Multi-mode steering control method and device for multi-axle all-wheel steering vehicle

Abstract

The invention provides a multi-mode steering control method and device for a multi-axle all-wheel steering vehicle, provides a multi-mode steering control scheme for the multi-axle all-wheel steering vehicle, and can effectively improve the steering performance of the multi-axle vehicle through chassis electric control full wheel steering angle control. The problems that a multi-axle vehicle is low in steering flexibility, large in steering tire abrasion, high in steering working condition requirement and the like are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of special vehicles, and in particular to a multi-mode steering control method and device for a multi-axle all-wheel steering vehicle. Background Art

[0002] Multi-axle all-wheel steering (AWS) vehicles have complex and diverse application scenarios. Long wheelbases place high demands on vehicle maneuverability and stability. Multi-mode steering control is key to improving vehicle handling performance and is crucial for enhancing road transport efficiency and driving safety. However, existing steering control solutions for multi-axle all-wheel steering vehicles lack flexibility and stability. Summary of the Invention

[0003] The present invention aims to provide a multi-mode steering control method and device for a multi-axle all-wheel steering vehicle that overcomes the above-mentioned problems or at least partially solves the above-mentioned problems.

[0004] To achieve the above object, the technical solution of the present invention is specifically implemented as follows:

[0005] One aspect of the present invention provides a multi-mode steering control method for a multi-axle all-wheel steering vehicle, comprising:

[0006] Get the steering mode request;

[0007] Enter the corresponding steering mode according to the current motion state and fault state;

[0008] When there is no fault, a steering control request is obtained and a target steering mode is entered for steering control; wherein the steering control request includes a stationary steering control request, a diagonal steering control request, and a normal steering control request, and the target steering modes include a stationary steering mode, a diagonal steering mode, and a normal steering mode;

[0009] When a fault occurs, a steering control request is obtained, the system enters the fault steering mode for steering control, and locks the corresponding steering shaft according to the steering system fault status.

[0010] Optionally, the method further comprises:

[0011] Establish a linear two-degree-of-freedom model for an n-axis steering vehicle;

[0012] According to the linear two-degree-of-freedom model of the n-axis steering vehicle, the unified steady-state yaw angular velocity gain expression, the steady-state center of mass sideslip angle gain expression, the equivalent wheelbase expression of the n-axis steering vehicle, the equivalent stability coefficient expression of the n-axis steering vehicle, the equivalent steering center distance expression of the n-axis steering vehicle and the equivalent center of mass sideslip angle coefficient expression of the n-axis steering vehicle are obtained.

[0013] Optionally, when the steering control request is an in-place steering control request, entering the target steering mode to perform steering control includes:

[0014] Control the vehicle according to the wheel angle of each axle

[0015]

[0016] Perform a pivot turn;

[0017] Among them, X Gi is the distance from each axis to the vehicle's geometric center, B w is the wheelbase, and ± means that the turning angles of coaxial wheels are equal in size but opposite in direction.

[0018] Optionally, when the steering control request is an oblique steering control request, entering the target steering mode to perform steering control includes:

[0019] Control the vehicle according to the relationship between the wheel angles of each axle:

[0020]

[0021] Perform oblique turns;

[0022] Among them, δ1 is the wheel angle of the first axis, ε i1 is the rotation angle ratio of the i-th axis to the 1st axis,

[0023] Optionally, when the steering control request is a normal steering control request, entering the target steering mode according to the steering control request includes:

[0024] A yaw-skew equivalent steering model for a multi-axle vehicle is used, and a hierarchical control method is employed to achieve wheel angle distribution for conventional steering.

