Anti-disturbance control method for high altitude platform air intake system based on non-smooth feedback function

Abstract

The anti-disturbance control method of the high-altitude platform air intake system based on the non-smooth feedback function of the present invention includes 1. establishing the main equipment characteristic models such as the cavity pressure model, the regulating valve flow model and the regulating valve control model of the high-altitude platform air intake control system, and constructing an approximate second-order system model of the air intake control system; 2. designing a non-smooth feedback function algorithm; 3. constructing a nonlinear enhanced filtering algorithm; 4. introducing adjustment signal amplitude parameters and phase compensation parameters to improve the signal processing capability of the nonlinear enhanced filtering algorithm; 5. feeding back the pressure output filter signal obtained in 4 to the non-smooth feedback sliding mode controller obtained in 2, and the non-smooth feedback sliding mode controller algorithm and the nonlinear enhanced filtering algorithm are used together in the air intake control system to realize the control of the intake pressure in the transient state test of the aircraft engine. Step 6: repeat the above 2 to 5.

Description

Technical Field

[0001] The invention belongs to the technical field of high-altitude simulation control of aircraft engines, and in particular relates to an anti-disturbance control method for an air intake system of a high-altitude platform based on a non-smooth feedback function. Background Art

[0002] The aircraft engine high-altitude simulation test bench (abbreviated as high-altitude test bench) is a test bench on the ground that can simulate the altitude, speed and intake distortion conditions of various types of aircraft engines in the air. It is one of the indispensable and most effective experimental equipment for the development of advanced aircraft engines and propulsion systems. The flight environment simulation control system is an important part of the high-altitude test bench, especially the intake environment simulation control system, which plays an extremely important role in the entire high-altitude simulation test. Its control quality and adjustment performance are directly related to the test safety of the tested engine and the accuracy of the simulation of the aerodynamic boundary conditions.

[0003] There are a large number of disturbance sources in the high-altitude flight environment simulation transition state test, such as complex characteristic changes in the wide flight envelope of the tested engine, changes in pipeline volume characteristics, changes in the aerodynamic characteristics of the exhaust diffuser, changes in the throttling and clearance characteristics of the regulating valve, etc. These large number of disturbance factors will have a significant impact on the stability and dynamic performance of the control system during the test, becoming a bottleneck problem restricting the improvement of control quality. In terms of the design of the flight environment simulation control system controller, domestic and foreign units with high-altitude simulation tests of aircraft engines have carried out a large number of studies on transition state control methods. The Arnold Engineering Development Center (AEDC) in the United States has carried out a large amount of basic equipment characteristic modeling and simulation work for the controlled system, established a relatively complete system model, and on this basis, carried out classical control algorithms such as gain scheduling control, adaptive control, and model predictive control. These research results have greatly improved the level of flight environment simulation control of aircraft engines and provided a solid foundation for the development of new aircraft engines. The University of Stuttgart in Germany has established a digital flight environment simulation control system and a hardware-in-the-loop simulation system for its high-altitude simulation test bench. Based on this simulation system, it has developed composite control and feedforward control technologies, greatly improving the adjustment capability of the intake control system in transition state tests.

[0004] The technology actually used in the current high-altitude platform flight environment simulation system in my country still revolves around the classic error feedback PID control. The linear feedback form used in the current system is inefficient and the steady-state error of the closed-loop system is inversely proportional to the feedback gain. When the system needs to reduce the final steady-state error, there are two aspects of linear feedback. On the one hand, increasing the feedback gain may make the feedback control amount too large, causing the regulating valve to be unable to increase the energy to achieve it. On the other hand, if integral feedback is introduced, the control amount may be saturated. In addition, due to internal and external factors such as the sensor's own constraints, overall line layout, environmental noise, system disturbances, etc., the control output of the flight environment simulation control system contains a high intensity of random noise, which further aggravates the control difficulty of the control system. Summary of the invention

[0005] In view of this, a control system for the temperature of a sampling probe of high-frequency induction heating is proposed to solve the technical problem of low efficiency of traditional linear feedback control.

