Multi-mode flight control method for compound quadrotor unmanned aerial vehicle

Abstract

The present disclosure provides a kind of composite quadrotor unmanned aerial vehicle multimode flight control method, and the composite quadrotor unmanned aerial vehicle includes multi-rotor platform and fixed wing platform, the flight control method includes: multi-rotor mode part, fixed wing mode part and transition mode part, in each mode, by adjusting the multi-rotor platform rotor speed, or the speed of fixed wing platform engine, realize unmanned aerial vehicle vertical take-off, cruise operation and the attitude adjustment of transition mode unmanned aerial vehicle.The composite quadrotor unmanned aerial vehicle multimode flight control method provided by the present disclosure provides the control method of each component in the mode switching process of composite quadrotor unmanned aerial vehicle, especially the control scheme of multi-rotor platform and fixed wing platform of unmanned aerial vehicle in transition mode, to realize decoupling control, so that unmanned aerial vehicle realizes full autonomous vertical take-off, mode switching.

Description

Technical Field

[0001] This disclosure relates to the field of aircraft control technology, and in particular to a multimodal flight control method for a compound quadcopter unmanned aerial vehicle. Background Technology

[0002] Fixed-wing multirotor hybrid unmanned aerial vehicles (UAVs), or simply hybrid-wing UAVs, are a new type of aircraft distinct from traditional fixed-wing and rotary-wing UAVs. By adding a multirotor system to a fixed-wing flight platform, they achieve VTOL (Vertical Take-off and Landing) and hovering capabilities, while retaining the cruising speed and range advantages of fixed-wing UAVs. Compared to other UAV systems, hybrid-wing UAVs offer significant advantages. Compared to helicopters, hybrid-wing UAVs have a simpler structure, lower cost, higher safety, and longer endurance; compared to multirotors, they have longer flight time, greater range, higher cruising speed, and better stable flight performance under complex weather conditions; compared to fixed-wing aircraft, hybrid-wing UAVs do not require dedicated runways, have a wider range of applications, are easier to use, and offer greater flexibility in launch locations.

[0003] Most existing compound-wing UAVs are developed by adding VTOL systems to existing fixed-wing flight platforms. The overall flight characteristics, aerodynamic drag, controllability, stability and structural strength of the aircraft are very different from those of previous fixed-wing UAVs.

[0004] However, in the process of developing this disclosure, the inventors discovered a control coupling problem between the VTOL system and the fixed-wing platform, which increases the difficulty of transition mode control. This problem poses a challenge to the flight control of compound-wing UAVs. Therefore, how to achieve decoupled control and enable UAVs to achieve fully autonomous vertical takeoff and landing and mode switching is of great significance to the development of compound-wing UAVs. VTOL systems are classified into tri-rotor systems, quadcopter systems, coaxial counter-rotor octocopter systems, and other multi-rotor systems depending on the multi-rotor configuration. Due to the different multi-rotor configurations, their control methods differ significantly in principle. This disclosure uses a quadcopter system as an example to detail a multi-modal flight control method for a compound quadcopter UAV.

[0005] Public content

[0006] (a) Technical problems to be solved

[0007] Based on the above-mentioned technical problems, this disclosure provides a multimodal flight control method for a compound quadcopter unmanned aerial vehicle (UAV) to alleviate the technical problem of control coupling between the VTOL system and the fixed-wing platform in existing UAV control methods.

[0008] (II) Technical Solution

[0009] This disclosure provides a multimodal flight control method for a compound quadrotor unmanned aerial vehicle (UAV). The compound quadrotor UAV includes a multirotor platform and a fixed-wing platform. The flight control method includes:

[0010] Multi-rotor mode: By adjusting the rotor speed of the multi-rotor platform, lift is generated in the vertical direction to achieve vertical take-off and landing of the UAV;

[0011] Fixed-wing mode: By adjusting the engine speed of the fixed-wing platform, the forward flight speed of the UAV is maintained above the initial transition speed, enabling UAV operation; and

[0012] The transition mode part includes:

[0013] Transition from multi-rotor mode to fixed-wing mode: gradually increase the engine speed to the maximum speed and maintain it, increase the forward flight speed of the UAV to the initial conversion speed, and then gradually decrease the rotor speed until 0 rpm;

[0014] Transition from fixed-wing mode to multi-rotor mode: Gradually reduce the engine speed and gradually increase the rotor speed to reduce the forward flight speed of the compound quadcopter UAV until the multi-rotor mode cruise speed.

[0015] In some embodiments of this disclosure, the multi-rotor mode includes: a vertical takeoff phase: after the UAV takes off vertically from the target location, the rotational speed of the rotor is adjusted to allow the UAV to reach and maintain a certain altitude, and then the rotational speed of the engine is adjusted to allow the UAV to begin generating forward flight speed; a vertical landing phase: after the forward flight speed of the UAV decreases to the multi-rotor mode cruise speed and cruises in multi-rotor mode to reach the target landing location, the rotational speed of the rotor is adjusted to allow the UAV to descend until the UAV lands at the target altitude; and a hovering phase: after the UAV rises to a certain altitude, the rotational speed of the rotor is adjusted to make the vertical lift generated by the rotor equal to the weight of the UAV, thereby achieving hovering of the UAV at a fixed point; in the vertical takeoff and vertical landing phases, the multi-rotor platform maintains the target attitude angle of the UAV at 0°, and the proportional servo output of each aerodynamic control surface of the fixed-wing platform is 0.