[0025] Optionally, the method of using a multi-axle vehicle yaw-slope equivalent steering model and adopting a hierarchical control method to implement wheel angle distribution for conventional steering includes:

[0026] According to the linear two-degree-of-freedom model of the n-axis steering vehicle, the unified steady-state yaw rate gain characteristic G of the n-axis vehicle is obtained. ω and the steady-state center of mass sideslip angle gain G β ;

[0027] The yaw-side equivalent steering model of a multi-axle vehicle is used to calculate the Ackerman equivalent steering center distance Δ of the yaw characteristic. nω and the Ackerman equivalent turning center distance Δ of the center of mass side slip characteristic nβ ;

[0028] According to the equivalent bias weight coefficient w, calculate the yaw-side equivalent turning center distance Δ nvalue, where Δ n =wΔ nr +(1-w)Δ nβ ;

[0029] Calculate the steering angle of each axis;

[0030] Conventional steering is completed by performing corner allocation according to the preset corner allocation control strategy.

[0031] Optionally, calculating the steering angle of each axis includes:

[0032] The steering angle of each axis under the Ackerman equivalent steering model is calculated by the following formula:

[0033]

[0034] Among them, X i is the displacement from the i-th axis to the center of mass of the vehicle.

[0035] Optionally, the preset turning angle allocation control strategy includes:

[0036] Control the slip angles from the second axis to the nth axis to be equal.

[0037] Optionally, locking the corresponding steering shaft according to the steering system fault state includes:

[0038] In redundant mode, the steering shaft close to the steering center is locked;

[0039] In the fault mode, the steering shafts other than the first and second steering shafts are locked.

[0040] Another aspect of the present invention provides a multi-mode steering control device for a multi-axle all-wheel steering vehicle, comprising: a processor, a memory;

[0041] The memory is used to store computer programs;

[0042] The processor is configured to execute the multi-mode steering control method for the multi-axle all-wheel steering vehicle as described above by calling the computer program.

[0043] It can be seen that the multi-mode steering control method and device for a multi-axle all-wheel steering vehicle provided by the present invention propose a multi-mode steering control scheme for a multi-axle all-wheel steering vehicle. Through the electronic all-wheel angle control of the chassis, the steering performance of the multi-axle vehicle can be effectively improved, and the problems of low steering flexibility of the multi-axle vehicle, large wear of the steering tires, and high steering working conditions requirements can be solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0045] Figure 1 A flowchart of a multi-mode steering control method for a multi-axle all-wheel steering vehicle provided by an embodiment of the present invention;

[0046] Figure 2 A multi-mode steering workflow diagram provided by an embodiment of the present invention;

[0047] Figure 3 A schematic diagram of a linear two-degree-of-freedom model provided by an embodiment of the present invention;

[0048] Figure 4 A schematic diagram of the distribution relationship of the wheel angles in the on-the-spot steering mode provided by an embodiment of the present invention;

[0049] Figure 5 A schematic diagram of the distribution relationship of the rotation angles of each wheel in the oblique driving mode provided by an embodiment of the present invention;

[0050] Figure 6 A schematic diagram of the basic workflow of the conventional steering mode provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0051] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0052] Figure 1 A flowchart of a multi-mode steering control method for a multi-axle all-wheel steering vehicle provided by an embodiment of the present invention is shown. Figure 2 The multi-mode steering workflow diagram provided by the embodiment of the present invention is shown in FIG. Figure 1 and Figure 2 The multi-mode steering control method for a multi-axle all-wheel steering vehicle provided by an embodiment of the present invention includes:

[0053] S1, obtain steering mode request;

[0054] S2, enter the corresponding steering mode according to the current motion state and fault state.

[0055] Specifically, the present invention firstly inputs a steering mode request via the driver, and the vehicle determines which steering mode to enter according to the current motion state and fault state.

[0056] S3, when there is no fault, obtain a steering control request and enter a target steering mode for steering control; wherein, the steering control request includes a stationary steering control request, a diagonal steering control request and a normal steering control request, and the target steering mode includes: a stationary steering mode, a diagonal steering mode and a normal steering mode.

