Variable structure quadrotor system and control method thereof

Abstract

This invention relates to the field of rotorcraft technology, providing a variable structure quadrotor system and its control method. The system includes: a fuselage; servos, an onboard computer, and several sensors mounted on the fuselage; a first high-position arm, a second high-position arm, a first low-position arm, and a second low-position arm respectively located at the four corners of the fuselage; and a motor at the end of each arm. A height difference exists between the first high-position arm and the first low-position arm, and the two diagonally opposite arms are at the same height. The onboard computer, based on sensor data uploaded from the sensors and the rotation angles of each arm, estimates and compensates for disturbances caused by the rotational motion of each arm using a linearly extended state observer, and controls the speed of each motor. While ensuring stable quadrotor flight, this significantly improves the quadrotor's ability to maneuver in confined spaces, thereby greatly enhancing the quadrotor's adaptability.

Description

Technical Field

[0001] This invention relates to the field of rotorcraft technology, and in particular to a variable structure quadrotor system and its control method. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] A quadcopter is an aircraft capable of performing aviation missions. Due to its advantages such as maneuverability, ease of carrying and storage, ease of learning to operate, vertical takeoff and landing, and self-stabilizing hovering, it is widely used in many fields such as cargo transportation, aerial photography, and agricultural plant protection.

[0004] However, existing quadcopters have high requirements for the flight environment, and their structures are often single and fixed. This is especially true for larger multi-rotor aircraft or those with many rotors. When encountering spaces or obstacles smaller than themselves, they struggle to penetrate confined spaces or traverse obstacles, affecting information acquisition and mission completion. In contrast, variable-structure rotorcraft are more environmentally adaptable. They can change their fuselage structure and size through a morphing mechanism to traverse confined spaces and obstacles, or approach walls, pipes, and other surfaces for more detailed inspections. They can also directly perform other functions such as object grasping and transportation through their morphing structure.

[0005] Based on this, the design and research of a variable structure quadrotor aircraft that can be flexibly applied to complex scenarios and mission environments has high practical application value. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a variable structure quadrotor system and its control method. Based on deformable mechanical structures and variable-morphology flight control strategies, it significantly improves the quadrotor's ability to pass through confined spaces while ensuring stable flight, thereby greatly enhancing the quadrotor's adaptability.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] The first aspect of the present invention provides a variable structure quadrotor system.

[0009] A variable structure quadcopter system includes: a fuselage, a servo motor, an onboard computer and several sensors mounted on the fuselage, a first high-position arm, a second high-position arm, a first low-position arm and a second low-position arm respectively mounted on the four corners of the fuselage, a motor mounted at the end of each arm, and a propeller connected to the motor.

[0010] The first high-position arm and the second high-position arm are located on the same diagonal line, the first low-position arm and the second low-position arm are located on the same diagonal line, and there is a height difference between the first high-position arm and the first low-position arm. The two arms on the diagonal line are at the same height.

[0011] The first high-position arm, the second high-position arm, the first low-position arm, and the second low-position arm are connected to the fuselage via different servo motors and achieve horizontal rotation under the drive of the servo motors.

[0012] The onboard computer estimates and compensates for the disturbances caused by the rotational motion of each arm based on the rotation angle of each arm and data uploaded by several sensors, and controls the speed of each motor through a linear extended state observer.

[0013] Furthermore, the sensors include accelerometers, magnetometers, gyroscopes, barometers, GPS devices, and cameras;

[0014] The sensor data includes triaxial angular velocity, attitude, altitude, positioning information, and environmental information.

[0015] Furthermore, the onboard computer is connected to each servo motor via a servo motor drive board;

[0016] The servo drive board receives the rotation angle sent by the onboard computer, outputs a pulse width modulation signal to the servo, and adjusts the power supply voltage to the rated voltage for servo operation.

[0017] Furthermore, the onboard computer is connected to each motor via a flight controller and an electronic speed controller;

[0018] The flight controller receives control signals from the onboard computer and converts them into pulse width modulation signals for the electronic speed controller.

[0019] Furthermore, the flight controller and onboard computer are fixed to the upper frame of the fuselage;

[0020] The electronic speed controller is fixed on the middle frame of the machine body.

[0021] Furthermore, the upper frame is fixed to the middle frame by aluminum pillars and screws.