[0016] In some embodiments of this disclosure, the multi-rotor mode portion achieves altitude control, pitch control, roll control, and yaw control of the UAV by manipulating the rotational speed of the rotors of the multi-rotor platform, enabling the UAV to achieve vertical take-off, vertical landing, and hovering in multi-rotor mode.

[0017] In some embodiments of this disclosure, the altitude control adjusts the lift generated by the multi-rotor platform by changing the rotational speed of the rotors; when the lift is greater than gravity, the drone ascends, and when it is less than gravity, the drone descends. The pitch control generates a lift difference by controlling the different rotational speeds of the rotors in the front and rear rows of the multi-rotor platform, thereby generating a pitch moment around the drone's center of mass and adjusting the drone's pitch attitude. The roll control generates a roll moment around the center of mass by controlling the different rotational speeds of the rotors in the left and right rows of the multi-rotor platform, adjusting the drone's roll attitude. The yaw control generates a yaw moment about the vertical axis in the longitudinal plane by controlling the different rotational speeds of the two diagonally opposite sets of rotors of the multi-rotor platform, adjusting the drone's heading.

[0018] In some embodiments of this disclosure, the fixed-wing mode includes: a fixed-wing climb phase: after the UAV enters the fixed-wing mode, it climbs to a predetermined operating altitude using the fixed-wing platform; a fixed-wing cruise phase: after the UAV climbs to the predetermined operating altitude, it performs cruise operations using the fixed-wing platform; and a fixed-wing dive phase: after completing the mission, the UAV dives to a predetermined switching altitude using the fixed-wing platform, preparing to switch to the transition mode.

[0019] In some embodiments of this disclosure, the fixed-wing mode portion achieves altitude control, pitch control, roll control, yaw control, and horizontal speed control of the UAV by manipulating the engine, elevator, aileron, and rudder of the fixed-wing platform, enabling the UAV to perform climb, cruise, and dive functions in fixed-wing mode.

[0020] In some embodiments of this disclosure, the altitude control and pitch control, by controlling the different deflection angles of the elevator surfaces of the fixed-wing platform, change the direction of aerodynamic drag generated by the air on the elevator during the UAV's cruise flight, generating a pitch moment around the UAV's center of mass, and adjusting the UAV's pitch attitude and flight altitude; the roll control, by controlling the different deflection angles of the aileron surfaces of the fixed-wing platform, changes the direction of aerodynamic drag generated by the air on the left and right wings during the UAV's cruise flight, generating a roll moment around the UAV's center of mass, and adjusting the UAV's roll attitude; the yaw control, by controlling the different deflection angles of the rudder of the fixed-wing platform, changes the direction of aerodynamic drag generated by the air on the rudder during the UAV's cruise flight, thereby generating a yaw moment around the UAV's center of mass, and adjusting the UAV's heading; and the horizontal speed control adjusts the UAV's flight speed by changing the rotational speed of the engine of the fixed-wing platform.

[0021] In some embodiments of this disclosure, the transition mode portion achieves altitude control, pitch control, roll control, yaw control, and horizontal speed control of the UAV by manipulating the rotor speed of the multi-rotor platform and the engine, elevator, aileron, and rudder of the fixed-wing platform, so that the UAV can achieve a smooth transition in the transition mode.

[0022] In some embodiments of this disclosure, the altitude control adjusts the lift generated by changing the rotational speed of each rotor of the multi-rotor platform, thereby changing the magnitude of the resultant force in the vertical direction of the UAV and thus adjusting the altitude of the UAV; the pitch control includes: differential control of the rotational speed of the front and rear rotors of the multi-rotor platform and adjustment of the deflection angle of the elevator surface of the fixed-wing platform; the roll control includes: differential control of the rotational speed of the left and right rotors of the multi-rotor platform and adjustment of the deflection angle of the aileron surface of the fixed-wing platform; the yaw control includes: differential control of the rotational speed of the diagonally opposite rotors of the multi-rotor platform and adjustment of the deflection angle of the rudder of the fixed-wing platform; the horizontal speed control includes: individually changing the rotational speed of the engine of the fixed-wing platform, or simultaneously changing the rotational speed of the engine of the fixed-wing platform and the rotational speed of the front and rear rotors of the multi-rotor platform.

[0023] In some embodiments of this disclosure, the initial conversion speed is 1 to 1.5 times the minimum airspeed requirement for fixed-wing mode cruise, and the multi-rotor mode cruise speed is between 3 m / s and 5 m / s.

[0024] (III) Beneficial Effects

[0025] As can be seen from the above technical solution, the multi-modal flight control method for the compound quadcopter UAV provided in this disclosure has one or more of the following beneficial effects:

[0026] (1) The multi-mode flight control method of the compound quadcopter UAV provided in this disclosure provides the control method of each component during the mode switching process of the compound quadcopter UAV, especially the control scheme of the UAV multi-rotor platform and fixed-wing platform in the transition mode, thereby realizing decoupled control and enabling the UAV to achieve fully autonomous vertical take-off and landing and mode switching.

