Method, system and equipment for dynamically and stably switching flight modes of hovercar

Abstract

The invention discloses a method, a system and equipment for dynamically and stably switching flight modes of an aerocar, and relates to the technical field of aerocar control. The method comprises the following steps: receiving flight state information of the hovercar, and judging whether a mode switching condition of the hovercar is met or not; if the mode switching condition of the hovercar is met, the flying attitude of the hovercar is adjusted to a stable attitude, and the rotating speed of the rotor wings is adjusted through the controller to maintain the stable attitude in the mode switching process. The motion process of the aerocar in the mode switching process is analyzed in the vertical direction and the horizontal direction, stable landing in the vertical direction is achieved through closed-loop control, it is guaranteed that the speed of landing rear wheels is synchronous with the speed in the horizontal direction through open-loop control, the switching efficiency of the flight modes can be improved, and the reliability of the aerocar is improved. Seamless connection of the hovercar in a low-altitude traffic domain and a ground traffic domain is achieved, meanwhile, the requirement of the hovercar for a take-off and landing site is lowered, and compared with a deceleration hovering process in a traditional method, the method can reduce energy loss during mode switching.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of flying car control technology, in particular to a flying car flight mode dynamic smooth switching method, system and device. BACKGROUND

[0002] Under the background of the release of global low-altitude economic policy dividends and the construction of urban three-dimensional transportation system, flying cars, as an innovative carrier connecting ground transportation and low-altitude travel, are becoming an important fulcrum of future mobile travel ecology. This kind of transportation tool breaks through the boundary of traditional vehicle form, and through the design architecture of land-air integration, it deeply integrates the ground traffic capacity of the car and the low-altitude flight performance of the aircraft, and carries a pure electric power system to realize power output.

[0003] Its core advantage lies in connecting urban road travel and low-altitude flight scenarios through mode switching technology - it can complete regular driving in the ground transportation network, and quickly switch to flight mode according to travel needs to cross geographical barriers or achieve efficient long-distance commuting. This flexible adaptation to multiple scenarios makes it no longer limited to solving traditional traffic congestion problems, but responds to the demand upgrade of instant and personalized travel of modern urban population with a new traffic form, providing a concrete implementation path for building a multi-level three-dimensional transportation network.

[0004] However, the current flying car mode switching scheme is not sufficient, especially for flying cars with multi-rotor structure. The mode switching scheme is based on the mode of traditional multi-rotor aircraft, that is, it needs to go through the processes of deceleration, hovering, landing, wheel starting and acceleration to reach the normal driving state, which has the following significant defects: first, it has limitations on landing sites and requires a dedicated landing pad or open flat area, which greatly limits the application of flying cars in diversified scenarios; second, it needs to be decelerated significantly before landing to enter the hovering state, which consumes a lot of energy and seriously affects energy utilization efficiency; in addition, during mode switching, the vehicle speed fluctuates greatly, resulting in poor driving experience. Therefore, the present application proposes a flying car flight mode dynamic smooth switching method, system and device. SUMMARY

[0005] The purpose of the present application is to provide a flying car flight mode dynamic smooth switching method, system and device, which reduces the requirements of flying cars for landing sites, avoids the energy consumption of complete deceleration during switching, improves the efficiency of mode switching, and is suitable for seamless connection between low-altitude transportation and ground transportation.

[0006] According to the first aspect of the present application, in order to achieve the above-mentioned purpose, the present application provides the following technical scheme: a flying car flight mode dynamic smooth switching method applied in the field of flying cars, wherein the flying car is configured with an accelerometer, a gyroscope, a visual speed meter, an ultrasonic ranging module, a barometer and an attitude sensor, and specifically comprises the following steps:

[0007] receiving the aerial vehicle flight state information, determining whether the aerial vehicle mode switching condition is met, wherein the flight state information comprises horizontal speed, vertical speed, height above ground and flight direction;

[0008] if the aerial vehicle mode switching condition is met, adjusting the aerial vehicle flight attitude to a stable attitude, and adjusting the rotor speed to maintain the stable attitude during the mode switching process by the controller, wherein the stable attitude is that the pitch angle and roll angle of the aerial vehicle are zero, and the horizontal component of the rotor thrust is zero;

[0009] based on the adjusted stable attitude, performing mode switching, calculating the vertical acceleration measured by the accelerometer and the target vertical acceleration, and adjusting the rotor lift by the controller to realize stable landing in the vertical direction;

[0010] calculating the instantaneous horizontal speed according to the horizontal acceleration measured by the accelerometer, and controlling the wheel speed by the controller so that the wheel speed at the end of the mode switching is equal to the instantaneous horizontal speed, wherein the wind resistance interference error is reduced by Kalman filtering algorithm when calculating the horizontal speed;

[0011] when the height of the aerial vehicle is reduced to 0, the aerial vehicle completes mode switching from flight mode to driving mode.

