A multi-rotor low altitude aircraft power system

Abstract

This utility model discloses a multi-rotor low-altitude aircraft power system, including at least one fuel engine connected to a gearbox, and the gearbox connected to multiple closed-loop hydraulic transmission circuits. Each closed-loop hydraulic transmission circuit includes a hydraulic variable pump, a hydraulic motor, and a displacement control device. The gearbox is connected to the hydraulic variable pump, then connected to the hydraulic motor via a high-pressure oil pipe, and then returned to the hydraulic variable pump via a low-pressure oil pipe. The displacement control device is connected to the hydraulic variable pump to adjust its displacement. It also includes multiple rotors, with each hydraulic motor and rotor connected sequentially. An onboard control unit independently controls each displacement control device. This multi-rotor low-altitude aircraft power system uses a fuel engine as its power source, and its output power can be precisely distributed to multiple rotors, achieving independent stepless speed regulation of multiple rotors, ensuring stable flight of the low-altitude aircraft, and significantly improving endurance and payload capacity.

Description

Technical Field

[0001] This utility model relates to the technical field of aviation power, specifically a power system for a multi-rotor low-altitude aircraft. Background Technology

[0002] Traditional low-altitude aircraft (with a true altitude typically below 1000 meters and a maximum of no more than 3000 meters) are mostly electric vertical takeoff and landing (eVTOL) aircraft. To achieve vertical takeoff and landing and ensure flight stability, eVTOL aircraft mostly use multi-rotors. The pitch of the multi-rotor is fixed, and the flight attitude is controlled by adjusting the speed and thrust of each rotor. There is no pitch-changing mechanism for the main rotor, which provides better handling and reliability than traditional single-rotor (excluding tail rotor) helicopters.

[0003] Electric vertical takeoff and landing (EVTOL) aircraft use electric drive, which solves the problems of power distribution and independent control of each rotor, as well as stepless speed and torque conversion, and achieves stable flight. However, due to the low energy density of the power battery, their range is generally insufficient, resulting in low practical and economic value.

[0004] When an aircraft uses fuel power, increasing the fuel tank capacity and the amount of fuel carried can increase its range. However, this raises the question of how to distribute the output power of the fuel engine among multiple rotors, and how to achieve independent stepless speed and torque regulation for each rotor. This problem has long remained unresolved, limiting the development of fuel-powered multi-rotor aircraft.

[0005] Therefore, the aforementioned technical problems need to be solved. Utility Model Content

[0006] This utility model addresses the above-mentioned technical problems by providing a multi-rotor low-altitude aircraft power system. It uses a fuel engine as the power source, and its output power can be precisely distributed to multiple rotors, enabling independent stepless speed and torque regulation of multiple rotors to ensure the stable flight of the low-altitude aircraft. At the same time, it significantly improves the endurance and payload capacity of the low-altitude aircraft.

[0007] To achieve the above objectives, the technical solution of this utility model is as follows:

[0008] A power system for a multi-rotor low-altitude aircraft includes at least one fuel engine connected to a gearbox, the gearbox being connected to at least one closed hydraulic transmission circuit;

[0009] Each of the closed hydraulic transmission circuits includes a hydraulic variable pump, a hydraulic motor, and a displacement control device. The gearbox is connected to the hydraulic variable pump. The hydraulic variable pump is connected to the hydraulic motor via a high-pressure oil pipe and then returns to the hydraulic variable pump via a low-pressure oil pipe. The displacement control device is connected to the hydraulic variable pump to adjust its displacement.

[0010] It also includes multiple rotors, each of which is connected in sequence to a hydraulic motor and a rotor;

[0011] It also includes an airborne control unit and a heading and attitude sensor, wherein the airborne control unit acquires data from the heading and attitude sensor to independently control each of the displacement control devices.

[0012] The power system of this multi-rotor low-altitude aircraft uses a fuel engine as its power source. Increasing the fuel tank capacity and carrying more fuel will increase the range, significantly improving the endurance of the low-altitude aircraft.

