A transient control method for compound-wing unmanned aerial vehicles based on fractional-order sliding mode

Abstract

This invention discloses a transient control method for compound-wing unmanned aerial vehicles (UAVs) based on fractional-order sliding mode control, specifically relating to the field of compound-wing UAV flight control. It employs the Newton-Euler equations to perform integrated modeling of the transient process of the compound-wing UAV, deriving a longitudinal nonlinear mathematical model. Based on the traditional exponential power reaching law, a novel fractional-order reaching law is designed by combining a double power reaching law and the concept of fractional-order calculus. A fractional-order sliding mode controller is constructed for pitch angle, airspeed, and quadrotor altitude. An airspeed weighted control allocation strategy is used to distribute the forces and torques between the quadrotor system and the fixed-wing system, thereby solving for the actuator output. This invention applies sliding mode variable structure control to the transient control of compound-wing UAVs. The proposed fractional-order sliding mode control method improves the dynamic quality of the system, reduces steady-state control errors, enhances the robustness of the compound-wing UAV flight control system, and achieves smooth control of the transient process.

Description

Technical Field

[0001] This invention relates to the field of flight control for compound-wing unmanned aerial vehicles (UAVs), and specifically to a transient control method for compound-wing UAVs based on fractional sliding mode. Background Technology

[0002] Vertical take-off and landing fixed-wing unmanned aerial vehicles (VTOL-FW UAVs) combine the advantages of fixed-wing UAVs and rotary-wing UAVs. They can take off and land vertically and hover, and have the speed, endurance and payload advantages of fixed-wing UAVs, while avoiding the shortcomings of the two types of UAVs to the greatest extent.

[0003] Among vertical takeoff and landing fixed-wing UAVs, the quadplane, despite its large dead weight, boasts advantages such as simple mechanical structure, good technical feasibility, low economic cost, high feasibility, high safety factor, and low requirements for external conditions during takeoff and recovery. It is currently the vertical takeoff and landing solution with the lowest engineering difficulty, the highest practicality and reliability, and has extremely broad application prospects and practical significance.

[0004] The transition process for compound-wing UAVs requires switching between rotor and fixed-wing structures, which is quite challenging and is crucial to the success or failure of compound-wing UAV flight missions.

[0005] Existing research solutions for the transient control problem of compound-wing unmanned aerial vehicles (UAVs) mainly fall into two categories: ① Linear control laws, including PID control, LQR control, and H∞ control; ② Nonlinear control laws, including inverse control, nonlinear dynamic inverse control, and active disturbance rejection control. Compared to linear control, nonlinear control, with its advantages of flexibility, adaptability, and improved system stability, is better suited to the complex transient control problem of compound-wing UAVs.

[0006] Sliding mode control (SMC) is a nonlinear control method with advantages such as fast response, low dependence on system model, and strong robustness, and is widely used in industrial systems. However, during the approach phase of sliding mode, chattering can easily occur, leading to system collapse.

[0007] To address the challenges of complex transition process control and model uncertainty in compound-wing unmanned aerial vehicles (UAVs), this invention provides a transition process control method for compound-wing UAVs based on fractional sliding mode. Summary of the Invention

[0008] To address this, the present invention provides a control method for the transient process of a compound-wing UAV based on fractional sliding mode. Compared with traditional PID control and traditional sliding mode control, the proposed control method reduces control tracking error, enhances control accuracy and disturbance rejection capability, improves the robustness of the compound-wing UAV flight control system, and achieves smooth control of the transient process, thereby solving the current problem of longitudinal control of the transient process of compound-wing UAVs.

[0009] To achieve the above objectives, the present invention provides the following technical solution: a sliding mode control scheme for the transition process of a compound-wing unmanned aerial vehicle (UAV), which requires control of the pitch angle, airspeed, and altitude of the UAV, specifically including the following steps:

[0010] S1: Based on the Newton-Euler equations, the rotor and fixed-wing dynamics of the transition process of the compound-wing UAV are modeled in an integrated manner, and the longitudinal nonlinear mathematical model of the compound-wing UAV is derived.

