A four-wheel drive electric vehicle reduces tire wear steering coordination control method

Abstract

The application discloses a kind of four-wheel drive electric vehicle reduces the steering coordination control method of tire wear, belong to vehicle steering control technical field.This method real-time acquisition steering wheel angle, speed, wheel speed, vertical load, tire history partial wear characteristics and four-wheel alignment real-time parameters;Based on the correction Ackerman steering model, the theoretical target wheel speed of each wheel is calculated, and the real-time slip rate is obtained by comparing the actual wheel speed;With the minimum tire slip power loss as the goal, the four-wheel drive torque is distributed and corrected in combination with the vertical load and partial wear characteristics, and a penalty coefficient is applied to the partial wear tire to reduce the load;Finally, the driven wheel speed converges to the theoretical target, maintaining the pure rolling state.The application simultaneously introduces toe and camber parameter dynamic correction steering model, designs full-condition torque protection strategy for partial wear tire, suppresses implicit slip and partial wear aggravation from the root, significantly prolongs tire service life, and improves steering control precision and driving economy.

Description

Technical Field

[0001] This invention relates to the field of steering coordination control technology for four-wheel drive electric vehicles, and particularly to a steering coordination control method for reducing tire wear in four-wheel drive electric vehicles. Background Technology

[0002] As the global automotive industry accelerates its transformation towards electrification and intelligentization, four-wheel-drive electric vehicles have become the mainstream due to their advantages of independent drive and precise torque response. However, their tire wear problem is more prominent than that of traditional vehicles. In addition to the large curb weight, the instantaneous torque impact of the motor, and the wear exacerbated by regenerative braking, the tire wear problem of four-wheel-drive electric vehicles is more complex under steering conditions, with hidden factors that are overlooked by current technology.

[0003] On the one hand, the asymmetric amplification effect of historical tire wear patterns on steering wear occurs in four-wheel drive electric vehicles. Due to manufacturing tolerances, uneven suspension stress, or lack of tire rotation over a long period, the four wheels often exhibit varying degrees of uneven wear (e.g., heavier wear on the inner side than the outer side, or unilateral tire shoulder wear). Existing steering coordination control methods assume an ideal state of uniform wear for all four wheels, failing to identify and provide special protection for unevenly worn tires. During steering, if severely worn tires are assigned the same driving torque or bear the same lateral force as normal tires, their wear rate will increase exponentially. On the other hand, the distortion of theoretical models caused by real-time drift of four-wheel alignment parameters leads to deviations in parameters such as toe angle and camber angle from factory calibration after long-term driving. Existing technologies based on Ackermann steering geometry rely on standard vehicle geometry parameters (fixed track width, fixed wheelbase, standard steering trapezoid), failing to consider the deviations in steering radius and wheel trajectory caused by real-time changes in suspension parameters. When a vehicle turns under abnormal suspension parameters, even if the wheel speed sensor shows no slippage, the tires are actually in a subtle state of lateral slippage or longitudinal drag. This hidden sliding friction cannot be identified by the existing slip ratio calculation formula, but it continues to cause abnormal tire wear. Summary of the Invention

[0004] In view of this, the present invention proposes a steering coordination control method for reducing tire wear in four-wheel drive electric vehicles. Based on the steering coordination control technology of four-wheel independent drive, the method achieves rolling friction between the wheels and the road surface instead of sliding friction by precisely controlling the output torque of each drive motor and cooperating with the active steering system, thereby reducing tire wear under steering conditions while ensuring steering flexibility.

[0005] The technical solution of this invention is implemented as follows:

[0006] A steering coordination control method for reducing tire wear in a four-wheel drive electric vehicle includes the following steps:

[0007] Step S1: Collect vehicle driving status data in real time. The driving status data includes at least the steering wheel angle signal, vehicle speed signal, wheel speed signal of each wheel, vertical load signal of each wheel, yaw rate signal of the whole vehicle, historical wear characteristic parameters of each tire, and real-time parameters of four-wheel alignment.

[0008] Step S2: Based on the steering wheel angle signal and vehicle speed signal, and using the Ackerman steering geometry model combined with the vehicle geometry model corrected by the real-time parameters of the four-wheel alignment, calculate the theoretical target wheel speed of each wheel under the current steering condition.

[0009] Step S3: Compare the actual wheel speeds of each wheel with the corresponding theoretical target wheel speeds to calculate the real-time slip ratio of each wheel;

[0010] Step S4: When the real-time slip ratio of any wheel exceeds the preset slip ratio threshold, the torque distribution correction of the four-wheel independent drive motor is calculated with the objective function of minimizing tire slip power loss, combined with the vertical load signal of each wheel and the historical wear characteristic parameters. Among them, the wheel with wear mark is penalized by a penalty coefficient during torque distribution to reduce its load.

[0011] Step S5: Generate a target torque command based on the torque distribution correction amount and send it to each wheel hub motor controller. By adjusting the driving torque of the inner and outer wheels, the actual wheel speed converges to the theoretical target wheel speed, maintaining the pure rolling friction state between the tire and the ground.

[0012] Preferably, in step S1, the method for obtaining the historical wear characteristic parameters is as follows:

[0013] By using a tread scanning sensor installed inside the wheel arch or a wear estimation model based on historical vehicle driving data, the residual tread depth of each tire on the inner, middle, and outer sides is obtained, and the difference in tread depth between the inner and outer sides is calculated. and the difference in tread depth between the shoulder and the center of the tire. ,like Exceeding the preset outward wear threshold or If the wear exceeds the preset toe-in wear threshold, the tire is marked as an uneven wear tire, and the uneven wear type and severity level are recorded.

[0014] Preferably, in step S4, the introduced tire wear factor weighting coefficient The calculation formula is revised as follows:

[0015]

[0016] in, The wear penalty factor is determined based on the severity level of the historical wear characteristic parameters, and its value range is [value range missing]. The more severe the uneven wear, The larger the value; The weighting coefficient for the wear penalty is introduced; When distributing steering torque, it actively reduces the force priority of unevenly worn tires to prevent them from wearing out further.

[0017] Preferably, in step S1, the real-time parameters for four-wheel alignment include at least the front wheel toe angle. Front wheel camber angle The four-wheel alignment parameters are collected in real time by high-precision angle sensors installed on the suspension links or steering knuckles, or by reading the online four-wheel alignment estimates from the electronic control unit based on the fusion of wheel speed and inertial measurement unit data via the vehicle bus.