[0057] Specifically, when there are no faults, the vehicle responds to the driver's steering control request and enters the target steering mode, which mainly includes: entering the stationary steering mode when stationary; entering the diagonal steering mode when stationary; and entering the default normal steering mode when in motion.

[0058] S4, when there is a fault, obtain a steering control request, enter a fault steering mode to perform steering control, and lock the corresponding steering shaft according to the steering system fault state.

[0059] Specifically, when a steering system malfunctions, the vehicle enters a fail-steering mode based on the driver's steering control request. In this mode, the vehicle can lock part of the steering shaft based on the steering system malfunction status.

[0060] As an optional implementation of the embodiment of the present invention, the multi-mode steering control method for a multi-axle all-wheel steering vehicle provided in the embodiment of the present invention further includes:

[0061] Establish a linear two-degree-of-freedom model for an n-axis steering vehicle;

[0062] According to the linear two-degree-of-freedom model of the n-axis steering vehicle, the unified steady-state yaw angular velocity gain expression, the steady-state center of mass sideslip angle gain expression, the equivalent wheelbase expression of the n-axis steering vehicle, the equivalent stability coefficient expression of the n-axis steering vehicle, the equivalent steering center distance expression of the n-axis steering vehicle and the equivalent center of mass sideslip angle coefficient expression of the n-axis steering vehicle are obtained.

[0063] In specific implementation, the present invention first performs a multi-axle vehicle dynamics modeling: the present invention establishes a linear two-degree-of-freedom model of an n-axle steering vehicle as follows Figure 3 The present invention is described below using a 6-axle vehicle as an example, but is also applicable to an n-axle vehicle. When n=6, it is a 6-axle vehicle.

[0064] Figure 3 In the figure, the origin of the vehicle coordinate system is fixed at the center of mass of the vehicle O; the X-axis of the coordinate system is along the longitudinal axis of the vehicle; the Y-axis points to the left side of the vehicle, and the Z-axis is perpendicular to the XOY plane and points upward; the vehicle steering center is OR; the instantaneous steering center is O'R; the displacement of each axle to the center of mass is X i(i=1, 2, 3, 4, 5, 6), define the i-th axis as positive before the center of mass and negative after the center of mass; the horizontal displacement of the steering center OR to the center of mass is Δ; the horizontal displacement of the instantaneous steering center O'R to the center of mass is Δ'; the wheel angle and tire side slip angle of each axis are δ i and α i The vehicle's yaw rate ω is in the same direction as the Z axis; the vehicle's sideslip angle is β;

[0065] According to the derivation of the two-degree-of-freedom linear vehicle model, the uniform steady-state yaw rate gain expression of the n-axis vehicle can be obtained as follows:

[0066]

[0067] The expression of steady-state center of mass sideslip angle gain is:

[0068]

[0069] G ω is the vehicle steady-state yaw rate gain; G β Steady-state center of mass sideslip angle gain; l n is the equivalent wheelbase of the n-axle steering vehicle; and K n is the equivalent stability coefficient of the n-axis steering vehicle; when the vehicle is understeering, K n >0, when the vehicle is in neutral steering, K n =0, when the vehicle is oversteering, K n <0; G β is the vehicle's steady-state center of mass sideslip angle gain, l n ′ is the equivalent turning center distance of the n-axis steering vehicle, and K is defined n ′ is the equivalent center of mass sideslip angle coefficient of the n-axis steering vehicle; the above variable expressions are

[0070]

[0071]

[0072] Where, E i is the roll steering coefficient of the i-th axis; K i is the cornering stiffness of the tire on the i-th axle; m i is the unsprung mass of the i-th axle; m b is the vehicle body mass; μ b is the steady-state roll and yaw coefficient; ε i1 is the rotation angle ratio of the i-th axis to the 1st axis, and this proportional coefficient is defined as

[0073]

[0074] As an optional implementation manner of the embodiment of the present invention, when the steering control request is an in-place steering control request, entering the target steering mode to perform steering control includes:

[0075] Control the vehicle according to the wheel angle of each axle

[0076]

[0077] Perform a pivot turn;

[0078] Among them, X Gi is the distance from each axis to the vehicle's geometric center, B w is the wheelbase, and ± means that the turning angles of coaxial wheels are equal in size but opposite in direction.

