JPS5922102A - Pi controller - Google Patents

Abstract

PURPOSE:To improve the precision of a PI controller which varies a proportional gain and an integral time automatically and to facilitate its handling by converting parameters of adaptability into parameters relating to values on a time axis. CONSTITUTION:A PI control constant adjusting part 11 inputs the proportional gain K of a controlled system and calculates the proprotional gain KP and integral time T1 of PI control. Quickness parameters alpha and T are so set that the time when control response reaches 100.alpha(%) as a final value in response to stepwise variation in the command of the controlled system is T. Further, a stability parameter beta is so set that while beta>1.0, beta=1/omegaCTI. Therefore, the parameter beta as an index of stability is settable in addition to the parameters alpha and T as indexes of quickness, so the arithmetic expression of the proportional gain KP and integral time TI is derived from the results of the simulation of many controlled systems.

Description

[Detailed Description of the Invention] [A branch of the invention] This invention is a so-called proportional method in which the deviation between a target value and a measured value and its integral are multiplied by a constant, and the sum is the output of the operating air. Integral (Relates to a pH control device, and particularly relates to a PII control device that has a function of automatically adjusting the P■ control constant in accordance with changes in the characteristics of the steel control 1 object.

[Prior art]

When controlling a nonlinear controlled object using a PI quantity control device, if control is performed with the PI quantity control constant completely fixed, it is impossible to always obtain a desired control response.

As an improved control device, we linearize the non-linear controlled object within all minute changes, formulate it as a proportional system, find the gain of this proportional system from other processes, and keep the control response constant against fluctuations in the value. There is a control device that automatically adjusts the PI quantity control constant so as to maintain the PI amount. FIG. 1 is a diagram showing the configuration of such a control device. FIG. 1 shows a pump discharge flow rate control system based on valve opening control as a control system. In FIG. 1, water is pumped from a water storage tank 1 to a water receiving tank 4 through a pipe 2, a bomb 3, and an f& control valve 5. A flow rate detector 6 and an opening degree detector 7 for detecting the entire opening degree of the flow rate control valve 5 are installed on the discharge side of the pump 3.

The process variables detected by these detectors 6 , 7 are input to the control device 8 . Then, calculation is performed using a function built in the control device 6 in advance, and as a result, an opening control command is outputted from the control device 8 to the flow rate control valve 5.

The control device 8 includes an input/output interface section 9, a proportional system gain calculation section 10. P amount control constant adjustment section 11. Consists of a PI control section 12 and an input/output interface section 9
inputs the signals from the flow rate detector 6 and (411 degree detector 7) and calculates the proportional system gain calculation unit 10 and P
It has the function of transmitting all the information to the PI control section 12 and outputting the opening control command from the PI control section 12 to the flow rate control valve 5. The PI control unit 12 has a function of calculating the current output MVn from the target flow Iqs, the measured flow rate detected by the flow rate detector 6, and q using the calculation formula shown below.

MVn=△MV −←MV n −1−(])△MV=
Kp((On-"-') 4-'j'!n l
-(2) J en-qs-q ...to (3) 1Vn -1: Previous opening output ΔM■: Opening output variation KP: Proportional gain T: Integral time en: This time deviation en-+: Previous deviation τ: The control period proportional system gain calculation unit 10 has a function to linearize the nonlinear controlled object within a minute change and calculate the proportional system gain Ki of the field formulated as a proportional system from other process variables. ),
-1 In the example shown in Figure 1, the controlled object is assumed to be in pressure equilibrium, and is expressed by the fth equation (4) shown below. Equation 4 is linearized near a certain equilibrium point, and the proportional system gain Find it using the formula.

hl −ht = fv(u)Q”−fp(q)
- (hI: Water level in the water tank: Water level in the water tank U: Flow rate control valve opening q: Flow rate flowing through the pipe fq11): Loss coefficient fp(q) of the flow rate control valve: Pump discharge pressure f 'v(ul S f U)'s micromolecule 'p(q): Differential of fp(q) n Nibrant-specific constant small PI control constant 1 Decrease part 1] is the process quantity equation In this example, FlowtWq and 18F1rkl
The ratio fv11 gain Kp formula, which is a KPI control constant, and the integral time Ti
″f, which has the function of calculating − such an IM
Conventionally, in the control device of the configuration, the calculation algorithm procedure used in the control constant adjustment section 11 is as shown in Fig. The IC is determined so that Kp = − 3 and T) = − ωC by setting it to a constant value and inputting it from the proportional system gain calculation unit 10 of the controlled object to obtain the PI quantity control proportional gain, and the integration time of 1°. do. Therefore, in the conventional method, the only parameter for adjusting the control response characteristic is the intersection angular frequency ωC, and if ωC is set, the proportional gain ra
p and the integration time TI are uniquely determined.

