Control device, control method, and program

Abstract

To make a control amount of a controlled object follow a target value even when an unknown disturbance exists, while effectively utilizing an existing controller.SOLUTION: A control device according to one aspect is a control device disposed between a higher-level control device that outputs a first target value for a control amount of a controlled object and a lower-level control device that controls the controlled object in accordance with a given second target value, and includes: a model parameter estimation unit that estimates parameters of a closed-loop response model that models the response of closed-loop control consisting of the lower-level control device and the controlled object based on the control amount and the second target value; a target value conversion unit that calculates a third target value by converting the first target value so that the control amount asymptotically approaches the first control amount based on the first target value, the second target value, and the parameters; and a switching unit that outputs either the first target value or the third target value to the lower-level control device as the next second target value.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a control device, a control method, and a program. [Background technology]

[0002] Various control methods, such as PID (Proportional Integral Differential) control and model predictive control, are known as control methods that aim to make the controlled variable of a controlled object follow a target value. Furthermore, a technique called a reference governor is known as a technology related to these control methods (Non-Patent Document 1). The reference governor is a technology that adjusts a target value in advance so that the manipulated variable or state variable of a control system satisfies a predetermined constraint condition. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Takeshi Hatanaka, Joji Takaba, "Integrated Design of Reference Governor and Preview Control", Transactions of the Institute of Systems, Control and Information Engineers, Vol.18, No.1, pp.39-41, 2005. Summary of the Invention [Problem to be solved by the invention]

[0004] When controlling a controlled object using an existing controller that uses PID control, etc., unknown disturbances can cause the controlled variable to deviate from the target value. While introducing advanced controllers that use model predictive control, etc., is an option, such implementation is costly. Therefore, there is a need for technology that can effectively utilize existing controllers while allowing the controlled variable to track the target value even in the presence of unknown disturbances.

[0005] The present disclosure has been made in consideration of the above points, and aims to provide a technology that can make effective use of existing controllers and cause the control variable of a controlled object to follow a target value even when an unknown disturbance is present. [Means for solving the problem]

[0006] A control device according to one embodiment of the present disclosure is a control device arranged between a higher-level control device that outputs a first target value for a control amount of a controlled object and a lower-level control device that controls the controlled object according to a given second target value, and includes: a model parameter estimation unit that estimates parameters of a closed-loop response model that models the response of a closed-loop control consisting of the lower-level control device and the controlled object based on the control amount and the second target value; a target value conversion unit that calculates a third target value by converting the first target value based on the first target value, the second target value, and the parameters so that the controlled amount asymptotically approaches the first target value; and a switching unit that outputs either the first target value or the third target value to the lower-level control device as the next second target value. [Effects of the Invention]

[0007] It is possible to make the control amount of the controlled object follow the target value even when an unknown disturbance exists, while effectively utilizing an existing controller. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a diagram illustrating an example of a hardware configuration of a control device according to the first embodiment. [Figure 2] FIG. 2 is a diagram illustrating an example of a functional configuration of a control device according to the first embodiment. [Figure 3] FIG. 2 is a diagram illustrating an example of a detailed functional configuration of a target value conversion unit according to the first embodiment. [Figure 4] FIG. 10 is a diagram for explaining an example of the operation of a closed-loop response function. [Figure 5] FIG. 10 is a diagram illustrating an example of a functional configuration of a control device according to a second embodiment. [Figure 6] FIG. 10 is a diagram illustrating an example of a detailed functional configuration of a target value conversion unit according to a second embodiment. [Figure 7] 10A and 10B are diagrams for explaining an example of the operation of a high-speed complement control unit; [Figure 8] FIG. 1 is a diagram illustrating an example of the configuration of a conventional control system. [Figure 9] FIG. 1 is a diagram illustrating an example of a configuration of a control system including a control device according to an embodiment. [Figure 10] FIG. 1 is a diagram illustrating a configuration of a control system according to an embodiment. [Figure 11] FIG. 10 is a diagram (part 1) showing the results of an implementation using only a PID controller. [Figure 12] FIG. 10 is a diagram (part 1) showing an implementation result when the control device according to the first embodiment is used. [Figure 13] FIG. 10 is a diagram (part 1) showing an implementation result when the control device according to the second embodiment is used. [Figure 14] FIG. 1 is a diagram (part 1) showing the estimation results of model parameters. [Figure 15] FIG. 10 is a diagram (part 2) showing the results of an implementation using only a PID controller. [Figure 16] FIG. 10 is a diagram (part 2) showing the results of an implementation using the control device according to the first embodiment. [Figure 17] FIG. 10 is a diagram (part 2) showing the results of an implementation using the control device according to the second embodiment. [Figure 18] FIG. 10 is a diagram (part 2) showing the estimation results of model parameters. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, each embodiment of the present invention will be described in detail with reference to the drawings. A control device 10 will be described below that can make the control amount of a control object follow a target value even when an unknown disturbance is present, while effectively utilizing an existing controller. Hereinafter, a control device that controls a control object using a predetermined control method (e.g., PID control) is assumed as the existing controller, and will be referred to as a "lower-level control device 20." Also, hereinafter, a plant is assumed as the control object, and will be referred to as a "controlled plant 30." However, the control object is not limited to a plant, and any device, equipment, facility, etc. can be the control object.

[0010] The lower-level control device 20 calculates and outputs a manipulated variable u for the controlled plant 30 so that the controlled variable y of the controlled plant 30 follows a given target value r. As a result, the controlled plant 30 is controlled according to the manipulated variable u, and a new controlled variable y is obtained. This type of control is called "closed-loop control" or simply "closed loop." However, in general, in plant control, disturbances v occur due to factors such as changes in the environment, changes in devices, equipment, facilities, etc., and changes in raw materials, and the influence of these disturbances v can cause the controlled variable y to deviate from the target value r. In other words, the controlled variable y of the controlled plant 30 is affected not only by the manipulated variable u but also by unknown disturbances v, so the controlled variable y can deviate from the target value r.

