A fixed-time sliding mode control method and system for tilt-rotor unmanned aerial vehicles with preset performance

Abstract

This invention relates to the field of unmanned aerial vehicle (UAV) control technology, and proposes a fixed-time sliding mode control method and system for tilt-rotor UAVs with preset performance. The method includes: constructing a motion model of the tilt-rotor UAV; constructing a conversion error based on a preset performance function; designing a fixed-time non-singular terminal sliding surface using adaptive gain; and, based on the motion model, fusing the control model with the non-singular terminal sliding surface to construct a control law, and controlling the tilt-rotor UAV based on the control law. This invention solves the singularity problem existing in the prior art and accelerates the convergence speed.

Description

Technical Field

[0001] This invention relates to the field of unmanned aerial vehicle (UAV) control technology, specifically to a fixed-time sliding mode control method and system for a tilt-rotor UAV with preset performance. Background Technology

[0002] Tiltrotor drones, as a new type of intelligent aircraft, flexibly switch between multi-rotor and fixed-wing modes by changing the rotor orientation through a tilting mechanism, enabling them not only to take off and land vertically but also to achieve rapid cruising. Due to their runway-free operation, high payload capacity, and high-speed, long-endurance capabilities, tilttrotor drones have broad application prospects in fields such as terrain reconnaissance, emergency rescue, logistics delivery, and agricultural and forestry plant protection. However, the unique airframe structure of tilttrotor drones gives them multimodal characteristics, strong nonlinearity, and strong aerodynamic interference. Especially during the transition between flight modes, their complex aerodynamic characteristics pose a significant challenge to flight control.

[0003] Currently, there are relevant studies on the flight control problem of tiltrotor UAVs. For example, model predictive control is used, but this method has a large computational load, slow response speed, and high requirements for model accuracy; some use fuzzy active disturbance rejection control, which has good robustness, but its convergence speed is slow and difficult to meet the needs of practical applications; some use neural network-based adaptive sliding mode control, which has a simple controller structure and fast response speed, but its tracking error can only achieve convergence in a finite time and is greatly affected by the initial error; in addition, some studies have proposed a pre-set performance robust control method, which can simultaneously control steady-state and transient performance, but its performance boundary converges exponentially, the convergence speed is slow, and it is limited by the initial error, so it cannot achieve global pre-set performance control. Summary of the Invention

[0004] To overcome the shortcomings of the prior art in balancing robustness and convergence speed, the present invention provides a fixed-time sliding mode control method and system for tilt-rotor unmanned aerial vehicles with preset performance.

[0005] To achieve the above-mentioned technical effects, the technical solution of the present invention is as follows:

[0006] This invention proposes a fixed-time sliding mode control method for tilt-rotor unmanned aerial vehicles with preset performance, comprising the following steps:

[0007] Construct a motion model for a tiltrotor UAV; build a conversion error based on a preset performance function; and design a fixed-time non-singular terminal sliding surface using adaptive gain.

[0008] Based on the motion model, the control model is fused with the non-singular terminal sliding surface to construct a control law, and the tilt-rotor UAV is controlled based on the control law.

[0009] This invention also proposes a fixed-time sliding mode control system for tilt-rotor unmanned aerial vehicles with preset performance, comprising:

[0010] Control law solving module: It carries a motion model of a tiltrotor UAV; a control model based on preset performance and a non-singular terminal sliding surface; based on the motion model, it merges the control model and the non-singular terminal sliding surface and solves the control law;

[0011] Unmanned Aerial Vehicle (UAV) Control Module: Controls the tiltrotor UAV based on the aforementioned control law.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0013] This invention proposes a fixed-time sliding mode control method and system for tiltrotor UAVs with preset performance. The control law designed based on the sliding surface achieves system convergence within a fixed time, which is more suitable for the rapidly changing flight conditions of UAV systems compared to traditional exponential and finite-time convergence. Specifically, by designing a non-singular sliding surface, the singularity problem inherent in traditional fixed-time sliding mode control is overcome, eliminating the need for additional auxiliary functions and simplifying the controller structure. Furthermore, the preset performance function ensures that the UAV reaches its steady-state range within a fixed time, achieving global preset performance control. By organically combining the sliding surface with the preset performance control strategy, an efficient and precise flight control solution is provided for tiltrotor UAVs. Attached Figure Description

[0014] Figure 1 This is a flowchart of a fixed-time sliding mode control method for a tiltrotor UAV with preset performance, as described in Example 1.

