Performance evaluation method for industrial process control system

Abstract

The invention discloses an industrial process control system performance evaluation method, which is based on a system model, combines an internal model principle to design an equivalent PID (Proportion Integration Differentiation) controller, then calculates a control performance index of a closed-loop system, carries out contrastive analysis by combining a performance index of a current actual system, quantifies the deviation between ideal performance and actual performance, and finally evaluates the performance of an industrial process control system. And finally, giving out an evaluation result of the system performance. According to the method, the performance of the control system can be accurately evaluated, a quantitative basis is provided for controller optimization design and system performance improvement, and the evaluation accuracy is improved.

Description

Technical Field

[0001] This method belongs to the field of performance evaluation of automatic control systems, specifically a technical method for quantitatively evaluating the performance of a control system by combining the internal model principle. Background Art

[0002] In industrial control systems, as the actual operating control system ages over time, due to factors such as equipment aging and process condition changes, the control performance of the system often deteriorates. This performance degradation may manifest as a slower response speed, an increase in steady-state error, or a decrease in system stability, ultimately affecting production efficiency and product quality. Therefore, scientific evaluation of the control system performance is the key to determining the need for controller optimization to ensure that the system can adapt to complex working conditions and maintain efficient operation.

[0003] Currently, the methods for evaluating the performance of control systems mainly include those based on empirical formulas, frequency-domain analysis, and simple simulation comparisons. These methods have certain guiding significance in engineering practice, but they usually have difficulty quantifying the optimal performance of the control system and cannot reflect the deviation between the system and the optimal performance, resulting in insufficient accuracy of the evaluation results. Summary of the Invention

[0004] The purpose of the present invention is to solve the deficiencies existing in the prior art and provide a method for evaluating the performance of an industrial process control system. This method is based on the system model, uses the internal model principle to design an optimal PID controller, calculates the optimal performance of the system on this basis, and combines the performance indicators of the current actual system to give the system performance evaluation result. Specifically, it includes the following steps:

[0005] 1) Based on the system model, design an equivalent PID controller by combining the internal model principle;

[0006] 2) Based on the designed PID controller, conduct system simulation and calculate the simulation control performance index δ * , and this performance index includes overshoot rise time steady-state error and settling time

[0007] 3) Collect data of the current actual system and calculate the actual control performance index δ′, and this performance index includes overshoot δ' OS , rise time δ' RT , steady-state error δ' SE and settling time δ' ST ;

[0008] 4) According to the simulation control performance index and the actual control performance index, calculate each control performance evaluation index h respectively, and the calculation formula is:

[0009]

[0010] 5) Calculate the system performance evaluation result by taking the average according to each control performance evaluation index h. According to the system performance evaluation result Judge the system performance.

[0011] The present invention designs an optimal PID controller by combining the internal model principle through a system model, calculates the control performance indexes of the closed-loop system, compares with the performance indexes of the current actual system, and gives the system performance evaluation result. This method makes full use of the system model, scientifically quantifies the optimal performance, can accurately diagnose the advantages and disadvantages of the actual system performance, and provides a reliable basis for subsequent system optimization.

[0012] More specifically, the steps of the present invention are as follows:

[0013] Step 1: Design an equivalent PID controller by the internal model principle, and the system model is:

[0014]

[0015] where k represents the system gain, and τ1 and τ2 represent time constants; when τ2 = 0, it will degenerate into a first-order model.

[0016] The internal model controller g c (s) is:

[0017]

[0018] where f(s) is a first-order filter and can be expressed as:

[0019]

[0020] where λ is the filter parameter.

[0021] Equivalent the internal model controller to a PID controller to obtain the parameters of the equivalent PID controller:

[0022]

[0023] where each parameter is expressed as:

[0024]

[0025] When the system model is first-order, let τ2 = 0, then the optimal PID parameters of the first-order system are obtained:

[0026]

[0027] Step 2: Collect simulation data and calculate the control performance indicators of the system, including:

[0028] 1) Overshoot

[0029]

[0030] where, is the maximum peak value of the system, is the steady-state value of the system;

[0031] 2) Rise time

[0032]

[0033] where, is the time when the system response reaches 90% of the steady-state value, is the time when the system response reaches 10% of the steady-state value;

[0034] 3) Steady-state error

[0035]

[0036] where y ref represents the set value;

[0037] 4) Settling time

[0038] is the time for the response from t 10％ to the response to remain within range.

[0039] Step 3: Collect data of the current actual system and calculate the control performance indicators of the current actual system, including overshoot δ', OS rise time δ', RT steady-state error δ', SE settling time δ', ST and the calculation method is the same as that in Step 2.

[0040] Step 4: Calculate each control performance evaluation indicator:

[0041]

[0042] where h RT h OS h SE and h ST respectively represent the evaluation indicators of overshoot, rise time, steady-state error and settling time.

[0043] Step 5: Calculate the system performance evaluation results

[0044]

[0045] According to the evaluation results Refer to Table 1 to give the system performance evaluation level.