[0006] A method for anti-disturbance control of an air intake system of an altitude platform based on a non-smooth feedback function is provided, which comprises the following steps:

[0007] Step 1: at least establish a cavity pressure model, a regulating valve flow model and a regulating valve control model of the high-altitude platform air intake control system, and determine a second-order system model of the air intake control system;

[0008] Step 2: Determine the non-smooth feedback function algorithm based on the constructed second-order system model;

[0009] Step 3: Based on a typical second-order integral system, the non-linear enhanced filtering algorithm is constructed by applying the non-smooth feedback function;

[0010] Step 4: introducing a signal processing method for adjusting the signal amplitude parameter and the phase compensation parameter to improve the nonlinear enhancement filtering algorithm, and inputting the pressure output signal in the intake control system into the nonlinear enhancement filtering algorithm to obtain an effective pressure output filtering signal;

[0011] Step 5: The pressure output filter signal is fed back to the non-smooth feedback sliding mode controller, and the non-smooth feedback sliding mode controller algorithm and the nonlinear enhanced filtering algorithm are used together in the intake control system to control the intake pressure in the aircraft engine transient state test.

[0012] Step 6: Repeat the above steps 2 to 5 to perform real-time control of the intake pressure in the aircraft engine transient state test to ensure the accuracy of the experimental control.

[0013] The technical beneficial effects of the present invention are:

[0014] The present invention aims at the technical problem of intake control in flight environment simulation in transition state test of aircraft engine, designs a sliding mode control strategy based on non-smooth feedback, and designs a nonlinear enhancement filter based on the non-smooth feedback to perform real-time filtering processing on the output signal as the state feedback input of the main controller. The combined effect of these two algorithms greatly improves the control quality of the transition state of the flight environment simulation control system, including the processing of filtering and the improvement of control accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0016] Figure 1 Schematic diagram of the anti-disturbance control of the intake system based on non-smooth feedback function;

[0017] Figure 2 Schematic diagram of the nonlinear enhancement filter algorithm based on non-smooth feedback function;

[0018] Figure 3 Signal tracking filtering effect diagram of nonlinear enhancement filter algorithm;

[0019] Figure 4 The effect diagram of the intake system anti-disturbance control based on the non-smooth feedback function under disturbance conditions;

[0020] Figure 5 Control effect diagram of intake system based on PID control under disturbance conditions;

[0021] Figure 6 Anti-disturbance control of intake system based on non-smooth feedback function under disturbance conditions. DETAILED DESCRIPTION

[0022] The embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.

[0023] The following describes the embodiments of the present disclosure through specific examples, and those skilled in the art can easily understand other advantages and effects of the present disclosure from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, rather than all of the embodiments. The present disclosure can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present disclosure. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present disclosure.

[0024] It should be noted that various aspects of the embodiments within the scope of the appended claims are described below. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on the present disclosure, it should be understood by those skilled in the art that an aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects described herein can be used to implement the device and / or practice the method. In addition, other structures and / or functionalities other than one or more of the aspects described herein can be used to implement this device and / or practice this method.

[0025] Aiming at the technical problems of flight environment simulation intake control in aircraft engine transient state test, a sliding mode control strategy based on non-smooth feedback is designed. Based on the non-smooth feedback, a nonlinear enhancement filter is designed to perform real-time filtering on the output signal as the state feedback input of the main controller. The combined effect of these two algorithms greatly improves the control quality of the transient state of the flight environment simulation control system. The anti-disturbance control principle of the intake system based on the non-smooth feedback function is as follows: Figure 1 As shown, the principle of the nonlinear enhancement filter algorithm based on the non-smooth feedback function is as follows Figure 2 The present invention provides an anti-disturbance control method for an air intake system of an altitude platform based on a non-smooth feedback function. The air intake system of the altitude platform is a system in the prior art, which includes the following steps:

[0026] Step 1: At least establish the cavity pressure model, regulating valve flow model and regulating valve control model of the high-altitude platform air intake control system, and determine the second-order system model of the air intake control system, specifically:

[0027] 1.1: Control model of the regulating valve, system modeling is carried out for the intake ambient pressure control system. First, through the mechanism and data model identification method, the regulating valve control model (G1(s)) between the control quantity and the equivalent cross-sectional area A of the regulating valve is obtained:

[0028] ,in is the proportionality coefficient, is the time constant. There is a positive correlation with the equivalent cross-sectional area A of the regulating valve, and the coefficient is K1;

[0029] 1.2: Traffic model (G2(s))

[0030] Establish the equivalent cross-sectional area A of the regulating valve and the flow rate The flow model of the regulating valve between is:

[0031] ,in is the flow coefficient, P1 is the pressure before the regulating valve, is the air density.