[0013] The internal combustion engine drives a hydraulic variable pump via a gearbox. The hydraulic variable pump drives a hydraulic motor through a closed hydraulic circuit. The hydraulic motor drives the rotor to rotate, thus distributing the output power of the internal combustion engine to each rotor. The displacement of the hydraulic variable pump is controlled by a displacement control device, which precisely, independently, and steplessly controls the rotational speed and torque of each rotor, thereby accurately controlling the lift generated by the rotor and ensuring the stable flight of the low-altitude aircraft. This effectively solves the problem of independent stepless speed and torque regulation of multiple rotors.

[0014] A further optimized design incorporates a servo electric actuator. This servo electric actuator offers stable operation and high adjustment precision.

[0015] Further optimization of the design includes multiple speed changers, with each hydraulic motor, speed changer, and rotor connected sequentially. The hydraulic motor's speed can be significantly increased by the speed changers.

[0016] A further optimized design incorporates radiators connected to the high-pressure oil pipe and / or low-pressure oil pipe respectively. This integrated oil pipe radiator eliminates the need for a separate cooling system, achieving a lightweight design.

[0017] In a further optimized design, the hydraulic variable pump is an axial piston pump with an internal swashplate connected to the displacement control device.

[0018] When the displacement control device is a servo electric actuator, the extension and retraction of the servo electric actuator adjusts the inclination of the swashplate, thereby adjusting the displacement of the hydraulic variable pump.

[0019] A hydraulic variable displacement pump is an axial piston pump. Its internal swashplate is connected to a servo-electric actuator via a pushrod. The extension position of the servo-electric actuator determines the swashplate's angle, which in turn determines the pump's displacement. The angle is adjustable, thus making the pump's displacement adjustable.

[0020] Further optimization involves the airborne control unit independently controlling each servo electric actuator via a control bus. This independent control of each servo electric actuator by the airborne control unit results in independent control of the displacement of each hydraulic variable pump, and consequently, independent control of the thrust of each rotor without interference.

[0021] To further optimize the solution, the control bus adopts either the CANopen protocol bus or the ModBus protocol bus. The CANopen protocol is an open protocol for controller area networks, also known as CAN open protocol, which is suitable for high real-time scenarios such as aircraft control; the ModBus protocol is a serial communication protocol with a simple protocol structure and low development cost, and can be used as a low-cost alternative, suitable for scenarios with less demanding real-time requirements, such as low-speed aircraft or ground testing.

[0022] To further optimize the design, a cooling fan is installed on the surface of the radiator, or the cooling effect is enhanced by exhaust from the rotor.

[0023] A further optimized design involves connecting at least two hydraulic variable pumps in series to form a series pump, with the gearbox driving the hydraulic variable pump at the head of the gearbox. Connecting multiple hydraulic variable pumps in series, compared to multiple independent pumps, allows for the sharing of housings, bases, and some oil circuits, resulting in a more compact structure, reduced weight, and lower costs. Simultaneously, it simplifies the structure of the gearbox, reducing its weight, cost, and overall size.

[0024] Further optimization of the design includes multiple internal combustion engines, each driving the tandem pump via an independent gearbox. Increasing the number of internal combustion engines correspondingly increases the drive power to the rotor, thereby enhancing the payload capacity of the low-altitude aircraft.

[0025] In a further optimized design, each of the hydraulic variable pumps is driven by a separate fuel engine connected to an independent gearbox. This maximizes the drive power to the rotor, thereby further enhancing the payload capacity of the low-altitude aircraft.

[0026] In a further optimized design, the number of rotors is 4, 6, or 8 or more, with each rotor corresponding to an independent closed-loop hydraulic transmission circuit.