[0015] Figure 2 This is an architecture diagram of the fixed-time sliding mode control system for a tilt-rotor UAV with preset performance in Example 2.

[0016] Figure 3 The position control curve of a tiltrotor UAV in simulation control.

[0017] Figure 4 The tracking error curve of a tiltrotor UAV in simulation control.

[0018] Figure 5 This is the attitude angle control curve for a tiltrotor UAV in simulation control.

[0019] Figure 6 The image shows the attitude angle tracking error curve of a tiltrotor UAV in simulation control. Detailed Implementation

[0020] The accompanying drawings are for illustrative purposes only and should not be construed as limiting the invention.

[0021] It will be understood by those skilled in the art that some well-known descriptions may be omitted in the accompanying drawings.

[0022] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0023] Example 1

[0024] This embodiment proposes a fixed-time sliding mode control method for tilt-rotor unmanned aerial vehicles with preset performance, such as... Figure 1 The diagram shown is a flowchart of a fixed-time sliding mode control method for a tilt-rotor UAV with preset performance, as described in this embodiment.

[0025] The fixed-time sliding mode control method for tilt-rotor UAVs with preset performance proposed in this embodiment includes the following steps:

[0026] Construct a motion model for a tiltrotor UAV; build a conversion error based on a preset performance function; and design a non-singular terminal sliding surface at a fixed time using adaptive gain control.

[0027] Based on the motion model, the control model is fused with the non-singular terminal sliding surface to construct a control law, and the tilt-rotor UAV is controlled based on the control law.

[0028] In this embodiment, the steady-state performance of the UAV is improved by combining sliding mode control and a preset performance control strategy. Specifically, by designing a control model that can converge within a fixed time, it is better able to adapt to the rapidly changing flight state of the UAV than traditional exponential convergence and finite-time convergence methods. Secondly, by designing a non-singular sliding surface, common singularity problems are completely eliminated, eliminating the need to introduce complex auxiliary functions and greatly simplifying the control algorithm. By combining the high responsiveness of sliding mode control with the transient guarantee of preset performance control, a fast, accurate, and stable flight control method is constructed for the tiltrotor UAV system, significantly improving the system's adaptability and reliability under complex flight conditions.

[0029] In an optional embodiment, the step of constructing the mathematical model of the tiltrotor unmanned aerial vehicle includes:

[0030] Construct the position loop model and attitude loop model of the UAV;

[0031] The six-degree-of-freedom motion equations are obtained based on the position loop model and attitude loop model.

[0032] In this embodiment, by constructing the motion model into a position loop model and an attitude loop model, the translational and rotational motion characteristics of the UAV are effectively separated, making the kinematic and dynamic analysis clearer and more intuitive, thereby improving the accuracy of UAV control model modeling.

[0033] In an optional embodiment, the step of constructing the UAV's position loop model includes:

[0034] By using a transformation matrix to correlate the velocity in the fuselage coordinate system with the position in the ground coordinate system, the velocity and acceleration of the UAV are modeled. The rotor thrust, aerodynamic force, and gravity within the acceleration are also modeled, resulting in the UAV's position loop model, expressed as follows:

[0035]

[0036]

[0037] Where, P = [x e ,y e ,z e ] T Let v be the position vector of the tiltrotor UAV in the ground coordinate system, v = [v x ,v y ,v z ] T This represents the velocity vector of the tiltrotor UAV in the ground coordinate system. Let [u, v, w] be the transformation matrix from the fuselage coordinate system to the ground coordinate system. T Let be the velocity vector of the UAV in the fuselage coordinate system; Let m be the acceleration, d be the mass of the tiltrotor UAV, and d be the acceleration. F For the total disturbance of the position loop, F p The force F generated by the rotor a For the aerodynamic forces generated by the wings and fuselage, F g To tilt the rotor without human gravity; T is the transformation matrix from the rotor coordinate system to the fuselage coordinate system. i (i = 1, 2, 3, 4) represents the thrust generated by each rotor, [D, Y, L] T These represent the drag, lateral force, and lift experienced by the tiltrotor unmanned aerial vehicle (UAV). Where σ is the dynamic pressure and σ is the air density, [C D C Y C L ] T These represent the drag coefficient, force coefficient, and lift coefficient, respectively; S is the projected area of ​​the tiltrotor UAV; and g is the acceleration due to gravity.

