Tilting ducted fan type hovercar

Abstract

The invention discloses a tiltable ducted fan type hovercar, and belongs to the technical field of hovercars. The flying car adopts a cross-shaped pneumatic layout, and four independent power units are integrated on the car roof. Each unit comprises a ducted fan and a ducted fan tilting mechanism, so that the ducted fan has the capacity of independently tilting around a support arm shaft by + / -180 degrees. And the control system calculates the target thrust and the torque vector, and distributes the target rotating speed and the tilting angle of each ducted fan in real time by utilizing a control efficiency matrix, so that the flexible regulation and control of the thrust vector are realized. The ducted fan tilting mechanism has the advantages that the ducted fan tilting mechanism has the speed reducing and torque increasing functions and the self-locking function, wind field disturbance is effectively resisted, and flight safety is ensured; (2) six-degree-of-freedom full-decoupling control is achieved through an overdrive control algorithm, the position and attitude independent control capacity is achieved, and the flight stability and the riding comfort are remarkably improved. The invention provides an efficient and reliable solution for urban air traffic.

Description

Technical Field

[0001] This invention relates to a general-purpose transportation device, belonging to the field of flying car technology, specifically a tiltable ducted fan flying car. Background Technology

[0002] With the continuous development of technology, traditional means of transportation can no longer meet people's demands for travel efficiency and convenience. Therefore, expanding transportation modes into three-dimensional space has become a new development trend. Flying cars, as a new type of transportation, combine the flight capabilities of aircraft with the driving capabilities of ground vehicles, effectively alleviating ground traffic congestion and significantly improving travel efficiency.

[0003] However, existing flying cars still have many shortcomings in terms of design and performance. Traditional fixed-wing flying cars typically use retractable wings. Taking the Transition designed by Terrafugia in 2009 as an example, it requires folding or unfolding its wings to switch between flight and ground modes. This not only results in a complex structure but also requires ample takeoff and landing space, leading to long takeoff and landing times and low operating efficiency. While multi-rotor flying cars possess vertical takeoff and landing capabilities, most are underactuated systems. The "Voyager X2" electric vertical takeoff and landing flying car developed by XPeng Aerospace uses a multi-rotor layout and demonstrates good adaptability in short-distance urban transportation. However, its control input dimension is less than the degrees of freedom of motion, and the direction of the thrust generated is fixed in the body coordinate system. The driving force and torque are highly coupled, making it difficult to achieve six degrees of freedom omnidirectional control. This control limitation makes it difficult to meet the high-precision application scenarios that require independent adjustment of position and attitude. To address the underactuation problem of flying cars, researchers have conducted extensive studies on thrust-vectoring flying cars. The LiliumJet, designed by the German company Lilium, integrates multiple propellers within the wing, achieving thrust vectoring control through wing tilting. This increases the degrees of freedom for attitude control, effectively suppressing attitude angle fluctuations during flight and improving flight stability. However, the large wing structure and heavy weight of this aircraft, coupled with stringent requirements for takeoff and landing sites, limit its application and widespread adoption in low-altitude airspace. Summary of the Invention

[0004] This invention addresses the problems existing in the prior art by disclosing a tiltable ducted fan-type flying car. It solves the technical problems of fixed-wing flying cars, such as complex structure, inability to take off and land vertically, and long takeoff and landing times, as well as the difficulty in achieving six-degree-of-freedom omnidirectional control due to the high coupling of driving force and torque in multi-propeller flying cars. The tiltable ducted fan-type flying car disclosed in this invention combines vertical takeoff and landing, high-speed cruising, and ground driving functions. With its compact structure and flexible thrust direction control, it can effectively meet the technical challenges of diverse travel scenarios.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a tiltable ducted fan flying car, comprising a body, a flight propulsion assembly, a ground propulsion assembly, a sensor assembly, a control assembly, and a battery pack; the flight propulsion assembly, the ground propulsion assembly, the sensor assembly, and the control assembly are mounted on the body; the battery pack is fixedly mounted in the middle of the chassis of the body to provide power to each assembly; the ground propulsion assembly is used to realize the ground driving function of the flying car;

[0006] The vehicle body includes a main body, a mounting platform, and four wheel suspension brackets. The main body adopts a load-bearing structure, forming a crew cabin and equipment installation space inside. The mounting platform is fixed to the top of the main body for connecting flight power components, and a wheel suspension bracket is set at each of the four corners of the bottom of the main body.

