Small tail seat type double-wing four-motor unmanned aerial vehicle and control method

Abstract

This invention relates to a small tail-seat biplane quadrotor unmanned aerial vehicle (UAV) and its control method. It includes a fixed-wing mechanism for level flight and a rotor system for vertical takeoff and landing (VTOL). The fixed-wing mechanism comprises two fixed wings connected by a connecting mechanism. Rotor systems are symmetrically arranged on both sides of the upper end of each fixed wing, and landing gear is located at the bottom of each fixed wing. A housing is located on the upper part of the connecting mechanism, and a control module is housed within the housing. The control module includes an MCU chip and a detection unit. The biplane quadrotor UAV of this invention possesses high flight efficiency, large payload capacity, and good maneuverability. It combines the advantages of both fixed-wing and multi-rotor UAVs, utilizing the multi-rotor for VTOL, thus solving the site requirements of fixed-wing UAVs, and using the fixed wings to enable level flight, effectively extending endurance.

Description

Technical Field

[0001] This invention belongs to the field of aerial unmanned robot control, specifically relating to a small tail-seat biplane quadcopter UAV and its control method. Background Technology

[0002] Due to their advantages such as small size, low cost, and ease of use, and with the progress of the times and the rapid development of technology, the performance of drones is constantly improving and the types are increasing, leading to a growing demand for their application in both military and civilian fields. In order to meet the higher demands of the military and civilian sectors for drones in the new era, more and more companies and research institutions are beginning to develop new types of drones.

[0003] Drones are generally divided into fixed-wing drones and rotary-wing drones. Technically, fixed-wing drones rely on engines to generate thrust, enabling them to fly at high speeds. They also utilize aerodynamics to generate lift, overcoming their own weight. There is a positive correlation between aerodynamics and speed; the higher the speed, the greater the aerodynamics. However, the engine cannot generate thrust perpendicular to the drone's axis, limiting their flight to horizontal. Furthermore, speed changes require time, necessitating long runways to reach a specific speed. Rotary-wing drones, on the other hand, use aerodynamics to rotate their rotors around their own axis. This rotation generates lift through relative motion with the air. Rotary-wing drones do not require horizontal speed for takeoff, overcoming the runway dependence of fixed-wing drones. However, because the rotor primarily provides lift, the horizontal thrust parallel to the fuselage axis is relatively small, resulting in slower horizontal flight speeds. Additionally, battery limitations limit their flight time.

[0004] Vertical takeoff and landing (VTOL) fixed-wing UAVs encompass two main characteristics: the aerodynamic layout of the fixed wing itself and the method of vertical takeoff and landing. However, the deflection angle of the control surfaces and the resulting control force are not linearly related, which poses certain challenges to the stability and control of the UAVs.

[0005] For example, a tail-seat vertical takeoff and landing fixed-wing UAV disclosed in patent document CN202111057558 includes a fuselage, wings, takeoff and landing drive assembly, cruise drive assembly and tail assembly. The main rotor is used to provide lift for takeoff and hovering of the fuselage, the auxiliary rotor is used to provide thrust for level flight of the fuselage, and the auxiliary rotor is also used to provide pitch force for takeoff and landing of the fuselage. However, this design makes the UAV too complicated, and the main rotor and auxiliary rotor of the UAV will generate aerodynamic interference, which is not conducive to the control of the UAV's attitude changes in the air. Summary of the Invention

[0006] To address the issues of poor controllability and flight stability in existing fixed-wing and rotary-wing UAVs, this invention provides a small tail-seat biplane quadcopter UAV and its control method. It combines the advantages of both fixed-wing and multi-rotor UAVs, utilizing the multi-rotor for vertical takeoff and landing, thus eliminating the site requirements of fixed-wing UAVs. The fixed-wing design enables the UAV to fly level in the air, effectively extending its endurance. Furthermore, the dual-loop control method improves the flight stability of the UAV, allowing it to perform flight missions in the desired attitude.