[0079] In specific implementation, the in-situ steering mode of the present invention is realized as follows:

[0080] The stationary steering mode is suitable for vehicles with a minimum turning radius and can be turned in a small space. In this steering mode, the electronic steering system controls the front three axles on one side of the vehicle to steer in the same direction, while the wheels on the fourth, fifth, and sixth axles rotate in the opposite direction of the front three axles. All axles are guaranteed to meet the Ackermann angle relationship to achieve pure rolling of the tires as much as possible and reduce tire wear. The schematic diagram is shown below. Figure 4 shown.

[0081] When the driver inputs a pivot control request, the vehicle pivots around the geometric center OG. The distance from each axis to the vehicle's geometric center OG is X. Gi . B w is the wheelbase; then the wheel angle of each axle is

[0082]

[0083] ± means that the turning angles of coaxial wheels are equal in magnitude but opposite in direction.

[0084] As an optional implementation manner of the embodiment of the present invention, when the steering control request is an oblique steering control request, entering the target steering mode to perform steering control includes:

[0085] Control the vehicle according to the relationship between the wheel angles of each axle:

[0086]

[0087] Perform oblique turns;

[0088] Among them, δ1 is the wheel angle of the first axis, ε i1 is the rotation angle ratio of the i-th axis to the 1st axis,

[0089] In specific implementation, the oblique steering mode of the present invention is realized as follows:

[0090] The oblique steering mode is suitable for situations where the vehicle is stationary or moving at low speed, and the lateral space is small, making it inconvenient to turn but requiring lateral movement. The rotation direction and magnitude of the rear five axes are exactly the same as the direction and magnitude of the first axis to complete oblique linear movement, such as Figure 5 shown.

[0091] When the steering wheel input is a small angle, the first axle wheel angle δ1 is obtained. At this time, the wheel angles of the n axles after control are exactly the same as those of the first axle. The relationship between the wheel angles of each axle is as follows:

[0092]

[0093] As an optional implementation manner provided by an embodiment of the present invention, when the steering control request is a normal steering control request, entering the target steering mode according to the steering control request includes:

[0094] A yaw-skew equivalent steering model for a multi-axle vehicle is used, and a hierarchical control method is employed to achieve wheel angle distribution for conventional steering.

[0095] Wherein: using a multi-axle vehicle yaw-slope equivalent steering model and adopting a hierarchical control method to achieve wheel angle distribution for conventional steering includes:

[0096] According to the linear two-degree-of-freedom model of the n-axis steering vehicle, the unified steady-state yaw rate gain characteristic G of the n-axis vehicle is obtained. ω and the steady-state center of mass sideslip angle gain G β ;

[0097] The yaw-side equivalent steering model of a multi-axle vehicle is used to calculate the Ackerman equivalent steering center distance Δ of the yaw characteristic. nω and the Ackerman equivalent turning center distance Δ of the center of mass side slip characteristic nβ ;

[0098] According to the equivalent bias weight coefficient w, calculate the yaw-side equivalent turning center distance Δ n value, where Δ n =wΔ nr +(1-w)Δ nβ ;

[0099] Calculate the steering angle of each axis;

[0100] Conventional steering is completed by performing corner allocation according to the preset corner allocation control strategy.

[0101] As an optional implementation manner of the embodiment of the present invention, calculating the steering angle of each axis includes:

[0102] The steering angle of each axis under the Ackerman equivalent steering model is calculated by the following formula:

[0103]

[0104] Among them, X i is the displacement from the i-th axis to the center of mass of the vehicle.

[0105] As an optional implementation manner of the embodiment of the present invention, the preset steering angle distribution control strategy includes: controlling the sideslip angles from the second axis to the nth axis to be equal.