[0011] S2: A novel fractional-order approach law designed on the basis of the traditional exponential power approach law by combining the ideas of double power approach law and fractional calculus.

[0012] S3: Based on the novel fractional-order approaching law, a fractional-order sliding mode controller for the pitch angle, airspeed and quadrotor altitude during the transition process is constructed in the longitudinal nonlinear mathematical model of the compound wing UAV. At the same time, a fixed-wing altitude controller is constructed as the outer loop of the pitch angle to jointly maintain altitude stability.

[0013] S4: Using an airspeed weighted control allocation strategy, the output of the fractional sliding mode controller is converted into the actuator output, thus completing the sliding mode control method for the transition process of the compound wing UAV.

[0014] According to the above scheme, based on the transition process model of the compound-wing UAV S1, assuming that the UAV flies horizontally without sideslip during the transition process, the longitudinal nonlinear mathematical model of the compound-wing UAV is as follows:

[0015]

[0016] In the formula: H is altitude; V is airspeed; θ, α, and γ are pitch angle, angle of attack, and track angle, respectively; q is pitch angular velocity; m is the mass of the UAV; I yy F is the moment of inertia about the y-axis; x w F z w and M y Let x and z be the components of the force and pitch moment along the UAV's airflow coordinate system, respectively, and be expressed as:

[0017]

[0018] M y =Mfixed +M rotor

[0019] In the formula: g is the gravitational acceleration of the UAV; T, D, L, M fixed F rotor and M rotor The thrust of the engine propeller, the drag of the fixed wing, the lift of the fixed wing, the pitching moment generated by the fixed wing, and the lift and pitching moment generated by the quadcopter are expressed as follows:

[0020]

[0021] D = 0.5ρV 2 SC D

[0022] L=0.5ρV 2 SC L

[0023] M fixed =0.5ρV 2 ScC M

[0024]

[0025] In the formula: ρ is the atmospheric density; S is the effective wing area; c is the mean aerodynamic chord length of the wing; c Tf and c Tr δ represents the thrust coefficients of the engine and the quadcopter propeller, respectively; d is the distance of the quadcopter from the center of gravity of the UAV; t ω1, ω2, ω3, and ω4 are the engine propeller speeds; C is the speed of the quadcopter propeller. D C L and C M These are the aerodynamic coefficients for fixed-wing drag, lift, and pitching moment, respectively.

[0026] Furthermore, the novel fractional-order reaching law described in S2 takes the following form:

[0027]

[0028] In the formula: s is the sliding surface function, For the differential of the sliding surface function, ε>0, k i >0, i = 1~3, 0 < p < 1, 1 < q < 2, α is a fractional calculus operator. Riemann-Liouville fractional calculus is The general formula is defined as follows:

[0029]

[0030] In the formula: Γ(x) represents the general formula for the Gamma function Γ(m-α), where m-1 < α < m, and m is a constant. (The rest of the formula is omitted as it is not directly related to the formula.) The symbol is abbreviated as D α .

[0031] Furthermore, based on the novel fractional-order reaching law, S3 constructs a fractional-order sliding mode controller for the pitch angle, airspeed, and altitude during the transition process of the compound-wing UAV, specifically including the following sub-steps:

[0032] S3.1. Using the total pitch moment as the virtual control variable, construct a pitch angle fractional-order sliding mode controller;

[0033] S3.2. Construct a fractional-order sliding mode controller for airspeed using engine propeller thrust as a virtual control variable;

[0034] S3.3. Using the lift of the quadrotor as a virtual control variable, a quadrotor altitude fractional sliding mode controller is constructed, and a fixed-wing altitude PID controller is constructed as the attitude outer loop to jointly maintain the altitude stability of the compound wing UAV.

[0035] S3.4. Based on Lyapunov stability theory, stability analysis is performed on the fractional-order sliding mode controller for pitch angle, airspeed, and quadrotor altitude.

[0036] According to S3.1, the sliding surface function form of the pitch angle fractional-order sliding mode controller is as follows:

[0037]

[0038] In the formula: s θ e is the pitch angle sliding surface function. θ =θ-θ d For pitch angle tracking error, For the differential of pitch tracking error, c θ >0 represents the pitch angle sliding surface coefficient, k θ >0 represents the pitch fractional order coefficient, D η Let η be a fractional calculus, and let η be the fractional calculus operator for the sliding surface.

