An independent steer-by-wire system and control method for a full-vector power chassis

Abstract

The present invention relates to the field of vehicle integrated design and control technology, and provides an independent steer-by-wire system and control method for a full-vector power chassis. The method comprises: determining a driver's steering intention based on forward road information and a steering wheel angle; matching the steering intention with a corresponding driver map curve and combining it with driving parameters to obtain a desired lateral speed and a desired yaw rate; comparing the required centripetal force of the steering intention with the centripetal force that the vehicle can provide under the current driving conditions; selecting a corresponding Ackerman steering map curve to obtain an optimal Ackerman four-wheel steering angle; and finally controlling a steering angle module of the vehicle to perform steering according to the optimal Ackerman four-wheel steering angle, the desired lateral speed, and the desired yaw rate. The present invention can better perform steering control.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle integrated design and control, and in particular to an independent wire-controlled steering system and a control method for a full-vector power chassis. Background Art

[0002] With the continuous development of the automobile industry in recent years, cars have become a necessity for almost every family. However, with the rapid increase in the number of cars, a series of problems such as traffic congestion and parking difficulties have emerged in many cities. A key reason for these problems is that the maneuverability and driving safety of the two-wheel steering vehicles that currently dominate the market need to be improved. Therefore, four-wheel steering vehicles that can adapt to various vehicle usage scenarios (such as turning on the spot, changing lanes sideways, and four-wheel independent steering) have come into being. However, among the mass-produced models currently on the market, only some high-end models are equipped with rear-wheel steering, and the maximum turning angle of the rear-wheel steering is generally 5 to 8 degrees. Since the rear-wheel steering has the same structure as the front-wheel steering, it generally adopts a traditional rack and pinion steering gear, and some adopt worm-type, worm-roller type, and recirculating ball type steering gear. This steering gear still retains the steering trapezoidal structure, and there is still a mechanical constraint between the left and right wheels, so that independent steering control of the left and right wheels cannot be achieved. It only improves the maneuverability of the car to a certain extent, but still cannot achieve functions such as turning in place, lateral lane changing, and four-wheel independent steering, and still cannot meet users' requirements for high vehicle maneuverability. At the same time, traditional non-mechanically decoupled cars are prone to understeer and oversteer when turning. This is because once the steering trapezoid of the car is determined, the turning angle relationship of each tire of the car is also determined.

[0003] The emergence of full-vector powertrain chassis vehicles has undoubtedly solved this problem. Due to their distributed, electric drive, full-vector powertrain chassis are a key category of new energy vehicles. They represent a revolutionary advancement in automotive chassis design. They feature a steering angle module at each wheel, integrating the suspension and steering systems. This eliminates mechanical components like the traditional steering trapezoid and the mechanical connection between the left and right wheels, achieving physical decoupling. This allows wheel angles to be fully controlled by the steering motor, without rigid constraints between wheel angles. This significantly addresses the fundamental issues of understeer and oversteer. However, while the absence of mechanical constraints like the traditional steering trapezoid improves vehicle maneuverability, it also presents significant challenges to handling stability and structural safety. Therefore, it is crucial to design a structurally safe steering angle module for the full-vector powertrain chassis and a universally applicable all-wheel independent steer-by-wire control method that is compatible with the full-vector powertrain. Summary of the Invention

[0004] The present invention provides an independent steer-by-wire system and control method for a full vector power chassis, which can overcome certain defects of the prior art.

[0005] An independent steer-by-wire control method for a full vector power chassis, comprising:

[0006] The driver's steering intention is determined based on the road ahead information and the steering wheel angle. The steering intention is then matched with the corresponding driver map curve and combined with the driving parameters to obtain the desired lateral speed and desired yaw rate. The required centripetal force required by the steering intention is compared with the centripetal force that the vehicle can provide under the current driving conditions to select the corresponding Ackermann steering map curve to obtain the optimal Ackermann four-wheel steering angle. Finally, the wheels are controlled to steer based on the optimal Ackermann four-wheel steering angle, desired lateral speed, and desired yaw rate.

[0007] Furthermore, the determination of the driver's steering intention includes: judging the road conditions ahead based on the road information ahead; if the road ahead is a curve, determining that the driver's steering intention is to turn; if the road ahead is a straight section, combining the steering wheel angle and the vehicle yaw angle to further determine that the driver's steering intention is any one of adjusting posture, changing lanes, and turning in place.

