Method for controlling speed of spoiler of unpowered return-field aircraft based on active disturbance rejection control

Abstract

The invention discloses an unpowered returning-field aircraft spoiler speed control method based on active disturbance rejection control, belongs to the technical field of unmanned aerial vehicle flight control, and aims to solve the problem that high-precision speed control is difficult to realize due to insufficient robustness when a traditional spoiler control strategy faces a complex and changeable environment and unknown disturbance. According to the method, the expansion state observer introducing active disturbance rejection control is adopted, unmodeled dynamics and external disturbance in the system are estimated on line and compensated in real time, the speed deviation is responded in a short time, the adaptive capacity to unknown disturbance is remarkably improved in unpowered return field section spoiler speed control, and the speed control accuracy of the spoiler is improved. According to the method, the dependence on an accurate model is reduced, higher-precision and more robust speed control is realized, and an effective technical means is provided for safe, stable and accurate landing of unmanned aerial vehicles and other unpowered landing aircrafts.

Description

Technical Field

[0001] The invention belongs to the technical field of unmanned aerial vehicle flight control, and in particular relates to a spoiler speed control method for an aircraft in an unpowered return segment based on anti-disturbance control. Background Art

[0002] With the rapid development of aerospace technology and unmanned aerial vehicle (UAV) technology, UAVs need to return to the landing site safely and accurately after completing their missions. For aircraft in the unpowered return phase (such as some gliding spacecraft or unpowered cruising drones), speed control is particularly important when approaching the target landing point due to the loss or reduction of their own thrust. If the aircraft cannot effectively offset and suppress various external disturbances (such as airflow changes, wind field disturbances, aerodynamic parameter uncertainty, mass deviation, etc.) during the descent, it may cause flight trajectory deviation, overshoot or premature deceleration, thus posing a threat to precise landing.

[0003] In the field of flight control, spoilers, as a control surface that changes aerodynamic characteristics, have been widely used in deceleration and glide trajectory adjustment during gliding landing. Traditional spoiler control strategies often rely on fixed-gain PID controllers or control law designs based on deterministic models. However, in the actual return process, the environment in which the aircraft is located is complex and changeable, and the aerodynamic parameter estimation errors and external disturbances are difficult to accurately predict, resulting in insufficient robustness of traditional controllers to disturbances. The challenge facing aircraft speed control is how to effectively compensate and cancel unknown disturbances without relying on high-precision mathematical models and comprehensive parameter estimation, thereby achieving high-precision deceleration and speed tracking control.

[0004] Active Disturbance Rejection Control (ADRC) is a new control strategy based on the extended state observer (ESO). It can achieve real-time suppression of disturbances and control law adjustment by online estimation and compensation of unknown dynamic and disturbance factors of the system without accurate modeling of the system. Therefore, applying ADRC technology to the spoiler control of the unpowered return stage can greatly improve the accuracy and robustness of speed control, and provide the possibility for accurate speed management and safe landing of the aircraft during the unpowered taxiing stage. At present, there are relatively few studies on the application of active disturbance rejection control to spoiler control in the unpowered return stage. Summary of the invention

[0005] The present invention provides a spoiler speed control method for an aircraft in an unpowered return segment based on active anti-disturbance control, which improves the dynamic characteristics and enhances the loop control quality by dynamically estimating and compensating for the uncertain disturbance information of the aircraft in real time, thereby significantly improving the dynamic and steady-state performance of the aircraft.

[0006] To achieve the above objectives, the present invention adopts the following technical solutions:

[0007] A method for controlling the speed of an aircraft spoiler during an unpowered return phase based on an anti-disturbance control comprises the following steps:

[0008] S1: Measure the flight speed of the aircraft and establish the dynamic model of the aircraft in the longitudinal direction;

[0009] S2: Calculate the speed error based on the current measured speed and use ESO to estimate the disturbance term online;

[0010] S3: Based on the ESO’s estimation of the disturbance, the LADRC control law is used to perform feedback control on the speed deviation.

[0011] In the above steps, the spoiler is installed on the upper surface of the wing and can be quickly deflected within a small angle range. The deflection angle is Can be controlled in real time; the dynamic model of the aircraft in the longitudinal direction is:

[0012] ,

[0013] in, is the differential of velocity, is the coefficient of the controller, numerically , is the control input, which in this case represents the spoiler deflection, For external disturbance.

[0014] The designed linear extended state observer is in the form of:

[0015] ,

[0016] in, Respectively Observation, are the velocity and the derivative of velocity respectively, is the gain of the observer.

[0017] Set the target speed to The actual speed is , then the speed error is The control goal is to make the aircraft speed Able to quickly approach and maintain Nearby, so as to achieve accurate descent control, the final control law output is:

[0018] .