[0039] The control law of the pitch angle fractional-order sliding mode controller is:

[0040]

[0041] In the formula: U θ This refers to the virtual control quantity of the pitch angle fractional-order sliding mode controller. ε θ >0, k i >0, i = 1 to 3 are the reaching law coefficients of the fractional-order sliding mode controller for the pitch angle. To define the second derivative of the pitch angle, I yy Let be the moment of inertia about the y-axis.

[0042] Furthermore, the sliding surface function form of the airspeed fractional-order sliding mode controller described in S3.2 is as follows:

[0043] s V =e V +λ V ∫e V dt+k V D η e V ,λ V >0,k V >0

[0044] In the formula: s V For the airspeed sliding surface function, e V =VV d For airspeed tracking error, λ V >0 represents the airspeed integral sliding surface coefficient, k V >0 represents the airspeed differential coefficient.

[0045] The control law of the fractional-order airspeed sliding mode controller is as follows:

[0046]

[0047] In the formula: U V ε is the virtual control quantity of the fractional-order airspeed sliding mode controller. V >0, k i >0, i=4~6 are the approach law coefficients of the fractional-order sliding mode controller for airspeed, Φ=-gsinγ+(F rotor sinα-D) / m, To define the differential of airspeed, m is mass, g is gravitational acceleration, γ is the trajectory angle, α is the angle of attack, D is drag, and F is... rotor It provides lift for the quadcopter.

[0048] Furthermore, the sliding surface function form of the quadrotor height fractional-order sliding mode controller described in S3.3 is as follows:

[0049]

[0050] In the formula: s H e is the quadrotor height sliding surface function. H =HH d For high tracking error, For the differential of the tracking error, c H >0 represents the height sliding surface coefficient, k H >0 represents a high-order calculus coefficient.

[0051] The control law of the quadrotor height fractional-order sliding mode controller is as follows:

[0052]

[0053] In the formula: U H This refers to the virtual control quantity of the quadcopter height fractional-order sliding mode controller. ε H >0, k i >0, i = 7~9 are the reaching law coefficients of the quadrotor height fractional sliding mode controller. To define the height of the second-order differential.

[0054] The fixed-wing altitude controller is in the following form:

[0055]

[0056] In the formula: k fHP k fHI k fHD These are the proportional, integral, and differential coefficients, respectively, θ d To set the pitch angle.

[0057] Furthermore, according to S3.4, the Lyapunov function is defined as follows:

[0058]

[0059] Taking the aforementioned pitch angle fractional-order sliding mode controller as an example, then

[0060]

[0061] Prove the sliding surface s of the fractional-order sliding mode controller for the pitch angle. θ It is asymptotically stable. Similarly, it can be proven that s H and s V It is gradually stable.

[0062] Furthermore, based on the pitch angle, airspeed, and quadrotor altitude fractional-order sliding mode controller and the fixed-wing altitude controller, S4 designs the airspeed weight control allocation strategy and calculates the actuator output of the compound-wing UAV, specifically including the following sub-steps:

[0063] S4.1 Design the airspeed weight control allocation strategy and calculate the force and torque required by the fixed-wing system and the quadrotor system;

[0064] S4.2 Calculate the engine propeller speed using engine thrust;

[0065] S4.3 Calculate the elevator deflection angle using the fixed-wing pitching moment;

[0066] S4.4 Calculate the quadcopter rotor speed using the quadcopter lift and pitch moment.

[0067] According to S4.1, the airspeed weight control allocation strategy is as follows:

[0068]

[0069] w rotor =1-w fixed

[0070] In the formula: w fixed For fixed-wing weights; w rotor V is the weight of the quadcopter; V is the current airspeed; V min V is the minimum airspeed of the transition mode; V is the maximum airspeed of the transition mode.