[0022] Furthermore, the electronic speed controller receives the pulse width modulation signal from the flight controller and converts the power supply voltage into three-phase winding voltage, thereby driving the motor to generate the corresponding speed.

[0023] Furthermore, the power supply is fixed to the bottom frame via nylon straps and strap slots on the bottom frame of the machine body.

[0024] Furthermore, landing gear is provided below the first high-position arm, the second high-position arm, the first low-position arm, and the second low-position arm.

[0025] The second aspect of this invention provides a control method for a variable structure quadrotor system, applied to the variable structure quadrotor system described in the first aspect of this invention, comprising the following steps:

[0026] Based on sensor data uploaded by several types of sensors and the rotation angle of each arm, the disturbance caused by the rotational motion of each arm is estimated and compensated by a linear expansion state observer, thereby controlling the speed of each motor.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] 1. The variable structure quadrotor system described in this invention is based on deformable mechanical structure, deformable drive hardware circuit and deformable flight control strategy. While ensuring stable flight of the quadrotor, it significantly improves the quadrotor's ability to pass through narrow spaces, thereby greatly improving the adaptability of the quadrotor and having broad application prospects.

[0029] 2. The variable structure quadcopter system described in this invention uses a designed linear expansion state observer to estimate and compensate for disturbances caused by deformation during flight, thereby ensuring flight stability. Attached Figure Description

[0030] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0031] Figure 1(a) is an overall structural diagram of the variable structure quadrotor system provided in Embodiment 1 of the present invention;

[0032] Figure 1(b) is a first-view view of a portion of the structure of the variable structure quadrotor system provided in Embodiment 1 of the present invention;

[0033] Figure 1(c) is a second-view view of a portion of the structure of the variable structure quadrotor system provided in Embodiment 1 of the present invention;

[0034] Figure 2 This is a schematic diagram of the deformation of the variable structure quadrotor system provided in Embodiment 1 of the present invention;

[0035] Figure 3 This is a schematic diagram of the software structure provided in Embodiment 1 of the present invention;

[0036] Figure 4 This is a schematic diagram of the modified hardware circuit connection and communication provided in Embodiment 1 of the present invention;

[0037] Figure 5This is a control block diagram of the variable structure quadrotor system provided in Embodiment 2 of the present invention;

[0038] Figure 6 This is a schematic diagram of the first modified function provided in Embodiment 2 of the present invention;

[0039] Figure 7 This is a schematic diagram of the second modified function provided in Embodiment 2 of the present invention. Detailed Implementation

[0040] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0041] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0042] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0043] Where there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0044] Example 1

[0045] As shown in Figures 1(a), 1(b) and 1(c), Embodiment 1 of the present invention provides a variable structure quadrotor system, including a fuselage, deformable hardware circuitry and servo-driven deformable arms.

[0046] The servo-driven deformable arm consists of a first high-position arm 1, a second high-position arm 2, a first low-position arm 3, a second low-position arm 4, a pivot 8, a spacer 9, a cross arm 10, a servo motor 11, etc.; the fuselage is composed of a bottom frame 5, a middle frame 6, and an upper frame 7.

[0047] The bottom frame 5 has a strap slot 16, and the power supply is fixed to the bottom frame 5 via nylon straps. While effectively ensuring power supply, it significantly lowers the center of gravity of the quadcopter, thereby improving flight stability.

[0048] The middle rack 6 is fixed to the bottom rack 5 by aluminum pillars and screws. The ESC 17 and the power management board are placed on the middle rack 6. The ESC is used to receive the pulse width modulation signal output by the flight controller and control the motor speed. The power management board is used in conjunction with the flight controller. It is equipped with voltage regulation and protection circuits, provides power to the flight controller, and provides ports for connecting the flight controller to the hardware circuits of various modules, facilitating wiring connections and layout.

[0049] The upper frame 7 is fixed to the middle frame 6 via aluminum pillars and screws. The flight controller and onboard computer are also fixed to the upper frame 7 via aluminum pillars and screws. The flight controller can output pulse-width modulation signals to the electronic speed controller and can receive control signals from the onboard computer, converting them into motor speeds. It also integrates a barometer, gyroscope, magnetometer, and accelerometer, and can connect to an external GPS module, enabling it to read and process sensor data. The onboard computer calculates the proposed control method, receives sensor data transmitted from the flight controller, and sends control signals and servo angle change commands to the flight controller and servo drive boards respectively. Furthermore, it connects to a camera and can read image data from the camera.

