Tilt-rotor unmanned aerial vehicle passive fault-tolerant control method and system based on nonlinear variable parameter model

Abstract

The invention relates to a passive fault-tolerant control method and system for a tilt-rotor unmanned aerial vehicle based on a nonlinear variable parameter model. The method comprises the following steps: S1, establishing an actuator fault model; s2, constructing a longitudinal dynamic model of the tilt-rotor aircraft, and converting the longitudinal dynamic model of the tilt-rotor aircraft into a nonlinear variable parameter model of the tilt-rotor aircraft; s3, introducing an actuator fault model into the nonlinear variable parameter model to obtain a nonlinear variable parameter model containing an actuator fault; s4, designing a fault-tolerant controller by adopting a quadratic sum convex programming method; s5, based on the Lyapunov stability theory, establishing a fault-tolerant controller solvability condition of the nonlinear variable parameter system model containing the actuator fault, enabling the nonlinear variable parameter model to have exponential stability, and solving the solvability condition to obtain the fault-tolerant controller; and S6, applying the fault-tolerant controller to a flight control system of the tilt-rotor aircraft.

Description

Technical Field

[0001] The present invention relates to the field of tilt-rotor UAV control, and in particular to a passive fault-tolerant control method and system for a tilt-rotor UAV based on a nonlinear parameter-varying (NPV) model. Background Art

[0002] With the widespread application and expansion of drones in various application scenarios such as reconnaissance, logistics and transportation, geographic surveying and mapping, and emergency rescue, people have higher and higher requirements for drone flight performance. The control design of helicopters and fixed-wing aircraft has been relatively mature in technology, and tilt-rotor aircraft have gradually become well-known. While having the performance advantages of fixed-wing drones and multi-rotor aircraft, tilt-rotor drones have also inherited the technical difficulties of these two types of aircraft, and derived unique technical problems of tilt-rotor drones.

[0003] The control system of a tilt-rotor aircraft is essentially time-varying and nonlinear. At present, for time-varying and nonlinear controlled objects in aerospace and other fields, the small disturbance linearization method of the trim state is often used in engineering practice. The disadvantage of this type of method is that it is relatively conservative in theory and difficult to meet its control design requirements. In recent years, with the vigorous development of the sum-of-squares (SOS) theory of polynomials, it has provided a powerful tool for the analysis of nonlinear time-varying systems. Based on the SOS convex programming theory, the computational difficulties caused by nonlinear and time-varying factors can be effectively handled. There are often multiple interferences in the transition phase of a tilt-rotor aircraft. A single interference suppression method cannot simultaneously handle problems such as high conservatism, high-precision control, and strict requirements on the controlled object and interference model. Fault-tolerant control theory aims to ensure that the reliability and stability of the system can be maintained in the event of a system failure. In practical applications, passive fault-tolerant control (PFTC) has been widely used in many fields due to its advantage of being able to quickly adjust the faulty system to maintain overall stability. However, the prior art has not yet realized passive fault-tolerant control of tilt-rotor aircraft based on a nonlinear variable parameter framework.

[0004] In view of the above problems existing in the prior art, the purpose of the present invention is to design a passive fault-tolerant control method and system for a tilt-rotor UAV based on a nonlinear variable parameter model. Summary of the invention

[0005] In view of the problems existing in the above-mentioned prior art, the present invention provides a passive fault-tolerant control method and system for a tilt-rotor UAV based on a nonlinear variable parameter model, which can effectively solve at least one problem existing in the above-mentioned prior art.

[0006] The technical solution of the present invention is: A passive fault-tolerant control method for a tilt-rotor UAV based on a nonlinear variable parameter model comprises the following steps: S1, establish actuator fault model; S2, constructing a longitudinal dynamics model of the tilt-rotor aircraft, and converting the longitudinal dynamics model of the tilt-rotor aircraft into a nonlinear variable parameter model of the tilt-rotor aircraft; S3, introducing an actuator fault model into the nonlinear variable parameter model to obtain a nonlinear variable parameter model containing an actuator fault; S4, using the square sum convex programming method to design a fault-tolerant controller; S5, based on Lyapunov stability theory, establishing a solvability condition of a fault-tolerant controller of a nonlinear variable parameter system model with actuator faults, so that the nonlinear variable parameter model has exponential stability, and solving the solvability condition to obtain the fault-tolerant controller; S6, applying the fault-tolerant controller to a flight control system of a tilt-rotor aircraft.