[0071] max

[0072] The forces and moments of the fixed-wing system and the quadcopter system are:

[0073] T = U V

[0074] M fixed =U θ w fixed

[0075] M rotor =U θ w rotor

[0076] F rotor =U H w rotor

[0077] Furthermore, the engine propeller speed described in S4.2 is calculated as follows:

[0078]

[0079] Furthermore, the formula for calculating the fixed-wing pitching moment described in S4.3 is as follows:

[0080]

[0081] In the formula: The pitch angular velocity is a dimensionless quantity.

[0082] The calculated elevator deflection angle is:

[0083]

[0084] Furthermore, the rotational speed of the quadcopter described in S4.4 is calculated as follows:

[0085]

[0086] The present invention has the following advantages:

[0087] This paper applies sliding mode variable structure nonlinear control to the transient process control of compound-wing UAVs. To overcome the shortcomings of traditional sliding mode exponential power-law approaching laws, such as chattering and inflexible parameters, a novel fractional-order approaching law is proposed, combining the concepts of double power-law approaching laws and fractional-order calculus. A fractional-order sliding mode controller is constructed to improve the rapid convergence of the sliding surface and suppress chattering. Simultaneously, an airspeed weighted control allocation strategy is employed to distribute control inputs and achieve actuator computation. Compared with traditional PID control and sliding mode control, this sliding mode control method reduces steady-state control error, enhances control accuracy, improves the robustness of the flight control system, and achieves smooth control during the transient process, providing a new approach for the transient process control of compound-wing UAVs. Attached Figure Description

[0088] Figure 1 The structural block diagram of the sliding mode control method for the transition process of a compound-wing UAV provided by the present invention is shown.

[0089] Figure 2 The flowchart of the sliding mode control method for the transition process of the compound wing UAV provided by the present invention is shown.

[0090] Figure 3 The block diagram of the fractional-order sliding mode controller for the compound-wing UAV provided by this invention is shown in MATLAB / SIMULINK.

[0091] Figure 4 The MATLAB / SIMULINK block diagram of the longitudinal mathematical model of the compound-wing UAV provided by this invention.

[0092] Figure 5 The airspeed tracking curve of the transition process of the compound wing UAV provided by this invention is shown in the figure.

[0093] Figure 6 The diagram showing the airspeed tracking error during the transition process of a compound-wing UAV provided by this invention;

[0094] Figure 7 The pitch angle tracking curve diagram of the transition process of the compound wing UAV provided by the present invention is shown.

[0095] Figure 8 The diagram showing the pitch angle tracking error during the transition process of a compound-wing UAV provided by this invention.

[0096] Figure 9 The altitude tracking curve of the transition process of the compound wing UAV provided by this invention is shown in the figure.

[0097] Figure 10The diagram showing the altitude tracking error during the transition process of the compound-wing UAV provided by this invention is shown.

[0098] Figure 11 The diagram showing the sliding mode control weight allocation during the transition process of the compound wing UAV provided by this invention. Detailed Implementation

[0099] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0100] like Figures 1-2 As shown, this embodiment provides a transient control method for a compound-wing unmanned aerial vehicle based on fractional-order sliding mode, including the following steps:

[0101] Step 1: Based on the Newton-Euler equations, integrate the rotor and fixed-wing dynamics of the transition process of the compound-wing UAV to derive the longitudinal nonlinear mathematical model of the compound-wing UAV:

[0102]

[0103] In the formula: H is altitude; V is airspeed; θ, α, and γ are pitch angle, angle of attack, and track angle, respectively; q is pitch angular velocity; m is the mass of the UAV; I yy Let F be the moment of inertia about the y-axis. x w F z w and M y Let x and z be the components of the force and pitch moment along the UAV's airflow coordinate system, respectively, and be expressed as:

[0104]

[0105] M y =M fixed +M rotor

[0106] In the formula: g is the gravitational acceleration of the UAV; T, D, L, M fixed F rotor and M rotor The thrust of the engine propeller, the drag of the fixed wing, the lift of the fixed wing, the pitching moment generated by the fixed wing, and the lift and pitching moment generated by the quadcopter are expressed as follows:

[0107]

[0108] D = 0.5ρV 2 SC D

[0109] L=0.5ρV 2 SC L

[0110] M fixed =0.5ρV 2 ScC M

[0111]

[0112] In the formula: ρ is the atmospheric density; S is the effective wing area; c is the mean aerodynamic chord length of the wing; c Tf and c Tr δ represents the thrust coefficients of the engine and the quadcopter propeller, respectively; d is the distance of the quadcopter from the center of gravity of the UAV; t ω1, ω2, ω3, and ω4 are the engine propeller speeds; C is the speed of the quadcopter propeller. D C L and C M These are the aerodynamic coefficients for fixed-wing drag, lift, and pitching moment, respectively.