[0038] In this embodiment, by employing a transformation matrix to correlate the velocity in the fuselage coordinate system with the position in the ground coordinate system, and by accurately modeling the velocity and acceleration, the motion state of the UAV in three-dimensional space can be accurately described and analyzed. Furthermore, key forces in the acceleration, such as rotor thrust, aerodynamic forces, and gravity, are modeled to ensure that the model comprehensively reflects the actual force conditions and motion characteristics of the UAV. The position loop model accurately describes the position change patterns of the UAV, providing detailed and reliable reference data for the design of subsequent control algorithms.

[0039] In an optional embodiment, the step of constructing the attitude loop model of the UAV includes:

[0040] The attitude angular velocity and attitude angle derivative of the tiltrotor UAV are correlated by a transformation matrix, and the dynamic equation of the attitude angle is constructed. The total torque of the tiltrotor UAV is decomposed, and the torque generated by the rotor and the aerodynamic torque of the wing or fuselage are modeled to obtain the attitude loop model of the UAV, the expression of which is as follows:

[0041]

[0042] Where Ω = [φ, θ, ψ] T Let ω represent the attitude angle of the tiltrotor UAV, where ω = [p, q, r]. T For attitude angular velocity, This is the transformation matrix from attitude angular velocity to attitude angular derivative. l is the distance between the rotors, and τ... i =k P Ω i 2 (i = 1, 2, 3, 4) represents the anti-torque generated by the rotor, k P Ω is the anti-torque coefficient of the rotor. i For the rotational speed of each rotor, l w For the wingspan of tiltrotor drones, It is the mean aerodynamic chord length, [C l C m C n ] T These are the roll, pitch, and yaw moments, respectively, and Ф is the rotor tilt angle.

[0043] In this embodiment, a transformation matrix is ​​used to correlate the attitude angular velocity and attitude angle differential of the tiltrotor UAV, and a dynamic equation for the attitude angle is constructed to achieve an accurate description of the attitude change law of the UAV. By decomposing the total torque and modeling in detail the torque generated by the rotor and the aerodynamic torque of the wing or fuselage, the model can comprehensively reflect the torque distribution and dynamic characteristics in the attitude control of the UAV, improving the analytical ability of the attitude change process of the UAV. At the same time, the fine modeling of different torques ensures the physical authenticity and calculation accuracy of the attitude loop model, enabling the model to accurately reflect the attitude response characteristics of the tiltrotor UAV in complex flight environments.

[0044] In an optional embodiment, the step of constructing the conversion error based on a preset performance function includes:

[0045] The tracking error and its boundary are designed based on a preset performance function;

[0046] The design error transformation function transforms the tracking error mapping constrained by the preset performance function into a new unconstrained transformation error;

[0047] A control model is constructed based on the aforementioned unrestricted conversion error;

[0048] The expression for the error transformation function Ψ(ε) is as follows:

[0049]

[0050]

[0051] Where sign() is the sign function; 0 < δ ≤ 1; e(0) is the initial tracking error.

[0052] Specifically, the tracking error of the control model is defined as e = xx. d Where x is the current state of the drone, x d This represents the desired state for the drone.

[0053] The fixed-time preset performance function is designed as follows:

[0054]

[0055] Where ρ0 is the initial value of the performance function, ρ ∞ >0 represents the steady-state value of the performance function, and ρ0>ρ ∞ T f The time required for the design to reach its steady-state value.

