Lane keeping control method and device for low-adhesion road surface

Abstract

The invention provides a lane keeping control method and device for a low-adhesion road surface, and the method comprises the steps: calculating a wheel slip rate according to a wheel angular velocity and a vehicle driving speed, and judging whether the road surface is the low-adhesion road surface or not according to the wheel slip rate; when it is judged that the road surface is the low-adhesion road surface, a preset gravity center adjustment coefficient is corrected according to the road surface friction coefficient, and meanwhile a peak lateral force value in a tire model corresponding to the target wheel is corrected; according to the real-time steering state of the vehicle and the corrected preset gravity center adjustment coefficient, the vehicle body height and the vehicle gravity center position are adjusted, and meanwhile the distribution condition of the wheel braking force is adjusted to optimize the road holding force of the target wheel; after the road holding force of the target wheel is optimized, the tire lateral force is calculated according to the corrected peak lateral force value, the compensation torque is calculated according to the tire lateral force and a pre-built yawing torque balance equation, and the vehicle system state is controlled to converge along the preset sliding mode surface through the compensation torque. According to the invention, the lane keeping effect is improved, and the driving safety is improved.

Description

Technical Field

[0001] This application relates to the field of vehicle technology, and more specifically, to a lane keeping control method and device for low-adhesion road surfaces. Background Technology

[0002] With the rapid development of automotive intelligence and autonomous driving technologies, lane keeping systems, as a core component of active safety technologies, directly affect driving safety and the driving experience, and have become one of the key technologies for improving vehicle intelligence. In complex road conditions, low-adhesion surfaces (such as icy, snowy, or waterlogged surfaces with a friction coefficient μ≤0.3) are widespread, which significantly reduces the adhesion between the tires and the road surface.

[0003] Current lane-keeping technologies are mainly based on traditional linear control theory. They acquire lane line information through sensors such as cameras and radar, and calculate steering commands using vehicle dynamics models to keep the vehicle within the lane. This technology can achieve good lane-tracking performance on dry, high-adhesion road surfaces (friction coefficient μ≥0.6), but its design often assumes ideal road conditions and does not fully consider the complex characteristics of low-adhesion road surfaces.

[0004] However, in low-adhesion road environments, due to insufficient tire grip, vehicles are prone to oversteering or understeering, resulting in lateral deviations often exceeding 0.3m, making it difficult to maintain high-precision lane tracking, and in severe cases, causing lane departure accidents. Summary of the Invention

[0005] In view of this, the purpose of this application is to provide a lane keeping control method and apparatus for low-adhesion road surfaces, which can solve at least one of the above-mentioned problems.

[0006] In a first aspect, embodiments of this application provide a lane keeping control method for low-adhesion road surfaces, the method comprising: The wheel slip ratio is calculated based on the obtained wheel angular velocity and vehicle speed, and the road surface is determined to be a low-adhesion road surface based on the wheel slip ratio. The road surface friction coefficient of the low-adhesion road surface is less than or equal to a preset friction threshold. When the road surface is determined to be a low-adhesion road surface, the preset center of gravity adjustment coefficient is corrected based on the real-time obtained road friction coefficient, and the peak lateral force value in the tire model corresponding to the target wheel is also corrected. The vehicle height and center of gravity position are adjusted according to the real-time steering status of the vehicle and the corrected preset center of gravity adjustment coefficient. At the same time, the distribution of wheel braking force is adjusted to optimize the grip of the target wheels. The preset center of gravity adjustment coefficient refers to the ratio of the actual center of gravity offset to the vehicle wheelbase. After optimizing the grip of the target wheel, the tire lateral force is calculated based on the corrected peak lateral force value, and a compensation torque is calculated based on the tire lateral force and the pre-constructed yaw moment balance equation. The compensation torque is used to control the convergence of the vehicle system state along a preset sliding surface. The preset sliding surface is determined by the actual yaw rate of the vehicle, the target yaw rate, the vehicle sideslip angle, and the weighting coefficient. The yaw moment balance equation is constructed based on the vehicle's yaw moment of inertia, yaw acceleration, the distance from the front axle to the center of gravity, and the distance from the rear axle to the center of gravity.

[0007] In one optional embodiment, the step of calculating the wheel slip ratio based on the obtained wheel angular velocity and vehicle speed, and determining whether the road surface is a low-adhesion road surface based on the wheel slip ratio, includes: Calculate the product of the wheel's angular velocity and its radius to obtain the wheel's rolling linear velocity; The wheel slip ratio is obtained by calculating the ratio of the difference between the rolling linear velocity and the vehicle speed to the vehicle speed. If the wheel slip ratio is greater than or equal to a preset slip ratio threshold, the road surface is determined to be a low-adhesion road surface.

[0008] In one optional embodiment, when the road surface is determined to be a low-adhesion road surface, correcting the preset center of gravity adjustment coefficient based on the real-time acquired road friction coefficient, and simultaneously correcting the peak lateral force value in the tire model corresponding to the target wheel, includes: When the road surface is determined to be a low-adhesion road surface, the road surface friction coefficient is obtained in real time through the roadside communication unit, and basic parameters in the preset parameter library are retrieved. The basic parameters include the default initial threshold of the preset center of gravity adjustment coefficient, the reference value of the peak lateral force of the dry road surface, and the reference value of the friction coefficient of the dry road surface. The road surface friction coefficient is used to classify low adhesion levels, and the preset center of gravity adjustment coefficient is adjusted based on the low adhesion level classification; wherein, the low adhesion level is positively correlated with the adjustment range of the default initial threshold of the preset center of gravity adjustment coefficient; the low adhesion levels include high-level low adhesion, medium-level low adhesion, and low-level low adhesion. Based on the proportional relationship between the road surface friction coefficient and the dry road surface friction coefficient reference value, the peak lateral force value in the tire model corresponding to the target wheel is corrected in real time; wherein, the peak lateral force value is determined by the dry road surface peak lateral force reference value and the proportional relationship.

[0009] In one optional embodiment, adjusting the vehicle height and center of gravity position based on the vehicle's real-time steering state and a corrected preset center of gravity adjustment coefficient, while simultaneously adjusting the distribution of wheel braking force to optimize the grip of the target wheels, includes: The real-time steering state of the vehicle is determined by collecting the vehicle steering state parameters, wherein the real-time steering state of the vehicle includes understeering state or oversteering state. Based on the vehicle's real-time steering status and the corrected preset center of gravity adjustment coefficient, the vehicle height and center of gravity position are adjusted by the active air suspension, while the wheel braking force distribution is adjusted by the electro-hydraulic braking system to optimize the grip of the target wheels; wherein, the adjustment range of the vehicle height is between -30mm and +30mm, and the braking torque applied by the electro-hydraulic braking system to the inner wheel does not exceed 200N·m.

