JP6111913B2 - Control parameter adjustment system - Google Patents

Description

  The present invention relates to a system for adjusting a control parameter to an optimum value.

  Generally, in an industrial plant such as a power plant and a petrochemical plant, a monitoring control device that monitors and controls equipment is used. The supervisory control device measures various process values such as temperature, pressure, and flow rate in order to operate the plant safely. Further, the monitoring control device displays the measured process value and notifies the plant operator of the operation state of the plant.

  The supervisory control device is provided with a number of control elements. For example, there are a PID controller, a PI-D controller, an I-PD controller, a 2-degree-of-freedom PID controller, and a model-driven PID controller as examples of control elements using PID (proportional integral derivative) operations. In order to design the control parameters of the control elements, conventionally, some modeling has been performed to obtain a transfer function representing the dynamic characteristics of the controlled object. For example, in the design and adjustment of a process control system, a two-stage method is adopted in which a dynamic characteristic model (or feature amount) to be controlled is first obtained and then control parameters are determined from the dynamic characteristic model based on a design rule. It was.

  A lot of data is necessary to extract the dynamic characteristic model necessary for control design. In addition, an error occurs in the dynamic characteristic model due to noise and non-linearity of the control target. For this reason, much labor is required only to obtain the dynamic characteristic model, and there are cases where a correct control parameter cannot be obtained from the identified dynamic characteristic model.

On the other hand, the following three methods are well known as methods for adjusting control parameters without obtaining a dynamic characteristic model of a controlled object.
・ IFT (Iterative Feedback Backing)
・ VRFT (Virtual Reference Feedback Tuning)
-FRIT (Fitious Reference Iterative Tunig)

  In a method called IFT, the control parameters are updated by repeating the test. In a method called VRFT and FRIT, control parameters are determined from a set of test data. Patent Document 1 discloses an example of VRFT.

JP 2009-175717 A

  In IFT, tests must be performed repeatedly to determine control parameters. There is a problem that a lot of data is required to determine the control parameter, and it takes a lot of time. In VRFT and FRIT, it is necessary to set a model indicating the response characteristic of the control system, but it is not easy to set an optimal model.

  The present invention has been made to solve the above-described problems. An object of the present invention is to provide a control parameter adjustment system that can easily adjust the value of a control parameter without the need to repeatedly perform a test or set a model indicating the response characteristic of the control system. is there.

  With the control parameter adjustment system according to the present invention, it is not necessary to repeatedly perform a test or set a model indicating the response characteristic of the control system, and the control parameter value can be easily adjusted.

It is a block diagram which shows the outline of the plant provided with the control parameter adjustment system in Embodiment 1 of this invention. It is a figure which shows the structure of a control parameter adjustment system. It is a figure which shows the structural example of the controller provided with the IMC control part and PD compensator.

  The present invention will be described in detail with reference to the accompanying drawings. The overlapping description will be simplified or omitted as appropriate. In each figure, the same or corresponding parts are denoted by the same reference numerals.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram showing an outline of a plant provided with a control parameter adjustment system according to Embodiment 1 of the present invention. In FIG. 1, reference numeral 1 denotes a control object whose transfer function is P (s). 2 is a controller whose transfer function is C (s, θ). θ is a control parameter (control constant) of the controller 2. The controller 2 controls the control object 1. The controller 2 includes an IMC control unit 3 and a PD compensator 4 (not shown in FIG. 1).

  A target value r (t) is input to the controller 2. Further, the control amount y (t) of the control object 1 is input to the controller 2. Based on the input target value r (t) and control amount y (t), the controller 2 outputs an operation amount u (t) so that the operation of the controlled object 1 follows the target value r (t). To do. The controlled object 1 operates according to the input operation amount u (t). The control amount y (t) of the control object 1 when the operation is performed according to the operation amount u (t) is input to the controller 2. That is, the plant shown in FIG. 1 forms a control loop in which the controller 2 takes in the target value r (t) and the controlled variable y (t) and generates the manipulated variable u (t).

Reference numeral 5 denotes a control parameter adjustment system for adjusting the value of the control parameter θ of the controller 2. The control parameter adjustment system 5 determines the control parameter θ based on a set of operation amount u ₀ (t) and control amount y ₀ (t) obtained during the test. r ₀ (t) represents a target value input to the controller 2 during the test. The test is performed by changing the target value r ₀ (t), for example. The target value r ₀ (t), the manipulated variable u ₀ (t), and the controlled variable y ₀ (t) at the time of the test are input to the control parameter adjusting system 5.

  Furthermore, the control parameter adjustment system 5 has an adjustment function for adjusting the control parameter θ of the controller 2. The adjustment function is realized by, for example, the subtracter 9 and the arithmetic setting unit 10. The configuration for realizing the adjustment function is not limited to this.

FIG. 3 is a diagram illustrating a configuration example of the controller 2 including the IMC control unit 3 and the PD compensator 4.
FIG. 3 shows a block diagram of model drive PID control. In FIG. 3, d indicates a disturbance element.

  The Q filter Q (s) and SV filter SV (s) of the IMC control unit 3 are expressed by the following equations.