[0012] Further, the aerial vehicle mode switching condition is that the horizontal speed is not less than 5m / s, the vertical speed is not less than 1m / s, the height above ground is between 1m and 10m, and the flight direction is towards the driving route after mode switching.

[0013] Further, the horizontal speed and the vertical speed are collected by a visual speed meter and an accelerometer, and the height above ground is measured by a barometer and an ultrasonic ranging module.

[0014] Further, if the aerial vehicle mode switching condition is met, the aerial vehicle flight attitude is adjusted to a stable attitude, and the rotor speed is adjusted to maintain the stable attitude during the mode switching process by the controller, wherein the stable attitude is that the pitch angle and roll angle of the aerial vehicle are zero, and the horizontal component of the rotor thrust is zero, and the specific process is as follows:

[0015] The gyroscope outputs real-time pitch angle and roll angle data. Due to acceleration, the gyroscope produces zero drift error, so the real-time acceleration measured by the accelerometer is used to compensate the attitude zero drift error of the gyroscope, and the specific calculation process is as follows:

[0016]

[0017] wherein ω comps is the compensated attitude parameter, ω means is the attitude parameter measured by the gyroscope, and Sg is a gravity sensitive coefficient, is an acceleration vector;

[0018] The controller adjusts the four-rotor speed according to the attitude error signal, so that the pitch angle and roll angle error converges to ≤0.5°.

[0019] Further, based on the adjusted stable attitude, the vertical acceleration measured by the accelerometer is subtracted from the target vertical acceleration, and the rotor lift is adjusted by the controller to achieve stable landing in the vertical direction, as follows:

[0020] (51) The target value of the vertical acceleration during the flying car mode switching process is derived from the dynamics theory, and the specific derivation process is as follows:

[0021]

[0022] where V v0 represents the initial vertical speed; V v (t) represents the instantaneous vertical speed; a v (t) represents the instantaneous vertical acceleration; F l (t) represents the instantaneous lift generated by the flying car rotor; M represents the overall weight of the flying car; g represents the local gravitational acceleration; t and τ are time variables;

[0023] (52) From formulas (1) and (2), the instantaneous vertical speed relationship expression (3) can be obtained:

[0024]

[0025] (53) At the end of the flying car mode stable switching time T, the flying car vertical speed is 0, and the height from the ground is also 0, so the expression needs to be satisfied:

[0026]

[0027] where H represents the height of the flying car from the road;

[0028] (54) The expression of F l (t) is calculated by simultaneously solving formulas (4) and (5), and a closed-loop control method is used to set the lift during mode switching as a constant, and then update the target lift value according to the real-time feedback of the current height and vertical speed of the flying car:

[0029]

[0030] V v = a v T(7)

[0031] where

[0032] Substitute equation (6) and equation (7) to get the vertical target acceleration:

[0033]

[0034] Where, V v is the vertical velocity, H is the height from the ground;

[0035] The accelerometer collects the vertical acceleration in real time, and the difference between the target value a v and the actual value is input to the PID controller; the controller output is the rotor speed adjustment signal, so that F l (t) = M(g-a v ), so that the vertical acceleration reaches the target value a v .

[0036] Further, the instantaneous horizontal velocity is calculated according to the horizontal acceleration measured by the accelerometer, and the wheel speed is controlled by the controller, so that the wheel speed at the end of the mode switching is equal to the instantaneous horizontal velocity, which is as follows:

[0037] (61) In the process of mode switching of the flying car, no horizontal forward power is actively provided, but due to inertia, the flying car will continue to move forward in the horizontal direction, and in the process, it will be affected by air resistance. The size of the instantaneous air resistance F h (t) is represented as:

[0038]

[0039] Where, c represents the air resistance coefficient, which is related to the characteristic area of the flying car, the smoothness and overall shape of the flying car; p represents the air density; S represents the windward area of the flying car; V h (t) represents the instantaneous horizontal velocity; V a (t) represents the wind speed, which is positive when the flying car is against the wind and negative when the flying car is with the wind; then the kinematics relationship in the horizontal direction is represented as:

[0040]

[0041] (62) In order to realize the stability in the process of mode switching, the wheel speed V w of the flying car needs to be consistent with the horizontal velocity V h at the end of the mode switching, and the relationship between the instantaneous horizontal velocity of the flying car is obtained by substituting equations (9), (10) and (11):

[0042]

[0043] Differentiate both sides to get:

[0044]

[0045] Let k = c p S / M, bring in the initial condition V h (0) = V h0 , the solution of the differential equation is:

[0046]

[0047] The required wheel speed when the flying car mode switching is completed is:

[0048]

[0049] In the formula, V h0 is the horizontal initial speed, the coefficient k = c p S / M, c is the air resistance coefficient, p is the air density, S is the windward area, and M is the mass of the flying car;

[0050] (63) When the horizontal speed is calculated, the Kalman filter algorithm is used to reduce the wind resistance interference error:

[0051] Because of the interference in the mode switching process and the difficulty in accurately obtaining the parameter k, the calculated result is quite different from the true result, so the horizontal acceleration a h (t) is measured by the accelerometer, so as to indirectly measure the horizontal speed V h (t), and the calculation process is simplified as:

[0052] V w = V h (t) (16)

[0053] Then the corresponding wheel speed n is:

[0054]

[0055] Wherein, p is the circular constant, and d is the wheel diameter.

