An emergency driving method for a vehicle with four-wheel independent drive and steering when three wheels fail.

Abstract

This invention belongs to the field of automotive technology, specifically disclosing an emergency driving method for a vehicle with four-wheel independent drive and steering in the event of a three-wheel failure. The method includes: an emergency driving method comprising: Method 1: a four-wheel independent steering method; Method 2: a single-wheel drive steering method; and Method 3: a wheel braking method. The four-wheel independent steering method is used to independently control the inner and outer turning angles of the wheels; the single-wheel drive steering method is used to calculate the turning angles of the four wheels; and the wheel braking method is used to limit the braking force of the wheels. In traditional vehicles, after three wheels fail, the vehicle lacks driving capability, its overall yaw moment is always biased, and the rear two wheels cannot steer, making forward movement impossible. However, in a fully vectored vehicle, when driving straight, the direction of the still-operating drive wheel can be made to pass through the center of the vehicle, while the steering direction of the other three wheels remains horizontal with that wheel, thus eliminating the yaw moment and enabling straight-line driving.

Description

Technical Field

[0001] This invention relates to the field of automotive technology, specifically to an emergency driving method for a vehicle with four-wheel independent drive and steering in the event of a three-wheel failure. Background Technology

[0002] As the electric vehicle market expands, more and more cars are adopting distributed drive solutions, namely wheel-side motors or wheel hub motors. Compared with traditional fuel vehicles, four-wheel hub motor-driven electric vehicles are a typical overdrive system, which can effectively improve vehicle operation stability and safety. However, due to the large number of motors and the complex working environment, the probability of motor failure will also increase. When a car motor fails, it will cause unequal driving forces on both sides, which will lead to vehicle instability.

[0003] Based on the number and location of the failed drive motors, drive motor failure modes can be classified into the following five categories:

[0004] (1) The drive motor of a single wheel fails;

[0005] (2) Both drive motors located on opposite sides of the vehicle fail simultaneously;

[0006] (3) The two drive motors located on the same side of the vehicle fail simultaneously;

[0007] (4) All three drive motors fail simultaneously;

[0008] (5) All four drive motors fail simultaneously. Summary of the Invention

[0009] The purpose of this invention is to provide an emergency driving method for a vehicle with four-wheel independent drive and steering in the event of a three-wheel failure, in order to solve the above-mentioned problems.

[0010] To achieve the above objectives, the present invention provides the following technical solution: a method for emergency driving of a vehicle with four-wheel independent drive and steering when three wheels fail, characterized in that it includes:

[0011] Emergency driving method, wherein the emergency driving method is:

[0012] Method 1: Four-wheel independent steering method;

[0013] Method 2: Single-wheel drive steering method;

[0014] Method 3: Wheel braking method;

[0015] The four-wheel independent steering method is used to independently control the relationship between the inner and outer steering angles of the wheels; the single-wheel drive steering method is used to calculate the steering angles of the four wheels; and the wheel braking method is used to limit the braking force of the wheels.

[0016] The four-wheel independent steering method is as follows:

[0017] a and b represent the track width and wheelbase of the four-wheel independent steering vehicle, respectively; G is the vehicle's center of gravity; R is the turning radius of the center of gravity; θ1, θ2, θ3, and θ4 are the ideal steering angles of the left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively. Based on the Ackermann steering principle, the relationship between the inner and outer steering angles of the four-wheel independent steering vehicle can be obtained:

[0018]

[0019] Based on the actual rotation angle θ i and the ideal corner deviation value Δθ i The proportional adjustment coefficient μ of the output speed of each wheel steering actuator is obtained. i ;

[0020]

[0021] In the formula: Corresponding to Figure 1 The left front wheel, right front wheel, left rear wheel, and right rear wheel;

[0022] When the vehicle performs independent steering, the proportional adjustment coefficient μ is used. i The output speed ω of each wheel steering actuator can be determined. i ,ω i The conditions for synchronous motion should be met as follows:

[0023]

[0024] The four wheels are controlled by independent hub motors with torques of T1, T2, T3, and T4 respectively.

[0025] First, taking the left front wheel as an example where it functions normally, its torque is T1. When driving straight, the driving force of one of its wheels must pass through the car's center of gravity, resulting in a yaw moment of 0. The steering directions of the other three wheels must remain parallel to this driving wheel. The magnitude of this turning angle can be derived from geometric relationships:

[0026]

[0027] Its driving force is: F t =T t1 R = T m1 iηR

[0028] T t1 T represents the drive torque of the left front wheel. m1 Where i is the output torque of the motor, i is the gear ratio of the reducer, η is the transmission efficiency, and R is the effective radius of the wheel.