[0011] Note that the disturbance v may or may not be measurable using a measuring instrument or the like. Even if the disturbance v can be measured, it may only be measured once or several times a day. For this reason, it is often difficult to suppress the influence of the unknown disturbance v by, for example, adjusting the parameters of the lower-level control device 20 (e.g., adjusting the parameters of PID control). That is, for example, when suppressing the influence of the unknown disturbance v by adjusting the parameters of the lower-level control device 20, there is no guarantee that the influence of the disturbance v can be suppressed with a single parameter adjustment, and the parameters may need to be readjusted multiple times. On the other hand, for example, suppressing the influence of the disturbance v by introducing an advanced controller using model predictive control or the like instead of the lower-level control device 20 requires identification of a process model, modification of the controller and field wiring, adjustment testing, and the like, which requires significant costs. Furthermore, for example, installing a new sensor or the like to measure the unknown disturbance v or increasing the measurement frequency also requires additional costs.

[0012] Therefore, in the control device 10 according to each of the following embodiments, a given target value (hereinafter, this target value will be referred to as "initial target value r0") is converted using the controlled variable y of the controlled plant 30, and either this converted target value or the initial target value r0 is output to the lower-level control device 20. This makes it possible to suppress the influence of an unknown disturbance v, for example, without adjusting the parameters of the lower-level control device 20. In the following, the target value converted from the initial target value r0 will be referred to as the "converted target value r0". m ", and the target value output to the lower-level control device 20 is called "applied target value r1."

[0013] [First embodiment] The first embodiment will be described below.

[0014] <Example of Hardware Configuration of Control Device 10 According to First Embodiment> An example of the hardware configuration of the control device 10 according to the first embodiment will be described with reference to Fig. 1. Fig. 1 is a diagram showing an example of the hardware configuration of the control device 10 according to the first embodiment.

[0015] 1, the control device 10 according to the first embodiment includes an input device 101, a display device 102, an external I / F 103, a communication I / F 104, a processor 105, and a memory device 106. These pieces of hardware are connected to each other via a bus 107 so as to be able to communicate with each other.

[0016] The input device 101 is, for example, a touch panel, various physical buttons, etc. The display device 102 is, for example, a display panel, etc. Note that the control device 10 does not necessarily have to include at least one of the input device 101 and the display device 102, for example.

[0017] The external I / F 103 is an interface with an external device such as a recording medium 103a, etc. Examples of the recording medium 103a include an SD memory card (Secure Digital memory card) and a USB (Universal Serial Bus) memory card.

[0018] The communication I / F 104 is an interface for connecting the control device 10 to a communication network. The processor 105 is, for example, various types of arithmetic devices such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). The memory device 106 is, for example, various types of storage devices such as an SSD (Solid State Drive), RAM (Random Access Memory), ROM (Read Only Memory), and flash memory.

[0019] 1 is an example, and the control device 10 may have other hardware configurations. For example, the control device 10 may have various hardware components other than the hardware components shown in the figure.

[0020] <Example of functional configuration of the control device 10 according to the first embodiment> An example of the functional configuration of the control device 10 according to the first embodiment will be described with reference to Fig. 2. Fig. 2 is a diagram showing an example of the functional configuration of the control device 10 according to the first embodiment.

[0021] 2, the control device 10 according to the first embodiment includes a target value conversion unit 111, a model parameter estimation unit 112, a switch 113, and a timer 114. These components are realized, for example, by a process in which one or more programs installed in the control device 10 are executed by a processor 105 or the like, or by dedicated hardware or the like. Here, an initial target value r0 is given to the control device 10 according to the first embodiment from a higher-level control device (for example, a process computer, an operator terminal, or the like).

[0022] Hereinafter, when the time t representing continuous time is specified, the time t of the initial target value r0 will be expressed as r0(t). Similarly, when the time t is specified for other variables, "(t)" will be written after the variable. Note that the initial target value r0(t) may or may not be constant.

[0023] The timer 114 is set to the main control period T c The main control period T c The main control period T c The value of is preset.

[0024] The target value conversion unit 111 converts the target value into a main control period T c For each time, the initial target value r0(t) at the current time t, the controlled variable y(t) at the current time t, the target variable width w, and the model parameter estimated value θ est (t) and the application target value r1(t) at the current time t are input, and the conversion target value r m (t) is output. The conversion target value r mis a target value obtained by converting the initial target value r0 so that the target deviation e0 (described later) approaches (approaches) 0. Also, the model parameter estimate θ est is the plant response function {S θ (t)}. θ (t)} is a function representing a closed-loop response model that models the response of closed-loop control configured by the lower-level control device 20 and the controlled plant 30.

[0025] The plant response function {S θ (t)} includes the model parameter θ. Hereinafter, the plant response function {S θ (t)} is called the closed-loop response function {S θ (t)}. Also, the closed-loop response function {S θ The model parameter θ set in {(t)} is also called the "model parameter setting value θ."

[0026] The model parameter estimation unit 112 estimates the main control period T c For each time, the control amount y(t) at the current time t and the application target value r1(t) at the current time t are input, and the model parameter estimate θ est The initial value of the model parameter θ may be a zero vector, a value representing a unit step response, or any other initial value.

