Independent steer-by-wire system for full-vector power chassis and control method

Abstract

The invention relates to the technical field of vehicle integrated design and control, and provides an independent steer-by-wire system for a full-vector power chassis and a control method of the independent steer-by-wire system for the full-vector power chassis. Then the steering intention is matched with a corresponding driver map curve, the expected transverse speed and the expected yaw velocity are obtained in combination with the driving parameters, the demanded centripetal force needed by the steering intention is compared with the centripetal force capable of being provided by the vehicle under the current driving condition, and a corresponding Ackerman steering map curve is selected to obtain the optimal Ackerman four-wheel steering angle; and finally, controlling a steering angle module of the vehicle to steer according to the optimal Ackerman four-wheel steering angle, the expected transverse speed and the expected yaw velocity. According to the invention, steering control can be well carried out.

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 sharp 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 a variety of vehicle usage scenarios (such as turning on the spot, changing lanes sideways, and four-wheel independent steering) came 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. In addition, 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 gears. 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 maneuverability of the vehicle. 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 power chassis vehicles has undoubtedly solved this problem. Full-vector power chassis vehicles are also one of the important types of new energy vehicles because their drive form is distributed drive, that is, electric drive. Full-vector power chassis vehicles are an innovation in automobile chassis. The full-vector power chassis is equipped with an angle module at each wheel. The angle module integrates the suspension and steering system as one, cancels the traditional mechanical components such as the steering trapezoid, and cancels the mechanical connection between the left and right wheels, thereby realizing the physical decoupling of the left and right wheels. This makes the wheel angle completely controlled by the steering motor, and there is no rigid relationship constraint between the wheel angles, which greatly solves the fundamental problem of understeer and oversteer. However, without the constraints of traditional mechanical components such as the steering trapezoid, although the maneuverability of the car is improved to a certain extent, its handling stability and structural safety are also facing severe challenges. Therefore, it is particularly important to design a full-vector power chassis steering angle module with high structural safety and a full-wheel independent wire-controlled steering control method that fits the full-vector power chassis and is generally applicable. Summary of the invention

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

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

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

[0007] Furthermore, determining 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, 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 in combination with the steering wheel angle and the vehicle yaw angle.

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

[0009] The driver's intention is to turn, which is manifested in the vehicle movement as follows: it is expected to obtain a larger yaw rate and a smaller lateral speed than 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 curved roads; the driving parameters are combined with the driver's turning map curve to obtain the expected lateral speed and the expected yaw rate in the turning mode; the driving parameters include the longitudinal speed at the center of mass of the vehicle and the road adhesion coefficient.

[0010] Determine the driver's intention to adjust the posture, which is manifested in the vehicle movement as: expecting to adjust the yaw rate and lateral speed by a small amplitude; combine the driving parameters with the driver's posture adjustment map curve to obtain the expected lateral speed and expected yaw rate in the posture adjustment mode;

[0011] The driver's intention is to change lanes, which is reflected in the vehicle movement as follows: the vehicle expects to obtain a smaller yaw rate and a larger lateral speed than other steering intentions. At this time, the vehicle steering mode is in the front and rear wheel in-phase mode to facilitate the lane change action; the driving parameter driver's posture adjustment map curve is combined to obtain the expected lateral speed and expected yaw rate in the posture adjustment mode;

[0012] Determine that the driver's intention is to turn on the spot, which is manifested in the vehicle movement as the wheels need to turn to a specified on-the-spot turning angle; combine the driving parameter driver's on-the-spot turning map curve to obtain the expected lateral speed and expected yaw rate in the on-the-spot turning 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 route 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 route 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 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 turning 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, and 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 centripetal force that can be provided, it is necessary to increase the centripetal force that can be provided, and determine the optimal Ackerman four-wheel turning angle 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 determine the optimal Ackerman four-wheel turning angle based on the full Ackerman steering map curve; if the required centripetal force is less than the centripetal force that can be provided, it is necessary to reduce the centripetal force that can be provided, and determine the optimal Ackerman four-wheel turning angle 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, the differential values ​​being obtained according to a tracking differentiator, and the bandwidth frequency ω of the tracking differentiator 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 transformation, U represents the system excitation after Laplace transformation, 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 state equation:

[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, and ω represents the yaw rate.

[0038] An independent wire-controlled steering system for a full vector power chassis comprises: an input layer, a control layer and an execution layer, wherein the input layer comprises a driver control input, a path tracking input and a sensor observation input; the control layer implements an independent wire-controlled steering control method for a full vector power chassis according to the input of the input layer to determine corresponding control information and send it to the execution layer, and the execution layer outputs a corresponding control signal for a corresponding controller of each wheel according to the control information to control a steering angle module of each wheel to realize the 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 angular velocity, a lateral velocity and a vehicle speed.

