An anti-disturbance control system and parameter tuning method

Abstract

The present application discloses an anti-disturbance control system and parameter tuning method. The parameter tuning method is mainly aimed at control objects with external disturbances and model uncertainty in process control. The control object model is uniformly regarded as an integral series type object, and a low-pass filter is connected in series after the state error feedback control law. The anti-disturbance control system is combined with a disturbance observer. The anti-disturbance control system has the characteristics of few adjustable parameters, clear tuning direction, clear debugging rules and physical meanings, which can better meet the debugging habits of field control engineers and avoid the need to know the precise process object model and the problem of unclear debugging process. The present application is widely applicable to the field of industrial process automation control, especially to process control fields such as thermal power plants, petrochemicals, metallurgy and steel.

Description

Technical Field

[0001] The present application belongs to the field of automatic control technology, and specifically relates to an anti-disturbance control system and a parameter setting method. Background Art

[0002] Regulators with a PID controller structure are widely used in industrial control. In some complex control laws, the PID control algorithm is still used at the basic control level. In industrial processes, control systems are subject to various forms of disturbances, which can severely impact the system's ultimate control performance. However, PID control only has a limited suppressive effect on step disturbances due to the integrator, making it less effective in dealing with other internal and external disturbances. A disturbance observer equates the differences between the actual object and the nominal model caused by external disturbances and model parameter changes to the control input, thereby observing the equivalent disturbance and introducing equivalent compensation into the control to achieve complete control of the disturbance. Introducing a disturbance observer into a control system can effectively suppress the impact of external disturbances and disturbances caused by changes in the model's own parameters on the control system, thereby optimizing control performance.

[0003] The controller based on DOB disturbance observer improved according to the ADRC principle has a parameter tuning method that is far better than the standard DOB, and its order is one order lower than the ADRC of the same order. While the structure is optimized, it can ensure the same control effect, so this anti-disturbance system will have a better market prospect. Summary of the Invention

[0004] To address the above issues, the present invention provides an anti-disturbance control system and a parameter tuning method. The anti-disturbance system of the present invention can effectively compensate for external and internal disturbances of the system. The technical solution is as follows:

[0005] The first aspect of the present application provides an anti-disturbance control system, comprising: a controlled object G p (s), disturbance observer, state error feedback control law G c (s) and reference model G n (s);

[0006] The input of the disturbance observer is the input U of the controlled object and the output Y of the controlled object, and the output of the disturbance observer is have Among them, G n (s) is the n-order integral series reference model, Q(s) is the compensation function, At the same time ensure It is physically feasible that the observer output value of the disturbance-resistant system can approximately track the sum of the internal disturbance and the external disturbance of the system when it reaches a steady state.

[0007] For example, in the anti-disturbance control system provided in one embodiment, the state error feedback control law G c The input is the error e after subtracting the set value R and the output Y of the controlled object. The state error feedback control law G c The output of is U0, then U0=G c (RY), and G c satisfy:

[0008]

[0009] Let k1+k2s+…+k n s n-1 +s n =(s+ω c ) n ,in, It is an n-1 order low-pass filter, ω0 is the bandwidth of the disturbance observer, which can also be called the filtering parameter, b0 is the proportional band of the anti-disturbance controller, ω c is the bandwidth of the state error feedback control law.

[0010] For example, in the anti-disturbance control system provided in one embodiment, the state error feedback control law G c The input is the set value R and the output Y of the controlled object, and it satisfies the following expression:

[0011]

[0012] Let k1+k2s+…+k n s n-1 +s n =(s+ω c ) n ,in,

[0013] For example, in the anti-disturbance control system provided in one embodiment, when the reference model G n When (s) is in first-order form, the state error feedback control law is: The expression of the controller U of the disturbance observer based on DOB satisfies the following formula:

[0014]

[0015] Among them, ω c is the bandwidth of the state error feedback control law, and the reference model is inversely First-order compensation function Observer output value of disturbance rejection system When the steady state is reached, the sum of the internal and external disturbances of the system can be approximately tracked.