[0032] 1.3: The cavity pressure model between the regulating valve flow and the cavity pressure is:

[0033] , where Kf is the proportional coefficient between flow and pressure, and Tf is the time constant between flow and pressure.

[0034] 1.4: Based on the main equipment characteristic models such as the cavity pressure model, regulating valve flow model and regulating valve control model of the above-mentioned high-altitude platform intake system, the approximate second-order system model of the intake pressure control system can be obtained as follows:

[0035] , where state x is the controlled output of the system, i.e., pressure; f is the disturbance to the system; a1 and a2 are system model parameters, b is the control input gain, and u is the control input of the controlled system, which determines the transfer relationship between the three dependent variables mentioned above.

[0036] Step 2: Determine the non-smooth feedback function algorithm based on the constructed second-order system model. The algorithm is executed by the controller. Specifically:

[0037] 2.1: The model of the high-altitude platform inlet pressure control system in step 1 (the second-order system model is) is further transformed into: Transformed into a state space model, satisfying:

[0038]

[0039] in is the state variable of the system, including the pressure output and the differential of the pressure output; w is the equivalent total disturbance sum of the system, including the disturbance in formula (4) and the uncertain part of the system model parameters; n1 is the random noise contained in the controlled output of the system, and the remaining variables are consistent with those specified in formula (4);

[0040] 2.2: Non-smooth feedback function algorithm satisfies:

[0041] ,

[0042] in, is a new saturation switching function, which is used to switch the sliding mode form in the formula, so that the state can reduce the vibration phenomenon during the transfer process; h is the sampling step of the intake pressure control system; r is the constrained extreme value of the control quantity and is related to the speed of the system state transfer process; is the intermediate variable in the process of constructing the control quantity; U a and U b is the intermediate control quantity; u is the control quantity finally applied to the controlled object of the intake control system, which is recorded as follows: .

[0043] This control form is based on the construction form of the sliding mode variable structure control algorithm of the non-smooth feedback function, in which when the state is outside the non-smooth sliding surface and on the non-smooth sliding surface, different control quantities are selected to make the state variables x1 and x2 quickly reach the origin.

[0044] In order to improve the control efficiency of the controller and overcome the low efficiency of traditional linear feedback control, equation (5) plays two roles: the combination of control and filtering.

[0045] Step 3: Based on a typical second-order integral system, the non-smooth feedback function is applied to construct a nonlinear enhanced filtering algorithm, that is, a filtering controller is set to perform filtering, specifically:

[0046] 3.1: The controlled pressure output of the high-altitude platform air intake control system contains high-intensity random noise. The existence of this noise will lead to a decrease in the performance of the final non-smooth feedback sliding mode control algorithm. For this reason, a nonlinear enhanced filtering algorithm is designed based on the non-smooth feedback function obtained by formula (6) to effectively filter the output of the controlled system. In the process of filter design, it is independent of the specific mathematical model of the air intake system and can be directly designed based on a typical second-order integral system. Specifically, based on the following typical second-order integral series system, it satisfies:

[0047] ,in, is the system state of a typical second-order integral system; The control quantity to be designed for the algorithm.

[0048] 3.2: Therefore, the control quantity designed in formula (6) is selected here to form the following nonlinear enhancement filter algorithm to satisfy:

[0049]

[0050] in, is the filtering output of the nonlinear enhancement filter; is the differential output of the nonlinear enhancement filter; h is the sampling step of the discrete system; k=0,1,⋯ is the control step of the discretized system; It is the amplitude adjustment parameter of the nonlinear enhancement filtering algorithm, used to achieve amplitude following; It is the fast factor of the nonlinear enhancement filtering algorithm, which is used to achieve fast signal tracking; It is the filter factor of the nonlinear enhancement filter algorithm, which is used to realize the signal smoothing function.

[0051] Step 4: Introduce a signal processing method for adjusting the signal amplitude parameter and the phase compensation parameter to improve the nonlinear enhancement filtering algorithm, and input the pressure output signal in the intake control system into the nonlinear enhancement filtering algorithm to obtain an effective pressure output filtering signal, the purpose is to strengthen the filter process, specifically:

[0052] 4.1: Based on formula (8), the phase compensation parameter is further introduced to improve the signal processing capability of the nonlinear enhancement filtering algorithm. A nonlinear enhancement filtering algorithm with both signal amplitude adjustment and phase compensation adjustment capabilities is designed. The pressure output signal in the flight environment simulation intake control system is input into the designed nonlinear enhancement filtering algorithm to obtain an effective pressure output filter signal. The purpose of the complete nonlinear enhancement filtering algorithm is to avoid distortion of the controlled signal and achieve high-precision and small phase extraction of the filter signal.