[0007] To achieve the above objectives, a first aspect of the present invention provides a small tail-seat biplane quadrotor unmanned aerial vehicle (UAV), comprising a fixed-wing mechanism for level flight and a rotor device for vertical takeoff and landing. The fixed-wing mechanism includes two fixed wings with internal cavities, arranged parallel to each other, and a connecting mechanism between them, fixing the two fixed wings together. Rotor devices are symmetrically arranged on both sides of the upper end of each fixed wing, and landing gear is provided at the bottom end of each fixed wing, corresponding to the rotor devices. A housing is provided on the upper part of the connecting mechanism, and a control module is disposed within the housing. The control module includes an MCU chip and a detection unit. The detection unit is used to detect the aircraft's attitude, and its output is connected to the input of the MCU chip. The output of the MCU chip is connected to a servo motor. The servo drive module is connected to the MCU chip via a remote control. The servo drive module drives the rotor device. The fixed wing includes a straight wing and two side wings, symmetrically arranged on both sides of the straight wing. The straight wing and the two side wings, when combined, form a curved structure that gradually tapers from the front to the rear. A cavity is provided inside the straight wing, and a connecting mechanism is located in the middle of the straight wing. The connecting mechanism includes a connecting part, a rigid connecting tube, and two flexible connecting tubes. The connecting part is an inverted mountain-shaped plate structure, and its vertical section is detachably connected to the straight wing. For each of the two fixed wings, there are two connecting parts. The middle of the horizontal sections of the two connecting parts is fixed to both ends of the rigid connecting tube, and flexible connecting tubes are symmetrically arranged at the edges of the horizontal sections, with both ends of the flexible connecting tubes fixed to the two connecting parts.

[0008] Furthermore, a housing is fixedly installed in the middle of the rigid connecting pipe. The housing is a hollow square structure, and a servo drive module and a control module are installed inside the housing. The housing is fixed to the rigid connecting pipe.

[0009] Furthermore, the inner cavity of the straight wing is provided with a fixed platform, which is a U-shaped plate. The bottom surface of the fixed platform is fixed to the straight wing. An energy module and two battery slots are provided on the inner side of the fixed platform. The battery slots are arc-shaped structures made of flexible material, and the two battery slots are symmetrically arranged. A square notch is opened on the side wall of the fixed platform near the connecting part. The vertical section of the connecting part corresponding to the square notch enters the inner cavity of the straight wing and engages with the square notch.

[0010] Furthermore, the servo drive module includes a servo motor, and the rotor device includes a rotor and a fixed frame. The fixed frame has a stepped cylindrical structure, with one side of the fixed frame fixed to the output shaft of the servo motor and the other side fixed to the rotor.

[0011] Furthermore, the landing gear has a trapezoidal sheet structure, and the landing gear and the straight wing are an integrated structure.

[0012] Furthermore, the control module is equipped with a position loop controller and an attitude loop controller, and the detection unit includes a gyroscope sensor, an accelerometer sensor, an ultrasonic sensor, a barometric pressure sensor, and a GPS module.

[0013] The biplane structure combines the advantages of fixed-wing drones—high speed, high altitude, and long endurance—with the space limitations required for takeoff and landing, and the inability to hover. To address the limitations of fixed-wing drones in terms of takeoff and landing space and hovering ability, a quadcopter structure is incorporated, enabling vertical takeoff, landing, and hovering. During vertical takeoff and landing, the quadcopter structure generates upward lift or forward thrust. Upon reaching the predetermined altitude, the rotors tilt the entire drone forward around its wing axis, gradually increasing the horizontal thrust. This, combined with the other two rotors, maintains altitude and provides forward velocity. Once the flight speed reaches the requirements for fixed-wing flight, the rotors return to a horizontal position, and the drone enters fixed-wing mode, significantly increasing speed, range, and loiter time. The landing phase is similar to takeoff. Upon reaching the landing area, the drone decelerates, and the rotors gradually shift from horizontal to vertical, transitioning to multi-rotor mode for a vertical landing.

[0014] For single-wing, dual-rotor drones, the attitude in the air is difficult to control, making them prone to crashing. In contrast, dual-fixed-wing, quadcopter drones offer better stability and are easier to control in the air, exhibiting better robustness during mode transitions. During transition modes, torque can easily be generated in the middle of the dual-fixed-wing configuration; flexible connecting tubes can prevent the aircraft from disintegrating in mid-air, improving flight stability. The detachable structure makes the drone easy to carry, and its simple design ensures reliable connections and convenient assembly and disassembly.