[0027] (2) Maintaining the engine's maximum speed for a certain period of time during the transition from multi-rotor mode to fixed-wing mode can prevent strong airflow interference that could cause flight attitude instability during the transition from the transition mode to the fixed-wing mode.

[0028] (3) Set the initial conversion speed to 1 to 1.5 times the minimum airspeed requirement for fixed-wing mode cruise. The specific initial conversion speed is adjusted according to the different aerodynamic characteristics of different aircraft platforms. This can prevent the wing from being unable to generate enough aerodynamic lift to offset the weight of the aircraft due to the initial conversion speed being too small, which would cause the compound quadcopter UAV to enter a stall state. It can also prevent the transition time in the second half from being significantly reduced due to the initial conversion speed being too large. However, the aerodynamic coupling problem between the rotor and the wing will be very prominent during the acceleration and forward flight in the first half, which will increase the difficulty of controlling the transition mode. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the UAV attitude in each mode in the multi-modal flight control method for a compound quadcopter UAV provided in the embodiments of this disclosure.

[0030] Figure 2 This is a schematic diagram of the structure of the UAV in the multimodal flight control method for the composite quadcopter UAV provided in the embodiments of this disclosure.

[0031] Figure 3 This is a schematic diagram of the entire flight profile process in the multimodal flight control method for a compound quadcopter UAV provided in this embodiment of the disclosure.

[0032] Figure 4 This is a schematic diagram of the control methods for the multi-rotor mode in the multi-modal flight control method for a compound quadcopter UAV provided in the embodiments of this disclosure.

[0033] Figure 5 This is a schematic diagram of the control methods for the fixed-wing mode in the multimodal flight control method for a compound quadcopter UAV provided in the embodiments of this disclosure.

[0034] Figure 6 This is a schematic diagram of the control methods for the transition mode portion of the multimodal flight control method for a compound quadcopter UAV provided in the embodiments of this disclosure.

[0035] [Explanation of key component symbols in the accompanying drawings of this disclosure embodiment]

[0036] 11-Rotor; 12-Engine; 13-Elevator;

[0037] 14-Aileron; 15-Rudder. Detailed Implementation

[0038] The multi-modal flight control method for a compound quadrotor UAV provided in this disclosure provides a method for controlling each component during mode switching of the compound quadrotor UAV, especially the control scheme for the multi-rotor platform and the fixed-wing platform of the UAV in the transition mode, thereby achieving decoupled control and enabling the UAV to achieve fully autonomous vertical take-off and landing and mode switching.

[0039] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0040] Figure 1 This is a schematic diagram of the UAV attitude in each mode in the multi-modal flight control method for a compound quadcopter UAV provided in the embodiments of this disclosure. Figure 2 This is a schematic diagram of the structure of the UAV in the multimodal flight control method for the composite quadcopter UAV provided in the embodiments of this disclosure. Figure 3 This is a schematic diagram of the entire flight profile process in the multimodal flight control method for a compound quadcopter UAV provided in this embodiment of the disclosure.

[0041] This disclosure provides a multimodal flight control method for a compound quadcopter unmanned aerial vehicle (UAV), such as... Figures 1 to 3 As shown, the compound quadcopter UAV includes a multi-rotor platform and a fixed-wing platform, and the flight control method includes:

[0042] Multi-rotor mode: Vertical lift is generated by adjusting the rotation speed of the multi-rotor platform rotor 11 to achieve vertical take-off and landing of the UAV;

[0043] Fixed-wing mode: By adjusting the rotational speed of the fixed-wing platform engine 12, the forward flight speed of the UAV is maintained above the initial transition speed, enabling UAV operations; and

[0044] The transition mode part includes:

[0045] Transition from multi-rotor mode to fixed-wing mode: gradually increase the engine speed of 12 to the maximum speed and maintain it, increase the forward flight speed of the UAV to the initial conversion speed, and then gradually reduce the speed of rotor 11 until 0 rpm;

[0046] Transition from fixed-wing mode to multi-rotor mode: gradually reduce the engine speed 12 and gradually increase the rotor speed 11 to reduce the forward flight speed of the compound quadcopter UAV until the multi-rotor mode cruise speed.

[0047] The multi-modal flight control method for a compound quadrotor UAV provided in this disclosure provides a method for controlling each component during mode switching of the compound quadrotor UAV, especially the control scheme for the multi-rotor platform and the fixed-wing platform of the UAV in the transition mode, thereby achieving decoupled control and enabling the UAV to achieve fully autonomous vertical take-off and landing and mode switching.

[0048] In some embodiments of this disclosure, such as Figure 3As shown, the multi-rotor mode includes: vertical takeoff phase: after the UAV takes off vertically from the target location, the speed of rotor 11 is adjusted to enable the UAV to reach and maintain a certain altitude, and then the speed of engine 12 is adjusted to enable the UAV to start generating forward flight speed; when the compound quadcopter UAV just begins to have forward flight speed, the speed does not reach the minimum airspeed requirement of the fixed-wing mode, and the wings cannot generate enough atmospheric lift to maintain the current altitude. At this time, the vector thrust of rotor 11 mainly relies on the aircraft's own weight to offset the flight altitude of the compound quadcopter UAV.

