Tire cornering stiffness estimation method based on vehicle motion control system

Abstract

The application discloses a kind of tire cornering stiffness estimation method based on vehicle motion control system, belong to vehicle testing technical field, this tire cornering stiffness estimation method is based on vehicle motion control system and obtains the real-time signal of vehicle, and according to real-time signal, the maximum lateral force of four wheels and four-wheel total slip rate of vehicle are calculated;According to four-wheel maximum lateral force and four-wheel total slip rate, front wheel maximum lateral force, front wheel total slip rate and rear wheel maximum lateral force are obtained;Then, according to front wheel maximum lateral force and front wheel total slip rate, front wheel cornering stiffness is calculated, and rear wheel cornering stiffness is calculated according to rear wheel maximum lateral force;Finally, according to front wheel cornering stiffness and rear wheel cornering stiffness, front and rear axle cornering stiffness is calculated, by fusing multi-source real-time signal, the estimation accuracy under nonlinear condition can be significantly improved, and without using complex iteration and filtering algorithm, the strong robustness and low algorithm power requirement of algorithm are guaranteed, without additional hardware, easy to practical vehicle engineering application.

Description

Technical Field

[0001] This invention relates to the field of vehicle testing technology, and in particular to a method and control device for estimating tire lateral stiffness based on a vehicle motion control system. Background Technology

[0002] Vehicle Motion Control (VMC) is one of the core technologies of autonomous driving. Based on decisions and planning layer instructions, VMC controls the vehicle to travel along a reference trajectory by combining vehicle state and environmental information. Tire lateral stiffness is a key parameter describing the tire's ability to generate lateral forces and is central to building high-precision vehicle dynamics models. Accurate lateral stiffness is the foundation for advanced control algorithms such as Model Predictive Control (MPC) to make optimal decisions and accurately predict vehicle states (such as yaw rate and sideslip angle). Vehicle dynamics are time-varying, and lateral stiffness changes significantly with factors such as load, tire pressure, road conditions, and tire wear. By estimating its current value online in real time, the control system can adaptively adjust the control strategy and compensate for parameter changes, thereby greatly improving the vehicle's handling stability and safety under extreme conditions or on low-adhesion surfaces. Therefore, accurate estimation of lateral stiffness is an indispensable part of achieving high-performance, robust vehicle motion control.

[0003] Existing methods for estimating lateral stiffness mainly suffer from the following problems: reliance on specialized equipment, computational complexity, poor real-time performance, insufficient robustness, reliance on experience for parameter adjustment, and high computational requirements for engineering applications. Summary of the Invention

[0004] This invention aims to address at least one of the technical problems existing in the prior art. To this end, this invention proposes a tire lateral stiffness estimation method based on a vehicle motion control system, which can significantly improve the estimation accuracy under nonlinear conditions, ensure the algorithm's strong robustness and low computational requirements, requires no additional hardware, and is easy to apply in real-world vehicle engineering.

[0005] According to a first aspect of the present invention, a tire lateral stiffness estimation method based on a vehicle motion control system includes: The vehicle motion control system acquires real-time signals from the vehicle and calculates the maximum lateral force and total slip ratio of the four wheels based on these signals. Based on the maximum lateral force of the four wheels and the total slip ratio of the four wheels, obtain the maximum lateral force of the front wheel, the total slip ratio of the front wheel, and the maximum lateral force of the rear wheel; The front wheel lateral stiffness is calculated based on the maximum lateral force and total slip ratio of the front wheels, and the rear wheel lateral stiffness is calculated based on the maximum lateral force of the rear wheels. The front and rear axle lateral stiffnesses are calculated based on the front and rear wheel lateral stiffnesses. These lateral stiffnesses are used to evaluate the tire lateral stiffness of the vehicle.

[0006] The tire lateral stiffness estimation method based on the vehicle motion control system according to embodiments of the present invention has at least the following beneficial effects: This invention acquires real-time signals from the vehicle's motion control system and calculates the maximum lateral force and total slip ratio of the four wheels based on these signals. The maximum lateral force, total slip ratio, and maximum lateral force of the front and rear wheels are then obtained from these signals. The front wheel lateral stiffness is calculated based on the maximum lateral force and total slip ratio, and the rear wheel lateral stiffness is calculated based on the maximum lateral force. Finally, the front and rear axle lateral stiffness are calculated based on the front and rear wheel lateral stiffness. These lateral stiffnesses are used to evaluate the tire lateral stiffness of the vehicle. By fusing multi-source real-time signals, the estimation accuracy under nonlinear conditions can be significantly improved. Furthermore, it eliminates the need for complex iterative and filtering algorithms, ensuring strong robustness and low computational requirements. It requires no additional hardware and is easily applied in real-world vehicle engineering.

[0007] According to some embodiments of the present invention, the real-time signals include target yaw rate, actual yaw rate, vehicle speed, vehicle friction coefficient, stability control indicator, four-wheel vertical force, four-wheel longitudinal slip ratio, and front and rear axle side slip angles; The process of acquiring real-time signals from the vehicle based on the vehicle motion control system, and calculating the maximum lateral force and total slip ratio of the four wheels based on the real-time signals, includes: When the difference between the target value and the actual value of the yaw rate is greater than or equal to the first preset value, and the vehicle speed is greater than or equal to the second preset value, the vehicle friction coefficient is determined as the vehicle's lateral friction coefficient. The maximum lateral force of the four wheels is determined based on the lateral friction coefficient, the stability control flag, and the vertical force of the four wheels. The total slip ratio of the four wheels is calculated based on the longitudinal slip ratio of the four wheels and the front and rear axle slip angles.

[0008] According to some embodiments of the present invention, the step of acquiring real-time signals of the vehicle based on the vehicle motion control system and calculating the maximum lateral force of the four wheels and the total slip ratio of the four wheels of the vehicle based on the real-time signals further includes: When the difference between the target value and the actual value of the yaw rate is greater than or equal to the first preset value, and the vehicle speed is greater than or equal to the second preset value, the lateral friction coefficient is set to the third preset value.