[0007] Furthermore, the actuator fault model is expressed by the following formula: ,in is the actuator fault model, is the failure factor, is the control input, For time.

[0008] Furthermore, after step S1, the following is performed: Introducing the intermediate matrix into the actuator fault model , , , convert the actuator fault model into a polynomial form; The intermediate matrix is ​​represented as follows: ; ; ; in, , , , represents the intermediate matrix, Expressed as the upper limit of the failure factor; It is expressed as the lower limit of the fault factor, m and L represent known constants respectively; The polynomial form is: , in, is the polynomial form of the actuator fault model, For the The signal of a failure in an actuator failure mode, is the command control torque vector, is the intermediate matrix, , Represent the known matrices, , .

[0009] Furthermore, the longitudinal dynamic model of the tilt-rotor aircraft is expressed by the following formula: ; in , , , and They are the speed, angle of attack, pitch angle, pitch rate and altitude of the tilt-rotor aircraft. is the tilt angle, is the velocity component in the z direction, It is the state of a tilt-rotor aircraft. , and Rotorcraft Component of force along the axis Components of axial force, pitching moment, is the mass of the tiltrotor aircraft, is the moment of inertia about the pitch axis, is the longitudinal control surface; The nonlinear variable parameter model of the tiltrotor aircraft is expressed by the following formula: , in, Indicates about The polynomial matrix of , Indicates about The polynomial matrix of , , , , , , , , , ; in is the system status, and are the errors in speed, angle of attack, pitch angle, pitch rate and altitude, is the control input, , and Along the main Axis and The components of the axis force error and pitch moment error, , , , , is the desired reference trajectory, , and is the reference control input; After introducing the actuator fault model into the nonlinear variable parameter model, we get: .

[0010] Furthermore, S4 adopts the square sum convex programming method to design a fault-tolerant controller including: Define that there is a The polynomial matrix and The symmetric polynomial matrix and matrix , and constant ,in , so that: , , , , in and is a suitable-dimensional vector, is a set of SOS polynomials, is a known vector, , is a known matrix, i , S, S1 represent known polynomials respectively; The exponentially stable fault-tolerant controller is obtained as: .

[0011] Furthermore, based on Lyapunov stability theory, a solvability condition of a fault-tolerant controller of a nonlinear variable parameter system model with actuator faults is established so that the nonlinear variable parameter model has exponential stability. Solving the solvability condition to obtain the fault-tolerant controller includes: S5.1, design the Lyapunov functional as , the Lyapunov functional is defined as is positive definite and bounded, and when hour, ; S5.2, calculate the time derivative of the Lyapunov functional, and the obtained time derivative of the Lyapunov functional is: ; in, is the intermediate matrix, Known constants, is the time-varying parameter vector; S5.3, converting non-convex terms in the time derivative into convex terms; S5.4, according to the SOS convex programming theory, the following SOS convex programming satisfies the conditions: , in, They represent known constants respectively; The nonlinear variable parameter model with actuator fault corresponding to the fault-tolerant controller is globally consistent exponentially stable at the origin and satisfies the conditions of square sum convex programming as the solvability conditions of the fault-tolerant controller of the nonlinear variable parameter model with actuator fault.

[0012] Further, converting the non-convex term in the time derivative into a convex term comprises: S5.3.1, Extracting Non-convex Terms in the Time Derivative ; S5.3.2, set at least one row of the matrix is equal to zero, there exists a Symmetric Polynomial Matrix ,one Polynomial Matrix , and the constant , and ,in , so that:

[0013]

[0014]

[0015]

[0016] in,

[0017] in is a column vector of appropriate dimension, , Respectively represent known matrices, and J represents a known constant; get ; S5.3.3, define the following form of Lyapunov candidate universal function: , The Lyapunov candidate functional satisfies: is positive definite and bounded, and when hour, ; S5.3.4, Introduction ,right The time derivative of the Lyapunov candidate functional is obtained by differentiation: ; in, Represents a known polynomial matrix, represents the time-varying parameter vector; S5.3.5, Extracting Nonconvex Terms from the Time Derivatives of Candidate Lyapunov Functionals ,right Perform mathematical transformation and get: ; in, represents a known constant; According to the conditions of S5.4.2, we get: ; By using the Schur complement theorem of the matrix, we get: ,Sure is non-negative; S5.3.6, if ,but , definition ,get , and then perform mathematical transformation to obtain , and ; like , by Held inequality and Available ,in and Calculated by SOS, assuming ,get .