[0018] Preferably, in step S2, the specific method for correcting the Ackermann steering geometry model based on the real-time parameters of the four-wheel alignment is as follows:

[0019] When the front wheel toe angle is detected When the angle exceeds the preset standard range, an equivalent angle correction is introduced. ,in This is the toe-influence coefficient; when the camber angle is detected... When the value exceeds the preset standard range, a tire lateral stiffness correction coefficient is introduced. ,in The camber wear sensitivity coefficient is used to substitute the corrected equivalent steering angle and the corrected tire lateral stiffness into the theoretical target wheel speed calculation model to eliminate the trajectory deviation caused by the drift of the four-wheel alignment parameters.

[0020] Preferably, it also includes four-wheel alignment abnormality warning and torque limiting protection steps:

[0021] When the real-time parameters of the four-wheel alignment are determined to exceed the preset safety threshold range, a four-wheel alignment abnormality warning signal is output to prompt the driver to inspect and repair; at the same time, during the steering process, the maximum driving torque of all wheels is limited to no more than 70% of the rated torque, and regenerative braking is used first to decelerate in order to reduce the tire wear rate under abnormal alignment conditions.

[0022] Preferably, it also includes a periodic self-inspection step for tires with uneven wear:

[0023] Each time the vehicle performs a self-test upon power-on or when the accumulated mileage reaches a preset interval, the historical wear characteristic parameter detection in step S1 is executed; if a new tire with uneven wear is detected or the wear level changes, the wear mark and penalty factor are updated. And store it in non-volatile memory.

[0024] Preferably, step S4 further includes:

[0025] When the vehicle speed is lower than the preset low speed threshold and the steering wheel angle is greater than the preset large steering angle threshold, the vehicle is determined to be in a low speed and large steering angle condition, and the system switches to the electronic differential assist steering mode. In this mode, it first determines whether the inner rear wheel is the tire with uneven wear. If so, the negative torque braking command of the inner rear wheel is transferred to the front wheel on the same side, or the negative torque amplitude is reduced to protect the tire with uneven wear.

[0026] Preferably, it also includes a deceleration and steering coordination control step:

[0027] When a brake pedal opening signal is detected and the steering wheel angle is non-zero, the road adhesion limit is estimated by combining the vertical load of each wheel. When distributing regenerative braking torque, if the rear wheel is marked as an unevenly worn tire, the regenerative braking torque of the rear wheel is further limited to no more than 50% of the road adhesion limit threshold estimated based on the vertical load, and the reduced braking torque is transferred to the front axle or the coaxial non-unevenly worn tire.

[0028] Preferably, it also includes a feedback correction step:

[0029] The system monitors the rate of change of wheel slip ratio after torque distribution correction in real time. If the slip ratio does not converge to below a threshold value within a preset adjustment period, an adaptive gain adjustment mechanism is triggered to dynamically increase the weighting coefficient of the wear factor. In If the slip ratio still fails to converge after multiple gain adjustments, and the wheel is marked as an unevenly worn tire, then it is determined that the current uneven wear condition has seriously affected the vehicle's dynamic control, and the speed limit protection mode is activated.

[0030] Compared with the prior art, the beneficial effects of the present invention are:

[0031] 1. By introducing historical wear characteristic parameters and real-time four-wheel alignment parameters, the steering cooperative control model is upgraded from the traditional ideal vehicle model to a real physical state perception model. By applying a torque penalty coefficient to the wear-prone tires, the high voltage strong grounding in the wear-prone area is actively avoided during steering distribution, which effectively curbs the broken window effect, i.e. the problem that the wear rate of the wear-prone tires deteriorates exponentially under steering conditions, and can significantly extend the average service life of the entire tire group.

[0032] 2. By monitoring four-wheel alignment parameters in real time, the equivalent steering angle and lateral stiffness in the Ackermann steering geometry model are dynamically corrected, eliminating implicit trajectory deviations caused by suspension aging and bushing deformation. This correction mechanism makes the calculation of the theoretical target wheel speed closer to the actual kinematic relationship of the vehicle, fundamentally reducing the continuous micro-slip caused by model errors, and further improving the accuracy of steering coordination control and tire protection effect;

[0033] 3. In both low-speed, high-angle driving conditions and deceleration energy recovery conditions, this invention sets up differentiated protection logic (such as negative torque transfer and differentiated regenerative braking limits) for tires with uneven wear, achieving balanced tire life management covering all working conditions and avoiding the economic loss of replacing all four tires at the same time due to excessive wear of a single tire. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only preferred embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 A flowchart of a steering coordination control method for reducing tire wear in a four-wheel drive electric vehicle according to the present invention;

[0036] Figure 2 This is a logic block diagram of torque distribution correction for a steering coordination control method to reduce tire wear in a four-wheel drive electric vehicle according to the present invention.

[0037] Figure 3 This is a schematic diagram of the hardware system structure of the present invention;

[0038] Reference numerals: 1. Hub motor; 2. Vehicle controller; 3. Steering wheel angle sensor; 4. Wheel speed sensor; 5. Suspension load strain gauge; 6. Inertial measurement unit; 7. Tire tread scanning sensor; 8. Suspension angle sensor; 9. Brake pedal position sensor; 10. CAN bus; 11. Motor controller; 12. Instrument panel. Detailed Implementation

[0039] To better understand the technical content of this invention, a specific embodiment is provided below, and the invention will be further described in conjunction with the accompanying drawings.

[0040] See Figure 1 , Figure 1 A flowchart of a steering coordination control method for reducing tire wear in a four-wheel drive electric vehicle, provided as an embodiment of the present invention.

[0041] This invention provides a steering coordination control method for reducing tire wear in a four-wheel drive electric vehicle, comprising:

[0042] Step S1: Collect vehicle driving status data in real time. The driving status data includes at least the steering wheel angle signal, vehicle speed signal, wheel speed signal of each wheel, vertical load signal of each wheel, yaw rate signal of the whole vehicle, historical wear characteristic parameters of each tire, and real-time parameters of four-wheel alignment.

[0043] In this embodiment, the four-wheel drive electric vehicle is equipped with four hub motors 1, a steering wheel angle sensor 3, a wheel speed sensor 4, a suspension load strain gauge 5, and a newly added tire tread laser scanning module and a suspension angle sensor 8.

[0044] Tire wear characteristic parameters acquisition:

[0045] With the vehicle stationary and the tires cool, a miniature laser profilometer installed in the wheel arch performs a lateral scan of the tire tread to obtain the residual tread depth at three locations: the inner, middle, and outer sides of the tread. , , .calculate If the difference is greater than 1.5mm, it is determined to be uneven wear caused by abnormal camber angle; calculation If the wear exceeds 1.2mm, it is considered feather wear caused by abnormal toe-in. (Wear level) Based on the percentage of deviations, it is divided into Level 1 (mild), Level 2 (moderate), and Level 3 (severe); uneven wear penalty factor. Take values ​​of 0.2, 0.5, and 0.8 respectively.