[0009] According to some embodiments of the present invention, the maximum lateral force of the four wheels includes the maximum lateral force of the left front wheel, the maximum lateral force of the right front wheel, the maximum lateral force of the left rear wheel, and the maximum lateral force of the right rear wheel; the vertical force of the four wheels includes the vertical force of the left front wheel, the vertical force of the right front wheel, the vertical force of the left rear wheel, and the vertical force of the right rear wheel; The step of determining the maximum lateral force of the four wheels based on the lateral friction coefficient, the stability control flag, and the vertical force of the four wheels includes: When the stability control flag is invalid, the maximum lateral force of the left front wheel is the product of the vertical force of the left front wheel and the lateral friction coefficient; the maximum lateral force of the right front wheel is the product of the vertical force of the right front wheel and the lateral friction coefficient; the maximum lateral force of the left rear wheel is the largest of the vertical forces of the left rear wheel and the right rear wheel; and the maximum lateral force of the right rear wheel is the largest of the vertical forces of the left rear wheel and the right rear wheel. When the stability control flag is invalid, the maximum lateral force of the left front wheel is the product of the vertical force of the left front wheel and the lateral friction coefficient, the maximum lateral force of the right front wheel is the product of the vertical force of the right front wheel and the lateral friction coefficient, the maximum lateral force of the left rear wheel is equal to the vertical force of the left rear wheel, and the maximum lateral force of the right rear wheel is equal to the vertical force of the right rear wheel.

[0010] According to some embodiments of the present invention, the four-wheel longitudinal slip ratio includes the longitudinal slip ratio of the left front wheel, the longitudinal slip ratio of the right front wheel, the longitudinal slip ratio of the left rear wheel, and the longitudinal slip ratio of the left rear wheel; the front and rear axle sideslip angles include the front axle sideslip angle and the rear axle sideslip angle; the four-wheel total slip ratio includes the total slip ratio of the left front wheel, the total slip ratio of the right front wheel, the total slip ratio of the left rear wheel, and the total slip ratio of the right rear wheel; The calculation of the total slip ratio of the four wheels based on the longitudinal slip ratio of the four wheels and the front and rear axle slip angles includes: The values ​​of the total slip ratio of the left front wheel, the total slip ratio of the right front wheel, the total slip ratio of the left rear wheel, and the total slip ratio of the right rear wheel are calculated according to the following formulas: The total slip ratio of the left front wheel = [(longitudinal slip ratio of the left front wheel * fourth preset value)^2 + (front axle sideslip angle * fifth preset value)^2]^0.5; The total slip ratio of the right front wheel = [(longitudinal slip ratio of the right front wheel * fourth preset value)^2 + (front axle sideslip angle * fifth preset value)^2]^0.5; The total slip ratio of the left rear wheel = [(longitudinal slip ratio of the left rear wheel * sixth preset value)^2 + (rear axle slip angle * seventh preset value)^2]^0.5; The total slip ratio of the right rear wheel is calculated as follows: [(longitudinal slip ratio of the right rear wheel * sixth preset value)^2 + (rear axle slip angle * seventh preset value)^2]^0.5.

[0011] According to some embodiments of the present invention, the maximum lateral force of the front wheels includes the maximum lateral force of the left front wheel and the maximum lateral force of the right front wheel; the total slip ratio of the front wheels includes the total slip ratio of the left front wheel and the total slip ratio of the right front wheel; the lateral stiffness of the front wheels includes the lateral stiffness of the left front wheel and the lateral stiffness of the right front wheel. The calculation of the front wheel lateral stiffness based on the maximum lateral force of the front wheel and the total slip ratio of the front wheel includes: When the vehicle speed is greater than or equal to the eighth preset value, and the total slip ratio of the left front wheel or the total slip ratio of the right front wheel is zero, the lateral stiffness of the left front wheel is the value of the maximum lateral force of the left front wheel divided by the ninth preset value, and the lateral stiffness of the right front wheel is the value of the maximum lateral force of the right front wheel divided by the ninth preset value. When the vehicle speed is greater than or equal to the eighth preset value, and the total slip ratio of the left front wheel or the total slip ratio of the right front wheel is zero, the lateral stiffness of the left front wheel is the value of the maximum lateral force of the left front wheel divided by the total slip ratio of the left front wheel, and the lateral stiffness of the right front wheel is the value of the maximum lateral force of the right front wheel divided by the total slip ratio of the right front wheel.

[0012] According to some embodiments of the present invention, the step of calculating the front wheel lateral stiffness based on the maximum lateral force of the front wheel and the total slip ratio of the front wheel further includes: When the vehicle speed is less than the eighth preset value, the left front wheel lateral stiffness and the right front wheel lateral stiffness are respectively set to the tenth preset value.

[0013] According to some embodiments of the present invention, the maximum lateral force of the rear wheel includes the maximum lateral force of the left rear wheel and the maximum lateral force of the right rear wheel; the lateral stiffness of the rear wheel includes the lateral stiffness of the left rear wheel and the lateral stiffness of the right rear wheel; The calculation of the rear wheel lateral stiffness based on the maximum lateral force of the rear wheel includes: When the vehicle speed is greater than or equal to the eighth preset value, and the longitudinal slip ratio of the left rear wheel or the longitudinal slip ratio of the right rear wheel is zero, the lateral stiffness of the left rear wheel is the value of the maximum lateral force of the left rear wheel divided by the eleventh preset value, and the lateral stiffness of the right rear wheel is the value of the maximum lateral force of the right rear wheel divided by the eleventh preset value. When the vehicle speed is greater than or equal to the eighth preset value, and the longitudinal slip ratio of the left rear wheel or the longitudinal slip ratio of the right rear wheel is zero, the lateral stiffness of the left rear wheel is the value of the maximum lateral force of the left rear wheel divided by the longitudinal slip ratio of the left rear wheel, and the lateral stiffness of the right rear wheel is the value of the maximum lateral force of the right rear wheel divided by the longitudinal slip ratio of the right rear wheel. When the vehicle speed is less than the eighth preset value, the left rear wheel lateral stiffness and the right rear wheel lateral stiffness are respectively set to the twelfth preset value.