[0015] The second aspect of the present invention provides a control method for a small tail-seat biplane quadcopter unmanned aerial vehicle, comprising: Step 1: inputting a takeoff command and desired motion attitude into a remote controller; Step 2: The aircraft attitude is detected by the detection unit, and the servo drive module is activated by the control module to operate the rotor device, causing the aircraft to rise vertically. Step 3: Input the real-time detected current body attitude into the attitude loop controller, complete the body attitude adjustment calculation through the position loop controller and attitude loop controller, and output the adjustment signal to the servo drive module; Step 4: The servo drive module adjusts the rotor device to put the aircraft in the desired motion attitude, and the aircraft changes from the transition mode to the level flight mode; Step 5: The detection unit detects the body's posture and transmits the posture parameters to the remote controller. The remote controller compares and analyzes the adjusted posture parameters with the desired motion posture to confirm whether the body has achieved the desired motion posture. If the desired flight posture is achieved, a signal indicating completion of the predetermined flight mission will be sent via the remote controller. If the desired motion posture is not achieved, a landing command is issued via remote control, and the servo drive module drives the rotor to complete the landing.

[0016] Furthermore, the position loop controller is used to track the desired position of the UAV and to generate angular velocity commands. The position loop controller transmits the angular velocity commands to the attitude loop controller, which tracks the angular velocity commands. The position loop controller uses integral sliding mode control, where the integral term is used to eliminate steady-state and static errors caused by aerodynamic influences. The attitude loop controller uses backstepping sliding mode control.

[0017] Furthermore, the small tail-seat biplane quadcopter UAV has three transformation modes: quadcopter mode, transition mode, and horizontal flight mode; the attitude parameters mentioned in step 2 include the attitude information, speed information, and acceleration information of the UAV measured by the gyroscope sensor, accelerometer, ultrasonic sensor, barometer, and GPS module; the motion tasks mentioned in step 3 include three-dimensional spatial rotational motion in the roll, pitch, and yaw directions.

[0018] The beneficial effects of the present invention through the above technical solution are as follows: 1. The small tail-mounted biplane quadcopter UAV of the present invention combines the features of fixed-wing UAVs and rotary-wing UAVs. At the same time, the energy module and control module are set inside the dual fixed-wing mechanism, which effectively improves the space utilization of the UAV and reduces the weight of the UAV, overcoming the problems of the existing UAVs having low site requirements or slow horizontal flight speed.

[0019] 2. The dual-ring sliding mode variable structure controller designed in this invention, combined with a servo drive module, enables the small tail-seat biplane quadrotor UAV to remain invariant under parameter disturbances and external wind interference, exhibiting advantages such as simple control structure and good robustness. The dual-ring sliding mode variable structure controller can effectively achieve tracking control of the desired motion position and attitude, demonstrating accurate control performance. Attached Figure Description

[0020] Figure 1 This is one of the structural schematic diagrams of a small tail-mounted biplane quadcopter unmanned aerial vehicle of the present invention; Figure 2 This is the second structural schematic diagram of a small tail-mounted biplane quadcopter UAV according to the present invention; Figure 3 This is the third structural schematic diagram of a small tail-mounted biplane quadcopter UAV according to the present invention; Figure 4 This is a flowchart of a small tail-seat biplane quadcopter UAV and its control method according to the present invention; Figure 5 This is a system principle block diagram of a small tail-mounted biplane quadcopter UAV and its control method according to the present invention.

[0021] Reference numerals: 1 is fixed wing, 2 is landing gear, 3 is shell, 4 is connecting part, 6 is rigid connecting tube, 7 is flexible connecting tube, 8 is fixed platform, 9 is battery slot, 10 is servo motor, 11 is rotor, 12 is fixed frame, 101 is straight wing, 102 is side wing. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings and specific embodiments: Example 1