[0056] To achieve the desired performance requirements, the asymmetric tracking error boundary is designed as follows:

[0057] -γ1ρ(t) <e(t)<γ2ρ(t)

[0058] In general preset performance control, the tracking error must satisfy the condition that the initial tracking error is within the initial boundary range of the preset performance function, that is, satisfy the inequality -γ1ρ(0). <e(0)<γ2ρ(0)。

[0059] To relax the restrictions, the improved error transformation function is defined as follows:

[0060]

[0061] Where ε is the conversion error. Let γ3 be a constant greater than 1, then the expression for γ3 is:

[0062]

[0063] Inverting the error transformation function yields the new unrestricted transformation error:

[0064]

[0065] As shown in the above equation, when a new conversion error ε is used instead of the original error e(t) to establish the controller, if the original error e(t) is close to the preset performance boundary, the value of the conversion error ε will increase rapidly, resulting in a large control input, causing e(t) to return to the preset performance boundary. Through the error conversion process, the system originally controlled by the original constrained error is transformed into one controlled by an unconstrained error, thus achieving the requirement of preset performance control.

[0066] Subsequently, to avoid the equilibrium point shift problem caused by the asymmetric transformation boundary, the error transformation was further designed as follows:

[0067]

[0068] To facilitate subsequent controller design, the relationship between the derivative of the error transformation and the original error is obtained as follows:

[0069]

[0070] Will The expression is abbreviated as:

[0071]

[0072] In this embodiment, a tracking error constraint boundary is designed using a preset performance function, and an improved error transformation function is introduced to convert the original tracking error, which is constrained by the preset performance boundary, into an unconstrained error. This effectively solves the problem of strictly limiting the initial tracking error in traditional preset performance control methods, making the control model globally applicable and enhancing its applicability and robustness. Furthermore, the error transformation function design can rapidly increase the control input when the original error approaches the preset performance boundary, thereby ensuring that the error quickly returns to the preset performance range, ensuring the system's transient performance and accelerating the convergence speed.

[0073] In an optional embodiment, the step of designing a fixed-time sliding surface in conjunction with adaptive gain includes:

[0074] Define a fixed-time sliding surface that includes control parameters and state variables;

[0075] By introducing a non-singular terminal sliding mode function and incorporating adaptive gain control into the derivative of the sliding surface, a non-singular terminal sliding surface is obtained; the expression for the sliding surface s is as follows:

[0076]

[0077] sig y (x)=|x| y sign(x)

[0078] Where σ1>1, 1<σ2<2;

[0079] The derivative expression for the sliding surface is as follows:

[0080]

[0081] in, For adaptive control of the gain, l2>0, l3>0, n1>1, 0 <n2<1,

[0082] In this embodiment, by combining adaptive gain control with a sliding surface designed for a fixed time, rapid convergence and precise control of the system state are achieved, overcoming the singularity problem in traditional sliding mode control. Specifically, the fixed-time sliding surface is defined based on control parameters and state variables, ensuring that the system reaches a stable state within a fixed time. By introducing a non-singular terminal function and embedding adaptive gain control in the derivative of the sliding surface, the robustness and responsiveness of the controller are further enhanced. The adaptive control gain can be adjusted in real time according to the system state, rapidly increasing the control input when the error is large, thereby accelerating convergence and compensating for external disturbances; while reducing the control force when the error is small, avoiding overshoot of the control input and improving the stability of the system.

[0083] In an optional embodiment, the step of constructing the control law includes:

[0084] Introduce unrestricted error within the sliding surface at a fixed time;

[0085] Based on the unconstrained error combined with the position loop and attitude loop models, control expressions for position tracking error and attitude tracking error are constructed respectively, and the control law is obtained.

[0086] Specifically, based on the designed fixed-time non-singular terminal sliding surface and control model, the new sliding surface can be obtained as follows:

[0087]

[0088] Differentiating both sides of the above equation and combining the derivative with the designed sliding surface, we can obtain:

[0089]

[0090] From the relationship between the original error and the transformed error, and the position loop model of the tilt-rotor UAV, we can obtain:

[0091]

[0092] Among them, e P =PP d Let P be the position tracking error, and P be the original position. d Given the desired position, the control expression u based on the position loop model can be obtained. P for:

[0093]

[0094] In this context, subscripts P1, P2, and P3 represent the parameters of the position loop controller.