[Problems with conventional technology]

However, in general, specifying control response characteristics often concerns the response on the time axis to step changes in the target value, so it is necessary to determine what value ωC should be specified to obtain a desirable control response. It's not easy to do.

In addition, the intersection angular frequency ωC is an index for the coordination of the control system, and is not an index for the stability of the control system. One drawback of conventional control devices is that it is difficult to create a desired control response that does not exist in the algorithm.

[Purpose of the invention]

The purpose of this invention is to be able to set parameters specifying control response characteristics for both coordination and stability.
Moreover, by subtracting the linked parameter from the parameter related on the time axis, a highly accurate and easy-to-handle control device # is provided.

[Summary of the invention]

In the invention, in a PI control device that automatically changes a proportional gain Kp and an integral time TI that are preset in the control device according to a process value to be side-turned, the process value is linearized within minute changes and proportional A proportional system gain calculation unit that outputs j system gains K and a predetermined round transfer function intersect with the angular frequency ωC1 speed 1F, and the gender parameter α
(α(1,0) and T, stability parameter β (β
)1.0) and the proportional system gain, and a PI quantity establishment a height 1 adjustment part that calculates the gain Kp and the integration time TI from the proportional system gain, and the coupling parameter α4? and T is the time required for the control response to a step change in the control target value of the process f to reach 10(l・α(%)).
The above objective was achieved by configuring the stability parameter β to be set as follows, the proportional gain Kp and the integration time Tl to be set so as to satisfy the respective relational expressions.

The present invention will be explained in detail with reference to Examples below.

[Embodiments of the invention]

FIG. 3 shows the calculation algorithm of the PI control constant adjustment section 11 used in one embodiment of the present invention. According to this invention, the connectivity parameters α and T and the stability parameter β are set.

After the coupling parameters α, T and stability parameter β are explained in detail, the proportional system gain K of the controlled object is input to the proportional system gain calculation unit 10 or C) as in the past, and the PI quantity control river is The proportional gain Kp and the integral time Ti are respectively 6)
Calculation 1-ru (7) Using equation (7), the connectivity parameters α and Ti are determined as follows.

The time taken for the control response to reach the final value of 1()0α(%) for a step change of the target (1α) of the controlled object is defined as T. However, α is α<: 1.0. For example, if you want to design a total time of 45 seconds until the control response to a step change in the target value reaches 95% of the final value, α = 0.95, T = 45 (F14))
You can set it as . When α is fixed, the smaller T is, the faster the control response follows the target 1ji'j.

The stability parameter β is selected in the range β>1.0 so as to satisfy the following equation (8). Therefore,
It means that the larger β is, the more stable it is. That is, when β is large, the rise of the control response is gradual, and when β is small, the rise is rapid.

Note that the ratios shown in equations (6) and (7),
The calculation formulas for the gain Kp and the integral time TI were derived as a result of simulations for many controlled objects. In addition, in the above-mentioned embodiment, the pump discharge flow control/
l! Although V) Defense has been explained with reference to V), it goes without saying that the present invention can be similarly applied to other control systems.

〔Effect of the invention〕

In the conventional control device 4, the only parameter for specifying control response characteristics is the intersection angular frequency (·)C, which is an index of coordination, and since ωC is a parameter on the frequency axis, its setting is extremely difficult. It was feminine.

In contrast, in this invention, four of the parameters to be set are
Responsiveness parameters The parameters are related to the control response on the time axis, so they can be easily set.In addition to the parameters that are indicators of responsiveness, parameters that are indicators of stability are also set, allowing for high accuracy and ease of use. It has the advantage of being able to provide a complete control system that is easy to handle.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a control device to which the present invention is applied;
FIG. 2 shows the calculation algorithm of the PIII leg constant adjustment section in the conventional control device, and FIG. 3 shows the calculation algorithm according to this fifth embodiment. 8...Control device, 1o...Proportional system gain calculation unit, 1
1... PI control constant adjustment section, 12... PIil+1
1 (Foundation) Department. Applicant's agent Kiyomata Inomata Figure 1 Figure 2

Claims (1)

[Scope of Claims] A PII control device that automatically changes a proportional gain Kp and an integration time TI preset in a control device according to a process value of a controlled object, linearizing the process value within minute changes, The proportional system gain calculation unit that calculates the proportional system gain Ki and the intersection angular frequency of the predetermined open-loop transfer function C1 quick response parameter (X' (α <: 1
．． 0 > and T, stability] parameter β-(β-n 1.
0) and the proportional gain Kp
and a PII control constant adjustment unit that calculates the control target value of the process value (J11 response is 100%).・The time to reach α(@ is set to T, and the AC stability parameter β
The PII control is characterized in that ωCψ TI is set so as to satisfy the I relationship of β = □, and the proportional gain Kp and the integral time T7 are each set so as to satisfy the relational expression 1'F. Device.