[0007] Compared with the prior art, the significant advantages of this invention are:

[0008] (1) The tiltable ducted-fan flying car disclosed in this invention adopts a cruciform aerodynamic layout. By using a ducted fan structure to replace the traditional wing, the flying car can maintain high lift while having a lighter weight and better structural compactness. This design improves the vertical take-off and landing capability while reducing the requirements for take-off and landing sites, effectively improving the maneuverability and stability of the flying car.

[0009] (2) The tiltable ducted flying car disclosed in this invention has each ducted fan that can tilt independently around the arm axis. Compared with the traditional multi-propeller flying car, by increasing the degree of freedom of the ducted fan to tilt around the arm axis, the underactuated system is transformed into an overactuated system, which can realize the active adjustment of thrust direction and the six-degree-of-freedom decoupled control of position and attitude. This not only improves the control accuracy and ride comfort during flight, but also effectively enhances the fault tolerance and flight safety of the system due to the control redundancy. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of a tilting ducted fan flying car according to the present invention.

[0011] Figure 2 This is a side view of a tiltable ducted fan flying car according to the present invention.

[0012] Figure 3 This is a schematic diagram of a tiltable ducted fan flying car of the present invention during cruise flight.

[0013] Figure 4 This is an overall schematic diagram of the ducted fan tilting mechanism of a tiltable ducted fan flying car according to the present invention.

[0014] Figure 5This is a side view of the ducted fan tilting mechanism of a tiltable ducted fan flying car according to the present invention.

[0015] Figure 6 This is a schematic diagram of the vehicle attitude angle of a tiltable ducted fan flying car in a trajectory tracking task according to the present invention.

[0016] Figure 7 The image shows a three-axis position tracking diagram of a tiltable ducted fan flying car in a trajectory tracking task according to the present invention, wherein (a) is the x-axis position tracking diagram, (b) is the y-axis position tracking diagram, and (c) is the z-axis position tracking diagram.

[0017] The reference numerals in the figure are respectively:

[0018] 1-First side ducted fan; 11-Propeller; 12-Propeller drive motor; 13-Motor mounting bracket; 14-Duct housing.

[0019] 2-Second duct fan; 3-Third duct fan; 4-Fourth duct fan; 5-Cross-shaped arm; 6-Mounting platform; 7-Window; 8-Wheel; 9-Body.

[0020] 10-Ducted fan tilting mechanism; 101-Worn gear; 102-Worn; 103-Tilting motor; 104-First coupling; 105-Angular contact ball bearing; 106-Bearing housing; 107-Second coupling; 108-Tilting rod; 109~1010-A pair of deep groove ball bearings. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0022] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0023] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly and specifically defined.

[0024] In this invention, unless otherwise explicitly specified and limited, the terms "connection," "fixing," etc., should be interpreted broadly. For example, "fixing" can mean a fixed connection, a detachable connection, or an integral part; "connection" can mean a mechanical connection or an electrical connection. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0025] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are feasible to those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0026] The following section will further introduce the specific implementation method, as well as the technical difficulties and inventive points of this invention, using this design example as an example.

[0027] Combination Figures 1 to 5 The tiltable ducted fan flying car of the present invention includes a body 9, a flight propulsion assembly, a ground propulsion assembly, a sensor assembly, a control assembly, and a battery pack. The flight propulsion assembly, ground propulsion assembly, sensor assembly, and control assembly are mounted on the body 9. The battery pack is fixedly mounted in the center of the chassis of the body 9, providing power to all components.

[0028] The vehicle body 9 includes the main body, mounting platform 6, and four wheel suspension brackets. The main body adopts a load-bearing structure, forming a crew cabin and equipment installation space inside. The mounting platform 6 is fixed to the top of the main body for connecting the flight propulsion components. A wheel suspension bracket is installed at each of the four corners of the bottom of the main body. The vehicle body 9 is equipped with windows 7.

[0029] The ground propulsion assembly, used to enable the flying car's ground driving function, includes four wheels 8 and four hub motors. The four wheels 8 are rotatably connected to wheel suspension brackets at the four corners of the vehicle body 9 via hub bearings. The hub motors are interference-fitted with the wheel hubs of the wheels 8 and are used to independently drive the rotation of each wheel to achieve the vehicle's forward, reverse, steering, and braking functions.