[0023] like Figures 1-5 As shown, a small tail-seat biplane quadcopter UAV includes a fixed-wing mechanism for level flight and a rotor device for vertical takeoff and landing. The fixed-wing mechanism includes two fixed wings 1 with internal cavities, arranged in parallel, and connected by a connecting mechanism. The two fixed wings 1 are fixed together by the connecting mechanism. Rotor devices are symmetrically arranged on both sides of the upper end of each fixed wing 1, and landing gear 2 is provided at the bottom end of each fixed wing 1, corresponding to the rotor devices. A housing 3 is provided on the upper part of the connecting mechanism, and a control module is provided inside the housing 3. The control module includes an MCU chip and a detection unit. The detection unit is used to detect the attitude of the UAV, and the output end of the detection unit is connected to the input end of the MCU chip. The output end of the MCU chip is connected to a servo drive module, and the MCU chip is communicatively connected to a remote controller. The servo drive module is used to drive the rotor devices.

[0024] To improve the stability of a small tail-mounted biplane quadcopter UAV, the fixed wing 1 includes a straight wing 101 and two side wings 102. The two side wings 102 are symmetrically arranged on both sides of the straight wing 101. The straight wing 101 and the two side wings 102, when combined, form a curved structure that gradually tapers from the front end to the tail end. A cavity is provided inside the straight wing 101, and a connecting mechanism is provided in the middle of the straight wing 101. The connecting mechanism includes a connecting part 4, a rigid connecting tube 6, and two flexible connecting tubes 7. The connecting part 4 is an inverted mountain-shaped plate structure, and the vertical section of the connecting part 4 is detachably connected to the straight wing 101. For each of the two fixed wings 1, there are two connecting parts 4. The middle of the horizontal section of each of the two connecting parts 4 is fixed to both ends of the rigid connecting tube 6, and the flexible connecting tubes 7 are symmetrically arranged at the edges of the horizontal section, with both ends of the flexible connecting tubes 7 fixed to the two connecting parts 4. During operation, the desired attitude of the small tail-seat biplane quadrotor UAV is set by the remote controller. The position loop controller and attitude loop controller control the servo motor 10 to change the rotation speed of the rotor device, thereby realizing the vertical take-off and landing of the small tail-seat biplane quadrotor UAV. In the air, its straight wing 101 and side wing 102 ensure the flight of the UAV through aerodynamics. Its position loop controller and attitude loop controller switch the control variables to make the system state slide along the sliding surface, so that the system has invariance when subjected to parameter disturbances and gust interference, and achieves stable operation in the air.

[0025] A housing 3 is fixedly installed in the middle of the rigid connecting pipe 6. The housing 3 is a hollow square structure. A servo drive module and a control module are installed inside the housing 3. The housing 3 is fixed to the rigid connecting pipe 6.

[0026] To facilitate power configuration and optimize power supply, a fixed platform 8 is provided in the inner cavity of the straight wing 101. The fixed platform 8 is a U-shaped plate, and its bottom surface is fixed to the straight wing 101. An energy module and two battery slots 9 are provided on the inner side of the fixed platform 8. The battery slots 9 are arc-shaped structures made of flexible material, and the two battery slots 9 are symmetrically arranged. A square notch is provided on the side wall of the fixed platform 8 near the connecting part 4. The vertical section of the connecting part 4 corresponding to the square notch enters the inner cavity of the straight wing 101 and engages with the square notch.

[0027] In order to enable the servo drive module to drive the rotor device, the servo drive module includes a servo motor 10, and the rotor device includes a rotor 11 and a fixed frame 12. The fixed frame 12 has a stepped cylindrical structure, with one side of the fixed frame 12 fixed to the output shaft of the servo motor 10 and the other side fixed to the rotor 11.

[0028] The landing gear 2 has a trapezoidal sheet structure and is an integrated structure with the straight wing 101. The landing gear 2 is located at the lower part of the fuselage and adopts the tail-seat takeoff characteristics of UAVs, making the takeoff process more stable.

[0029] The control module is equipped with a position loop controller and an attitude loop controller, and the detection unit includes a gyroscope sensor, an accelerometer sensor, an ultrasonic sensor, a barometric pressure sensor, and a GPS module.