[0027] The switch 113 selects the initial target value r0(t) at the current time t or the conversion target value r m (t) at the next time t+T c The target value r1(t+T c ) to the lower-level control device 20. Note that the initial target value r0 or the conversion target value r m It is possible to determine in various ways which of the following values ​​is output as the application target value r1. For example, the initial target value r0 or the conversion target value r mEither of these may be output as the application target value r1, or if the target deviation e0 is greater than a certain value, the conversion target value r m Otherwise, the initial target value r0 may be output as the applied target value r1. m In other time periods, the initial target value r0 may be output as the applied target value r1, or if certain conditions are met, the converted target value r m If not, the initial target value r0 may be output as the applied target value r1.

[0028] As described above, the control device 10 according to the first embodiment performs the main control period T c After acquiring the control amount y of the controlled plant 30, the model parameter estimate value θ est Calculate the initial target value r0 and convert it into the conversion target value r m and convert it to the initial target value r0 or the converted target value r m is output to the lower control device 20 as the application target value r1 at the next time. In other words, the control device 10 according to the first embodiment outputs c For each, the model parameter estimates θ est and sequentially outputs the applied target value r1 to the lower-level control device 20. Thereafter, the lower-level control device 20 calculates and outputs the manipulated variable u for the controlled plant 30 so that the controlled variable y of the controlled plant 30 follows the applied target value r1. As a result, even if an unknown disturbance v exists, the influence of the disturbance v can be suppressed and a situation in which the controlled variable y deviates from the target value r can be prevented. Moreover, since there is no need to make any changes to the lower-level control device 20, which is an existing controller, it is possible to suppress the influence of the disturbance v safely and at low cost compared to, for example, replacing it with an advanced controller that uses model predictive control or the like.

[0029] <<Detailed Functional Configuration Example of Target Value Converter 111 According to First Embodiment>> A detailed functional configuration example of the target value conversion unit 111 according to the first embodiment will be described with reference to Fig. 3. Fig. 3 is a diagram illustrating a detailed functional configuration example of the target value conversion unit 111 according to the first embodiment.

[0030] As shown in FIG. 3, the target value conversion unit 111 according to the first embodiment includes a difference calculator 121, a control parameter calculation unit 122, a time difference calculator 123, a target deviation prediction unit 124, a target change amount calculation unit 125, an adder 126, and a conversion target value constraint unit 127.

[0031] The difference calculator 121 calculates the difference between the initial target value r0(t) and the controlled variable y(t) as the target deviation e0(t). That is, the difference calculator 121 calculates the target deviation e0(t) by e0(t)=r0(t)−y(t).

[0032] The control parameter calculation unit 122 calculates θ=θ est (t) is the closed-loop response function {S θ (t)}, the control gain k I and look-ahead length T p The control parameter calculation unit 122 calculates the control gain k I and look-ahead length T p can be calculated.

[0033] Specifically, the control parameter calculation unit 122 calculates the look-ahead length T p can be calculated.

[0034] Find T p ,where S θ (T p )=β×S θ (T max ) Here, β is a preset adjustment coefficient, and it is preferable that 0<β≦1. max is the final time that is preset as a sufficiently long value.

[0035] Furthermore, the control parameter calculation unit 122 calculates, for example, k I =α×1 / (g P +ε) to control gain k I Here, α is a preset adjustment coefficient, and it is preferable that 0<α≦1. ε is a small non-negative value. P is the look-ahead length T p The gain at time g p =S θ (T p )

[0036] The time difference calculator 123 calculates the time for one main control period T c That is, the time difference calculator 123 calculates the applied target value change amount dr1, which represents the time difference between the c The applied target value change amount dr1(t) is calculated by the following equation: The applied target value r1(t) is a target value set in the low-level control device 20 at the current time t.

[0037] The target deviation prediction unit 124 calculates the deviation θ=θ est (t) is the closed-loop response function {S θ (t)}, the target deviation e0(t), the time series {dr1(t)} of the past applied target value change amount dr1 (hereinafter referred to as the "applied target value change amount series {dr1(t)}"), and the look-ahead length T p Based on this, the correction target deviation e * The target deviation prediction unit 124 calculates the corrected target deviation e(t) by using the applied target value change amount series {dr1(t)} instead of the operation change amount time series {du(t)} described in Reference 1, for example. * (t) can be calculated.

[0038] Specifically, the target deviation prediction unit 124 calculates, for example, the control amount from the current time t to T p The value predicted to change after a certain time has elapsed is used as the pre-read response correction value y n (t) and then calculate the look-ahead response correction value y nThe corrected target deviation e0(t) is calculated by * (t) can be calculated as follows. Corrected target deviation e * (t) is, for example, e * (t)=e0(t)-y n (t) is calculated as follows. n (t) can be calculated, for example, by the methods described in References 2 and 3.

[0039] The target change amount calculation unit 125 calculates the corrected target deviation e * (t) and the control gain k I The target change amount calculation unit 125 calculates the target change amount dr(t) based on, for example, dr(t)=k I ×e * (t) to calculate the target change amount dr(t).

[0040] The adder 126 calculates a target value (hereinafter referred to as the "main control unit target value r") by adding the target change amount dr(t) to the application target value r1(t). a That is, the adder 126 calculates r a (t) = r1(t) + dr(t) is the target value of the main control unit r a Calculate (t).

[0041] The conversion target value constraint unit 127 determines the main control unit target value r a (t), the initial target value r0(t), and the target variable width w, the main control unit target value r a The upper and lower limits are imposed so that the absolute value of the difference between (t) and the initial target value r0(t) falls within the target variable width w, and the value after the constraint is used as the conversion target value r m Specifically, the conversion target value constraint unit 127 calculates the conversion target value r m Calculate (t).

[0042]

number

[0043] <<Closed-loop response function {S θ (t)} operation≫ The closed-loop response function {S θ The operation of the closed-loop response function {S θ FIG. 10 is a diagram illustrating an example of the operation of {(t)}.