[0018] A passive fault-tolerant control system for a tilt-rotor UAV based on a nonlinear variable parameter model is further provided, which implements the passive fault-tolerant control method for a tilt-rotor UAV based on a nonlinear variable parameter model during operation.

[0019] Therefore, the present invention provides the following effects and / or advantages: The present application discloses a passive fault-tolerant control method for a tiltrotor aircraft based on a nonlinear variable parameter model. A nonlinear variable parameter model of a tiltrotor aircraft containing multi-source interference is constructed according to a defined explicit time-varying nonlinear variable parameter system. For the nonlinear variable parameter system containing time-varying faults, an exponentially stable fault-tolerant controller is designed to suppress interference in the nonlinear model, thereby forming a passive fault-tolerant control structure with strong robust performance. For the fault-tolerant controller, the Lyapunov stability condition and the SOS method are applied to obtain a solved fault-tolerant controller to control the flight of a tiltrotor UAV, thereby finally forming a passive fault-tolerant control method for a tiltrotor aircraft.

[0020] The present invention overcomes the shortcomings of the traditional nonlinear robust control method and improves the robust performance of the system.

[0021] The method provided by the present invention is used to control the flight of a tilt-rotor UAV, and can track the target trajectory more quickly and accurately from the aspects of pitch angle rate, pitch angle and speed, and the method provided by this embodiment described from the components of the force in the x-direction, the components of the force in the y-direction and the pitch moment can track the target more quickly and accurately.

[0022] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention are realized and obtained by the structures particularly pointed out in the description and the drawings.

[0023] It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The present invention is a schematic diagram of a framework of a passive fault-tolerant control method for a tilt-rotor UAV based on a nonlinear variable parameter model.

[0025] Figure 2 A schematic diagram of coordinate reference established for the tilt-rotor aircraft model of the present invention.

[0026] Figure 3 Angle of attack Tracking trajectory graph.

[0027] Figure 4 For height Tracking trajectory graph.

[0028] Figure 5 is the pitch angle rate Tracking trajectory graph.

[0029] Figure 6 is the pitch angle Tracking trajectory graph.

[0030] Figure 7 For speed Tracking trajectory graph.

[0031] Figure 8 is the force along the x-axis Tracking trajectory graph.

[0032] Fig. 9 is the force along the y-axis Track the trajectory curve.

[0033] Fig.10 for Tracking trajectory graph. DETAILED DESCRIPTION

[0034] In order to facilitate understanding by those skilled in the art, the present invention is now described in further detail by way of examples: refer to Figure 1 , A passive fault-tolerant control method for a tilt-rotor UAV based on a nonlinear variable parameter model comprises the following steps: S1, establish actuator fault model; S2, constructing a longitudinal dynamics model of the tilt-rotor aircraft, and converting the longitudinal dynamics model of the tilt-rotor aircraft into a nonlinear variable parameter model of the tilt-rotor aircraft; S3, introducing an actuator fault model into the nonlinear variable parameter model to obtain a nonlinear variable parameter model containing an actuator fault; In steps S1-S3, according to the defined nonlinear variable parameter system, the longitudinal dynamic model of the nonlinear variable parameter system of the tilt-rotor UAV is constructed and represented as a closed-loop system of the nonlinear variable parameter model; then, for the nonlinear variable parameter model of the tilt-rotor UAV, the actuator fault model is introduced to obtain the nonlinear variable parameter model containing the actuator fault.

[0035] S4, using the sum of squares (SOS) convex programming method to design a fault-tolerant controller; In this step, a fault-tolerant controller with exponential stability is designed for the nonlinear variable parameter model, and the fault-tolerant controller is applied to the nonlinear variable parameter model to suppress the interference in the nonlinear model.

[0036] S5, based on Lyapunov stability theory, establishing a solvability condition of a fault-tolerant controller of a nonlinear variable parameter system model with actuator faults, so that the nonlinear variable parameter model has exponential stability, and solving the solvability condition to obtain the fault-tolerant controller; In this step, the Lyapunov function itself has the characteristics that the speed V of the tiltrotor aircraft is greater than 0, and the derivative of V is less than 0. When the derivative of V obtained by the designed controller is negative, it means that the controller has the characteristic of exponential stability.