[0046] Real-time parameter acquisition for four-wheel alignment:

[0047] During vehicle operation, an angle encoder installed at the connection between the lower control arm and the steering knuckle of the front suspension measures the camber angle of the front wheels in real time. and front wheel toe angle The Vehicle Controller Unit 2 (VCU) reads this value at a frequency of 10Hz. When Exceeding the factory standard range At that time, the Ackermann corner correction logic is activated.

[0048] Step S2: Based on the steering wheel angle signal and vehicle speed signal, and using the Ackerman steering geometry model combined with the vehicle geometry model corrected by the real-time parameters of the four-wheel alignment, calculate the theoretical target wheel speed of each wheel under the current steering condition.

[0049] Step S3: Compare the actual wheel speeds of each wheel with the corresponding theoretical target wheel speeds to calculate the real-time slip ratio of each wheel.

[0050] Step S4: When the real-time slip ratio of any wheel exceeds the preset slip ratio threshold, the torque distribution correction of the four-wheel independent drive motor is calculated with the objective function of minimizing tire slip power loss, combined with the vertical load signal of each wheel and the historical wear characteristic parameters. Among them, the wheel with wear mark is penalized by a penalty coefficient during torque distribution to reduce its load.

[0051] Step S5: Generate a target torque command based on the torque distribution correction amount and send it to the controller of each wheel hub motor 1. By adjusting the driving torque of the inner and outer wheels, the actual wheel speed is made to converge to the theoretical target wheel speed, thus maintaining the pure rolling friction state between the tire and the ground.

[0052] Steering collaborative control process:

[0053] In this embodiment, the vehicle makes a 90-degree left turn at a speed of 20 km / h. Under this condition, the vehicle control unit 2 (VCU) retrieves the stored data from the previous self-test cycle and identifies that the left rear wheel has been marked as a level 2 uneven wear tire, with the corresponding uneven wear penalty factor ( During steering, the left rear wheel experiences a decrease in vertical load due to load transfer, leading to a tendency to slip. Traditional control systems would slightly reduce torque. This invention, when calculating torque distribution, takes into account... The function, The value was increased by an additional 0.5, resulting in a reduction of approximately 20% in torque on the left rear wheel compared to when uneven wear was not considered. The reduced torque was distributed to the right rear wheel and the left front wheel. Simultaneously, a positive deviation of 0.15° in the front wheel toe angle was detected. The Vehicle Control Unit (VCU) corrected the theoretical turning radius calculation, slightly reducing the target speed of the left front wheel. This prevented lateral slippage of the front wheels due to excessive toe-in, further reducing the risk of abnormal tire wear.

[0054] Preferably, in step S1, the method for obtaining the historical wear characteristic parameters is as follows:

[0055] The residual tread depth of each tire is obtained from the inner, middle, and outer sides of the tread using a tread scanning sensor 7 installed inside the wheel arch or a wear estimation model based on historical vehicle driving data. The difference in tread depth between the inner and outer sides is then calculated. and the difference in tread depth between the shoulder and the center of the tire. ,like Exceeding the preset outward wear threshold or If the wear exceeds the preset toe-in wear threshold, the tire is marked as an uneven wear tire, and the uneven wear type and severity level are recorded.

[0056] See hardware system architecture diagram Figure 3In this embodiment, tire tread scanning sensors 7 are installed on the inner sides of the four wheel arches of the vehicle. These sensors employ a miniature line laser profilometer or a high-resolution ultrasonic ranging array, and are installed at the top of the wheel arch directly opposite the center of the tire tread. The effective scanning width covers the entire width of the tire tread (i.e., from the inner shoulder to the outer shoulder). The sensors operate in the invisible infrared or ultrasonic wave band, unaffected by ambient light or tire surface contamination, and have a sampling resolution of at least 0.1 mm. Furthermore, the vehicle is equipped with one of the following: non-volatile memory, on-board EEPROM, or cloud data storage unit, to record historical wear data, uneven wear marking status, and uneven wear severity levels for each tire.

[0057] During each power-on self-test phase of the vehicle, or when the vehicle's cumulative mileage reaches a preset interval (set to 500km) and the vehicle is stationary at zero speed, the tire tread scanning sensor 7 is activated to perform a complete tire tread scan. The specific scanning process is as follows:

[0058] S11. Ensure the vehicle is on a level surface and the parking brake is locked.

[0059] S12. The scanning sensor inside the wheel arch emits a set of linear detection signals along the lateral direction of the tire (perpendicular to the rolling direction), covering the entire tread area from the inner shoulder to the outer shoulder.

[0060] S13. The sensor receives the reflected signal and calculates the residual tread depth at each lateral position point on the tire tread using the time-of-flight method or triangulation method.

[0061] S14. The data processing unit performs the above-mentioned lateral scan at three equally spaced angular positions (0°, 120°, 240°) along the tire circumference, and takes the average value of the three scan results to eliminate interference caused by local abnormal wear or stones.

[0062] For each tire, based on the tread lateral depth distribution curve obtained from scanning, the residual tread depth values ​​at the following three key locations are extracted: inner region depth: the average depth 10 mm inward from the inner shoulder edge; middle region depth: the average depth at the tread geometric center line; outer region depth: the average depth 10 mm inward from the outer shoulder edge. The selection of these three locations is based on tire contact patch mechanical analysis. The inner and outer regions correspond to the main action areas of abnormal camber wear and steering lateral force wear, respectively; the middle region corresponds to the reference area for normal rolling wear. Based on the above characteristic values, the following two wear symmetry judgment indicators are calculated:

[0063] Difference in pattern depth between inner and outer sides :

[0064]

[0065] This indicator is used to detect unilateral wear caused by abnormal camber angle. When the wheel camber angle deviates from the design value, the tire contact pressure concentrates on one side, causing the inner or outer side to wear significantly faster than the opposite side. The greater the difference in depth between the inner and outer sides, the more severe the abnormal camber wear.

[0066] Difference in tread depth between the shoulder and center of the tire on one side :

[0067]

[0068] This indicator is used to detect feathering or sawtooth wear on the tire shoulder caused by abnormal toe angle. Toe angle deviation causes the tire to generate a continuous lateral slip component during rolling, resulting in scraping wear between the tire shoulder area and the ground, causing the tread depth on the shoulder to be significantly lower than that in the center.