[0095] The position loop controller consists of the equivalent control law of the designed sliding surface and the reaching law of the sliding surface derivative. The reaching law ensures that the controlled state can reach the sliding surface quickly and in a fixed time, i.e., s=0. At the same time, the upper bound of the disturbance is adaptively estimated through adaptive gain, which ensures the stability of the control system and improves its robustness.

[0096] Similarly, the relationship between the original error and the transformation error of the tiltrotor UAV attitude loop can be obtained as follows:

[0097]

[0098] Among them, e Ω =Ω-Ω d It is the attitude tracking error, Ω dLet the desired attitude be denoted as . Therefore, the control expression based on the attitude loop model can be obtained as follows:

[0099]

[0100] In this context, the subscripts Ω1, Ω2, and Ω3 represent the parameters of the attitude loop controller.

[0101] A complete flight control law for a tiltrotor UAV consists of a position loop controller and an attitude loop controller, with the designed position loop controller as the outer loop and the attitude loop controller as the inner loop. When the desired trajectory is input, the position loop controller first performs calculations, and its output is used as the input to the attitude loop controller. The output of the attitude loop controller is then fed into the control distribution system to obtain the required rotor speed Ω, rotor tilt angle Ф, and aerodynamic control surface deflection angle, thereby achieving flight control of the tiltrotor UAV.

[0102] In this embodiment, efficient and precise control of a tiltrotor UAV within a fixed time period is achieved by constructing a control law, while significantly enhancing the applicability and dynamic performance of the control system. Based on an error-free design, the limitations of traditional control laws on initial errors are effectively overcome, ensuring the controller's stability across the entire range. Furthermore, by introducing the derivative of the sliding mode surface and adaptive control gain, the control law parameters can be dynamically adjusted. This allows the system to provide stronger control input to accelerate convergence when the error is large, while smoothly adjusting the input when the error is small, significantly improving the control system's response speed and steady-state accuracy.

[0103] Example 2

[0104] This embodiment proposes a fixed-time sliding mode control system for tiltrotor unmanned aerial vehicles (UAVs) with preset performance, applying the fixed-time sliding mode control method for tiltrotor UAVs with preset performance proposed in Embodiment 1. For example... Figure 2 The diagram shown is an architecture diagram of the fixed-time sliding mode control system for a tilt-rotor UAV with preset performance in this embodiment.

[0105] This embodiment proposes a fixed-time sliding mode control system for a tilt-rotor unmanned aerial vehicle with preset performance, including:

[0106] Control law solving module: It carries a motion model of a tiltrotor UAV; a control model based on preset performance and a non-singular terminal sliding surface; based on the motion model, it merges the control model and the non-singular terminal sliding surface and solves the control law;

[0107] Unmanned Aerial Vehicle (UAV) Control Module: Controls the tiltrotor UAV based on the aforementioned control law.

[0108] It is understood that the system in this embodiment corresponds to the method in Embodiment 1 above, and the options in Embodiment 1 above are also applicable to this embodiment, so they will not be described again here.

[0109] Example 3

[0110] This embodiment proposes a computer device, including a memory and a processor. The memory stores computer-readable instructions, wherein when the computer-readable instructions are executed by the processor, the processor performs the steps of the fixed-time sliding mode control method for tilt-rotor UAVs with preset performance proposed in Embodiment 1.

[0111] Example 4

[0112] This embodiment proposes a storage medium storing computer-readable instructions, wherein when the computer-readable instructions are executed by a processor, they implement the steps of the fixed-time sliding mode control method for tilt-rotor UAVs with preset performance proposed in Embodiment 1.

[0113] Example 5

[0114] This embodiment simulates the control of a tiltrotor drone based on embodiments 1 to 4.

[0115] The simulation lasted 15 seconds, with a sampling time of 0.001 seconds. Some parameters of the tiltrotor UAV are as follows: mass m = 1575 kg, moment of inertia I = [0.459, 0.446, 1.609]. T kg·m 2 Wingspan w =2.1m, projected area S =0.48m 2 The average aerodynamic chord length c = 0.25m and the rotor spacing l = 0.54m.