[0008] The driver map curve is obtained through deep learning, including the driver turning map curve, the driver posture adjustment map curve, the driver lane changing map curve, and the driver on-site steering map curve;

[0009] The driver's intention is determined to be turning, which is manifested in vehicle motion as: a desire to obtain a larger yaw rate and a smaller lateral speed compared to other steering intentions. At this time, the vehicle steering mode is in a front and rear wheel out-of-phase mode to facilitate turning action and tracking of the curved road. The driving parameters are combined with the driver's turning map curve to obtain the desired lateral speed and desired yaw rate in the turning mode; the driving parameters include the longitudinal speed at the vehicle's center of mass and the road adhesion coefficient.

[0010] Determine the driver's intention to adjust the attitude, which is manifested in the vehicle's movement as a desire to adjust the yaw rate and lateral speed by a small amount. Combine the driving parameters with the driver's attitude adjustment map curve to obtain the desired lateral speed and desired yaw rate in the attitude adjustment mode.

[0011] The driver's intention is determined to be a lane change, which manifests itself in vehicle motion as a desire for a smaller yaw rate and a larger lateral velocity compared to other steering intentions. The vehicle's steering mode is then in a front and rear wheel in-phase mode to facilitate lane change. The desired lateral velocity and yaw rate in the attitude adjustment mode are then combined with the driving parameter driver's attitude map curve.

[0012] Determine the driver's intention to pivot, which manifests itself in the vehicle's movement as the wheels turning to a specified pivot angle. Combine the driving parameter, the driver's pivot map curve, to obtain the desired lateral velocity and yaw rate in pivot mode.

[0013] Furthermore, the further determination based on the steering wheel angle and the vehicle yaw angle includes: when the vehicle yaw angle is greater than the critical course deviation and there is a steering wheel angle, determining that the driver's steering intention is to adjust the posture; when the vehicle yaw angle is less than the critical course deviation and there is a steering wheel angle, determining that the driver's steering intention is to change lanes; when the vehicle speed tends to 0 or is equal to 0 and the steering wheel angle is at a limit angle, determining that the driver's steering intention is to turn on the spot, wherein the yaw angle = lane line angle - vehicle yaw angle.

[0014] Furthermore, the actual wheel angles of the four wheels of the vehicle are obtained and combined with the corresponding tire cornering stiffness to obtain the actual tire lateral force, which is then combined with the actual tire lateral force, road adhesion coefficient, current yaw angular velocity and lateral velocity to calculate the centripetal force that can be provided.

[0015] Furthermore, if the required centripetal force is greater than the available centripetal force, the available centripetal force needs to be increased, and the optimal Ackerman four-wheel turning angle is determined based on the insufficient Ackerman steering map curve; if the required centripetal force is equal to the available centripetal force, the available centripetal force remains unchanged, and the optimal Ackerman four-wheel turning angle is determined based on the full Ackerman steering map curve; if the required centripetal force is less than the available centripetal force, the available centripetal force needs to be reduced, and the optimal Ackerman four-wheel turning angle is determined based on the excessive Ackerman steering map curve.

[0016] Furthermore, the process of controlling the vehicle steering module also involves differential values ​​corresponding to the desired lateral velocity and the desired yaw rate, which are obtained according to a tracking differentiator, and the bandwidth frequency ω of the tracking differentiator is n The calculation process is as follows:

[0017]

[0018] Where, F represents tire adhesion, F max represents the tire adhesion limit, k is the controller gain, ω n0 For the vehicle speed v x The basic bandwidth frequency under nmax is the maximum bandwidth frequency.

[0019] Specifically, the tracking differentiator adopts a typical second-order system design, and its mathematical expression is:

[0020]

[0021] Calculate the bandwidth frequency ωn After that, the closed-loop transfer function Φ(s) of the tracking differentiator becomes:

[0022]

[0023] Y represents the system response after Laplace transform, U represents the system excitation after Laplace transform, and s is the complex frequency;

[0024] After Laplace inverse transformation, we get:

[0025]

[0026] in, is the second-order differential of the system response y, is the first-order differential of the system response y, let the system response y = x1, x1 is the current state of the system, u = v, v is the target state, that is:

[0027]

[0028] v yd represents the desired lateral velocity, ω d represents the desired yaw rate;

[0029] It can be expressed as the equation of state:

[0030]

[0031] The current state of the system x1 is the transition curve, and x2 is the differential of the transition curve;

[0032] Substituting the above tracking differentiator form into vehicle dynamics control, we get:

[0033] Vehicle lateral direction:

[0034]

[0035] Vehicle yaw direction:

[0036]

[0037] The differential values ​​of the desired yaw rate and the desired lateral velocity are thus obtained, where ω represents the yaw rate.

