Transverse control method and device for double-shaft steering vehicle and double-shaft steering vehicle

Abstract

The invention relates to a double-shaft steering vehicle transverse control method and device and a double-shaft steering vehicle, and the double-shaft steering vehicle transverse control method comprises the steps that vehicle state information and reference track information are obtained; constructing a vehicle model according to the vehicle state information and the reference trajectory information, wherein the vehicle model comprises a front and rear axle steering kinematics model and a front axle steering two-degree-of-freedom dynamics model; under the condition that the vehicle speed is smaller than a speed threshold value, a transverse control algorithm is designed according to the front and rear axle steering kinematic model, and under the condition that the vehicle speed is not smaller than the speed threshold value, the transverse control algorithm is designed according to the front and rear axle steering kinematic model or the front axle steering two-degree-of-freedom kinetic model; a transverse LQR controller is designed according to the vehicle model, the optimal wheel rotation angle is calculated, and transverse control over the vehicle is conducted according to the optimal wheel rotation angle.

Description

Technical Field

[0001] The present disclosure relates to the field of intelligent driving technology, and in particular, to a lateral control method, a control device, and a double-axle steering vehicle for a double-axle steering vehicle. Background Art

[0002] A double-axle steering vehicle is a special vehicle with two sets of steering mechanisms at the front and rear and the same dynamic performance for driving forward and backward. Such vehicles have a small turning radius and flexible steering performance, and are more convenient when passing through narrow streets, sharp turns, roundabouts, or entering and exiting parking spaces.

[0003] During the control process of a double-axle steering vehicle, it is necessary to consider the influence of multiple variables such as the steering angles and steering speeds of the front and rear axles on lateral control, resulting in high control complexity. When switching between multiple steering modes, it is easy to exacerbate the instability of vehicle driving. The front and rear axles of a double-axle steering vehicle have high requirements for steering control accuracy and steering response speed. Therefore, when driving at high speed, the tolerance is low, and a small deviation may cause the vehicle to lose control. Summary of the Invention

[0004] Embodiments of the present disclosure provide a lateral control method, a control device, and a double-axle steering vehicle for a double-axle steering vehicle, which can improve the stability of a double-axle steering vehicle during mode switching and high-speed driving.

[0005] According to a first aspect of the present disclosure, there is provided a lateral control method for a double-axle steering vehicle, including:

[0006] Obtain vehicle state information and reference trajectory information;

[0007] Construct a vehicle model according to the vehicle state information and the reference trajectory information, where the vehicle model includes a front and rear axle steering kinematic model and a front axle steering two-degree-of-freedom dynamic model;

[0008] When the vehicle speed is less than the speed threshold, design a lateral control algorithm according to the front and rear axle steering kinematic model. When the vehicle speed is not less than the speed threshold, design a lateral control algorithm according to the front and rear axle steering kinematic model or the front axle steering two-degree-of-freedom dynamic model;

[0009] Design a lateral LQR controller according to the vehicle model and calculate the optimal wheel steering angle, and perform lateral control of the vehicle according to the optimal wheel steering angle.

[0010] In some embodiments, when the vehicle speed is not less than the speed threshold, the control method further includes:

[0011] When the rear wheel steering angle is not equal to zero, execute a rear wheel steering angle zeroing algorithm to calculate the rear wheel steering angle control amount, and design a lateral control algorithm according to the rear wheel steering angle control amount and the front and rear axle steering kinematic model;

[0012] When the rear wheel steering angle is equal to zero, a lateral control algorithm is designed according to the two-degree-of-freedom dynamic model of the front axle steering.

[0013] In some embodiments, during the process of the vehicle executing the rear wheel steering angle zeroing algorithm, the vehicle speed is fixed at a speed threshold, and when the rear wheel steering angle is equal to zero, the vehicle speed limit is lifted.