[0010] In one optional embodiment, the vehicle steering state parameters include the actual yaw rate and the vehicle sideslip angle. Determining the real-time vehicle steering state using the collected vehicle steering state parameters includes: When the actual yaw rate is less than the target yaw rate and the vehicle sideslip angle is greater than the first preset threshold, the real-time steering state of the vehicle is determined to be understeering. When the actual yaw rate is greater than the target yaw rate and the vehicle sideslip angle is greater than the second preset threshold, the real-time steering state of the vehicle is determined to be oversteering; wherein the second preset threshold is less than the first preset threshold.

[0011] In one optional embodiment, the step of adjusting the vehicle height and center of gravity position via active air suspension based on the vehicle's real-time steering state and a corrected preset center of gravity adjustment coefficient, while simultaneously adjusting the wheel braking force distribution via an electro-hydraulic braking system to optimize the grip of the target wheels, includes: The target center of gravity offset is calculated by multiplying the corrected preset center of gravity adjustment coefficient with the vehicle wheelbase, and the center of gravity offset direction is determined according to the real-time steering state of the vehicle; wherein, in the understeering state, the center of gravity offset direction is towards the front axle of the vehicle, and in the oversteering state, the center of gravity offset direction is towards the rear axle of the vehicle. Based on the target center of gravity offset and vehicle curb weight, the required load adjustment for the front and rear axles is calculated. Combined with the adjustment range of vehicle height, the lifting stroke parameters of the active air suspension are calculated. The lifting stroke parameters are used to control the lifting action of the active air suspension to adjust the vehicle height and the position of the vehicle center of gravity. By combining the real-time vehicle speed, the braking force distribution ratio between the target wheel and the non-target wheel is calculated. Based on the braking force distribution ratio and the preset maximum braking torque threshold, the braking torque applied by the electro-hydraulic braking system to the inner wheel is calculated, so as to adjust the wheel braking force distribution through the braking torque and optimize the grip of the target wheel.

[0012] In one optional embodiment, after optimizing the grip of the target wheel, the step of calculating the tire lateral force based on the corrected peak lateral force value, and calculating a compensation torque based on the tire lateral force and a pre-constructed yaw moment balance equation, so as to control the convergence of the vehicle system state along a preset sliding surface through the compensation torque, includes: After optimizing the grip of the target wheel, the lateral forces of the front wheel and the rear wheel are calculated based on the corrected peak lateral force value and tire slip angle. Substitute the calculated front wheel lateral force and rear wheel lateral force into the pre-constructed yaw moment balance equation to calculate the basic compensation torque required to offset the current attitude deviation. The basic compensation torque is used to balance the difference in yaw moment generated by the front wheel lateral force and the rear wheel lateral force. Substitute the actual yaw rate and sideslip angle of the vehicle collected into the preset sliding surface formula to calculate the system state deviation value; The basic compensation torque is adjusted according to the system state deviation value to obtain the final compensation torque, which is used to correct the vehicle yaw attitude, so that the vehicle system state converges along the preset sliding surface and maintains lane stability.

[0013] In one optional embodiment, the preset sliding surface formula includes: s=ω-ω_d+k×β Where s represents the sliding surface, ω represents the actual yaw rate of the vehicle, ω_d represents the target yaw rate, β represents the vehicle sideslip angle, and k represents the weighting coefficient; The yaw moment balance equation is calculated using the following formula: Iz×rz=Fyf×a-Fyr×b+ΔMz Where Iz represents the vehicle's yaw moment of inertia, rz represents the yaw acceleration, a represents the distance from the front axle to the center of gravity, b represents the distance from the rear axle to the center of gravity, Fyf represents the lateral force of the front wheels, Fyr represents the lateral force of the rear wheels, and ΔMz represents the compensating torque.

[0014] In one optional embodiment, the tire model is represented by the following formula: Fy=D×sin(C×arctan(B×λ-E×(B×λ-arctan(B×λ)))) Where Fy represents the tire lateral force, B represents the stiffness factor, C represents the shape factor, D represents the peak lateral force, E represents the curve curvature factor, and λ represents the tire slip angle.

[0015] Secondly, embodiments of this application also provide a lane keeping control device for low-adhesion road surfaces, the device comprising: The road surface judgment module is used to calculate the wheel slip ratio based on the obtained wheel angular velocity and vehicle speed, so as to determine whether the road surface is a low-adhesion road surface based on the wheel slip ratio, wherein the road surface friction coefficient of the low-adhesion road surface is less than or equal to a preset friction threshold. The numerical correction module is used to correct the preset center of gravity adjustment coefficient based on the real-time obtained road friction coefficient when the road surface is determined to be a low-adhesion road surface, and at the same time correct the peak lateral force value in the tire model corresponding to the target wheel. The grip optimization module is used to adjust the vehicle height and center of gravity position based on the vehicle's real-time steering status and the corrected preset center of gravity adjustment coefficient, while also adjusting the distribution of wheel braking force to optimize the grip of the target wheels; wherein, the preset center of gravity adjustment coefficient refers to the ratio of the actual center of gravity offset to the vehicle wheelbase. The sliding mode control module is used to calculate the tire lateral force based on the corrected peak lateral force value after optimizing the grip of the target wheel, and to calculate the compensation torque based on the tire lateral force and the pre-constructed yaw moment balance equation, so as to control the vehicle system state to converge along the preset sliding surface through the compensation torque; wherein, the preset sliding surface is determined by the actual yaw rate of the vehicle, the target yaw rate, the vehicle sideslip angle and the weighting coefficient, and the yaw moment balance equation is constructed based on the vehicle yaw moment of inertia, yaw acceleration, the distance from the front axle to the center of gravity and the distance from the rear axle to the center of gravity.

[0016] Thirdly, embodiments of this application also provide an electronic device, including: a processor, a memory, and a bus, wherein the memory stores machine-readable instructions executable by the processor, and when the electronic device is running, the processor communicates with the memory via the bus, and when the machine-readable instructions are executed by the processor, the steps of the method described above are performed.

[0017] Fourthly, embodiments of this application also provide a computer-readable storage medium storing a computer program, which, when executed by a processor, performs the steps of the method described above.

[0018] The lane keeping control method and device for low-adhesion road surfaces provided in this application effectively solve the problem of oversteering or understeering caused by insufficient tire grip on low-adhesion road surfaces (ice, snow, water, friction coefficient μ≤0.3) in traditional lane keeping technology. It controls the lateral deviation within a small range, significantly improves the lane keeping effect, and increases driving safety.