[0037] Then, the Lyapunov stability condition and SOS method are applied to solve the controller, and the obtained solution can be used to control the flight of the tiltrotor aircraft.

[0038] S6, applying the fault-tolerant controller to a flight control system of a tilt-rotor aircraft.

[0039] Further, The actuator fault model is expressed by the following formula: ,in is the actuator fault model, is the failure factor, is the control input, For time.

[0040] The failure factor of the actuator ,in and is a constant and .when ,Right now , at this time the actuator efficiency factor is a constant. , at this time, the actuator efficiency coefficient is a variable that changes with time.

[0041] Consider multiplicative actuator failures. Definition .

[0042] Further, After step S1, execute: Introduce the intermediate matrix into the actuator fault model , , , convert the actuator fault model into a polynomial form; The intermediate matrix is ​​represented as follows: ; ; ; in, , , , represents the intermediate matrix, Expressed as the upper limit of the failure factor; It is expressed as the lower limit of the fault factor, m and L represent known constants respectively; The polynomial form is: , in, is the polynomial form of the actuator fault model, For the The signal of a failure in an actuator failure mode, is the command control torque vector, is the intermediate matrix, , Represent the known matrices, , .

[0043] Further, The longitudinal dynamics model of the tilt-rotor aircraft is expressed by the following formula: ; in , , , and They are the speed, angle of attack, pitch angle, pitch rate and altitude of the tilt-rotor aircraft. is the tilt angle, is the velocity component in the z direction, It is the state of a tilt-rotor aircraft. , and Rotorcraft Component of force along the axis Components of axial force, pitching moment, is the mass of the tiltrotor aircraft, is the moment of inertia about the pitch axis, is the longitudinal control surface; The nonlinear variable parameter model of the tiltrotor aircraft is expressed by the following formula: , in, Indicates about The polynomial matrix of , Indicates about The polynomial matrix of , , , , , , , , , ; in is the system status, and are the errors in speed, angle of attack, pitch angle, pitch rate and altitude, is the control input, , and Along the main Axis and The components of the axis force error and pitch moment error, , , , , is the desired reference trajectory, , and is the reference control input; After introducing the actuator fault model into the nonlinear variable parameter model, we get: .

[0044] Furthermore, S4 adopts the square sum convex programming method to design a fault-tolerant controller including: Define that there is a The polynomial matrix and The symmetric polynomial matrix and matrix , and constant ,in , so that: , , , , in and is a suitable-dimensional vector, is a set of SOS polynomials, is a known vector, , is a known matrix, i , S, S1 represent known polynomials respectively; The exponentially stable fault-tolerant controller is obtained as: .

[0045] In this step, a fault-tolerant controller of the closed-loop system Global Uniform Exponential Stability (GUES) is calculated through a nonlinear variable parameter model, and a Lyapunov functional is designed for the fault-tolerant controller of the closed-loop system GUES, thereby designing a fault-tolerant controller.

[0046] Next comes the specific process of designing a fault-tolerant controller.

[0047] Further, Based on Lyapunov stability theory, a solvability condition of a fault-tolerant controller of a nonlinear variable parameter system model with actuator faults is established so that the nonlinear variable parameter model has exponential stability. Solving the solvability condition to obtain the fault-tolerant controller includes: S5.1, design the Lyapunov functional as , the Lyapunov functional is defined as is positive definite and bounded, and when hour, ; S5.2, calculate the time derivative of the Lyapunov functional, and the obtained time derivative of the Lyapunov functional is: ; in, is the intermediate matrix, Known constants, is the time-varying parameter vector; S5.3, converting non-convex terms in the time derivative into convex terms; S5.4, according to the SOS convex programming theory, the following SOS convex programming satisfies the conditions: , in, They represent known constants respectively; The nonlinear variable parameter model with actuator fault corresponding to the fault-tolerant controller is globally consistent exponentially stable at the origin and satisfies the conditions of square sum convex programming as the solvability conditions of the fault-tolerant controller of the nonlinear variable parameter model with actuator fault.

