Tilting multi-rotor unmanned aerial vehicle and tilting transition method

Abstract

The invention discloses a tilting multi-rotor unmanned aerial vehicle and a tilting transition method, and belongs to the technical field of unmanned aerial vehicles. The tilting multi-rotor unmanned aerial vehicle comprises a fuselage, wings are symmetrically arranged on the two sides of the fuselage, wingtip small wings with rudders are arranged at the tail ends of the wings, and front tilting mechanisms symmetrically arranged relative to the fuselage are arranged at the front end of the fuselage; rear tilting mechanisms which are symmetrically arranged relative to the fuselage are arranged at the rear end of the fuselage, and a propeller is arranged in the middle of the rear end of the fuselage; the front tilting mechanism comprises a front propeller, the front propeller is connected with the fuselage through a tilting power structure, the rear tilting mechanism comprises a rear propeller, and the rear propeller is connected with the fuselage through a tilting power structure. According to the tilting multi-rotor unmanned aerial vehicle and the tilting transition method, the fuselage layout is matched with the front tilting mechanism and the rear tilting mechanism, the flight stability is improved, and higher air maneuverability is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of unmanned aerial vehicles, and in particular to a tilt-rotating multi-rotor unmanned aerial vehicle and a tilt-rotating transition method. Background Art

[0002] At present, drones are mainly divided into rotary-wing drones and fixed-wing drones. Rotary-wing drones can take off and land vertically without relying on runways and other ground auxiliary facilities, and can adapt to a variety of take-off environments, but due to their short endurance and low flight speed, their use scenarios are subject to certain restrictions. Fixed-wing drones can fly at high speeds and long distances, but they need to rely on runways or ground launch and recovery equipment to assist in take-off and landing, which also limits their scope of application to a certain extent. Tilt-rotor drones combine the advantages of both. They can not only take off and land vertically, but also fly at high speeds and long distances. They can be used for short-distance transportation, medical rescue, aerial photography, agricultural plant protection, wildlife observation, surveying and mapping, power inspections, and aerial search and rescue. Therefore, tilt-rotor drones are regarded as one of the trends in the future development of drones.

[0003] Most of the power units of traditional vertical take-off and landing technologies shrink and fold after take-off, which causes power system redundancy and increases the weight of the drone. The existing conventional layout drones have a large wingtip effect, which affects the lift of the wing surface.

[0004] At present, the transition of traditional tilt-wing UAVs has high requirements for the flight control system. During the tilting process, the rotor is still relied on to provide lift. The flight attitude is difficult to control during the tilting process. In addition, the torsional load of the tilting mechanism is large, and the torsion rod is subjected to large stress. Once a problem occurs in the tilting mechanism, the flight cannot continue, and problems are very likely to occur during the transition process. Summary of the invention

[0005] The purpose of the present invention is to provide a tilt-rotating multi-rotor UAV and a tilt-rotating transition method to solve the problems raised in the above-mentioned background technology.

[0006] To achieve the above object, the present invention provides a tilt-rotating multi-rotor UAV, comprising a fuselage, wings symmetrically arranged on both sides of the fuselage, winglets with rudders arranged at the ends of the wings, a forward tilt-rotating mechanism symmetrically arranged with respect to the fuselage arranged at the front end of the fuselage, a rearward tilt-rotating mechanism symmetrically arranged with respect to the fuselage arranged at the rear end of the fuselage, and a propulsion propeller arranged in the middle of the rear end of the fuselage;

[0007] The front tilt mechanism includes a front propeller, which is connected to the fuselage through a tilt power structure, and the rear tilt mechanism includes a rear propeller, which is connected to the fuselage through a tilt power structure.

[0008] Preferably, a fuselage frame is provided inside the fuselage to play a supporting role.

[0009] Preferably, the rear end of the wing is provided with ailerons and flaps, the ailerons are used for the rolling maneuvers of the UAV, and the flaps are used for the take-off and landing of the UAV.

[0010] Preferably, a wing frame is arranged inside the wing, and the wing frame includes a main carbon fiber tube beam frame, an auxiliary carbon fiber tube beam frame and a plurality of wing ribs. The main carbon fiber tube beam frame and the auxiliary carbon fiber tube beam frame are respectively arranged along the length direction of the wing, and the wing ribs are arranged between the main carbon fiber tube beam frame and the auxiliary carbon fiber tube beam frame, and are arranged at intervals along the length direction of the wing.

[0011] Preferably, the rudder is arranged at the rear end of the winglet, and a winglet frame is arranged inside the winglet. The winglet frame includes winglet ribs and a winglet carbon fiber beam frame. The wingtip winglet carbon fiber beam frame is arranged along the length direction of the winglet, and the wingtip winglet ribs are arranged along the width direction of the winglet.

[0012] Preferably, the fuselage is provided with a tilt device fixing frame, the front propeller and the rear propeller are respectively connected to the tilt device fixing frame through a tilt power structure, and the front ends of the front propeller and the rear propeller are provided with fairings; the tilt power structure includes a tilt frame, a servo motor is provided on the mounting surface of the tilt frame, the output end of the servo motor is connected to the front propeller or the rear propeller, the frame plates on both sides of the tilt frame are connected to the box body through a tilt connection assembly, and the box body is connected to the tilt device fixing frame.