[0019] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 A flowchart illustrating a lane keeping control method for low-adhesion road surfaces provided in this application embodiment; Figure 2 A schematic diagram of the structure of a lane keeping control device for low-adhesion road surfaces provided in an embodiment of this application; Figure 3 This is a schematic diagram of the structure of an electronic device provided in an embodiment of this application. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. Based on the embodiments of this application, every other embodiment obtained by those skilled in the art without inventive effort falls within the scope of protection of this application.

[0023] Please see Figure 1 , Figure 1 A flowchart illustrating a lane keeping control method for low-adhesion road surfaces provided in an embodiment of this application. Figure 1 As shown in the embodiments of this application, the method includes: S101. Calculate the wheel slip ratio based on the obtained wheel angular velocity and vehicle speed, and determine whether the road surface is a low-adhesion road surface based on the wheel slip ratio. The road friction coefficient of a low-adhesion road surface is less than or equal to a preset friction threshold. S102. When the road surface is determined to be a low-adhesion road surface, the preset center of gravity adjustment coefficient is corrected according to the real-time obtained road friction coefficient, and the peak lateral force value in the tire model corresponding to the target wheel is corrected at the same time. S103. Adjust the vehicle height and center of gravity position according to the real-time steering status of the vehicle and the corrected preset center of gravity adjustment coefficient, and at the same time adjust the distribution of wheel braking force to optimize the grip of the target wheel; wherein, the preset center of gravity adjustment coefficient refers to the ratio of the actual center of gravity offset to the vehicle wheelbase. S104. After optimizing the grip of the target wheel, calculate the tire lateral force based on the corrected peak lateral force value, and calculate the compensation torque based on the tire lateral force and the pre-constructed yaw moment balance equation, so as to control the convergence of the vehicle system state along the preset sliding surface through the compensation torque; wherein, the preset sliding surface is determined by the actual yaw rate of the vehicle, the target yaw rate, the vehicle sideslip angle and the weighting coefficient, and the yaw moment balance equation is constructed based on the vehicle yaw moment of inertia, yaw acceleration, the distance from the front axle to the center of gravity and the distance from the rear axle to the center of gravity.

[0024] The method provided in this application effectively solves the problem of oversteering or understeering caused by insufficient tire grip on low-adhesion road surfaces (ice, snow, water, friction coefficient μ≤0.3) in traditional lane keeping technology. It controls the lateral deviation within a small range, significantly improves the lane keeping effect, and increases driving safety.

[0025] The following is an exemplary description of steps S101 to S104 above: In step S101, the wheel slip ratio is calculated based on the obtained wheel angular velocity and vehicle speed, so as to determine whether the road surface is a low-adhesion road surface. The road friction coefficient of a low-adhesion road surface is less than or equal to a preset friction threshold.

[0026] In the above steps, wheel angular velocity refers to the angular velocity of each wheel of the vehicle, which can be acquired in real time by wheel speed sensors. For example, Hall effect speed sensors installed at the hubs of the four wheels can be used to acquire wheel rotation signals in real time, and the wheel angular velocity can be obtained after conversion by a signal processing module. Vehicle speed is the actual speed at which the vehicle moves in the longitudinal direction of travel, and it can be combined with the wheel rolling linear velocity to accurately calculate the wheel slip ratio. For example, vehicle speed can be obtained through the vehicle's GPS positioning system or onboard inertial navigation module.

[0027] Wheel slip ratio is a parameter that reflects the degree of relative slippage between the wheel and the ground. Specifically, wheel slip ratio can be calculated by the difference between the wheel's rolling linear velocity and the vehicle's traveling speed. Its function is to characterize the adhesion state between the wheel and the ground. When the slip ratio exceeds a certain threshold, it indicates that the ground adhesion has decreased, and the road surface is judged as having low adhesion.

[0028] Optionally, the preset friction threshold is a critical value of the friction coefficient that distinguishes between low-adhesion and non-low-adhesion road surfaces. Specifically, the preset friction threshold can be a critical value determined based on a large amount of road test data. Its function is to verify and calibrate the wheel slip ratio judgment results to ensure the accuracy of the low-adhesion road surface judgment. For example, combined with the critical condition for the failure of traditional lane keeping technology, the preset friction threshold is set to 0.3, that is, when the road surface friction coefficient μ≤0.3, it is determined to be a low-adhesion road surface.

[0029] In an optional embodiment, step S101 specifically includes the following steps: calculating the product of the wheel angular velocity and the wheel radius to obtain the wheel's rolling linear velocity; calculating the ratio between the difference between the rolling linear velocity and the vehicle's travel speed and the vehicle's travel speed to obtain the wheel slip ratio; if the wheel slip ratio is greater than or equal to a preset slip ratio threshold, the road surface is determined to be a low-adhesion road surface. Furthermore, the wheel slip ratio can be calculated using the following formula: s = (ω × r - v_x) / v_x, where ω is the wheel angular velocity, r is the wheel radius, and v_x is the longitudinal velocity, i.e., the vehicle's travel speed. For example, when the calculated slip ratio s ≥ 15%, the road surface can be preliminarily determined to be a low-adhesion road surface.

[0030] For example, the preset slip ratio threshold can be set to 15%. The wheel radius can be preset according to the vehicle model. For example, the wheel radius of a car is 0.33m. When the collected wheel angular velocity is 100rad / s, the wheel rolling linear velocity is 100×0.33=33m / s (i.e. 118.8km / h). If the vehicle speed is 30m / s (i.e. 108km / h), the wheel slip ratio is (33-30) / 30=10%, which is less than the preset slip ratio threshold of 15%, so the road surface can be determined to be a non-low adhesion road surface. If the vehicle speed is 28m / s (i.e. 100.8km / h), the wheel slip ratio is (33-28) / 28≈17.86%, which is greater than the preset slip ratio threshold of 15%, so the road surface can be determined to be a low adhesion road surface. Further verification can be performed by combining the road friction coefficient.

[0031] In step S102, when the road surface is determined to be a low-adhesion road surface, the preset center of gravity adjustment coefficient is corrected according to the real-time obtained road friction coefficient, and the peak lateral force value in the tire model corresponding to the target wheel is corrected at the same time.