[0014] According to some embodiments of the present invention, the front and rear axle lateral stiffness includes front axle lateral stiffness and rear axle lateral stiffness; the front wheel lateral stiffness includes left front wheel lateral stiffness and right front wheel lateral stiffness; the rear wheel lateral stiffness includes left rear wheel lateral stiffness and right rear wheel lateral stiffness. The calculation of the front and rear axle lateral stiffness based on the front wheel lateral stiffness and the rear wheel lateral stiffness includes: The front axle lateral stiffness is the sum of the left front wheel lateral stiffness and the right front wheel lateral stiffness; The rear axle lateral stiffness is the sum of the left rear wheel lateral stiffness and the right rear wheel lateral stiffness.

[0015] According to a second aspect of the present invention, the control device includes at least one processor; and a memory storing instructions that, when executed by the at least one processor, perform the tire lateral stiffness estimation method based on the vehicle motion control system described in the first aspect of the present invention.

[0016] Since the control device adopts all the technical solutions of the tire lateral stiffness estimation method based on the vehicle motion control system in the above embodiments, it has at least all the beneficial effects brought about by the technical solutions in the above embodiments, which will not be repeated here.

[0017] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description

[0018] Figure 1 This is a flowchart of a tire lateral stiffness estimation method based on a vehicle motion control system according to an embodiment of the present invention; Figure 2 This is a schematic diagram illustrating the overall principle of a tire lateral stiffness estimation scheme according to an embodiment of the present invention; Figure 3 This is a flowchart illustrating the specific steps involved in calculating the maximum lateral force and total slip ratio of the four wheels according to an embodiment of the present invention. Figure 4 This is a flowchart of the specific steps for calculating the front wheel lateral stiffness according to an embodiment of the present invention; Figure 5 This is a flowchart illustrating the specific steps involved in calculating the rear wheel lateral stiffness according to an embodiment of the present invention. Detailed Implementation

[0019] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0020] In the description of this invention, it should be understood that the terms "upper" and "lower" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0021] In the description of this invention, "multiple" means two or more; "greater than," "less than," and "exceeding" are understood to exclude the stated number; "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is for the purpose of distinguishing technical features only and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0022] In the description of this invention, it should be noted that terms such as "set up," "install," and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0023] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are some embodiments of the present invention, not all embodiments.

[0024] In existing technologies, vehicle motion control relies on high-precision tire lateral stiffness parameters to achieve trajectory tracking and state prediction. Traditional estimation methods require six-component force sensors or complex dynamic models, which suffer from drawbacks such as high equipment costs, large computational delays, and high parameter sensitivity. In emergency avoidance scenarios on low-adhesion roads, sudden changes in tire load cause a sharp drop in lateral stiffness. Traditional offline calibration methods cannot capture parameter changes in real time, leading to trajectory deviations in the model predictive control algorithm.

[0025] To address these issues, researchers discovered that the vehicle motion control system itself possesses real-time signals such as yaw rate and longitudinal slip ratio, which contain information about the tire's mechanical state. By analyzing the dynamic relationship between the vertical force and friction coefficient of the four wheels, they proposed a direct calculation path for the front and rear wheel lateral stiffness by reconstructing the maximum lateral force using existing sensor data and combining it with the total slip ratio, thus avoiding the introduction of additional hardware.

[0026] Therefore, this application proposes a method for estimating tire lateral stiffness based on a vehicle motion control system.

[0027] Reference Figure 1 As shown, the specific steps include, but are not limited to, the following: Step S100: Obtain real-time signals of the vehicle based on the vehicle motion control system, and calculate the maximum lateral force of the four wheels and the total slip ratio of the four wheels based on the real-time signals. Step S200: Based on the maximum lateral force of the four wheels and the total slip ratio of the four wheels, obtain the maximum lateral force of the front wheel, the total slip ratio of the front wheel, and the maximum lateral force of the rear wheel; Step S300: Calculate the front wheel lateral stiffness based on the maximum lateral force and total slip ratio of the front wheel, and calculate the rear wheel lateral stiffness based on the maximum lateral force of the rear wheel. Step S400: Calculate the front and rear axle lateral stiffness based on the front wheel lateral stiffness and the rear wheel lateral stiffness. The front wheel lateral stiffness, rear wheel lateral stiffness, and front and rear axle lateral stiffness are used to evaluate the tire lateral stiffness of the vehicle.

[0028] The real-time signals include parameters such as yaw rate, vehicle speed, and vertical force, which can be directly read via the vehicle's CAN bus, providing a basic data source for calculations. The maximum lateral force of the four wheels represents the theoretical lateral force limit of the tire under current operating conditions, determined by the product of vertical force and the coefficient of friction, reflecting the impact of load distribution on tire performance. The total slip ratio of the four wheels integrates longitudinal slip and sideslip angle data, using a vector sum calculation method to comprehensively characterize the tire's slip state. The front wheel lateral stiffness is calculated as the ratio of the maximum lateral force to the total slip ratio, reflecting the stiffness characteristics of the tire's lateral force as slip changes. The rear wheel lateral stiffness is calculated separately based on the maximum lateral force, adapting to the differences in mechanical characteristics under rear axle driving or braking conditions.