[0113] Step 2: Based on the longitudinal nonlinear mathematical model of the compound-wing UAV, and using a novel fractional-order reaching law, construct a fractional-order sliding mode controller for pitch angle, airspeed, and quadrotor altitude. Simultaneously, construct a fixed-wing altitude controller as the outer loop for pitch angle to jointly maintain altitude stability. This includes the following sub-steps:

[0114] Step 2.1: Based on the traditional exponential power reaching law, the novel fractional reaching law is designed by combining double power terms and fractional calculus, in the following form:

[0115]

[0116] In the formula: s is the sliding surface function, For the differential of the sliding surface function, ε>0, k i >0, i = 1~3, 0 < p < 1, 1 < q < 2, α is a fractional calculus operator. Riemann-Liouville fractional calculus is The general formula is defined as follows:

[0117]

[0118] In the formula: Γ(x) represents the general formula for the Gamma function Γ(m-α), where m-1 < α < m, and m is a constant. (The rest of the formula is omitted as it is not directly related to the formula.) The symbol is abbreviated as D α .

[0119] Step 2.2: Using the pitch moment of the compound-wing UAV as the virtual control variable, construct the fractional-order sliding mode controller for the pitch angle. The sliding surface function of the fractional-order sliding mode controller for the pitch angle is:

[0120]

[0121] In the formula: s θ e is the pitch angle sliding surface function. θ =θ-θ d For pitch angle tracking error, For the differential of pitch tracking error, c θ >0 represents the pitch angle sliding surface coefficient, k θ >0 represents the pitch fractional order coefficient, D η For fractional calculus, η is the fractional calculus operator for the sliding surface;

[0122] The control law of the pitch angle fractional-order sliding mode controller is:

[0123]

[0124] In the formula: U θ This refers to the virtual control quantity of the pitch angle fractional-order sliding mode controller. ε θ >0, k i >0, i = 1 to 3 are the reaching law coefficients of the fractional-order sliding mode controller for the pitch angle. To define the second-order differential of the pitch angle.

[0125] Step 2.3: Construct the fractional-order airspeed sliding mode controller using the engine propeller thrust as the virtual control variable. The sliding surface function of the fractional-order airspeed sliding mode controller is:

[0126] s V =e V +λ V ∫e V dt+k V D η e V ,λ V >0,k V >0

[0127] In the formula: s V For the airspeed sliding surface function, e V =VV d For airspeed tracking error, λ V >0 represents the airspeed integral sliding surface coefficient, k V >0 represents the airspeed differential coefficient.

[0128] The control law of the fractional-order airspeed sliding mode controller is as follows:

[0129]

[0130] In the formula: Φ=-gsinγ+(F rotor sinα-D) / m, U V ε is the virtual control quantity of the fractional-order airspeed sliding mode controller. V >0, k i >0, i = 4 to 6 are the reaching law coefficients of the fractional-order sliding mode controller for airspeed. To define the differential of airspeed, m is mass, g is gravitational acceleration, γ is the trajectory angle, α is the angle of attack, D is drag, and F is... rotor It provides lift for the quadcopter.

[0131] Step 2.4: Using the quadrotor lift as the virtual control variable, construct the quadrotor height fractional-order sliding mode controller. The sliding surface function of the quadrotor height fractional-order sliding mode controller is:

[0132]

[0133] In the formula: s H e is the quadrotor height sliding surface function. H =HH d For high tracking error, For the differential of the tracking error, c H >0 represents the height sliding surface coefficient, k H >0 represents a high-order calculus coefficient;

[0134] The control law of the quadrotor height fractional-order sliding mode controller is as follows:

[0135]

[0136] In the formula: U H This refers to the virtual control quantity of the quadcopter height fractional-order sliding mode controller. ε H >0, k i >0, i = 7~9 are the reaching law coefficients of the quadrotor height fractional sliding mode controller. To define the height of the second-order differential.