[0027] This utility model has the following technical advantages compared with the prior art:

[0028] 1. Breakthrough in technical bottlenecks: For the first time, stepless independent speed regulation of fuel power among multiple rotors was achieved, resolving the contradiction between range and control in electric vertical takeoff and landing aircraft;

[0029] 2. Lightweight design: The radiator is integrated into the oil pipe of the working circuit, eliminating the need for a separate cooling circuit, which helps to reduce weight and lower costs;

[0030] 3. High controllability: The closed-loop hydraulic circuit has a stepless speed regulation accuracy of ±1r / min, which far exceeds that of mechanical transmission;

[0031] 4. High scalability: The modular design supports multi-rotor configurations to adapt to different load requirements. Attached Figure Description

[0032] Figure 1 This is a structural block diagram of the first embodiment of the power system for the multi-rotor low-altitude aircraft of this utility model;

[0033] Figure 2 This is a structural block diagram of the second embodiment of the power system for the multi-rotor low-altitude aircraft of this utility model;

[0034] Figure 3 This is a structural block diagram of the third embodiment of the power system for the multi-rotor low-altitude aircraft of this utility model;

[0035] Figure 4 This is a structural block diagram of the fourth embodiment of the power system for the multi-rotor low-altitude aircraft of this utility model.

[0036] In the diagram: fuel engines 1 and 1 ’ 1 ’’ 1 ’’’ Engine output shafts 2 and 2 ’ 2 ’’ 2 ’’’ ; Gearbox 3, 3 ’ 3 ’’ 3 ’’’ Control bus 4, gearbox output shaft 5, 5 ’ 5 ’’ 5 ’’’ Hydraulic variable pump 6, 6 ’ 6 ’’ 6 ’’’ Low-pressure oil pipes 7, 7 ’ 7 ’’ 7 ’’’ High-pressure oil pipes 8 and 8 ’ 8 ’’ 8 ’’’ Hydraulic motors 9 and 9 ’ 9 ’’ 9 ’’’ Displacement control devices 10, 10 ’ 10 ’’ 10 ’’’ Radiator 11, 11 ’ 11 ’’ 11 ’’’ Motor output shafts 12, 12 ’ 12 ’’12 ’’’ ; Gearbox 13, 13 ’ 13 ’’ 13 ’’’ ; Gearbox output shafts 14, 14 ’ 14 ’’ 14 ’’’ Rotor 15, 15 ’ 15 ’’ 15 ’’’ ; Airborne control unit 16, heading and attitude sensor 17, spatial position sensor 18. Detailed Implementation

[0037] The present invention will now be described in further detail with reference to the embodiments shown in the accompanying drawings.

[0038] like Figures 1 to 4 As shown, four specific embodiments of the multi-rotor low-altitude aircraft propulsion system of this utility model are illustrated, with a quadcopter low-altitude aircraft propulsion system as an example for detailed explanation. The same principle applies to six-rotor, eight-rotor, and more rotor low-altitude aircraft propulsion systems implemented using the solution of this utility model.

[0039] like Figure 1 As shown, the power system of the multi-rotor low-altitude aircraft in the first embodiment includes a fuel engine 1 connected to a gearbox 3 via an engine output shaft 2. The gearbox 3 has four gearbox output shafts 5, 5... ’ 5 ’’ 5 ’’’ Each of the four circuits is connected to a closed hydraulic transmission circuit.

[0040] The gearbox 3 contains a gear set, whose function is to convert the speed input from the fuel engine 1 into an appropriate output speed, for example, reducing the speed input from the engine output shaft 2 from 5800 r / min to 2500 r / min, and then transmitting it through the four gearbox output shafts 5, 5... ’ 5 ’’ 5 ’’’ Output.

[0041] The first closed-loop hydraulic transmission circuit includes a hydraulic variable pump 6, a hydraulic motor 9, and a displacement control device 10. The gearbox 3 is connected to the hydraulic variable pump 6. The hydraulic variable pump 6 is connected to the hydraulic motor 9 through a high-pressure oil pipe 8, and then returned to the hydraulic variable pump 6 through a low-pressure oil pipe 7. The displacement control device 10 is connected to the hydraulic variable pump 6 to adjust its displacement.

[0042] The displacement control device 10 can be a swashplate cylinder controlled by a proportional solenoid valve or a servo electric actuator. Preferably, the displacement control device 10 adopts a servo electric actuator. Compared with the swashplate cylinder, the servo electric actuator has advantages such as higher control accuracy and higher reliability.