[0050] There is a height difference between the first high-position arm 1, the second high-position arm 2 and the first low-position arm 3, the second low-position arm 4. The first high-position arm 1, the second high-position arm 2, the first low-position arm 3 and the second low-position arm 4 are respectively installed on the four corners of the fuselage. The first high-position arm 1 and the second high-position arm 2 are located on the same diagonal line, and the first low-position arm 3 and the second low-position arm 4 are located on the same diagonal line. The two arms on the diagonal line are of the same type and are located at the same height to prevent the propellers 18 between the arms from interfering with each other due to deformation.

[0051] Servo slots 19 are provided at the four corners of the bottom frame 5, and servos 11 are placed inside the servo slots 19 of the bottom frame 5. The first high-position arm 1, the second high-position arm 2, the first low-position arm 3 and the second low-position arm 4 are each provided with a motor mount 20 at one end and an upper mounting base and a lower mounting base at the other end. The servo slots 19 are located between the upper mounting base and the lower mounting base. The cross arm 10 is placed in the cross arm groove of the upper mounting base of the first high-position arm 1, the second high-position arm 2, the first low-position arm 3, and the second low-position arm 4. Each arm is connected to the cross arm 10 and the servo motor 11 by screws. The rotating shaft 8 and the spacer 9 are located below each arm. The lower mounting base has holes. The spacer 9 is fitted onto the rotating shaft 8. The rotating shaft 8 is inserted into the servo motor groove 19 of the bottom frame 5 through the holes below each arm. The rotating shaft 8, the spacer 9, the first high-position arm 1, the second high-position arm 2, the first low-position arm 3, and the second low-position arm 4 are connected to the bottom frame 5 by screws and nuts. Specifically, a hole is provided below the servo slot, and a spacer 9 is fitted onto the rotating shaft 8; the rotating shaft 8 serves as the rotating shaft at the lower end of the first high-position arm 1, the second high-position arm 2, the first low-position arm 3, and the second low-position arm 4, and has screws on both the top and bottom; the upper part of the rotating shaft 8 is inserted into the servo slot 19 of the bottom frame 5 and fixed with a nut, and when connected to the first high-position arm 1, the second high-position arm 2, the first low-position arm 3, and the second low-position arm 4, the lower part is fixed with a nut.

[0052] The deformable arms can rotate horizontally under the drive of servo motors. All four deformable arms can move simultaneously under the drive of servo motors, thus realizing the transformation function of the quadcopter.

[0053] The propeller 18 is fixed to the rotating shaft of the first motor 12, the second motor 13, the third motor 14, and the fourth motor 15 by nuts. The first motor 12 is fixed to the motor base 20 of the first high-position arm 1 by screws. The second motor 13 is fixed to the motor base 20 of the second high-position arm 2 by screws. The third motor 14 is fixed to the motor base 20 of the first low-position arm 3 by screws. The fourth motor 15 is fixed to the motor base 20 of the second low-position arm 4 by screws.

[0054] Landing supports 21 are provided below the first high-position arm 1, the second high-position arm 2, the first low-position arm 3, and the second low-position arm 4. The landing supports 21 are used to ensure the stability of the quadcopter during takeoff and landing.

[0055] When the control circuit sends a control signal to the servo motor 11, the servo motor can rotate, thereby driving the arm to rotate in the horizontal direction, realizing the structural change of the quadcopter.

[0056] like Figure 2As shown, the angle variation range of each arm is between -45° and 45°. The initial position of each arm of the variable structure quadcopter is at 0°, which can be regarded as an X-shape. When the quadcopter is in the X-shape, the wheelbase is 280mm, that is, the distance from the center of the first motor 12 to the center of the second motor 13 is 280mm, the distance from the center of the third motor 14 to the center of the fourth motor 15 is 280mm, and the height from the landing gear 21 to the top of the fuselage is 180mm. The entire quadcopter has a centrally symmetrical structure. The variable structure quadcopter is in... Figure 2 In the configuration shown, the first high-position arm 1 changes angle by 45°, the second high-position arm 2 changes angle by 45°, the first low-position arm 3 changes angle by 45°, and the second low-position arm 4 changes angle by 45°.

[0057] like Figure 3 As shown, the modified hardware circuit of the present invention consists of a power supply, a power system, and a control system.