[0049] In some embodiments of this disclosure, such as Figure 3 As shown, the multi-rotor mode section also includes: vertical landing phase: after the forward speed of the UAV decreases to the multi-rotor mode cruise speed and cruises in multi-rotor mode to reach the target landing location, the UAV lowers its altitude by adjusting the rotation speed of rotor 11. At this time, the vector thrust of rotor 11 cannot completely offset the UAV's own gravity, and the flight altitude of the compound quadcopter UAV will continue to decrease until the UAV lands at the target altitude.

[0050] In some embodiments of this disclosure, the multi-rotor mode further includes: a hovering phase: after the UAV has risen to a certain height, the rotational speed of the rotor 11 is adjusted so that the vertical lift generated by the rotor 11 is equal to the weight of the UAV, thereby achieving hovering of the UAV at a fixed point; during the vertical take-off and vertical landing phases, the multi-rotor platform maintains the target attitude angle of the UAV at 0°, and the proportional servo output of each aerodynamic control surface of the fixed-wing platform is 0.

[0051] Figure 4 This is a schematic diagram of the control methods for the multi-rotor mode in the multi-modal flight control method for a compound quadcopter UAV provided in the embodiments of this disclosure. Figure 4 Part (A) represents the height control method. Figure 4 Part (B) indicates the pitch control method. Figure 4 The middle (C) section indicates the roll control method. Figure 4 The middle (D) section represents the yaw control method, where a long arrow indicates a high rotational speed and a short arrow indicates a lower rotational speed relative to the long arrow. To clearly illustrate the pitch, roll, yaw, speed, and altitude control methods, this embodiment specifies that after the four rotors of the multi-rotor platform are installed, the diagonal rotors rotate in the same direction. Specifically, the front left rotor 11 and the rear right rotor 11 rotate counterclockwise, and the front right rotor 11 and the rear left rotor 11 rotate clockwise. In practical applications, other installation configurations may be used, and the control methods will need to be adjusted accordingly.

[0052] In some embodiments of this disclosure, such as Figure 4As shown, the multi-rotor mode section controls the altitude, pitch, roll and yaw of the UAV by manipulating the rotation speed of the rotor 11 of the multi-rotor platform, enabling the UAV to achieve vertical take-off, vertical landing and hovering in multi-rotor mode.

[0053] In some embodiments of this disclosure, such as Figure 4 As shown in (A), altitude control adjusts the lift generated by changing the rotational speed of the rotor 11 of the multi-rotor platform. When the lift is greater than gravity, the drone ascends; when it is less than gravity, the drone descends. The four rotors 11 of the multi-rotor platform are installed with adjacent rotors rotating in opposite directions to reduce the impact of the reverse torque generated by the high-speed rotation of the rotors 11 on the drone.

[0054] In some embodiments of this disclosure, such as Figure 4 As shown in (B), pitch control generates a lift difference by controlling the different rotational speeds of the front and rear rotors 11 of the multi-rotor platform, thereby generating a pitch moment around the UAV's center of mass and adjusting the UAV's pitch attitude; as Figure 4 As shown in (B), by increasing the rotational speed of the front rotor 11 and decreasing the rotational speed of the rear rotor 11, the drone will lift its head and fly backward; or (not shown in the figure), by decreasing the rotational speed of the front rotor 11 and increasing the rotational speed of the rear rotor 11, the drone will lower its head and fly forward.

[0055] In some embodiments of this disclosure, such as Figure 4 As shown in (C), roll control generates a roll torque around the center of mass by controlling the different rotation speeds of the left and right rows of rotors 11 on the multi-rotor platform, thereby adjusting the roll attitude of the UAV; as Figure 4 As shown in (C), by increasing the rotational speed of the left rotor 11 and decreasing the rotational speed of the right rotor 11, the drone will roll to the right; or (not shown in the figure), by increasing the rotational speed of the right rotor 11 and decreasing the rotational speed of the left rotor 11, the drone will roll to the left.

[0056] In some embodiments of this disclosure, such as Figure 4 As shown in (D), yaw control generates a yaw torque about the vertical axis in the longitudinal plane by controlling the different rotation speeds of the two sets of diagonal rotors 11 on the multi-rotor platform, thus adjusting the UAV's heading. By increasing the rotation speed of one set of diagonal rotors 11 while decreasing the rotation speed of the other set, the UAV will produce yaw motion, as shown in (D). Figure 4 As shown in (D), by increasing the rotational speed of the front left rotor 11 and the rear right rotor 11 and decreasing the rotational speed of the front right rotor 11 and the rear left rotor 11, the UAV yaws to the right; or (not shown in the figure), by decreasing the rotational speed of the front left rotor 11 and the rear right rotor 11 and increasing the rotational speed of the front right rotor 11 and the rear left rotor 11, the UAV yaws to the left.

[0057] In some embodiments of this disclosure, such as Figure 3 As shown, the fixed-wing mode includes: fixed-wing climb phase: after entering the fixed-wing mode, the UAV climbs to the predetermined operating altitude using the fixed-wing platform; fixed-wing cruise phase: after climbing to the predetermined operating altitude, the UAV cruises using the fixed-wing platform; and fixed-wing dive phase: after completing the mission, the UAV dives to the predetermined switching altitude using the fixed-wing platform, preparing to switch to the transition mode.