[0044] As shown in Figure 4, the closed-loop response function {S θ (t)} is a unit step response S of the closed loop response model at time t after the elapse of time t from the initial time 0 when the model parameter setting value θ and time t are input. θ Output (t).

[0045] <Closed-loop response model> Time t is t=k×T where k is an integer greater than or equal to 0. c Therefore, hereinafter, time t and integer k will be regarded as the same. As a result, for example, notations such as y(k) and r1(k) can be regarded as the same as y(t) and r1(t). Note that such an integer k is also called an index representing sample time (which may also be called discrete time).

[0046] In this case, as a closed-loop response model that models the response of the closed-loop control configured by the low-level control device 20 and the controlled plant 30, for example, the ARMA model shown below can be used.

[0047]

number

[0048] Here, the state vector ξ(k) is as follows:

[0049]

number

[0050]

number

[0051] As a method for estimating the model parameter θ, for example, the method described in Reference 1 (recursive least squares method including a forgetting factor) can be used.

[0052] The initial value of the model parameter θ is θ0=θ est (0) can be a zero vector or a value representing the unit step response below.

[0053]

number

[0054] [Second embodiment] The second embodiment will be described below. In the second embodiment, the main control period T c A control period T shorter than f (Hereinafter referred to as “high-speed control period T f This section explains how to complement a target value using the

[0055] In the second embodiment, differences from the first embodiment will be mainly described, and a description of components that may be the same as those in the first embodiment will be omitted. That is, components that are not particularly described in the second embodiment may be the same as those in the first embodiment.

[0056] <Example of functional configuration of the control device 10 according to the second embodiment> An example of the functional configuration of the control device 10 according to the second embodiment will be described with reference to Fig. 5. Fig. 5 is a diagram showing an example of the functional configuration of the control device 10 according to the second embodiment.

[0057] As shown in Fig. 5, the control device 10 according to the second embodiment has a timer 116 in addition to the components described in the first embodiment. The timer 116 is realized, for example, by a process in which one or more programs installed in the control device 10 are executed by the processor 105 or the like, or by dedicated hardware or the like. Here, in the control device 10 according to the second embodiment, the high-speed control period T f A control amount y(t) is obtained for each time, and the control amount y(t) is input to a high-speed interpolation control unit 128, which will be described later.

[0058] The timer 116 is a high-speed control period T f For each time, the fast complement target value r b It functions as an operation trigger for calculating the high-speed control period T f is nT where n is a predetermined natural number. f =T c It is expressed as:

[0059] <<Detailed Functional Configuration Example of Target Value Converter 111 According to Second Embodiment>> A detailed example of the functional configuration of the target value conversion unit 111 according to the second embodiment will be described with reference to Fig. 6. Fig. 6 is a diagram showing an example of the detailed functional configuration of the target value conversion unit 111 according to the second embodiment.

[0060] As shown in FIG. 6, the target value converter 111 according to the second embodiment includes a high-speed complement controller 128 in addition to the components described in the first embodiment.

[0061] The high-speed complement control unit 128 calculates the main control unit target value r a (t) and the controlled variable y(t), the fast complementary target value r b The fast interpolation target value r is output. b The main control unit target value r a (t) and the main control unit target value r a (t+T c ) and the high-speed control period T f That is, the high-speed interpolation control unit 128 interpolates the target value every high-speed control period T f For each, the fast completion target value r b (t) where t=n1T for two integers n1 and n2. f and t=n2T c For time t, r a (t)=r b (t).

[0062] The conversion target value constraint unit 127 determines the fast interpolation target value r b (t), the initial target value r0(t), and the target variable width w, the fast complement target value r b The upper and lower limits are imposed so that the absolute value of the difference between (t) and the initial target value r0(t) falls within the target variable width w, and the value after the constraint is used as the conversion target value r m That is, the conversion target value constraint unit 127 calculates the high-speed control period T f For each, use the above number 1 to find r a (t) to r b The conversion target value r is calculated by replacing (t) m (t) is calculated. This allows for the fast interpolation target value r0 to be calculated, which can quickly respond to changes in the controlled variable y and the initial target value r0. b is the high-speed control period T f It is calculated every time.

[0063] <<Operation of the high-speed complement control unit 128>> The operation of the high-speed compensation control unit 128 according to the second embodiment will be described with reference to FIG. 7. FIG. 7 is a diagram for explaining an example of the operation of the high-speed compensation control unit 128.

[0064] As shown in FIG. 7, the main control unit target value r a (t) changes every main control period T c and the high-speed compensation target value r b (t) calculated by the high-speed compensation control unit 128 according to the second embodiment changes every high-speed control period T f . However, for two certain integers n1 and n2, when t = n1T f and t = n2T c , for the time t, r a (t) = r b (t). This is because the high-speed compensation target value r a is calculated at a timing when the target change amount calculation unit 125 is not operating within the main control period T c with the main control unit target value r b as a reference.

[0065] Note that the high-speed compensation control unit 128 may calculate the high-speed compensation target value r b by performing a process similar to the process of calculating the compensation operation amount u[[ID=3३]] b described in Reference 4, for example. Specifically, the high-speed compensation control unit 128 may calculate the high-speed compensation target value r b by, for example, the following steps 1 to 6. Hereinafter, for the sake of simplicity, for a certain integer n3, when t + (n3 - 1)T c ≤ t' < t + n3T c ، the case of calculating the high-speed compensation target value r b (t') at the time t' within the continuous time satisfying this will be described. Hereinafter, an index satisfying 0 ≤ j < n + 1 will be used. However, n is a natural number satisfying nT (t') at the time t' within the continuous time satisfying this will be described. Hereinafter, an index satisfying 0 ≤ j < n + 1 will be used. However, n is a natural number satisfying nT f = T c .