[0019] Beneficial effects: The present invention provides a spoiler speed control method for an unpowered return segment aircraft based on anti-disturbance control, which has the following advantages over the prior art:

[0020] 1. During the unpowered return process, the aircraft faces problems such as wind field disturbances, aerodynamic uncertainty and parameter deviations. Traditional control methods are difficult to identify and cancel these unknown disturbances in real time. The present invention introduces active disturbance rejection control, which can estimate the unmodeled dynamics and external disturbances in the system online and compensate for them in real time, thereby improving the robustness and adaptability of the control to disturbances.

[0021] 2. Traditional control strategies often rely on precise aerodynamic parameters and dynamic models. Once the parameter error is large or the environment changes dramatically, the speed control accuracy will drop significantly. The present invention uses an extended state observer with self-disturbance rejection control to extract unknown system dynamics online, so that the control law is no longer strictly dependent on high-precision mathematical models. It can achieve precise speed tracking control under a wider range of working conditions and disturbances, improve dynamic and steady-state performance, and enhance the versatility of the control system.

[0022] 3. The present invention does not require complicated parameter identification and optimization steps. The anti-disturbance controller can respond to speed deviations in a relatively short time while achieving precise disturbance compensation, which is conducive to achieving rapid and reliable deceleration and speed control of the aircraft within a short distance, ultimately ensuring that the return landing process is safer, smoother and more efficient, improving safety and landing accuracy, and is conducive to practical engineering applications.

[0023] 4. The method of the present invention is applicable to various types of fixed-wing UAVs and similar unpowered return aircraft, and provides a new approach and solution for improving the safety and control accuracy during unpowered taxiing and landing. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the structure of the speed controller LADRC in an embodiment of the present invention;

[0025] Figure 2 The second-order linear ESO Simulink block diagram of the embodiment of the present invention;

[0026] Figure 3 It is a curve diagram of the spoiler speed control simulation results in an embodiment of the present invention. DETAILED DESCRIPTION

[0027] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments:

[0028] The three main parts of the ADRC are: Tracking Differentiator (TD), Extended State Observer (ESO) and Nonlinear State Error Feedback (NLSEF). Among them, the tracking differentiator and the nonlinear error feedback control law can be used selectively, and the present invention only uses the extended state observer.

[0029] The extended state observer is the core of the entire ADRC technology, and its essence lies in the estimation of disturbances. Its function is to estimate the impact of unknown disturbances and uncertainties on the system in real time, and expand it into a new state variable, perform real-time compensation through the design of control quantities, and then transform the system into an integral series linear control system. If there is a state , output A first-order system, using Indicates the status The estimate is It represents the estimation of the sum of internal disturbance, external disturbance and all uncertainties. In this embodiment, an extended state observer is used, and its mathematical model is discretized and expressed as follows:

[0030] ,

[0031] In the formula, , is the observer gain, Respectively Observation, is the system state variable, For observation and output The error between is the sampling period after the system is discretized, is the time step of the discrete time series.

[0032] The spoiler speed control method based on LADRC control has a control structure such as Figure 1 As shown in the figure, for the force analysis of the aircraft in the forward direction, the spoiler can be used to increase the additional resistance to produce a certain deceleration (or achieve a certain acceleration under certain conditions). The required net force can be given by Newton's second law:

[0033] .

[0034] in, is the mass of the aircraft, is the acceleration.

[0035] Assuming that the deflection of the spoiler will introduce additional drag increment, the drag can be expressed as:

[0036] ,

[0037] in, is the spoiler deflection angle, is the increase in drag coefficient per unit spoiler deflection, dynamic pressure , is the air density, is the flight speed, is the reference area;

[0038] You can get:

[0039] ,

[0040] make , ,in, is the system output, is the coefficient of the controller, is the control signal, For unmodeled dynamics and external disturbances, the state space equation can be written as:

[0041] ,

[0042] in .

[0043] Design a linear extended state observer to observe the system. The observer form is:

[0044] ,

[0045] in, Respectively Observation, is the gain of the observer.

[0046] With proportional control, the closed-loop bandwidth of the speed controller is , the final control law output is:

[0047] .

[0048] This embodiment takes a certain type of unpowered return UAV as the object, and realizes precise speed control in the unpowered taxiing stage by setting controllable spoilers on the wings of the aircraft and using the linear active disturbance rejection control (LADRC) strategy. The steps of this embodiment include: system parameter measurement and modeling, extended state observer (ESO) parameter selection, control law design and implementation, and actual experimental verification.