[0106] In specific implementation, the conventional steering mode (hierarchical control) of the present invention is realized as follows:

[0107] Conventional steering mode is suitable for wheels under normal driving conditions. The electronic steering system can control the steering of the rear axle wheels according to the driver's needs, enhancing the high-speed stability of the vehicle. This solution is analyzed based on a 6-axle vehicle, and the relevant solution is also applicable to n-axle vehicles. Using the yaw-side equivalent steering model of multi-axle vehicles, a hierarchical control method is used to achieve wheel angle distribution. Its basic workflow is as follows: Figure 6 The details are as follows:

[0108] (1) According to the derivation of the established two-degree-of-freedom linear vehicle model and the driver's subjective calibration requirements, the unified steady-state yaw rate gain characteristic G of the n-axis vehicle is obtained. ω and the steady-state center of mass sideslip angle gain G β ;

[0109] (2) Using the yaw-side equivalent steering model of a multi-axle vehicle to calculate the Ackerman equivalent steering center distance Δ of the yaw characteristic nω and the Ackerman equivalent turning center distance Δ of the center of mass side slip characteristic nβ ;

[0110] (3) According to the equivalent bias (which can be calibrated manually), the weight coefficient w is given, and then the final Δ is obtained by adding them together. n value.

[0111] Δ n =wΔ nr +(1-w)Δ nβ

[0112] (4) The upper feedforward control distributes the total turning angle of each axis under the single-track model. The weight of the Ackerman equivalent turning center distance of the yaw characteristic is set to 0.5, that is, w = 0.5. And the steady-state center of mass side slip angle gain is 0, that is, G β = 0, Ackerman equivalent steering center distance Δ n It can be expressed as:

[0113]

[0114] According to the above formula, Δ n The steering angle of each axis under the Ackerman equivalent steering model can be calculated by the following formula.

[0115]

[0116] (5) The lower layer realizes the corner distribution of dual-track vehicles. With the goal of reducing tire wear and improving driving economy, the lower layer corner distribution control is designed.

[0117] Research literature indicates that tire cornering wear can be directly calculated based on the tire's slip angle, with greater slip angles leading to greater tire wear. Therefore, controlling tire cornering wear can be directly translated into controlling the slip angle. Optimization shows that total tire wear is minimized when the slip angles of all axles are exactly equal—that is, when the left and right wheels on the same axle have equal slip angles.

[0118] To obtain the total minimum tire wear rate, the following relationship must be met:

[0119]

[0120] The vehicle studied in this paper is a fully steered vehicle. The first axle and the steering wheel are mechanically connected, the angle transmission ratio is fixed, and the rear five axles are electrically controlled hydraulic steering systems, whose angle values ​​can be adjusted according to control requirements. The lower-level control goal proposed in this scheme is to make the side slip angles of the rear five axles completely equal, that is, to meet the following requirements in steady state and transient state respectively:

[0121]

[0122] Among them, Δ n is the displacement of the vehicle's steering center to its center of mass on the X-axis.

[0123] As an optional implementation manner of the embodiment of the present invention, locking the corresponding steering shaft according to the steering system fault state includes:

[0124] In redundant mode, the steering shaft close to the steering center is locked;

[0125] In the fault mode, the steering shafts other than the first and second steering shafts are locked.

[0126] In specific implementation, the redundancy and failure mode of the present invention are realized as follows:

[0127] When the vehicle needs to improve high-speed driving stability or part of the electronic steering system fails, the locking mode can be used to improve the vehicle's safety performance.