[0030] The flight propulsion assembly includes a cross-shaped arm 5, four propeller drive motors 12, four sets of ducted fan tilting mechanisms 10, motor mounting bases 13, and four identical ducted fans. These four ducted fans are named First Ducted Fan 1, Second Ducted Fan 2, Third Ducted Fan 3, and Fourth Ducted Fan 4, with First Ducted Fan 1 located at the front of the vehicle and named counter-clockwise. The cross-shaped arm 5 is fixed to the center of the top surface of the mounting platform 6 via a central mounting base. The four ducted fans 1-4 are respectively located at the four ends of the cross-shaped arm 5. Each ducted fan includes a propeller 11 and a duct housing 14 protecting the propeller 11. One propeller 11 is fixed to the output shaft of a propeller drive motor 12 via a key connection. The propeller drive motor 12 is connected to the ducted fan tilting mechanism 10 via the motor mounting base 13. The cross-shaped arm 5 is fixed to the top of the mounting platform 6.

[0031] The cross-shaped arm 5 includes a central mounting cavity and four hollow support arms.

[0032] Combination Figures 4 to 5 The ducted fan tilting mechanism 10 is an actuator that drives four ducted fans to tilt. Each ducted fan tilting mechanism is identical, and its core is a worm gear reducer. The ducted fan tilting mechanism 10 includes a tilting motor 103 as a power source, a reducer mechanism with a self-locking function, and a tilting rod 108 for transmitting power.

[0033] As an example of a reducer mechanism, it includes a worm gear 101, a worm 102, an angular contact ball bearing 105, a bearing housing 106, a first coupling 104, a tilting motor 103, a second coupling 107, and a pair of deep groove ball bearings 109-1010. The worm gear 101, worm 102, angular contact ball bearing 105, bearing housing 106, first coupling 104, tilting motor 103, and second coupling 107 are located within the central mounting cavity, while the tilting rod 108 and the pair of deep groove ball bearings 109-1010 are located within the support arm mounting cavity.

[0034] One end of the worm gear 102 is rotatably connected to the bearing housing 106 via an angular contact ball bearing 105, and the other end of the worm gear 102 is fixedly connected to the output shaft of the tilting motor 103 via a first coupling 104.

[0035] The worm gear 101 meshes with the worm 102. One end of the tilting rod 108 is connected to the worm gear 101 via the second coupling 107. The other end of the tilting rod 108 is arranged along the support arm of the cross-shaped machine arm 5 and extends out of the support arm to be fixedly connected to the motor mounting base 13. The tilting rod 108 rotates within the support arm mounting cavity via a pair of deep groove ball bearings 109 to 1010.

[0036] When the tilt motor 103 is working, it drives the worm wheel 101 to rotate through the worm gear 102, which in turn drives the tilt rod 108 and the entire ducted fan (including the motor mounting base 13, the propeller drive motor 12, the propeller 11 and the duct housing 14) fixed thereon to tilt around the axis of the support arm, thereby achieving independent and precise adjustment of the thrust direction.

[0037] Furthermore, when the four ducted fans 1-4 generate lift during operation and exert pressure on the four tilting rods 108, this pressure is transmitted to the arm 5 through the first bearing 109 and the second bearing 1010 of the tilting rods. This design helps to improve the strength and stability of the tilting rods 108, ensuring the safety and reliability of the four ducted fans 1-4 during tilting.

[0038] The sensor assembly is used to collect vehicle attitude, position, and speed information in real time.

[0039] The control component is fixed to the equipment compartment behind the passenger compartment with screws. The control component is electrically connected to various sensors, tilt motor 103, propeller drive motor 12 and hub motor via wiring harness (the wiring harness passes through pre-reserved holes in the vehicle body with clearance fit). By collecting vehicle attitude, position and speed information in real time, and integrating the pilot's commands and sensor information, the control component coordinates the control of the ground power component and the flight power component, specifically divided into two basic modes: ground driving and air flight.