[0014] In some embodiments, the rear wheel steering angle zeroing algorithm includes:

[0015] According to the distance l from the front wheel of the vehicle to the center of mass f and the distance l from the rear wheel of the vehicle to the center of mass r and the curvature k at the preview trajectory point in the reference trajectory pre calculate the reference steering angle value δ ref (t + Δt) at the preview trajectory point in the reference trajectory;

[0016] According to the wheel steering angle value δ veh (t) and the reference steering angle value δ ref (t + Δt) calculate the steering angle change amount Δδ ref at the preview trajectory point in the reference trajectory, and the steering angle change amount Δδ ref satisfies the vehicle steering angle change rate constraint, and the vehicle steering angle change rate includes the maximum steering angle change rate Δδ fmax of the vehicle's front wheels and the maximum steering angle change rate Δδ rmax of the vehicle's rear wheels;

[0017] According to the maximum steering angle change rate Δδ rmax of the vehicle's rear wheels, calculate the initial rear wheel steering angle change amount Δδ r_init when the rear wheel steering angle is zero;

[0018] According to the vehicle's rear wheel steering angle δ r and the steering angle change amount Δδ ref calculate the rear wheel steering angle change amount Δδ r_end ;

[0019] According to the vehicle's rear wheel steering angle δ r and the rear wheel steering angle change amount Δδ r_end calculate the rear wheel steering angle control amount δ r_c .

[0020] In some embodiments, the steering angle change amount Δδ ref satisfying the vehicle steering angle change rate constraint includes:

[0021]

[0022] In some embodiments, according to the maximum steering angle change rate Δδ rmaxCalculate the initial change in the rear wheel angle Δδ when the rear wheel angle returns to zero r_init including:

[0023]

[0024] In some embodiments, according to the rear wheel angle δ of the vehicle r and the change in angle Δδ ref calculate the change in the rear wheel angle Δδ r_end including:

[0025] When δ r <0, Δδ ref ≥0:

[0026]

[0027] When δ r ≥0, Δδ ref <0:

[0028]

[0029] When δ r 、Δδ ref is other values:

[0030] Δδ r_end =Δδ r_init .

[0031] In some embodiments, designing a lateral LQR controller according to the vehicle model and calculating the optimal wheel angle includes:

[0032] Construct and discretize the state deviation equation according to the vehicle model:

[0033] X(t + dt) = AX(t) + Bu(t).

[0034] In some embodiments, designing a lateral LQR controller according to the vehicle model and calculating the optimal wheel angle further includes:

[0035] Determine the number of iterations N and the preset accuracy eps;

[0036] Set the Q, R matrices, and set the initial iteration value as P N = Q;

[0037] Calculate the A, B matrices in the state deviation equation according to the vehicle state information and the reference trajectory information;

[0038] Loop iteration: k = N,..., 1, P k-1 = A T P k A - A T P k B(R + BT P k B) -1 B T P k A + Q, if ‖P k -P k-1 ‖ < eps, end the loop;

[0039] Calculate the feedback coefficient K = -(R + B T P k+1 B) -1 B T P k+1 A;

[0040] Calculate the optimal control quantity or the optimal control deviation quantity u = KX, and calculate the optimal control quantity u according to the optimal control quantity or the optimal control deviation quantity opt 。

[0041] According to the second aspect of the present disclosure, a lateral control device for a two - axis steering vehicle is proposed, which is used to implement the lateral control method of the two - axis steering vehicle in the above - mentioned embodiment.

[0042] According to the third aspect of the present disclosure, a two - axis steering vehicle is proposed, which includes the lateral control device of the two - axis steering vehicle in the above - mentioned embodiment.

[0043] Based on the above - mentioned technical solutions, the lateral control method of the two - axis steering vehicle in the embodiments of the present disclosure can provide strong support for the accurate and stable tracking control of the two - axis steering vehicle by collecting data, establishing a vehicle model, designing a control mode, and constructing a lateral controller to calculate the optimal wheel angles; adjusting the lateral control mode according to the real - time vehicle state information and the reference trajectory information, and calculating the optimal wheel angles of the two - axis steering vehicle can improve the accuracy of vehicle lateral control and the stability of the two - axis steering vehicle during mode switching and high - speed driving. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The drawings described herein are used to provide a further understanding of the present disclosure, and constitute a part of this application. The illustrative embodiments of the present disclosure and their descriptions are used to explain the present disclosure and do not constitute an improper limitation of the present disclosure. In the drawings:

[0045] Figure 1 is a schematic flow chart of some embodiments of the lateral control method of the two - axis steering vehicle of the present disclosure.