[0032] In this step, the road surface friction coefficient, which can be acquired in real time, is a real-time physical parameter reflecting the ground's adhesion capability on low-adhesion surfaces. This real-time road surface friction coefficient is used to adapt the control strategy to road surfaces with different adhesion capabilities, ensuring the stability of the control effect. It can be obtained through roadside communication or onboard sensors. For example, the road surface friction coefficient data detected by roadside equipment can be acquired in real time through the roadside communication unit of a V2X (vehicle-to-everything) system, with a data update frequency of 1Hz; when the vehicle travels on an icy or snowy road surface, the acquired real-time road surface friction coefficient is 0.2.

[0033] Specifically, the preset center of gravity adjustment coefficient refers to the ratio of the actual center of gravity offset to the vehicle's wheelbase, used to quantify the degree of center of gravity offset. The preset center of gravity adjustment coefficient is a core parameter for controlling vehicle center of gravity offset, providing a quantitative basis for the active air suspension to adjust the center of gravity position. By dynamically correcting this coefficient, the center of gravity offset can be adapted to different road surface adhesion conditions. For example, the default initial threshold range of the preset center of gravity adjustment coefficient can be 0-0.1. When the vehicle is driving on a dry road surface, the coefficient can be 0.05; when driving on a low-adhesion road surface, it is corrected based on the real-time road friction coefficient.

[0034] Here, the target wheel is the wheel whose grip needs to be optimized. It is typically determined based on the vehicle's steering state, either the front or rear axle wheels. In other words, the target wheel is the core object of grip optimization. By specifically adjusting the center of gravity and braking force distribution, the adhesion of the target wheel is improved, thereby enhancing the vehicle's steering stability. For example, when the vehicle is understeer, the front wheels lack grip, and the target wheel is the front axle wheel; when the vehicle is oversteer, the rear wheels lack grip, and the target wheel is the rear axle wheel.

[0035] The tire model is a mathematical model describing the relationship between tire lateral force and related parameters. The peak lateral force value is the maximum lateral force parameter that the tire can provide. Specifically, the tire model is used to accurately calculate the tire's lateral force under different operating conditions, providing a basis for yaw moment balance calculations. The peak lateral force value directly determines the tire's grip capability, and by correcting this value, the tire lateral force calculation can be adapted to low-adhesion road surface conditions.

[0036] For example, the tire model can be expressed by the following formula: Fy=D×sin(C×arctan(B×λ-E×(B×λ-arctan(B×λ)))); where Fy represents the tire lateral force, B represents the stiffness factor, C represents the shape factor, D represents the peak lateral force, E represents the curve curvature factor, and λ represents the tire slip angle. When the road surface friction coefficient decreases, the peak lateral force D needs to be adjusted accordingly to match the actual grip capability.

[0037] In an optional embodiment, step S102 specifically includes the following steps: when the road surface is determined to be a low-adhesion road surface, the road surface friction coefficient is obtained in real time through the roadside communication unit, and basic parameters in the preset parameter library are retrieved; the basic parameters include the default initial threshold of the preset center of gravity adjustment coefficient, the reference value of the peak lateral force of the dry road surface, and the reference value of the friction coefficient of the dry road surface; the low-adhesion level is divided according to the road surface friction coefficient, and the preset center of gravity adjustment coefficient is corrected based on the low-adhesion level classification; wherein, the low-adhesion level is positively correlated with the reduction of the default initial threshold of the preset center of gravity adjustment coefficient; the low-adhesion level includes high-level low-adhesion, medium-level low-adhesion, and low-level low-adhesion; the peak lateral force value in the tire model corresponding to the target wheel is corrected in real time according to the ratio of the road surface friction coefficient to the reference value of the friction coefficient of the dry road surface; wherein, the peak lateral force value is determined by the reference value of the peak lateral force of the dry road surface and the ratio.

[0038] For example, the basic parameters stored in the preset parameter library can be: a default initial threshold of 0.05 for the preset center of gravity adjustment coefficient, a reference value of 8000N for the peak lateral force on dry pavement, and a reference value of 0.8 for the friction coefficient on dry pavement; the low adhesion level classification standard is: high-level low adhesion (μ≤0.2), medium-level low adhesion (0.2<μ≤0.25), and low-level low adhesion (0.25<μ≤0.3), with corresponding reductions in the preset center of gravity adjustment coefficient of 20%, 15%, and 10%, respectively; when the real-time obtained pavement friction coefficient is 0.2 (high-level low adhesion), the corrected preset center of gravity adjustment coefficient is 0.05×(1-20%)=0.04; at the same time, according to the proportional relationship 0.2 / 0.8=0.25, the corrected peak lateral force value is 8000N×0.25=2000N, that is, when μ=0.2, the D value is reduced to 25% of that on dry pavement.

[0039] In step S103, the vehicle height and center of gravity position are adjusted according to the real-time steering status of the vehicle and the corrected preset center of gravity adjustment coefficient. At the same time, the distribution of wheel braking force is adjusted to optimize the grip of the target wheel. The preset center of gravity adjustment coefficient refers to the ratio of the actual center of gravity offset to the vehicle wheelbase.

[0040] In the above steps, the real-time steering state of the vehicle refers to its deviation from the target steering trajectory during driving, including understeer and oversteer. Specifically, the real-time steering state is the core basis for determining the direction of center of gravity shift and braking force distribution strategy. Its function is to enable control measures to address steering deviation problems in a targeted manner and improve lane tracking accuracy. For example, when the vehicle is turning, if the front wheels slip outwards, causing the actual steering trajectory to deviate from the outer edge of the target trajectory, this is an understeer state; if the rear wheels slip outwards, causing the actual steering trajectory to deviate from the inner edge of the target trajectory, this is an oversteer state.

[0041] Specifically, adjusting vehicle height refers to changing the vertical distance between the vehicle body and the ground through active actuators. The purpose is to optimize wheel load distribution in conjunction with adjustments to the center of gravity. Here, adjusting vehicle height is a crucial means of optimizing vehicle posture. Its function is to indirectly adjust the longitudinal and lateral distribution of the center of gravity by changing the vertical position of the vehicle body, thereby affecting the load ratio of each wheel and improving the grip of the target wheel. For example, vehicle height adjustment can be achieved through active air suspension, with an adjustment range between -30mm and +30mm. When it is necessary to increase the load on the front axle wheels, the front height of the vehicle can be lowered by 30mm, and the rear height raised by 30mm.

[0042] Specifically, adjusting the vehicle's center of gravity refers to shifting the center of gravity longitudinally (between the front and rear axles) by changing the vehicle's posture, thereby altering the load ratio between the front and rear wheels. Adjusting the vehicle's center of gravity is the core method for improving the grip of the target wheels. Its function is to increase the load on the target wheels by shifting the center of gravity towards the axle containing them, thus enhancing their grip. For example, if the vehicle's wheelbase is 2.8m and the preset center of gravity adjustment coefficient is 0.08, then the actual center of gravity shift is 0.08 × 2.8 = 0.224m. When in understeer, shifting the center of gravity 0.224m towards the front axle increases the load on the front wheels.