[0056] According to the second aspect of the application, the application provides a flying car flight mode dynamic smooth switching system for realizing the flying car flight mode dynamic smooth switching method described in the first aspect, comprising:

[0057] The judging module is used for receiving the flying car flight state information, judging whether the flying car mode switching condition is met, wherein the flight state information includes the horizontal speed, the vertical speed, the height above the ground and the flight direction;

[0058] The adjusting module is used for adjusting the flying car flight attitude to the stable attitude if the flying car mode switching condition is met, and adjusting the rotor speed to maintain the stable attitude by the controller during the mode switching process, wherein the stable attitude is that the pitch angle and the roll angle of the flying car are zero, and the horizontal component of the rotor thrust is zero.

[0059] Vertical direction closed loop control module, for modal switching based on adjusted stable attitude, difference between vertical acceleration measured by accelerometer and vertical direction target acceleration, adjusting rotor lift through controller to realize vertical direction stable landing;

[0060] Horizontal direction open loop control module, for calculating instantaneous horizontal velocity according to horizontal acceleration measured by accelerometer, and controlling wheel speed through controller, so that wheel speed at the end of modal switching is equal to instantaneous horizontal velocity, wherein Kalman filtering algorithm is used to reduce wind resistance interference error when calculating horizontal velocity;

[0061] Modal switching completion module, for completing modal switching of flying car from flight mode to driving mode when the height of flying car is reduced to 0.

[0062] According to the second aspect of the present application, the present application provides a terminal device, comprising a memory, a processor and a computer program stored in the memory and capable of running on the processor, characterized in that when the processor loads and executes the computer program, the flying car flight mode dynamic stable switching method described in the first aspect is adopted.

[0063] The present application at least has the following beneficial effects:

[0064] 1. The present application analyzes the motion process of the flying car in the modal switching process from the vertical and horizontal directions, realizes stable landing in the vertical direction through closed loop control, and ensures that the wheel speed after landing is synchronized with the horizontal direction speed through open loop control, which can improve the switching efficiency of the flight mode and realize seamless connection of the flying car in the low-altitude traffic domain and the ground traffic domain.

[0065] 2. Compared with the traditional modal switching method, the flying car in the present application does not have to go through the process of deceleration hovering, which can reduce the energy loss during modal switching.

[0066] 3. The present application can reduce the requirement for take-off and landing site, and can complete the switching on the road where vehicles run, without worrying about affecting the ground traffic.

[0067] Of course, any product implementing the present application does not necessarily need to achieve all the advantages described above at the same time. BRIEF DESCRIPTION OF DRAWINGS

[0068] Figure 1 The flowchart of the switching method described in the present application;

[0069] Figure 2 The state comparison diagram of the traditional flight mode switching process and the dynamic modal switching process of the present application;

[0070] Figure 3 This is a schematic diagram of the closed-loop control principle for vertical motion during mode switching in this invention.

[0071] Figure 4 This is a schematic diagram of the open-loop control principle for synchronizing the front wheel speed and horizontal speed after mode switching in this invention.

[0072] Figure 5 Simulation diagram of the motion trajectory during the dynamic and smooth switching of flight modes for a flying car. Detailed Implementation

[0073] The technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0074] like Figure 2 As shown, during the mode switching process, the trajectory of the flying car is a smooth curve. Dynamic switching means that the horizontal speed of the flying car does not need to be decelerated during mode switching, and the switching from flight mode to driving mode can be completed while in motion.

[0075] Smooth transition means that the flying car maintains a stable attitude during landing and its vertical velocity is zero at the moment of impact (minimum impact).

[0076] Vertical velocity is related to vertical acceleration, which is mainly determined by propeller lift and gravity. Vertical acceleration can be adjusted by controlling rotor lift.

[0077] Please see Figures 1-5 This invention provides a technical solution: a method for dynamic and smooth switching of flight modes in a flying car, comprising the following steps:

[0078] S1. Receive the flight status information of the flying car and determine whether the conditions for switching modes of the flying car are met. The flight status information includes horizontal speed, vertical speed, altitude above the ground, and flight direction.

[0079] Specifically, before the flight mode switching begins, the flying car needs to meet the switching conditions, that is, the flying car adjusts its speed, altitude and direction to meet the requirements of dynamic flight mode switching. Specifically, the altitude is between 1m and 10m, the horizontal speed is not less than 5m / s, the vertical speed is not less than 1m / s, and the flight direction is along the driving route after the mode switching. The horizontal and vertical speeds are collected by visual speedometers and accelerometers, and the ground clearance is measured by barometers and ultrasonic ranging modules.