[0058] Figure 5 This is a schematic diagram of the control methods for the fixed-wing mode in the multimodal flight control method for a compound quadcopter UAV provided in the embodiments of this disclosure. Figure 5 Part A in the middle represents the altitude control method and the pitch control method. Figure 5 Part (B) indicates the roll control method. Figure 5 The middle (C) section represents the yaw control method. Figure 5 The middle (D) section represents the speed control method, where the upward arrow on each control surface represents the control surface deflecting upward, the downward arrow represents the control surface deflecting downward, the left arrow represents the control surface deflecting to the left, the right arrow represents the control surface deflecting to the right, and the upward arrow on the engine represents the engine speed increase.

[0059] In some embodiments of this disclosure, such as Figure 5 As shown, the fixed-wing mode section controls the altitude, pitch, roll, yaw and horizontal speed of the UAV by manipulating the engine 12, elevator 13, aileron 14 and rudder 15 of the fixed-wing platform, enabling the UAV to climb, cruise and dive in fixed-wing mode.

[0060] In some embodiments of this disclosure, such as Figure 5 As shown in (A), altitude control and pitch control, by controlling the different deflection angles of the elevator 13 on the fixed-wing platform, change the direction of the aerodynamic drag generated by the air on the elevator 13 during the UAV's cruise flight, generating a pitch moment around the UAV's center of mass, and adjusting the UAV's pitch attitude and flight altitude, such as... Figure 5 As shown in (A), the UAV can be made to pitch up by tilting the elevator 13 surface; or (not shown in the figure), the UAV can be made to pitch down by tilting the elevator 13 surface.

[0061] In some embodiments of this disclosure, such as Figure 5 As shown in (B), roll control alters the direction of aerodynamic drag on the left and right wings of the UAV during cruise flight by controlling the deflection angle of the aileron 14 control surfaces of the fixed-wing platform. This generates a roll moment around the UAV's center of mass, adjusting the UAV's roll attitude, such as... Figure 5As shown in (B), the UAV can roll to the right by deflecting the left aileron 14 control surface downward and the right aileron 14 control surface upward; or (not shown in the figure), the UAV can roll to the left by deflecting the left aileron 14 control surface upward and the right aileron 14 control surface downward.

[0062] In some embodiments of this disclosure, such as Figure 5 As shown in (C), yaw control changes the direction of aerodynamic drag on the rudder during UAV cruise flight by controlling the different deflection angles of the fixed-wing platform's rudder 15, thereby generating a yaw moment around the UAV's center of mass and adjusting the UAV's heading, such as... Figure 5 As shown in (C), the UAV can yaw to the right by deflecting the rudder 15 to the right; or (not shown in the figure), the UAV can yaw to the left by deflecting the rudder 15 to the left. Yaw control can also be achieved in conjunction with the aileron 14 rudder surface deflection assistance, as shown in the figure. Figure 5 As shown in (C), when the rudder 15 deflects to the right, the left aileron 14 deflects downward, and the right aileron 14 deflects upward, the UAV yaws to the right; or (not shown in the figure), when the rudder 15 deflects to the left, the left aileron 14 deflects upward, and the right aileron 14 deflects downward, the UAV yaws to the left.

[0063] In some embodiments of this disclosure, such as Figure 5 As shown in (D), horizontal speed control adjusts the flight speed of the UAV by changing the rotational speed of the fixed-wing platform engine 12.

[0064] In some embodiments of this disclosure, the transition from multi-rotor mode to fixed-wing mode in the transition mode section includes: a first stage: gradually increasing the rotational speed of engine 12 to increase the forward flight speed of the UAV until the minimum airspeed requirement for fixed-wing mode cruise is met; and a second stage: continuing to increase the rotational speed of engine 12 to the maximum speed and maintaining it, and when the forward flight speed reaches the initial conversion speed, gradually reducing the rotational speed of rotor 11 to 0 rpm, transitioning from multi-rotor mode to fixed-wing mode (especially in the second stage), maintaining the maximum engine speed for a certain period of time can avoid strong airflow interference at the moment of switching from transition mode to fixed-wing mode, which can lead to flight attitude instability.

[0065] Figure 6 This is a schematic diagram of the control methods for the transition mode portion of the multimodal flight control method for a compound quadcopter UAV provided in the embodiments of this disclosure. Figure 6 Part (A) represents the height control method. Figure 6 Part B: Pitch control method Figure 6 The middle (C) section indicates the roll control method. Figure 6 The middle (D) section represents the yaw control method. Figure 6The middle (E) section represents the speed control method, where the long arrows on each rotor represent high speed, the short arrows represent low speed relative to the long arrows, the upward arrows on each control surface represent deflection, the downward arrows represent downward deflection, the left arrows represent left deflection, the right arrows represent right deflection, and the upward arrows on the engine represent engine speed increase.

[0066] In some embodiments of this disclosure, such as Figure 6 As shown, the transition mode section controls the altitude, pitch, roll, yaw, and horizontal speed of the UAV by manipulating the rotation speed of the rotor 11 of the multi-rotor platform and the engine 12, elevator 13, aileron 14, and rudder 15 of the fixed-wing platform, enabling the UAV to achieve a smooth transition in the transition mode.