[0038] An independent steer-by-wire system for a full-vector power chassis includes: an input layer, a control layer, and an execution layer. The input layer includes driver control input, path tracking input, and sensor observation input. The control layer implements an independent steer-by-wire control method for a full-vector power chassis based on input from the input layer to determine corresponding control information and transmit it to the execution layer. The execution layer outputs a corresponding control signal to a controller corresponding to each wheel based on the control information to control a steering angle module of each wheel to achieve steering of the corresponding wheel.

[0039] Furthermore, the driver control input includes a steering wheel angle, the path tracking input includes front road information and a vehicle yaw angle, and the sensor observation input includes a yaw rate, a lateral velocity, and a vehicle speed.

[0040] Furthermore, the control layer includes a steering intention determination module, a speed determination module, a turning angle determination module and an output module.

[0041] The steering intention determination module is used to determine the driver's steering intention based on the front road information and the steering wheel angle;

[0042] The speed determination module is used to match the steering intention with the corresponding driver map curve and obtain the desired lateral speed and the desired yaw rate in combination with the driving parameters;

[0043] The turning angle determination module is used to compare the required centripetal force required for the steering intention with the centripetal force that the vehicle can provide under the current driving conditions, select the corresponding Ackermann steering map curve to obtain the optimal Ackermann four-wheel turning angle;

[0044] The output module is used to output the optimal Ackermann four-wheel steering angle, the desired lateral speed and the desired yaw rate as control information.

[0045] Furthermore, the steering angle module does not include a steering trapezoid.

[0046] The beneficial effects of the present invention are as follows:

[0047] 1) The steering angle module of the present invention eliminates the connection between mechanical components such as the steering trapezoid, achieves structural decoupling, has a higher controllable degree of freedom, can better play the advantages of the control strategy, and thus achieve a higher level of autonomous driving; a spring roller structure is arranged in the four-wheel independent steering angle to balance the lateral force generated during steering, making the angle module structure more reasonable and safe; the angle module can make the wheel's extreme turning angle reach ±90°, and can realize special driving modes such as lateral driving. At the same time, a limit block is arranged at the extreme turning angle to ensure steering safety; different from the traditional four-wheel steering, only two motors are needed to drive the steering gear of the front and rear axles to complete the four-wheel steering. The four wheels of the four-wheel independent steering angle module are completely decoupled in structure, so four steering motors with the same number of wheels are required to drive the steering of each wheel separately. In this way, when the steering motor fails, only the steering of the corresponding wheel will fail, and the steering of the two wheels on the entire axle will not fail.

[0048] 2) By combining various driver curve maps obtained through deep learning, under the same computing power conditions, the driver curve maps obtained through deep learning can achieve higher generalization, while maintaining stability and achieving better steady-state accuracy. Introducing control variables such as lateral velocity and yaw rate can improve the vehicle's handling stability. Simultaneously, only a simple second-order tracking differentiator is required to obtain the required control variables, reducing the complexity of the control system and enabling the control system to achieve the control target without overshoot. The present invention also designs a bandwidth calculation method to accelerate system response.

[0049] 3) By combining various Ackermann steering curve maps obtained through deep learning and inputting tens of millions of real-vehicle test data, the Ackermann steering curve map obtained through deep learning has higher generalization ability. While ensuring stability, it also has better steady-state accuracy and performs better in real vehicles than other theoretical control methods. Furthermore, by considering the relationship between the required centripetal force during steering and the actual centripetal force provided, it can eliminate a series of problems such as understeer and oversteer caused by wheel slip angle. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 Schematic diagram of a flow chart of an independent steer-by-wire control method for a full-vector power chassis in an embodiment.

[0051] Figure 2 This is a diagram of the four-wheel independent steering control framework in the embodiment.

[0052] Figure 3 1 is an Ackerman steering geometry diagram in an embodiment.

[0053] Figure 4 This is a diagram of the four-wheel independent steering driving mode in the embodiment.