[0030] During operation, the desired attitude of the small tail-seat biplane quadrotor UAV is set by the remote controller. The position loop controller and attitude loop controller control the servo motor 10 to change the rotation speed of the rotor device, thereby realizing the vertical take-off and landing of the small tail-seat biplane quadrotor UAV. In the air, its straight wing 101 and side wing 102 ensure the flight of the UAV through aerodynamics. Its position loop controller and attitude loop controller switch the control variables to make the system state slide along the sliding surface, so that the system has invariance when subjected to parameter disturbances and gust interference, and achieves stable operation in the air. Example 2

[0031] The second aspect of this invention provides a control method for a small biplane quadcopter unmanned aerial vehicle (UAV), specifically: Step 1: Input the takeoff command and desired motion attitude into the remote controller; Step 2: The aircraft attitude is detected by the detection unit, and the servo drive module is activated by the control module to operate the rotor device, causing the aircraft to rise vertically. Step 3: Input the real-time detected current body attitude into the attitude loop controller, complete the body attitude adjustment calculation through the position loop controller and attitude loop controller, and output the adjustment signal to the servo drive module; Step 4: The servo drive module adjusts the rotor device to put the aircraft in the desired motion attitude, and the aircraft changes from the transition mode to the level flight mode; Step 5: The detection unit detects the body's posture and transmits the posture parameters to the remote controller. The remote controller compares and analyzes the adjusted posture parameters with the desired motion posture to confirm whether the body has achieved the desired motion posture. If the desired flight posture is achieved, a signal indicating completion of the predetermined flight mission will be sent via the remote controller. If the desired motion posture is not achieved, a landing command is issued via remote control, and the servo drive module drives the rotor to complete the landing.

[0032] The position loop controller is used to track the desired position of the UAV and to generate angular velocity commands. The position loop controller transmits the angular velocity commands to the attitude loop controller, which tracks the angular velocity commands. The position loop controller uses integral sliding mode control, and the integral term is used to eliminate steady-state and static errors caused by aerodynamic influences. The attitude loop controller uses backstepping sliding mode control.

[0033] The small tail-seat biplane quadcopter UAV has three transformation modes: quadcopter mode, transition mode, and horizontal flight mode; the attitude parameters mentioned in step 2 include the attitude information, speed information, and acceleration information of the UAV measured by the gyroscope sensor, accelerometer, ultrasonic sensor, barometer, and GPS module; the motion tasks mentioned in step 5 include three-dimensional spatial rotational motion in the roll, pitch, and yaw directions.

[0034] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Therefore, all equivalent changes or modifications made to the structure, features and principles described in the claims of the present invention should be included within the scope of the present invention.

Claims

1. A small tail seat type twin-wing four-propeller unmanned aerial vehicle comprising a fixed-wing mechanism for air level flight and a rotor device for vertical take-off and landing, characterized in that, The fixed wing mechanism includes two fixed wings (1) with internal cavities. The two fixed wings (1) are arranged in parallel and a connecting mechanism is provided between the two fixed wings (1). The two fixed wings (1) are fixed by the connecting mechanism. Rotor devices are symmetrically arranged on both sides of the upper end of the fixed wing (1). Landing gear (2) is provided at the bottom end of the fixed wing (1). The landing gear (2) is arranged corresponding to the rotor devices. The upper part of the connecting mechanism is provided with a housing (3), and a control module is provided inside the housing (3); the control module includes an MCU chip and a detection unit, the detection unit is used to detect the body attitude, the output end of the detection unit is connected to the input end of the MCU chip, the output end of the MCU chip is connected to a servo drive module, and the MCU chip is connected to a remote controller; the servo drive module is used to drive the rotor device; The fixed wing (1) includes a straight wing (101) and two side wings (102). The two side wings (102) are symmetrically arranged on both sides of the straight wing (101). The straight wing (101) and the two side wings (102) are combined to form a curved surface structure that gradually tapers from the front end to the rear end. A cavity is provided inside the straight wing (101). A connecting mechanism is provided in the middle of the straight wing (101). The connecting mechanism includes a connecting part (4), a rigid connecting pipe (6), and two flexible connecting pipes (7). The connecting part (4) is an inverted mountain-shaped plate structure. The vertical section of the connecting part (4) is detachably connected to the straight wing (101). For the two fixed wings (1), there are two connecting parts (4). The middle position of the horizontal section of the two connecting parts (4) is fixed to both ends of the rigid connecting pipe (6). Flexible connecting pipes (7) are symmetrically arranged at the edge position of the horizontal section, and both ends of the flexible connecting pipes (7) are fixed to the two connecting parts (4).