[0116] The initial position of the tiltrotor UAV designed in the simulation is [1.5, -2, 0]. T m, initial attitude angle is [6, -10, 4] T deg.

[0117] The desired position of the tiltrotor UAV designed in the simulation is [2sin(0.1πt)+sin(0.3πt),sin(0.1πt),-0.25t-0.5]. T m, the desired attitude angle is [15sin(0.75πt), 15sin(0.75πt), 0.2t-2] T deg. The perturbation distances for the position loop and attitude loop are set to d = sin(πt).

[0118] Figure 3-6 To control the simulation results; among which, Figure 3Position control curves for tiltrotor unmanned aerial vehicles; Figure 4 The tracking error curve for a tiltrotor UAV; Figure 5 The attitude angle control curve for a tiltrotor unmanned aerial vehicle; Figure 6 The attitude angle tracking error curve of the tiltrotor UAV.

[0119] Figure 3 The changes in the UAV's position during the control process are demonstrated. It can be seen that the desired position curve and the actual position curve quickly converge to the same value within a short period, without significant overshoot or oscillation. This verifies the high efficiency and rapid response capability of the position controller of this invention.

[0120] Figure 4 The variation of the UAV position tracking error is demonstrated. It can be seen that the initial error is large, but then the error rapidly converges to zero within a short period and stabilizes within the preset performance range. This rapid convergence characteristic indicates that the controller can effectively control the error within a fixed time, which verifies the design effectiveness of the sliding surface and error transformation function in this invention. Furthermore, no oscillations or singularities occurred during the convergence phase, further demonstrating the superiority of non-singular terminal sliding mode control.

[0121] Figure 5 The dynamic changes of the UAV's attitude angles (such as roll, pitch, and yaw) during the control process are demonstrated. It can be seen that the attitude control response time is significantly less than 2 seconds, and there is no significant overshoot or oscillation during convergence. This demonstrates the high precision and strong robustness of the attitude loop controller of this invention under dynamic conditions.

[0122] Figure 6 The dynamic changes in attitude angle tracking error are demonstrated. It can be seen that the initial error is large, but it rapidly decreases to zero within a short time and stabilizes within the steady-state range. This verifies that the attitude controller of this invention can accurately control the attitude angle of the UAV and avoids control problems caused by boundary effects in traditional control systems.

[0123] Depend on Figure 3-6 As can be seen, the control method designed based on this invention can keep the tracking error of the controlled state within the set asymmetric preset performance function. Even when the initial error is outside the preset performance range, singularity can be avoided, and the tracking error can be quickly controlled within the required range, achieving global preset performance controllability. Furthermore, the controller designed in this invention exhibits good robustness and fast response capability under disturbances.

[0124] The terminology used in the accompanying drawings is for illustrative purposes only and should not be construed as limiting the scope of this patent.

[0125] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A fixed-time sliding mode control method for a tiltrotor unmanned aerial vehicle with preset performance, characterized in that, Includes the following steps: Construct a motion model for a tiltrotor UAV; build a conversion error based on a preset performance function; and design a fixed-time non-singular terminal sliding surface using adaptive gain. Based on the motion model, the control model is fused with the non-singular terminal sliding surface to construct a control law, and the tilt-rotor UAV is controlled based on the control law. The step of constructing the conversion error based on the preset performance function includes: The tracking error and its boundary are designed based on a preset performance function; The design error transformation function converts the tracking error into an unrestricted error that is not constrained by the initial boundary of the preset performance function; A control model is constructed based on the aforementioned unconstrained error; The error transformation function The expression is as follows: Where sign() is the sign function; ; The initial tracking error is denoted as ; where For conversion error, It is a constant greater than 1; This represents the original error; Preset performance functions for fixed time intervals; The steps for designing a fixed-time sliding mode surface using adaptive gain include: Define a fixed-time sliding surface that includes control parameters and state variables; A non-singular terminal sliding mode function is introduced, and adaptive gain control is applied to the derivative of the sliding mode surface to obtain a non-singular terminal sliding mode surface; the sliding mode surface s The expression is as follows: in, , , and The control parameters to be designed; The derivative expression for the sliding surface is as follows: in, For adaptive control of gain, , , , , , .