[0043] Furthermore, adjusting the wheel braking force distribution involves changing the braking force of different wheels through the braking system to generate an auxiliary yaw moment to correct the vehicle's heading. Here, adjusting the wheel braking force distribution is an auxiliary means of correcting vehicle attitude. Its function is to generate a yaw moment opposite to the direction of steering deviation by applying braking force to specific wheels, thereby suppressing wheel sideslip and correcting the vehicle's heading. For example, a slight braking force with a braking torque ≤200N can be applied to the inner wheel through an electro-hydraulic braking system (EHB). m generates an auxiliary yaw moment to balance the steering deviation.

[0044] In one optional embodiment, the specific implementation process of step S103 includes: determining the real-time steering state of the vehicle by collecting vehicle steering state parameters, wherein the vehicle steering state parameters include the actual yaw rate and the vehicle sideslip angle; adjusting the vehicle height and the vehicle center of gravity position by active air suspension according to the real-time steering state of the vehicle and the corrected preset center of gravity adjustment coefficient, and adjusting the distribution of wheel braking force by electro-hydraulic braking system to optimize the grip of the target wheel; wherein the adjustment range of vehicle height is between -30mm and +30mm, and the braking torque applied by the electro-hydraulic braking system to the inner wheel does not exceed 200N·m.

[0045] For example, by collecting the vehicle's actual yaw rate and sideslip angle through the onboard inertial measurement unit (IMU), when the collected actual yaw rate is less than the target yaw rate and the sideslip angle is greater than a first preset threshold (such as 5°), it is determined to be an understeer state. At this time, the active air suspension lowers the front height of the vehicle by 20mm and raises the rear height by 20mm, causing the center of gravity to shift to the front axle. At the same time, the electro-hydraulic braking system applies a braking torque of 150 N·m to the inner rear wheel, increasing the front wheel load and generating an auxiliary yaw moment to optimize the front wheel grip.

[0046] In one optional embodiment, the vehicle steering state parameters include the actual yaw rate and the vehicle sideslip angle. The process of determining the real-time vehicle steering state further includes: when the actual yaw rate is less than the target yaw rate and the vehicle sideslip angle is greater than a first preset threshold, the real-time vehicle steering state is determined to be understeering; when the actual yaw rate is greater than the target yaw rate and the vehicle sideslip angle is greater than a second preset threshold, the real-time vehicle steering state is determined to be oversteering; wherein the second preset threshold is less than the first preset threshold.

[0047] For example, a first preset threshold can be set to 5°, a second preset threshold to 3°, and a target yaw rate of 10 rad / s. When the actual yaw rate of the vehicle is 8 rad / s (less than the target value) and the vehicle sideslip angle is 6° (greater than the first preset threshold), it can be determined as understeering. When the actual yaw rate of the vehicle is 12 rad / s (greater than the target value) and the vehicle sideslip angle is 4° (greater than the second preset threshold), it can be determined as oversteering.

[0048] In one optional embodiment, step S103 specifically includes: calculating the target center of gravity offset by multiplying the corrected preset center of gravity adjustment coefficient with the vehicle wheelbase, and determining the center of gravity offset direction according to the real-time steering state of the vehicle; wherein, in the understeer state, the center of gravity offset direction is towards the front axle of the vehicle, and in the oversteer state, the center of gravity offset direction is towards the rear axle of the vehicle; calculating the required load adjustment amount for the front and rear axles based on the target center of gravity offset and the vehicle curb weight, and calculating the lifting stroke parameters of the active air suspension in combination with the vehicle height adjustment range, the lifting stroke parameters being used to control the lifting action of the active air suspension to adjust the vehicle height and the vehicle center of gravity position; calculating the braking force distribution ratio between the target wheel and the non-target wheel in combination with the real-time vehicle speed, and calculating the braking torque applied to the inner wheel by the electro-hydraulic braking system based on the braking force distribution ratio and the preset maximum braking torque threshold, so as to adjust the wheel braking force distribution through the braking torque and optimize the grip of the target wheel.

[0049] For example, when the vehicle wheelbase is 2.8m, the corrected preset center of gravity adjustment coefficient is 0.08 in understeer, so the target center of gravity offset is 0.08 × 2.8 = 0.224m, and the center of gravity offset direction is towards the central axis; the vehicle's curb weight is 1500kg, and based on the center of gravity offset, the front axle load needs to be increased by 15% (i.e., 225kg). Combined with the vehicle height adjustment range of ±30mm, the active air suspension front axle lifting travel is calculated to be -25mm (lower) and rear axle lifting travel is +25mm (higher); the real-time vehicle speed is 60km / h, and the calculated braking force distribution ratio between the target wheel (front axle) and the non-target wheel (rear axle) is 6:4. The preset maximum braking torque threshold is 200N·m, and the final calculated braking torque applied to the inner rear wheel is 120N·m.

[0050] In step S104, after optimizing the grip of the target wheel, the tire lateral force is calculated based on the corrected peak lateral force value, and the compensation torque is calculated based on the tire lateral force and the pre-constructed yaw moment balance equation, so as to control the convergence of the vehicle system state along the preset sliding surface through the compensation torque; wherein, the vehicle system state includes the actual yaw rate and the vehicle sideslip angle, the preset sliding surface is determined by the actual yaw rate, the target yaw rate, the vehicle sideslip angle and the weighting coefficient, and the yaw moment balance equation is constructed based on the vehicle yaw moment of inertia, yaw acceleration, the distance from the front axle to the center of gravity and the distance from the rear axle to the center of gravity.

[0051] Among these, tire lateral force, the lateral force generated between the tire and the ground, is a key force parameter affecting the vehicle's yaw attitude. Optionally, tire lateral force is the core force source generating the vehicle's yaw moment. Its function is to adjust the vehicle's yaw attitude by changing the difference in lateral forces between the front and rear axles, allowing the vehicle to travel along a target trajectory. For example, the difference between the front wheel lateral force Fyf and the rear wheel lateral force Fyr will generate a yaw moment. When Fyf×a>Fyr×b, the vehicle can generate a clockwise yaw moment, which can correct oversteer.