[0016] For example, in the anti-disturbance control system provided in one embodiment, when the state error feedback control law G c When (s) is in first-order form, the state error feedback control law parameter ω c The ratio of the filtering parameter ω0 is λ, that is, make but:

[0017] ω c =(1+λ)ω D ,

[0018] Among them, ω D is the bandwidth of the disturbance controller.

[0019] A second aspect of the present application provides a parameter tuning method for an anti-disturbance control system, comprising the following steps:

[0020] Step 1: configuring a control algorithm on a control system of a controlled object based on the state error feedback control law and the disturbance observer;

[0021] Step 2: Obtain the soaring curve of the controlled object, and obtain the steady-state gain K of the controlled object, the time parameter T of the approximate first-order plus pure delay system, and the delay time τ;

[0022] Step 3: When the controlled object is a first-order model, set ω D , the initial value of λ, b0, and the controller parameters are obtained;

[0023] Step 4: Debug based on the simulation platform and gradually adjust the steady-state gain b0 from the initial value so that the closed-loop control effect meets the performance index. If so, select the steady-state gain b0 and ω that meet the performance index. D , we get ω c and the best parameters of ω0, set the best parameters to the logic configuration completed in step 1, and put it into operation; if it is not satisfied, record the best b0 value and debug it based on the simulation platform, gradually reduce ω from the initial value D , each time ω is reduced D , gradually adjust the steady-state gain b0 from the optimal b0 value so that the closed-loop control effect meets the performance index, and then select the steady-state gain b0 and ω that meet the performance index. D , we get ω c and the optimal parameters of ω0, set the optimal parameters to the logic configuration completed in step 1, and put it into operation; the performance indicators include closed-loop adjustment time less than or equal to the design value t s2 And the system has no overshoot.

[0024] For example, in the parameter tuning method of the anti-disturbance control system provided in one embodiment, in step 1, the control system of the controlled object includes a DCS control system and a PLC control system.

[0025] For example, in the parameter tuning method of the anti-disturbance control system provided in one embodiment, in step 4, the initial value b0 of the control system is:

[0026] For example, in the parameter tuning method of the anti-disturbance control system provided in one embodiment, the bandwidth ω of the disturbance observer is D The initial value of is:

[0027] For example, in the parameter tuning method of the disturbance rejection control system provided in one embodiment, when the system adopts a first-order DOB disturbance observer, the initial value of λ is 0.1.

[0028] The beneficial effects brought about by the anti-disturbance control system and parameter tuning method of the present application are as follows: the anti-disturbance system of the present application can effectively compensate for the external disturbances and internal disturbances of the system. The parameter tuning method of the present application is mainly aimed at the control objects with external disturbances and model uncertainty in process control. The control object model is uniformly regarded as an integral series type object, and a low-pass filter is connected in series after the state error feedback control law. The anti-disturbance control system is composed of a disturbance observer, which has the characteristics of few adjustable parameters, clear tuning direction, clear debugging rules and physical meanings. It can better meet the debugging habits of on-site control engineers and avoid the problem of needing to know the precise process object model and unclear debugging process.

[0029] This application is widely applicable to the field of industrial process automation control, especially to process control fields such as thermal power plants, petrochemicals, and steel metallurgy. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0031] Figure 1 is a structural diagram of the anti-disturbance control system and parameter tuning method in Example 1;

[0032] Figure 2 is a disturbance observer control system output response diagram of the anti-disturbance system in Example 3;

[0033] Figure 3This is a comparison diagram of the output responses of the same object system controlled by different anti-disturbance systems in Example 4;

[0034] Figure 4 It is a comparison chart between the external disturbance setting value and the standard DOB and anti-disturbance system disturbance;

[0035] Figure 5 is a comparison diagram of the output value of the anti-disturbance system and the output value of the ADRC system in Example 4;

[0036] Figure 6 This is a soaring curve diagram of the main steam temperature system in Example 5;