[0069] The system has preset empirically calibrated wear thresholds. In this embodiment, the outward tilt wear threshold is... Toe wear threshold The decision logic is: if > Then it is determined that the tire has camber wear, and the wear type is recorded as "Camber_Wear"; if > If the tire is determined to have uneven wear (toe-in), the wear type is recorded as "Toe_Wear". If both types of uneven wear exist simultaneously, the wear type is recorded as "Mixed_Wear". For tires determined to have uneven wear, the severity level is further classified according to the extent to which the difference exceeds the threshold. This embodiment uses a three-level classification: And the wear-off penalty factor At that time, the severity level was 1 (mild); And the wear-off penalty factor At that time, the severity level was 2 (moderate); And the wear-off penalty factor At this time, the severity level is 3 (severe). A similar interval mapping rule is used for classifying anterior toe wear. For mixed-type toe wear, the higher penalty factor value of the two criteria is used.

[0070] For economy vehicles that are not equipped with tire tread scanning sensor 7, this embodiment provides a wear estimation model based on historical vehicle driving data as an alternative. The model takes into account the following parameters: the cumulative driving energy of each wheel (obtained by integration by motor controller 11), the cumulative braking energy of each wheel (including the distribution ratio of regenerative braking and mechanical braking), the estimated value of the cumulative lateral force work done by each wheel under steering conditions (calculated from historical data of lateral acceleration and vertical load), and the historical average values ​​of ambient temperature and tire pressure.

[0071] The model uses a pre-calibrated tire wear rate lookup table function to output estimated values ​​of residual tread depth for each region of the tire tread. Because the estimation accuracy is lower than direct scanning measurement, the corresponding wear threshold... and The tolerances were relaxed to 2.0mm and 1.6mm respectively to reduce the probability of misjudgment. (Wearing penalty factor) The calculation still follows the above mapping relationship.

[0072] Each tire's uneven wear indicator, uneven wear type, and severity level are stored in the vehicle's non-volatile memory and bound to the tire's ID code, which uses a TPMS sensor ID. When a tire is rotated or replaced, the system resets the uneven wear data in the corresponding storage location either manually or automatically by recognizing the new tire ID. After each uneven wear self-check, if the detected uneven wear level changes, the system automatically updates the stored data and applies the updated uneven wear penalty factor. It is passed to the steering coordination control model for subsequent torque distribution correction calculations under steering conditions.

[0073] Preferably, in step S4, the introduced tire wear factor weighting coefficient The calculation formula is revised as follows:

[0074]

[0075] in, The wear penalty factor is determined based on the severity level of the historical wear characteristic parameters, and its value range is [value range missing]. The more severe the uneven wear, The larger the value; The weighting coefficient for the wear penalty is introduced; When distributing steering torque, it actively reduces the force priority of unevenly worn tires to prevent them from wearing out further.

[0076] In this embodiment, the wear factor weighting coefficient The design aims to quantify tire wear risk into a comprehensive indicator that can be directly incorporated into torque distribution calculations. This formula consists of three weighted terms:

[0077] First item This reflects the impact of vertical load changes on tire wear sensitivity. When the wheel's vertical load decreases due to steering roll, this value increases, indicating that the wheel is more prone to slippage and requires more suppression in torque distribution. In this embodiment, the nominal load... The static load of each wheel when the vehicle is stationary; real-time load. Data is collected in real time by suspension strain gauges. Weighting coefficients. The actual vehicle calibration value is 0.35.

[0078] Second item It reflects the degree of deviation between the current slip state and the allowable slip threshold. When the real-time slip rate... Approaching or exceeding the threshold value When (in this embodiment, it is set to 5%), this item increases rapidly, triggering rapid torque suppression. Weighting coefficient The value is set to 0.50 to ensure that the slip ratio factor plays a dominant role in the control decision.

[0079] Third item This is a newly added wear penalty term in this invention. The wear penalty factor is... The self-inspection process described in claim 2 determines the value as follows: 0.2 for mild uneven wear, 0.5 for moderate uneven wear, and 0.8 for severe uneven wear; for normal tires without uneven wear markings, The value is 0. Penalty weight coefficient. Based on actual vehicle wear comparison tests, a value of 0.25 was determined, resulting in a tire with severe uneven wear. The value is approximately 0.2 higher than that of a normal tire, resulting in a noticeable load transfer effect in torque distribution calculations.

[0080] Within each torque distribution calculation cycle (10ms), the vehicle controller 2 calculates the torque distribution of each of the four wheels. value, A higher value indicates a higher risk of wear for the wheel. While meeting the total drive torque requirement, the controller prioritizes reducing the torque distribution to that wheel and transfers the reduced portion to the [wheel type / wheel]. Wheels with smaller values. By introducing Tire wear is uneven. The baseline value is systematically higher than that of normal tires, thus providing continuous torque protection under all working conditions and preventing its weak areas from being damaged faster due to excessive stress.

[0081] Preferably, in step S1, the real-time parameters for four-wheel alignment include at least the front wheel toe angle. Front wheel camber angle The four-wheel alignment parameters are collected in real time by high-precision angle sensors installed on the suspension links or steering knuckles, or by reading the online four-wheel alignment estimates estimated by the electronic control unit based on the fusion of wheel speed and inertial measurement unit 6 data through the vehicle bus.

[0082] This embodiment provides two methods for obtaining real-time four-wheel alignment parameters to adapt to vehicles with different configuration levels.

[0083] The first approach uses a high-precision angle sensor for direct measurement. On vehicles equipped with active suspension or higher-spec models, a magneto-electric angle encoder is installed at the hinge point between the lower control arm and the steering knuckle of the front suspension. This encoder has a resolution of 0.01° and is used to measure the front wheel camber angle in real time. A linear displacement sensor is installed at the connection between the steering tie rod and the steering knuckle, and the front wheel toe angle is obtained through geometric conversion. The rear wheel toe angle is obtained using the same principle by an angle sensor installed on the rear suspension trailing arm or tie rod. The aforementioned sensor signal is transmitted to the analog input module of the vehicle controller 2 via a shielded cable, with a sampling frequency of 100Hz. After low-pass filtering (cutoff frequency 5Hz), it is used as a real-time positioning parameter in subsequent calculations. This solution offers high measurement accuracy and fast response, but the hardware cost is relatively high.

[0084] Approach Two: Online Estimation Based on Multi-Sensor Data Fusion. For economy vehicles without dedicated angle sensors, this embodiment utilizes data from the vehicle's existing wheel speed sensor 4, inertial measurement unit 6 (IMU), and steering wheel angle sensor 3 to estimate four-wheel alignment parameters online using an extended Kalman filter. The estimation principle is as follows: When the vehicle is traveling in a straight line at a low to medium speed (30~50km / h), if the four-wheel alignment parameters are normal, the wheel speeds of each wheel should be strictly equal, and the yaw rate detected by the IMU should be close to zero. If there is a toe angle deviation, the left and right wheels will have a slight speed difference; if there is a camber angle deviation, the vehicle will experience a continuous lateral acceleration offset. The filter takes the steering wheel angle and vehicle speed as inputs, and the wheel speed difference and yaw rate deviation as observations, to recursively estimate the current toe angle deviation and camber angle deviation. This estimated value is updated every 1 second and sent to the vehicle controller 2 via the vehicle CAN bus 10. Because the estimation accuracy is affected by factors such as road slope and crosswind, it is used as an auxiliary reference value for correction, and the corresponding correction coefficient amplitude is halved compared with the direct measurement method. Regardless of the method used, the real-time four-wheel alignment parameters are compared with the factory nominal values ​​(stored in the vehicle controller 2 EEPROM). When the deviation exceeds the preset standard range, the model correction logic described in claim 5 is triggered.

