An unmanned aerial vehicle trajectory fault-tolerant control method and system for actuator failure

Abstract

The application discloses a kind of unmanned plane trajectory fault-tolerant control methods and systems for actuator failure, belong to unmanned plane control technical field, including under the condition of nonlinear interference and model uncertainty, obtain unmanned plane nonlinear fault model;Actuator failure model is constructed under the condition of unmanned plane motor efficiency loss, and unmanned plane nonlinear fault model is simplified based on actuator failure model;Based on the simplified unmanned plane nonlinear fault model, construct nonlinear fault diagnosis observer to diagnose actuator failure;Based on nonlinear fault diagnosis observer, construct nonlinear adaptive fault estimator to estimate the parameters of actuator failure;Based on the diagnosed actuator failure and parameter, design fault-tolerant controller;Based on fault-tolerant controller, modify motor control command, control the flight trajectory of unmanned plane.The application reduces the risk that actuator failure leads to the flight performance of unmanned plane deteriorates or even crashes, improves the reliability and safety of unmanned plane.

Description

Technical Field

[0001] This invention belongs to the field of unmanned aerial vehicle (UAV) control technology, and relates to a UAV trajectory fault-tolerant control method and system for actuator failure. Background Technology

[0002] Unmanned aerial vehicles (UAVs) have garnered widespread attention due to their potential applications in various military and civilian fields. Quadcopter UAVs represent a special type of UAV equipped with four propellers, each mounted on the shaft of a brushless DC motor. The rotation of the rotors generates the thrust required to maintain the quadcopter's flight. Furthermore, the quadcopter's attitude is controlled by changing the rotor speed, which generates torque forces acting on the airframe. Researchers have proposed various methods to address the attitude stabilization or tracking problems of quadcopter UAVs, including backstepping techniques, disturbance rejection control strategies based on H∞ theory, and adaptive control. However, these control schemes are all designed based on the assumption that the quadcopter system is fault-free. Due to degradation or damage to components such as motors and propellers, the drive motor-propeller system is prone to failure. Such actuator failures can adversely affect position and attitude tracking performance. How to avoid actuator failures from compromising the safety of UAVs is currently a key research focus. Summary of the Invention

[0003] The purpose of this invention is to solve the problems in the prior art and provide a fault-tolerant control method and system for UAV trajectory in response to actuator failure. This method can reduce the risk of serious deterioration of UAV flight performance or even serious accidents such as crashes caused by actuator failure, and improve the reliability, safety and survivability of quadcopter UAVs.

[0004] To achieve the above objectives, the present invention employs the following technical solution:

[0005] In a first aspect, the present invention provides a fault-tolerant trajectory control method for unmanned aerial vehicles (UAVs) oriented towards actuator failure, comprising the following steps:

[0006] Based on the kinematic equations, a nonlinear fault model for UAVs under nonlinear disturbances and model uncertainties is constructed.

[0007] An actuator failure model is constructed under the condition of motor efficiency loss in UAVs, and a nonlinear failure model of UAVs is simplified based on the actuator failure model;

[0008] Based on a simplified UAV nonlinear fault model, a nonlinear fault diagnosis observer is constructed to diagnose actuator faults.

[0009] Based on a nonlinear fault diagnosis observer, a nonlinear adaptive fault estimator is constructed to predict actuator fault parameters.

[0010] Based on the diagnosed actuator faults and the estimated actuator fault parameters, a fault-tolerant controller is designed.

[0011] The drone's flight trajectory is controlled by modifying the motor control commands based on a fault-tolerant controller.

[0012] Secondly, the present invention provides a fault-tolerant unmanned aerial vehicle (UAV) trajectory control system for actuator failures, comprising:

[0013] The acquisition module, based on kinematic equations, acquires a nonlinear fault model of the UAV under conditions of nonlinear disturbance and model uncertainty.

[0014] The fault model simplification module is used to construct an actuator fault model under the condition of UAV motor efficiency loss, and to simplify the UAV nonlinear fault model based on the actuator fault model.

[0015] The first construction module is based on a simplified UAV nonlinear fault model to construct a nonlinear fault diagnosis observer to diagnose actuator faults.