[0052] Optionally, the yaw moment balance equation is a mathematical equation describing the yaw moment balance relationship of the vehicle, used to calculate the compensating torque required to maintain the vehicle's yaw attitude stability. The yaw moment balance equation is constructed based on vehicle dynamics principles; its function is to calculate the compensating torque required to offset attitude deviations by quantifying the yaw moment relationships generated by various forces, thus ensuring the vehicle's yaw attitude stability. For example, the yaw moment balance equation considers parameters such as the vehicle's yaw moment of inertia, yaw angular acceleration, and the distance from the front and rear axles to the center of gravity, accurately reflecting the dynamic characteristics of the vehicle's yaw motion.

[0053] Here, the compensating torque is an additional torque used to correct the vehicle's yaw attitude deviation, which can be applied to the vehicle by controlling the actuator. Specifically, the compensating torque is the core control quantity for achieving convergence of the vehicle system state along a preset sliding surface. Its function is to counteract the yaw torque deviation caused by changes in the road surface friction coefficient or steering deviation, allowing the vehicle to quickly return to a stable state. For example, when the road surface friction coefficient suddenly drops from 0.8 to 0.2, the vehicle's yaw attitude will deviate. At this time, the compensating torque ΔMz = 500N can be calculated. m, applying this torque can suppress yaw rate overshoot, with an overshoot of ≤5%.

[0054] Specifically, the preset sliding surface is an ideal motion trajectory constraint surface determined by the vehicle's actual yaw rate, target yaw rate, vehicle sideslip angle, and weighting coefficients. In other words, the preset sliding surface is a core element of sliding mode variable structure control. Its function is to set an ideal motion trajectory for the vehicle system state, and to force the system state to move along this surface by controlling the compensation torque, ultimately converging to the target state (error of 0). Furthermore, the system dynamic characteristics on the sliding surface are unaffected by the nonlinearity and disturbances of the original system. For example, the preset sliding surface is obtained by linearly combining the deviation between the vehicle's actual yaw rate and the target value, as well as the vehicle sideslip angle, ensuring simultaneous stability of the vehicle's yaw attitude and lateral position.

[0055] In one optional embodiment, step S104 specifically includes: after optimizing the grip of the target wheel, calculating the front wheel lateral force and the rear wheel lateral force according to the corrected peak lateral force value and tire slip angle; substituting the calculated front wheel lateral force and rear wheel lateral force into the pre-constructed yaw moment balance equation to calculate the basic compensation torque required to offset the current attitude deviation, the basic compensation torque being used to balance the yaw moment difference generated by the front wheel lateral force and the rear wheel lateral force; substituting the collected actual vehicle yaw rate and vehicle slip angle into the preset sliding surface formula to calculate the system state deviation value; adjusting the basic compensation torque according to the system state deviation value to obtain the final compensation torque, so as to correct the vehicle yaw attitude through the compensation torque, so that the vehicle system state converges along the preset sliding surface and maintains lane stability.

[0056] For example, given a corrected peak lateral force D = 2000 N, and the collected front wheel slip angle λf = 3° and rear wheel slip angle λr = 2°, substituting these values ​​into the tire model's formula yields a front wheel lateral force Fyf = 1800 N and a rear wheel lateral force Fyr = 1500 N. The vehicle's yaw moment of inertia is Iz = 2000 kg·m², yaw acceleration is rz = 0.5 rad / s², the distance from the front axle to the center of gravity is a = 1.2 m, and the distance from the rear axle to the center of gravity is b = 1.6 m. Substituting these values ​​into the yaw moment balance equation Iz × rz = Fy The basic compensation torque ΔMz_base is calculated as f×a-Fyr×b+ΔMz = 2000×0.5-(1800×1.2-1500×1.6) = 1000-(2160-2400) = 1240 N·m. Substituting the actual yaw rate ω = 8 rad / s, the target yaw rate ω_d = 10 rad / s, the vehicle sideslip angle β = 6°, and the weighting coefficient k = 0.5 into the preset sliding surface formula, the system state deviation value s = 8-10+0.5×6 = 1 is calculated. Finally, the basic compensation torque is adjusted according to the system state deviation value s, and the final compensation torque ΔMz=1240×(1+0.1×s)=1364N·m is obtained. After applying this torque, the vehicle system state gradually converges to the sliding surface, and the yaw rate and vehicle sideslip angle return to the target values.

[0057] For example, the preset sliding surface formula includes: s=ω-ω_d+k×β, where s represents the sliding surface, ω represents the actual yaw rate of the vehicle, ω_d represents the target yaw rate, β represents the vehicle sideslip angle, and k represents the weighting coefficient; the yaw moment balance equation is calculated using the following formula: Iz×rz=Fyf×a-Fyr×b+ΔMz, where Iz represents the vehicle's yaw moment of inertia, rz represents the yaw acceleration, a represents the distance from the front axle to the center of gravity, b represents the distance from the rear axle to the center of gravity, Fyf represents the lateral force of the front wheels, Fyr represents the lateral force of the rear wheels, and ΔMz represents the compensation torque.

[0058] For example, with a weighting coefficient k=0.5, when the actual yaw rate ω=9rad / s, the target yaw rate ω_d=10rad / s, and the vehicle sideslip angle β=4°, the sliding surface s=9-10+0.5×4=1; for a certain vehicle, Iz=2200kg·m², rz=0.4rad / s², a=1.3m, b=1.5m, Fyf=1700N, Fyr=1400N, substituting into the yaw moment balance equation, we can get 2200×0.4=1700×1.3-1400×1.5+ΔMz, and calculate ΔMz=880-(2210-2100)=770N·m.

[0059] In this embodiment, the compensating torque is applied by an actuator to correct the vehicle's yaw attitude. After the compensating torque is applied, the system state quickly converges to the sliding surface, which can suppress yaw rate overshoot (overshoot ≤5%), and ultimately control the vehicle's lateral offset within ±0.2m, achieving high-precision lane tracking.

[0060] Based on the same inventive concept, this application also provides a lane keeping control device for low-adhesion road surfaces, which corresponds to the lane keeping control method for low-adhesion road surfaces. Since the principle of the device in this application is similar to the lane keeping control method for low-adhesion road surfaces described above, the implementation of the device can refer to the implementation of the method, and the repeated parts will not be described again.