[0037] Figure 7 This is the output response diagram of the main steam temperature system controlled by the anti-disturbance system in Example 5. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0039] Unless otherwise defined, the technical or scientific terms used in this disclosure should have the usual meanings understood by persons of ordinary skill in the field to which this disclosure belongs. The words "first", "second" and similar terms used in this disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. Words such as "include" or "comprise" mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Words such as "connect" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0040] The first aspect of the present application provides an anti-disturbance control system, comprising: a controlled object G p (s), disturbance observer, state error feedback control law G c (s) and reference model G n (s); The input of the disturbance observer is the input U of the controlled object and the output Y of the controlled object, and the output of the disturbance observer is The output of the disturbance observer Satisfies the following formula:

[0041]

[0042] Among them, G n (s) is the reference model, Q(s) is the compensation function, and it is guaranteed Physically achievable. The n-order reference model G n (s), using integral series type The compensation function is The state error feedback control law G c The input is the set value R and the output Y of the controlled object. The difference between them is the error e, and the output is U0. So e=RY; U0=eG c Considering that the state error feedback control law Gc needs to be physically realizable, we have:

[0043]

[0044] Let k1+k2s+…+k n s n-1 +s n =(s+ω c ) n ,in, Then there is

[0045]

[0046] in, It is an n-1 order low-pass filter, ω0 is the bandwidth of the disturbance observer, which can also be called the filtering parameter, and b0 is the proportional band of the anti-disturbance controller.

[0047] in It is an n-1 order low-pass filter, and b0 is the parameter b0 in the reference model.

[0048] In order to reduce the controller parameters, let k1+k2s+…+k n s n-1 +s n =(s+ω c ) n ,in, The n-order state error feedback control law G obtained by sorting c The formula is as follows:

[0049]

[0050] The output of the controller, U, is equal to the output of the error feedback control law, U0, minus the output of the disturbance observer. Right now Set U0=G c (RY), Substituting them respectively, we get the expression of the controller U based on the DOB disturbance observer, and sorting out the formula:

[0051]

[0052] The expression of the controller U of the disturbance observer based on DOB satisfies the following formula:

[0053]

[0054] For example, in the anti-disturbance control system provided in one embodiment, when the state error feedback control law G c When (s) is of first-order form, we have ω c is the bandwidth of the state error feedback control law, and the reference model is inversely First-order compensation function Substituting the reference model and controller into the expression of the controller output U based on the disturbance observer, we get:

[0055]

[0056] Example 1:

[0057] A disturbance rejection control system, such as Figure 1 As shown, the controlled object G p (s), disturbance observer, state error feedback control law G c (s) and reference model G n (s); The input of the disturbance observer is the input U of the controlled object and the output Y of the controlled object, and the output of the disturbance observer is The output of the disturbance observer Satisfies the following formula:

[0058]

[0059] Among them, G n (s) is the reference model, Q(s) is the compensation function, and it is guaranteed Physically achievable.

[0060] The output of the controller, U, is equal to the output of the error feedback control law, U0, minus the output of the disturbance observer. Right now Set U0=G c (RY), Substituting them respectively, we get the expression of the controller U based on the DOB disturbance observer, and sorting out the formula:

[0061]

[0062] According to the system closed-loop transfer function formula The closed-loop transfer function of the system with DOB can be obtained:

[0063]

[0064] Assume that the controlled object is Controller G c Only the proportional link, namely G R (s) = k c , the compensation function can be set as The reference model is Substitute the above expression into the closed-loop transfer function G b Formula, sorted out:

[0065]

[0066] Find the steady-state gain from the closed-loop transfer function This shows that the standard DOB control system cannot eliminate the steady-state error when the controller only has a proportional link, so the controller must be added with an integral link to eliminate the system steady-state error.