[0013] Preferably, the tilt connection assembly includes a worm gear arranged inside the box body, one end of the worm gear is connected to the output shaft of the tilt motor, a fixing box for fixing the tilt motor is provided inside the box body, the other end of the worm gear is rotatably connected to the box body through a bearing, the middle part of the worm gear is connected to the middle part of the tilt gear rod, and both ends of the tilt gear rod pass through the box body and are connected to the frame plates on both sides of the tilt frame.

[0014] Preferably, a front landing gear is provided at the front bottom end of the fuselage, a left landing gear and a right landing gear are symmetrically provided on both sides of the bottom of the fuselage, a flight control device, a mission payload and a battery are provided inside the fuselage, a propulsion motor is provided at the upper and rear end of the fuselage, an output shaft of the propulsion motor is connected to the propulsion propeller, and a displacement sensor, a phase sensor, an acceleration sensor and a gyroscope are integrated in the flight control device.

[0015] The present invention also provides a tilt transition method for a tilt multi-rotor UAV, comprising the following steps:

[0016] Step 1: perform signal processing in real time and in sequence: take the center of gravity of the drone as the coordinate origin O, take the chord direction of the drone as the x-axis, take the plane passing through the chord horizontal to the forward direction of the drone as the chord plane, take the direction perpendicular to the chord plane of the drone as the y-axis, and take the direction perpendicular to both the x-axis and the y-axis as the z-axis;

[0017] The acceleration sensor is used to obtain the x-axis acceleration u, y-axis acceleration v, and z-axis acceleration w of the drone. The gyroscope is used to obtain the pitch velocity ω3 and pitch angle θ3, roll velocity ω1, roll angle θ1, yaw velocity ω2, and yaw angle θ2 of the drone's flight state. The components F of the resultant force on the x-axis, y-axis, and z-axis of the drone during flight are calculated. x 、F y 、F z The sum of the rotor thrust and the flight aerodynamic force produces a pitching moment M3, a rolling moment M1, and a yaw moment M2; the front propeller and the rear propeller are the rotors;

[0018] By integrating the acceleration, we can further obtain the horizontal forward flight velocity V X , vertical speed V Y , yaw speed V Z ;

[0019] Step 2: Adjust the attitude of the drone according to the above calculations, and adjust the vertical speed V by adjusting the servo motors on the four tilting power structures. Y and the pitch moment M3, so that the UAV is flying forward at a speed V when it is not flying horizontally. X Tends to 0 until it reaches a flight altitude of 50m;

[0020] Step 3: According to the above flight process, after reaching 50m, start the propulsion motor and change the horizontal forward speed V of the drone by changing the thrust. X , as V X The speed of the servo motors on the four tilting power structures is gradually reduced, and the forward flight speed V X The change of lift is used to judge the change of the drone, and the flight control equipment controls the rudder on the winglet, the aileron on the wing and the speed of the servo motors on the four tilt-rotating power structures to adjust the balance of the drone in the y-axis and z-axis directions until the speed of the servo motors on the four tilt-rotating power structures drops to 0;

[0021] Step 4: Use the worm gear to drive the tilt-rotor frame to rotate, and then adjust the position of the front and rear propellers to make the UAV transition from a vertical state to a horizontal state. Restart the servo motors on the four tilt-rotor power structures through the flight control equipment, and drive the UAV to fly through a total of five power sources, two pulls and three pushes.

[0022] Preferably, in step 1, the following formula is used to calculate the flight parameters of the drone:

[0023] F x =F 推 +mgsin(θ3)+F 阻 cos(β);

[0024] Fy =F 升 +mgcos(θ3)+F 阻 sin(β);

[0025]

[0026] u=F x / m;

[0027] v=F y / m;

[0028] w=F z / m;

[0029] V X =∫ucos(θ3)+vsin(θ3)dt;

[0030] V Y =∫u sin(θ3)+vcos(θ3)dt;

[0031] V Z =∫w cos(θ1)+v sin(θ1)dt;

[0032]

[0033] H=∫V Y dt;

[0034]

[0035]

[0036] Among them, M 偏 is the yaw moment, F x 、F y 、F z They represent the components of the resultant force on the x-axis, y-axis, and z-axis of the vertical takeoff and landing of the UAV. The angles in the trigonometric functions in the above formulas are all implicit functions. 推 F is the thrust of the drone along the chord direction; 升 is the lift in the direction perpendicular to the chord plane; F 阻 is the actual flow direction resistance, angle β is the angle between the actual flow direction and the chord, I1, I2, and I3 are the moments of inertia of the body on the x-axis, y-axis, and z-axis respectively. For drones in V X The amount of advance in the direction, H is the distance of the drone in V Y The amount of advance in a certain direction is the flight altitude. For drones in V Z The amount of progress in the direction, yes and The sum of The modulus represents the actual flight distance; R is the projection of the actual distance between the wing lift center and the center of gravity on the x-axis. The lift center of the drone is on the negative half of the x-axis;

[0037] In step 2, the propulsion motor is not started, and the component of the combined force on the y-axis of the vertical take-off and landing of the UAV other than gravity is the gravity mg and the downward resistance F 阻 The sum of the vertical acceleration v of the drone at this time is obtained, and the formula is as follows:

[0038] F 阻 = kV Y 2 ;