[0040] In ground driving mode, the control unit primarily drives the ground propulsion components. The control unit controls the differential operation of the four hub motors 102 to achieve the vehicle's forward, reverse, steering, and braking functions. Simultaneously, the control unit manages the attitude of the flight propulsion components to optimize wind resistance: it adjusts the duct planes of the first ducted fan 1 at the front of the vehicle and the second ducted fan 2 at the rear to be essentially parallel to the ground (tilt angle approximately 0°) to minimize air resistance; it controls the duct planes of the third ducted fan 3 and the fourth ducted fan 4 to tilt within the range of -90° to +90° to generate auxiliary thrust or reverse drag along the vehicle's forward direction 9, working in conjunction with the hub motors to achieve efficient ground driving.

[0041] In the in-flight mode, the control components primarily drive the flight propulsion components. This mode is further divided into three sub-modes: vertical takeoff and landing, transitional flight, and cruise forward flight.

[0042] In vertical takeoff and landing (VTOL) mode, the control unit adjusts the duct planes of the four ducted fans (1-4) to be parallel to the ground. The control unit independently adjusts the propeller speed of each ducted fan to generate a resultant force of equal magnitude and vertical upward, thereby enabling the flying car to take off and land vertically.

[0043] In transitional flight mode, the control unit gradually increases the duct plane tilt angle of the left-side ducted fan 2 and the right-side ducted fan 4 from 0°, decomposing the thrust generated into a vertical component to provide lift and a horizontal component to provide forward thrust. Simultaneously, the duct planes of the front-side ducted fan 1 and the rear-side ducted fan 3 remain parallel to the ground for most of the time, primarily providing lift. When the sensor unit detects that external disturbances such as wind disturbances cause the vehicle's attitude angle to deviate from the target value, the control unit immediately calculates the required compensation torque and instructs the front-side ducted fan 1 and the rear-side ducted fan 3 to tilt symmetrically or anti-symmetrically around the axis of the arm 5. By generating a compensation torque opposite to the direction of the disturbance torque, the attitude angle of the vehicle 9 is quickly corrected, maintaining flight stability and achieving near-zero attitude angle flight, significantly improving passenger comfort and safety.

[0044] Combination Figure 3 In cruise forward flight mode, the flying car enters a highly efficient forward flight state. The control unit allocates control inputs based on the driver's commands and flight path planning, using a pseudo-inverse method. The ducted planes of the left-side ducted fan 2 and the right-side ducted fan 4 maintain a fixed forward tilt angle (e.g., 30°) to generate continuous cruise forward thrust. The ducted planes of the front-side ducted fan 1 and the rear-side ducted fan 3 remain parallel to the ground for most of the time, and their thrust primarily provides lift, while also including a small portion of forward thrust. When disturbance torques caused by wind or other external factors during flight cause fluctuations in the attitude angle of the vehicle body 9, the control unit adjusts the tilt angles of the ducted fans 1-4 in real time, using the resulting attitude correction torques to counteract the disturbances, thereby improving stability and ride comfort during cruise flight.

[0045] The determination of the above-mentioned structural parameters in this invention is based on a series of interrelated calculations to ensure the scientific nature and optimization of the design. The numerical relationships and design basis behind each key parameter will be explained in the following sections.

[0046] 1. Relationship between vehicle weight and thrust requirement:

[0047] The total vehicle weight is the fundamental basis for power system design. This invention accurately determines the total takeoff weight through iterative calculations. This weight is a combination of the following component weights:

[0048] The total takeoff weight of a flying car mainly includes structural weight. Weight of electric power system Power battery weight Fixed equipment weight and payload weight Total takeoff weight The calculation formula is:

[0049] ,

[0050] In the formula, For structural weight, For the weight of the electric power system, For the weight of the power battery, To fix the weight of the equipment, For the effective payload weight, This refers to the number of passengers. To control the weight of the system, This refers to the weight of the avionics instrumentation system.

[0051] Because this invention employs an aerodynamic layout with four ducted fans, and takes into account additional loads such as wind resistance encountered during actual flight, the thrust of the ducted fans is... for:

[0052] ,

[0053] This thrust value is the core input and constraint for the subsequent aerodynamic design of the ducted fan.