[0067] Change the controller form and add an integral link to the controller, that is, The compensation function can be set as The reference model is set to Substituting the above expression into the closed-loop characteristic equation of the system, we can obtain:

[0068] If the order but The necessary and sufficient condition for the root of is in the negative half plane (system stability condition) is For the standard DOB disturbance observer parameter ω0, a larger setting for ω0 results in better tracking of disturbances, but the system's stability requirements restrict the value of ω0. This shows that standard DOB systems with PI controllers face difficulties in parameter tuning.

[0069] Taking the first-order ADRC anti-disturbance system as an example, the ESO equation of the ADRC automatic disturbance rejection system is expanded to:

[0070]

[0071] Then the control quantity u of ADRC is:

[0072]

[0073] Assume that the standard DOB has a first-order controller G c =k c , set U0 = eG c =G c(RY) Substitution The formula is:

[0074]

[0075] By matching the ADRC control quantity u with the DOB control quantity formula U, we can obtain the controller, compensation function Q(s), and reference model in the following forms:

[0076]

[0077] The reference model G can be found n It is an integral series type.

[0078] If the reference model in the DOB disturbance observer adopts the integral series type, that is, Then it can replace the integral link provided by the PI controller in the system, and the controller Gc only retains the error state feedback, which is Controller G c The parameter b0 is set in to match the parameter b0 in the reference model. Meanwhile, the compensation function in the first-order DOB system is It is one order lower than Q1 in ADRC, which optimizes the controller structure. From this, we can get the control quantity output formula of the DOB disturbance observer of this application:

[0079]

[0080] The closed-loop transfer function of the system The characteristic equation of the system can be obtained:

[0081]

[0082] In order to conveniently configure the closed-loop transfer function zero poles, we can make From this we get ω c =(1+λ)ω D , where ω D is called the bandwidth of the disturbance observer. c The parameter ω c A mathematical relationship is established with the DOB parameter ω0, which further reduces the difficulty of system parameter tuning compared to the standard DOB.

[0083] Table 1 is a comparison of the standard DOB, ADRC anti-disturbance system, the controller, compensation link, and reference model of the anti-disturbance system. It can be seen from Table 1 that the reference models of the ADRC anti-disturbance system and the anti-disturbance system both adopt the integral series type, which makes the anti-disturbance system and ADRC able to track the sum of internal and external disturbances very well. Figure 4It can be seen that when the external disturbance setting value is 0.2, the anti-disturbance system and ADRC have better tracking capabilities than the standard DOB. The anti-disturbance system uses the same compensation function as the standard DOB, which is one order lower than the ADRC and has a simpler form. For a comparison of the control effects between the standard DOB, ADRC active disturbance rejection, and the DOB system of this application, please refer to Example 4.

[0084] Table 1: Comparison of disturbance observer forms

[0085]

[0086] Extended to n-order DOB, the reference model also needs to adopt n-order form State error feedback control law G c The n-order form of At the same time, in order to make the system physically feasible, the controller G c On the basis of the original form, an n-1 order low-pass filter is added in series Then there is Where b0 is the parameter b0 in the reference model.

[0087] In order to reduce the controller parameters, let k1+k2s+…+k n s n-1 +s n =(s+ω c ) n ,in, The n-order state error feedback control law G obtained by sorting c The formula is as follows:

[0088]

[0089] When the state error feedback control law is in first-order form, The reference model is inversely Compensation function Substituting into the control quantity U output formula based on the disturbance observer, the control quantity is:

[0090]

[0091] Example 2:

[0092] In Example 1, when the state error feedback control law is a first-order form, let the state error feedback control law ω c The ratio of the bandwidth and the filter parameter ω0 is λ, that is, At the same time Then we have ω c =(1+λ)ω D , where ω Dis called the bandwidth of the disturbance controller.