[0053] 4.2: Complete nonlinear enhancement filtering algorithm

[0054]

[0055] in, It is the pressure output signal sequence of the intake control system; is the phase compensation parameter of the nonlinear enhancement filtering algorithm; It is the pressure output filter signal output by the nonlinear enhancement filter algorithm.

[0056] Step 5: The pressure output filter signal is fed back to the non-smooth feedback sliding mode controller, and the non-smooth feedback sliding mode controller algorithm and the nonlinear enhanced filtering algorithm are used together in the intake control system to control the intake pressure in the aircraft engine transient state test. Specifically:

[0057] For the intake system (5), the non-smooth feedback controller algorithm given by formula (6) is adopted, and the nonlinear enhancement filter algorithm given by formula (9) is adopted at the same time. The two algorithms are applied together in the intake control system of the high-altitude platform to realize the environmental simulation intake pressure control of the aircraft engine transient state test.

[0058] Step 6: Repeat the above steps 2 to 5 to perform real-time control of the intake pressure in the aircraft engine transient state test to ensure the accuracy of the experimental control.

[0059] The method in this case is carried out simultaneously and synchronously through closed-loop control, with a short response time, which can better fit the dynamic changes of the actual test simulation device. In the air intake control system of the high-altitude platform, there are strong internal and external disturbances due to changes in the test tasks of the test engine, and at the same time, there is strong random noise interference in the pressure output signal. By constructing a non-smooth feedback mechanism, a nonlinear enhanced filter algorithm is designed for filtering the pressure output signal; at the same time, a non-smooth feedback sliding mode controller is designed for the main controller design of the system. The nonlinear enhanced filter has the characteristics of fast speed, small overshoot, and following the input signal without jitter. It also has the characteristics of high smoothness and phase lag that meets actual requirements. The designed non-smooth feedback sliding mode controller has the dynamic control quality of fast overshoot and small overshoot under disturbance, and at the same time, it has high steady-state accuracy and strong robustness.

[0060] As a specific implementation method provided in this case, the non-smooth feedback function adopts a nonlinear enhanced filtering algorithm to filter the pressure signal, and adopts a non-smooth feedback function to design a sliding mode feedback to the controller.

[0061] Implementation Effect

[0062] In order to verify the anti-interference control effect of the air intake system of the high-altitude platform flight environment simulation system based on the non-smooth feedback function proposed in the present invention, including the tracking filtering effect of the nonlinear enhancement filter algorithm and the control effect of the non-smooth feedback sliding mode control algorithm, the following simulation of the air intake pressure control system of a high-altitude platform is used to illustrate.

[0063] In the nonlinear enhancement filter algorithm based on the non-smooth feedback function, the input signal is given as ,

[0064] Among them, 0.085*rand(1) is a random noise with energy of 1, and the signal-to-noise ratio is about 20dB. For the designed nonlinear enhancement filter algorithm, the parameters involved are adjusted by trial and error, where the sampling step is 0.001s. , C_filter=50; the amplitude enhancement parameter σ of the nonlinear enhancement filtering algorithm is 1.15; the phase compensation parameter μ of the nonlinear enhancement filtering algorithm is 0.05. The specific effect is as follows Figure 3 shown.

[0065] In a flight environment simulation control system of a certain high-altitude platform, the throttle lever is simulated to move suddenly during 80s-160s, resulting in a rapid change in the engine intake air flow rate. The parameter selection is consistent with the above numerical simulation example. The specific effect is as follows Figure 4 , Figure 5 , Figure 6 As shown. Figure 4 , Figure 5 By comparison, the anti-disturbance control method of the high-altitude platform air intake system based on non-smooth feedback function significantly improves the anti-disturbance ability and control accuracy of the control system compared with the PID control method, while greatly shortening the adjustment time. Figure 6 It shows that under the action of the anti-disturbance control method of the intake system based on the non-smooth feedback function, the control output can achieve a smooth and non-vibration transition. It also shows that the use of nonlinear enhanced filtering algorithm in the control process can significantly weaken the influence of random noise in the system.