[0054] 2. Aerodynamic design of ducted fans based on momentum theory and similarity theory:

[0055] To achieve the design thrust of the ducted fan The dimensions and blade parameters of the ducted fan need to be determined. This invention abandons empirical selection and adopts the simplified design method for ducted propellers proposed by Gao Yongwei, based on the momentum theorem of fluid dynamics.

[0056] Based on the incompressible continuity equation and momentum theory, the thrust of a ducted fan can be derived. :

[0057] ,

[0058] in, The density of the incoming gas. The outlet area of ​​the ducted fan. Let be the axial velocity of the incoming gas. The flow velocity at the outlet of the ducted fan. For the propeller disk area, The flow velocity at the propeller disk, This represents the airflow rate at the propeller disk.

[0059] ,

[0060] Specific speed is one of the most important similarity parameters in the similarity theory of ventilation fans. The blade diameter and hub ratio are both strongly correlated with specific speed. In the formula, It is the number of revolutions; The rotational speed of the blades; The total pressure generated by the propeller disk; The diameter of the propeller disk; For coefficients; To account for the static pressure difference generated by the propeller disk during loss, The static pressure difference generated by the propeller disk is not considered when losses are not taken into account; To ignore the static pressure difference generated by the propeller disk; airflow through the ducted fan will have intake losses and exhaust losses. The intake loss is related to the ratio r / D1 of the radius at the duct inlet and the diameter of the propeller disk. This is the intake loss coefficient. This is the exhaust loss coefficient; This is the sum of the loss coefficients.

[0061] The number of propeller blades can be determined based on empirical values ​​between the number of propeller blades Z and the hub ratio d, as shown in Table 1:

[0062] , exist Within a reasonable range, closest to - The optimal solution is represented by the relationship curve. The calculated parameters of the ducted fan are shown in Table 2.

[0063] , The ducted fan employs a cylindrical geometry, which not only facilitates smooth airflow and reduces air resistance but also provides high rigidity and strength. For material selection, aluminum alloy and carbon fiber composites were primarily considered. Aluminum alloys offer high strength and good machinability, and are relatively inexpensive; however, their relatively high density hinders the lightweight design of the ducted fan. Carbon fiber composites, on the other hand, have lower density and higher specific strength, significantly reducing weight while maintaining structural strength. Therefore, carbon fiber composites were ultimately chosen as the primary material for the ducted fan structure.

[0064] Volume of duct casing 14 It can be represented as:

[0065] ,

[0066] in, The outer diameter of the duct casing. The inner diameter of the duct casing is larger than the propeller disk diameter, and its size depends on the wall thickness of the duct casing. The overall shape of the duct casing is designed to be circular. This refers to the height of the duct shell. Based on the material density of carbon fiber composite materials... and the volume of the outer shell The weight of the duct shell It can be represented as:

[0067] ,

[0068] Since ducted fans consist of a propeller, duct housing, propeller drive motor, and considering the weight of the motor selection and other components (such as support structures, bolts, etc.), the weight of a ducted fan is... It can be represented as:

[0069] =1.5 ,

[0070] 3. Calculate the driving torque of the tilting mechanism and determine the transmission ratio:

[0071] To ensure the reliable and precise operation of the ducted fan tilting mechanism, its driving torque must be accurately calculated. This torque must overcome three loads: the load torque... Inertial torque during system startup or braking and frictional torque Total output torque for:

[0072] ,

[0073] ,

[0074] in, For the weight of the tilting rod (108), For the weight of the ducted fan, This is the distance from the center of gravity of the tilting rod to the tilting axis. This is the distance from the center of gravity of the ducted fan assembly to the tilt axis. The total moment of inertia of the system. For the desired angular acceleration, For gravitational acceleration, To account for the system's tilting efficiency due to frictional torque;

[0075] Based on the above calculations and the rated torque of the selected tilt motor According to the torque increase relationship of the reducer:

[0076] ,

[0077] To ensure With a margin, the gear ratio i of the reducer of the ducted fan tilting mechanism (10) is determined. The selection of this gear ratio i satisfies both the torque increase requirement and the system self-locking (to prevent wind disturbance from causing angle drift) functional requirements. Its structural layout is as follows: Figure 4 and Figure 5 As shown.

[0078] Example 1

[0079] The vehicle weighs 860kg. Through a lightweight cross-shaped duct layout and the application of composite materials, it achieves a weight reduction of approximately 20% compared to the traditional "wing + tiltrotor" layout. Its specific parameters and performance are as follows:

[0080] Ducted fan diameter: 1.5m, designed based on momentum theorem and blade element theory, single thrust can reach 2500N.