[0043] For example, in the first closed-loop hydraulic transmission circuit, the gearbox output shaft 5 is connected to the hydraulic variable pump 6, the outlet of the hydraulic variable pump 6 is connected to the high-pressure oil pipe 8, the other end of the high-pressure oil pipe 8 is connected to the inlet of the hydraulic motor 9, the outlet of the hydraulic motor 9 is connected to the low-pressure oil pipe 7, and the other end of the low-pressure oil pipe 7 is connected back to the inlet of the hydraulic variable pump 6, forming a closed-loop hydraulic transmission circuit from the hydraulic variable pump 6 to the hydraulic motor 9.

[0044] Furthermore, the low-pressure oil pipe 7 can be connected to an oil replenishment device, and a flushing valve can be connected between the high-pressure oil pipe 8 and the low-pressure oil pipe 7 to replace part of the hydraulic oil in the working circuit to the cooling and filtration circuit. The oil replenishment device and the flushing valve are well known to those skilled in the art and will not be described in detail here.

[0045] The output shaft 12 of the hydraulic motor 9 is connected to the gearbox 13. The gearbox 13 contains a gear set, which converts the input speed into another appropriate speed output from the gearbox output shaft 14. For example, it increases the speed of the motor output shaft 12 from 4000 r / min to 8000 r / min and outputs it from the gearbox output shaft 14. The gearbox output shaft 14 is connected to the hub of the rotor 15, driving the blades on the hub to rotate at the same speed, generating thrust.

[0046] In some cases, such as when the output shaft of the hydraulic motor 9 rotates at a sufficiently high speed to reach the speed required by the rotor 15, the gearbox 13 can be omitted, and the hydraulic motor 9 and the rotor 15 can be directly connected instead.

[0047] The connection structures of the other three closed hydraulic transmission circuits with the gearbox and rotor are the same as above.

[0048] The power system of this multi-rotor low-altitude aircraft uses a fuel engine as its power source. Increasing the fuel tank capacity and carrying more fuel will increase the range, significantly improving the endurance of the low-altitude aircraft.

[0049] The internal combustion engine drives a hydraulic variable pump via a gearbox. The hydraulic variable pump drives a hydraulic motor through a closed hydraulic circuit. The hydraulic motor directly drives or drives the rotor to rotate via a gearbox, thus distributing the output power of the internal combustion engine to each rotor. The displacement of the hydraulic variable pump is controlled by a displacement control device, which precisely, independently, and steplessly controls the rotational speed and torque of each rotor, thereby accurately controlling the thrust generated by the rotor and ensuring the stable flight of the low-altitude aircraft. This effectively solves the problem of independent stepless speed and torque regulation of multiple rotors.

[0050] The hydraulic variable pump 6 is an axial piston pump with an internal swashplate connected to the displacement control device 10. When the displacement control device 10 is a servo electric actuator, the extension and retraction of the actuator adjusts the swashplate's inclination, thereby adjusting the displacement of the hydraulic variable pump 6.

[0051] The hydraulic variable pump 6 is an axial piston pump. Its internal swashplate is connected to the push rod of the displacement control device 10 via a push rod. When the displacement control device 10 is a servo-electric push rod, the extension position of the push rod determines the swashplate's inclination, which inclination determines the displacement of the hydraulic variable pump 6. The inclination is adjustable, thus the displacement of the hydraulic variable pump 6 is adjustable. For example, the displacement of the hydraulic variable pump 6 can be adjusted between 0 ml / r and 45 ml / r. With the displacement of the hydraulic motor 9 fixed, for example, 23 ml / r, the speed and displacement of the hydraulic variable pump 6 determine the speed of the hydraulic motor 9.

[0052] like Figure 1 As shown, the power system of this multi-rotor low-altitude aircraft also includes an onboard control unit 16, which independently controls each displacement control device 10 via a control bus 4. The control of each displacement control device 10 by the onboard control unit 16 is independent and does not interfere with each other, and thus the displacement control of each hydraulic variable pump 6 is also independent and does not interfere with each other, thereby achieving independent and non-interfering control of the thrust of each rotor 15.