[0058] The power source is a lithium polymer battery (model aircraft lithium battery), installed on the lower frame, which provides the energy consumed for the aircraft to fly.

[0059] like Figure 4 As shown, the power system of this invention consists of servos, servo drive boards, power management boards, four electronic speed controllers (ESCs 17), four propellers, and four brushless DC motors. The servos and servo drive boards are mounted on the bottom frame, the power management boards and ESCs are mounted on the middle frame, and the propellers are mounted on the brushless DC motors. The servo drive boards receive rotation angle commands from the onboard computer, output pulse-width modulation (PWM) signals to the servos, and adjust the power supply voltage to the rated voltage for servo operation. Upon receiving the signal, the servos drive the arms to rotate to the specified angle. The power management board is the hub for aircraft wiring connections, providing connection interfaces for the flight controller and connecting these interfaces to corresponding modules. It also adjusts the power supply voltage to the flight controller's operating voltage, thus powering the flight controller. The ESCs receive PWM signals from the flight controller, converting the battery's DC voltage into three-phase winding voltage, thereby driving the brushless DC motors to rotate. The rotation of the brushless DC motor rotors drives the propellers to rotate synchronously, and the propellers push air to generate lift.

[0060] The control system of this invention consists of a flight controller and an onboard computer, which are mounted on the upper rack. The flight controller integrates a main processor and an I / O processor for inputting / outputting data and managing the operation of the underlying control system. When it receives control signals from the onboard computer, it converts them into pulse-width modulation (PWM) signals for the electronic speed controller.

[0061] In addition, it is equipped with an accelerometer, magnetometer, gyroscope, barometer, and GPS. The accelerometer, magnetometer, and gyroscope measure the three-axis angular velocity and attitude of the aircraft through data fusion; the barometer can determine the altitude information of the aircraft; the GPS can realize the positioning of the aircraft; the flight controller is connected to the onboard computer via USB, and the onboard computer can read the sensor data of the aircraft (including three-axis angular velocity, attitude, altitude, and positioning information), run the control method proposed in this patent, output control quantities to the flight controller, and adjust the control allocation strategy in real time to enable the variable structure quadcopter to fly stably.

[0062] The aircraft can carry sensors such as depth cameras and connect to an onboard computer. Real-time environmental information is acquired by these sensors and transmitted to the onboard computer, which then uses intelligent image algorithms to detect spatial volume, obstacle size, and distance in real time. Flight control is achieved using designed control algorithms, and the aircraft can also be remotely controlled manually to deform and traverse obstacles. The variable-structure quadcopter can perform missions in enclosed spaces or open environments with a minimum length greater than 300mm, a minimum width greater than 300mm, and a minimum height greater than 1000mm.

[0063] During normal flight, the quadcopter maintains its original traditional X-shaped structure. Its motor drives the propeller to rotate and generate lift to achieve flight. When encountering spaces or obstacles smaller than itself, it can use servo motors to drive the arms to rotate horizontally to reduce its size and maintain stable flight, passing through narrow spaces and obstacles.

[0064] This embodiment provides a variable structure quadrotor system, which, based on deformable mechanical structures, deformable drive hardware circuits, and deformable flight control strategies, significantly improves the quadrotor's ability to pass through confined spaces while ensuring stable flight, thereby greatly enhancing the quadrotor's adaptability and having broad application prospects.

[0065] Example 2

[0066] Embodiment 2 of the present invention provides a control method for a variable structure quadrotor system, which is applied to the variable structure quadrotor system described in Embodiment 1. By using a designed Linear Extended State Observer (LESO) to estimate and compensate for the disturbances caused by deformation during flight, the method can estimate and compensate for the changes in physical parameters such as the moment of inertia of each attitude channel during deformation (which can be regarded as internal disturbances of the system), thereby ensuring the stability of the variable structure quadrotor during flight and structural changes.

[0067] like Figure 5As shown, the process includes the following steps: acquiring data uploaded by each sensor, calculating the error between the aircraft's state variables and the reference input, and inputting the control quantity and system state to the extended state observer; inputting the error to the PID controller and combining it with the output of the extended state observer to obtain the controller output; and calculating the speed of each motor by passing the controller output through the control allocation matrix based on the rotation angle of each arm.