[0029] Specifically, the vehicle motion control system continuously collects signals such as yaw rate, vehicle speed, and vertical force on all four wheels. When the yaw rate deviation exceeds a threshold and the vehicle speed reaches a set range, the system calculates the maximum lateral force on each tire based on the vertical force distribution, and simultaneously calculates the total slip ratio based on the longitudinal slip ratio and the sideslip angle. The front wheel sideslip stiffness is dynamically updated using the real-time ratio of the maximum lateral force to the total slip ratio, while the rear wheel sideslip stiffness is directly calculated based on the maximum lateral force. The front and rear axle sideslip stiffness is formed by superimposing data from each wheel, providing time-varying parameters for the control algorithm.

[0030] Compared to existing technologies, this method overcomes the hardware limitations of relying on dedicated sensors and utilizes signals from the vehicle's existing control system to achieve parameter estimation. Compared to methods that require building complex tire models, it directly calculates stiffness parameters through mechanical relationships, reducing computational complexity. For load transfer and sudden road surface changes, it improves the timeliness and accuracy of parameter estimation by updating the maximum lateral force and slip ratio in real time.

[0031] Through the above technical solution, this application achieves online real-time estimation of lateral stiffness, eliminating the data lag problem of traditional methods. It operates based on existing vehicle control system data, avoiding the increased costs associated with adding dedicated sensors. By calculating the stiffness of the front and rear wheels separately for each axle, it effectively distinguishes the mechanical characteristics of the steering wheels and drive wheels, providing more accurate parameter input for vehicle stability control. The simplified calculation process design allows the algorithm to run in real-time on the onboard controller, meeting the computational efficiency requirements of autonomous driving systems.

[0032] In some embodiments, the real-time signal includes a target yaw rate, an actual yaw rate, vehicle speed, vehicle friction coefficient, stability control indicator, four-wheel vertical force, four-wheel longitudinal slip ratio, and front and rear axle sideslip angles. When the real-time signal is acquired based on the vehicle motion control system and the maximum lateral force and total slip ratio of the four wheels are calculated, if the difference between the target yaw rate and the actual yaw rate is greater than or equal to a first preset value and the vehicle speed is greater than or equal to a second preset value, the vehicle friction coefficient is determined as the lateral friction coefficient. The maximum lateral force of the four wheels is determined based on the lateral friction coefficient, the stability control indicator, and the four-wheel vertical force. The total slip ratio of the four wheels is calculated based on the four-wheel longitudinal slip ratio and the front and rear axle sideslip angles.

[0033] The target yaw rate refers to the vehicle's desired rotational angular velocity around its vertical axis, generated through a vehicle dynamics model or driver input. The actual yaw rate refers to the vehicle's actual rotational angular velocity collected in real-time by an inertial measurement unit or sensors; the difference between the two is used to determine the vehicle's dynamic stability. The overall vehicle friction coefficient refers to the maximum adhesion coefficient between the tire and the road surface, estimated through a road surface recognition module or historical data, used to characterize current road conditions. The stability control indicator is the operating status identifier of the vehicle's electronic stability system, obtained through the controller area network bus, used to determine whether it is in active control mode. The four-wheel vertical force refers to the load perpendicular to the ground borne by the tires, calculated through suspension sensors or a dynamics model, used to determine the tire's lateral force limit. The four-wheel longitudinal slip ratio refers to the degree of slippage between the tire's rolling direction and the vehicle's traveling direction, calculated through wheel speed sensors and the difference between wheel speed and vehicle speed, used to characterize the tire's longitudinal dynamic state. The front and rear axle slip angles are the angles between the velocity directions of the front and rear axle center points and the vehicle's longitudinal axis, estimated through a kinematic model or state observer, used to characterize the degree of tire lateral deformation.

[0034] Specifically, when the difference between the target and actual yaw rate exceeds a first preset value (e.g., 0.5 rad / s) and the vehicle speed exceeds a second preset value (e.g., 15 km / h), it indicates that the vehicle is in an unstable state with sufficient dynamic excitation. In this case, the overall vehicle friction coefficient is directly used as the lateral friction coefficient. Based on this lateral friction coefficient, the vehicle is judged to be in an electronic stability system intervention state in conjunction with the stability control indicator: when the stability control indicator is invalid, the maximum lateral force of the front wheels is calculated by multiplying the vertical force of each wheel by the friction coefficient, and the maximum lateral force of the rear wheels is dynamically adjusted according to the rear axle load distribution; when the stability control indicator is valid, the maximum lateral force of the rear wheels is directly taken as the vertical force value. The total slip ratio of the four wheels is calculated by vector synthesis of the longitudinal slip ratio of each wheel and the corresponding axle slip angle. The front axle uses the fourth and fifth preset values ​​(e.g., 0.9 and 1.1) as weighting coefficients, and the rear axle uses the sixth and seventh preset values ​​(e.g., 0.8 and 1.2) for proportional adjustment. Finally, the total slip ratio of each wheel is obtained by square root operation.

[0035] Existing methods typically employ fixed friction coefficients or offline calibration parameters, which cannot adapt to dynamically changing driving conditions. This solution, however, dynamically selects the friction coefficient calculation method by real-time monitoring of yaw rate deviation and vehicle speed threshold, and intelligently adjusts the maximum lateral force calculation logic based on the stability control system status, effectively improving parameter adaptability under different operating conditions. Furthermore, by nonlinearly fusing the longitudinal slip ratio and sideslip angle to calculate the total slip ratio, it overcomes the accuracy limitations of traditional linear superposition methods.

[0036] Through the above technical solutions, this application achieves accurate estimation of tire lateral stiffness under complex working conditions. The friction coefficient selection strategy is dynamically adjusted based on real-time vehicle state signals, avoiding estimation deviations caused by fixed parameters. Combined with the intelligent switching calculation mode of the stability control system, the calculation reliability during active control intervention is ensured. The use of a multi-dimensional data fusion method to calculate the total slip ratio significantly improves the accuracy of tire mechanical state characterization, providing accurate dynamic parameter input for vehicle motion control.