[0054] Figure 5 This is a control architecture diagram of an independent steer-by-wire system for a full-vector power chassis according to an embodiment.

[0055] Figure 6 Schematic diagram of the structure of the steering angle module involved in the embodiment.

[0056] Reference numerals

[0057] 1- Spring roller, 2- Steering motor, 3- Limit block, 4- Flange, 5- Gear sleeve, 6- Steering arm, 7- Wheel, 8- Angle sensor. DETAILED DESCRIPTION

[0058] In order to further understand the content of the present invention, the present invention is described in detail with reference to the accompanying drawings and embodiments. It should be understood that the embodiments are merely for explaining the present invention and are not intended to limit the present invention.

[0059] The corresponding meanings of the relevant symbols and abbreviations appearing in the following embodiments and the drawings of the specification are as follows:

[0060] ECU: The abbreviation of Electronic Control Unit, which is also called "on-board computer";

[0061] Map: a spectrum map, i.e. a pre-defined lookup table map;

[0062] DCU: Domain Controller.

[0063]

[0064]

[0065] An independent steer-by-wire control method for a full vector power chassis, such as Figure 1 Shown, including:

[0066] The driver's steering intention is determined based on the road ahead information and the steering wheel angle. The steering intention is then matched with the corresponding driver map curve and combined with the driving parameters to obtain the desired lateral speed and desired yaw rate. The required centripetal force required by the steering intention is compared with the centripetal force that the vehicle can provide under the current driving conditions to select the corresponding Ackermann steering map curve to obtain the optimal Ackermann four-wheel steering angle. Finally, the wheels are controlled to steer based on the optimal Ackermann four-wheel steering angle, desired lateral speed, and desired yaw rate.

[0067] In another embodiment, determining the driver's steering intention includes: judging the road conditions ahead based on road information ahead; if the road ahead is a curve, determining that the driver's steering intention is to turn; if the road ahead is a straight section, further determining that the driver's steering intention is any one of adjusting posture, changing lanes, and turning in place in combination with the steering wheel angle and the vehicle yaw angle.

[0068] Specifically, the road ahead information includes the curvature of the road ahead; when the road ahead is a curve, the curvature of the road ahead is greater than the critical curvature of the road; when the road ahead is a straight section, the curvature of the road ahead is less than or equal to the critical curvature of the road; the critical curvature of the road is set according to the road design specifications.

[0069] The driver map curve is obtained through deep learning, including a driver turning map curve, a driver posture adjustment map curve, a driver lane change map curve, and a driver on-the-spot steering map curve; deep learning refers to inputting a data packet containing a large amount of vehicle speed, road adhesion coefficient, yaw angular velocity, lateral velocity, road curvature, and vehicle yaw angle information for deep learning, and ultimately obtaining an expected curve about yaw angular velocity and lateral velocity.

[0070] The driver's intention is determined to be turning, which is manifested in vehicle motion as: a desire to obtain a larger yaw rate and a smaller lateral speed compared to other steering intentions. At this time, the vehicle steering mode is in a front and rear wheel out-of-phase mode to facilitate turning action and tracking of the curved road. The driving parameters are combined with the driver's turning map curve to obtain the desired lateral speed and desired yaw rate in the turning mode; the driving parameters include the longitudinal speed at the vehicle's center of mass and the road adhesion coefficient.

[0071] Determine the driver's intention to adjust the attitude, which is manifested in the vehicle's movement as a desire to adjust the yaw rate and lateral speed by a small amount. Combine the driving parameters with the driver's attitude adjustment map curve to obtain the desired lateral speed and desired yaw rate in the attitude adjustment mode.

[0072] The driver's intention is determined to be a lane change, which manifests itself in vehicle motion as a desire for a smaller yaw rate and a larger lateral velocity compared to other steering intentions. The vehicle's steering mode is then in a front and rear wheel in-phase mode to facilitate lane change. The desired lateral velocity and yaw rate in the attitude adjustment mode are then combined with the driving parameter driver's attitude map curve.

[0073] Determine the driver's intention to pivot, which manifests itself in the vehicle's movement as the wheels turning to a specified pivot angle. Combine the driving parameter, the driver's pivot map curve, to obtain the desired lateral velocity and yaw rate in pivot mode.

[0074] Unlike traditional front-wheel steering vehicles, the fully vectored power chassis is an overdrive system, allowing for independent four-wheel steering, which allows for separate control of the vehicle's yaw motion around its center of rotation and lateral motion along its side during steering. This is impossible with traditional front-wheel steering vehicles.