[0137] The fixed-wing altitude controller is in the following form:

[0138]

[0139] In the formula: k fHP k fHI k fHD These are the proportional, integral, and differential coefficients, respectively, θ d To set the pitch angle.

[0140] Step 3: Based on the pitch angle, airspeed, and quadrotor altitude fractional-order sliding mode controller and the fixed-wing altitude controller, design an airspeed weight control allocation strategy and calculate the actuator output of the compound-wing UAV. This includes the following sub-steps:

[0141] Step 3.1: Design the airspeed weight control allocation strategy and calculate the forces and moments of the fixed-wing system and the quadcopter system.

[0142] The airspeed weight control allocation strategy is as follows:

[0143]

[0144] w rotor =1-w fixed

[0145] In the formula: w fixed For fixed-wing weights; w rotor V is the weight of the quadcopter; V is the current airspeed; V min V is the minimum airspeed for the transition mode; max This is the maximum airspeed of the transition mode.

[0146] Based on the aforementioned airspeed weight control allocation strategy, the forces and moments of the fixed-wing system and the quadrotor system are calculated as follows:

[0147] T = U V

[0148] M fixed =U θ w fixed

[0149] M rotor =U θ w rotor

[0150] F rotor =U H w rotor

[0151] Step 3.2: Based on the forces and torques of the fixed-wing system and the quadcopter system, calculate the actuator outputs, including the elevator deflection angle, the engine propeller speed, and the quadcopter propeller speed.

[0152] The calculated propeller speed of the engine is:

[0153]

[0154] The formula for calculating the fixed-wing pitching moment is:

[0155]

[0156] In the formula: The pitch angular velocity is a dimensionless quantity.

[0157] The calculated elevator deflection angle is:

[0158]

[0159] The calculated rotational speed of the quadcopter is:

[0160]

[0161] Figure 3 This is a MATLAB / SIMULINK block diagram of the fractional sliding mode controller for the compound wing UAV. Based on this, the S-Function module function is written according to the above steps to establish the fractional sliding mode controller (FOSMC). Figure 4 This is a MATLAB / SIMULINK block diagram of the mathematical model of the compound-wing UAV. The fractional sliding mode controller is applied to the mathematical model of the compound-wing UAV to simulate and control the transient process of the compound-wing UAV.

[0162] To verify the control effect, a certain type of compound-wing UAV was selected as the object in the simulation test example of this invention. The simulation time was set to 20s, and V was taken as... max 21 m / s, V min The speed is 6 m / s, and the drone is set to an altitude of H. d The airspeed is set to 50m and V. d for:

[0163]

[0164] Figures 5-10 The simulation results of the sliding mode control during the transition process of the compound wing UAV are derived from... Figure 5 and Figure 6 It is evident that the airspeed of the compound-wing UAV exhibits smaller overshoot, smaller tracking error, and better control performance under a fractional-order sliding mode controller; Figure 7 and Figure 8 It is evident that the pitch angle tracking error is smaller and the control accuracy is higher under the fractional-order sliding mode controller; Figure 9 and Figure 10 It is evident that the quadcopter height fractional sliding mode controller can better maintain height stability during the transition process.

[0165] Figure 11 The diagram shows the control weight allocation during the transition process of the compound-wing UAV. As can be seen, the airspeed weight control allocation strategy can be correctly executed during the simulation, verifying the effectiveness of the strategy.

[0166] Based on the above simulation tests, the transient process control method for compound-wing UAVs based on fractional sliding mode proposed in this invention reduces control tracking errors, improves the robustness of the compound-wing UAV flight control system, and achieves smooth control of the transient process.