[0037] In some embodiments, when the difference between the target value and the actual value of the yaw rate is greater than or equal to a first preset value, and the vehicle speed is greater than or equal to a second preset value, the lateral friction coefficient is set to a third preset value.

[0038] The lateral friction coefficient is a quantitative parameter representing the frictional characteristics between the tire and the road surface. It can be implemented using a preset fixed value. For example, when the vehicle is not under extreme dynamic conditions, setting a third preset value of 0.8 can avoid errors in friction coefficient estimation caused by signal fluctuations or low-dynamic scenarios. The third preset value refers to a pre-set default value for the friction coefficient, which can be determined through experimental calibration or empirical data. For example, a value in the range of 0.7-0.9 is used under normal road conditions. Its purpose is to provide a benchmark reference for lateral force calculation under non-target conditions, preventing the system from failing to output effective parameters due to unmet conditions.

[0039] Specifically, when the difference between the target and actual yaw rate of the vehicle does not reach a preset threshold, or when the vehicle speed does not exceed a set lower limit, the system determines that the vehicle is not in a condition requiring precise estimation of the lateral friction coefficient. In this case, the lateral friction coefficient is forcibly set to a third preset value, such as 0.85 as the default value in normal driving scenarios. This setting eliminates the influence of dynamic parameter fluctuations on the friction coefficient calculation, ensuring that the calculation of the maximum lateral force of the four wheels always has valid input, and avoiding interruptions in subsequent lateral stiffness estimation or the generation of abnormal values ​​due to unmet operating conditions.

[0040] Existing methods often stop parameter estimation or use historical data directly under non-target operating conditions, leading to error accumulation or response delay. This solution introduces a preset friction coefficient mechanism to maintain system stability while ensuring calculation continuity, using a verified benchmark value, making it particularly suitable for scenarios where vehicles transition from low-dynamic to high-dynamic states.

[0041] Through the above technical solution, this application can still output a lateral friction coefficient that conforms to physical laws even when the vehicle does not meet specific dynamic conditions, preventing estimation failures caused by sensor noise or fluctuations in operating conditions. This solves the problem of insufficient robustness caused by reliance on real-time dynamic signals in existing technologies, ensuring the continuous and effective operation of the lateral stiffness estimation system across the entire operating range.

[0042] In some embodiments, the maximum lateral force of the four wheels includes the maximum lateral force of the left front wheel, the maximum lateral force of the right front wheel, the maximum lateral force of the left rear wheel, and the maximum lateral force of the right rear wheel; the maximum vertical force of the four wheels includes the vertical force of the left front wheel, the vertical force of the right front wheel, the vertical force of the left rear wheel, and the vertical force of the right rear wheel; determining the maximum lateral force of the four wheels based on the lateral friction coefficient, the stability control flag, and the vertical force of the four wheels includes: when the stability control flag is invalid, the maximum lateral force of the left front wheel is the product of the vertical force of the left front wheel and the lateral friction coefficient, and the maximum lateral force of the right front wheel is the product of the vertical force of the right front wheel and the lateral friction coefficient. The product of the vertical force of the front wheel and the coefficient of lateral friction. The maximum lateral force of the left rear wheel is the greater of the vertical forces of the left and right rear wheels, and the maximum lateral force of the right rear wheel is the greater of the vertical forces of the left and right rear wheels. When the stability control flag is invalid, the maximum lateral force of the left front wheel is the product of the vertical force of the left front wheel and the coefficient of lateral friction, the maximum lateral force of the right front wheel is the product of the vertical force of the right front wheel and the coefficient of lateral friction, the maximum lateral force of the left rear wheel is equal to the vertical force of the left rear wheel, and the maximum lateral force of the right rear wheel is equal to the vertical force of the right rear wheel.

[0043] The maximum lateral force of the left front wheel refers to the maximum lateral force that the left front wheel can generate under extreme conditions. Specifically, it can be calculated by multiplying the vertical force of the left front wheel by the lateral friction coefficient. This calculation method reflects the maximum adhesion between the tire and the road surface. The calculation principle for the maximum lateral force of the right front wheel is the same as that of the left front wheel, using the product of the vertical force and the friction coefficient to characterize the front wheel's lateral force limit. When stability control fails, the maximum lateral force of the left rear wheel is taken as the maximum value of the vertical forces of both rear wheels. This approach avoids estimation errors caused by insufficient load on one rear wheel. When stability control is activated, the maximum lateral force of the rear wheels is directly taken as their respective vertical forces. At this time, the vehicle is in an active control state and the load transfer effect does not need to be considered.

[0044] Specifically, when the stability control system is not engaged, the maximum lateral force of the rear wheels is calculated by selecting the maximum vertical force of the left and right rear wheels. For example, when the vehicle makes an emergency lane change causing the load to shift to one side, the vertical force of the left rear wheel may be significantly smaller than that of the right rear wheel. In this case, using the maximum vertical force of the left and right rear wheels as the benchmark for calculating the lateral force of the rear wheels can avoid underestimating the lateral force caused by load transfer. When the stability control system is activated, the lateral force of the rear wheels is directly calculated using their respective vertical forces. At this time, the vehicle is already in a controlled state, and the electronic stability program can actively adjust the wheel braking force and driving force, so there is no need to consider the impact of dynamic load distribution on the lateral force.

[0045] Traditional methods typically use fixed formulas to calculate rear wheel lateral forces without considering the influence of vehicle dynamic control states, leading to abrupt changes in lateral force estimation before and after stability control intervention. This proposed solution differentiates between stability control status states, employing a dynamic load compensation strategy when control is inactive and real-time vertical force data when control is active, thus keeping the lateral force estimation results synchronized with the actual vehicle operating state.