[0075] In another embodiment, the forward road information refers to information related to road signs.

[0076] In another embodiment, the further determination based on the steering wheel angle and the vehicle yaw angle includes: when the vehicle yaw angle is greater than the critical course deviation and there is a steering wheel angle, determining that the driver's steering intention is to adjust the posture; when the vehicle yaw angle is less than the critical course deviation and there is a steering wheel angle, determining that the driver's steering intention is to change lanes; when the vehicle speed tends to 0 or is equal to 0 and the steering wheel angle is at a limit angle, determining that the driver's steering intention is to turn on the spot, wherein the yaw angle = lane line angle - vehicle yaw angle.

[0077] In another embodiment, the actual wheel angles of the four wheels of the vehicle are obtained and combined with the corresponding tire cornering stiffness to obtain the actual tire lateral force, which is then combined with the actual tire lateral force, the road adhesion coefficient, the current yaw angular velocity and the lateral velocity to calculate the centripetal force that can be provided.

[0078] In another embodiment, if the required centripetal force is greater than the centripetal force that can be provided, the centripetal force that can be provided needs to be increased, and the optimal Ackerman four-wheel turning angle is determined based on the insufficient Ackerman steering map curve; if the required centripetal force is equal to the centripetal force that can be provided, the centripetal force that can be provided remains unchanged, and the optimal Ackerman four-wheel turning angle is determined based on the full Ackerman steering map curve; if the required centripetal force is less than the centripetal force that can be provided, the centripetal force that can be provided needs to be reduced, and the optimal Ackerman four-wheel turning angle is determined based on the excessive Ackerman steering map curve.

[0079] The insufficient Ackerman steering map curve, the full Ackerman steering map curve and the excessive Ackerman steering map curve are all obtained by deep learning, wherein deep learning refers to inputting a large amount of vehicle speed, road adhesion coefficient, required centripetal force, actual centripetal force, and four-wheel steering angle information for deep learning, and finally obtaining an expected curve about the four-wheel steering angle.

[0080] Specifically, when a traditional car leaves the factory, its steering trapezoidal structure has been determined, so the angle relationship between the left and right wheels has been determined. However, the side slip angle of the wheels varies with different vehicle speeds and road conditions, which may cause insufficient or excessive centripetal force. Therefore, the traditional steering structure cannot always keep the steering force within the required range. Figure 3As shown in the figure, in the Ackerman steering geometry determination process, the required centripetal force is calculated by combining the current vehicle speed and the curvature of the road ahead. The actual wheel angles of the left front wheel, right front wheel, left rear wheel, and right rear wheel are obtained and combined with the corresponding tire cornering stiffness to obtain the actual tire lateral force. The actual tire lateral force, road adhesion coefficient, expected yaw rate, and lateral speed are then combined to calculate the provided centripetal force. The two forces are compared. If F n >F p , it proves that the centripetal force provided is insufficient. At this time, the outer tires need to increase the turning angle to provide greater steering force, and the final four-wheel turning angle is determined based on the insufficient Ackerman steering map curve; if F n =F p , it proves that the centripetal force provided is just right, so in this case the four-wheel turning angle is obtained based on the full Ackerman steering map curve; if F n <F p , it proves that the centripetal force provided is excessive. At this time, the tire needs to reduce the outer tire turning angle to provide smaller steering force, and the final four-wheel turning angle is determined based on the excessive Ackerman steering map curve. The four-wheel turning angle, as the optimal Ackerman four-wheel turning angle, includes the wheel angles of the left front wheel, right front wheel, left rear wheel, and right rear wheel of the full vector power chassis. The insufficient Ackerman steering map curve, the complete Ackerman steering map curve, and the excessive Ackerman steering map curve are all obtained through deep learning training.

[0081] In another embodiment, the process of controlling the vehicle steering module further involves differential values ​​corresponding to the desired lateral velocity and the desired yaw rate, the differential values ​​being obtained according to a tracking differentiator, and the bandwidth frequency of the tracking differentiator being ω n Determines the rate at which the chassis tracks the desired motion, ω n The larger the value, the faster the tracking rate. Figure 2 As shown, the bandwidth frequency ω of the tracking differentiator n The calculation process is as follows:

[0082]

[0083] Where, F represents tire adhesion, F max represents the tire adhesion limit, k is the controller gain, ω n0 For the vehicle speed v x The basic bandwidth frequency under nmax is the maximum bandwidth frequency.