[0067] In some embodiments of this disclosure, such as Figure 6 As shown in (A), altitude control adjusts the lift generated by changing the rotational speed of each rotor 11 of the multi-rotor platform, thereby changing the magnitude of the resultant force in the vertical direction of the UAV and thus adjusting the altitude of the UAV.

[0068] In some embodiments of this disclosure, such as Figure 6 As shown in (B), pitch control includes: differential speed control of the front and rear rotors 11 of the multi-rotor platform and adjustment of the deflection angle of the elevator surface 13 of the fixed-wing platform. Figure 6 In (B), by increasing the rotational speed of the front rotor 11 and decreasing the rotational speed of the rear rotor 11, while simultaneously deflecting the control surface of the elevator 13, the UAV will pitch up and climb; or (not shown in the figure), by decreasing the rotational speed of the front rotor 11 and increasing the rotational speed of the rear rotor 11, while simultaneously deflecting the control surface of the elevator 13 downward, the UAV will pitch down and dive.

[0069] In some embodiments of this disclosure, such as Figure 6 As shown in (C), the roll control includes: differential speed control of the left and right rotors 11 of the multi-rotor platform and adjustment of the deflection angle of the aileron 14 control surfaces of the fixed-wing platform. Figure 6 In (C), by increasing the rotational speed of the left rotor 11 and decreasing the rotational speed of the right rotor 11, and by deflecting the left aileron 14 downward and the right aileron 14 upward, the UAV will roll to the right; or (not shown in the figure), by decreasing the rotational speed of the left rotor 11 and increasing the rotational speed of the right rotor 11, and by deflecting the left aileron 14 upward and the right aileron 14 downward, the UAV will roll to the left.

[0070] In some embodiments of this disclosure, such as Figure 6 As shown in (D), yaw control includes: differential speed control of the diagonal rotor 11 on the multi-rotor platform and adjustment of the yaw angle of the rudder 15 on the fixed-wing platform. Figure 6In (D), by increasing the rotational speed of the rotors 11 on the left front row and the right rear row, decreasing the rotational speed of the rotors 11 on the right front row and the left rear row, and deflecting the rudder 15 to the right, the UAV can yaw to the right; or (not shown in the figure), by decreasing the rotational speed of the rotors 11 on the left front row and the right rear row, increasing the rotational speed of the rotors 11 on the right front row and the left rear row, and deflecting the rudder 15 to the left, the UAV can yaw to the left.

[0071] In some embodiments of this disclosure, such as Figure 6 As shown in (E), horizontal speed control includes: individually changing the rotational speed of the fixed-wing platform engine 12, or simultaneously changing the rotational speeds of the fixed-wing platform engine 12 and the front and rear rotors 11 of the multi-rotor platform, such as... Figure 6 As shown in (E), by reducing the rotational speed of the front rotor 11, increasing the rotational speed of the rear rotor 11, and simultaneously increasing the rotational speed of the engine 12, the UAV can achieve horizontal acceleration; or (not shown in the figure), by increasing the rotational speed of the front rotor 11, reducing the rotational speed of the rear rotor 11, and simultaneously reducing the rotational speed of the engine 12, the UAV can achieve horizontal deceleration.

[0072] It should be noted that in horizontal speed control, if the rotational speed of the front and rear rotors 11 of the multi-rotor platform is changed to assist in horizontal speed control, the pitch attitude angle of the UAV should be limited to within ±5° to avoid excessive pitch of the UAV causing changes in the UAV's flight altitude.

[0073] During the transition mode, due to the combined effect of rotor 11 thrust and aerodynamics, there is an operational coupling of two flight modes. The weights of the two controls are not the same at different times in the transition mode. In order to allow the compound quadcopter UAV to pass through the transition mode smoothly as soon as possible, the rotor 11 thrust of the multi-rotor platform gradually decreases as the airspeed increases. That is, the weight of the rotor thrust in the vertical resultant force decreases as the airspeed changes. When the airspeed reaches a critical speed, the rotor 11 thrust of the multi-rotor platform withdraws from the control of the compound quadcopter UAV, and the aerodynamic control surfaces of the fixed-wing platform completely take over the control of the compound quadcopter UAV. The determination of this airspeed is determined by the aerodynamic characteristics of different flight platforms. During the process of the compound quadcopter UAV accelerating from 0 m / s to the critical airspeed, the flight altitude is maintained by the rotor 11 thrust and aerodynamic lift. After the airspeed is stable above the critical airspeed for a certain period of time, the aerodynamic control surfaces take over the flight control, and the rotor thrust withdraws from altitude control.

[0074] When a compound quadcopter drone transitions from multi-rotor mode to transition mode, there are certain requirements for the drone's current attitude angle. If the attitude angle value is too large, it indicates that the drone is not fully leveled. At this time, starting engine 12 may cause the drone's attitude to become unstable. If the pitch and roll attitude angles are within 5°, the compound quadcopter drone can be considered to be in a leveled state, allowing it to enter the transition mode.