[0049] 1. System composition and parameter measurement

[0050] The aircraft of this embodiment is a fixed-wing UAV, which is equipped with basic sensors such as an inertial measurement unit (IMU), a pitot tube, a GPS and an altimeter. During the unpowered return phase, the engine thrust is turned off or kept at the minimum, and the aircraft returns to the predetermined landing area by gliding.

[0051] (1) Spoiler layout: The spoiler is installed at a specific position on the upper surface of the wing and can be quickly deflected within a small angle range. The deflection angle is Can be controlled in real time;

[0052] (2) State quantity and feedback signal:

[0053] Output signal: flight speed ;

[0054] Input signal: spoiler deflection , achieved through the servo actuator;

[0055] (3) System model and parameters: Based on the above principles, a dynamic model of the aircraft in the longitudinal direction is established. The model form is:

[0056]

[0057] in, is the differential of velocity, is the coefficient of the controller, numerically , is the control input, which in this case represents the spoiler deflection, For external disturbance.

[0058] 2. Extended State Observer (ESO) design and parameter selection

[0059] This embodiment adopts a second-order linear extended state observer to perform online estimation of the system state and unknown disturbances to eliminate the adverse effects caused by external interference and model uncertainty.

[0060] (1) Definition of expansion state:

[0061] Design a linear extended state observer to observe the system. The observer form is:

[0062] ,

[0063] in, Respectively Observation, is the gain of the observer; Figure 2As shown, the observer has 6 inputs and 2 outputs, where input: signal 1 is the differential of the speed command, signal 2 is the output (speed in this example), signal 3 is the initial value of observation 2, signal 4 is the observer gain beta01, signal 5 is the observer gain beta02, and signal 6 is the time step T; output: signal 1 is the observation result z2 (in this example, the observation of speed), and signal 2 is the observation result z1 (observation of the total disturbance).

[0064] (2) ESO gain setting: The ESO gain parameters are selected according to the response characteristics of the aircraft and the expected control bandwidth, so that the ESO can accurately track and estimate the , the observer gain parameters can be adjusted through offline simulation and experiments, such as making the ESO bandwidth slightly higher than the closed-loop controller bandwidth to ensure fast estimation of unknown disturbances.

[0065] Figure 2 This is an example of a Simulink block diagram of a second-order linear ESO. In this implementation, the parameters can be adjusted according to different aircraft models and atmospheric environments. The bandwidth of the ESO determines the observer's response speed to disturbances and unmodeled dynamics. The selection of bandwidth should consider the following factors:

[0066] a) Determine the bandwidth of ESO

[0067] The bandwidth of the ESO determines the observer's response speed to disturbances and unmodeled dynamics and should be set according to the dynamic characteristics and response requirements of the system. In general, the bandwidth of the ESO ( ) should be set to 1.5 to 3 times the control bandwidth to ensure that the observer can track system disturbances quickly and accurately.

[0068] b) Calculate the gain of ESO

[0069] For a second-order linear ESO, its gain parameters are usually determined by pole placement or frequency domain design. The following takes pole placement as an example: select the pole position of the ESO so that its response speed meets the bandwidth requirements. For a second-order system, the damping ratio ( ) and the natural frequency ( ) to configure the gain.

[0070] c) Adjust ESO gain parameters

[0071] In the simulation environment, by adjusting Parameters, observe the estimation accuracy and response speed of ESO to disturbances, the goal is to ensure that the observer can quickly and accurately estimate the disturbance term after the disturbance occurs , while maintaining robustness to system noise.

[0072] 3. Control law design and implementation

[0073] Based on the ESO's estimation of disturbance, a simplified LADRC control law is used to perform feedback control on the speed deviation.

[0074] (1) Error definition and control objectives

[0075] Set the target speed to The actual speed is , then the speed error is The control goal is to make the aircraft speed Able to quickly approach and maintain Nearby, thus achieving precise descent control.

[0076] (2) Control law expression

[0077] Based on the estimation results of ESO, the control quantity can be designed as:

[0078] ,

[0079] in, is the closed-loop bandwidth of the speed controller. The real-time estimate of the error feedback term is used to offset the unknown disturbance. Act directly on the system to achieve fast and stable control of speed.

[0080] During the implementation process, ground semi-physical simulation and wind tunnel tests can be used to and Calibration is performed so that the control system can maintain the desired speed control accuracy and response characteristics under typical disturbance conditions (such as a certain range of wind speed changes and aerodynamic parameter deviations). The specific steps include:

[0081] (1) Before the aircraft takes off, the above controller parameters are written into the onboard flight control computer. When the aircraft completes its mission and enters the unpowered return phase, the flight control computer will adjust the speed. Perform online measurements.