[0016] The second building module, based on the nonlinear fault diagnosis observer, constructs a nonlinear adaptive fault estimator to predict the parameters of actuator faults;

[0017] A fault-tolerant controller design module, which designs a fault-tolerant controller based on the diagnosed actuator fault and the parameters of the actuator fault;

[0018] The control module modifies the motor control commands based on the fault-tolerant controller to control the flight trajectory of the UAV.

[0019] Thirdly, the present invention provides a terminal device including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the method described above.

[0020] Fourthly, the present invention provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the method described above.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] This invention utilizes a fault diagnosis observer and estimator to diagnose and estimate faults. Based on the fault diagnosis and estimation, a fault-tolerant controller is used to achieve stable control of the trajectory and attitude. The UAV can stably and accurately track the desired position trajectory and desired attitude trajectory, reducing the risk of serious deterioration of the UAV's flight performance or even serious accidents such as crashes caused by actuator failures, and improving the reliability, safety and survivability of quadcopter UAVs. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a flowchart of the UAV trajectory fault-tolerant control method for actuator failure according to the present invention;

[0025] Figure 2 This is a schematic diagram of the cross-type quadcopter UAV of the present invention;

[0026] Figure 3 This is a block diagram of the UAV trajectory fault-tolerant control system for actuator failures according to the present invention.

[0027] Figure 4 This is a diagram illustrating the position tracking effect of the UAV trajectory fault-tolerant control system of the present invention.

[0028] Figure 5 This is a diagram illustrating the altitude effect of the UAV trajectory fault-tolerant control system of the present invention.

[0029] Figure 6 This is a diagram illustrating the yaw angle effect of the UAV trajectory fault-tolerant control system of the present invention.

[0030] Figure 7 This is a diagram illustrating the roll angle effect of the unmanned aerial vehicle trajectory fault-tolerant control system of the present invention.

[0031] Figure 8 This is a diagram illustrating the pitch angle effect of the UAV trajectory fault-tolerant control system of the present invention.

[0032] Figure 9 This is a structural diagram of the UAV trajectory fault-tolerant control system for actuator failures according to the present invention. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0034] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0035] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0036] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Furthermore, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0037] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0038] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0039] The present invention will now be described in further detail with reference to the accompanying drawings:

[0040] See Figure 1 This invention discloses a fault-tolerant control method for UAV trajectory in response to actuator failures, comprising:

[0041] S101, based on kinematic equations, constructs a nonlinear fault model for UAVs under nonlinear disturbances and model uncertainties.

[0042] Considering the known disturbances and model uncertainties, the UAV model is constructed according to Newton's second law and Euler's dynamic equations as shown in formula (1):

[0043]

[0044] Where, p E v E η = [φ, θ, ψ] and ω = [p, q, r] are the inertial position, inertial velocity, Euler angle, and angular rate, respectively; U and T φ T θ T ψ These are thrust, roll torque, pitch torque, and yaw torque, respectively; R EB (η) is the rotation matrix of η; m is the weight of the UAV, c d v is the tensile coefficient. B J is the velocity of the drone relative to the body, g is the acceleration due to gravity; x J y J z Let ζ be the inertia of the UAV in the X, Y, and Z directions; v , ζ ω To model uncertainty; R η (φ,θ) is the rotation matrix of φ,θ, and ζ v0 For an unknown nonlinear term, ζ ω0 This is to add an unknown nonlinear term.

[0045] S102, construct an actuator failure model under the condition of UAV motor efficiency loss, and simplify the UAV nonlinear failure model based on the actuator failure model.

[0046] See Figure 2 This diagram shows a simplified model of a quadcopter, along with the assumed fuselage and inertial frame. According to UAV dynamics principles, motors M1 and M3 rotate counter-clockwise, while motors M2 and M4 rotate clockwise. Each motor is equidistant from the UAV's center of mass and generates a force along the z-direction relative to the fuselage frame. The rotation of each rotor produces a counter-torque acting on the UAV.