[0053] like Figure 1 As shown, the power system of the multi-rotor low-altitude aircraft also includes a heading and attitude sensor 17 and a spatial position sensor 18. The airborne control unit 16 connects to the heading and attitude sensor 17 and the spatial position sensor 18 and acquires their relevant data.

[0054] The airborne control unit 16 receives flight commands, which can come from direct commands from the onboard pilot or remote commands from the ground command and control center or ground pilot. It also acquires relevant data from the heading and attitude sensor 17 and the spatial position sensor 18, generates a control strategy, and controls the displacement control devices 10 and 10' via the control bus. ’ 10 ’’ 10 ’’’ Send corresponding data; Displacement control devices 10, 10 ’ 10 ’’ 10 ’’’ To generate the corresponding action, adjust hydraulic variable pumps 6 and 6. ’’ 6 ’’’ 6 ’’’ The swashplate angle causes a change in its displacement, affecting hydraulic motors 9 and 9. ’ 9 ’’ 9 ’’’ The rotational speed and torque change accordingly, thereby adjusting rotors 15 and 15. ’ 15 ’’ 15 ’’’ The rotational speed generates corresponding thrust, thereby controlling flight speed, attitude, and heading.

[0055] At the same time, the airborne control unit 16 is also electrically connected to the electronic control unit (ECU) of the fuel engine 1 to control the start, stop, and throttle of the fuel engine 1, thereby achieving communication with the rotors 15 and 15... ’ 15 ’’ 15 ’’’ The airborne control unit 16 also acquires the operating condition data of the fuel engine 1 and transmits it to the flight control system or the ground command and control center.

[0056] Control bus 4 uses either the CANopen protocol bus or the ModBus protocol bus. The CANopen protocol is an open protocol for controller area networks, also known as CAN open protocol, which is suitable for high real-time scenarios such as aircraft control; the ModBus protocol is a serial communication protocol with a simple protocol structure and low development cost, and can be used as a low-cost alternative, suitable for scenarios with less demanding real-time requirements, such as low-speed aircraft or ground testing.

[0057] like Figure 1 As shown, radiators 11 are connected to the high-pressure oil pipe 8 and / or the low-pressure oil pipe 7 respectively. The high-pressure oil pipe 8 and the low-pressure oil pipe 7 are made of metal and are tightly connected to the radiator 11, which is also made of metal, in a certain connection method. Preferably, the connection method is welding, including direct welding or welding through a metal intermediate with good thermal conductivity.

[0058] The heat from the hydraulic oil in the high-pressure and low-pressure oil pipes can be conducted to the radiator, and then transferred to the air through the radiator's fins. The integrated oil pipe radiator eliminates the need for a separate cooling system, enabling a lightweight design. A cooling fan can be installed on the radiator surface, or, through appropriate spatial layout design, a portion of the rotor exhaust can pass through the radiator surface, thereby enhancing the heat dissipation effect and increasing the cooling speed.

[0059] like Figure 2 As shown, the second embodiment of the multi-rotor low-altitude aircraft propulsion system is an improvement upon the first embodiment. The difference lies in the fact that in the second embodiment, hydraulic pump 6 and hydraulic pump 6... ’ The input shafts are connected in series to form the first series pump; hydraulic pump 6 ’’ and hydraulic pump 6 ’’’ The input shafts are connected in series to form a second series pump. The output shafts of gearbox 3 are reduced from four to two, namely gearbox output shafts 5 and 5'. ’’ The gearbox output shaft 5 is connected to the first series pump. ’’ Connect the second series pump, while keeping the connections of the other parts unchanged.

[0060] The beneficial technical effects of this embodiment are that it simplifies the structure of the reduction gearbox, reduces weight, lowers cost, and reduces overall size. Furthermore, compared to multiple independent pumps, a single tandem pump can share the same housing, base, and some oil passages, resulting in a more compact structure, reduced weight, and lower cost.