[0066] [[ID=५०]]Step 1: The high-speed compensation control unit 128 determines whether j = n.

[0067] Step 2: If it is determined in step 1 above that j=n, the high-speed complement control unit 128 sets y0=y(t), m dr Initialize (0)=0, j=0. Here, m dr (j) is the average target value change amount at index j, as will be described later. Note that, at this time, for two integers n1 and n2, t=n1T f and t=n2T c The time t'=t.

[0068] Step 3: If it is not determined in step 1 above that j=n, the high-speed complement control unit 128 updates the index so that j←j+1.

[0069] Step 4: The high-speed complementation control unit 128 calculates the predicted target deviation e f (j) Calculate the predicted target deviation e f (j) is the look-ahead length T predicted at the current time t'. p The high-speed complementation control unit 128 calculates the predicted target deviation e by, for example, the following calculation method 1 or 2. f Just calculate (j).

[0070] Predicted target deviation e f Calculation method 1 for (j) e f (j)=r0(t')-(y(t')+(r0(t')-y0)·(1-a(j))) a(j)=j T f / T p Note that r0(t') is the value of r0(t) at t=t'.

[0071] Predicted target deviation e f Calculation method 2 for (j) e f (j)=r0(t')-(y0+(y(t')-y0) / a(j)) a(j)=j T f / T p

[0072] Step 5: The high-speed complement control unit 128 calculates the average target value change amount mdr Calculate (j).

[0073] Dr. f (j)=k I ·e f (j) m dr (j)=(m dr (j-1)·j+dr f (j)) / (j+1)

[0074] Alternatively, to take a simple average, the average target value change m dr (j) may be calculated.

[0075] Dr. f (j)=k I ·e f (j) m dr (j)=m dr (j-1)+dr f (j)·T f / T p

[0076] Step 6: The high-speed complement control unit 128 b (t')=r a (t)+m dr (j) Fast complementary target value r b Calculate (t').

[0077] [Control system configuration example] An example of the configuration of a control system including the control device 10 according to the first and second embodiments will be described below.

[0078] <Example of conventional control system configuration> First, an example of the configuration of a conventional control system will be described with reference to Fig. 8. Fig. 8 is a diagram showing an example of the configuration of a conventional control system.

[0079] 8, in a conventional control system, a higher-level control device 40 (e.g., a process computer or an operator terminal) exists above a lower-level control device 20, and a target value r is given from the higher-level control device 40 to the lower-level control device 20. Thereafter, the lower-level control device 20 calculates and outputs an operation amount u for the controlled plant 30 so that the controlled amount y of the controlled plant 30 follows the given target value r.

[0080] <Configuration example of a control system including the control device 10> Next, a configuration example of a control system including the control device 10 according to the first or second embodiment will be described with reference to Fig. 9. Fig. 9 is a diagram showing an example of the configuration of a control system including the control device 10 according to one embodiment.

[0081] As shown in FIG. 9 , in a control system including the control device 10 according to the first or second embodiment, the control device 10 is included as an intermediate control device between a higher-level control device 40 and a lower-level control device 20. In other words, the control device 10 is disposed as an intermediate control device between the higher-level control device 40 and the lower-level control device 20. In this control system, an initial target value r0 is provided to the control device 10 from the higher-level control device 40. The control device 10 calculates an application target value r1 based on the provided initial target value r0 and a controlled variable y of the controlled plant 30, and outputs this applied target value r1 to the lower-level control device 20. Thereafter, the lower-level control device 20 calculates and outputs an operation variable u for the controlled plant 30 so that the controlled variable y of the controlled plant 30 follows the provided applied target value r1. Note that in the example shown in FIG. 9 , the control device 10 acquires the controlled variable y from the controlled plant 30; however, the control device 10 may acquire the controlled variable y from, for example, the lower-level control device 20.

[0082] When incorporating the control device 10 according to the first or second embodiment into a conventional control system, all that is required is the installation of the control device 10 and the associated wiring of the transmission equipment, and there is no need to modify the upper control device 40 or the lower control device 20. Therefore, the control device 10 according to the first or second embodiment can be incorporated into a conventional control system at low cost and safely.

[0083] Any controller that controls the controlled plant 30 using a predetermined control method can be used as the lower-level control device 20. For example, any controller that controls the controlled plant 30 using any existing control method such as PID control, model predictive control (MPC), sliding mode control, H2 control, etc. can be used as the lower-level control device 20.

[0084] In addition, as the control device 10 (intermediate control device), for example, a PC (personal computer), a distributed control system (DCS: Distributed Control System), a PLC (Programmable Logic Controller), a regulator, etc. can be used as the control device 10 (intermediate control device).

[0085] [Example] An example of a control system including the control device 10 according to the first and second embodiments will be described below.

[0086] <System configuration> The configuration of the control system according to this embodiment will be described with reference to Fig. 10. Fig. 10 is a diagram showing the configuration of the control system according to one embodiment.

[0087] 10 , in this embodiment, an initial target value r0 is provided from a higher-level control device 40 such as a process computer to a control device 10 according to the first or second embodiment. The control device 10 according to the first or second embodiment calculates an application target value r1 from the provided initial target value r0 and outputs it to a lower-level control device 20 which is a PID controller C. Then, the lower-level control device 20 calculates a manipulated variable u so that a controlled variable y of a controlled plant 30 which is a plant P follows the application target value r1, and outputs it to the controlled plant 30. In addition to the manipulated variable u, an unknown disturbance v is input to the controlled plant 30.