[0048] Since there is a time derivative of the Lyapunov functional This non-convex term makes it impossible for SOSTOOLS to search for controller parameters. Considering that in actual engineering applications, the system is usually under-actuated and fully-actuated, that is, in the fault system, by introducing Eliminate the influence of non-convex terms on controller selection.

[0049] Further, Converting the non-convex term in the time derivative into a convex term includes: S5.3.1, Extracting Non-convex Terms in the Time Derivative ; S5.3.2, set at least one row of the matrix is equal to zero, there exists a Symmetric Polynomial Matrix ,one Polynomial Matrix , and the constant , and ,in , so that:

[0050]

[0051]

[0052]

[0053] in,

[0054] in is a column vector of appropriate dimension, , Respectively represent known matrices, and J represents a known constant; get ; S5.3.3, define the following form of Lyapunov candidate universal function: , The Lyapunov candidate functional satisfies: is positive definite and bounded, and when hour, ; S5.3.4, Introduction ,right The time derivative of the Lyapunov candidate functional is obtained by differentiation: ; in, Represents a known polynomial matrix, represents the time-varying parameter vector; S5.3.5, Extracting Nonconvex Terms from the Time Derivatives of Candidate Lyapunov Functionals ,right Perform mathematical transformation and get: ; in, represents a known constant; According to the conditions of S5.4.2, we get: ; By using the Schur complement theorem of the matrix, we get: ,Sure is non-negative; S5.3.6, if ,but , definition ,get , and then perform mathematical transformation to obtain , and ; like , by Held inequality and Available ,in and Calculated by SOS, assuming ,get .

[0055] At this time, both are convex items.

[0056] Specifically, if there is no zero row in the B matrix, this requires the use of SDP to solve the problem. To further advance this work, the following definition is first given: (3-54).

[0057] Assume there is at least one row of the matrix is equal to zero.

[0058] For a faulty system, suppose there exists a The polynomial matrix and The symmetric polynomial matrix and matrix , and constant ,in , so that (3-56); (3-57); (3-58); (3-59); in, , in is a column vector of appropriate dimension. The controller that makes the closed-loop system achieve GUES is: (3-60); Proof: Define the following form of Lyapunov candidate function: (3-61); is positive definite and bounded, and when hour, .

[0059] Introduction .right Taking the derivative with respect to time t gives: (3-62); It can be seen that there is a non-convex term: (3-63); Multiply (3-60) by and right multiplication ,have: (3-64); Formula (3-58) means: (3-65); By using Schur's complement theorem of matrices, we have: (3-66); It can be seen that is non-negative. Therefore, it can be divided into two cases for discussion: 1) When ,mean , so (3-59) means: (3-67); Condition (3-54) means: (3-68); Multiply both sides of (3-68) by ,have: (3-69); because , and then we can get: (3-70); Multiply (3-67) by and right multiplication ,because , we can get: , and (3-71); Obviously, the controller (3-60) for the closed-loop system to achieve GUES can make the nonlinear variable parameter model achieve GUES at the origin.

[0060] 2) When , from Held inequality and equation (3-59) we can get: (3-72); in and It is calculated by the SOS in the corresponding theorem. It can be seen that if: (3-73); Then (3-69) means: (3-74); The same result can be obtained. (3-73) can be used as a criterion. and When (3-73) is satisfied, the fault-tolerant control objective is achieved. It can be seen that if is close to zero, (3-73) is obviously satisfied.

[0061] Therefore, it is concluded that the nonlinear variable parameter model generated under the fault-tolerant controller (3-60) is globally consistent exponentially stable at the origin.

[0062] A passive fault-tolerant control system for a tilt-rotor UAV based on a nonlinear variable parameter model is further provided, which implements the passive fault-tolerant control method for a tilt-rotor UAV based on a nonlinear variable parameter model during operation.

[0063] Experimental data Figure 3 Medium blue curve The dotted line represents the angle of attack trajectory of the tilt-rotor UAV of the present invention. represents the angle of attack trajectory of the normal NPV, represents the reference angle of attack trajectory.

[0064] Figure 4 Medium blue curve The dotted line represents the altitude trajectory of the tilt-rotor UAV of the present invention. represents the height trajectory of the normal NPV, Represents the reference altitude trajectory.