[0039] F y =mg+kV Y 2 ;

[0040]

[0041] Where m is the mass of the fuselage and k represents the drag constant;

[0042] According to the Newton-Euler method in classical mechanics, a suitable dynamic mathematical model is constructed:

[0043]

[0044] In the above formula, the control of the drone depends on the roll Pitch and yaw Angular velocity and its influence on attitude. The front and rear propellers are propellers of the same structure. The propeller speed Ω(t) = -Ω1(t) + Ω2(t) -Ω3(t) + Ω4(t), which determines the lift and torque. The driving torque T1(t), T2(t), and T3(t) determine the horizontal, vertical movement and steering of the drone. The moment of inertia I R Reflects the propeller's anti-rotation capability;

[0045] According to the above dynamic mathematical model, in step 2, the rotation speeds of the two front propellers and the two rear propellers Ω1(t), Ω2(t), Ω3(t), Ω4(t) are adjusted, and the flight attitude is adjusted by changing the rotation speeds of the front propellers and the rear propellers;

[0046] In step 3, the propulsion motor is started, the speed of the servo motor is finally 0, and the lift force on the drone is gravity. The horizontal flight speed V of the drone is obtained at this time. X , the formula is as follows:

[0047] F 升 = mg;

[0048]

[0049] Where ρ is the atmospheric density, S is the wing area, C y is the lift coefficient, and the (β) in cos(β) is the implicit function of the β angle with respect to time t.

[0050] Therefore, the present invention adopts the above-mentioned tilt-rotor multi-rotor UAV and tilt-rotor transition method, which has the following beneficial effects:

[0051] (1) The present invention can smoothly transition the take-off process. During the tilting process of the UAV, the front propeller and the rear propeller do not rotate, which greatly reduces the stress of the tilting link of the tilt-rotor UAV, which has the highest failure rate, thereby greatly reducing the failure rate of the tilting mechanism. At the same time, the design of driving the gear to rotate by rotating the worm structure has a self-locking effect, and the tilting process will not be affected by disturbances before and after the tilting.

[0052] (2) Compared with traditional UAVs, it has an additional power source, has a stronger load-bearing capacity and a longer range, and improves the reliability of the aircraft in level flight. If a propeller fails during level flight, it can be handled by the cooperation of other propellers. For example, if the left front propeller fails, the yaw moment can be balanced by turning off the right front propeller and the UAV can be controlled through the two rear tilt propellers and propulsion motors to continue to complete the flight mission.

[0053] (3) The present invention uses two front propellers and two rear propellers to enable the UAV to have both vertical take-off and landing and horizontal take-off and landing methods. When there is a runway, the UAV can choose the horizontal take-off and landing method with less energy consumption, and the load capacity is greatly increased. Compared with traditional UAVs, it can achieve high-speed level flight and has stronger aerial maneuverability.

[0054] (4) The present invention sets a rudder at the wingtip winglet, which can correct the disturbance of the UAV without a tail wing. Not only can the flight attitude be adjusted by adjusting the speed of the front propeller and the two rear propellers, but the flight attitude can also be corrected by the wingtip rudder surface, thereby improving the flight stability. The wingtip winglet design can effectively reduce and alleviate the wingtip effect and ensure that the wingtip lift loss is small.

[0055] (5) The present invention adopts a tailless design and unique forward tilting mechanism and rear tilting mechanism. Compared with the traditional tilting UAV that tilts the entire wing surface, the wing area is reduced, and the geometric cross-sectional area is reduced, so that the aircraft has a lower radar cross-sectional area, which is beneficial to stealth performance, reduces the possibility of being detected by the enemy, and has a good stealth effect.

[0056] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 It is a schematic diagram of the overall structure of an embodiment of the present invention;

[0058] Figure 2 This is a diagram of the internal structure of a drone according to an embodiment of the present invention;

[0059] Figure 3 A top view of an embodiment of the present invention;

[0060] Figure 4 A schematic diagram of a forward tilting mechanism according to an embodiment of the present invention;

[0061] Figure 5 This is a schematic diagram of the wing skeleton structure of an embodiment of the present invention;

[0062] Figure 6 A schematic diagram of a coordinate axis established in an embodiment of the present invention;

[0063] Figure 7 The figure is a schematic diagram of a method flow of an embodiment of the present invention.

[0064] Reference numerals

[0065] 1. Fuselage; 11. Tilt device fixing frame; 12. Fuselage frame; 2. Wing; 21. Main carbon fiber tube beam frame; 22. Auxiliary carbon fiber tube beam frame; 23. Aileron; 24. Flaps; 25. Wing ribs; 26. Winglet; 261. Winglet ribs; 262. Winglet carbon fiber beam frame; 263. Rudder; 3. Forward tilt mechanism; 31. Tilt motor; 32. Worm; 33. Tilt gear rod; 34. Bearing; 35. Fairing; 36. Fixing box; 37. Tilt frame; 38. Front propeller; 39. Servomotor; 310. Rear propeller; 4. Rear tilt mechanism; 5. Propulsion motor; 6. Front landing gear; 7. Left landing gear; 8. Right landing gear; 9. Flight control equipment; 10. Battery; 20. Mission payload. DETAILED DESCRIPTION

[0066] In order to make the purpose, technical scheme and advantages disclosed in the embodiments of the present invention clearer, the embodiments of the present invention are further described in detail in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the embodiments of the present invention and are not intended to limit the embodiments of the present invention. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions.