[0088] Transfer function of plant P The transfer function of the controlled plant 30 is assumed to be a second-order lag system expressed as follows:

[0089]

number

[0090] PID controller C The PID controller C is assumed to be a PI controller expressed as follows:

[0091]

number

[0092] In the following, the following two cases are assumed regarding the PID parameters.

[0093] Case 1: PID parameters are well tuned Case 2: PID parameters are not well adjusted Setting of the control device 10 As a setting of the control device 10 according to the first or second embodiment, the main control period T c is T c = 5 [sec], and the target variable width w was set to w = 0.5. f is T f =0.5 [sec].

[0094] Under the above conditions, the controlled plant 30 was controlled in each of Case 1 and Case 2 using only the PID controller C, the control device 10 according to the first embodiment, and the control device 10 according to the second embodiment. The results of these experiments will be described below.

[0095] <Results of Case 1> <When only PID controller C is used> In Case 1, the implementation results when only the PID controller C (lower control device 20) is used will be described with reference to Fig. 11. Fig. 11 is a diagram (part 1) showing the implementation results when only the PID controller C is used.

[0096] Figure 11(a) shows a time series graph of the initial target value r0(t), Figure 11(b) shows the initial target value r0(t) and the controlled variable y(t), Figure 11(c) shows the disturbance v(t), and Figure 11(d) shows the manipulated variable u(t).

[0097] As shown in Figures 11(a) to 11(d), the initial target value r0(t) is constant at 60, but the disturbance v(t) varies between -1 and 1. The disturbance v(t) causes the controlled variable y(t) to fluctuate, with large fluctuations occurring especially at the beginning of the change in the disturbance v(t). In the PID control by the lower-level control device 20, the controlled variable y(t) is made to follow the initial target value r0(t), so the manipulated variable u(t) varies in the opposite direction to the disturbance v(t) so as to cancel out the disturbance v(t).

[0098] <<When the control device 10 according to the first embodiment is used>> In Case 1, the implementation results when the control device 10 according to the first embodiment is used will be described with reference to Fig. 12. Fig. 12 is a diagram (part 1) showing the implementation results when the control device 10 according to the first embodiment is used.

[0099] Fig. 12(a) shows the initial target value r0(t) and the conversion target value r m 12(b) shows the time series graph of the initial target value r0(t) and the controlled variable y(t), FIG. 12(c) shows the disturbance v(t), and FIG. 12(d) shows the time series graph of the manipulated variable u(t). m (t) at the next time t+T c The target value r1(t+T c ) is set to output.

[0100] As shown in Fig. 12(a) to Fig. 12(d), the conversion target value r m (t) changes according to the change in the disturbance v(t) and is a value different from the initial target value r0(t), but the converted target value r m The absolute value of the difference between (t) and the initial target value r0(t) is restricted to within the target variable width w=0.5. Therefore, the conversion target value r m (t) is a value between 59.5 and 60.5.

[0101] The target conversion value r m By setting (t), the manipulated variable u(t) changes more sharply when the disturbance v(t) changes, compared to when only the PID controller C is used. As a result, the difference between the controlled variable y(t) and the initial target value r0(t) is kept smaller than when only the PID controller C is used.

[0102] <<When the control device 10 according to the second embodiment is used>> In Case 1, the implementation results when the control device 10 according to the second embodiment is used will be described with reference to Fig. 13. Fig. 13 is a diagram (part 1) showing the implementation results when the control device 10 according to the second embodiment is used.

[0103] Fig. 13(a) shows the initial target value r0(t) and the conversion target value r m 13(b) shows the time series graph of the initial target value r0(t) and the controlled variable y(t), FIG. 13(c) shows the disturbance v(t), and FIG. 13(d) shows the time series graph of the manipulated variable u(t). m (t) at the next time t+T c The target value r1(t+T c ) is set to output.

[0104] As shown in Fig. 13(a) to Fig. 13(d), the conversion target value r m (t) changes according to the change in the disturbance v(t) and is a value different from the initial target value r0(t), but the converted target value r m The absolute value of the difference between (t) and the initial target value r0(t) is restricted to within the target variable width w=0.5. Therefore, the conversion target value r m (t) is a value between 59.5 and 60.5.

[0105] The target conversion value r m By setting (t), the manipulated variable u(t) changes more sharply when the disturbance v(t) changes, compared to when only the PID controller C is used. As a result, the difference between the controlled variable y(t) and the initial target value r0(t) is kept smaller than when only the PID controller C is used. Furthermore, the fluctuation of the controlled variable y(t) is further suppressed compared to when the control device 10 according to the first embodiment is used.

[0106] <Comparison of control response> In Case 1, the maximum and minimum values ​​of the control response and the amount of overshoot are shown in Table 1 below when only the PID controller C is used, when the control device 10 according to the first embodiment is used, and when the control device 10 according to the second embodiment is used.

[0107] [Table 1] As shown in Table 1 above, the amount of upper overshoot is 0.423 when only PID control is used, 0.352 when the control device 10 according to the first embodiment is used, and 0.283 when the control device 10 according to the second embodiment is used. The amount of lower overshoot is 0.846 when only PID control is used, 0.677 when the control device 10 according to the first embodiment is used, and 0.590 when the control device 10 according to the second embodiment is used. This shows that the influence of the unknown disturbance v can be suppressed by using the control device 10 according to the first or second embodiment.

[0108] <<Estimation results of model parameter θ>> In Case 1, the estimation results of the model parameter θ when the control device 10 according to the first embodiment is used and when the control device 10 according to the second embodiment is used will be described with reference to Fig. 14. Fig. 14 is a diagram (part 1) showing the estimation results of the model parameter θ. Note that the ARMA model shown in the above equation 2 was used as the closed-loop response model.