[0066] The above are only specific embodiments of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present disclosure should be included in the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be based on the protection scope of the claims.

Claims

1. A method for anti-disturbance control of an air intake system of a high altitude platform based on a non-smooth feedback function, characterized in that: The following steps are involved: Step 1: at least establish a cavity pressure model, a regulating valve flow model and a regulating valve control model of the high-altitude platform air intake control system, and determine a second-order system model of the air intake control system; Step 2: Determine the non-smooth feedback function algorithm based on the constructed second-order system model, including transforming the model of the intake pressure control system and satisfying: , where is the state variable of the system, including the pressure output and the differential of the pressure output; w is the equivalent total disturbance sum of the system; n1 is the random noise contained in the controlled output of the system; The following non-smooth feedback function algorithm is obtained: ， in, is a new saturation switching function, which is used to switch the sliding mode form in the formula, so that the state can reduce the vibration phenomenon during the transfer process; h is the sampling step of the intake pressure control system; r is the constrained extreme value of the control quantity and is related to the speed of the system state transfer process; is the intermediate variable in the process of constructing the control quantity; U a and U b is the intermediate control quantity; u is the control quantity finally applied to the controlled object of the intake control system; The construction form of the sliding mode variable structure control algorithm based on the non-smooth feedback function, when the state is outside the non-smooth sliding surface and on the non-smooth sliding surface, different control quantities are selected to make the state variables x1 and x2 quickly reach the origin; Step 3: Based on a typical second-order integral system, the non-smooth feedback function is applied to construct a non-linear enhanced filtering algorithm, wherein the controlled pressure output of the high-altitude platform air intake control system contains relatively strong random noise, and the presence of noise leads to a decrease in the performance of the non-smooth feedback sliding mode control algorithm. A non-linear enhanced filtering algorithm is designed based on the non-smooth feedback function to effectively filter the pressure output of the controlled system, wherein the design is based on a typical second-order integral system, and the typical second-order integral system satisfies: , where is the system state of a typical second-order integral system, is the control quantity to be designed by the algorithm. The nonlinear enhancement filter algorithm designed according to the non-smooth feedback function satisfies: in, is the filtering output of the nonlinear enhancement filter; is the differential output of the nonlinear enhancement filter; h is the sampling step of the discrete system; k is the control step of the discretized system; It is the amplitude adjustment parameter of the nonlinear enhancement filtering algorithm, used to achieve amplitude following; It is the fast factor of the nonlinear enhancement filtering algorithm, which is used to achieve fast signal tracking; It is the filter factor of the nonlinear enhanced filtering algorithm, which is used to realize the smoothing function of the signal; Step 4: Introduce a signal processing method for adjusting the signal amplitude parameter and the phase compensation parameter to improve the nonlinear enhanced filtering algorithm, and input the pressure output signal in the intake control system into the nonlinear enhanced filtering algorithm to obtain an effective pressure output filter signal, wherein the phase compensation parameter is introduced to improve the signal processing capability of the nonlinear enhanced filtering algorithm, and the nonlinear enhanced filtering algorithm with the signal amplitude adjustment and phase compensation adjustment capabilities, inputs the pressure output signal in the flight environment simulation intake control system into the designed nonlinear enhanced filtering algorithm to obtain an effective pressure output filter signal, and the nonlinear enhanced filtering algorithm satisfies: ， in, It is the pressure output signal sequence of the intake control system; is the phase compensation parameter of the nonlinear enhancement filtering algorithm; It is the pressure output filter signal output by the nonlinear enhancement filter algorithm; Step 5: The pressure output filter signal is fed back to the non-smooth feedback sliding mode controller, and the non-smooth feedback sliding mode controller algorithm and the nonlinear enhancement filter algorithm are used together in the intake control system to control the intake pressure in the aircraft engine transient state test; Step 6: Repeat the above steps 2 to 5 to perform real-time control of the intake pressure in the aircraft engine transient state test to ensure the accuracy of the experimental control.

2. The anti-disturbance control method for the high altitude platform air intake system based on non-smooth feedback function according to claim 1 is characterized in that: The non-smooth feedback function adopts a nonlinear enhanced filtering algorithm to filter the pressure signal, and adopts the non-smooth feedback function to design a sliding mode feedback to the controller.

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