[0067] It should be noted that the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or server that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units that are not explicitly listed or inherent to these processes, methods, products or devices.

[0068] Like reference numerals and letters denote similar items in the following drawings, and thus, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0069] In the description of the present invention, it should be noted that the terms "upper", "lower", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, or are directions or positional relationships in which the product of the invention is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0070] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "setting", "installation" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0071] Example

[0072] like Figure 1 As shown, the tilt-rotor multi-rotor UAV of the present invention comprises a fuselage 1, and wings 2 are symmetrically arranged on both sides of the fuselage 1. Figure 2 , Figure 6 As shown, a supporting fuselage frame 12 is arranged inside the fuselage 1, and an aileron 23 and a flap 24 are arranged at the rear end of the wing 2. The aileron 23 is used for the rolling maneuver of the UAV, and the flap 24 is used for the take-off and landing of the UAV.

[0073] like Figure 2 , Figure 5 As shown, a wing frame is arranged inside the wing 2, and the wing frame includes a main carbon fiber tube beam frame 21, an auxiliary carbon fiber tube beam frame 22, and a plurality of wing ribs 25. The main carbon fiber tube beam frame 21 and the auxiliary carbon fiber tube beam frame 22 are arranged along the length direction of the wing 2, respectively, and the wing ribs 25 are arranged between the main carbon fiber tube beam frame 21 and the auxiliary carbon fiber tube beam frame 22, and are arranged at intervals along the length direction of the wing 2.

[0074] A winglet 26 with a rudder 263 is provided at the end of the wing 2. The rudder 263 is provided at the rear end of the winglet 26. A winglet frame is provided inside the winglet 26. The winglet frame includes a winglet rib 261 and a winglet carbon fiber beam frame 262. The winglet carbon fiber beam frame 262 is provided along the length direction of the winglet 26. The winglet rib 261 is provided along the width direction of the winglet 26.

[0075] like Figure 1 , Figure 3 , Figure 4 As shown, a front tilt mechanism 3 symmetrically arranged with respect to the fuselage 1 is provided on the front end of the fuselage 1, and a rear tilt mechanism 4 symmetrically arranged with respect to the fuselage 1 is provided on the rear end of the fuselage 1. The front tilt mechanism 3 includes two front propellers 38 symmetrically arranged with respect to the fuselage 1, and the front propellers 38 are connected to the fuselage 1 through a tilt power structure. The rear tilt mechanism 4 includes two rear propellers 310 symmetrically arranged with respect to the fuselage 1, and the rear propellers 310 are connected to the fuselage 1 through a tilt power structure. The fuselage 1 is provided with a tilt device fixing frame 11, and the front propellers 38 and the rear propellers 310 are respectively connected to the tilt device fixing frame 11 through the tilt power structure. A fairing 35 is provided at the front ends of the front propellers 38 and the rear propellers 310. The tilt power structure includes a tilt frame 37, a servo motor 39 is arranged on the mounting surface of the tilt frame 37, the output end of the servo motor 39 is connected to the front propeller 38 or the rear propeller 310, and the frame plates on both sides of the tilt frame 37 are connected to the box body through the tilt connection assembly, and the box body is connected to the tilt device fixing frame 11. The tilt connection assembly includes a worm 32 arranged inside the box body, one end of the worm 32 is connected to the output shaft of the tilt motor 31, and the other end of the worm 32 is rotatably connected to the box body through a bearing 34. A fixing box 36 for fixing the tilt motor 31 is arranged inside the box body. The middle part of the worm 32 is connected to the middle part of the tilt gear rod 33, and the two ends of the tilt gear rod 33 pass through the box body and are connected to the frame plates on both sides of the tilt frame 37. The two ends of the tilt gear rod 33 are connected to the box body through bearings 34.

[0076] A front landing gear 6 is provided at the bottom front end of the fuselage 1, a left landing gear 7 and a right landing gear 8 are symmetrically provided at both sides of the bottom of the fuselage 1, a flight control device 9, a mission payload 20 and a battery 10 are provided inside the fuselage 1, a propulsion motor 5 is provided at the upper rear end of the fuselage 1, and the output shaft of the propulsion motor 5 is connected to the propulsion propeller in the middle of the upper rear end of the fuselage 1. The flight control device 9 integrates a displacement sensor, a phase sensor, an acceleration sensor, a gyroscope, etc.

[0077] The flight control device 9 and the mission payload 20 adopt the conventional configuration of existing drones. The battery 10, the propulsion motor 5, the tilting motor 31, the servo motor 39 and other electric control components on the drone are electrically connected to the flight control device 9 using the existing structure.

[0078] The front propeller 38 and the rear propeller 310 of the drone can be driven to rotate by the servo motor 39. The tilt motor 31 can drive the tilt frame 37 to rotate through the worm 32 and the tilt gear rod 33, thereby realizing that each of the two front propellers 38 and the two rear propellers 310 can adjust the tilt angle separately.