[0080] S2. If the flying car mode switching condition is met, adjust the flying car flight attitude to the steady attitude, and adjust the rotor speed through the controller to maintain the steady attitude during the mode switching process, wherein the steady attitude is the flying car pitch angle and roll angle being zero, and the rotor thrust horizontal component being zero, and the specific adjustment is as follows:

[0081] The gyroscope outputs the pitch angle and roll angle data in real time. Due to the zero drift error of the gyroscope caused by acceleration, the real-time acceleration measured by the accelerometer is used to compensate the attitude zero drift error of the gyroscope. The specific calculation process is as follows:

[0082]

[0083] Wherein, ω comps is the compensated attitude parameter, ω means is the attitude parameter measured by the gyroscope, S g is the gravity sensitivity coefficient, is the acceleration vector.

[0084] At the beginning of the flight mode switching, the flying car is adjusted to the steady attitude. In the ideal case, the attitude parameters should be pitch angle 0° and roll angle 0°. The attitude parameters can be measured by the gyroscope, and the error is less than 0.5°.

[0085] The power of the flying car in the flight mode is completely provided by the rotor. When the flying car is tilted, the horizontal component of the rotor thrust provides horizontal power, and the vertical component provides vertical power and offsets the gravity.

[0086] It should be noted that in the steady attitude of the flying car, the pitch angle and roll angle are zero, and the horizontal component of the rotor thrust is zero. At this time, the flying car has no horizontal power. Due to inertia, the flying car will continue to move horizontally in the air, and will be subjected to certain wind resistance during this period. However, due to the large mass of the flying car, the horizontal deceleration caused by wind resistance is not significant.

[0087] S3. Based on the adjusted steady attitude, the mode switching is carried out, the vertical acceleration measured by the accelerometer is subtracted from the vertical target acceleration, and the rotor lift is adjusted through the controller to realize the steady landing in the vertical direction, and the specific adjustment is as follows:

[0088] (S31) The flying car mode switching process needs to strictly control the vertical acceleration to achieve the steady condition. The target value of the vertical acceleration is derived by dynamics theory, and the specific derivation process is as follows:

[0089]

[0090] Wherein, V v0 represents the initial vertical speed; V v(t) represents the instantaneous vertical direction velocity; a v (t) represents the instantaneous vertical direction acceleration; F l (t) represents the instantaneous lift generated by the rotor of the flying car; M represents the overall weight of the flying car; g represents the local gravitational acceleration; t and τ are time variables;

[0091] (S32) The instantaneous vertical velocity relationship expression (3) can be obtained from the formulas (1) and (2):

[0092]

[0093] (S33) The key to smooth switching is that the vertical velocity of the flying car is exactly 0 at the moment T when the mode switching ends, and the height to the road surface is also 0, so the expression needs to be met:

[0094]

[0095] In the formula, H represents the height of the flying car to the road surface;

[0096] (S34) The expression of F l (t) is calculated by simultaneously solving the formulas (4) and (5), but the solution of the time-varying lift is difficult, and there are disturbances in the process, which deviate the actual results from the ideal results, for this, the closed-loop control is used to solve this problem, as shown in Figure 3 , the specific idea is to set the lift in the mode switching process as a constant, and then update the target lift value in real time according to the feedback, the feedback is the current height and vertical direction velocity of the flying car obtained by the sensor in real time, so that the interference can be corrected in real time, and the parameter solving process can be simplified, as follows:

[0097]

[0098] V v = a v T(24)

[0099] Wherein, each motion state parameter is the current value measured by the sensor;

[0100] The above formulas are simultaneously solved to obtain the target vertical direction acceleration parameter

[0101]

[0102] In the formula, V v is the vertical direction velocity, and H is the height from the ground;

[0103] In the closed-loop control process, the vertical direction velocity V v and the height H of the flying car are measured, and the target acceleration value a v, control the rotor of the air car to provide lift to make the vertical acceleration sensor reach the target value a v , repeat the algorithm until the air car completes the mode stable switching;

[0104] S4. Calculate the instantaneous horizontal speed according to the horizontal acceleration measured by the accelerometer, and control the wheel speed through the controller to make the wheel speed equal to the instantaneous horizontal speed at the end of mode switching, wherein the wind resistance interference error is reduced by Kalman filtering algorithm when calculating the horizontal speed, as follows:

[0105] (S41) During the mode switching process, the air car does not actively provide horizontal forward power, but due to inertia, the air car will continue to move forward in the horizontal direction, and during the process, it will be affected by air resistance. The size of the instantaneous air resistance F h (t) is represented as:

[0106]