[0046] Figure 2 is a schematic flow chart of other embodiments of the lateral control method of the two - axis steering vehicle of the present disclosure.

[0047] Figure 3 is a schematic diagram of the front - and - rear axle steering kinematic model of some embodiments of the lateral control method of the two - axis steering vehicle of the present disclosure.

[0048] Figure 4 This is a schematic diagram of the front axle steering two-degree-of-freedom dynamic model for some embodiments of the lateral control method of the disclosed dual-axis steering vehicle. Detailed implementation manners

[0049] Various exemplary embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. The description of the exemplary embodiments is merely illustrative and in no way limits the present disclosure and its application or use. The present disclosure can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are provided to make the present disclosure thorough and complete and to fully convey the scope of the present disclosure to those skilled in the art. It should be noted that: Unless otherwise specifically stated, the relative arrangements of components and steps, the compositions of materials, numerical expressions and values set forth in these embodiments should be construed as merely exemplary and not as limitations.

[0050] The terms "first", "second" and similar terms used in the present disclosure do not denote any order, quantity or importance, but are only used to distinguish different parts. Words such as "including" or "comprising" mean that the elements before the word cover the elements listed after the word, and do not exclude the possibility of also covering other elements. Terms such as "upper", "lower", "left", "right" are only used to represent relative positional relationships, and when the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0051] In the present disclosure, when it is described that a specific device is located between a first device and a second device, there may or may not be an intermediate device between the specific device and the first device or the second device. When it is described that a specific device is connected to other devices, the specific device may be directly connected to the other devices without an intermediate device, or may not be directly connected to the other devices but have an intermediate device.

[0052] All terms used in the present disclosure (including technical terms or scientific terms) have the same meaning as understood by those of ordinary skill in the art to which the present disclosure pertains, unless otherwise specifically defined. It should also be understood that terms defined in a general dictionary such as should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and should not be interpreted in an idealized or overly formal sense unless explicitly defined as such here.

[0053] Techniques, methods and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, the techniques, methods and devices should be regarded as part of the specification.

[0054] Based on the above embodiments of the present disclosure, without explicit negation or conflict, the technical features of one embodiment can be beneficially combined with one or more other embodiments.

[0055] To make the content of the present disclosure clearer and to more conveniently describe the present disclosure, some abbreviations and definitions of key terms are given here. The definitions of these specific terms do not constitute a limitation on the protection scope of the present disclosure.

[0056] Biaxial steering vehicle: A biaxial steering vehicle refers to a vehicle that realizes the steering function through the coordinated steering of two axles.

[0057] Lateral control: By controlling the wheel angle, the vehicle always travels along the desired path while ensuring the driving safety and ride comfort of the vehicle.

[0058] The inventors found during the research process that the steering control of the front and rear axles of a biaxial steering vehicle is highly complex, and unreasonable steering mode switching will seriously affect the driving stability of the vehicle. At high speeds, strict requirements are imposed on the steering control accuracy and steering response speed, and the steering stability and safety are low.

[0059] To solve at least one of the above problems, first, the present disclosure provides a lateral control method for a biaxial steering vehicle. In some embodiments, as Figure 1 and Figure 2 shown, the lateral control method for a biaxial steering vehicle includes:

[0060] S1. Obtain vehicle state information and reference trajectory information;

[0061] S2. Construct a vehicle model based on the vehicle state information and reference trajectory information. The vehicle model includes a front and rear axle steering kinematic model and a front axle steering two-degree-of-freedom dynamic model;

[0062] S3. When the vehicle speed is less than the speed threshold V l , design a lateral control algorithm according to the front and rear axle steering kinematic model. When the vehicle speed is not less than the speed threshold V l , design a lateral control algorithm according to the front and rear axle steering kinematic model or the front axle steering two-degree-of-freedom dynamic model;

[0063] S4. Design a lateral LQR controller according to the vehicle model and calculate the optimal wheel angle, and perform lateral control of the vehicle according to the optimal wheel angle.