[0029] Its resistance formula is:

[0030] F w =0.5ρC w Av 2

[0031] Where F w Where ρ is air resistance, A is air density, and C is the frontal area. w Where v is the drag coefficient and v is the vehicle speed;

[0032] The slope resistance is F f ,

[0033] F f =Wf

[0034] W is the total weight of the vehicle, and f is the rolling resistance coefficient;

[0035] Its driving equation is:

[0036] F t =F w +F f +F i +F j

[0037] Where F i F j These are acceleration resistance and gradient resistance, respectively.

[0038] The single-wheel drive steering method is as follows:

[0039] make make The vehicle's center coordinates are (0, 0), and the coordinates of the left front, right front, left rear, and right rear wheels are (0, y0), (x0, y0-y1), (-x0, y1-y0), and (0, -y0) respectively.

[0040] Because of the four-wheel independent steering, the vehicle has a high degree of steering freedom, and the steering center can be arbitrarily determined. Here, the coordinates of the steering center are determined as (-R, 0), where R is the steering radius.

[0041] The four-wheel steering angle is calculated based on the above coordinate positions:

[0042]

[0043] Preferably, the wheel braking method is as follows:

[0044] F b1 F b2 The braking forces are respectively applied to the left front wheel and the right rear wheel. If there is a difference in braking force between the two wheels, namely the right front wheel and the left rear wheel, a yaw moment will be generated, which will disrupt the stability of the entire vehicle. To avoid this situation, the two wheels are directly de-braked.

[0045] Compared with the prior art, the beneficial effects of the present invention are:

[0046] This invention can be applied to fully vector-driven vehicles, specifically those with independent four-wheel drive and steering. It provides an emergency driving method for vehicles where three-wheel drive fails, only one wheel is functioning normally, and all four steering wheels remain operational. This includes basic driving, steering, and braking functions, allowing the driver to continue driving for a period in emergencies. Compared to traditional distributed drive vehicle safety control, this invention addresses not only single-wheel or two-wheel failures on opposite sides, but directly tackles three-wheel failure in fully vector-driven vehicles, providing control strategies for drive, steering, and braking while maintaining basic functions to handle emergencies. It utilizes single-wheel drive combined with four-wheel steering to achieve straight-line driving and steering. In traditional vehicles, three-wheel failure results in a loss of driving capability; the vehicle's yaw moment is always off-center, and the rear two wheels cannot steer, preventing forward movement. However, in fully vector-driven vehicles, during straight-line driving, the direction of the still-functioning drive wheel can pass through the vehicle's center, while the other three wheels maintain a horizontal steering direction relative to that wheel, thus eliminating yaw moment and enabling straight-line driving. Attached Figure Description

[0047] Figure 1 This is a schematic diagram of the four-wheel independent steering of the present invention;

[0048] Figure 2 This is a schematic diagram of the single-wheel drive straight-line driving of the present invention;

[0049] Figure 3 This is a schematic diagram of the single-wheel drive steering of the present invention;

[0050] Figure 4 This is a schematic diagram of the wheel braking system of the present invention. Detailed Implementation

[0051] 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 some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0052] In the description of this invention, it should be noted that the terms "vertical," "upper," "lower," "horizontal," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0053] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0054] Please see Figure 1-4 The present invention provides a technical solution: an emergency driving method for a vehicle with four-wheel independent drive and steering in the event of a three-wheel failure, comprising:

[0055] Emergency driving method, wherein the emergency driving method is:

[0056] Method 1: Four-wheel independent steering method;

[0057] Method 2: Single-wheel drive steering method;

[0058] Method 3: Wheel braking method;

[0059] The four-wheel independent steering method is used to independently control the relationship between the inner and outer steering angles of the wheels; the single-wheel drive steering method is used to calculate the steering angles of the four wheels; and the wheel braking method is used to limit the braking force of the wheels.

