but a significantly improved control response is obtained compared to Figures 24 to 26.

[0083] In this way, the limit processing unit 27 is not an essential component of the present invention. If the limit processing unit 27 is not provided, the manipulated variable output unit 28 outputs the manipulated variable MV_x' calculated by the feedback adder 26 to the control target. If the limit processing unit 27 is not provided, it becomes unnecessary to transmit the manipulated variable upper limit value OH_x and the manipulated variable lower limit value OL_x from the industrial PC 1, and the anti-reset windup process described in equations (4) to (8) will not be executed.

[0084] The industrial PC 1 and the PID controller 2 described in this embodiment can each be realized by a computer equipped with a CPU (Central Processing Unit), a storage device, and an interface, and a program that controls these hardware resources. An example of the configuration of this computer is shown in FIG.

[0085] The computer includes a CPU 200, a storage device 201, and an interface device (I / F) 202. In the case of the industrial PC 1, the I / F 202 is connected to hardware of a communication circuit for communication with the PID controller 2, etc. In the case of the PID controller 2, the I / F 202 is connected to a sensor that measures the controlled variable PV, hardware of a communication circuit for communication with the industrial PC 1, a power regulator, etc. In such a computer, a program for realizing the control method of the present invention is stored in the storage device 201. The CPU 200 of each of the industrial PC 1 and the PID controller 2 executes the processing described in this embodiment according to the program stored in the storage device 201. [Industrial Applicability]

[0086] The present invention can be applied to a control system. [Explanation of symbols]

[0087] 1...industrial PC, 2...PID controller, 10...ideal response generation unit, 11...controlled variable change memory unit, 12...operated variable change memory unit, 13...controlled variable output unit, 14...operated variable change range output unit, 15...operated variable upper limit value output unit, 16...operated variable lower limit value output unit, 17...memory unit, 18...transmission unit, 20...set value input unit, 21...operated variable change range input unit, 22...operated variable upper limit value input unit, 23...operated variable lower limit value input unit, 24...controlled variable acquisition unit, 25...feedforward addition unit, 26...feedback addition unit, 27...limit processing unit, 28...operated variable output unit, 29...receiving unit.

Claims

1. It is composed of a host device and a PID controller, The host device includes: an ideal response generating unit configured to generate time series data of a controlled variable and time series data of a manipulated variable corresponding to an ideal control response; A storage unit configured to store time series data of the controlled variable and time series data of the manipulated variable; a transmission unit configured to sequentially retrieve controlled variable data for each control cycle from the time series data stored in the storage unit and sequentially transmit the data to the PID controller at a specified timing, and simultaneously sequentially retrieve manipulated variable data for each control cycle from the time series data stored in the storage unit and sequentially transmit manipulated variable change range data calculated from the retrieved data to the PID controller, The PID controller is a receiving unit configured to receive the control amount transmitted from the host device as a new value of a reference set value and to receive the manipulated variable change range transmitted from the host device as a new value of a change range of a feedforward control manipulated variable; A control variable acquisition unit configured to acquire a measurement value of a control variable; a feedforward adder configured to calculate, as a second manipulated variable, a value obtained by adding a change width of the feedforward control manipulated variable received by the receiver to a first manipulated variable from one control cycle before; a feedback adder configured to receive the reference set value and a measured value of the controlled variable, perform a speed-type PID calculation to calculate a change width of a feedback control manipulated variable, and calculate a value obtained by adding the change width of the feedback control manipulated variable to the second manipulated variable as a new value of the first manipulated variable; a manipulated variable output unit configured to output the first manipulated variable calculated by the feedback adder to a controlled object.

2. 2. The control system of claim 1, the PID controller further includes a limit processing unit configured to output a third manipulated variable obtained by limiting the first manipulated variable calculated by the feedback adder to a value within a range between an manipulated variable upper limit value and an manipulated variable lower limit value, the transmission unit of the host device transmits, at the specified timing, the manipulated variable upper limit value and the manipulated variable lower limit value assuming an error range of the manipulated variable for each control cycle, together with the data of the controlled variable and the data of the manipulated variable change range, to the PID controller; the receiving unit of the PID controller receives the manipulated variable upper limit value and the manipulated variable lower limit value transmitted from the host device as new values ​​to be used in the limit processing unit, The control system according to claim 1, wherein the manipulated variable output unit of the PID controller outputs the third manipulated variable to a control object, instead of outputting the first manipulated variable to the control object.