[0064] Specifically, the vehicle state information is the vehicle real-time state data obtained by the vehicle body sensor, including at least the vehicle position (x v , y v , z v ), the vehicle speed v v, vehicle heading angle ψ, and vehicle front wheel steering angle δ f and vehicle rear wheel steering angle δ r and other information.

[0065] Specifically, the reference trajectory information is the expected vehicle driving trajectory, and the dual-axis steering vehicle lateral control method is used to control the vehicle to drive according to the reference trajectory. The reference trajectory is based on the trajectory data of the decision-making and planning module and is saved in the form of discrete points. The attributes of the reference trajectory points at least include the trajectory point coordinates (x i , y i , z i ), heading angle θ i , curvature k i ; where i is the trajectory point index.

[0066] In some embodiments, a front and rear axle steering kinematic model and a front axle steering two-degree-of-freedom dynamic model are constructed and the models are simplified. The specific implementation process is as follows:

[0067] S21: For a dual-axis steering vehicle, the front axle and rear axle in this article refer to the front axle and rear axle along the vehicle driving direction, rather than the front axle and rear axle of the vehicle body.

[0068] S22: The front and rear axle steering kinematic model is established based on the geometric relationship of the control system without considering the forces affecting the motion. Refer to Figure 3 , where the left and right front wheels of the vehicle are replaced by one wheel located at point A, the left and right rear wheels are replaced by one wheel located at point B, point C is the vehicle center of mass, point o is the vehicle instantaneous rotation center, and point R is the radius of the vehicle path.

[0069] Specifically, the equation of the front and rear axle steering kinematic model is as follows:

[0070]

[0071] In the formula: X: the X coordinate of the vehicle in the Cartesian coordinate system; Y: the Y coordinate of the vehicle in the Cartesian coordinate system; v: the vehicle speed; ψ: the vehicle heading angle; β: the vehicle sideslip angle; l f : the distance from the vehicle front wheel to the center of mass; l r : the distance from the vehicle rear wheel to the center of mass; δ f : the vehicle front wheel steering angle; δ r : the vehicle rear wheel steering angle.

[0072] When the vehicle center of mass is at the center point of the rear axle, the differential equation can be simplified to:

[0073]

[0074] The control quantity of the above front and rear axle steering kinematic model is u = [δ f δr T , when the front and rear axle steering is converted to front axle steering, the rear wheel angle δ of the vehicle r = C is a constant, and the control variable at this time is u = [δ f .

[0075] S23: The two-degree-of-freedom vehicle dynamics model for front axle steering takes into account the forces and lateral displacements of the vehicle tires, referring to Figure 4 , where x and y are the x-axis and y-axis in the vehicle body coordinate system, and v f is the front wheel speed, v r is the rear wheel speed, α f is the front wheel side slip angle, α r is the rear wheel side slip angle, F yf is the front wheel lateral force, F yr is the rear wheel lateral force.

[0076] Specifically, the equations of the dynamics model are as follows:

[0077]

[0078] In the formula: Vehicle lateral speed; Vehicle yaw rate; v x : The component of the vehicle speed v on the x-axis; δ f : Vehicle front wheel angle; C αf : Front wheel side slip stiffness; C ar : Rear wheel side slip stiffness; I z : Moment of inertia about the z-axis.

[0079] The control variable of the above two-degree-of-freedom vehicle dynamics model for front axle steering is u = [δ f .

[0080] This embodiment can provide strong support for the precise and stable trajectory tracking control of a two-axle steering vehicle by collecting data, establishing a vehicle model, designing a control mode, and constructing a lateral controller to calculate the optimal wheel angle. It can not only improve the flexibility of the vehicle during low-speed driving but also ensure the stability of the vehicle during high-speed driving; by adjusting the lateral control mode according to the real-time vehicle state information and reference trajectory information and calculating the optimal wheel angle of the two-axle steering vehicle, it can improve the accuracy of vehicle lateral control and the stability of the two-axle steering vehicle during mode switching and high-speed driving.