[0093] ω D The initial values ​​of and λ can be set as:

[0094] The steps for parameter tuning of the anti-disturbance control system are as follows:

[0095] Step 1: configuring a control algorithm on a control system of a controlled object based on the state error feedback control law and the disturbance observer;

[0096] Step 2: Obtain the soaring curve of the controlled object, and obtain the steady-state gain K of the controlled object, the time parameter T of the approximate first-order plus pure delay system, and the delay time τ;

[0097] Step 3: When the controlled object is a first-order model, set ω D , the initial value of λ, b0, and the controller parameters are obtained;

[0098] Step 4: Debug based on the simulation platform and gradually adjust the steady-state gain b0 from the initial value so that the closed-loop control effect meets the performance index. If so, select the steady-state gain b0 and ω that meet the performance index. D , we get ω c and the best parameters of ω0, set the best parameters to the logic configuration completed in step 1, and put it into operation; if it is not satisfied, record the best b0 value and debug it based on the simulation platform, gradually reduce ω from the initial value D , each time ω is reduced D , gradually adjust the steady-state gain b0 from the optimal b0 value so that the closed-loop control effect meets the performance index, and then select the steady-state gain b0 and ω that meet the performance index. D , we get ω c and the optimal parameters of ω0, set the optimal parameters to the logic configuration completed in step 1, and put it into operation; the performance indicators include closed-loop adjustment time less than or equal to the design value t s2 And the system has no overshoot.

[0099] The optimal parameter of b0 selected by the final control system is ω D The best parameters are

[0100] Example 3:

[0101] This embodiment uses the anti-disturbance control system and parameter tuning method of the present application to control the first-order object Simulate the control system and add external step disturbance. The inverse of the reference model is Low-pass filter First-order state error feedback control law

[0102] The parameter tuning method includes the following steps:

[0103] Step 1: Programming and configuring the anti-disturbance system and the controlled object based on the present application in simulation software;

[0104] Step 2: Set the initial value ω D =2,λ=0.1,b0=22;, according to the formula ω c =(1+λ)ω D , Get the initial value of system configuration parameters;

[0105] Step 3: Gradually adjust the steady-state gain b0 from the initial value so that the closed-loop control effect meets the performance index as much as possible. If it does not meet the performance index, record the optimal b0 value and proceed to step 4;

[0106] Step 4: Gradually reduce ω from the initial value D , each time ω is reduced D , gradually adjust the steady-state gain b0 from the optimal b0 value in step 3 until the closed-loop control obtains the best effect as shown in Figure 2 As shown, the parameter that ultimately achieves the best control effect is ω c =1.1, ω0=11, b0=22;

[0107] Example 4:

[0108] This embodiment uses the anti-disturbance control system and parameter tuning method of the present application to control the first-order object Compared with Example 3, this embodiment adds the ADRC system and the standard DOB disturbance observer as a comparison to further demonstrate the theoretical derivation process in Example 1. Finally, the best control effect is obtained. Figure 3 As shown, the optimal parameters are as follows:

[0109] Standard DOB optimal parameters: ω0 = 0.05, k c =0.43;

[0110] The best parameters for this application: λ = 0.1, ω c =1.1, ω0=11, b0=22;

[0111] Active disturbance rejection control system ADRC: λ=0.1,ω c =1.2, ω0=12, b0=12;

[0112] Depend on Figure 5 It can be seen that the output curve of this embodiment is very close to the output curve of ADRC, and the standard DOB has been unable to eliminate the residual error. At the same time, the controller structure of this application is simpler, and thus has better market prospects.

[0113] Example 5

[0114] This embodiment uses the anti-disturbance control system and parameter tuning method of the present application to perform anti-disturbance control on the superheater outlet temperature control of a 330MW unit. The temperature control model is as follows:

[0115]

[0116] Among them, P1(s) is the controlled object of the secondary loop, and P2(s) is the controlled object of the primary loop. The unit step response curve of the two connected in series is as follows: Figure 6 shown.

[0117] The system approximates the FOPTD model as follows:

[0118]

[0119] Step 1: Configure the control algorithm based on the PID controller in the control system of the controlled object;

[0120] In the second step, the soaring curve method is used on site to obtain the steady-state gain K of the controlled object, the time parameters T and τ of the approximate first-order inertia plus pure delay system, that is, K = -0.4, T = 130, τ = 64, and set the initial value ω D =0.00847, λ=0.1, b0=0.037.