[0081] Vehicle dimensions: 3256mm × 1510mm × 1578mm, compact structure, reducing takeoff and landing space requirements by 30%.

[0082] Control Method: To transform the flying car from an underactuated system to an overactuated system and achieve complete decoupling control of position and attitude, this invention employs a control allocation strategy based on the pseudo-inverse method. The spatial motion equations of the flying car can be simplified as follows:

[0083] ,

[0084] in, and These are the desired control force and control torque vectors, respectively. The control efficiency matrix (a function of the tilt angle α) is used. This represents the thrust command vector for each ducted fan. To address control redundancy, a virtual control variable U=[UF,UM] is introduced. T (T denotes transpose), and the Moore-Penrose pseudoinverse A of the control efficiency matrix A is obtained by solving for A. + To allocate control quantities:

[0085] N = A + ⋅U,

[0086] The advantage of this method is that when A takes the pseudo-inverse, the norm of N can be minimized, thereby minimizing energy consumption and ensuring uniform load on each ducted fan. The effectiveness of this control algorithm has been verified in simulations, such as... Figure 6 and Figure 7 As shown, in complex trajectory tracking tasks, the position and attitude errors of the flying car are controlled within a very small range (position error <1m, attitude angle error <0.5°), which fully proves the correctness of the numerical relationship and design basis.

[0087] Flight mode performance: The maximum forward speed can reach 201 km / h, and the maximum ground driving speed is 146.5 km / h.

[0088] This embodiment fully verifies that the flying car described in this invention achieves the goals of lightweight and compact design while possessing high-precision attitude control capabilities and excellent flight performance, thus meeting the complex mission requirements of urban air mobility (UAM).

Claims

1. A tiltable ducted fan air vehicle, characterized by: The vehicle body (9), a flight power assembly, a ground power assembly, a sensor assembly, a control assembly and a battery pack; the flight power assembly, the ground power assembly, the sensor assembly and the control assembly are installed on the vehicle body (9); the battery pack is fixedly installed in the middle part of the chassis of the vehicle body (9) and provides electric energy for each assembly; the ground power assembly is used for realizing the ground driving function of the flying vehicle. The vehicle body (9) comprises a vehicle body main body, a mounting platform (6) and four wheel suspension supports, the vehicle body main body adopts a load-bearing structure, and an occupant cabin and an equipment installation space are formed in the vehicle body main body; the mounting platform (6) is fixed on the top surface of the vehicle body main body and is used for connecting the flight power assembly, and one wheel suspension support is arranged at each corner of the bottom of the vehicle body main body.

2. The tiltable ducted fan flying car of claim 1, wherein: The ground power assembly comprises four wheels (8) and m hub motors, and m is 2 or 4; the four wheels (8) are rotationally connected to the wheel suspension supports at the four corners of the bottom of the vehicle body (9) through hub bearings; each hub motor is in transmission connection with the hub of the corresponding wheel (8) and is used for independently driving the rotation of each wheel to realize the functions of forward driving, backward driving, steering and braking of the vehicle.

3. The tiltable ducted fan flying car of claim 2, wherein: The flight power assembly comprises a cross-shaped machine arm (5), four propeller driving motors (102), four sets of ducted fan tilting mechanisms (10), a motor mounting seat (13) and four structurally identical ducted fans, the four ducted fans are named as a first ducted fan (1), a second ducted fan (2), a third ducted fan (3) and a fourth ducted fan (4) in sequence from the front to the rear of the vehicle, and the first ducted fan (1) is located at the front of the vehicle; the cross-shaped machine arm (5) is fixedly connected to the top center of the mounting platform (6) through the mounting base at the center thereof; the four ducted fans are arranged at the four ends of the cross-shaped machine arm (5); the ducted fan comprises a propeller (11) and a duct housing (14) for protecting the propeller (11); one propeller (11) is fixedly connected to the output shaft of one propeller driving motor (102) through a key; the propeller driving motor (102) is connected with the ducted fan tilting mechanism (10) through the motor mounting seat (13); and the cross-shaped machine arm (5) is fixed on the top of the mounting platform (6).