[0107] Where c represents the air resistance coefficient, which is usually an experimental value, and the characteristic area (windward area) of the air car, the smoothness and overall shape of the air car; ρ represents the air density, and the approximate value of dry air is 1.293 g / L, which needs to be measured in actual application; S represents the windward area of the air car; V h (t) represents the instantaneous horizontal speed; V a (t) represents the wind speed, which is positive when the air car is against the wind and negative when the air car is with the wind;

[0108] Then the kinematics relationship in the horizontal direction is represented as:

[0109]

[0110] (S42) In order to realize the stability in the horizontal direction during mode switching, the wheel speed V w of the air car should be consistent with the horizontal speed V h at the end of mode switching, and the relationship of the instantaneous horizontal speed of the air car can be obtained by combining formulas (9), (10) and (11):

[0111]

[0112] Differentiate both sides to get:

[0113]

[0114] Let k = cρS / M, and bring in the initial condition V h (0) = V h0 , and solve the differential equation to get:

[0115]

[0116] The required wheel speed when the flying car completes mode switching is:

[0117]

[0118] Although the target wheel speed of the flying car can be calculated using formula (15), the calculated result differs significantly from the actual result due to interference during mode switching and the difficulty in accurately obtaining the parameter k. Therefore, the formula (15) is used instead of formula (15). Figure 4 The open-loop control scheme shown reduces the error by measuring the horizontal acceleration a using an accelerometer. h (t), thus indirectly measuring the horizontal velocity V h (t), the solution process can be directly simplified as follows:

[0119] V w =V h (T)(33)

[0120] The corresponding wheel speed n is

[0121]

[0122] Where π is the mathematical constant pi, and d is the diameter of the wheel;

[0123] S5. When the flying car's altitude drops to 0, the flying car completes the mode switch, switching from flight mode to driving mode, and can turn off the rotors for free driving;

[0124] It should be noted that using the real-time acceleration sensor mounted on the flying car simplifies the calculation process of target parameters in the control system. The flying car does not need to measure parameters such as c, ρ, S, and M in advance, but it still needs to determine H and V. h0 V v0 Parameters, however, are not difficult to obtain for intelligent flying cars equipped with multiple sensors:

[0125] It should be noted that this embodiment does not affect the flying car's mode switching in the traditional way; the driver can freely choose the switching method according to actual needs.

[0126] The technical solution of the present invention will be further described below with reference to specific embodiments:

[0127] The flying car's flight structure is similar to that of a typical multi-rotor drone, and its driving structure is similar to that of a regular electric car. The flying car is equipped with necessary sensors such as accelerometers, gyroscopes, visual sensors, ultrasonic ranging modules, and barometers.

[0128] (1) Closed-loop adjustment of motion parameters

[0129] Horizontal speed calibration: Accelerometer (ADXL345) and visual speedometer (OptiFlow V5) data are read by the main controller and fused using a complementary filtering algorithm; for example, if the initial speed is currently detected to be 30 m / s, the electronic speed controller (ESC) is triggered to reduce the horizontal thrust component of the rotor, and the speed is reduced to 15 m / s through a PID controller (proportional coefficient Kp=0.8, integral coefficient Ki=0.2, and differential coefficient Kd=0.1);

[0130] Vertical speed control: The altimeter (MS5611) and the ultrasonic module (HC-SR04) jointly measure the height, for example, when the height decreases from 40 m to 5 m, the vertical speed is 5 m / s, and the error is suppressed to ≤0.3 m / s through Kalman filtering;

[0131] (2) Heading and attitude pre-adjustment

[0132] The visual navigation module (PX4FLOW) recognizes the ground road markings, and the controller drives the rudder to adjust the flight direction, so that the angle between the heading and the target driving route is ≤3°, and the gyroscope (ICM-20948) monitors the yaw angle in real time, and when the deviation exceeds 1°, the rotor differential adjustment is triggered;

[0133] (3) Attitude dynamics stabilization stage (millisecond-level closed-loop control)

[0134] Zero attitude initialization: The nine-axis sensor (ICM-20948) outputs the pitch angle and roll angle at a frequency of 200 Hz, and the controller executes the following calibration and control process:

[0135]

[0136]

[0137] The accelerometer (ADXL345) calculates the gravity acceleration component in real time, compensates for the gyroscope drift, and ensures that the attitude error is ≤0.3°;

[0138] (4) Attitude maintenance control

[0139] The controller executes the following attitude maintenance control process:

[0140]

[0141]

[0142] (4) Vertical direction closed-loop control stage (dynamic precise calculation)

[0143] Target parameter real-time calculation: The ultrasonic module (HC-SR04) measures the wheel ground clearance, for example, the measured value H=5.02 m (error ±0.05 m), and the vertical speed V v= 4.98 m / s, plug into formula:

[0144] Calculate target vertical acceleration, meanwhile back-propagate rotor lift force by dynamics equation: F l (t) = M(g - a v ) = 1000 x (9.81 - 2.47) = 7340 N, where M is measured by load cell (Honeywell 24PC);