[0047] The thrust and torque generated by the rotor are proportional to the square velocity of the rotor, as shown in formulas (2) and (3):

[0048]

[0049]

[0050] Among them, F n For the total force on the drone, b F And k are constant coefficients for the motor thrust and torque, T n The relative torque of the drone is Ω, sgn(.) represents the sign function. n Given the angular velocity of the motor, n = 1, 2, 3, 4 represent four motors;

[0051] The total thrust and torque of the drone are expressed as follows:

[0052]

[0053] in, M represents the given motor speed, and M is the mapping matrix between thrust and torque and rotor angular velocity;

[0054] The actuator fault model under partial efficiency loss of the motor is constructed as shown in Equation (4):

[0055]

[0056] Among them, Ω n Represents the given angular velocity of the motor. Represents the actual angular velocity of the motor; The unknown parameter represents the partial failure of motor n; κ n =1 indicates that the motor is fault-free, κ n <1 indicates that the motor has experienced some efficiency loss. It is a lower bound scalar;

[0057] Based on the actuator fault model, the relationship between motor thrust and torque is constructed. Substituting this into the UAV nonlinear fault model simplifies the UAV nonlinear fault model, as shown in formula (5):

[0058]

[0059] Where I4 is a four-dimensional unit vector, β is the fault function, and t is the time variable. n v represents the time when the failure occurred. n For execution state Λ n Assign a fault matrix to the actuator. If motor 1 fails, then Λ1 = diag{1,0,0,0}; when t < t n When, β(tt) n ) = 0, when t > t n When, β(tt) n ) = 1.

[0060] S103, based on a simplified UAV nonlinear fault model, constructs a nonlinear fault diagnosis observer to diagnose actuator faults.

[0061] Substituting the thrust-torque relationship into the simplified UAV model, as shown in equation (6):

[0062]

[0063] in, Let ζ(x,t) be the differential of the velocity in the vertical direction, and let ζ(x,t) be a nonlinear term. For the known nonlinear terms, construct a nonlinear fault diagnosis observer as shown in formula (7):

[0064]

[0065] Among them, v z Representing the inertial velocity of the UAV along the z-axis, the fault diagnosis observer system status includes: the estimated inertial velocity and the UAV's angular rate. These are design parameters.

[0066] S104, based on a nonlinear fault diagnosis observer, constructs a nonlinear adaptive fault estimator to predict the parameters of actuator faults.

[0067] When an actuator fault is diagnosed, four adaptive fault isolation estimators are activated to determine the faulty motor. The nonlinear adaptive fault estimator is shown in Equation (8):

[0068]

[0069] in, Γ is the state estimator. n It is a positive definite design matrix, and This represents the state estimate, where ξ is the state variable and f() is the nonlinear quantity. h is the square of the rotor speed of the airborne controller. n Given the known executor function structure, x is a function variable. For fault parameter estimation.

[0070] Unknown fault parameter v n The adaptability rate is:

[0071]

[0072] Among them, Ψ n >0 is a constant, representing the adaptive rate; P Θ This is the projection operator.

[0073] S105, based on the diagnosed actuator faults and the parameters of the actuator faults, design a fault-tolerant controller.

[0074] To mitigate the impact of actuator failures, a fault-tolerant controller is designed by combining various observations obtained from a fault diagnosis observer and a fault isolation estimator.

[0075]

[0076] in, It is the square of the rotor speed of the airborne controller; For fault parameter estimation; Λ n Assign a fault matrix to the actuator; This is the squared value of the rotor speed for fault tolerance.

[0077] S106 modifies motor control commands based on a fault-tolerant controller to control the flight trajectory of the drone.

[0078] See Figure 3 A dual-loop control structure is designed based on the fault-tolerant controller, including a position control loop and an attitude control loop. The position control loop uses a position fault-tolerant controller, and the attitude control loop uses an attitude fault-tolerant controller. The roll angle and pitch angle required for control are generated by the following PID control law, as shown in formula (10):

[0079]

[0080] Where R(ψ) is the transformation matrix defined to compensate for the rotation direction of the quadrotor, and e(t) is the position error, K P ,K I ,K D These are the proportional, integral, and derivative gain values; the fault-tolerant controller outputs the UAV's position tracking trajectory, altitude, and attitude angle tracking trajectory.