[0109] 14(a) shows a time series graph of the estimation result of the model parameter θ when the control device 10 according to the first embodiment is used, and FIG. 14(b) shows a time series graph of the estimation result of the model parameter θ when the control device 10 according to the second embodiment is used. It can be seen that the model parameter θ is sequentially estimated online in both the case where the control device 10 according to the first embodiment is used and the case where the control device 10 according to the second embodiment is used.

[0110] <Results of Case 2> <When only PID controller C is used> In Case 2, the implementation result when only the PID controller C (lower control device 20) is used will be described with reference to Fig. 15. Fig. 15 is a diagram (part 2) showing the implementation result when only the PID controller C is used.

[0111] Figure 15(a) shows a time series graph of the initial target value r0(t), Figure 15(b) shows the initial target value r0(t) and the controlled variable y(t), Figure 15(c) shows the disturbance v(t), and Figure 15(d) shows the manipulated variable u(t).

[0112] As shown in Figures 15(a) to 15(d), the initial target value r0(t) is constant at 60, but the disturbance v(t) varies between -1 and 1. The disturbance v(t) causes the controlled variable y(t) to fluctuate, with large fluctuations occurring especially at the beginning of the change in the disturbance v(t). In the PID control by the lower-level control device 20, the controlled variable y(t) is made to follow the initial target value r0(t), so the manipulated variable u(t) varies in the opposite direction to the disturbance v(t) so as to cancel out the disturbance v(t).

[0113] <<When the control device 10 according to the first embodiment is used>> In Case 2, the implementation results when the control device 10 according to the first embodiment is used will be described with reference to Fig. 16. Fig. 16 is a diagram (part 2) showing the implementation results when the control device 10 according to the first embodiment is used.

[0114] Fig. 16(a) shows the initial target value r0(t) and the conversion target value r m 16(b) shows the time series graph of the initial target value r0(t) and the controlled variable y(t), FIG. 16(c) shows the disturbance v(t), and FIG. 16(d) shows the time series graph of the manipulated variable u(t). m (t) at the next time t+T c The target value r1(t+T c ) is set to output.

[0115] As shown in Fig. 16(a) to Fig. 16(d), the conversion target value r m (t) changes according to the change in the disturbance v(t) and is a value different from the initial target value r0(t), but the converted target value r m The absolute value of the difference between (t) and the initial target value r0(t) is restricted to within the target variable width w=0.5. Therefore, the conversion target value r m (t) is a value between 59.5 and 60.5.

[0116] The target conversion value r m By setting (t), the manipulated variable u(t) changes more sharply when the disturbance v(t) changes, compared to when only the PID controller C is used. As a result, the difference between the controlled variable y(t) and the initial target value r0(t) is kept smaller than when only the PID controller C is used.

[0117] <<When the control device 10 according to the second embodiment is used>> In Case 2, the implementation result when the control device 10 according to the second embodiment is used will be described with reference to Fig. 17. Fig. 17 is a diagram (part 2) showing the implementation result when the control device 10 according to the second embodiment is used.

[0118] Fig. 17(a) shows the initial target value r0(t) and the conversion target value r m 17(b) shows the time series graph of the initial target value r0(t) and the controlled variable y(t), FIG. 17(c) shows the disturbance v(t), and FIG. 17(d) shows the time series graph of the manipulated variable u(t). m (t) at the next time t+T c The target value r1(t+T c ) is set to output.

[0119] As shown in Fig. 17(a) to Fig. 17(d), the conversion target value r m (t) changes according to the change in the disturbance v(t) and is a value different from the initial target value r0(t), but the converted target value r m The absolute value of the difference between (t) and the initial target value r0(t) is restricted to within the target variable width w=0.5. Therefore, the conversion target value r m (t) is a value between 59.5 and 60.5.

[0120] The target conversion value r mBy setting (t), the manipulated variable u(t) changes more sharply when the disturbance v(t) changes, compared to when only the PID controller C is used. As a result, the difference between the controlled variable y(t) and the initial target value r0(t) is kept smaller than when only the PID controller C is used. Furthermore, the fluctuation of the controlled variable y(t) is further suppressed compared to when the control device 10 according to the first embodiment is used.

[0121] <Comparison of control response> In Case 2, the maximum and minimum values ​​of the control response and the amount of overshoot in each of the cases where only the PID controller C is used, where the control device 10 according to the first embodiment is used, and where the control device 10 according to the second embodiment is used are shown in Table 2 below.

[0122] [Table 2] As shown in Table 2 above, the amount of upper overshoot is 0.395 when only PID control is used, 0.379 when the control device 10 according to the first embodiment is used, and 0.259 when the control device 10 according to the second embodiment is used. The amount of lower overshoot is 0.789 when only PID control is used, 0.633 when the control device 10 according to the first embodiment is used, and 0.547 when the control device 10 according to the second embodiment is used. This shows that the influence of the unknown disturbance v can be suppressed by using the control device 10 according to the first or second embodiment.

[0123] <<Estimation results of model parameter θ>> In Case 2, the estimation results of the model parameter θ when the control device 10 according to the first embodiment is used and when the control device 10 according to the second embodiment is used will be described with reference to Fig. 18. Fig. 18 is a diagram (part 2) showing the estimation results of the model parameter θ. Note that the ARMA model shown in the above equation 2 was used as the closed-loop response model.

[0124] 18(a) shows a time series graph of the estimation result of the model parameter θ when the control device 10 according to the first embodiment is used, and FIG. 18(b) shows a time series graph of the estimation result of the model parameter θ when the control device 10 according to the second embodiment is used. It can be seen that the model parameter θ is sequentially estimated online in both the case where the control device 10 according to the first embodiment is used and the case where the control device 10 according to the second embodiment is used.