2. The small tail-seat biplane quadrotor UAV according to claim 1, characterized in that, A housing (3) is fixedly installed in the middle of the rigid connecting pipe (6). The housing (3) is a square structure with a hollow interior. A servo drive module and a control module are installed inside the housing (3). The housing (3) is fixed to the rigid connecting pipe (6).

3. A small tail-mounted biplane quadcopter UAV according to claim 1, characterized in that, The inner cavity of the straight wing (101) is provided with a fixed platform (8). The fixed platform (8) is a U-shaped plate. The bottom surface of the fixed platform (8) is fixed to the straight wing (101). An energy module and two battery slots (9) are provided on the inner side of the fixed platform (8). The battery slots (9) are arc-shaped structures made of flexible material. The two battery slots (9) are symmetrically arranged. A square notch is opened on the side wall of the fixed platform (8) near the connecting part (4). The vertical section of the connecting part (4) corresponding to the square notch enters the inner cavity of the straight wing (101) and engages with the square notch.

4. A small tail-seat biplane quadrotor UAV according to claim 1, characterized in that, The servo drive module includes a servo motor (10), and the rotor device includes a rotor (11) and a mounting frame (12). The mounting frame (12) has a stepped cylindrical structure. One side of the mounting frame (12) is fixed to the output shaft of the servo motor (10), and the other side is fixed to the rotor (11).

5. A small tail-mounted biplane quadcopter UAV according to claim 2, characterized in that, The landing gear (2) is a trapezoidal sheet structure, and the landing gear (2) and the straight wing (101) are an integrated structure.

6. A small tail-mounted biplane quadcopter UAV according to claim 1, characterized in that, The control module is equipped with a position loop controller and an attitude loop controller, and the detection unit includes a gyroscope sensor, an accelerometer sensor, an ultrasonic sensor, a barometric pressure sensor, and a GPS module.

7. A control method for a small tail-seat biplane quadrotor unmanned aerial vehicle according to any one of claims 1 to 6, characterized in that, include: Step 1: Input the takeoff command and desired motion attitude into the remote controller; Step 2: The aircraft attitude is detected by the detection unit, and the servo drive module is activated by the control module to operate the rotor device, causing the aircraft to rise vertically. Step 3: Input the real-time detected current body attitude into the attitude loop controller, complete the body attitude adjustment calculation through the position loop controller and attitude loop controller, and output the adjustment signal to the servo drive module; Step 4: The servo drive module adjusts the rotor device to put the aircraft in the desired motion attitude, and the aircraft changes from the transition mode to the level flight mode; Step 5: The detection unit detects the aircraft's attitude and transmits the attitude parameters to the remote controller. The remote controller compares and analyzes the adjusted attitude parameters with the desired motion attitude to confirm whether the aircraft has reached the desired motion attitude. If the desired motion attitude is reached, the remote controller sends a signal to complete the predetermined flight mission. If the desired motion attitude is not reached, the remote controller sends a landing command, and the servo drive module drives the rotor to complete the landing.

8. The control method for a small tail-mounted biplane quadrotor UAV according to claim 7, characterized in that, The position loop controller is used to track the desired position of the UAV and to generate angular velocity commands. The position loop controller transmits the angular velocity commands to the attitude loop controller, which is used to track the angular velocity commands. The position loop controller uses integral sliding mode control, with the integral term used to eliminate steady-state and static errors caused by aerodynamic influences. The attitude loop controller uses backstepping sliding mode control.

9. The control method for a small tail-mounted biplane quadrotor UAV according to claim 7, characterized in that, The small tail-seat biplane quadcopter UAV has three transformation modes: quadcopter mode, transition mode, and horizontal flight mode; the attitude parameters mentioned in step 2 include the attitude information, speed information, and acceleration information of the UAV measured by the gyroscope sensor, accelerometer, ultrasonic sensor, barometer, and GPS module; the motion tasks mentioned in step 5 include three-dimensional spatial rotational motion in the roll, pitch, and yaw directions.

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