[0046] Through the above technical solution, this application effectively solves the problem of lateral force estimation distortion caused by load transfer under extreme conditions such as emergency obstacle avoidance. In the stage before stability control intervention, the maximum value of the rear wheel vertical force is dynamically selected to ensure the accuracy of lateral stiffness estimation. In the stage when stability control is activated, the actual vertical force data is directly used to avoid calculation logic conflicts caused by control intervention, thereby realizing continuous and reliable estimation of lateral stiffness under all working conditions.

[0047] In some embodiments, the four-wheel longitudinal slip ratio includes the longitudinal slip ratio of the left front wheel, the longitudinal slip ratio of the right front wheel, the longitudinal slip ratio of the left rear wheel, and the longitudinal slip ratio of the right rear wheel; the front and rear axle sideslip angles include the front axle sideslip angle and the rear axle sideslip angle; and the four-wheel total slip ratio includes the total slip ratio of the left front wheel, the total slip ratio of the right front wheel, the total slip ratio of the left rear wheel, and the total slip ratio of the right rear wheel. Based on the longitudinal slip ratios of the four wheels and the front and rear axle sideslip angles, the total slip ratio of the four wheels is calculated, including the values ​​of the total slip ratios of the left front wheel, right front wheel, left rear wheel, and right rear wheel according to the following formulas: The total slip ratio of the left front wheel is the square root of the sum of the product of the longitudinal slip ratio of the left front wheel and the square of the fourth preset value, and the sum of ...

[0048] The four-wheel longitudinal slip ratio refers to the degree of slippage generated by each wheel during longitudinal movement. Specifically, it can be obtained by collecting wheel speed signals from wheel speed sensors and combining them with vehicle speed, and is used to characterize the longitudinal slip state of the tire-ground contact surface.

[0049] Among them, the front and rear axle slip angles refer to the deviation angles of the center lines of the front and rear axles of the vehicle relative to the actual direction of vehicle movement. Specifically, they can be estimated by combining an inertial measurement unit or a steering angle sensor with a vehicle dynamics model, and are used to reflect the degree of lateral deformation of the tires during vehicle steering.

[0050] The total slip ratio is a composite slip index that combines longitudinal slip and lateral slip. Specifically, it is calculated by combining the longitudinal slip ratio and the sideslip angle with preset weighting coefficients to comprehensively characterize the overall slip state of the tire under complex working conditions.

[0051] The fourth, fifth, sixth, and seventh preset values ​​refer to coefficients used to adjust the contribution ratio of longitudinal slip ratio and sideslip angle to total slip ratio. They can be calibrated according to tire characteristics or vehicle dynamics parameters. For example, the fourth preset value can be a value in the range of 0.8 to 1.2, the fifth preset value can be a value in the range of 0.05 to 0.15, and the sixth and seventh preset values ​​can be kept independent of or related to the front axle coefficient, respectively.

[0052] Specifically, during vehicle movement, the total slip ratio of the left front wheel is obtained by multiplying the longitudinal slip ratio of the left front wheel by a fourth preset value, squaring the result, and adding the result of multiplying the front axle sideslip angle by a fifth preset value, squaring the result, and then taking the square root. The total slip ratio of the right front wheel uses the same calculation logic, but the input parameter is replaced with the longitudinal slip ratio of the right front wheel. For the rear wheels, the total slip ratio of the left rear wheel is obtained by taking the square root of the sum of the longitudinal slip ratio of the left rear wheel multiplied by a sixth preset value and the rear axle sideslip angle multiplied by a seventh preset value. The total slip ratio of the right rear wheel is calculated similarly using the longitudinal slip ratio of the right rear wheel. This calculation method dynamically balances the contributions of longitudinal and lateral slip through preset coefficients, enabling the total slip ratio to accurately reflect the actual slip state of the tire under combined operating conditions.

[0053] Traditional methods typically consider slip ratio in only one direction or use fixed weighting coefficients, leading to significant errors in total slip ratio estimation under coupled vehicle steering and acceleration / braking conditions. This solution introduces calibrable preset coefficients to dynamically adjust the contributions of longitudinal and lateral slip. For example, by increasing the weighting coefficient of the sideslip angle during high-speed steering, the accuracy of total slip ratio calculation is improved. Furthermore, the independent setting of these preset coefficients allows for different parameter combinations for the front and rear axles, adapting to the impact of different load distributions on tire characteristics.

[0054] Through the above technical solution, this application effectively solves the problem of tire lateral stiffness estimation deviation caused by neglecting the coupling effect of longitudinal and lateral slip in the prior art. By accurately calculating the composite slip ratio, more reliable input parameters are provided for subsequent lateral stiffness estimation, thereby improving the prediction accuracy of the vehicle dynamics model. This method does not rely on dedicated sensors and can be implemented using only signals from the vehicle's existing control system, significantly reducing computational complexity and hardware costs. Furthermore, the flexible calibration of preset coefficients enhances the algorithm's adaptability to different vehicle models and operating conditions.

[0055] In some embodiments, when the vehicle speed is greater than or equal to an eighth preset value, and the total slip ratio of the left front wheel or the total slip ratio of the right front wheel is zero, the lateral stiffness of the left front wheel is the value of the maximum lateral force of the left front wheel divided by a ninth preset value, and the lateral stiffness of the right front wheel is the value of the maximum lateral force of the right front wheel divided by a ninth preset value; when the vehicle speed is greater than or equal to the eighth preset value, and the total slip ratio of the left front wheel or the total slip ratio of the right front wheel is not zero, the lateral stiffness of the left front wheel is the value of the maximum lateral force of the left front wheel divided by the total slip ratio of the left front wheel, and the lateral stiffness of the right front wheel is the value of the maximum lateral force of the right front wheel divided by the total slip ratio of the right front wheel.