[0075] In some embodiments of this disclosure, the initial transition speed is the critical speed at which the UAV begins to transition from multi-rotor mode to fixed-wing mode in the transition mode. It is 1 to 1.5 times the minimum airspeed requirement for fixed-wing mode cruise. The specific initial transition speed is adjusted according to the different aerodynamic characteristics of different aircraft platforms. The minimum airspeed requirement for fixed-wing mode cruise is the minimum speed at which the UAV wings can generate sufficient aerodynamic lift to maintain the current altitude when the UAV is cruising in fixed-wing mode. The multi-rotor mode cruise speed is between 3-5 m / s. Setting the initial transition speed to 1 to 1.5 times the minimum airspeed requirement for fixed-wing mode cruise can avoid the fact that the wings 11 cannot generate enough aerodynamic lift to offset the aircraft's weight due to the initial transition speed being too small, causing the compound quadcopter UAV to enter a stall state. It can also avoid the fact that the transition time in the second half is significantly reduced due to the initial transition speed being too large, but the aerodynamic coupling problem between the rotor and the wing will be very prominent during the acceleration process in the first half, thus increasing the difficulty of controlling the transition mode. The power consumption of multi-rotor mode is about 5 times that of fixed-wing mode. The long transition time will reduce the flight time of the drone and fail to realize the advantages of flight time and range of the compound quadcopter drone.

[0076] Based on the above description, those skilled in the art should have a clear understanding of the multimodal flight control method for the compound quadcopter UAV provided in this disclosure.

[0077] In summary, the multi-modal flight control method for the compound quadrotor UAV provided in this disclosure offers control methods for each component during mode switching of the compound quadrotor UAV, especially the control scheme for the multi-rotor platform and fixed-wing platform of the UAV in the transition mode, enabling the UAV to achieve fully autonomous vertical take-off and landing and mode switching.

[0078] It should also be noted that the directional terms mentioned in the embodiments, such as "up," "down," "front," "back," "left," and "right," are only for reference to the directions in the accompanying drawings and are not intended to limit the scope of protection of this disclosure. Throughout the drawings, the same elements are represented by the same or similar reference numerals. Conventional structures or constructions will be omitted where they may cause confusion in understanding this disclosure.

[0079] Furthermore, the shapes and dimensions of the components in the figures do not reflect actual size and proportion, but are merely illustrative of embodiments of this disclosure. Additionally, any reference numerals placed between parentheses in the claims should not be construed as limiting the scope of the claims.

[0080] Similarly, it should be understood that, in order to simplify this disclosure and aid in understanding one or more of the various aspects of the disclosure, in the foregoing description of exemplary embodiments of the disclosure, various features of the disclosure are sometimes grouped together in a single embodiment, figure, or description thereof. However, this approach to disclosure should not be construed as reflecting an intention that the claimed disclosure requires more features than are expressly recited in each claim. Rather, as reflected in the preceding claims, the disclosure aspect comprises fewer than all features of a single previously disclosed embodiment. Therefore, the claims following the detailed description are hereby expressly incorporated into that detailed description, wherein each claim itself is a separate embodiment of the disclosure.

[0081] The specific embodiments described above further illustrate the purpose, technical solutions, and beneficial effects of this disclosure. It should be understood that the above descriptions are merely specific embodiments of this disclosure and are not intended to limit this disclosure. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the protection scope of this disclosure.

Claims

1. A multimodal flight control method for a compound quadrotor unmanned aerial vehicle (UAV), the compound quadrotor UAV comprising a multirotor platform and a fixed-wing platform, wherein the fixed-wing platform comprises a left aileron, a right aileron, and an engine, wherein, The engine is connected to a propeller, and the multi-rotor platform includes four rotors respectively arranged in the front row of the left aileron, the rear row of the left aileron, the front row of the right aileron, and the rear row of the right aileron. The flight control method includes: Multi-rotor mode: By adjusting the rotor speed of the multi-rotor platform, lift is generated in the vertical direction to achieve vertical take-off and landing of the UAV; Fixed-wing mode: By adjusting the engine speed of the fixed-wing platform, the forward flight speed of the UAV is maintained above the initial transition speed, enabling UAV operation; and The transition mode portion includes: Transition from multi-rotor mode to fixed-wing mode: In the first stage, the engine speed is gradually increased to increase the forward speed of the UAV until the minimum airspeed requirement for fixed-wing mode cruise is met; In the second stage, the engine speed is further increased to the maximum speed and maintained for a preset duration to increase the forward speed of the UAV to the initial transition speed. After that, the rotor speed is gradually reduced to 0 rpm to avoid strong airflow interference that could cause flight attitude instability during the transition from the transition mode to the fixed-wing mode. The initial transition speed is 1 to 1.5 times the minimum airspeed requirement for fixed-wing mode cruise. Transition from fixed-wing mode to multi-rotor mode: Gradually reduce the engine speed and gradually increase the rotor speed to reduce the forward flight speed of the compound quadcopter UAV until the multi-rotor mode cruise speed.