[0128] (1) Redundancy mode

[0129] When the vehicle is driving steadily at low or medium speeds, lock the third and fourth axles. Because the third and fourth axles are close to the steering center, their steering angles are relatively small or even require almost no steering. When the first axle's steering angle is small, the steering angles of the third and fourth axles may be even smaller than the tire's side slip angle. In this case, locking the third and fourth axles can reduce control requirements and appropriately minimize tire wear. The distribution of the wheel angles is as follows:

[0130]

[0131]

[0132] Among them, u is the actual vehicle speed, v is the minimum locking speed, and v+τ is the maximum locking speed. v and τ can be calibrated according to the different requirements of different vehicle models.

[0133] (2) Failure mode

[0134] When one or more of the rear four axles experience a steering failure, the rear four axles are locked. This steering mode is generally selected when the vehicle's electronically controlled hydraulic steering system fails or the steering system becomes extremely uncontrollable and dangerous, such as when a steering failure occurs during high-speed driving. Selecting this steering mode locks all four rear axles and prevents them from steering, leaving only the front two axles for steering. This ensures that the vehicle still has a certain degree of steering capability and can be turned safely. The distribution relationship of the wheel angles is as follows:

[0135]

[0136] When a wheel is at a certain angle and cannot be instantly adjusted to zero and locked, a reasonable return angular velocity must be designed based on the wheel angle and actual vehicle speed. This parameter requires manual calibration. If the second axle fails, the control strategy of locking the rear four axles is still used to ensure the stability of the multi-axle vehicle. An electronic steering fault warning light should be installed on the vehicle's instrument panel. If any of the five rear axles fails, the driver should be reminded to pull over, slow down, and repair the vehicle promptly, as appropriate.

[0137] Thus, the multi-mode steering control method for a multi-axle all-wheel steering vehicle provided by the embodiment of the present invention proposes a multi-mode steering control solution for a multi-axle all-wheel steering vehicle. By controlling the all-wheel steering angle of the chassis electronically, the steering performance of the multi-axle vehicle can be effectively improved, solving the problems of low steering flexibility, high wear of steering tires, and high steering working condition requirements of multi-axle vehicles. It has the following beneficial effects:

[0138] (1) Improve the vehicle's steering flexibility: Multi-wheel steering enables the vehicle to have better maneuverability in narrow spaces.

[0139] (2) Improve driving stability: Under different driving speeds and working conditions, the driving stability of the vehicle can be improved by adjusting the steering angle of each wheel.

[0140] (3) Optimize vehicle economy: According to actual driving needs, reasonably allocate the steering angle of each wheel to reduce energy consumption and tire wear, and improve driving economy.

[0141] (4) Improve driving comfort: Through multi-mode steering control, the driver can operate the vehicle more easily and comfortably.

[0142] (5) Adapt to different driving environments: The vehicle can select the appropriate steering mode according to different driving environments (such as urban roads, highways, off-road roads, etc.) to improve driving safety.

[0143] The present invention also provides a multi-mode steering control device for a multi-axle all-wheel steering vehicle, and the multi-mode steering control device for the multi-axle all-wheel steering vehicle applies the above method. The following is only a brief description of the multi-mode steering control device for the multi-axle all-wheel steering vehicle. For other matters not covered, please refer to the relevant description of the multi-mode steering control method for the multi-axle all-wheel steering vehicle, including: a processor, a memory;

[0144] The memory is used to store computer programs;

[0145] The processor is configured to execute the multi-mode steering control method for the multi-axle all-wheel steering vehicle as described above by calling the computer program.

[0146] It can be seen that the multi-mode steering control device for a multi-axle all-wheel steering vehicle provided by the embodiment of the present invention proposes a multi-mode steering control scheme for a multi-axle all-wheel steering vehicle. Through the electronic all-wheel angle control of the chassis, the steering performance of the multi-axle vehicle can be effectively improved, and the problems of low steering flexibility of the multi-axle vehicle, large wear of the steering tires, and high steering working conditions requirements can be solved.

[0147] The above are merely embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should all be included within the scope of the claims of the present application.