[0085] Preferably, in step S2, the specific method for correcting the Ackermann steering geometry model based on the real-time parameters of the four-wheel alignment is as follows:

[0086] When the front wheel toe angle is detected When the angle exceeds the preset standard range, an equivalent angle correction is introduced. ,in This is the toe-influence coefficient; when the camber angle is detected... When the value exceeds the preset standard range, a tire lateral stiffness correction coefficient is introduced. ,in The camber wear sensitivity coefficient is used to substitute the corrected equivalent steering angle and the corrected tire lateral stiffness into the theoretical target wheel speed calculation model to eliminate the trajectory deviation caused by the drift of the four-wheel alignment parameters.

[0087] This embodiment details the specific calculation process of the four-wheel alignment parameter correction Ackermann steering geometry model.

[0088] Toe angle deviation correction:

[0089] Toe angle is defined as the angle between the wheel center plane and the vehicle's longitudinal symmetry plane. Positive toe angle indicates that the front of the wheel is turned inward. When the toe angle deviates from the nominal value... When the toe-in is typically 0° to 0.2°, the actual rolling direction of the wheel deviates from the theoretical direction determined by the steering trapezoid, causing the tire to experience continuous lateral slippage during rolling.

[0090] In this embodiment, the toe angle deviation is converted into a correction amount for the equivalent front wheel steering angle: Among them, the pre-beam influence coefficient The value was determined to be 0.85 in this embodiment through vehicle dynamics simulation and real-vehicle calibration. The corrected front wheel steering angle... ,in The nominal steering angle of the front wheel is calculated by the steering ratio from the steering wheel angle sensor 3.

[0091] The instantaneous steering center position and turning radius are recalculated using the corrected front wheel steering angle. This updates the theoretical target wheel speed for each wheel.

[0092] Camber deviation correction: Camber is defined as the angle between the wheel's center plane and the vertical plane; negative camber indicates that the top of the wheel tilts inward. Camber deviation directly affects the shape of the tire's contact patch and its lateral stiffness. When the camber deviates from the nominal value, the tire's lateral stiffness changes non-linearly, causing a difference between the actual wheel slip angle and the theoretically calculated value under the same lateral force.

[0093] This embodiment introduces a tire lateral stiffness correction factor:

[0094]

[0095] Among them, the outward wear sensitivity coefficient According to tire bench testing and calibration, for commonly used 235 / 55 R19 tires The value is 0.12. Corrected tire lateral stiffness. ,in This is the nominal lateral stiffness under the standard outward tilt angle.

[0096] When calculating the theoretical slip angle of each wheel, the corrected slip stiffness value is used to make the target wheel speed calculation closer to the actual lateral mechanical characteristics of the tire under the current camber angle.

[0097] Substituting both of the above corrections into the Ackermann steering geometry model, taking a left turn as an example, the theoretical wheel speed of the outer front wheel is corrected as follows:

[0098]

[0099] in, For vehicle speed, The front wheel track. This refers to the vehicle's wheelbase. This is a reference value for the yaw rate calculated based on the corrected turning radius. The wheel speed fine-tuning coefficient related to the camber angle correction is calculated from the corrected lateral stiffness.

[0100] Through the above dynamic correction, the theoretical target wheel speed model can adaptively follow the real-time changes in the four-wheel alignment parameters, fundamentally eliminating the implicit trajectory deviation and continuous micro-slip caused by suspension aging or parameter drift.

[0101] Preferably, it also includes four-wheel alignment abnormality warning and torque limiting protection steps:

[0102] When the real-time parameters of the four-wheel alignment are determined to exceed the preset safety threshold range, a four-wheel alignment abnormality warning signal is output to prompt the driver to inspect and repair; at the same time, during the steering process, the maximum driving torque of all wheels is limited to no more than 70% of the rated torque, and regenerative braking is used first to decelerate in order to reduce the tire wear rate under abnormal alignment conditions.

[0103] This embodiment adds a four-wheel alignment anomaly warning and torque limiting protection function as a supplementary safety strategy to the model correction described in claim 5. When the deviation of the four-wheel alignment parameters is too large and exceeds the effective compensation range of the model correction, simply relying on algorithm correction is not enough to completely eliminate abnormal wear. At this time, it is necessary to protect the tires through warning and active torque limiting.

[0104] The vehicle controller 2 presets the safety threshold range for four-wheel alignment parameters: front wheel toe angle deviation safety threshold: ±0.5°; front wheel camber angle deviation safety threshold: ±1.2°; rear wheel toe angle deviation safety threshold: ±0.4°; the above thresholds are determined based on tire wear bench test data: when the deviation exceeds this range, even if the correction model described in claim 5 is used, the tire wear rate under steering conditions is still more than 30% higher than the normal state.

[0105] When any real-time parameter of the four-wheel alignment exceeds the corresponding safety threshold range, the vehicle controller 2 sends a four-wheel alignment abnormality warning signal to the instrument panel 12 via the CAN bus 10. The instrument panel 12 illuminates a yellow fault indicator light and displays the text "Please check the four-wheel alignment". This warning signal remains until the next power-on self-test confirms that the parameters have returned to the safe range, or the fault code is cleared by after-sales diagnostic tools.

[0106] During the warning state activation, the vehicle controller 2 imposes the following restrictions on the drive torque output: the upper limit of the drive torque for all wheels is limited to 70% of the motor's rated torque. This limit is determined based on empirical data and can reduce tire wear rate by approximately 40% while ensuring the vehicle's basic driving capability. When the steering wheel angle exceeds 50°, the upper limit of the drive torque for the inner wheels is further reduced to 50% of the rated torque to reduce slippage wear of the inner tires under reduced load conditions. During deceleration, regenerative braking is used preferentially over mechanical braking, and the distribution of regenerative braking torque follows the wear protection rules described in claim 9 to avoid applying excessive longitudinal force to the unevenly worn tires during braking.

[0107] The torque limiting protection will automatically deactivate once the four-wheel alignment parameters return to a safe range. If the warning status persists for more than 500km without maintenance, the vehicle controller 2 will activate the secondary torque limiting protection, further limiting the maximum drive torque to 50% of the rated torque, and displaying a message on the instrument panel 12: "Please have the four-wheel alignment checked immediately."