[0046] Table 1 System performance evaluation level division

[0047]

[0048] Beneficial effects:

[0049] The present invention discloses a method for evaluating the performance of an industrial process control system, which can effectively solve the problems of difficult quantification of optimal performance and insufficient evaluation accuracy in traditional performance evaluation methods. This method uses the existing system model, combines the internal model principle to design an equivalent PID controller, calculates the control performance index of the closed-loop system, and compares it with the control performance of the current actual system to quantify the performance of the system. The present invention can accurately evaluate the advantages and disadvantages of the actual control performance, provide a quantitative basis for the optimization and adjustment of the controller, and improve the production efficiency. Description of the drawings

[0050] Figure 1 It is the principle block diagram of the internal model controller adopted by a method for evaluating the performance of an industrial process control system of the present invention;

[0051] Figure 2 It is the step response comparison between the current system and the equivalent system. Specific implementation manners

[0052] The following details the embodiments of the present invention. This embodiment is implemented on the premise of the technical solution of the present invention, and gives the detailed implementation manners and specific operation processes, but the protection scope of the present invention is not limited to the following embodiments.

[0053] Considering that a first-order system can be degenerated from a second-order system, a second-order industrial system is taken as an example here. Now, a performance evaluation method based on the internal model principle is adopted, and the control performance of the system is comprehensively evaluated by designing an equivalent PID controller, calculating the optimal closed-loop performance index, and comparing it with the actual step response data.

[0054] The specific implementation steps are as follows:

[0055] 1) Use system identification technology to obtain the second-order system model of the controlled object as:

[0056]

[0057] According to the internal model principle, take λ = 2, then the first-order filter It can be designed as:

[0058]

[0059] The principle block diagram of the internal model controller is as Figure 1 shown. To further simplify, the part within the dashed box is combined, and the equivalent controller can be expressed as:

[0060]

[0061] Substituting formulas (1) and (2) into formula (3), it can be sorted out to obtain:

[0062]

[0063] 2) Based on the internal model principle and the second-order system model, design an equivalent PID controller:

[0064]

[0065] By comparing formula (4) and formula (5), it can be obtained that:

[0066]

[0067] 3) According to the designed equivalent PID controller, calculate the dynamic performance indexes of the closed-loop system under the input of a step signal, which are respectively:

[0068]

[0069] 4) Run the actual control system, collect the output response data of the system under the input of a step signal, and then calculate the performance indexes of the actual system, which are respectively:

[0070] δ' RT = 2.74 s, δ' OS = 15.11%, δ' ST = 8.70 s, δ' SE = 0.00358.

[0071] 5) Performance comparison and analysis:

[0072] As Figure 2 shown, compare the control performance indexes of the actual system with the optimal control performance indexes, and calculate the system performance evaluation results

[0073]

[0074] 6) According to the numerical range of the performance evaluation results Since The level is A, so the system performance is excellent and no improvement is needed.

[0075] Through this embodiment, the applicability of the performance evaluation method based on the internal model principle to industrial process systems is illustrated. This method can effectively combine theory with practice, accurately quantify the control performance of the control system, and provide a reliable basis for the optimal design and performance improvement of industrial control systems.

Claims

1. An industrial process control system performance evaluation method, characterized in that, The industrial process control system performance evaluation method includes the following steps: 1) Based on the system model, design an equivalent PID controller in combination with the internal model principle; 2) Based on the designed PID controller, conduct system simulation and calculate the simulation control performance index δ of the closed-loop system * , which includes overshoot rise time steady-state error and settling time 3) Collect data of the current actual system and calculate the actual control performance index δ′, which includes overshoot δ', OS rise time δ', RT steady-state error δ', SE and settling time δ'. ST ; 4) According to the simulation control performance index and the actual control performance index, calculate each control performance evaluation index h respectively. The calculation formula is: 5) Calculate the system performance evaluation result by taking the average according to each control performance evaluation index h According to the system performance evaluation result Determine the system performance.

2. The performance evaluation method for an industrial process control system according to claim 1, wherein In step (5), according to the system performance evaluation results The specific method for determining the system performance is as follows: According to the system performance evaluation results Conduct system performance level division: When the system performance level is "A", it is determined that the system performance is excellent and no improvement is required; When the system performance level is "B", it is determined that the system performance is good and it can continue to be used; When the system performance level is "C", it is determined that the system performance needs to be improved; When the system performance level is "D", it is determined that the system cannot be used and needs to be redesigned.

3. The performance evaluation method of the industrial process control system according to claim 2, wherein The system model Adopts the following structure: where k represents the system gain, and τ1 and τ2 represent the time constants; when τ2 = 0, it will degenerate into a first-order model.

4. The industrial process control system performance evaluation method according to claim 3, characterized in that The method for designing the equivalent PID controller in step (1) is as follows: Based on the system model Design the internal model controller g c (s), and the expression is as follows: Among them, f(s) is a first-order filter: where λ is the filter parameter; The internal model controller \(g\) c (s) is equivalent to a PID controller to obtain the equivalent PID controller parameters, and the expression is as follows: where each parameter is expressed as: When the system model is first-order, let τ2 = 0 to obtain the optimal PID parameters of the first-order system:

5. The industrial process control system performance evaluation method according to claim 4, wherein The calculation method of each performance index is as follows: Among them, δ OS is the overshoot of the system, including and δ' OS ; y max is the maximum peak value of the system output y, and y ss is the steady-state value; Among them, δ RT is the rise time of the system, including and δ' RT ; t 90％ is the time taken for the system response to reach 90% of the steady-state value, and t 10％ is the time taken for the system response to reach 10% of the steady-state value; δ SE = y ref -y ss , Among them, δ SE is the steady-state error of the system, including and δ' SE ; y ref represents the set value, and y ss is the steady-state value; The adjustment time δ of the system ST is the time for the system response to go from t 10％ to when the response remains within y ss ±5% y ss , including and δ' ST .

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