Claims

1. A multi-mode steering control method for a multi-axle all-wheel steering vehicle, characterized in that: include: Get the steering mode request; Enter the corresponding steering mode according to the current motion state and fault state; When there is no fault, a steering control request is obtained and a target steering mode is entered for steering control; wherein the steering control request includes a stationary steering control request, a diagonal steering control request, and a normal steering control request, and the target steering modes include a stationary steering mode, a diagonal steering mode, and a normal steering mode; When a fault occurs, a steering control request is obtained, the system enters the fault steering mode for steering control, and locks the corresponding steering shaft according to the steering system fault status.

2. The method according to claim 1, characterized in that Also includes: Establish a linear two-degree-of-freedom model for an n-axis steering vehicle; According to the linear two-degree-of-freedom model of the n-axis steering vehicle, the unified steady-state yaw angular velocity gain expression, the steady-state center of mass sideslip angle gain expression, the equivalent wheelbase expression of the n-axis steering vehicle, the equivalent stability coefficient expression of the n-axis steering vehicle, the equivalent steering center distance expression of the n-axis steering vehicle and the equivalent center of mass sideslip angle coefficient expression of the n-axis steering vehicle are obtained.

3. The method according to claim 2, characterized in that When the steering control request is an in-place steering control request, entering the target steering mode to perform steering control includes: Control the vehicle according to the wheel angle of each axle Perform a pivot turn; Among them, X Gi is the distance from each axis to the vehicle's geometric center, B w is the wheelbase, and ± means that the turning angles of coaxial wheels are equal in size but opposite in direction.

4. The method according to claim 3, characterized in that When the steering control request is an oblique steering control request, entering the target steering mode to perform steering control includes: Control the vehicle according to the relationship between the wheel angles of each axle: Perform oblique turns; Among them, δ1 is the wheel angle of the first axis, ε i1 is the rotation angle ratio of the i-th axis to the 1st axis, 5. The method according to claim 4, characterized in that When the steering control request is a normal steering control request, entering the target steering mode according to the steering control request includes: A yaw-skew equivalent steering model for a multi-axle vehicle is used, and a hierarchical control method is employed to achieve wheel angle distribution for conventional steering.

6. The method according to claim 5, characterized in that The method of using a multi-axle vehicle yaw-slope equivalent steering model and a hierarchical control method to realize wheel angle distribution for conventional steering includes: According to the linear two-degree-of-freedom model of the n-axis steering vehicle, the unified steady-state yaw rate gain characteristic G of the n-axis vehicle is obtained. ω and the steady-state center of mass sideslip angle gain G β ; The yaw-side equivalent steering model of a multi-axle vehicle is used to calculate the Ackerman equivalent steering center distance Δ of the yaw characteristic. nω and the Ackerman equivalent turning center distance Δ of the center of mass side slip characteristic nβ ; According to the equivalent bias weight coefficient w, calculate the yaw-side equivalent turning center distance Δ n value, where Δ n =wΔ nr +(1-w)Δ nβ ; Calculate the steering angle of each axis; Conventional steering is completed by performing corner allocation according to the preset corner allocation control strategy.

7. The method according to claim 6, characterized in that Calculating the steering angle of each axis includes: The steering angle of each axis under the Ackerman equivalent steering model is calculated by the following formula: Among them, X i is the displacement from the i-th axis to the center of mass of the vehicle.

8. The method according to claim 7, characterized in that The preset corner distribution control strategy includes: Control the slip angles from the second axis to the nth axis to be equal.

9. The method according to claim 8, characterized in that The locking of the corresponding steering shaft according to the steering system fault state includes: In redundant mode, the steering shaft close to the steering center is locked; In the fault mode, the steering shafts other than the first and second steering shafts are locked.

10. A multi-mode steering control device for a multi-axle all-wheel steering vehicle, characterized in that: include: Processor, memory; The memory is used to store computer programs; The processor is configured to execute the multi-mode steering control method for a multi-axle all-wheel steering vehicle according to any one of claims 1 to 9 by calling the computer program.

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