[0065] Figure 5 Medium blue curve The dotted line represents the pitch rate trajectory of the tilt-rotor UAV of the present invention. represents the pitch rate trajectory of a normal NPV, Represents the reference pitch rate trajectory.

[0066] Figure 6 Medium blue curve The dotted line represents the pitch angle trajectory of the tilt-rotor UAV of the present invention. represents the pitch angle trajectory of a normal NPV, Represents the reference pitch angle trajectory.

[0067] Figure 7 Medium blue curve The dotted line represents the velocity trajectory of the tilt-rotor UAV of the present invention. represents the velocity trajectory of the normal NPV, Represents the reference velocity trajectory.

[0068] Figure 8 Medium blue curve The dotted line represents the trajectory of the tilt-rotor UAV of the present invention. represents the trajectory obtained by ordinary NPV, represents the reference trajectory.

[0069] Fig. 9 Medium blue curve The dotted line represents the velocity trajectory of the tilt-rotor UAV of the present invention. represents the velocity trajectory obtained by ordinary NPV, Represents the reference velocity trajectory.

[0070] Fig.10 Medium blue curve The dotted line represents the trajectory of the tilt-rotor UAV of the present invention. represents the trajectory of the ordinary NPV, represents the reference trajectory.

[0071] Figure 4 It is illustrated that the method provided in this embodiment has a smaller altitude deviation and can achieve altitude stability 10 seconds in advance. Figure 5 , Figure 6 , Figure 7 The method provided in this embodiment, which is also explained from the pitch angle rate, pitch angle and speed, can track the target trajectory more quickly and accurately. Figure 8-10 The method provided in this embodiment, which is explained from the components of the force in the x direction, the components of the force in the y direction and the pitch moment, can track the target more quickly and accurately.

[0072] Figure 3-Figure 10, which illustrates that the method provided by this embodiment enables the tilt-rotor UAV to track the target trajectory more stably, and can keep up with the reference angle of attack trajectory, reference altitude trajectory, reference pitch rate trajectory, reference pitch angle trajectory, reference velocity trajectory, reference x-direction force component trajectory, reference y-direction force component trajectory, and reference pitch moment trajectory more quickly than the common NPV method. At the same time, the present invention overcomes the shortcomings of the traditional nonlinear robust control method and improves the robust performance of the system.

[0073] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0074] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0075] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0076] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0077] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms should not be understood as necessarily being directed to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

Claims

1. A passive fault-tolerant control method for a tilt-rotor UAV based on a nonlinear variable parameter model, characterized in that: The following steps are involved: S1, establish actuator fault model; S2, constructing a longitudinal dynamics model of the tilt-rotor aircraft, and converting the longitudinal dynamics model of the tilt-rotor aircraft into a nonlinear variable parameter model of the tilt-rotor aircraft; S3, introducing an actuator fault model into the nonlinear variable parameter model to obtain a nonlinear variable parameter model containing an actuator fault; S4, using the square sum convex programming method to design a fault-tolerant controller; S5, based on Lyapunov stability theory, establishing a solvability condition of a fault-tolerant controller of a nonlinear variable parameter system model with actuator faults, so that the nonlinear variable parameter model has exponential stability, and solving the solvability condition to obtain the fault-tolerant controller; S6, applying the fault-tolerant controller to a flight control system of a tilt-rotor aircraft.

2. The passive fault-tolerant control method for a tilt-rotor UAV based on a nonlinear variable parameter model according to claim 1, characterized in that: The actuator fault model is expressed by the following formula: ,in is the actuator fault model, is the failure factor, is the control input, For time.

3. The passive fault-tolerant control method for a tilt-rotor UAV based on a nonlinear variable parameter model according to claim 2, characterized in that: After step S1, execute: Introduce the intermediate matrix into the actuator fault model , , , convert the actuator fault model into a polynomial form; The intermediate matrix is ​​represented as follows: ； ； ； in, , , , represents the intermediate matrix, Expressed as the upper limit of the failure factor; It is expressed as the lower limit of the fault factor, m and L represent known constants respectively; The polynomial form is: , in, is the polynomial form of the actuator fault model, For the The signal of a failure in an actuator failure mode, is the command control torque vector, is the intermediate matrix, , Represent the known matrices, , .