3. 3. The control system of claim 2, the feedback adder, when adding the change range of the feedback control operation amount to the second operation amount, adds proportional and differential action components of the change range of the feedback control operation amount to the second operation amount, and only when a result of the addition is within a range between the operation amount upper limit value and the operation amount lower limit value, further adds an integral action component of the change range of the feedback control operation amount to the second operation amount.

4. 3. The control system of claim 2, a control system characterized in that the transmission unit sets the manipulated variable upper limit value to a value obtained by adding an upward margin value to the manipulated variable for each control cycle, and sets the manipulated variable lower limit value to a value obtained by subtracting a downward margin value from the manipulated variable for each control cycle.

5. A control system according to any one of claims 1 to 4, The ideal response generating unit generates time series data of a controlled variable and time series data of a manipulated variable corresponding to an ideal control response by utilizing a virtual controlled object model for reproducing the behavior of the controlled object on a computer.

6. A first step in which a host device generates time series data of a controlled variable and time series data of a manipulated variable corresponding to an ideal control response; a second step in which the host device stores time series data of the controlled variable and time series data of the manipulated variable; a third step in which the host device, at a specified timing, sequentially extracts data of a controlled variable for each control cycle from the time series data stored in the second step and sequentially transmits the data to the PID controller, and simultaneously sequentially extracts data of an operation variable for each control cycle from the time series data stored in the second step and sequentially transmits data of an operation variable change range calculated from the extracted data to the PID controller; a fourth step in which the PID controller receives the controlled variable transmitted from the host device as a new value of a reference set value and receives the manipulated variable change range transmitted from the host device as a new value of a change range of a feedforward control manipulated variable; a fifth step of the PID controller acquiring a measured value of a controlled variable; a sixth step in which the PID controller calculates, as a second manipulated variable, a value obtained by adding a change width of the feedforward control manipulated variable to a first manipulated variable one control cycle before; a seventh step in which the PID controller performs a speed-type PID calculation using the reference set value and the measured value of the controlled variable as inputs to calculate a change range of a feedback control manipulated variable, and calculates a value obtained by adding the change range of the feedback control manipulated variable to the second manipulated variable as a new value of the first manipulated variable; and an eighth step of the PID controller outputting the first manipulated variable calculated in the seventh step to a controlled object.

7. 7. The control method according to claim 6, a ninth step of outputting a third manipulated variable obtained by limiting the first manipulated variable calculated in the seventh step to a value within a range between an manipulated variable upper limit value and an manipulated variable lower limit value, the third step includes a step of transmitting, at the specified timing, the manipulated variable upper limit value and the manipulated variable lower limit value assuming an error range of the manipulated variable for each control cycle, together with data of the controlled variable and data of the manipulated variable change range, to the PID controller; the fourth step includes a step of receiving the operation amount upper limit value and the operation amount lower limit value transmitted from the host device as new values ​​to be used in the ninth step; The control method according to claim 8, further comprising the step of outputting the third manipulated variable to a control target, instead of outputting the first manipulated variable to the control target.

8. 8. The control method according to claim 7, the seventh step includes a step of adding, when adding the change range of the feedback control operation amount to the second operation amount, a proportional action component and a differential action component of the change range of the feedback control operation amount to the second operation amount, and further adding a component of an integral action component of the change range of the feedback control operation amount to the second operation amount only when the addition result is within a range between the operation amount upper limit value and the operation amount lower limit value.

9. 8. The control method according to claim 7, the third step including a step of setting a value obtained by adding an upward side margin value to the manipulated variable for each control cycle as the manipulated variable upper limit value, and setting a value obtained by subtracting a downward side margin value from the manipulated variable for each control cycle as the manipulated variable lower limit value.

10. 10. The control method according to claim 6, a control method characterized in that the first step includes a step of generating time series data of a controlled variable and time series data of a manipulated variable corresponding to an ideal control response by utilizing a virtual controlled object model for reproducing the behavior of the controlled object on a computer.

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