[0084] Specifically, the tracking differentiator adopts a typical second-order system design, and its mathematical expression is:

[0085]

[0086] Calculate the bandwidth frequency ωn After that, the closed-loop transfer function Φ(s) of the tracking differentiator becomes:

[0087]

[0088] Y represents the system response after Laplace transform, U represents the system excitation after Laplace transform, and s is the complex frequency;

[0089] After Laplace inverse transformation, we get:

[0090]

[0091] in, is the second-order differential of the system response y, is the first-order differential of the system response y, let the system response y = x1, x1 is the current state of the system, u = v, v is the target state, that is:

[0092]

[0093] v yd represents the desired lateral velocity, ω d represents the desired yaw rate;

[0094] It can be expressed as the equation of state:

[0095]

[0096] The current state of the system x1 is the transition curve, and x2 is the differential of the transition curve;

[0097] Substituting the above tracking differentiator form into vehicle dynamics control, we get:

[0098] Vehicle lateral direction:

[0099]

[0100] Vehicle yaw direction:

[0101]

[0102] The differential values ​​of the desired yaw rate and the desired lateral velocity are thus obtained, where ω represents the yaw rate.

[0103] In another embodiment, an independent steer-by-wire system for a full vector power chassis is provided. Figure 5As shown, it includes: an input layer, a control layer and an execution layer, wherein the input layer includes driver control input, path tracking input, and sensor observation input; the control layer implements the independent wire-controlled steering control method for a full-vector power chassis mentioned in the above embodiment according to the input of the input layer to determine the corresponding control information and send it to the execution layer, and the execution layer outputs a corresponding control signal to the controller corresponding to each wheel, i.e., the DCU, according to the control information to control the steering angle module of each wheel to realize the steering of the corresponding wheel.

[0104] In another embodiment, the driver control input includes a steering wheel angle, the path tracking input includes front road information and a vehicle yaw angle, and the sensor observation input includes a yaw rate, a lateral velocity, and a vehicle speed.

[0105] In another embodiment, the control layer includes a turning intention determination module, a speed determination module, a turning angle determination module, and an output module.

[0106] The steering intention determination module is used to determine the driver's steering intention based on the front road information and the steering wheel angle;

[0107] The steering intention includes turning, i.e. four-wheel different-direction mode, adjusting posture and changing lanes, i.e. four-wheel same-direction mode, and turning on the spot.

[0108] The speed determination module is used to match the steering intention with the corresponding driver map curve and obtain the desired lateral speed and the desired yaw rate in combination with the driving parameters;

[0109] The turning angle determination module is used to compare the required centripetal force required for the steering intention with the centripetal force that the vehicle can provide under the current driving conditions, select the corresponding Ackermann steering map curve to obtain the optimal Ackermann four-wheel turning angle;

[0110] The output module is used to output the optimal Ackermann four-wheel steering angle, the desired lateral speed and the desired yaw rate as control information.

[0111] In another embodiment, the steering angle module does not include a steering trapezoid.

[0112] Specifically, the steering angle module includes a steering motor 2 and a steering arm 6 that are rotatably connected. The lower end of the steering arm 6 is connected to the wheel 7, and the upper end of the steering arm 6 is connected to a spring roller 1. The steering motor 2 is connected to a connecting piece, and the spring roller 1 is connected to the connecting piece. A limit block 3 is provided on the connecting piece, and the limit block 3 limits the rotation range of the steering arm.

[0113] The steering range of the steering arm 6 is [-90°, 90°].

[0114] The spring roller 1 includes a spring, a conical disk, and a roller structure that are fixedly connected. The spring is fixedly connected to the steering arm 6, and the conical disk and the roller structure are connected to a connecting piece.