[0079] like Figure 7 As shown, the tilt transition method of a tilt multi-rotor UAV described in the present invention comprises the following steps:

[0080] Step 1: Process the signal in real time and sequentially: Figure 6 As shown, the center of gravity of the UAV is the coordinate origin O, the direction of the UAV chord is the x-axis, the plane passing through the chord and horizontal to the forward direction of the UAV is the chord plane, the direction perpendicular to the UAV chord plane is the y-axis, and the direction perpendicular to both the x-axis and the y-axis is the z-axis.

[0081] The acceleration sensor is used to obtain the x-axis acceleration u, y-axis acceleration v, and z-axis acceleration w of the drone. The gyroscope is used to obtain the pitch velocity ω3 and pitch angle θ3, roll velocity ω1, roll angle θ1, yaw velocity ω2, and yaw angle θ2 of the drone's flight state. Calculate the components F of the resultant force on the x-axis, y-axis, and z-axis of the drone during flight. x 、F y 、F z The sum of the thrust of the rotors (the front propeller 38 and the rear propeller 310) and the flight aerodynamic force generates a pitch resultant moment M3, a roll resultant moment M1, and a yaw resultant moment M2.

[0082] By integrating the acceleration, we can further obtain the horizontal forward flight velocity V X , vertical speed V Y , yaw speed V Z .

[0083] In step 1, the following formula is used to calculate the flight parameters of the drone:

[0084] F x =F 推 +mgsin(θ3)+F 阻 cos(β);

[0085] F y =F 升 +mgcos(θ3)+F 阻 sin(β);

[0086]

[0087] u=F x / m;

[0088] v=F y / m;

[0089] w=F z / m;

[0090] V X =∫ucos(θ3)+vsin(θ3)dt;

[0091] V Y =∫usin(θ3)+vcos(θ3)dt;

[0092] V Z =∫wcos(θ1)+vsin(θ1)dt;

[0093]

[0094]

[0095] H=∫V Y dt;

[0096]

[0097] Among them, M 偏 is the yaw moment, F x 、F y 、F z They represent the components of the resultant force on the vertical take-off and landing of the UAV on the x-axis, y-axis, and z-axis respectively. The angles in the trigonometric functions in the above formulas are all implicit functions, and their function values ​​change with time. Therefore, they should be processed as implicit function integrals when performing integration. 推 F is the thrust of the drone along the chord direction (x axis); 升 is the lift in the direction perpendicular to the chord plane (y axis); F 阻 is the actual flow direction resistance, β angle is the angle between the actual flow direction and the chord (flight angle of attack), I1, I2, I3 are the moments of inertia of the aircraft on the x-axis, y-axis, and z-axis respectively, For drones in V X The amount of advance in the direction, H is the distance of the drone in V Y The amount of advance in a certain direction is the flight altitude. For drones in V Z The amount of progress in the direction, yes and The sum of The modulus represents the actual flight distance; R is the projection of the actual distance between the lift center and the center of gravity of wing 2 on the x-axis. In this drone, the lift center is on the negative half axis of the x-axis, that is, the lift center is closer to the tail than the center of gravity. When the flap 24 is adjusted, the relative positions of the lift center and the center of gravity are not changed.

[0098] Step 2: Adjust the attitude of the drone according to the above calculation, and adjust the vertical speed V by adjusting the servo motors 39 on the four tilting power structures. Y and the pitch moment M3, so that the UAV is not flying horizontally, the forward flight speed V X It tends to 0 until it reaches a flight altitude of 50m.

[0099] In step 2, the propulsion motor 5 is not started, and the component of the resultant force on the y-axis of the vertical take-off and landing of the UAV other than gravity is the gravity mg and the downward resistance F 阻 The sum of the vertical acceleration v of the drone at this time is obtained, and the formula is as follows:

[0100] F 阻 = kV Y 2 ;

[0101] F y =mg+kV Y 2 ;

[0102]

[0103] Where m is the mass of the fuselage 1, and k represents the drag constant;

[0104] According to the Newton-Euler method in classical mechanics, a suitable dynamic mathematical model is constructed:

[0105]

[0106] In the above formula, the control of the drone depends on the roll Pitch and yaw Angular velocity, and its influence on attitude. The front propeller 38 and the rear propeller 310 are propellers of the same structure. The propeller speed Ω(t) = -Ω1(t) + Ω2(t) -Ω3(t) + Ω4(t), which determines the lift and torque. The driving torque T1(t), T2(t), and T3(t) determine the horizontal, vertical movement and steering of the drone. The moment of inertia I R Reflects the propeller's ability to resist rotation, and I1, I2, and I3 are the body's moments of inertia on the x-axis, y-axis, and z-axis, respectively. These factors together determine the UAV's dynamic characteristics and responsiveness, especially when maneuvering quickly or fighting wind resistance.

[0107] According to the above dynamic mathematical model, in step 2, the rotation speeds Ω1(t), Ω2(t), Ω3(t), and Ω4(t) of the two front propellers 38 and the two rear propellers 310 are adjusted, and the flight attitude is adjusted by changing the rotation speeds of the front propellers 38 and the rear propellers 310. By changing the propeller rotation speed, the balance of the left and right front and rear torques of the drone can be achieved; at the same time, the rotation speed of the servo motor 39 is further changed synchronously on the basis of changing the rotation speed so that the drone can obtain a vertical acceleration v, so as to achieve the purpose of gradually raising the drone.