[0061] like Figure 3 As shown, the third embodiment of the multi-rotor low-altitude aircraft propulsion system is an improvement upon the second embodiment. The difference lies in the fact that the third embodiment employs two fuel engines, namely fuel engine 1 and fuel engine 2. ’ In this configuration, the engine output shaft 2 of the internal combustion engine 1 is connected to the transmission 3, which only performs gear shifting and has no transfer function. The transmission output shaft 5 of the transmission 3 is connected to the first tandem pump. Similarly, the engine output shaft 2 of the internal combustion engine 1'... ’ Connecting gearbox 3 ’ , gearbox 3 ’ It only has a transmission function and no transfer case function. (Transmission 3) ’ 5th gearbox output shaft ’’ Connect the second series pump. The airborne control unit 16 is simultaneously electrically connected to fuel engine 1 and fuel engine 2. ’ The connection relationships of other parts remain unchanged.

[0062] The beneficial technical effect of this embodiment is that by using two engines to output power, compared with the scheme of one fuel engine, the driving power of the rotor is increased, thereby improving the carrying capacity of the low-altitude aircraft.

[0063] like Figure 4 As shown, the fourth embodiment of the multi-rotor low-altitude aircraft propulsion system is an improvement upon the first embodiment. The difference lies in the fact that the fourth embodiment employs four fuel engines, namely fuel engine 1, fuel engine 2, and fuel engine 3. ’ 1. Fuel engine ’’ 1. Fuel engine ’’’ And four independent hydraulic variable pumps, namely hydraulic variable pump 6, hydraulic variable pump 6 ’ 6 hydraulic variable pumps ’’ 6 hydraulic variable pumps ’’’ The fuel engine 1 is connected to the transmission 3 and the hydraulic variable pump 6; the fuel engine 1 ’ With gearbox 3 ’ 6 hydraulic variable pumps ’ Connection; fuel engine 1 ’’ With gearbox 3 ’’ 6 hydraulic variable pumps ’’ Connection; fuel engine 1 ’’’ With gearbox 3 ’’’ 6 hydraulic variable pumps’’’ Connection. The airborne control unit 16 is simultaneously electrically connected to fuel engine 1 and fuel engine 1. ’ 1. Fuel engine ’’ and fuel engine 1 ’’’ Other connection relationships remain unchanged.

[0064] The beneficial technical effect of this embodiment is that by using four fuel engines to output power, compared with the scheme of one or two fuel engines, the driving power of the rotor is further increased, thereby further improving the carrying capacity of the low-altitude aircraft.

[0065] Specifically, in the above four embodiments, fuel engines 1, 1 ’ 1 ’’ 1 ’’’ The selected engine is a G150 aviation gasoline piston engine manufactured by Hongpeng Aviation Power, with hydraulic variable pumps 6 and 6. ’ 6 ’’ 6 ’’’ The system utilizes the HX-HA22VG hydraulic motor, primarily developed and manufactured by AIDC (Zhuhai Hengqin) Co., Ltd., with components including hydraulic motors 9 and 9. ’ 9 ’’ 9 ’’’ The A2FM23 displacement control device 10 and 10, manufactured by Guangzhou Huaxin Hydraulic Technology Co., Ltd., are used. ’ 10 ’’ 10 ’’’ The servo-driven reciprocating electric actuator (cylinder) QDA60-R5-150KG-50mm / S-750W, manufactured by Dongguan Guanghong Automation Equipment Co., Ltd., is used, with radiators 11 and 11. ’ 11 ’’ 11 ’’’ The radiator used is a shovel-shaped radiator (1060 material) manufactured by Dongguan Jindu Hardware Products Co., Ltd., measuring 737mm*120mm*110mm in height. The airborne control unit 16 uses a programmable industrial intelligent gateway SIG-0601-C01 manufactured by Shenzhen Shengbo Technology Embedded Computer Co., Ltd. The rotors are 15 and 15... ’ 15 ’’ 15 ’’’ The low-altitude flight propulsion unit, HX-carbon fiber & EPP-D1500P16-550KG-A, is developed and manufactured by AIDC (Zhuhai Hengqin) Co., Ltd. Gearbox 3, 3 ’ 3 ’’ 3 ’’’ 13, 13 speed changer ’ 13 ’’ 13 ’’’The heading and attitude sensor 17 and the spatial position sensor 18 are common products in the prior art and are well known to those skilled in the art, so they will not be described in detail.