[0061] Please see Figure 2 , Figure 2 This is a schematic diagram of a lane keeping control device for low-adhesion road surfaces provided in an embodiment of this application. Figure 2 As shown, the device 200 includes: The road surface judgment module 201 is used to calculate the wheel slip ratio based on the obtained wheel angular velocity and vehicle speed, so as to determine whether the road surface is a low-adhesion road surface based on the wheel slip ratio, wherein the road surface friction coefficient of the low-adhesion road surface is less than or equal to a preset friction threshold. The numerical correction module 202 is used to correct the preset center of gravity adjustment coefficient based on the real-time obtained road friction coefficient when the road surface is determined to be a low-adhesion road surface, and at the same time correct the peak lateral force value in the tire model corresponding to the target wheel. The grip optimization module 203 is used to adjust the vehicle height and the vehicle center of gravity position according to the real-time steering status of the vehicle and the corrected preset center of gravity adjustment coefficient, and at the same time adjust the distribution of wheel braking force to optimize the grip of the target wheel; wherein, the preset center of gravity adjustment coefficient refers to the ratio of the actual center of gravity offset to the vehicle wheelbase. The sliding mode control module 204 is used to calculate the tire lateral force based on the corrected peak lateral force value after optimizing the grip of the target wheel, and to calculate the compensation torque based on the tire lateral force and the pre-constructed yaw moment balance equation, so as to control the vehicle system state to converge along the preset sliding surface through the compensation torque; wherein, the preset sliding surface is determined by the actual yaw rate of the vehicle, the target yaw rate, the vehicle sideslip angle and the weighting coefficient, and the yaw moment balance equation is constructed based on the vehicle yaw moment of inertia, yaw acceleration, the distance from the front axle to the center of gravity and the distance from the rear axle to the center of gravity.

[0062] The device provided in this application effectively solves the problem of oversteering or understeering caused by insufficient tire grip on low-adhesion road surfaces (ice, snow, water, friction coefficient μ≤0.3) in traditional lane keeping technology. It controls the lateral deviation within a small range, significantly improves the lane keeping effect, and increases driving safety.

[0063] Please see Figure 3 , Figure 3 This is a schematic diagram of the structure of an electronic device provided in an embodiment of this application. Figure 3 As shown, the electronic device 300 includes a processor 310, a memory 320, and a bus 330.

[0064] The memory 320 stores machine-readable instructions executable by the processor 310. When the electronic device 300 is running, the processor 310 and the memory 320 communicate via the bus 330. When the machine-readable instructions are executed by the processor 310, they can perform the operations described above. Figure 1 The specific implementation of the lane keeping control method for low-adhesion road surfaces in the illustrated method embodiment can be found in the method embodiment, and will not be repeated here.

[0065] This application also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, can perform the above-described actions. Figure 1 The specific implementation of the lane keeping control method for low-adhesion road surfaces in the illustrated method embodiment can be found in the method embodiment, and will not be repeated here.

[0066] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0067] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. The apparatus embodiments described above are merely illustrative. For example, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. Furthermore, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Additionally, the shown or discussed mutual couplings, direct couplings, or communication connections may be through some communication interfaces; indirect couplings or communication connections between devices or units may be electrical, mechanical, or other forms.

[0068] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0069] In addition, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0070] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a processor-executable, non-volatile, computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0071] Finally, it should be noted that the above-described embodiments are merely specific implementations of this application, used to illustrate the technical solutions of this application, and not to limit them. The scope of protection of this application is not limited thereto. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features, within the scope of the technology disclosed in this application. Such modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A lane keeping control method for a low adhesion road, characterized by, The method comprises the following steps: calculating the wheel slip ratio according to the obtained wheel angular velocity and vehicle running speed, to determine whether the road surface is a low adhesion road surface according to the wheel slip ratio, wherein the road surface friction coefficient of the low adhesion road surface is less than or equal to a preset friction threshold value; when it is determined that the road surface is a low adhesion road surface, correcting the preset gravity center adjustment coefficient according to the real-time obtained road surface friction coefficient, and simultaneously correcting the peak lateral force value in the tire model corresponding to the target wheel; adjusting the vehicle body height and the vehicle gravity center position according to the real-time steering state of the vehicle and the corrected preset gravity center adjustment coefficient, and simultaneously adjusting the distribution of the wheel braking force, so as to optimize the grip force of the target wheel; wherein the preset gravity center adjustment coefficient refers to the ratio of the actual gravity center offset amount to the vehicle wheelbase; after the grip force of the target wheel is optimized, calculating the tire lateral force according to the corrected peak lateral force value, and calculating the compensation moment according to the tire lateral force and the pre-constructed yaw moment balance equation, so as to control the vehicle system state to converge along the preset sliding mode surface through the compensation moment; wherein the preset sliding mode surface is determined by the actual yaw angular velocity of the vehicle, the target yaw angular velocity, the vehicle side slip angle and the weight coefficient, and the yaw moment balance equation is constructed based on the vehicle yaw moment of inertia, the yaw angular acceleration, the distance from the front axle to the gravity center and the distance from the rear axle to the gravity center.

2. The method of claim 1, wherein, The method comprises the following steps: calculating the wheel slip ratio according to the obtained wheel angular velocity and vehicle running speed, to determine whether the road surface is a low adhesion road surface according to the wheel slip ratio, wherein the road surface friction coefficient of the low adhesion road surface is less than or equal to a preset friction threshold value; calculating the product of the wheel angular velocity and the wheel radius to obtain the rolling linear speed of the wheel; calculating the ratio of the difference between the rolling linear speed and the vehicle running speed to the vehicle running speed to obtain the wheel slip ratio; 3. The method of claim 1, wherein, if the wheel slip ratio is greater than or equal to a preset slip ratio threshold value, it is determined that the road surface is a low adhesion road surface. The method comprises the following steps: when it is determined that the road surface is a low adhesion road surface, the preset gravity center adjustment coefficient is corrected according to the real-time obtained road surface friction coefficient, and simultaneously the peak lateral force value in the tire model corresponding to the target wheel is corrected. when it is determined that the road surface is a low adhesion road surface, the road surface friction coefficient is obtained in real time through a roadside communication unit, and the basic parameters in a preset parameter library are called; the basic parameters include the default initial threshold value of the preset gravity center adjustment coefficient, the dry road surface peak lateral force reference value and the dry road surface friction coefficient reference value; the low adhesion level is divided according to the road surface friction coefficient, and the preset gravity center adjustment coefficient is graded corrected based on the low adhesion level; wherein the low adhesion level and the default initial threshold value of the preset gravity center adjustment coefficient have a positive correlation relationship; the low adhesion level includes high-grade low adhesion, medium-grade low adhesion and low-grade low adhesion; the peak lateral force value in the tire model corresponding to the target wheel is corrected in real time according to the proportional relationship between the road surface friction coefficient and the dry road surface friction coefficient reference value; wherein the peak lateral force value is determined by the dry road surface peak lateral force reference value and the proportional relationship.