[0081] In some embodiments, as Figure 2 shown, when the vehicle speed is not less than the speed threshold, the control method further includes:

[0082] ​When the rear wheel steering angle is not equal to zero, the rear wheel steering angle zeroing algorithm is executed to calculate the rear wheel steering angle control amount, and the lateral control algorithm is designed according to the rear wheel steering angle control amount and the front and rear axle steering kinematic model;

[0083] When the rear wheel steering angle is zero, the lateral control algorithm is designed according to the two-degree-of-freedom dynamic model of the front axle steering.

[0084] In some embodiments, the control method includes:

[0085] S31: When the vehicle speed is lower than the speed threshold V l When the vehicle speed is higher than the speed threshold V l When the rear wheel turning angle δ r ≠0, execute the rear wheel angle zeroing algorithm, and use the front and rear axle steering kinematics model with the rear wheel angle as a constant to design the lateral control algorithm; until the rear wheel angle δ r =0, the lateral control algorithm is designed using the two-degree-of-freedom dynamics model of the front axle steering.

[0086] S32: When the vehicle executes the rear wheel angle zeroing algorithm, the vehicle speed is fixed to the speed threshold V l When δ r =0, the speed limit is released.

[0087] S33: The rear wheel steering angle zeroing algorithm calculates the rear wheel steering angle control value δ based on the vehicle state information and the reference trajectory information r_c , the specific calculation method is as follows:

[0088] First, calculate the reference turning angle value of the vehicle at the preview trajectory point in the reference trajectory:

[0089] δ ref (t+Δt)=(l f +l r )·k pre ;

[0090] Where: k pre : The curvature of the preview trajectory point in the reference trajectory; t: The absolute time of the vehicle at the current moment; Δt: The time step of the control module.

[0091] Based on the current vehicle state, calculate the change in the turning angle at the preview trajectory point:

[0092] Δδ ref =δ ref (t+Δt)-δ veh (t);

[0093] Where: veh (t): Wheel steering angle value in vehicle state, including front wheel and rear wheel steering angles.

[0094] The change in the pre - preview trajectory point turning angle needs to satisfy the vehicle turning rate constraint:

[0095]

[0096] In the formula: Δδ fmax : The maximum turning rate of the vehicle's front wheels; Δδ rmax : The maximum turning rate of the vehicle's rear wheels.

[0097] Calculate the initial change in the rear - wheel turning angle when the rear - wheel returns to zero based on the rear - wheel turning rate constraint:

[0098]

[0099] According to the values of δ r , Δδ ref , the calculation of the rear - wheel turning angle change is as follows:

[0100] When δ r < 0, Δδ ref ≥0:

[0101]

[0102] When δ r ≥0, Δδ ref <0:

[0103]

[0104] When δ r , Δδ ref takes other values:

[0105] Δδ r_end =Δδ r_(n(t ;

[0106] The final calculated rear - wheel turning control amount of the vehicle rear - wheel turning angle zeroing algorithm is:

[0107] δ r_c =δ r +Δδ r_e)d .

[0108] Specifically, the above - mentioned embodiment records the design of a lateral control algorithm using a kinematic model of front - and - rear - axle steering with a constant rear - wheel turning angle. Based on the simplified kinematic model in S22, let the vehicle rear - wheel turning angle be the given value δ r_c calculated in S33. At this time, the vehicle kinematic model is:

[0109]

[0110] In some embodiments, designing a lateral LQR controller according to a vehicle model and calculating the optimal wheel steering angle includes:

[0111] S41: Construct and discretize the state error equation based on the vehicle model selected in part S3:

[0112] X(t + dt) = AX(t) + Bu(t);

[0113] S42: Construct a discrete LQR lateral controller to solve for the optimal control quantity. The solution steps of the LQR algorithm are as follows:

[0114] 1. Determine the number of iterations N and the preset precision eps;

[0115] 2. Set the Q and R matrices, and set the initial iteration value as P N = Q;

[0116] 3. Calculate the A and B matrices in the state deviation equation according to the vehicle state information and the reference trajectory;