[0068] The dynamic model of the position and attitude channels during quadrotor flight is as follows:

[0069]

[0070] Where x represents the state of the system. The derivative represents the system state, w represents the unmodeled dynamics and internal disturbances of the system, d represents the external disturbances, f represents the lumped disturbances of the internal and external systems, b is the control input parameter, and u is the input quantity.

[0071] Based on the above dynamic model, it can be rewritten by adding an expansion state term, and its specific expression is as follows:

[0072]

[0073] Where x1 represents the system state, x2 represents the first derivative of the system state, and x3 represents the lumped disturbance, which includes the effects of structural changes in the quadrotor body. This represents the derivative of the lumped perturbation.

[0074] The formula can be rewritten as a state-space expression, and its specific form is as follows:

[0075]

[0076] in, C = [1 0 0].

[0077] Based on the construction process of the Romberg observer, an observer is constructed for the system with the added extended state term, and its specific expression is as follows:

[0078]

[0079] Where z is an estimate of the system state x.

[0080] Expanding on this, the specific expression of the Linear Extended State Observer (LESO) for the variable structure quadrotor design is as follows:

[0081]

[0082] Where z1 represents the system state estimate, z2 represents the estimate of the first derivative of the system state, z3 represents the estimate of the lumped disturbances experienced by the system, and β1, β2, and β3 are the parameters of the Linear Extended State Observer (LESO).

[0083] Based on the established Linear State Observer (LESO) and its estimated lumped disturbance z3, the specific form of the PID controller is designed as follows:

[0084]

[0085] Where e(t) represents the error between the current state and the reference input r. It is the derivative of the error. It is the integral of the error, k p k i k d These are the controller parameters. The states include the aircraft's attitude, position, altitude, angular velocity, and speed. Attitude and angular velocity are measured by a gyroscope, magnetometer, and accelerometer, and are obtained by fusing these measurements using an information fusion algorithm. Altitude is measured by a barometer, position by GPS, and speed by a combination of GPS and accelerometer measurements. The spatial volume, obstacle size, and distance mentioned earlier are identified and obtained by cameras and onboard computers. Based on this, visual positioning and motion planning can be implemented in the future to enhance the aircraft's autonomous movement capabilities.

[0086] like Figure 5 As shown, the control quantity u = [fτ] is obtained. x τ y τ z After that, where f is the total lift and τ is the total lift. x τ y τ z These are the torques required for the quadcopter's x, y, and z axes, respectively. The obtained force and torque control quantities *u* need to be converted into actual actuator speeds through control allocation. The specific conversion method is as follows:

[0087]

[0088] In the above formula, the 4*4 matrix is ​​the control allocation matrix, c t c m These are the lift coefficient and torque coefficient, where ω1, ω2, ω3, and ω4 are the speeds of the first, second, third, and fourth motors, respectively. For example... Figure 2 As shown, L 1x L 1y L is the lever arm length of the first motor relative to the x-axis and y-axis of the machine coordinate system. 2x L 2yL is the lever arm length of the second motor relative to the x-axis and y-axis of the machine coordinate system. 3x L 3y It is the lever arm length of the third motor relative to the x-axis and y-axis of the machine coordinate system; L 4x L 4y This refers to the lever arm length of the fourth motor relative to the x-axis and y-axis of the aircraft coordinate system. Due to the rotation of the aircraft arms, the lever arm lengths of each motor relative to the x-axis and y-axis vary, and can be calculated based on the rotation angle of the aircraft arms and the center of gravity. The control inputs of the servos are obtained by sending commands from the onboard computer, and their values ​​depend on the aircraft operator or the autonomous planning algorithm, which flexibly sets them within a certain range based on the environment and obstacles.

[0089] like Figure 4 As shown, after calculating the lever arm lengths of each motor to the x and y axes after the arm rotates, the calculated values ​​are transmitted to the control distribution unit in the flight controller using the flight controller's own uORB communication mechanism. After obtaining the control quantity u, it is input into the control distribution unit, causing the flight controller to generate the correct pulse width modulation signal, which is sent to the electronic speed controller via the power management board. The electronic speed controller receives the pulse width modulation signal from the flight controller and drives the brushless DC motor to generate the correct speed, ensuring the stability of the variable structure quadcopter during deformation.

[0090] For example, during hovering, a quadcopter in an X-shape needs to ensure that the four motors rotate at the same speed, that is, the forces generated by the four motors are the same and equal in magnitude and opposite in direction to other external forces acting on the quadcopter, in order to ensure stable hovering.