[0060] The four-wheel independent steering method is as follows:

[0061] a and b represent the track width and wheelbase of the four-wheel independent steering vehicle, respectively; G is the vehicle's center of gravity; R is the turning radius of the center of gravity; θ1, θ2, θ3, and θ4 are the ideal steering angles of the left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively. Based on the Ackermann steering principle, the relationship between the inner and outer steering angles of the four-wheel independent steering vehicle can be obtained:

[0062]

[0063] Based on the actual rotation angle θ i and the ideal corner deviation value Δθ i The proportional adjustment coefficient μ of the output speed of each wheel steering actuator is obtained. i ;

[0064]

[0065] In the formula: Corresponding to Figure 1 The left front wheel, right front wheel, left rear wheel, and right rear wheel;

[0066] When the vehicle performs independent steering, the proportional adjustment coefficient μ is used.i The output speed ω of each wheel steering actuator can be determined. i ,ω i The conditions for synchronous motion should be met as follows:

[0067]

[0068] The four wheels are controlled by independent hub motors with torques of T1, T2, T3, and T4 respectively.

[0069] First, taking the left front wheel as an example where it functions normally, its torque is T1. When driving straight, the driving force of one of its wheels must pass through the car's center of gravity, resulting in a yaw moment of 0. The steering directions of the other three wheels must remain parallel to this driving wheel. The magnitude of this turning angle can be derived from geometric relationships:

[0070]

[0071] Its driving force is: F t =T t1 R = T m1 iηR

[0072] T t1 T represents the drive torque of the left front wheel. m1 Where i is the output torque of the motor, i is the gear ratio of the reducer, η is the transmission efficiency, and R is the effective radius of the wheel.

[0073] Its resistance formula is:

[0074] F w =0.5ρC w Av 2

[0075] Where F w Where ρ is air resistance, A is air density, and C is the frontal area. w Where v is the drag coefficient and v is the vehicle speed;

[0076] The slope resistance is F f ,

[0077] F f =Wf

[0078] W is the total weight of the vehicle, and f is the rolling resistance coefficient;

[0079] Its driving equation is:

[0080] F t =F w +F f +F i +F j

[0081] Where F i Fj These are acceleration resistance and gradient resistance, respectively.

[0082] The single-wheel drive steering method is as follows:

[0083] Regarding the steering requirements of a car, this section provides a comprehensive vehicle steering method, including calculations of four-wheel steering angles, driving forces, and yaw moments; for example... Figure 3 The single-wheel drive steering method shown is relatively complex to calculate the four-wheel steering angle, requiring geometric calculation. The intersection of the center of the left front wheel and the center of the right rear wheel passes through the center of the vehicle. To simplify the calculation, a coordinate system with the vehicle center as the origin is established, and the line connecting the center of the drive wheel to the vehicle center is the x-axis. Under this coordinate system, the various coordinates are calculated.

[0084] make make The vehicle's center coordinates are (0, 0), and the coordinates of the front left, front right, rear left, and rear right wheels are (0, y0), (x0, y0-y1), respectively.

[0085] (-x0, y1-y0), (0, -y0);

[0086] Because of the four-wheel independent steering, the vehicle has a high degree of steering freedom, and the steering center can be arbitrarily determined. Here, the coordinates of the steering center are determined as (-R, 0), where R is the steering radius.

[0087] The four-wheel steering angle is calculated based on the above coordinate positions:

[0088]

[0089] The aforementioned turning angles need to be distinguished by direction in order to ensure proper steering.

[0090] Furthermore, the wheel braking method is as follows:

[0091] For braking stability, the drive wheels and diagonally opposite wheels are braked, while the side wheels are not braked. Taking the left front wheel as an example, when braking, only the left front wheel and the right rear wheel brake, while the right front wheel and the left rear wheel do not participate in braking.

[0092] At the same time, the braking force is limited. Under unstable conditions, excessive braking force can easily cause dangerous situations such as skidding, fishtailing, or even rollover.

[0093] F b1 ,F b2 The braking forces are respectively applied to the left front wheel and the right rear wheel. If there is a difference in braking force between the two wheels, namely the right front wheel and the left rear wheel, a yaw moment will be generated, which will compromise the stability of the vehicle. To avoid this situation, the two wheels are not braked. The braking forces of the drive wheels and the diagonally opposite wheels pass through the center of the vehicle, and the difference in braking force will not cause the vehicle to become unstable.