[0040] Furthermore, the control layer includes a turning 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 by the steering intention with the centripetal force that the vehicle can provide under the current driving condition, select the corresponding Ackerman steering map curve to obtain the optimal Ackerman 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] Further, 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 cancels the connection of mechanical components such as the steering trapezoid, realizes structural decoupling, has a higher controllable degree of freedom, can better play the advantages of the control strategy, and thus realize 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 limit turning angle reach ±90°, can realize special driving modes such as lateral driving, and at the same time, a limit block is arranged at the limit turning angle to ensure steering safety; different from the traditional four-wheel steering, which only needs two motors to drive the steering gear of the front and rear axles to complete the four-wheel steering, the four-wheel independent steering angle module has four wheels that are completely decoupled in structure, so it is necessary to arrange four steering motors with the same number of wheels to drive the steering of each wheel respectively, so that 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) Combined with various driver curve maps that have been learned through deep learning, under the same computing power conditions, the driver curve map obtained through deep learning can have higher generalization, and its steady-state accuracy is also better while ensuring stability. The introduction of control quantities such as lateral speed and yaw rate can improve the handling stability of the car; at the same time, only a simple second-order tracking differentiator is needed to obtain the required control quantity, which reduces the complexity of the control system and enables the control system to achieve the control target without overshoot; the present invention designs a bandwidth calculation method that can speed up the system response speed.

[0049] 3) Combined with various Ackerman steering curve maps through deep learning, the Ackerman steering curve map obtained through deep learning with tens of millions of real vehicle test data can have higher generalization, and its steady-state accuracy is also better while ensuring stability. Compared with other theoretical control methods, its effect on real vehicles is also better. At the same time, considering the relationship between the required centripetal force and the actual centripetal force provided during steering, a series of problems such as understeering and oversteering caused by the side slip angle of the wheel can be eliminated. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 It is a flow chart of an independent wire-controlled steering control method for a full vector power chassis in an embodiment.

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

[0052] Figure 3 1 is a geometric diagram of Ackerman steering in an embodiment.

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

[0054] Figure 5 A control architecture diagram of an independent wire-controlled steering system for a full-vector power chassis according to an embodiment.

[0055] Figure 6 It is a schematic structural diagram 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- Steering angle sensor. DETAILED DESCRIPTION

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

[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 wire-controlled steering control method for a full vector power chassis, such as Figure 1 As shown, including:

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

[0067] In another embodiment, determining 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 the driver's steering intention is to turn, and if the road ahead is a straight section, combining the steering wheel angle and the vehicle yaw angle to further determine the driver's steering intention is any one of adjusting posture, changing lanes and turning on the spot.

[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 changing map curve, and a driver on-the-spot steering map curve; wherein deep learning refers to inputting a data packet containing a large amount of vehicle speed, road adhesion coefficient, yaw angular velocity, lateral speed, road curvature, and vehicle yaw angle information for deep learning, and finally obtaining an expected curve about yaw angular velocity and lateral speed.

[0070] The driver's intention is to turn, which is manifested in the vehicle movement as follows: it is expected to obtain a larger yaw rate and a smaller lateral speed than 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 curved roads; the driving parameters are combined with the driver's turning map curve to obtain the expected lateral speed and the expected yaw rate in the turning mode; the driving parameters include the longitudinal speed at the center of mass of the vehicle and the road adhesion coefficient.

[0071] Determine the driver's intention to adjust the posture, which is manifested in the vehicle movement as: expecting to adjust the yaw rate and lateral speed by a small amplitude; combine the driving parameters with the driver's posture adjustment map curve to obtain the expected lateral speed and expected yaw rate in the posture adjustment mode;

[0072] The driver's intention is to change lanes, which is reflected in the vehicle movement as follows: the vehicle expects to obtain a smaller yaw rate and a larger lateral speed than other steering intentions. At this time, the vehicle steering mode is in the front and rear wheel in-phase mode to facilitate the lane change action; the driving parameter driver's posture adjustment map curve is combined to obtain the expected lateral speed and expected yaw rate in the posture adjustment mode;

[0073] Determine that the driver's intention is to turn on the spot, which is manifested in the vehicle movement as the wheels need to turn to a specified on-the-spot turning angle; combine the driving parameter driver's on-the-spot turning map curve to obtain the expected lateral speed and expected yaw rate in the on-the-spot turning mode;

[0074] Unlike traditional front-wheel steering vehicles, the full vector power chassis is an overdrive system, and its four-wheel independent steering function allows the vehicle's yaw motion around the center of rotation and lateral motion along the side of the vehicle to be controlled separately during the steering process, which is impossible for traditional front-wheel steering vehicles.