2. The multi-modal flight control method for a compound quadcopter UAV according to claim 1, wherein the multi-rotor modal component comprises: Vertical takeoff phase: After the drone takes off vertically from the target location, the speed of the rotor is adjusted to allow the drone to reach and maintain a certain altitude, and then the speed of the engine is adjusted to allow the drone to start generating forward flight speed. Vertical landing phase: After the forward speed of the UAV is reduced to the cruise speed of the multi-rotor mode and it cruises in multi-rotor mode to reach the target landing location, the UAV is lowered by adjusting the rotation speed of the rotor until the UAV lands at the target altitude. as well as Hovering phase: After the drone has risen to a certain height, the rotation speed of the rotor is adjusted so that the vertical lift generated by the rotor is equal to the weight of the drone, thus enabling the drone to hover in a fixed position. During the vertical takeoff and vertical landing phases, the multi-rotor platform maintains the target attitude angle of the UAV at 0°, and the proportional servo output of each aerodynamic control surface of the fixed-wing platform is 0.

3. The multi-modal flight control method for a compound quadcopter UAV according to claim 2, wherein the multi-rotor mode part controls the altitude, pitch, roll and yaw of the UAV by manipulating the rotational speed of the rotor of the multi-rotor platform, so that the UAV can achieve vertical take-off, vertical landing and hovering in multi-rotor mode.

4. The multi-modal flight control method for a compound quadcopter UAV according to claim 3, wherein: The altitude control adjusts the lift generated by changing the rotational speed of the rotor of the multi-rotor platform. When the lift is greater than the gravity, the drone ascends; when the lift is less than the gravity, the drone descends. The pitch control generates a lift difference by controlling the different rotation speeds of the rotors in the front and rear rows of the multi-rotor platform, thereby generating a pitch torque around the center of mass of the UAV and adjusting the pitch attitude of the UAV. The roll control generates a roll torque around the center of mass by controlling the different rotation speeds of the rotors in the left and right rows of the multi-rotor platform, thereby adjusting the roll attitude of the UAV. The yaw control generates a yaw torque in the longitudinal plane by controlling the different rotation speeds of the two diagonally opposite rotors of the multi-rotor platform, causing them to rotate around the vertical axis, thereby adjusting the UAV's heading.

5. The multi-modal flight control method for a compound quadcopter UAV according to claim 1, wherein the fixed-wing mode part comprises: Fixed-wing climb phase: After the UAV enters fixed-wing mode, it climbs to the predetermined operating height using the fixed-wing platform; Fixed-wing cruise phase: After the UAV climbs to the predetermined operating altitude, it uses the fixed-wing platform to conduct cruise operations; as well as Fixed-wing dive phase: After completing the mission, the UAV uses the fixed-wing platform to dive to the predetermined switching altitude, preparing to switch to the transition mode.

6. The multi-modal flight control method for a compound quadcopter UAV according to claim 5, wherein the fixed-wing mode part realizes altitude control, pitch control, roll control, yaw control and horizontal speed control of the UAV by manipulating the engine, elevator, aileron and rudder of the fixed-wing platform, so that the UAV can realize climb, cruise and dive functions in fixed-wing mode.

7. The multi-modal flight control method for a compound quadcopter UAV according to claim 6, wherein: The altitude control and pitch control change the direction of aerodynamic drag on the elevator during the UAV's cruise flight by controlling the different deflection angles of the elevator surfaces of the fixed-wing platform, thereby generating a pitch moment around the UAV's center of mass and adjusting the UAV's pitch attitude and flight altitude. The roll control changes the direction of aerodynamic drag on the left and right wings of the UAV during cruise flight by controlling the different deflection angles of the aileron control surfaces of the fixed-wing platform, thereby generating a roll moment around the center of mass of the UAV and adjusting the roll attitude of the UAV. The yaw control changes the direction of aerodynamic drag on the rudder during the UAV's cruise flight by controlling the different deflection angles of the rudder on the fixed-wing platform, thereby generating a yaw moment around the UAV's center of mass and adjusting the UAV's heading. The horizontal speed control adjusts the flight speed of the UAV by changing the rotational speed of the engine on the fixed-wing platform.

8. The multi-modal flight control method for a compound quadcopter UAV according to claim 1, wherein the transition mode part achieves altitude control, pitch control, roll control, yaw control, and horizontal speed control of the UAV by manipulating the rotor speed of the multi-rotor platform and the engine, elevator, aileron, and rudder of the fixed-wing platform, so that the UAV can achieve a smooth transition in the transition mode.

9. The multi-modal flight control method for a compound quadcopter UAV according to claim 8, wherein: The altitude control adjusts the lift generated by changing the rotational speed of each rotor of the multi-rotor platform, thereby changing the magnitude of the resultant force in the vertical direction of the UAV and thus adjusting the altitude of the UAV. The pitch control includes: differential speed control of the front and rear rotors of the multi-rotor platform and adjustment of the deflection angle of the elevator surface of the fixed-wing platform; The roll control includes: differential control of the rotational speed of the left and right rotors of the multi-rotor platform and adjustment of the deflection angle of the aileron control surfaces of the fixed-wing platform; The yaw control includes: differential control of the rotor speed of the multi-rotor platform diagonally and adjustment of the rudder deflection angle of the fixed-wing platform; The horizontal speed control includes: individually changing the rotational speed of the engine on the fixed-wing platform, or simultaneously changing the rotational speed of the engine on the fixed-wing platform and the rotational speeds of the front and rear rotors on the multi-rotor platform.

10. The multi-modal flight control method for a compound quadcopter UAV according to any one of claims 1 to 9, wherein the multi-rotor mode cruise speed is between 3 m / s and 5 m / s.

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