  λ and α are fine tuning parameters of the MD-PID controller. λ is a parameter related to the tracking speed of the target value of the control system. α is a parameter related to disturbance suppression of the control system. The default value of λ and the default value of α are each 1. λ and α are set to default values, respectively.

  Further, the control parameter adjustment system 5 has a third calculation function for calculating the transfer function P (s) of the controlled object 1. The control parameter adjustment system 5 calculates P (s) based on the control parameter θ that minimizes the value of the evaluation function J.

Therefore, the control object P (s) can be calculated by P (s) ⁻¹ = G (s) ⁻¹ −F (s). In particular, the denominator series coefficient of the control object P (s) is P (s) ⁻¹ = p ₀ + p ₁ s + p ₂ s ² + p ₃ s ³ +.
Then, P _i (i = 0, 1, 2, 3,...) Can be obtained by Taylor expansion of G (s) ⁻¹ -F (s).

  If the dynamic characteristic shape of the control target P (s) is a first-order lag system having a dead time, the control target P (s) is expressed by the following equation.

K _p , T _p , and L _p can be obtained by solving this nonlinear equation.

  Further, if the dynamic characteristic shape of the control object P (s) is an integral system having a dead time, the control object P (s) is expressed by the following equation.

T _p and L _p can be obtained by solving this nonlinear equation. Note that the subscript p means a plant.

  When the controller 2 has the configuration shown in FIG. 3, the control amount y is expressed by the following equation.

  If the disturbance d = 0, the control amount y is a function of the target value r as shown in the following equation. The subscript c means a controller.

The target value r is changed in the actual process to obtain y. At this time, the target value is r ₀ and the control amount is y ₀ . The r ₀ to calculate the control variable y by substituting the above equation. If it can be confirmed that the calculated control amount y substantially matches the control amount y ₀ , it can be evaluated that the control parameter θ specified by the arithmetic setting unit 10 is effective. As a comparison method, for example, there is a method in which a graph of calculated values and a graph of response results of an actual process are displayed side by side and visually confirmed. As another comparison method, there is a method of confirming by a numerical value such as IAE.

Such an evaluation may be performed in the control parameter adjustment system 5. In this case, the control parameter adjustment system 5 has a fourth calculation function for calculating the control amount y by calculation. That is, the control parameter adjustment system 5 calculates the control amount y using the target value r ₀ input to the IMC control unit 3 and the control parameter θ specified by the arithmetic setting unit 10. Further, the control parameter adjustment system 5 has a determination function for determining whether or not the control parameter θ specified by the calculation setting unit 10 is valid. Control parameter adjusting system 5, performs the determination based on the control amount y ₀ of the actual process when the controlled variable y and the target value r ₀ obtained by calculation is input to the actual process. For example, it is determined that the control parameter adjusting system 5 determines the value of such IAE from the control variable y and the control amount y ₀ Prefecture, if its value is within the allowable range, it is effective control parameter θ identified.

  With the control parameter adjustment system 5 having the above-described configuration, it is not necessary to repeatedly perform a test or set a model indicating the response characteristics of the control system when adjusting the control parameters. In addition, the control parameters can be easily adjusted.

  Since the transfer function P (s) of the control target 1 can be obtained, various controllers such as a PID controller, a PI-D controller, an I-PD controller, a two-degree-of-freedom PID controller, and a model-driven PID controller. Can be applied. Furthermore, control parameters can be grasped through the display of the Nyquist diagram, each sensitivity function, and time response simulation analysis results. Therefore, when applying to actual processes, reliable control parameters can be used without relying on experience or intuition as in the past. Can be set.

DESCRIPTION OF SYMBOLS 1 Control object 2 Controller 3 IMC control part 4 PD compensator 5 Control parameter adjustment system 6 Virtual PD compensator 7 Adder 8 First order lag model 9 Subtractor 10 Operation setting device

Claims (5)

The adjusting means uses the virtual second gain, the virtual differential time, and the virtual differential gain of the virtual PD compensator when the evaluation function is minimized under a certain condition, as the second gain and differential of the PD compensator. The control parameter adjustment system according to claim 1 , wherein the control parameter adjustment system is set for each of time and differential gain. The adjusting means calculates values of the reciprocal of the virtual first gain, the virtual dead time, and the virtual time constant of the first-order lag model when the evaluation function is minimized under a certain condition, as the first gain of the IMC control unit. the control parameter adjustment system according to claim 1 or claim 2 respectively set to the dead time and time constant. The control according to any one of claims 1 to 3 , further comprising third calculation means for calculating a transfer function of the control object based on a control parameter of the controller adjusted by the adjustment means. Parameter adjustment system. Fourth calculation means for calculating by calculation a first control amount output from the control object using a target value input to the controller and a control parameter of the controller adjusted by the adjustment means;
The controller adjusted by the adjusting unit based on the first control amount calculated by the fourth calculating unit and the second control amount output by the control object when the target value is input to the controller Determining means for determining whether or not the control parameter is valid;
The control parameter adjustment system according to any one of claims 1 to 4 , further comprising:

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