[0108] Preferably, it also includes a periodic self-inspection step for tires with uneven wear:

[0109] Each time the vehicle performs a self-test upon power-on or when the accumulated mileage reaches a preset interval, the historical wear characteristic parameter detection in step S1 is executed; if a new tire with uneven wear is detected or the wear level changes, the wear mark and penalty factor are updated. And store it in non-volatile memory.

[0110] This embodiment describes in detail the triggering mechanism, execution process, and data update logic of the periodic self-inspection of unevenly worn tires.

[0111] The tire wear self-check is automatically triggered under the following two conditions: Each time the vehicle wakes up from sleep mode (e.g., unlocking the door, pressing the brake pedal to prepare for starting), if more than 24 hours have passed since the last complete self-check, a complete self-check is performed. A complete self-check is automatically performed every 500km increase in the vehicle's cumulative mileage, when the current vehicle speed is zero and the parking brake is locked. After the self-check is triggered, the vehicle controller 2 wakes up the tread scanning sensor 7 via the LIN bus or a dedicated signal line, and executes the tread depth scanning and wear determination process described in claim 2.

[0112] The self-check process scans the four tires sequentially: front left, front right, rear left, and rear right. Each tire scan takes approximately 8 seconds, with a total self-check time of approximately 35 seconds. During the self-check, if the driver prepares to drive (e.g., shifting into Drive), the process is immediately interrupted. Completed scan data is retained, while unfinished tire scans are deferred to the next trigger. To avoid frequent self-checks impacting user experience, the system sets a minimum self-check interval of 200km. If the trigger conditions are met multiple times within 200km, only the first self-check will be performed.

[0113] After each self-test, the vehicle controller 2 compares the test results with the historical wear patterns stored in the EEPROM. If a tire is identified as an unevenly worn tire for the first time, a new uneven wear record for that tire is created in the EEPROM, including the uneven wear type, severity level, and corresponding penalty factor. The system records the inspection timestamp and mileage. If a tire already has a history of uneven wear but the current inspection shows a change in the uneven wear level (upgraded or downgraded), the recorded level and mileage are updated. Value. A reduction in the wear rating typically occurs after tire rotation, where the less worn tire is moved to the wear inspection location. If a tire has a history of uneven wear but the current inspection shows it has returned to normal (e.g., a new tire has been installed), the uneven wear indicator for that tire will be cleared. Reset to 0. All update operations are synchronously written to EEPROM to ensure that data is not lost after the vehicle is powered off.

[0114] To address tire rotation scenarios, the wear tracking data is linked to the tire pressure monitoring system (TPMS) sensor ID. When the vehicle detects a change in the TPMS sensor position (based on received signal strength or phase difference), the wear tracking data is automatically migrated to follow the physical tire position, ensuring that the wear tracking mark always corresponds to the correct physical tire.

[0115] Preferably, step S4 further includes:

[0116] When the vehicle speed is lower than the preset low speed threshold and the steering wheel angle is greater than the preset large steering angle threshold, the vehicle is determined to be in a low speed and large steering angle condition, and the system switches to the electronic differential assist steering mode. In this mode, it first determines whether the inner rear wheel is the tire with uneven wear. If so, the negative torque braking command of the inner rear wheel is transferred to the front wheel on the same side, or the negative torque amplitude is reduced to protect the tire with uneven wear.

[0117] This embodiment details a special protection strategy for tires with uneven wear under low-speed, high-angle conditions.

[0118] The vehicle controller 2 monitors vehicle speed and steering wheel angle signals in real time. The vehicle is determined to be in a low-speed, large-angle driving condition when the following conditions are simultaneously met: vehicle speed... ,in The preset low-speed threshold is set to 10 km / h in this embodiment; the absolute value of the steering wheel angle is the preset large-angle threshold, which is set to 300° in this embodiment (corresponding to a front wheel angle of approximately 25°~30°). Typical scenarios for this condition include: parking in a parking lot, making a U-turn on a narrow road, and making a right-angle turn.

[0119] Under low-speed, large-angle conditions, the system activates the electronic differential steering assist mode. This mode works by applying a slight braking torque (negative torque) to the inner rear wheel, causing its speed to drop slightly below the theoretical value for pure rolling, while simultaneously supplementing the positive drive torque to the outer front wheel. This utilizes the torque difference between the left and right wheels to generate an auxiliary yaw moment, helping the vehicle rotate around the inner rear wheel, thereby reducing the turning radius and improving steering agility. In conventional electronic differential steering assist, the negative torque amplitude of the inner rear wheel is typically set to 10% to 20% of the motor's rated torque.

[0120] This embodiment introduces tire wear protection logic in the electronic differential steering assist mode. The execution steps are as follows: Before activating the steering assist mode, the vehicle controller 2 queries the tire wear indicator of the inner rear wheel. Taking a left turn as an example, it queries the tire wear status of the left rear wheel. If... The inner rear wheel is marked as an unevenly worn tire. If the wear level is 1 (mild), the negative torque braking command originally applied to that wheel will be processed according to the following rules: if the wear level is 1 (mild), the negative torque amplitude will be reduced by 50%; if the wear level is 2 or 3 (moderate or severe), the negative torque command will be completely cancelled and transferred to the front wheel on the same side for execution.

[0121] Same-side front wheel negative torque execution: After receiving the transferred negative torque command, the hub motor 1 of the inner front wheel enters the power generation mode to generate the required braking torque. Because the front wheels experience a large vertical load and sufficient contact area at low speeds and large steering angles, the impact of negative torque on their wear is far less than on the inner rear wheel, whose load has been significantly reduced. Yaw moment compensation: Since the transfer of negative torque from the rear wheels to the front wheels shortens the lever arm of the auxiliary yaw moment, the system simultaneously increases the positive drive torque supplement to the outer front wheel to maintain a constant total yaw moment and ensure that the steering assist effect is not compromised. Through the above protection strategies, the unevenly worn tires are spared additional braking friction loads under low-speed, large-steering-angle conditions, their weak areas are effectively protected, and the steering assist function remains unaffected.

[0122] Preferably, it also includes a deceleration and steering coordination control step:

[0123] When a brake pedal opening signal is detected and the steering wheel angle is non-zero, the road adhesion limit is estimated by combining the vertical load of each wheel. When distributing regenerative braking torque, if the rear wheel is marked as an unevenly worn tire, the regenerative braking torque of the rear wheel is further limited to no more than 50% of the road adhesion limit threshold estimated based on the vertical load, and the reduced braking torque is transferred to the front axle or the coaxial non-unevenly worn tire.

[0124] This embodiment details the regenerative braking coordinated control strategy under deceleration and steering conditions, especially the differentiated protection measures for unevenly worn rear wheels.