[0167] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A transient control method for a compound-wing unmanned aerial vehicle based on fractional-order sliding mode, characterized in that, Controlling the transition process of a compound-wing UAV based on sliding mode variable structure control specifically includes: Step S-1: Perform integrated modeling of rotor and fixed-wing dynamics during the transition process of the compound-wing UAV, and derive the longitudinal nonlinear mathematical model of the compound-wing UAV; Step S-2: A novel fractional-order approach law is designed based on the traditional exponential power approach law by combining the ideas of double power approach law and fractional calculus. The novel fractional-order reaching law takes the form of: In the formula: For sliding surface functions, For the differential of the sliding surface function, , , , For fractional calculus operators, Riemann-Liouville fractional calculus is The general formula is defined as follows: In the formula: The Gamma function is The general formula, , It is a constant, and the subsequent The symbol is abbreviated as ; Step S-3: Based on the novel fractional-order reaching law, construct a fractional-order sliding mode controller for the pitch angle, airspeed, and quadrotor altitude during the transition process in the longitudinal nonlinear mathematical model of the compound wing UAV. At the same time, construct a fixed-wing altitude controller as the outer loop of the pitch angle to jointly maintain altitude stability. Step S-3-1: Construct a fractional-order sliding mode controller for pitch angle using pitch moment as the virtual control variable; The sliding surface function form of the pitch angle fractional-order sliding mode controller is: In the formula: For pitch angle sliding surface function, For pitch angle tracking error, For the differential of pitch angle tracking error, The sliding surface coefficient is the pitch angle. For pitch fractional order coefficients, For fractional calculus, For sliding surface fractional calculus operators; The control law of the pitch angle fractional-order sliding mode controller is: In the formula: This refers to the virtual control quantity of the pitch angle fractional-order sliding mode controller. , , The approach law coefficients of the fractional-order sliding mode controller for the pitch angle are... To define the second derivative of the pitch angle, Let y be the moment of inertia about the y-axis; Step S-3-2: Using engine propeller thrust as a virtual control variable, construct a fractional-order airspeed sliding mode controller; The sliding surface function form of the fractional-order airspeed sliding mode controller is: In the formula: For airspeed sliding surface function, For airspeed tracking error, The integral sliding surface coefficient for airspeed is... The integral coefficients for airspeed; The control law of the airspeed fractional-order sliding mode controller is: In the formula: This refers to the virtual control quantity of the fractional-order airspeed sliding mode controller. , The approach law coefficients of the fractional-order airspeed sliding mode controller are... , , To set the airspeed derivative, For quality, It is the acceleration due to gravity. For the track angle, For the angle of attack, As resistance, For the lift of the quadcopter; Step S-3-3: Using the lift of the quadrotor as a virtual control variable, construct a quadrotor altitude fractional sliding mode controller, and using the fixed-wing altitude controller as the attitude outer loop, construct a fixed-wing altitude PID controller to jointly maintain the altitude stability of the compound wing UAV. The sliding surface function of the quadrotor height fractional-order sliding mode controller is: In the formula: For the quadrotor's height sliding surface function, For high tracking error, For the differential of the high tracking error, The sliding surface coefficient is the height. These are highly calculus coefficients; The control law of the quadrotor height fractional-order sliding mode controller is as follows: In the formula: This refers to the virtual control quantity of the quadcopter height fractional-order sliding mode controller. , , The coefficients of the reaching law of the quadrotor height fractional-order sliding mode controller are: To define the second-order differential of the height; Step S-4: Based on the pitch angle, airspeed, and quadrotor altitude fractional sliding mode controller and the fixed wing altitude controller, design an airspeed weighted control allocation strategy to allocate control quantities and calculate the actuator output.

2. The transient control method for a compound-wing unmanned aerial vehicle based on fractional-order sliding mode according to claim 1, characterized in that, In step S-3-3, the fixed-wing altitude controller is in the following form: In the formula: , , These are the proportional, integral, and differential coefficients, respectively.

3. The transient control method for a compound-wing unmanned aerial vehicle based on fractional-order sliding mode according to claim 1, characterized in that, Step S-4 includes the following sub-steps: Step S-4-1: Design the airspeed weight control allocation strategy and calculate the forces and moments of the fixed-wing system and the quadrotor system; Step S-4-2: Based on the forces and torques of the fixed-wing system and the quadcopter system, calculate the actuator outputs, including the elevator deflection angle, the engine propeller speed, and the quadcopter propeller speed.

Images