[0075] In another embodiment, the road ahead 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 route 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 route 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 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 turning 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, and 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 angles of the wheels are different at different vehicle speeds and road conditions, so there will be problems of insufficient or excessive centripetal force. Therefore, the traditional steering structure cannot always keep the steering force within the required range. Figure 3As shown in FIG. 1 , in the process of determining the Ackerman steering geometry, the required centripetal force is calculated by combining the current vehicle speed and the curvature of the road ahead, and the actual wheel angles of the left front wheel, the right front wheel, the left rear wheel, and the right rear wheel are obtained by combining the corresponding tire cornering stiffness to obtain the actual tire lateral force. The actual tire lateral force, the road adhesion coefficient, the expected yaw angular velocity, and the lateral velocity 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 tire needs 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 determine the final four-wheel turning angle based on the excessive Ackerman steering map curve. The 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 as the optimal Ackerman four-wheel turning angle. 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, wherein the differential values ​​are obtained according to a tracking differentiator, and the bandwidth frequency ω of the tracking differentiator is 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 transformation, U represents the system excitation after Laplace transformation, 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 state equation:

[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, and ω represents the yaw rate.

[0103] In another embodiment, an independent wire-controlled steering system for a full vector power chassis is provided, such as 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 an 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 for each wheel corresponding controller, i.e., 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 intentions include 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 by the steering intention with the centripetal force that the vehicle can provide under the current driving condition, select the corresponding Ackerman steering map curve to obtain the optimal Ackerman 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 a 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 comprises a spring, a conical disk and a roller structure which 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 piece 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, and 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 the spring roller 1, and the spring roller 1 is connected to the flange 4. The flange 4 is provided with two limit blocks 3, and 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 in 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-absorbing and isolation performance; because a large lateral force is easily generated during steering, in order to balance the lateral force, 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 disk cooperates with the guide barrel on the steering arm 6 to play a guiding role. There is a spring between the lower side of the conical disk 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 section of the flange 4.

[0117] When the four-wheel independent steering angle module is applied to the four wheels of the vehicle, there is no direct connection between each four-wheel independent steering angle module, which realizes the maximum decoupling, has a very high controllable degree of freedom, and has a strong trajectory tracking ability; the wheel turns positive and negative 90 degrees, which can realize the full-range displacement function; it is conducive to the use of the control algorithm, and the four-wheel opposite-direction steering mode can be switched at low speed, which can obtain a smaller lateral speed and a larger yaw rate, which is convenient for improving the path tracking accuracy. Switching the four-wheel same-direction steering mode at high speed can effectively increase the turning radius, reduce the yaw moment and yaw rate of the vehicle, and improve the 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 on-the-spot turning mode in (c) can be used. The turning radius of this mode is approximately equal to half of the length of the vehicle body (the minimum achievable turning radius). This mode can easily cope with the needs of turning around and turning 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 present invention and its embodiments are described schematically above, and the description 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 it and designs a structural method and an embodiment similar to the technical solution without creativity without departing from the purpose of the invention, they shall all fall within the protection scope of the present invention.

Claims

1. An independent wire-controlled steering control method for a full vector power chassis, characterized in that: include: The driver's steering intention is determined based on the road information ahead and the steering wheel angle, and then the steering intention is matched with the corresponding driver map curve and combined with the driving parameters to obtain the expected lateral speed and the expected yaw rate. The required centripetal force required by the steering intention and the centripetal force that the vehicle can provide under the current driving conditions are compared to select the corresponding Ackerman steering map curve to obtain the optimal Ackerman four-wheel steering angle. Finally, the wheels are controlled to steer according to the optimal Ackerman four-wheel steering angle, the expected lateral speed and the expected yaw rate.

2. The independent wire-controlled steering 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 according to 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 in combination with the steering wheel angle and the vehicle yaw angle.

3. The independent wire-controlled steering control method for a full vector power chassis according to claim 2, characterized in that: 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 route 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 route 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 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.

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

5. The independent wire-controlled steering control method for a full vector power chassis according to claim 1, characterized in that: 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 steering 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 steering 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 steering angle is determined based on the excessive Ackerman steering map curve.

6. The independent wire-controlled steering 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 differential values ​​corresponding to the desired lateral velocity and the desired yaw rate, the differential values ​​are obtained according to a tracking differentiator, and the bandwidth frequency ω of the tracking differentiator is n The calculation process is as follows: 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.

7. An independent wire-controlled steering 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 a driver control input, a path tracking input and a sensor observation input; The control layer implements the independent wire-controlled steering control method for a full vector power chassis as described in any one of claims 1-6 according to the input of the input layer to determine the corresponding control information and send it to the execution layer. The execution layer outputs the corresponding control signal to the controller corresponding to each wheel according to the control information to control the steering angle module of each wheel to realize the steering of the corresponding wheel.

8. The independent wire-controlled steering system for a full vector power chassis according to claim 7, 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 angular velocity, a lateral velocity, and a vehicle speed.

9. The independent wire-controlled steering system for a full vector power chassis according to claim 7, characterized in that: The control layer includes a turning 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 by the steering intention with the centripetal force that the vehicle can provide under the current driving condition, select the corresponding Ackerman steering map curve to obtain the optimal Ackerman 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.

10. The independent wire-controlled steering system for a full vector power chassis according to claim 7, characterized in that: The steering angle module does not include a steering trapezoid.

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