2. The fixed-time sliding mode control method for a tiltrotor unmanned aerial vehicle with preset performance according to claim 1, characterized in that, The steps for constructing the mathematical model of the tiltrotor unmanned aerial vehicle include: Construct the position loop model and attitude loop model of the UAV; The six-degree-of-freedom motion equations are obtained based on the position loop model and attitude loop model.

3. A fixed-time sliding mode control method for a tilt-rotor UAV with preset performance according to claim 2, characterized in that, The steps for constructing the UAV's position loop model include: By using a transformation matrix to correlate the velocity in the fuselage coordinate system with the position in the ground coordinate system, the velocity and acceleration of the UAV are modeled. The rotor thrust, aerodynamic force, and gravity within the acceleration are also modeled, resulting in the UAV's position loop model, expressed as follows: in, Let be the position vector of the tiltrotor UAV in the ground coordinate system. This represents the velocity vector of the tiltrotor UAV in the ground coordinate system. This is the transformation matrix from the fuselage coordinate system to the ground coordinate system. Let be the velocity vector of the UAV in the fuselage coordinate system; For acceleration, For the mass of tiltrotor drones, This represents the total perturbation of the position loop. The force generated by the rotor The aerodynamic forces generated by the wings and fuselage To tilt the rotor without human gravity; This is the transformation matrix from the rotor coordinate system to the fuselage coordinate system. The thrust generated by each rotor, These represent the drag, lateral force, and lift experienced by the tiltrotor unmanned aerial vehicle (UAV). For dynamic pressure, air density, These are the drag coefficient, lateral force coefficient, and lift coefficient, respectively. The projected area of ​​the tiltrotor drone. It is the acceleration due to gravity; Ф This refers to the rotor tilt angle.

4. A fixed-time sliding mode control method for a tilt-rotor UAV with preset performance according to claim 2, characterized in that, The steps for constructing the attitude loop model of the UAV include: The attitude angular velocity and attitude angle derivative of the tiltrotor UAV are correlated by a transformation matrix, and the dynamic equation of the attitude angle is constructed. The total torque of the tiltrotor UAV is decomposed, and the torque generated by the rotor and the aerodynamic torque of the wing or fuselage are modeled to obtain the attitude loop model of the UAV, the expression of which is as follows: in, The attitude angle of the tiltrotor unmanned aerial vehicle. For attitude angular velocity, This is the transformation matrix from attitude angular velocity to attitude angular differential; The distance between the rotor blades. The counter-torque generated by the rotor This is the anti-torque coefficient of the rotor. The rotational speed of each rotor. For the wingspan of tiltrotor drones, It is the mean aerodynamic chord length. These are the roll, pitch, and yaw moments, respectively. Ф The rotor tilt angle, For rotational inertia, For the attitude loop total perturbation.

5. A fixed-time sliding mode control method for a tilt-rotor unmanned aerial vehicle with preset performance according to claim 4, characterized in that, The steps for constructing the control law include: Introduce unrestricted error within the sliding surface at a fixed time; Based on the unconstrained error combined with the position loop and attitude loop models, control expressions for position error and attitude error are constructed respectively, and the control law is obtained.

6. A fixed-time sliding mode control system for a tiltrotor unmanned aerial vehicle with preset performance, applied to the fixed-time sliding mode control method for a tiltrotor unmanned aerial vehicle with preset performance as described in any one of claims 1 to 5, characterized in that, The system includes: Control law solving module: It carries a motion model of a tiltrotor UAV; a control model based on preset performance and a non-singular terminal sliding surface; based on the motion model, it merges the control model and the non-singular terminal sliding surface and solves the control law; Unmanned Aerial Vehicle (UAV) Control Module: Controls the tiltrotor UAV based on the aforementioned control law.

7. An electronic 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 fixed-time sliding mode control method for tilt-rotor UAVs with preset performance as described in any one of claims 1 to 5.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the fixed-time sliding mode control method for tilt-rotor UAVs with preset performance as described in any one of claims 1 to 5.

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