[0108] In this process, the propulsion motor 5 is not started, and the whole is in a vertical take-off and landing state. In addition to the disturbance, the forward flight acceleration u and the horizontal flight speed V X The pitch angle θ3 and the roll angle θ1 are also as close to 0 as possible after control and adjustment.

[0109] Step 3: According to the above flight process, after reaching 50m, start the propulsion motor 5, and change the horizontal forward flight speed V of the drone by changing the thrust. X , as V X The lift of the wing 2 increases accordingly, and the rotation speed of the servo motor 39 on the four tilting power structures is gradually reduced, and the forward flight speed V in the horizontal direction of the flight is increased. X The change in lift of the UAV is determined by the change in the lift of the UAV. The flight control device 9 controls the rudder 263 on the winglet 26, the aileron 23 on the wing 2, and the rotation speed of the servo motors 39 on the four tilting power structures to adjust the balance of the UAV in the y-axis and z-axis directions until the rotation speed of the servo motors 39 on the four tilting power structures drops to 0.

[0110] There is a difference between the above-mentioned step 2 process and step 3 process. In this process, as the propulsion motor 5 is started, the lift gradually changes from being provided entirely by the propeller to being provided by part of the propeller and part of the wing 2 surface, so that the control and power of the drone will also change accordingly.

[0111] In step 3, the propulsion motor 5 is started, the speed of the servo motor 39 is finally 0, and the lift force on the drone is gravity. The horizontal flight speed V of the drone is obtained at this time. X , the formula is as follows:

[0112] F 升 = mg;

[0113]

[0114] Where ρ is the atmospheric density, S is the area of ​​wing 2, C y is the lift coefficient, and the (β) in cos(β) is the implicit function of the β angle (flight angle of attack) with respect to time t.

[0115] Step 4: The worm gear 32 drives the tilt frame 37 to rotate, thereby adjusting the positions of the front propeller 38 and the rear propeller 310 to make the UAV transition from a vertical state to a horizontal state. The servo motors 39 on the four tilt power structures are restarted through the flight control device 9, and the UAV is driven to fly through a total of five power sources, namely, two pulls and three pushes.

[0116] In the above steps, the transition balance controller adopts a PID controller, wherein the tilt motor 31, the servo motor 39, and the rudder 263 are all controlled by the PID strategy. Real-time compensation is performed for the control signal vibration caused by the transition switching of the tilt-wing UAV, and the above method can suppress the signal jitter caused by the switching. The UAV of the present invention has three modes, namely vertical take-off and landing mode, transition flight mode and cruise flight mode, as follows:

[0117] Vertical take-off and landing mode: before flight, during vertical take-off and landing, the four-propeller output shaft is perpendicular to the longitudinal axis y of the drone to provide sufficiently large lift, that is, perpendicular to the ground. When the drone rises vertically, the lift of the drone is generated by the four tilt-rotor propellers (two front propellers 38 and two rear propellers 310). The pitch stability of the drone is achieved by PID controlling the y-axial thrust difference of the two front and rear groups of two tilt motors 31 of the four tilt-rotor propellers. The roll stability control is achieved by PID controlling the y-axial thrust difference of the two left and right groups of two tilt motors 31 of the tilt-rotor propellers.

[0118] The heading control of the UAV is achieved by controlling the rotation speed direction of the four-propeller diagonal servo motors 39, that is, one group of diagonal servo motors 39 reduces the rotation speed, and the other group of diagonal servo motors 39 increases the rotation speed to cause z-axis torque and compensate for lift at the same time.

[0119] Transition flight mode: After the drone takes off vertically and reaches the specified height of 50m, it enters the transition flight mode, the propulsion motor 5 is started, the four tilt-rotor propellers do not tilt, and the propeller thrust direction is still kept as the Y axis. The drone generates X-axis acceleration and speed, and at the same time, the wing 2 begins to gradually provide lift, and the four tilt-rotor motors 31 gradually decelerate to complete the transition of the lift source. At this time, the pitch stability of the drone is adjusted by PID controlling the left and right flaps 24 of the drone to adjust the lift size of the wing 2, and at the same time, the pitch moment is formed with the lift center of the four-rotor propeller (the lift center of the four-rotor propeller coincides with the center of gravity of the drone), thereby dynamically adjusting the pitch angle. The rolling stability of the drone is obtained by PID controlling the left and right ailerons 23 of the drone to obtain the torque of the x-axis in the flight direction, thereby dynamically adjusting the rolling angle. The heading stability of the drone is obtained by PID controlling the left and right winglets of the drone to obtain the torque in the normal direction of the wing 2, thereby dynamically adjusting the heading angle.

[0120] In the transition flight mode, the quadrotor tilt motor 31 simultaneously executes the PID control program of the vertical take-off and landing mode, so that in the entire transition flight mode, the stability control of the drone in all directions is hyperstatically stable. In the transition flight mode, the early lift of the drone mainly comes from the four tilt rotor propellers.

[0121] Then the PID stabilization control effect of the four-tilt-rotor is better than the PID stabilization control of wing 2, that is, the PID stabilization control of the four-tilt-rotor is the main stabilization control, and the PID stabilization control of wing 2 is the auxiliary stabilization control; the lift of the UAV in the later stage mainly comes from wing 2, then the PID stabilization control of wing 2 is better than the PID stabilization control effect of the four-tilt-rotor, that is, the PID stabilization control of wing 2 is the main stabilization control, and the PID stabilization control of the four-tilt-rotor is the auxiliary stabilization control; in this way, the transition flight mode completes the transition of the UAV lift source, and also completes the transition of the UAV stability control.