[0081] Reference Figure 4 , Figure 5 , Figure 6 , Figure 7 and Figure 8 The invention was tested on an actual UAV. The results show that the UAV trajectory fault-tolerant control system and method proposed in this invention for actuator failure can stably control the position and attitude of the UAV when a failure occurs.

[0082] See Figure 9 This invention discloses a fault-tolerant unmanned aerial vehicle (UAV) trajectory control system for actuator failures, comprising:

[0083] The acquisition module, based on kinematic equations, acquires a nonlinear fault model of the UAV under conditions of nonlinear disturbance and model uncertainty.

[0084] The fault model simplification module is used to construct an actuator fault model under the condition of UAV motor efficiency loss, and to simplify the UAV nonlinear fault model based on the actuator fault model.

[0085] The first construction module is based on a simplified UAV nonlinear fault model to construct a nonlinear fault diagnosis observer to diagnose actuator faults.

[0086] The second building module, based on the nonlinear fault diagnosis observer, constructs a nonlinear adaptive fault estimator to predict the parameters of actuator faults;

[0087] A fault-tolerant controller design module, which designs a fault-tolerant controller based on the diagnosed actuator fault and the parameters of the actuator fault;

[0088] The control module modifies the motor control commands based on the fault-tolerant controller to control the flight trajectory of the UAV.

[0089] An embodiment of the present invention provides a terminal device. This terminal device includes a processor, a memory, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps in the various method embodiments described above. Alternatively, when the processor executes the computer program, it implements the functions of each module / unit in the various device embodiments described above.

[0090] The computer program can be divided into one or more modules / units, which are stored in the memory and executed by the processor to complete the present invention.

[0091] The terminal device may be a desktop computer, laptop, handheld computer, or cloud server, etc. The terminal device may include, but is not limited to, a processor and a memory.

[0092] The processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc.

[0093] The memory can be used to store the computer program and / or module. The processor implements various functions of the terminal device by running or executing the computer program and / or module stored in the memory and calling the data stored in the memory.

[0094] If the modules / units integrated into the terminal device are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc. It should be noted that the content included in the computer-readable medium can be appropriately added or removed according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer-readable media do not include electrical carrier signals and telecommunication signals.

[0095] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A fault-tolerant trajectory control method for unmanned aerial vehicles (UAVs) oriented towards actuator failure, characterized in that, Includes the following steps: Based on the kinematic equations, a nonlinear fault model for UAVs under nonlinear disturbances and model uncertainties is constructed; the details are as follows: Constructing a nonlinear fault model for unmanned aerial vehicles: in, , , and These are inertial position, inertial velocity, Euler angles, and angular rate, respectively. , , , These are thrust, roll torque, pitch torque, and yaw torque, respectively. for The rotation matrix; For the weight of the drone, The tensile coefficient, The speed of the drone relative to the body. It is the acceleration due to gravity; Let X be the inertia of the UAV in the X, Y, and Z directions. To model uncertainty; for The rotation matrix, For unknown nonlinear terms, To add unknown nonlinear terms An actuator failure model is constructed under the condition of motor efficiency loss in UAVs, and a nonlinear failure model of UAVs is simplified based on the actuator failure model; Based on a simplified UAV nonlinear fault model, a nonlinear fault diagnosis observer is constructed to diagnose actuator faults. Based on a nonlinear fault diagnosis observer, a nonlinear adaptive fault estimator is constructed to predict actuator fault parameters. Based on the diagnosed actuator faults and the estimated actuator fault parameters, a fault-tolerant controller is designed. The drone's flight trajectory is controlled by modifying the motor control commands based on a fault-tolerant controller.