[0145] Error correction and hardware driving: Accelerometer (ADXL345) measures vertical acceleration at 1000 Hz sampling rate, when measured value is 2.42 m / s 2 , error Da = 0.05 m / s 2 , controller outputs PWM signal (duty cycle increases 2%) to rotor driving circuit, increases lift force 50 N, control logic as follows:

[0146]

[0147]

[0148] (5) Horizontal velocity synchronous open-loop control phase (inertia-resistance dynamic matching)

[0149] Wind resistance real-time modeling and compensation: for example, when horizontal velocity V h > 10 m / s, F h = 0.3 x 1.293 x 1.89 x (V h + V a ) 2 / 2; real-time wind speed V a is measured by ultrasonic anemometer (Young 05103), downwind is negative, upwind is positive (e.g. V a = 2 m / s, F h increases 10%). Wind resistance acceleration is used to predict horizontal velocity decay. When t = 2 s, V h = 14.76 m / s, decays 0.24 m / s compared with initial value, calculated by formula

[0150] Wheel diameter d = 0.602 m, target rotation speed: Encoder (HEDL5540) measures wheel speed in real time, when measured value is 7.82 r / s, controller outputs current compensation signal (increases 0.5 A) to in-wheel motor, eliminates speed difference, control logic as follows:

[0151]

[0152] ​

[0153] (6) Modal switching verification and system switching

[0154] Switching end determination: The ultrasonic module measures H ≤ 0.05m for 5 consecutive times (threshold adjustable);

[0155] Data recording: Store switching process data (such as vertical acceleration curve, wheel speed synchronization error) to an SD card (FAT32 format), with a sampling frequency of 100Hz, for later analysis;

[0156] (7) Abnormal operating condition handling mechanism

[0157] If a rotor fails, the controller immediately executes the following: the remaining rotor thrust is redistributed (e.g., if one rotor in a quadcopter fails, the thrust of the other three rotors increases by 30%); the strategy is switched down to the traditional "deceleration-hovering-landing" mode to ensure a safe landing;

[0158] (8) Taking the above process parameters as an example, a simulation was performed, and the results are as follows: Figure 5 As shown, the trajectory curve is as expected. Compared with the traditional method, the energy loss is reduced by about 225KJ during the transition from flight mode to a speed of 15m / s, and the mode switching time is reduced from the traditional 20s to 2.5s, which greatly improves the switching efficiency.

[0159] In summary, this invention analyzes the motion process of a flying car during mode switching from both vertical and horizontal directions. It achieves a smooth vertical landing through closed-loop control and ensures that the wheel speed is synchronized with the horizontal speed after landing through open-loop control. This method reduces the requirements of the flying car for take-off and landing sites, avoids the energy consumption of complete deceleration during switching, and improves the efficiency of mode switching. It is suitable for seamless connection between low-altitude transportation and ground transportation.

[0160] Example 2:

[0161] This embodiment provides a dynamic and smooth switching system for flight modes of a flying car, used to implement the dynamic and smooth switching method for flight modes of a flying car described in Embodiment 1, including:

[0162] The judgment module is used to receive the flight status information of the flying car and determine whether the conditions for the mode switching of the flying car are met. The flight status information includes horizontal speed, vertical speed, altitude above the ground and flight direction.

[0163] The adjustment module is used to adjust the flight attitude of the flying car to a stable attitude if the mode switching conditions of the flying car are met, and to maintain a stable attitude by adjusting the rotor speed through the controller during the mode switching process. The stable attitude is when the pitch angle and roll angle of the flying car are zero and the horizontal component of the rotor thrust is zero.

[0164] The vertical direction closed-loop control module is used for mode switching based on the adjusted stable attitude, obtaining the difference between the vertical acceleration measured by the accelerometer and the vertical direction target acceleration, adjusting the rotor lift through the controller, and realizing the stable landing in the vertical direction;

[0165] The horizontal direction open-loop control module is used for calculating the instantaneous horizontal velocity according to the horizontal acceleration measured by the accelerometer, and controlling the wheel speed through the controller, so that the wheel speed is equal to the instantaneous horizontal velocity at the end of the mode switching, wherein the wind resistance interference error is reduced through the Kalman filtering algorithm when the horizontal velocity is calculated.

[0166] The mode switching completion module is used for completing the mode switching of the flying car from the flight mode to the driving mode when the height of the flying car is reduced to 0.

[0167] Embodiment three:

[0168] The application provides a terminal device, which comprises a memory, a processor and a computer program stored in the memory and capable of running on the processor, the memory stores the computer program capable of running on the processor, and the processor loads and executes the computer program, and the flying car flight mode dynamic stable switching method described in the embodiment one is adopted.