[0125] For deceleration and steering condition recognition, the vehicle controller 2 detects braking intention via the brake pedal position sensor 9 and steering state via the steering wheel angle sensor 3. When the brake pedal opening is greater than 5% and the absolute value of the steering wheel angle is greater than 10°, the vehicle is determined to have entered a deceleration and steering condition. The physical characteristics of this condition are: the vehicle decelerates in a curve, centrifugal force causes the load on the inner wheel to decrease and the load on the outer wheel to increase; at the same time, braking deceleration causes the load on the rear axle to transfer to the front axle, further reducing the vertical load on the rear wheels.

[0126] Before distributing the regenerative braking torque, the vehicle controller 2 first estimates the current road adhesion limit for each wheel:

[0127]

[0128] in, The road surface adhesion coefficient is estimated in real time by a Kalman filter that fuses wheel speed sensor 4 and IMU data. The initial value for dry asphalt pavement is 0.85, and the value for wet pavement is dynamically adjusted according to the slip ratio feedback. The real-time vertical load on each wheel is collected by the suspension strain gauges and dynamically corrected by combining longitudinal acceleration and lateral acceleration.

[0129] Multiply the adhesion limit by the tire rolling radius. The maximum regenerative braking torque that each wheel can withstand is obtained:

[0130]

[0131] In conventional strategies, the regenerative braking limit for unevenly worn rear wheels is determined by allocating regenerative braking torque at a fixed ratio between the front and rear axles (e.g., 60% front axle, 40% rear axle) to maximize braking energy recovery efficiency. In this embodiment, before distributing regenerative braking, the rear wheel unevenness markings are checked: if neither the left nor right rear wheel is marked as unevenly worn, the torque is allocated according to the conventional ratio. If a rear wheel is marked as unevenly worn, the upper limit of the regenerative braking torque for that rear wheel is further tightened to:

[0132]

[0133] That is, the regenerative braking torque of the rear wheel with uneven wear should not exceed 50% of its adhesion limit, so as to leave sufficient adhesion margin for lateral force and prevent sideslip wear caused by excessive longitudinal braking force squeezing out lateral adhesion.

[0134] The regenerative braking torque reduced due to the aforementioned limits is transferred according to the following priority: Within the limits allowed by the motor and battery, the reduced braking torque is added to the front axle regenerative braking command. The front axle experiences increased vertical load during deceleration and steering, with sufficient traction margin to safely handle the additional braking torque. If the front axle's regenerative braking capacity has reached its limit (limited by motor power generation or battery charging power), the reduced braking torque is transferred to the unmarked rear wheel on the opposite side of the same axle. If the above transfer still cannot fully absorb the total braking demand, the remaining portion is supplemented by the hydraulic-mechanical braking system. Through this strategy, the unmarked rear wheel remains under low load during cornering deceleration, preventing its weak tread area from bearing excessive longitudinal shear force, thus significantly reducing the wear rate.

[0135] Preferably, it also includes a feedback correction step:

[0136] The system monitors the rate of change of wheel slip ratio after torque distribution correction in real time. If the slip ratio does not converge to below a threshold value within a preset adjustment period, an adaptive gain adjustment mechanism is triggered to dynamically increase the weighting coefficient of the wear factor. In If the slip ratio still fails to converge after multiple gain adjustments, and the wheel is marked as an unevenly worn tire, then it is determined that the current uneven wear condition has seriously affected the vehicle's dynamic control, and the speed limit protection mode is activated.

[0137] This embodiment details the closed-loop feedback correction mechanism for torque distribution control, ensuring that the control effect achieves the expected results under various operating conditions. After each execution of the torque distribution correction command, the vehicle controller 2 continuously monitors the changes in the slip ratio of each wheel at a period of 10ms. For wheels that are determined to have exceeded the slip ratio threshold S... th For the wheels, the system records the following parameters: peak slip ratio S peak : The maximum slip ratio reached after control intervention; t conv Convergence time: the time it takes for the slip ratio to fall back from its peak to the threshold value S. th The following time is required; steady-state slip ratio S steady : The stable value of the slip ratio after convergence.

[0138] Gain adaptive adjustment, if a certain wheel is within a preset adjustment period T adj If the slip ratio does not converge to below the threshold within 200ms (as set in this embodiment), the adaptive gain adjustment mechanism is triggered. The adjustment process is as follows:

[0139] Determining the cause of convergence failure: Vehicle controller 2 analyzes the slip ratio change curve of the wheel. If the slip ratio exhibits oscillating characteristics, it indicates that the current control gain is too high; if the slip ratio decreases monotonically but at a slow speed, it indicates that the current control gain is insufficient. Dynamically increase... Value: In cases of insufficient gain, the system operates according to a preset step size. Increase the weighting coefficient of the wear factor In Value. The increase is subject to an upper limit. max =1.0 constraint. Recalculate torque distribution: with the updated... Value recalculated And generate the corrected torque distribution command. Iterative adjustment: If the slip ratio is within the next T after the first gain adjustment... adj The internal convergence has not yet occurred, and the increment continues to increase. The value is maintained until the slip ratio converges or The upper limit has been reached. Adaptive gain adjustment only applies to the wheel that currently triggered the slippage; other wheels are not affected. The value remains unchanged. Adjusted The value remains valid throughout the current driving cycle and returns to the nominal value after the vehicle is powered off.

[0140] Speed ​​limiting protection for unevenly worn tires, after three gain adjustments ( The value has increased by 0.15 cumulatively, the slip ratio has not yet converged below the threshold, and the wheel is marked as an unevenly worn tire. If the wear condition is detected, it is determined that the current uneven wear has severely affected the vehicle's dynamic control capabilities, and continued driving will lead to rapid tire damage. At this time, the vehicle controller 2 activates the speed limit protection mode: speed limit setting: the speed limit value is determined according to the wear level - mild uneven wear speed limit 80km / h, moderate uneven wear speed limit 60km / h, severe uneven wear speed limit 40km / h.

[0141] Speed ​​Limit Execution: By limiting the upper limit of motor output power and controlling the accelerator pedal response curve, the maximum vehicle speed is limited to below a set value. Instrument Panel Warning: The instrument panel displays the text "Tire wear is severe, please slow down and replace the tires as soon as possible," accompanied by an audible alarm. Speed ​​Limit Removal Conditions: The speed limit protection mode is only removed after tire replacement and removal of uneven wear markers, or by forced reset using authorized repair equipment. Through the above feedback correction and speed limit protection mechanisms, this invention not only achieves precise tire wear suppression under normal operating conditions, but also actively limits the vehicle's operating range under extreme uneven wear conditions, fundamentally eliminating safety hazards caused by excessive tire wear.