4. The passive fault-tolerant control method for a tilt-rotor UAV based on a nonlinear variable parameter model according to claim 3, characterized in that: The longitudinal dynamics model of the tilt-rotor aircraft is expressed by the following formula: ； in , , , and They are the speed, angle of attack, pitch angle, pitch rate and altitude of the tilt-rotor aircraft. is the tilt angle, is the velocity component in the z direction, It is the state of a tilt-rotor aircraft. , and Rotorcraft Component of force along the axis Components of axial force, pitching moment, is the mass of the tiltrotor aircraft, is the moment of inertia about the pitch axis, is the longitudinal control surface; The nonlinear variable parameter model of the tiltrotor aircraft is expressed by the following formula: ， in, Indicates about The polynomial matrix of , Indicates about The polynomial matrix of , ， ， ， ， ， ， ， ， ； in is the system status, and are the errors in speed, angle of attack, pitch angle, pitch rate and altitude, is the control input, , and Along the main Axis and The components of the axis force error and pitch moment error, , , , , is the desired reference trajectory, , and is the reference control input; After introducing the actuator fault model into the nonlinear variable parameter model, we get: 。 5. The passive fault-tolerant control method for a tilt-rotor UAV based on a nonlinear variable parameter model according to claim 4, characterized in that: S4, using the square sum convex programming method, designs a fault-tolerant controller including: Define that there is a The polynomial matrix and The symmetric polynomial matrix and matrix , and constant ,in , so that: ， ， ， ， in and is a suitable-dimensional vector, is a set of SOS polynomials, is a known vector, , is a known matrix, i , S, S1 represent known polynomials respectively; The exponentially stable fault-tolerant controller is obtained as: 。 6. The passive fault-tolerant control method for a tilt-rotor UAV based on a nonlinear variable parameter model according to claim 5, characterized in that: Based on Lyapunov stability theory, a solvability condition of a fault-tolerant controller of a nonlinear variable parameter system model with actuator faults is established so that the nonlinear variable parameter model has exponential stability. Solving the solvability condition to obtain the fault-tolerant controller includes: S5.1, design the Lyapunov functional as , the Lyapunov functional is defined as is positive definite and bounded, and when hour, ; S5.2, calculate the time derivative of the Lyapunov functional, and the obtained time derivative of the Lyapunov functional is: ; in, is the intermediate matrix, Known constants, is the time-varying parameter vector; S5.3, converting non-convex terms in the time derivative into convex terms; S5.4, according to the SOS convex programming theory, the following SOS convex programming satisfies the conditions: ， in, They represent known constants respectively; The nonlinear variable parameter model with actuator fault corresponding to the fault-tolerant controller is globally consistent exponentially stable at the origin and satisfies the conditions of square sum convex programming as the solvability conditions of the fault-tolerant controller of the nonlinear variable parameter model with actuator fault.

7. The passive fault-tolerant control method for a tilt-rotor UAV based on a nonlinear variable parameter model according to claim 6, characterized in that: Converting the non-convex term in the time derivative into a convex term includes: S5.3.1, Extracting Non-convex Terms in the Time Derivative ; S5.3.2, set at least one row of the matrix is equal to zero, there exists a Symmetric Polynomial Matrix ,one Polynomial Matrix , and the constant , and ,in , so that: in, in is a column vector of appropriate dimension, , Respectively represent known matrices, and J represents a known constant; get ; S5.3.3, define the following form of Lyapunov candidate universal function: ， The Lyapunov candidate functional satisfies: is positive definite and bounded, and when hour, ; S5.3.4, Introduction ,right The time derivative of the Lyapunov candidate functional is obtained by differentiation: ； in, Represents a known polynomial matrix, represents the time-varying parameter vector; S5.3.5, Extracting Nonconvex Terms from the Time Derivatives of Candidate Lyapunov Functionals ,right Perform mathematical transformation and get: ； in, represents a known constant; According to the conditions of S5.4.2, we get: ； By using the Schur complement theorem of the matrix, we get: ,Sure is non-negative; S5.3.6, if ,but , definition ,get , and then perform mathematical transformation to obtain , and ; like , by Held inequality and Available ,in and Calculated by SOS, assuming ,get .

8. A passive fault-tolerant control system for a tilt-rotor UAV based on a nonlinear variable parameter model, characterized in that: When working, the passive fault-tolerant control method of a tilt-rotor UAV based on a nonlinear variable parameter model as described in any one of claims 1 to 7 is implemented.

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