[0122] Cruise flight mode: After the UAV completes the transition flight mode, the wing 2 provides all the lift, and the four-tilt rotor propeller no longer rotates. At this time, the tilt frame 37 is driven to rotate by the rotation of the worm gear, so that the thrust direction of the four-tilt rotor propeller is the same as that of the propulsion motor 5, which is the X-axis of the UAV flight direction. After the tilt is completed, the four-rotor tilt motor 31 is started, and the propulsion motor 5 and the four-tilt motor 31 jointly provide thrust in the X-axis direction, thereby completing the thrust distribution.

[0123] In cruise flight mode, the PID stability control system of the four tilt-rotor propellers is no longer in operation, and the Wing 2 PID stability control manages the overall stability control of the drone.

[0124] Assuming that disturbances are encountered, the two flight control systems 9 are used to adjust the lift of the aircraft to ensure its flight stability. The two flight control systems are fixed-wing and four-tilt-rotor propellers. The fixed-wing refers to the wing structure, which is mainly controlled by adjusting the flaps 24, ailerons 23 and the rudders on the wingtip winglets 26. The lift size is changed by adjusting the propeller speed, so that the lift difference brought by the four power sources is used to adjust the flight attitude.

[0125] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A tilt-rotor multi-rotor UAV, characterized in that: The aircraft comprises a fuselage, wings are symmetrically arranged on both sides of the fuselage, winglets with rudders are arranged at the ends of the wings, a forward tilting mechanism symmetrically arranged about the fuselage is arranged at the front end of the fuselage, a backward tilting mechanism symmetrically arranged about the fuselage is arranged at the rear end of the fuselage, and a propulsion propeller is arranged in the middle of the rear end of the fuselage; The front tilt mechanism includes a front propeller, which is connected to the fuselage through a tilt power structure, and the rear tilt mechanism includes a rear propeller, which is connected to the fuselage through a tilt power structure.

2. The tilt-rotor multi-rotor UAV according to claim 1, characterized in that: A supporting fuselage frame is arranged inside the fuselage.

3. The tilt-rotor multi-rotor UAV according to claim 1, characterized in that: The rear end of the wing is equipped with ailerons and flaps. The ailerons are used for the rolling maneuvers of the UAV, and the flaps are used for the take-off and landing of the UAV.

4. The tilt-rotor multi-rotor UAV according to claim 1, characterized in that: A wing frame is arranged inside the wing, and the wing frame includes a main carbon fiber tube beam frame, an auxiliary carbon fiber tube beam frame and a plurality of wing ribs. The main carbon fiber tube beam frame and the auxiliary carbon fiber tube beam frame are respectively arranged along the length direction of the wing, and the wing ribs are arranged between the main carbon fiber tube beam frame and the auxiliary carbon fiber tube beam frame, and are arranged at intervals along the length direction of the wing.

5. The tilt-rotor multi-rotor UAV according to claim 1, characterized in that: The rudder is arranged at the rear end of the winglet. A winglet frame is arranged inside the winglet. The winglet frame includes winglet ribs and a winglet carbon fiber beam frame. The winglet carbon fiber beam frame is arranged along the length direction of the winglet, and the winglet ribs are arranged along the width direction of the winglet.

6. The tilt-rotor multi-rotor UAV according to claim 1, characterized in that: The fuselage is provided with a tilt device fixing frame, the front propeller and the rear propeller are respectively connected to the tilt device fixing frame through the tilt power structure, and the front ends of the front propeller and the rear propeller are provided with fairings; the tilt power structure includes a tilt frame, a servo motor is provided on the mounting surface of the tilt frame, the output end of the servo motor is connected to the front propeller or the rear propeller, the frame plates on both sides of the tilt frame are connected to the box body through the tilt connection assembly, and the box body is connected to the tilt device fixing frame.

7. The tilt-rotor multi-rotor UAV according to claim 1, characterized in that: The tilt connection assembly includes a worm gear arranged inside the box body, one end of the worm gear is connected to the output shaft of the tilt motor, a fixing box for fixing the tilt motor is arranged inside the box body, the other end of the worm gear is rotatably connected to the box body through a bearing, the middle part of the worm gear is connected to the middle part of the tilt gear rod, and both ends of the tilt gear rod pass through the box body and are connected to the frame plates on both sides of the tilt frame.

8. The tilt-rotor multi-rotor UAV according to claim 1, characterized in that: A front landing gear is provided at the front bottom end of the fuselage, and a left landing gear and a right landing gear are symmetrically provided on both sides of the bottom of the fuselage. Flight control equipment, mission payload and batteries are provided inside the fuselage. A propulsion motor is provided at the upper and rear end of the fuselage. The output shaft of the propulsion motor is connected to the propulsion propeller. The flight control equipment is integrated with a displacement sensor, a phase sensor, an acceleration sensor and a gyroscope.