4. The tiltable ducted fan flying car of claim 3, wherein: The cross-shaped machine arm (5) comprises a central mounting cavity and four hollow supporting arms.

5. The tiltable ducted fan flying car of claim 4, wherein: The ducted fan tilting mechanism (10) comprises a tilting motor (103) as a power source, a self-locking reducer mechanism and a tilting rod (108) for transmitting power; the input end of the reducer mechanism is connected with the output end of the tilting motor (103), and the output end is drivingly connected with one end of the tilting rod (108); the other end of the tilting rod (108) extends along the supporting arm of the cross-shaped machine arm (5) and is fixedly connected with the motor mounting seat (13) of the ducted fan; when the tilting motor (103) works, the tilting rod (108) is driven to rotate through the reduction transmission mechanism, and the ducted fan fixedly connected thereto is further driven to tilt around the axis of the supporting arm, so that the direction of the thrust is independently and accurately adjusted.

6. The tiltable ducted fan flying car of claim 5, wherein: Assume that the takeoff gross weight of the flying car includes the structure weight , the electric power system weight , the power battery weight , the fixed equipment weight , and the payload weight , so the takeoff gross weight satisfies the following formula: ， wherein, is the structural weight, is the electric power system weight, is the power battery weight, is the fixed equipment weight, is the payload weight, is the number of passengers, is the handling system weight, is the avionics system weight.

7. The tiltable ducted fan flying car of claim 6, wherein: The aerodynamic layout of four ducted fans is adopted, and the additional load such as wind resistance encountered in actual flight is considered, so the thrust of the ducted fan is: : ， This thrust value is the core input and constraint for subsequent ducted fan aerodynamic design; the simplified ducted propeller design method proposed by Gao Yongwei is adopted, based on the momentum theorem of fluid dynamics. Design; According to the incompressible continuity equation and momentum theory, the thrust of the ducted fan is derived : ， wherein, is the incoming air density, is the bypass fan exit area, is the incoming air axial velocity, is the bypass fan exit flow velocity, is the rotor disc area, is the rotor disc flow velocity, is the rotor disc airflow rate: ， wherein, is the specific speed, is the rotational speed of the blade, is the total pressure generated by the blade disc, is the diameter of the blade disc, is the coefficient, is the static pressure difference generated by the blade disc taking into account losses, is the static pressure difference generated by the blade disc not taking into account losses, is the static pressure difference generated by the blade disc not taking into account losses, the air flow through the ducted fan having an inlet loss and an outlet loss, the inlet loss being related to the ratio r / D1 of the radius at the inlet of the duct and the diameter of the blade disc, is the inlet loss coefficient, is the outlet loss coefficient, is the sum of the loss coefficients.

8. The tiltable ducted fan flying car of claim 7, wherein: Volume of the duct housing (14) is represented as: ， wherein is the outer diameter of the duct shell (14), is the inner diameter of the duct shell (14) which is larger than the diameter of the propeller disc, depending on the wall thickness of the duct shell, the overall shape of the duct shell (14) being designed as a circle, is the height of the duct shell (14); According to the material density of the carbon fiber composite material and the volume of the duct housing (14) , the weight of the duct housing (14) is expressed as: ， Since the ducted fan includes a propeller, a duct housing, a propeller driving motor, considering the motor selection and the weight of other components, the weight of the ducted fan is represented as: =1.5 。 9. The tiltable ducted fan flying car of claim 8, wherein: To ensure that the ducted fan tilting mechanism can work reliably and accurately, the driving torque thereof needs to be accurately calculated, and the driving torque needs to overcome three parts of load: load torque , inertial torque when the system starts or brakes , and friction torque , and the total output torque is: ， ， wherein, is the weight of the tiltbar (108), is the weight of the ducted fan, is the distance from the tiltbar center of gravity to the tilt axis, is the distance from the ducted fan assembly center of gravity to the tilt axis, is the system total moment of inertia, is the desired angular acceleration, is the acceleration due to gravity, is the system tilt efficiency accounting for frictional torques; based on the calculated and a selected rated torque of the tilting motor , according to a torque multiplication relation of the reduction gear: ， To ensure The reduction ratio i of the reduction gear of the ducted fan tilt mechanism (10) is determined with a margin.

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