[0066] In summary, as described in the specification and figures, this utility model has been manufactured into actual samples and subjected to multiple use tests. The test results demonstrate that this utility model achieves its intended purpose, and its practicality is beyond doubt. The embodiments described above are merely for illustrative purposes and are not intended to limit the scope of this utility model. Any equivalent embodiments made by those with common knowledge in the relevant technical field, utilizing the technical content disclosed in this utility model, without departing from the scope of the technical features and similar features disclosed in this utility model, are all within the protection scope of this utility model.

Claims

1. A propulsion system for a multi-rotor low-altitude aircraft, characterized in that: It includes at least one fuel engine (1) connected to a gearbox (3), the gearbox (3) being connected to at least one closed hydraulic transmission circuit; Each of the closed hydraulic transmission circuits includes a hydraulic variable pump (6), a hydraulic motor (9), and a displacement control device (10). The gearbox (3) is connected to the hydraulic variable pump (6). The hydraulic variable pump (6) is connected to the hydraulic motor (9) via a high-pressure oil pipe (8) and then returned to the hydraulic variable pump (6) via a low-pressure oil pipe (7). The displacement control device (10) is connected to the hydraulic variable pump (6) to adjust its displacement. It also includes multiple rotors (15), each of which is connected in sequence to the hydraulic motor (9) and rotor (15); It also includes an airborne control unit (16) and a heading and attitude sensor (17), wherein the airborne control unit (16) acquires data from the heading and attitude sensor (17) to independently control each of the displacement control devices (10).

2. The multi-rotor low-altitude aircraft propulsion system according to claim 1, characterized in that, The displacement control device (10) is a servo electric actuator.

3. The multi-rotor low-altitude aircraft propulsion system according to claim 1, characterized in that, It also includes multiple speed changers (13), each of the hydraulic motors (9), speed changers (13) and rotors (15) being connected in sequence.

4. The multi-rotor low-altitude aircraft propulsion system according to claim 1, characterized in that, A radiator (11) is connected to the high-pressure oil pipe (8) and / or the low-pressure oil pipe (7).

5. The multi-rotor low-altitude aircraft propulsion system according to claim 1, characterized in that, The hydraulic variable pump (6) is an axial piston pump with a swashplate inside, which is connected to the displacement control device (10).

6. The multi-rotor low-altitude aircraft propulsion system according to claim 1, characterized in that, The airborne control unit (16) independently controls each of the displacement control devices (10) via the control bus (4).

7. The multi-rotor low-altitude aircraft propulsion system according to claim 6, characterized in that, The control bus (4) adopts the CANopen protocol bus or the ModBus protocol bus.

8. The multi-rotor low-altitude aircraft propulsion system according to claim 4, characterized in that, The surface of the radiator (11) is provided with a cooling fan or the cooling effect is enhanced by the exhaust of the rotor (15).

9. The multi-rotor low-altitude aircraft propulsion system according to claim 1, characterized in that, At least two of the hydraulic variable pumps (6) are connected in series to form a series pump, with the hydraulic variable pump (6) being driven by a single head of the gearbox (3).

10. The multi-rotor low-altitude aircraft propulsion system according to claim 9, characterized in that, It includes multiple fuel engines (1), each of which drives the series pump via an independent gearbox (3).

11. The multi-rotor low-altitude aircraft propulsion system according to claim 1, characterized in that, Each of the hydraulic variable pumps (6) is driven by a separate fuel engine (1) connected to an independent gearbox (3).

12. The multi-rotor low-altitude aircraft propulsion system according to claim 1, characterized in that, The number of rotors (15) is 4, 6 or 8 or more, and each rotor (15) corresponds to an independent closed hydraulic transmission circuit.

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