[0117] 4. Iterate in a loop, k = N,..., 1, P k-1 = A T P k A - A T P k B(R + B T R k B) -1 B T P k a + Q, if ‖P k - P k-1 ‖ < eps, end the loop;

[0118] 5. Calculate the feedback coefficient: K = -(R + B T P k+1 B) -1 B T P k+1 A;

[0119] 6. The optimal control quantity or control deviation quantity is u = KX;

[0120] 7. Calculate the optimal control quantity u opt , in step 6, if the kinematic model of a vehicle with front and rear axle steering is adopted, the optimal control deviation quantity obtained in step 6 of the LQR algorithm solution steps needs to be combined with the reference steering angle value in S33 to obtain the optimal control quantity; if the dynamic model of a two-degree-of-freedom vehicle with front axle steering is adopted, the optimal control quantity obtained in step 6 of the LQR algorithm solution steps is u opt = u.

[0121] Specifically, by using the optimal control quantity u of the vehicle steering angle calculated in the above embodiments optSend it to the vehicle's underbody by - wire control system to achieve the lateral control of the vehicle.

[0122] The control method of this embodiment is based on the lateral control algorithm of the front - rear axle steering kinematic model and the front - axle steering two - degree - of - freedom dynamic model, which not only improves the flexibility of the vehicle during low - speed driving but also ensures the stability of the vehicle during high - speed driving. The control method is based on vehicle state information and reference trajectory information, and designs and implements control mode conversion and rear - wheel angle zeroing algorithms, which can ensure the stability and safety of the vehicle during control mode switching.

[0123] Secondly, the present disclosure proposes a lateral control device for a two - axle steering vehicle to implement the lateral control method of the two - axle steering vehicle in the above - mentioned embodiment.

[0124] In addition, the present disclosure also proposes a two - axle steering vehicle, which includes a detection module, the lateral control device for a two - axle steering vehicle in the above - mentioned embodiment, and an execution module.

[0125] Specifically, the detection module includes a variety of sensors for obtaining vehicle state information and reference trajectory information. Optionally, the two - axle steering vehicle includes an autonomous - driving mining dump truck.

[0126] The two - axle steering vehicle of this embodiment has high stability during multi - steering mode switching, high fault tolerance during high - speed driving, low risk of vehicle out - of - control, and high running safety.

[0127] The above has introduced in detail a lateral control method, a control device, and a two - axle steering vehicle provided by the present disclosure. Specific embodiments are used in this article to elaborate on the principle and implementation manner of the present disclosure. The description of the above embodiments is only used to help understand the method and its core idea of the present disclosure. It should be noted that for those of ordinary skill in the art of this technology, without departing from the principle of the present disclosure, several improvements and modifications can be made to the present disclosure, and these improvements and modifications also fall within the protection scope of the claims of the present disclosure.

Claims

1. A lateral control method for a double-axle steering vehicle, characterized in that Including: Obtain vehicle state information and reference trajectory information; Construct a vehicle model according to the vehicle state information and the reference trajectory information, where the vehicle model includes a front and rear axle steering kinematic model and a front axle steering two-degree-of-freedom dynamic model; When the vehicle speed is less than the speed threshold, design a lateral control algorithm according to the front and rear axle steering kinematic model. When the vehicle speed is not less than the speed threshold, design a lateral control algorithm according to the front and rear axle steering kinematic model or the front axle steering two-degree-of-freedom dynamic model; Design a lateral LQR controller according to the vehicle model and calculate the optimal wheel steering angle, and perform lateral control of the vehicle according to the optimal wheel steering angle.

2. The lateral control method for a biaxial steering vehicle according to claim 1, characterized in that When the vehicle speed is not less than the speed threshold, the control method further includes: When the rear wheel steering angle is not equal to zero, execute a rear wheel steering angle zeroing algorithm to calculate the rear wheel steering angle control amount, and design a lateral control algorithm according to the rear wheel steering angle control amount and the front and rear axle steering kinematic model; When the rear wheel steering angle is equal to zero, design a lateral control algorithm according to the front axle steering two-degree-of-freedom dynamic model.