4. The method of claim 1, wherein, The vehicle body height and the vehicle gravity center position are adjusted according to the real-time steering state of the vehicle and the adjusted preset gravity center adjustment coefficient, and the distribution of the wheel braking force is adjusted to optimize the grip of the target wheel, comprising: The real-time steering state of the vehicle is determined by collecting the vehicle steering state parameters, wherein the real-time steering state of the vehicle includes understeering state or oversteering state; The vehicle body height and the vehicle gravity center position are adjusted by the active air suspension according to the real-time steering state of the vehicle and the adjusted preset gravity center adjustment coefficient, and the distribution of the wheel braking force is adjusted by the electronic hydraulic braking system to optimize the grip of the target wheel; wherein the adjustment range of the vehicle body height is between-30mm and +30mm, and the braking torque applied to the inner wheel by the electronic hydraulic braking system is not more than 200N·m.

5. The method of claim 4, wherein, The vehicle steering state parameters include actual yaw rate and vehicle side slip angle, and the real-time steering state of the vehicle is determined by collecting the vehicle steering state parameters, comprising: When the actual yaw rate is less than the target yaw rate and the vehicle side slip angle is greater than the first preset threshold, it is determined that the real-time steering state of the vehicle is understeering state; When the actual yaw rate is greater than the target yaw rate and the vehicle side slip angle is greater than the second preset threshold, it is determined that the real-time steering state of the vehicle is oversteering state; wherein the second preset threshold is less than the first preset threshold.

6. The method of claim 5, wherein, The vehicle body height and the vehicle gravity center position are adjusted by the active air suspension according to the real-time steering state of the vehicle and the adjusted preset gravity center adjustment coefficient, and the distribution of the wheel braking force is adjusted by the electronic hydraulic braking system to optimize the grip of the target wheel, comprising: The target gravity center offset is calculated based on the product of the adjusted preset gravity center adjustment coefficient and the wheelbase, and the gravity center offset direction is determined according to the real-time steering state of the vehicle; wherein in the understeering state, the gravity center offset direction is towards the front axle of the vehicle, and in the oversteering state, the gravity center offset direction is towards the rear axle of the vehicle; The load adjustment amount required for the front and rear axles is calculated according to the target gravity center offset and the vehicle kerb mass, and the lifting stroke parameter of the active air suspension is calculated in combination with the adjustment range of the vehicle body height, which is used to control the lifting action of the active air suspension to adjust the vehicle body height and the vehicle gravity center position; In combination with the real-time vehicle speed, the braking force distribution ratio of the target wheel and the non-target wheel is calculated, and the braking torque applied to the inner wheel by the electronic hydraulic braking system is calculated according to the braking force distribution ratio and the preset maximum braking torque threshold, so as to adjust the distribution of the wheel braking force by the braking torque to optimize the grip of the target wheel.

7. The method of claim 1, wherein, After the grip of the target wheel is optimized, the tire lateral force is calculated according to the adjusted peak lateral force value, and the compensation torque is calculated according to the tire lateral force and the pre-constructed yaw moment balance equation, so as to control the vehicle system state to converge along the preset sliding mode surface by the compensation torque, comprising: After the grip of the target wheel is optimized, the front wheel side force and the rear wheel side force are calculated according to the tire side slip angle of the corrected peak side force value; The calculated front wheel side force and rear wheel side force are substituted into the pre-constructed yaw moment balance equation to calculate a basic compensation moment required to offset the current attitude deviation, and the basic compensation moment is used to balance the yaw moment difference generated by the front wheel side force and the rear wheel side force; The collected actual yaw rate of the vehicle and the vehicle side slip angle are substituted into the preset sliding mode surface formula to calculate a system state deviation value; The basic compensation moment is adjusted according to the system state deviation value to obtain a final compensation moment, so as to correct the vehicle yaw attitude through the compensation moment, so that the vehicle system state converges along the preset sliding mode surface and maintains lane stability.

8. The method of claim 7, wherein, The preset sliding mode surface formula includes: s = ω - ω_d + k × β Wherein, s represents the sliding mode surface, ω represents the actual yaw rate of the vehicle, ω_d represents the target yaw rate, β represents the vehicle side slip angle, and k represents the weight coefficient; And, the yaw moment balance equation is calculated by the following formula: Iz × rz = Fyf × a - Fyr × b + ΔMz Wherein, Iz represents the yaw moment of inertia of the vehicle, rz represents the yaw angular acceleration, a represents the distance from the front axle to the center of gravity, b represents the distance from the rear axle to the center of gravity, Fyf represents the front wheel side force, Fyr represents the rear wheel side force, and ΔMz represents the compensation moment.

9. The method of claim 1, wherein, The tire model is represented by the following formula: Fy = D × sin(C × arctan(B × λ - E × (B × λ - arctan(B × λ))) Wherein, Fy represents the tire side force, B represents the stiffness factor, C represents the shape factor, D represents the peak side force, E represents the curve curvature factor, and λ represents the tire side slip angle.

10. A lane keeping control device for a low adhesion road, characterized by It includes: A road surface judgment module for calculating the wheel slip ratio according to the obtained wheel angular velocity and vehicle speed, so as to judge whether the road surface is a low adhesion road surface according to the wheel slip ratio, wherein the road surface friction coefficient of the low adhesion road surface is less than or equal to a preset friction threshold; A numerical correction module for correcting the preset gravity adjustment coefficient according to the real-time obtained road surface friction coefficient when it is judged that the road surface is a low adhesion road surface, and simultaneously correcting the peak side force value in the tire model corresponding to the target wheel; A grip optimization module for adjusting the vehicle body height and the vehicle gravity center position according to the real-time steering state of the vehicle and the corrected preset gravity adjustment coefficient, and simultaneously adjusting the distribution of the wheel braking force, so as to optimize the grip of the target wheel; wherein the preset gravity adjustment coefficient refers to the ratio of the actual gravity center offset amount to the wheelbase of the vehicle. The slip mode control module is used to calculate the tire lateral force according to the corrected peak lateral force value after the target wheel's grip force is optimized, and to calculate the compensation moment according to the tire lateral force and a pre-constructed yaw moment balance equation, so as to control the vehicle system state to converge along a preset slip mode surface through the compensation moment; wherein the preset slip mode surface is determined by the actual yaw angular velocity of the vehicle, the target yaw angular velocity, the vehicle side slip angle and the weight coefficient, and the yaw moment balance equation is constructed based on the vehicle yaw moment of inertia, the yaw angular acceleration, the distance from the front axle to the center of gravity and the distance from the rear axle to the center of gravity.

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