[0056] Among them, the maximum lateral force of the front wheel refers to the maximum lateral force value of the tire under the action of the ultimate lateral force. It can be calculated by multiplying the vertical force and the lateral friction coefficient. Its function is to provide a basic physical quantity for the calculation of lateral stiffness. The total slip ratio of the front wheel is a composite slip ratio index that combines the longitudinal slip ratio and the sideslip angle. It can be calculated by taking the square root of the weighted sum of squares of the longitudinal slip ratio and the front axle sideslip angle. Its function is to provide dynamic slip state input for the calculation of lateral stiffness. The ninth preset value is a minimum slip ratio substitute value set to avoid the denominator being invalid due to the total slip ratio being zero. For example, it can be set to 0.001. Its function is to ensure the numerical stability of the calculation process.

[0057] Specifically, when the vehicle speed reaches the eighth preset value (e.g., 20 km / h), the system enters the lateral stiffness estimation mode. If the total slip ratio of the left or right front wheel is zero, it indicates that the tire is in a pure rolling state. In this case, the ninth preset value is used as the lower limit of the slip ratio for division to avoid calculation failure due to a zero denominator. If the total slip ratio is not zero, the lateral stiffness is calculated directly using the ratio of the maximum lateral force to the total slip ratio. In this case, the total slip ratio truly reflects the tire's slip state, resulting in a more accurate calculation. This calculation logic implements branch processing through a conditional judgment mechanism, ensuring both calculation stability under extreme conditions and calculation accuracy under normal conditions.

[0058] Compared to existing technologies, traditional methods often employ fixed thresholds or linear interpolation under low slip ratio conditions, resulting in limited estimation accuracy. This solution introduces a minimum substitution value and a dynamic slip ratio judgment mechanism, effectively improving estimation accuracy in the low slip ratio range while ensuring computational stability. Furthermore, existing technologies typically use a single calculation model, while this solution achieves adaptive switching of the calculation model through dual judgments of vehicle speed threshold and slip ratio state, significantly enhancing the algorithm's adaptability to different driving conditions.

[0059] Through the above technical solution, this application solves the problem of unstable estimation of lateral stiffness under low slip ratio conditions in the prior art, effectively avoiding calculation failure caused by a zero denominator, and improving estimation accuracy by dynamically selecting the calculation model. This method does not rely on dedicated sensors and can be implemented using only conventional signals from the vehicle motion control system, significantly reducing hardware costs. It also has low computational complexity, meets real-time requirements, and provides reliable lateral stiffness parameter input for vehicle stability control.

[0060] This application further proposes that when the vehicle speed is less than the eighth preset value, the lateral stiffness of the left front wheel and the lateral stiffness of the right front wheel be set to the tenth preset value respectively.

[0061] The eighth preset value refers to the vehicle speed threshold used to determine whether the vehicle is in a low-speed state. This threshold can be determined through experiments or vehicle dynamics models, and could be, for example, 20 km / h. This threshold is used to distinguish the critical speed at which significant changes in vehicle dynamic characteristics occur. When the vehicle speed is below this value, the linear relationship between tire lateral force and slip ratio tends to stabilize, and a fixed value is used to simplify calculations. The tenth preset value refers to a preset lateral stiffness benchmark value, which can be determined using historical data or calibration experiments, such as empirical values ​​or vehicle factory calibration data. This preset value is used to directly replace dynamic calculations under low-speed conditions, avoiding the problem of an excessively small denominator caused by the slip ratio approaching zero, thus improving calculation stability.

[0062] Specifically, when the vehicle speed is below the eighth preset value, the system no longer dynamically calculates the lateral stiffness of the left and right front wheels based on the total slip ratio of the front wheels. Instead, it directly sets both to the tenth preset value. For example, when the vehicle speed is 15 km / h, if the eighth preset value is 20 km / h, then regardless of whether the total slip ratio of the left or right front wheels is zero, the lateral stiffness of both the left and right front wheels is assigned the tenth preset value. This preset value can be obtained through offline testing, such as measuring the average ratio of tire lateral force to slip angle under low-speed steady-state conditions. Thus, the system avoids the impact of slip ratio measurement noise on lateral stiffness estimation at low speeds, while also reducing real-time computational resource consumption.

[0063] Traditional methods still rely on dynamic calculation logic at low speeds, leading to numerical instability or amplified calculation errors when the slip ratio approaches zero. For example, when the slip ratio approaches zero, the denominator term in the lateral stiffness calculation formula significantly affects the accuracy of the result, even causing division by zero anomalies. This proposed solution replaces dynamic calculation with preset values, eliminating the calculation risks associated with the denominator term while maintaining estimation accuracy under low-speed conditions, and reducing reliance on high-precision sensors.

[0064] Through the above technical solution, this application effectively solves the numerical instability problem caused by the slip ratio approaching zero under low-speed conditions in existing lateral stiffness estimation methods. By replacing dynamic calculation with a preset fixed value, calculation errors caused by an excessively small denominator are avoided, thus improving the robustness of the estimation results. At the same time, this solution reduces the dependence on real-time slip ratio data, significantly reducing computational complexity while ensuring estimation accuracy, making it particularly suitable for resource-constrained scenarios in embedded systems.

[0065] This application further proposes a tire lateral stiffness estimation method based on a vehicle motion control system, including: the maximum lateral force of the rear wheels includes the maximum lateral force of the left rear wheel and the maximum lateral force of the right rear wheel; the rear wheel lateral stiffness includes the lateral stiffness of the left rear wheel and the lateral stiffness of the right rear wheel; the rear wheel lateral stiffness is calculated based on the maximum lateral force of the rear wheels, including: when the vehicle speed is greater than or equal to an eighth preset value, and the longitudinal slip ratio of the left rear wheel or the longitudinal slip ratio of the right rear wheel is zero, the lateral stiffness of the left rear wheel is the maximum lateral force of the left rear wheel divided by an eleventh preset value. The right rear wheel lateral stiffness is the value of the maximum lateral force of the right rear wheel divided by the eleventh preset value; when the vehicle speed is greater than or equal to the eighth preset value, and the longitudinal slip ratio of the left rear wheel or the longitudinal slip ratio of the right rear wheel is not satisfied, the left rear wheel lateral stiffness is the value of the maximum lateral force of the left rear wheel divided by the longitudinal slip ratio of the left rear wheel, and the right rear wheel lateral stiffness is the value of the maximum lateral force of the right rear wheel divided by the longitudinal slip ratio of the right rear wheel; when the vehicle speed is less than the eighth preset value, the left rear wheel lateral stiffness and the right rear wheel lateral stiffness are set to the twelfth preset value respectively.