9. A tilt transition method for a tilt multi-rotor UAV according to any one of claims 1 to 8, characterized in that: The following steps are involved: Step 1: Perform signal processing in real time and in sequence: take the center of gravity of the drone as the coordinate origin 0, take the direction of the drone string as the x-axis, take the plane passing through the string and horizontal to the forward direction of the drone as the string plane, take the direction perpendicular to the drone string plane as the y-axis, and take the direction perpendicular to both the x-axis and the y-axis as the z-axis; The acceleration sensor is used to obtain the x-axis acceleration u, y-axis acceleration v, and z-axis acceleration w of the drone. The gyroscope is used to obtain the pitch velocity ω3 and pitch angle θ3, roll velocity ω1, roll angle θ1, yaw velocity ω2, and yaw angle θ2 of the drone's flight state. The components F of the resultant force on the x-axis, y-axis, and z-axis of the drone during flight are calculated. x 、F y 、F z The sum of the rotor thrust and the flight aerodynamic force produces a pitching moment M3, a rolling moment M1, and a yaw moment M2; the front propeller and the rear propeller are the rotors; By integrating the acceleration, we can further obtain the horizontal forward flight velocity V X , vertical speed V Y , yaw speed V Z ; Step 2: Adjust the attitude of the drone according to the above calculations, and adjust the vertical speed V by adjusting the servo motors on the four tilting power structures. Y and the pitch moment M3, so that the UAV is flying forward at a speed V when it is not flying horizontally. X Tends to 0 until it reaches a flight altitude of 50m; Step 3: According to the above flight process, after reaching 50m, start the propulsion motor and change the horizontal forward speed V of the drone by changing the thrust. X , as V X The speed of the servo motors on the four tilting power structures is gradually reduced, and the forward flight speed V in the horizontal direction is increased. X The change of lift is used to judge the change of the drone, and the flight control equipment controls the rudder on the winglet, the aileron on the wing and the speed of the servo motors on the four tilt-rotating power structures to adjust the balance of the drone in the y-axis and z-axis directions until the speed of the servo motors on the four tilt-rotating power structures drops to 0; Step 4: Use the worm gear to drive the tilt-rotor frame to rotate, and then adjust the position of the front and rear propellers to make the UAV transition from a vertical state to a horizontal state. Restart the servo motors on the four tilt-rotor power structures through the flight control equipment, and drive the UAV to fly through a total of five power sources, two pulls and three pushes.

10. The tilt transition method of a tilt multi-rotor UAV according to claim 9, characterized in that: In step 1, the following formula is used to calculate the flight parameters of the drone: F x =F 推 +mgsin(θ3)+F 阻 cos(β); F y =F 升 +mgcos(θ3)+F 阻 sin(β); u=F x / m; v=F y / m; w=F z / m; V X =∫u cos(θ3)+v sin(θ3)dt; V Y =∫u sin(θ3)+v cos(θ3)dt; V Z =∫w cos(θ1)+v sin(θ1)dt; H=∫V Y dt; Among them, M 偏 is the yaw moment, F x 、F y 、F z They represent the components of the resultant force on the x-axis, y-axis, and z-axis of the vertical takeoff and landing of the UAV. The angles in the trigonometric functions in the above formulas are all implicit functions. 推 F is the thrust of the drone along the chord direction; 升 is the lift in the direction perpendicular to the chord plane; F 阻 is the actual flow direction resistance, angle β is the angle between the actual flow direction and the chord, I1, I2, and I3 are the moments of inertia of the body on the x-axis, y-axis, and z-axis respectively. For drones in V X The amount of advance in the direction, H is the distance of the drone in V Y The amount of progress in the direction, For drones in V Z The amount of progress in the direction, yes and The sum of The modulus represents the actual flight distance; R is the projection of the actual distance between the wing lift center and the center of gravity on the x-axis. The lift center of the drone is on the negative half of the x-axis; In step 2, the propulsion motor is not started, and the total force other than gravity on the vertical take-off and landing of the UAV is y The components on the axis are gravity mg and the downward resistance F 阻 The sum of the vertical acceleration v of the drone at this time is obtained, and the formula is as follows: F 阻 =kV Y 2 ; F y =mg+kV Y 2 ; Where m is the mass of the fuselage and k represents the drag constant; According to the Newton-Euler method in classical mechanics, a suitable dynamic mathematical model is constructed: In the above formula, the drone control depends on the roll Pitch and yaw Angular velocity and its influence on attitude. The front and rear propellers are propellers of the same structure. The propeller speed Ω(t) = -Ω1(t) + Ω2(t) -Ω3(t) + Ω4(t), which determines the lift and torque. The driving torque T1(t), T2(t), and T3(t) determine the horizontal, vertical movement and steering of the drone. The moment of inertia I R Reflects the propeller's anti-rotation capability; According to the above dynamic mathematical model, in step 2, the rotation speeds of the two front propellers and the two rear propellers Ω1(t), Ω2(t), Ω3(t), Ω4(t) are adjusted, and the flight attitude is adjusted by changing the rotation speeds of the front propellers and the rear propellers; In step 3, the propulsion motor is started, the speed of the servo motor is finally 0, and the lift force on the drone is gravity. The horizontal flight speed V of the drone is obtained at this time. X , the formula is as follows: F 升 =mg; Where ρ is the atmospheric density, S is the wing area, C v is the lift coefficient, and the (β) in cos(β) is the implicit function of the β angle with respect to time t.

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