2. The UAV trajectory fault-tolerant control method for actuator failure as described in claim 1, characterized in that, The actuator failure model constructed under the condition of UAV motor efficiency loss, and the UAV nonlinear failure model simplified based on the actuator failure model, includes: The thrust and torque generated by the drone motor rotor are related to the square velocity of the rotor as follows: in, For the total force on the drone, and For constant coefficients of motor thrust and torque, Let sgn(.) represent the relative torque of the drone. Given the angular velocity of the motor, n =1, 2, 3, 4 represent four motors; The total thrust and torque of the drone are as follows: in, Represents the given motor speed. M This is the mapping matrix between thrust and torque and rotor angular velocity; Construct an actuator failure model under partial efficiency loss of the motor: in, This refers to the actual angular velocity of the motor. express n Unknown parameters of motor No. 1 that experienced partial failure, including , This indicates that the motor is fault-free. This indicates that the motor has experienced some efficiency loss. It is a lower bound scalar, and ; Based on the actuator failure model, a relationship between motor thrust and torque is constructed. This relationship is then substituted into the UAV nonlinear failure model to simplify the UAV nonlinear failure model. in, It is a four-dimensional unit vector. For fault functions, For time variables, The time when the failure occurred. Execution status Assign a fault matrix to the actuators; if motor number 1 fails, then... ;when hour, =0, when hour, =1.

3. The UAV trajectory fault-tolerant control method for actuator failure as described in claim 2, characterized in that, The simplified UAV nonlinear fault model is used to construct a nonlinear fault diagnosis observer to diagnose actuator faults, specifically as follows: Substituting the thrust-torque relationship into the simplified UAV model: in, The derivative of the velocity in the vertical direction is... It is a nonlinear term. , For the known nonlinear terms, construct a nonlinear fault diagnosis observer as shown in formula (7): in, Representing the inertial velocity of the UAV along the z-axis, the fault diagnosis observer system status includes: the estimated inertial velocity and the UAV's angular rate. These are design parameters.

4. The UAV trajectory fault-tolerant control method for actuator failure as described in claim 1, characterized in that, The nonlinear adaptive fault estimator, based on the nonlinear fault diagnosis observer, is used to predict actuator fault parameters. Specifically: When an actuator fault is diagnosed, four adaptive fault isolation estimators are activated to determine the faulty motor. The nonlinear adaptive fault estimator is shown in Equation (8): in, For state estimators, It is a positive definite design matrix, and , j =1,…,4; Represents state estimation, For state variables, It is a nonlinear quantity. The square of the rotor speed of the airborne controller. Given the known executor function structure, For function variables, For fault parameter estimation; Unknown fault parameters The adaptability rate is: in, It is a constant representing the adaptive rate; This is the projection operator.

5. The UAV trajectory fault-tolerant control method for actuator failure as described in claim 3 or 4, characterized in that, The modification of motor control commands based on the fault-tolerant controller to control the flight trajectory of the UAV specifically involves: The fault-tolerant controller modifies the motor control command and sends it to the motor, as shown in formula (9): in, It is the square of the rotor speed of the airborne controller; For fault parameter estimation; Assign a fault matrix to the actuator; This is the squared value of the rotor speed for fault tolerance. The roll angle Φ required for the fault-tolerant controller d and pitch angle Θ d It is generated by the PID control law, as shown in formula (10): in, To compensate for the transformation matrix defined by the rotation direction of the quadcopter, and , For positional error, These are the proportional, integral, and derivative gain values; the fault-tolerant controller outputs the UAV's position tracking trajectory, altitude, and attitude angle tracking trajectory.

6. A fault-tolerant unmanned aerial vehicle trajectory control system for implementing the method of any one of claims 1-5, characterized in that, include: The acquisition module, based on kinematic equations, acquires a nonlinear fault model of the UAV under conditions of nonlinear disturbance and model uncertainty. The fault model simplification module is used to construct an actuator fault model under the condition of UAV motor efficiency loss, and to simplify the UAV nonlinear fault model based on the actuator fault model. The first construction module is based on a simplified UAV nonlinear fault model to construct a nonlinear fault diagnosis observer to diagnose actuator faults. The second building module, based on the nonlinear fault diagnosis observer, constructs a nonlinear adaptive fault estimator to predict the parameters of actuator faults; A fault-tolerant controller design module, which designs a fault-tolerant controller based on the diagnosed actuator fault and the parameters of the actuator fault; The control module modifies the motor control commands based on the fault-tolerant controller to control the flight trajectory of the UAV.

7. A terminal device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method as described in any one of claims 1-5.

8. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by a processor, it implements the steps of the method as described in any one of claims 1-5.

Images