[0094] Furthermore, this invention provides an emergency driving method for vehicles with four-wheel independent drive and four-wheel independent steering, applicable to situations where three-wheel drive fails, only one wheel is functioning normally, and all four wheels still operate normally. This method includes basic drive, steering, and braking functions, helping the driver continue driving for a period in an emergency. Compared to traditional distributed drive vehicle drive failure safety control, this invention addresses not only single-wheel failure or failure of two wheels on opposite sides, but directly tackles three-wheel failure in fully vectored vehicles, proposing control strategies and providing drive, steering, and braking control methods to maintain basic functions and cope with emergencies. It uses single-wheel drive combined with four-wheel steering to achieve straight-line driving and steering functions. In traditional vehicles, after three wheels fail, the vehicle lacks driving capability; the yaw moment is always off-center, and the rear two wheels cannot steer, preventing forward movement. However, in fully vectored vehicles, when driving straight, the direction of the still-operating drive wheel can pass through the center of the vehicle, while the other three wheels maintain a horizontal steering direction with that wheel, thus eliminating the yaw moment and enabling straight-line driving.

[0095] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for emergency driving of a vehicle with four-wheel independent drive and steering when three wheels fail, characterized in that: include; Emergency driving method, wherein the emergency driving method is: Method 1: Four-wheel independent steering method; Method 2: Single-wheel drive steering method; Method 3: Wheel braking method; The four-wheel independent steering method is used to independently control the relationship between the inner and outer steering angles of the wheels; the single-wheel drive steering method is used to calculate the steering angles of the four wheels; the wheel braking method is used to limit the braking force of the wheels. The four-wheel independent steering method is as follows: a and b represent the track width and wheelbase of the four-wheel independent steering vehicle, respectively; G is the vehicle's center of gravity; R is the turning radius of the center of gravity; θ1, θ2, θ3, and θ4 are the ideal steering angles of the left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively. Based on the Ackermann steering principle, the relationship between the inner and outer steering angles of the four-wheel independent steering vehicle can be obtained: Based on the actual rotation angle θ i and the ideal corner deviation value Δθ i The proportional adjustment coefficient μ of the output speed of each wheel steering actuator is obtained. i ; In the formula: These correspond to the left front wheel, right front wheel, left rear wheel, and right rear wheel in Figure 1, respectively. When the vehicle performs independent steering, the proportional adjustment coefficient μ is used. i The output speed ω of each wheel steering actuator can be determined. i ,ω i The conditions for synchronous motion should be met as follows: The four wheels are controlled by independent hub motors with torques of T1, T2, T3, and T4 respectively. First, taking the left front wheel as an example where it functions normally, its torque is T1. When driving straight, the driving force of one of its wheels must pass through the car's center of gravity, resulting in a yaw moment of 0. The steering directions of the other three wheels must remain parallel to this driving wheel. The magnitude of this turning angle can be derived from geometric relationships: Its driving force is: F t =T t1 R = T m1 iηR T t1 T represents the drive torque of the left front wheel. m1 Where i is the output torque of the motor, i is the gear ratio of the reducer, η is the transmission efficiency, and R is the effective radius of the wheel. Its resistance formula is: F w =0.5ρC w Of 2 Where F w Where ρ is air resistance, A is air density, and C is the frontal area. w Where v is the drag coefficient and v is the vehicle speed; The slope resistance is F f , F f =Wf W is the total weight of the vehicle, and f is the rolling resistance coefficient; Its driving equation is: F t =F w +F f +F i +F j Where F i F j These are acceleration resistance and gradient resistance, respectively. The single-wheel drive steering method is as follows: make make The vehicle's center coordinates are (0, 0), and the coordinates of the left front, right front, left rear, and right rear wheels are (0, y0), (x0, y0-y1), (-x0, y1-y0), and (0, -y0) respectively. Because of the independent steering of the four wheels, the vehicle has a high degree of steering freedom, and the steering center can be arbitrarily determined. Here, the coordinates of the steering center are determined as (-R, 0), where R is the steering radius. The four-wheel steering angle is calculated based on the above coordinate positions:

2. The emergency driving method for a vehicle with four-wheel independent drive and steering in case of three-wheel failure as described in claim 1, characterized in that: The wheel braking method is as follows: F b1 F b2 The braking forces are respectively applied to the left front wheel and the right rear wheel. If there is a difference in braking force between the two wheels, namely the right front wheel and the left rear wheel, a yaw moment will be generated, which will disrupt the stability of the entire vehicle. To avoid this situation, the two wheels are directly de-braked.

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