[0121] Step 3: Debug based on the simulation platform and gradually adjust D And b0, each time the parameters are adjusted, according to the formula ω c =(1+λ)ω D , Calculate the latest ω c and ω0, and update the configuration program;

[0122] Step 4: Debug based on the simulation platform and finally adjust to get the best control effect. Figure 7 As shown, the optimal parameter ω is selected D =0.0092, b0=0.035, ω c =0.0101,ω0=0.101.

[0123] Although the embodiments of the present application have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims

1. An anti-disturbance control system, characterized in that: include: Accused object G p (s), disturbance observer, state error feedback control law G c (s) and reference model G n (s); The input of the disturbance observer is the input U of the controlled object and the output Y of the controlled object, and the output of the disturbance observer is have Among them, G n (s) is the n-order integral series reference model, Q(s) is the compensation function, Observer output value of disturbance rejection system When reaching steady state, it approximately tracks the sum of the internal disturbance and external disturbance of the system, where ω0 is the bandwidth of the disturbance observer and b0 is the proportional band of the disturbance rejection controller; The state error feedback control law G c The input is the error e after subtracting the set value R and the output Y of the controlled object. The state error feedback control law G c The output of is U0, then U0=G c (RY), and G c satisfy: Let k1+k2s+…+k n s n-1 +s n =(s+ω c ) n ,in, is an n-1 order low-pass filter, ω c is the bandwidth of the state error feedback control law; The state error feedback control law G c The input is the set value R and the output Y of the controlled object, and it satisfies the following expression: Let k1+k2s+…+k n s n-1 +s n =(s+ω c ) n ,in, When the reference model G n When (s) is in first-order form, the state error feedback control law is: The expression of the controller U of the disturbance observer based on DOB satisfies the following formula: Among them, ω c is the bandwidth of the state error feedback control law, and the reference model is inversely First-order compensation function The anti-disturbance control system includes the following steps: Step 1: configuring a control algorithm on a control system of a controlled object based on the state error feedback control law and the disturbance observer; Step 2: Obtain the soaring curve of the controlled object, and obtain the steady-state gain K of the controlled object, the time parameter T and the delay time τ of the approximate first-order plus pure delay system; Step 3: When the controlled object is a first-order model, that is, the state error feedback control law G c When (s) is in first-order form, the state error feedback control law parameter ω c The ratio of the bandwidth ω0 of the disturbance observer is λ, that is, make but: oh c =(1+λ)ω D , Among them, ω D is the bandwidth of the disturbance controller; Setting ω D , the initial value of λ, b0, and the controller parameters are obtained; Step 4: Debug based on the simulation platform and gradually adjust the steady-state gain b0 from the initial value so that the closed-loop control effect meets the performance index. If so, select the steady-state gain b0 and ω that meet the performance index. D , we get ω c and the best parameters of ω0, set the best parameters to the logic configuration completed in step 1, and put it into operation; if it is not satisfied, record the best b0 value and debug it based on the simulation platform, gradually reduce ω from the initial value D , each time ω is reduced D , gradually adjust the steady-state gain b0 from the optimal b0 value so that the closed-loop control effect meets the performance index, and then select the steady-state gain b0 and ω that meet the performance index. D , we get ω c and the optimal parameters of ω0, set the optimal parameters to the logic configuration completed in step 1, and put it into operation; the performance indicators include closed-loop adjustment time less than or equal to the design value t s2 And the system has no overshoot.

2. The anti-disturbance control system according to claim 1, characterized in that: In the step 1, the control system of the controlled object includes a DCS control system and a PLC control system.

3. The anti-disturbance control system according to claim 1, characterized in that: In step 4, the initial value of the control system b0 is:

4. The anti-disturbance control system according to claim 1, characterized in that: The bandwidth ω of the disturbance observer D The initial value of is:

5. The anti-disturbance control system according to claim 1, characterized in that: When the system adopts the first-order DOB disturbance observer, the initial value of λ is 0.1.

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