[0125] [summary] As described above, the control device 10 according to the first and second embodiments makes it possible to make the controlled variable of the controlled object follow the target value even when an unknown disturbance is present, while effectively utilizing an existing controller. In this case, the control device 10 according to the first and second embodiments does not require any modifications to the existing controller, and therefore can improve the target deviation with respect to the unknown disturbance safely and at low cost. This is one of the notable features not found in conventionally known methods for improving the target deviation (e.g., a method for readjusting PID parameters, a method for replacing with advanced control such as model predictive control, or a method for modifying a closed loop such as a disturbance observer or Smith compensator).

[0126] Furthermore, after the control device 10 according to the first and second embodiments is introduced into the control system, even if, for example, the lower-level control device 20 is readjusted or a change is made to the controlled plant 30 itself, the model parameter θ is adjusted autonomously by the model parameter estimation unit 112, so that there is no need for maintenance of the control device 10 (intermediate control device) itself.

[0127] Furthermore, the control device 10 according to the first and second embodiments maintains the original control loop and adjusts the conversion target value r so as not to deviate from the initial target value r0 by the target variable width w. m Therefore, if the original control loop is stable, the stability of the control system incorporating the control device 10 is also guaranteed.

[0128] In addition, by using the control device 10 according to the first and second embodiments, the influence of the unknown disturbance v can be suppressed without installing a new sensor or the like for measuring the unknown disturbance v or increasing the measurement frequency.

[0129] The present invention is not limited to the above-described embodiments specifically disclosed, and various modifications, changes, and combinations with known technologies are possible without departing from the scope of the claims.

[0130] [References] Reference 1: Patent No. 7014330 Reference 2: International Publication No. 2016 / 092872 Reference 3: JP 2020-21411 A Reference document 4: Patent No. 7283646 [Explanation of symbols]

[0131] 10 Control device 20 Lower level control device 30 Controlled plants 101 Input Device 102 Display device 103 External I / F 103a Recording media 104 Communication I / F 105 processors 106 Memory Device 107 Bus 111 Target value conversion unit 112 Model parameter estimation section 113 Switch 114 Timer 115 Timer 121 Differentiator 122 Control parameter calculation unit 123 Time Differentiator 124 Target deviation prediction unit 125 Target change amount calculation unit 126 Adder 127 Conversion target value constraint part 128 High-speed Complementary Control Unit

Claims

1. A control device disposed between a higher-level control device that outputs a first target value for a control amount of a controlled object and a lower-level control device that controls the controlled object in accordance with a given second target value, a model parameter estimation unit that estimates parameters of a closed-loop response model that models a response of a closed-loop control configured by the lower-level control device and the controlled object, based on the controlled variable and the second target value; a target value conversion unit that calculates a third target value by converting the first target value based on the first target value, the second target value, and the parameter so that the controlled variable asymptotically approaches the first target value; a switching unit that outputs either the first target value or the third target value to the lower-level control device as the next second target value; A control device having:

2. 2. The control device according to claim 1, wherein the third target value is a value that is constrained so that an absolute value of a difference between the third target value and the first target value is equal to or less than a predetermined target variable width.

3. The target value conversion unit includes: a target deviation prediction unit that predicts a corrected target deviation obtained by correcting a target deviation representing a difference between the first target value and the controlled variable based on the parameter, the first target value, the second target value, and the controlled variable using the controlled variable after a predetermined look-ahead length; a target change amount calculation unit that calculates a target change amount that represents a change amount of the second target value based on the corrected target deviation; an adder that calculates a fourth target value by adding the target change amount to the second target value; a conversion target value constraint unit that calculates, as the third target value, the fourth target value constrained so that an absolute value of a difference between the fourth target value and the first target value is equal to or less than the target variable width.

4. The target value conversion unit The control device according to claim 3 , wherein the third target value is calculated by converting the first target value in a predetermined first control cycle so that the controlled variable gradually approaches the first target value.

5. The target value conversion unit includes:

5. The control device according to claim 4, further comprising a high-speed complementation control unit that calculates, in a predetermined second control period shorter than the first control period, a fifth target value that complements between the fourth target value and the fourth target value after the first control period, so that the controlled variable asymptotically approaches the first target value.

6. the closed-loop response model is an ARMA model; The model parameter estimation unit A control device according to any one of claims 1 to 5, wherein the parameters of the ARMA model are estimated recursively.

7. the host control device is a process computer or an operator terminal, The control device according to claim 1 , wherein the lower-level control device is a DCS, a PLC, or a controller.

8. a control device disposed between a higher-level control device that outputs a first target value for a controlled variable of a controlled object and a lower-level control device that controls the controlled object in accordance with a given second target value, a model parameter estimation step of estimating parameters of a closed-loop response model that models a response of a closed-loop control configured by the lower-level control device and the controlled object, based on the controlled variable and the second target value; a target value conversion step of calculating a third target value by converting the first target value based on the first target value, the second target value, and the parameter so that the controlled variable asymptotically approaches the first target value; a switching procedure of outputting either the first target value or the third target value to the lower-level control device as the next second target value; A control method for performing

9. a control device disposed between a higher-level control device that outputs a first target value for a controlled variable of a controlled object and a lower-level control device that controls the controlled object in accordance with a given second target value; a model parameter estimation step of estimating parameters of a closed-loop response model that models a response of a closed-loop control configured by the lower-level control device and the controlled object, based on the controlled variable and the second target value; a target value conversion step of calculating a third target value by converting the first target value based on the first target value, the second target value, and the parameter so that the controlled variable asymptotically approaches the first target value; a switching procedure of outputting either the first target value or the third target value to the lower-level control device as the next second target value; A program that executes the following.

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