[0082] (2) The flight control computer calculates the speed error based on the current measured speed , and use ESO to estimate the disturbance term online to obtain ;

[0083] (3) Calculate the spoiler deflection according to the control law The servo actuator drives the spoiler to achieve a corresponding slight deflection, thereby introducing the necessary additional resistance in the aerodynamics to make the speed reach the target value. convergence;

[0084] (4) During the entire descent and return process, the ESO continues to work online. When external wind fields, air turbulence and other disturbances change, the ESO can be updated in a relatively short time. , so that the controller can adapt to new environmental conditions in real time and maintain stable speed control performance.

[0085] Test verification and results

[0086] During the experimental stage, the control strategy of this embodiment can be tested in a simulation environment (such as a semi-physical simulation platform), and the aircraft model, spoiler aerodynamic characteristic parameters, and typical wind field disturbances are input into the simulation system. The experimental results are as follows: Figure 3 As shown, it can be seen that after entering the unpowered return, the speed control mode changes from throttle control to spoiler control, and the deceleration control of 30m / s is achieved through spoiler control in about 15s, and the speed tracking of the error is achieved in about 30s. The spoiler deflection is pre-biased by about 2° before switching the control mode, and finally stabilizes at about 6° after switching, and the command output is smooth. When the input wind field disturbance, quality parameter deviation or aerodynamic characteristics change, the control system can estimate the disturbance and compensate it through ESO in a short time, so that the speed error is quickly reduced; compared with the traditional PID or control method based on the precise model, the method of this embodiment can still maintain good speed tracking performance and higher robustness under large parameter uncertainty, and can achieve stable and rapid speed adjustment in a wide range of working conditions and environmental changes, providing strong support for safe and accurate landing in the unpowered return section.

[0087] The above are only preferred embodiments of the present invention. Ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the protection scope of the present invention.

Claims

1. A method for controlling the speed of an aircraft spoiler during an unpowered return phase based on active disturbance rejection control, characterized in that: The following steps are involved: S1: Online measurement of the aircraft's flight speed and establishment of the aircraft's dynamic model in the longitudinal direction; S2: Calculate the speed error based on the current measured speed and use ESO to estimate the disturbance term online; S3: Based on the ESO’s estimation of the disturbance, the LADRC control law is used to perform feedback control on the speed deviation.

2. The method for controlling the speed of an aircraft spoiler during an unpowered return phase based on active disturbance rejection control according to claim 1, characterized in that: The dynamic model of the aircraft in the longitudinal direction is: ， In the formula, is the differential of velocity, is the coefficient of the controller, is the external disturbance, For control input.

3. The method for controlling the speed of an aircraft spoiler during an unpowered return phase based on active disturbance rejection control according to claim 1, characterized in that: The designed extended state observer is in the form of: ， in, Respectively Observation, is the system state variable, is the observer gain, For observation and output The error between .

4. The method for controlling the speed of an aircraft spoiler during an unpowered return phase based on active disturbance rejection control according to claim 3 is characterized in that: The ESO gain parameters are selected according to the response characteristics of the aircraft and the desired control bandwidth.

5. The method for controlling the speed of an aircraft spoiler during an unpowered return phase based on active disturbance rejection control according to claim 3 or 4, characterized in that: The ESO gain parameter setting process is as follows: The bandwidth of the ESO is set to 1.5 to 3 times the control bandwidth, depending on the dynamic characteristics and response requirements of the system; Calculate the gain of the ESO by pole placement or frequency domain design method; By adjusting the gain of the observer, the estimation accuracy and response speed of the ESO to the disturbance are observed to ensure that the observer can estimate the disturbance term quickly and accurately after the disturbance occurs.

6. The method for controlling the speed of an aircraft spoiler during an unpowered return phase based on active disturbance rejection control according to claim 1, characterized in that: The speed error is ,in is the target speed, is the actual measured speed.

7. The method for controlling the speed of an aircraft spoiler during an unpowered return phase based on active disturbance rejection control according to claim 1 or 3, characterized in that: The LADRC control law is: ， in, is the closed-loop bandwidth of the speed controller, e is the speed error, is the coefficient of the controller.

8. The method for controlling the speed of an aircraft spoiler during an unpowered return phase based on active disturbance rejection control according to claim 7, characterized in that: The deflection of the spoiler is calculated according to the LADRC control law, and the servo actuator drives the spoiler to achieve a corresponding small deflection, thereby introducing necessary additional resistance in the aerodynamics to make the speed converge to the target speed.

9. The method for controlling the speed of an aircraft spoiler during an unpowered return phase based on active disturbance rejection control according to claim 8, characterized in that: The spoiler is installed on the upper surface of the wing.

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