[0115] like Figure 6 As shown, the connecting part is a flange, which is connected to the vehicle body through the flange 4, and the flange 4 is connected to the steering motor 2. The steering motor 2 is connected to the steering arm 6 through the gear sleeve 5. The steering arm 6 is connected to the wheel 7. The rotation energy of the steering motor 2 is transmitted through the gear sleeve 5 to drive the rotation of the steering arm 6, and the steering arm 6 controls the lateral swing of the wheel 7. The steering arm 6 is connected to a spring roller 1, and the spring roller 1 is connected to the flange 4. The flange 4 is provided with two limit blocks 3. The limit blocks 3 are used to limit the angular range of the steering arm 6. The maximum angular range of the steering arm 6 is ±90°. The spring roller 1 includes a spring, a conical disc and a roller structure. The spring is fixedly connected to the steering arm 6, and the conical disc and the roller structure are pressed into the groove on the flange 4. The steering motor 2 is equipped with an angle sensor 8. The steering motor 2 is a rotary motor. The rotary motor can be arranged on the suspension to effectively reduce the requirements for the motor's shock absorption and isolation performance. Because large lateral forces are easily generated during steering, in order to balance the lateral forces, a spring roller 1 structure connected to the steering arm 6 is designed.

[0116] The steering arm 6 is connected to the flange 4 through the bearing. The outer ring of the bearing is fixed on the flange 4, and the inner ring is fixed on the steering arm 6. The guide rod at the lower end of the conical disc cooperates with the guide barrel on the steering arm 6 to play a guiding role. There is a spring between the lower surface of the conical disc and the steering arm 6 to adjust the gap in real time, so that the spring roller structure is pressed against the groove of the conical cross section of the flange 4.

[0117] When the four-wheel independent steering angle module is applied to all four wheels of a vehicle, there is no direct connection between the modules, achieving maximum decoupling, extremely high controllable freedom, and strong trajectory tracking capabilities. The wheels can steer 90 degrees, enabling full-range displacement. This facilitates the implementation of control algorithms. At low speeds, the four-wheel counter-steering mode can be switched to achieve lower lateral speeds and higher yaw rates, thereby improving path tracking accuracy. At high speeds, the four-wheel unidirectional steering mode can be switched to effectively increase the turning radius, reduce the vehicle's yaw moment and yaw rate, and enhance handling stability and active safety.

[0118] The independent wire-controlled steering system designed by the present invention for a full vector power chassis can realize multiple steering modes, such as Figure 4As shown, it includes: (a) is the traditional front-wheel steering mode, and similarly, the traditional rear-wheel steering mode and the traditional four-wheel steering mode can also be completed. When an obstacle appears in front of the vehicle during driving, the oblique straight-line walking mode in (b) can be used. This walking method enables the vehicle to change lanes faster during driving. When the vehicle needs to turn around or turn in a small space, the in-situ turning mode in (c) can be used. The turning radius of this mode is approximately equal to half the length of the vehicle body (the minimum achievable turning radius). This mode can easily cope with the U-turn and turning needs in a small space. When the vehicle needs to park sideways, the lateral driving mode in (d) can be used. Multiple driving modes will provide great convenience for driving.

[0119] The above is a schematic description of the present invention and its embodiments, which is not restrictive. The drawings show only one embodiment of the present invention, and the actual structure is not limited thereto. Therefore, if a person skilled in the art is inspired by this and, without departing from the purpose of the present invention, designs a structure and embodiment similar to this technical solution without inventiveness, they shall fall within the scope of protection of the present invention.

Claims

1. An independent steer-by-wire control method for a full vector power chassis, characterized in that: include: The driver's steering intention is determined based on the road ahead and the steering wheel angle. The steering intention is then matched with the corresponding driver map curve and combined with driving parameters to obtain the desired lateral speed and desired yaw rate. The required centripetal force required by the steering intention is compared with the centripetal force that the vehicle can provide under the current driving conditions. The corresponding Ackermann steering map curve is selected to obtain the optimal Ackermann four-wheel steering angle. Finally, the wheels are controlled to steer based on the optimal Ackermann four-wheel steering angle, the desired lateral speed, and the desired yaw rate. If the required centripetal force is greater than the available centripetal force, the available centripetal force needs to be increased, and the optimal Ackermann four-wheel steering angle is determined based on the insufficient Ackermann steering map curve; If the required centripetal force is equal to the available centripetal force, the available centripetal force remains unchanged, and the optimal Ackermann four-wheel steering angle is determined based on the full Ackermann steering map curve; If the required centripetal force is less than the available centripetal force, the available centripetal force needs to be reduced, and the optimal Ackermann four-wheel steering angle is determined based on the excessive Ackermann steering map curve; Determine the driver's intention to adjust the attitude, which is manifested in the vehicle's movement as a desire to adjust the yaw rate and lateral speed by a small amount. Combine the driving parameters with the driver's attitude adjustment map curve to obtain the desired lateral speed and desired yaw rate in the attitude adjustment mode. The driver's intention is determined to be a lane change, which manifests itself in vehicle motion as a desire for a smaller yaw rate and a larger lateral velocity compared to other steering intentions. The vehicle's steering mode is then in a front and rear wheel in-phase mode to facilitate lane change. The desired lateral velocity and yaw rate in the attitude adjustment mode are then combined with the driving parameter driver's attitude map curve. Determining that the driver's intention is to turn in place, which is manifested in the vehicle's movement as the wheels needing to turn to a specified turning angle; The driving parameter driver's spot steering map curve is combined to obtain the expected lateral speed and expected yaw rate in the spot steering mode.