[0169] It should be noted that the terminal device can be a computer device such as a desktop computer, a notebook computer or a cloud server, and the terminal device comprises but is not limited to a processor and a memory, for example, the terminal device can further comprise an input / output device, a network access device and a bus, etc.

[0170] Further, the processor can be a central processing unit (CPU), of course, according to the actual use, other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), ready programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc., the general-purpose processor can be a microprocessor or any conventional processor, etc., and the application does not limit this.

[0171] It should be noted that in this paper, the relationship terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between the entities or operations. Moreover, the terms "include", "contain" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or device.

[0172] Those of ordinary skill in the art will appreciate that the above described terms are understood in their specific context within the present application. When an element is referred to as being "mounted," "attached," "connected" or "disposed" on another element, it can be directly on the other element or intervening elements can also be present. When an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements can also be present. As used herein the terms "vertical," "horizontal," "upper," "lower," "left," "right," and the like are used for illustration only and are not intended to be limiting.

[0173] While embodiments of the application have been shown and described, it is to be understood that various modifications, substitutions, combinations, and variations can be made in the embodiments without departing from the spirit and scope of the present application, which is defined by the appended claims and their equivalents.

[0174] In the description of the specification, reference to "one embodiment", "an example", "a specific example" or the like means that a particular feature, structure, material or characteristic is included in at least one embodiment or example of the disclosure. The appearances of the above described terms in various places in the specification do not necessarily refer to the same embodiment or example. Moreover, the particular features, structures, materials or characteristics can be combined in any suitable manner in one or more embodiments or examples.

Claims

1. A method for dynamically and smoothly switching between flight and ground modes of an air car, applied to the field of air cars, wherein an accelerometer, a gyroscope, a visual speedometer, an ultrasonic ranging module, a barometer, and an attitude sensor are configured on the air car, and the method is characterized in that, Specifically comprising the following steps: Receiving the flying car flight state information, judging whether the flying car mode switching condition is met, wherein the flight state information includes horizontal speed, vertical speed, height above ground and flight direction; If the flying car mode switching condition is met, adjusting the flying car flight attitude to a stable attitude, and adjusting the rotor speed through the controller to maintain the stable attitude during the mode switching process, wherein the stable attitude is that the pitch angle and roll angle of the flying car are zero, and the horizontal component of the rotor thrust is zero; Based on the adjusted stable attitude, the mode switching is carried out, the vertical acceleration measured by the accelerometer is subtracted from the vertical direction target acceleration, the rotor lift is adjusted through the controller, and vertical direction stable landing is realized; According to the horizontal acceleration measured by the accelerometer, the instantaneous horizontal speed is calculated, and the wheel speed is controlled through the controller, so that the wheel speed at the end of the mode switching is equal to the instantaneous horizontal speed, wherein the wind resistance interference error is reduced through the Kalman filtering algorithm when calculating the horizontal speed; When the height of the flying car is reduced to 0, the flying car completes the mode switching from the flight mode to the driving mode.

2. The flying car flying mode dynamic smooth switching method according to claim 1, characterized in that: The flying car mode switching condition is specifically that the horizontal speed is not less than 5 m / s, the vertical speed is not less than 1 m / s, the height above ground is between 1 m and 10 m, and the flight direction is towards the driving route after the mode switching.

3. The flying car flying mode dynamic smooth switching method according to claim 2, characterized in that: The horizontal speed and the vertical speed are collected by a visual speed meter and an accelerometer, and the height above ground is measured by a barometer and an ultrasonic ranging module.

4. The flying car flying mode dynamic smooth switching method according to claim 3, characterized in that: If the flying car mode switching condition is met, adjusting the flying car flight attitude to a stable attitude, and adjusting the rotor speed through the controller to maintain the stable attitude during the mode switching process, wherein the stable attitude is that the pitch angle and roll angle of the flying car are zero, and the horizontal component of the rotor thrust is zero, specifically as follows: The gyroscope outputs real-time pitch angle and roll angle data. Due to the acceleration, the gyroscope produces zero drift error, so the real-time acceleration measured by the accelerometer is used to compensate the attitude zero drift error of the gyroscope, and the specific calculation process is as follows: wherein ω comps is the compensated attitude parameter, ω means is the gyroscope measured attitude parameter, S g is the gravity sensitive coefficient, is the acceleration vector; The controller adjusts the four-rotor speed according to the attitude error signal, so that the pitch angle and roll angle error converges to ≤0.5°.