3. The lateral control method for a biaxial steering vehicle according to claim 2, characterized in that, During the process of the vehicle executing the rear wheel steering angle zeroing algorithm, the vehicle speed is fixed at the speed threshold. When the rear wheel steering angle is equal to zero, the vehicle speed limit is lifted.

4. The lateral control method for a biaxial steering vehicle according to claim 2, characterized in that, The rear wheel steering angle zeroing algorithm includes: According to the distance \(l\) from the front wheel of the vehicle to the center of mass f , the distance \(l\) from the rear wheel of the vehicle to the center of mass r and the curvature \(k\) at the preview trajectory point in the reference trajectory pre calculate the reference steering angle value \(\delta\) of the vehicle at the preview trajectory point in the reference trajectory ref (t + \Delta t); According to the wheel rotation angle value δ veh (t) and the reference rotation angle value δ ref (t + Δt), calculate the change in rotation angle Δδ of the vehicle at the preview trajectory point in the reference trajectory ref , where the change in rotation angle Δδ ref satisfies the vehicle rotation angle change rate constraint, and the vehicle rotation angle change rate includes the maximum rotation angle change rate Δδ of the vehicle's front wheels fmax and the maximum rotation angle change rate Δδ of the vehicle's rear wheels rmax ; According to the maximum change rate Δδ of the rear wheel angle of the vehicle rmax calculate the initial change amount Δδ of the rear wheel angle when the rear wheel angle returns to zero r_init ; According to the rear wheel steering angle δ of the vehicle r and the steering angle change amount Δδ ref calculate the rear wheel steering angle change amount Δδ r_end ; According to the rear wheel steering angle δ of the vehicle r and the change amount Δδ of the rear wheel steering angle r_end calculate the control amount δ of the rear wheel steering angle r_c .

5. The lateral control method for a biaxial steering vehicle according to claim 4, characterized in that, The corner change amount Δδ ref Satisfying the vehicle corner change rate constraint includes:

6. The lateral control method for a biaxial steering vehicle according to claim 4, characterized in that According to the maximum cornering rate change Δδ of the rear wheels of the vehicle rmax calculate the initial change amount Δδ of the rear wheel cornering angle when the rear wheel cornering angle returns to zero r_init including:

7. The lateral control method for a biaxial steering vehicle according to claim 4, wherein, According to the rear wheel steering angle δ of the vehicle r and the steering angle change amount Δδ ref calculate the rear wheel steering angle change amount Δδ r_end including: When δ r < 0, Δδ ref ≥ 0: When δ r ≥ 0, Δδ ref < 0: When δ r , Δδ ref take other values: Δδ r_end = Δδ r_(n(t .

8. The lateral control method for a biaxial steering vehicle according to any one of claims 1 to 7, characterized in that, Designing a lateral LQR controller according to the vehicle model and calculating the optimal wheel steering angle includes: Construct and discretize the state deviation equation according to the vehicle model: X(t + dt) = AX(t) + Bu(t).

9. The lateral control method for a biaxial steering vehicle according to claim 8, characterized in that Designing a lateral LQR controller according to the vehicle model and calculating the optimal wheel steering angle further includes: Determine the number of iterations N and the preset accuracy eps; Set the Q and R matrices, and set the initial value of the iteration to P N = Q; Calculate the A and B matrices in the state deviation equation according to the vehicle state information and the reference trajectory information; Loop iteration: k = N,..., 1, P k-1 = A T P k A - A T P k B(R + B T P k B) -1 B T P k A + Q, if ‖P k - P k-1 ‖ < eps, end the loop; Calculate the feedback coefficient K = -(R + B T P k+1 B) -1 B T P k+1 A; Calculate the optimal control quantity or the optimal control deviation quantity \(u = KX\), and calculate the optimal control quantity \(u\) according to the optimal control quantity or the optimal control deviation quantity opt .

10. A lateral control device for a biaxial steering vehicle, characterized in that, Used to implement the lateral control method for a two-axle steering vehicle according to any one of claims 1 to 9.

11. A two-axle steering vehicle, characterized in that, Including the lateral control device for a two-axle steering vehicle according to claim 10.

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