[0091] like Figure 6 As shown, when the variable structure quadcopter is in Figure 6 In the configuration shown, the first high-position arm 1 changes angles of 45°, the second high-position arm 2 changes angles of 45°, the first low-position arm 3 changes angles of -45°, and the second low-position arm 4 changes angles of -45°. Since the aircraft remains in a centrally symmetrical state, according to the control process and method, the rotational speeds of the four motors do not need to change. That is, stable hovering can only be guaranteed when the forces generated by the four motors are the same and equal in magnitude and opposite in direction to other external forces acting on the quadcopter. This variable-structure quadcopter can effectively reduce its size, allowing it to penetrate confined spaces or traverse obstacles to complete information acquisition tasks.

[0092] like Figure 7 As shown, when the variable structure quadcopter is in Figure 7In the configuration shown, the first high-position arm 1 has an angle change of 0°, the second high-position arm 2 has an angle change of -45°, the first low-position arm 3 has an angle change of 0°, and the second low-position arm 4 has an angle change of 45°. According to the control process and method, stable hovering can only be guaranteed when the speeds of the second and third motors are increased to be equal, the speeds of the first and fourth motors are decreased to be equal, and the forces generated by the four motors are equal in magnitude and opposite in direction to other external forces acting on the quadcopter. At this point, the variable-structure quadcopter can effectively reduce the distance between the arms and the object being observed, and can carry sensors such as cameras, thus allowing it to approach walls, pipes, etc., to complete more detailed inspection work.

[0093] The control approach for transformation processes into other forms is the same as the control methods described above.

[0094] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A variable structure quadrotor system, characterized in that: include: The fuselage includes servo motors, an onboard computer, and several sensors mounted on the fuselage; a first high-position arm, a second high-position arm, a first low-position arm, and a second low-position arm respectively mounted at the four corners of the fuselage; a motor mounted at the end of each arm; and a propeller connected to the motor. The first high-position arm and the second high-position arm are located on the same diagonal line, the first low-position arm and the second low-position arm are located on the same diagonal line, and there is a height difference between the first high-position arm and the first low-position arm. The two arms on the diagonal line are at the same height. The first high-position arm, the second high-position arm, the first low-position arm, and the second low-position arm are connected to the fuselage via different servo motors and achieve horizontal rotation under the drive of the servo motors. The onboard computer, based on sensor data uploaded by several sensors and the rotation angles of each arm, estimates and compensates for disturbances caused by the rotational motion of each arm through a linear extended state observer, and controls the speed of each motor. This includes the following steps: acquiring data uploaded by each sensor, calculating the error between the aircraft's state variables and the reference input, and inputting the control quantity and system state to the extended state observer; inputting the error to the PID controller and combining it with the output of the extended state observer to obtain the controller output; and calculating the speed of each motor by applying the controller output to the control assignment matrix based on the rotation angles of each arm. The servo drive board receives the rotation angle command sent by the onboard computer, outputs a pulse width modulation signal to the servo, and adjusts the power supply voltage to the rated voltage for servo operation; after receiving the signal, the servo drives the arm to rotate to the specified angle; the angle variation range of each arm is between -45° and 45°. The linear expansion state observer estimates and compensates for disturbances caused by deformation during flight, estimating and compensating for changes in physical parameters of each attitude channel during deformation to ensure the stability of the variable structure quadrotor during flight and structural changes. The specific expression of the linear expansion state observer is as follows: ； Based on the established linear state observer and its estimated lumped disturbance The specific form of the PID controller design is as follows: ； in, To control the input parameters, For input quantity, This represents the state estimate of the system. This represents an estimate of the first derivative of the system state. This represents an estimate of the lumped disturbance experienced by the system, which includes the effects of structural changes to the quadrotor itself. , , These are the parameters of the linearly extended state observer; Represents the current state and reference input The error between them It is the derivative of the error. It is the integral of the error. , , These are the controller parameters. y For output quantity; The obtained control quantities at the force and torque levels The control allocation is converted into the actual actuator speed, and the specific conversion method is as follows: ； in, It is total lift. , , They are quadcopters axis, axis, The torque required for the shaft is determined by the 4x4 matrix in the above formula, which serves as the control and allocation matrix. , These are the lift coefficient and torque coefficient. , , , These are the rotational speeds of the first motor, the second motor, the third motor, and the fourth motor, respectively. , The first motor is relative to the machine body coordinate system axis, The length of the lever arm of the shaft; , The second motor is relative to the machine body coordinate system. axis, The length of the lever arm of the shaft; , The third motor is relative to the machine body coordinate system. axis, The length of the lever arm of the shaft; , The fourth motor is relative to the machine body coordinate system. axis, The length of the lever arm of the shaft.