[0142] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A steering coordination control method for reducing tire wear in a four-wheel drive electric vehicle, characterized in that, Includes the following steps: Step S1: Collect vehicle driving status data in real time. The driving status data includes at least the steering wheel angle signal, vehicle speed signal, wheel speed signal of each wheel, vertical load signal of each wheel, yaw rate signal of the whole vehicle, historical wear characteristic parameters of each tire, and real-time parameters of four-wheel alignment. Step S2: Based on the steering wheel angle signal and vehicle speed signal, and using the Ackerman steering geometry model combined with the vehicle geometry model corrected by the real-time parameters of the four-wheel alignment, calculate the theoretical target wheel speed of each wheel under the current steering condition. Step S3: Compare the actual wheel speeds of each wheel with the corresponding theoretical target wheel speeds to calculate the real-time slip ratio of each wheel; Step S4: When the real-time slip ratio of any wheel exceeds the preset slip ratio threshold, the torque distribution correction of the four-wheel independent drive motor is calculated with the objective function of minimizing tire slip power loss, combined with the vertical load signal of each wheel and the historical wear characteristic parameters. Among them, the wheel with wear mark is penalized by a penalty coefficient during torque distribution to reduce its load. Step S5: Generate a target torque command based on the torque distribution correction amount and send it to each wheel hub motor controller. By adjusting the driving torque of the inner and outer wheels, the actual wheel speed converges to the theoretical target wheel speed, maintaining the pure rolling friction state between the tire and the ground.

2. The steering coordination control method for reducing tire wear in a four-wheel drive electric vehicle according to claim 1, characterized in that, In step S1, the method for obtaining the historical wear characteristic parameters is as follows: By using a tread scanning sensor installed inside the wheel arch or a wear estimation model based on historical vehicle driving data, the residual tread depth of each tire on the inner, middle, and outer sides is obtained, and the difference in tread depth between the inner and outer sides is calculated. and the difference in tread depth between the shoulder and the center of the tire. ,like Exceeding the preset outward wear threshold or If the wear exceeds the preset toe-in wear threshold, the tire is marked as an uneven wear tire, and the uneven wear type and severity level are recorded.

3. The steering coordination control method for reducing tire wear in a four-wheel drive electric vehicle according to claim 1, characterized in that, In step S4, the weighted coefficient of the tire wear factor is introduced. The calculation formula is revised as follows: in, The wear penalty factor is determined based on the severity level of the historical wear characteristic parameters, and its value range is [value range missing]. The more severe the uneven wear, The larger the value; The weighting coefficient for the wear penalty is introduced; When distributing steering torque, it actively reduces the force priority of unevenly worn tires to prevent them from wearing out further.

4. The steering coordination control method for reducing tire wear in a four-wheel drive electric vehicle according to claim 1, characterized in that, In step S1, the real-time parameters for four-wheel alignment include at least the front wheel toe angle. Front wheel camber angle The four-wheel alignment parameters are collected in real time by high-precision angle sensors installed on the suspension links or steering knuckles, or by reading the online four-wheel alignment estimates from the electronic control unit based on the fusion of wheel speed and inertial measurement unit data via the vehicle bus.

5. The steering coordination control method for reducing tire wear in a four-wheel drive electric vehicle according to claim 1, characterized in that, In step S2, the specific method for correcting the Ackermann steering geometry model based on the real-time parameters of the four-wheel alignment is as follows: When the front wheel toe angle is detected When the angle exceeds the preset standard range, an equivalent angle correction is introduced. in This is the toe-influence coefficient; when the camber angle is detected... When the value exceeds the preset standard range, a tire lateral stiffness correction coefficient is introduced. ,in The coefficient for sensitivity to outward tilting wear; The corrected equivalent steering angle and the corrected tire lateral stiffness are substituted into the theoretical target wheel speed calculation model to eliminate the trajectory deviation caused by the drift of the four-wheel alignment parameters.

6. The steering coordination control method for reducing tire wear in a four-wheel drive electric vehicle according to claim 1, characterized in that, It also includes four-wheel alignment abnormality warning and torque limiting protection steps: When the real-time parameters of the four-wheel alignment are determined to exceed the preset safety threshold range, a four-wheel alignment abnormality warning signal is output to prompt the driver to inspect and repair. At the same time, during the steering process, the maximum driving torque of all wheels is limited to no more than 70% of the rated torque, and regenerative braking is used first to decelerate in order to reduce the tire wear rate under abnormal alignment conditions.

7. A steering coordination control method for reducing tire wear in a four-wheel drive electric vehicle according to claim 1, characterized in that, It also includes periodic self-inspection steps for tires with uneven wear: Each time the vehicle performs a self-test upon power-on or when the accumulated mileage reaches a preset interval, the historical wear characteristic parameter detection in step S1 is executed; if a new tire with uneven wear is detected or the wear level changes, the wear mark and penalty factor are updated. And store it in non-volatile memory.

8. A steering coordination control method for reducing tire wear in a four-wheel drive electric vehicle according to claim 1, characterized in that, Step S4 further includes: When the vehicle speed is lower than the preset low speed threshold and the steering wheel angle is greater than the preset large steering angle threshold, the vehicle is determined to be in a low speed and large steering angle condition, and the system switches to the electronic differential assist steering mode. In this mode, it first determines whether the inner rear wheel is the tire with uneven wear. If so, the negative torque braking command of the inner rear wheel is transferred to the front wheel on the same side, or the negative torque amplitude is reduced to protect the tire with uneven wear.

9. A steering coordination control method for reducing tire wear in a four-wheel drive electric vehicle according to claim 1, characterized in that, It also includes deceleration and steering coordination control steps: When a brake pedal opening signal is detected and the steering wheel angle is non-zero, the road adhesion limit is estimated by combining the vertical load of each wheel. When distributing regenerative braking torque, if the rear wheel is marked as an unevenly worn tire, the regenerative braking torque of the rear wheel is further limited to no more than 50% of the road adhesion limit threshold estimated based on the vertical load, and the reduced braking torque is transferred to the front axle or the coaxial non-unevenly worn tire.

10. A steering coordination control method for reducing tire wear in a four-wheel drive electric vehicle according to claim 1, characterized in that, It also includes a feedback and correction step: The system monitors the rate of change of wheel slip ratio after torque distribution correction in real time. If the slip ratio does not converge to below a threshold value within a preset adjustment period, an adaptive gain adjustment mechanism is triggered to dynamically increase the weighting coefficient of the wear factor. In If the slip ratio still fails to converge after multiple gain adjustments, and the wheel is marked as an unevenly worn tire, then it is determined that the current uneven wear condition has seriously affected the vehicle's dynamic control, and the speed limit protection mode is activated.

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