5. The flying car flying mode dynamic smooth switching method according to claim 4, characterized in that: Based on the adjusted stable attitude, the mode switching is carried out, the vertical acceleration measured by the accelerometer is subtracted from the vertical direction target acceleration, the rotor lift is adjusted through the controller, and vertical direction stable landing is realized, specifically as follows: (51) The target value of the vertical acceleration during the flying car mode switching process is derived by dynamics theory, and the specific derivation process is as follows: where V v0 V represents the initial vertical velocity; V v (t) represents the instantaneous vertical velocity; a v (t) represents the instantaneous vertical acceleration; F l (t) represents the instantaneous lift generated by the rotor of the flying car; M represents the total weight of the flying car; g represents the local gravitational acceleration; t and τ are time variables; (52) From formulas (1) and (2), the instantaneous vertical speed relationship expression (3) can be obtained: (53) At the end of the flying car mode stable switching time T, the vertical speed of the flying car is 0, and the height above ground is also 0, so the expression needs to be met: In the formula, H represents the height of the flying car above the ground; (54) F is calculated by simultaneous equations (4) and (5) l (t) is expressed, and a closed-loop control mode is adopted to set the lift during the modal switching process as a constant, and then the target lift value is updated according to the real-time acquisition of the current height and vertical direction speed feedback of the air car: V v = a v T (7) In the formula, The vertical direction target acceleration is obtained by combining formula (6) and formula (7): In the formula, V v is the vertical direction velocity, and H is the height from the ground. The accelerometer collects vertical acceleration in real time, and the difference between the target value a v is taken as the input of the PID controller; the controller output is the rotor speed adjustment signal, which makes F l (t) = M(g-a v ), so that the vertical acceleration reaches the target value a v .

6. The flying car flying mode dynamic smooth switching method according to claim 5, characterized in that: According to the horizontal acceleration measured by the accelerometer, the instantaneous horizontal speed is calculated, and the wheel speed is controlled through the controller, so that the wheel speed at the end of the mode switching is equal to the instantaneous horizontal speed, specifically as follows: (61) In the process of switching the mode of the flying car, no horizontal forward power is actively provided, but due to inertia, the flying car will continue to move forward in the horizontal direction, and in the process, it will be affected by air resistance, and the instantaneous air resistance F h (t) is expressed as: wherein c represents the air resistance coefficient, which is related to the characteristic area of the flying car, the smoothness and overall shape of the flying car; p represents the air density; S represents the windward area of the flying car; V h (t) represents the horizontal direction instantaneous speed; V a (t) represents the wind speed, which is positive when the flying car is against the wind and negative when the flying car is with the wind; the horizontal direction kinematics relationship is represented as: (62)In order to realize the smoothness of the horizontal direction in the mode switching process, the air car wheel speed V w The horizontal speed V h Need to be consistent, simultaneous equations (9), (10) and (11) are obtained by air car horizontal instantaneous speed relationship: Differentiate both sides simultaneously to get: Let k = cρs / M, and substitute the initial condition V h (0) = V h0 , the solution of the differential equation is: The required wheel speed when the flying car mode switching is completed is: where V h0 is the horizontal initial velocity, and the coefficient k = c pS / M, where c is the air resistance coefficient, p is the air density, S is the windward area, and M is the mass of the flying car. (63) The wind resistance interference error is reduced by Kalman filtering algorithm when the horizontal speed is calculated: Because of the disturbance in the process of modal switching and the difficulty in obtaining the parameter k accurately, the calculated result is quite different from the real result. Therefore, the horizontal acceleration a h (t) is measured by the accelerometer, so as to indirectly measure the horizontal velocity V h (t) and simplify the solving process. V w = V h (T) (16) The corresponding wheel speed n is: Wherein, π is the circular constant, and d is the wheel diameter.

7. A flying car flight mode dynamic smooth switching system for implementing the flying car flight mode dynamic smooth switching method of any one of claims 1 to 6, characterized in that, Comprise: The judging module is used for receiving the flying car flight state information, judging whether the flying car mode switching condition is met, wherein the flying car flight state information comprises horizontal speed, vertical speed, height above ground and flight direction; The adjusting module is used for adjusting the flying car flight attitude to the steady attitude if the flying car mode switching condition is met, and adjusting the rotor speed through the controller to maintain the steady attitude during the mode switching, wherein the steady attitude is that the pitch angle and roll angle of the flying car are zero, and the horizontal component of the rotor thrust is zero; The vertical direction closed loop control module is used for mode switching based on the adjusted steady attitude, calculating the difference between the vertical acceleration measured by the accelerometer and the vertical direction target acceleration, adjusting the rotor lift through the controller, and realizing the vertical direction steady landing; The horizontal direction open loop control module is used for calculating the instantaneous horizontal speed according to the horizontal acceleration measured by the accelerometer, and controlling the wheel speed through the controller, so that the wheel speed is equal to the instantaneous horizontal speed when the mode switching is completed, wherein the wind resistance interference error is reduced by Kalman filtering algorithm when the horizontal speed is calculated; The mode switching completion module is used for completing the mode switching of the flying car from the flight mode to the driving mode when the height of the flying car is reduced to 0.

8. A terminal device comprising a memory, a processor, and a computer program stored in the memory and capable of running on the processor, characterized in that, The processor loads and executes the computer program, and the flying car flight mode dynamic steady switching method in any one of claims 1 to 6 is adopted.

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