2. The variable structure quadrotor system as described in claim 1, characterized in that: The sensors include accelerometers, magnetometers, gyroscopes, barometers, GPS devices, and cameras; The sensor data includes triaxial angular velocity, attitude, altitude, positioning information, and environmental information.

3. The variable structure quadrotor system as described in claim 1, characterized in that: The onboard computer is connected to each servo via a servo drive board.

4. The variable structure quadrotor system as described in claim 1, characterized in that: The onboard computer is connected to each motor via a flight controller and an electronic speed controller. The flight controller receives control signals from the onboard computer and converts them into pulse width modulation signals for the electronic speed controller.

5. The variable structure quadrotor system as described in claim 4, characterized in that: The flight controller and onboard computer are fixed to the upper frame of the fuselage; The electronic speed controller is fixed on the middle frame of the machine body.

6. The variable structure quadrotor system as described in claim 5, characterized in that: The upper frame is fixed to the middle frame by aluminum pillars and screws.

7. The variable structure quadrotor system as described in claim 5, characterized in that: The electronic speed controller receives the pulse width modulation signal from the flight controller and converts the power supply voltage into three-phase winding voltage, thereby driving the motor to generate the correct speed.

8. The variable structure quadrotor system as described in claim 7, characterized in that: The power supply is fixed to the bottom frame via nylon straps and strap slots on the bottom frame of the machine body.

9. The variable structure quadrotor system as described in claim 1, characterized in that: The first high-position arm, the second high-position arm, the first low-position arm, and the second low-position arm are all equipped with landing gear.

10. A control method for a variable structure quadrotor system, characterized in that: Applied to the variable structure quadrotor system as described in any one of claims 1-9, the method includes the following steps: Based on sensor data uploaded by several sensors and the rotation angle of each arm, a linear extended state observer is used to estimate and compensate for the disturbances caused by the rotational motion of each arm, and to control the speed of each motor. The steps include: acquiring data uploaded by each sensor, calculating the error between the aircraft's state variables and the reference input, and inputting the control quantity and system state into the extended state observer; inputting the error into the PID controller and combining it with the output of the extended state observer to obtain the controller output; and calculating the speed of each motor by passing the controller output through a control assignment matrix based on the rotation angle of each arm. The servo drive board receives the rotation angle command sent by the onboard computer, outputs a pulse width modulation signal to the servo, and adjusts the power supply voltage to the rated voltage for servo operation; after receiving the signal, the servo drives the arm to rotate to the specified angle; the angle variation range of each arm is between -45° and 45°. The linearly extended state observer is specifically expressed as follows: ； Based on the established linear state observer and its estimated lumped disturbance The specific form of the PID controller design is as follows: ； in, To control the input parameters, For input quantity, This represents the state estimate of the system. This represents an estimate of the first derivative of the system state. This represents an estimate of the lumped disturbance experienced by the system, which includes the effects of structural changes to the quadrotor itself. , , These are the parameters of the linearly extended state observer; Represents the current state and reference input The error between them It is the derivative of the error. It is the integral of the error. , , These are the controller parameters. y For output quantity; The obtained control quantities at the force and torque levels The control allocation is converted into the actual actuator speed, and the specific conversion method is as follows: ； in, It is total lift. , , They are quadcopters axis, axis, The torque required for the shaft is determined by the 4x4 matrix in the above formula, which serves as the control and allocation matrix. , These are the lift coefficient and torque coefficient. , , , These are the rotational speeds of the first motor, the second motor, the third motor, and the fourth motor, respectively. , The first motor is relative to the machine body coordinate system axis, The length of the lever arm of the shaft; , The second motor is relative to the machine body coordinate system. axis, The length of the lever arm of the shaft; , The third motor is relative to the machine body coordinate system. axis, The length of the lever arm of the shaft; , The fourth motor is relative to the machine body coordinate system. axis, The length of the lever arm of the shaft.

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