2. The independent steer-by-wire control method for a full vector power chassis according to claim 1, characterized in that: The determining of the driver's steering intention includes: judging the road condition ahead based on the road information ahead, if the road ahead is a curve, determining that the driver's steering intention is to turn, and if the road ahead is a straight section, further determining that the driver's steering intention is any one of adjusting posture, changing lanes and turning on the spot based on the steering wheel angle and the vehicle yaw angle.

3. The independent steer-by-wire control method for a full vector power chassis according to claim 2, characterized in that: Further judgment based on the steering wheel angle and the vehicle yaw angle includes: when the vehicle yaw angle is greater than the critical course deviation and there is a steering wheel angle, the driver's steering intention is judged to be adjusting the posture; when the vehicle yaw angle is less than the critical course deviation and there is a steering wheel angle, the driver's steering intention is judged to be changing lanes; when the vehicle speed tends to 0 or is equal to 0 and the steering wheel angle is at the extreme turning angle, the driver's steering intention is judged to be turning on the spot, where the yaw angle = lane line angle - vehicle yaw angle.

4. The independent steer-by-wire control method for a full vector power chassis according to claim 1, characterized in that: The actual wheel angles of the four wheels of the vehicle are obtained and combined with the corresponding tire cornering stiffness to obtain the actual tire lateral force. The actual tire lateral force, road adhesion coefficient, current yaw rate and lateral speed are then combined to calculate the centripetal force that can be provided.

5. The independent steer-by-wire control method for a full vector power chassis according to claim 1, characterized in that: The process of controlling the vehicle steering module also involves the differential value corresponding to the desired lateral velocity and the desired yaw rate, which is obtained according to the tracking differentiator. The bandwidth frequency of the tracking differentiator is The calculation process is as follows: ； Where, Indicates tire adhesion. Indicates the tire adhesion limit value, is the controller gain, For vehicle speed The basic bandwidth frequency under is the maximum bandwidth frequency.

6. An independent steer-by-wire system for a full vector power chassis, characterized in that: include: An input layer, a control layer, and an execution layer, wherein the input layer includes driver control input, path tracking input, and sensor observation input; The control layer implements the independent wire-controlled steering control method for a full-vector power chassis according to any one of claims 1-5 based on the input of the input layer to determine the corresponding control information and send it to the execution layer. The execution layer outputs a corresponding control signal to the controller corresponding to each wheel based on the control information to control the steering angle module of each wheel to realize the steering of the corresponding wheel.

7. The independent steer-by-wire system for a full vector power chassis according to claim 6, characterized in that: The driver control input includes a steering wheel angle, the path tracking input includes front road information and a vehicle yaw angle, and the sensor observation input includes a yaw rate, a lateral velocity, and a vehicle speed.

8. The independent steer-by-wire system for a full vector power chassis according to claim 6, characterized in that: The control layer includes a steering intention determination module, a speed determination module, a turning angle determination module and an output module. The steering intention determination module is used to determine the driver's steering intention based on the front road information and the steering wheel angle; The speed determination module is used to match the steering intention with the corresponding driver map curve and obtain the desired lateral speed and the desired yaw rate in combination with the driving parameters; The turning angle determination module is used to compare the required centripetal force required for the steering intention with the centripetal force that the vehicle can provide under the current driving conditions, select the corresponding Ackermann steering map curve to obtain the optimal Ackermann four-wheel turning angle; The output module is used to output the optimal Ackermann four-wheel steering angle, the desired lateral speed and the desired yaw rate as control information.

9. The independent steer-by-wire system for a full vector power chassis according to claim 6, characterized in that: The steering angle module does not include a steering trapezoid.

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