[0066] The eighth preset value is the vehicle speed threshold used to determine whether the vehicle is traveling at high speed. For example, a value of 60 km / h can be used. Its function is to distinguish between low-speed and high-speed conditions where the vehicle's dynamic characteristics differ significantly. The longitudinal slip ratios of the left and right rear wheels refer to the degree of slippage generated by the rear wheels during longitudinal movement. These can be calculated using wheel speed sensors and vehicle speed signals, and are used to characterize the longitudinal force state between the tires and the road surface. The eleventh preset value is a minimal constant used to replace the denominator when the longitudinal slip ratio is zero. For example, it could be 0.001. Its function is to avoid calculation errors caused by a zero denominator. The twelfth preset value is a preset rear wheel lateral stiffness benchmark value under low-speed conditions. For example, it can be set based on historical data or calibration tests. Its function is to ensure the stability of the estimation results at low speeds.

[0067] Specifically, when the vehicle speed reaches or exceeds the eighth preset value, if the longitudinal slip ratio of the left or right rear wheel is detected to be zero, it indicates that no significant longitudinal slip has occurred in the rear wheels. In this case, the maximum lateral force of the rear wheel is divided by the eleventh preset value to avoid the mathematical error of a zero denominator, while maintaining the continuity of the lateral stiffness estimation. If the longitudinal slip ratio is not zero, the lateral stiffness is calculated directly using the ratio of the maximum lateral force of the rear wheel to the longitudinal slip ratio, thus reflecting the impact of the actual slip state on the lateral force generation capability. When the vehicle speed is below the eighth preset value, since the vehicle's dynamic response is relatively smooth, the preset twelfth value is directly used as the rear wheel lateral stiffness to avoid complex calculations and improve the system's real-time performance.

[0068] Compared to existing technologies, which typically rely on fixed parameters or offline calibration, this approach cannot dynamically adapt to sudden changes in longitudinal slip ratio or parameter variations under low-speed conditions, leading to accumulated estimation errors. Our proposed solution, however, introduces vehicle speed threshold judgment and longitudinal slip ratio state branch calculation to achieve dynamic adjustment of rear wheel lateral stiffness. This avoids mathematical calculation errors and simplifies computational complexity through low-speed preset values.

[0069] Through the above technical solution, this application can effectively solve the problem of inaccurate estimation of lateral stiffness caused by sudden changes in longitudinal slip ratio in the prior art, improve the real-time performance and accuracy of the estimation results under high-speed conditions, and maintain calculation stability by preset values ​​under low-speed conditions, thus significantly enhancing the robustness and adaptability of the vehicle motion control system.

[0070] This application further proposes a method for estimating tire lateral stiffness based on a vehicle motion control system. By taking the sum of the lateral stiffness of the left front wheel and the right front wheel as the front axle lateral stiffness, and taking the sum of the lateral stiffness of the left rear wheel and the right rear wheel as the rear axle lateral stiffness, a comprehensive evaluation of the tire lateral stiffness of the vehicle is achieved.

[0071] The front axle lateral stiffness refers to the overall ability of the vehicle's front axle to resist lateral deformation. It is specifically calculated by linearly superimposing the lateral stiffness of the left and right front wheels, reflecting the combined characteristics of the tires on both sides of the front axle. The rear axle lateral stiffness refers to the overall ability of the vehicle's rear axle to resist lateral deformation. It is also calculated by linearly superimposing the lateral stiffness of the left and right rear wheels, accurately representing the combined effect of the tires on both sides of the rear axle. The left front wheel lateral stiffness refers to the lateral force generated per unit slip angle by the left front tire. It is calculated as the ratio of the maximum lateral force of the left front tire to its total slip ratio, directly reflecting the grip characteristics of the left front tire. The calculation method for the right front wheel lateral stiffness is symmetrical to that of the left front tire. Calculating the parameters independently on both sides avoids the impact of unilateral tire anomalies on the overall assessment.

[0072] Specifically, during vehicle motion control, the lateral stiffness of the left and right front wheels is calculated independently based on their respective maximum lateral force and slip ratio. Adding these two independent parameters yields the front axle lateral stiffness, effectively reflecting the combined effect of the tires on both sides of the front axle during vehicle steering. Similarly, the lateral stiffness of the tires on both sides of the rear axle is superimposed using the same logic to form the rear axle lateral stiffness. This method of calculating and superimposing parameters wheel-by-wheel preserves the independent characteristics of each tire while providing directly usable parameters for the vehicle dynamics model through axle-level integration. For example, in model predictive control algorithms, the front and rear axle lateral stiffness can be directly used to construct the vehicle yaw dynamics equations.

[0073] In some specific implementations, the front axle lateral stiffness calculation can be dynamically accumulated using real-time updated lateral stiffness data for the left and right front wheels. For example, when slippage of the right front wheel is detected, its lateral stiffness will decrease in real time, and the front axle lateral stiffness will automatically decrease to reflect this abnormal state. The calculation of the rear axle lateral stiffness is also dynamically adaptive. When the vehicle undergoes emergency braking, causing a sudden change in the longitudinal slip ratio of the rear wheels, the rear axle lateral stiffness will be adjusted promptly through real-time updates of the parameters on both sides.

[0074] Traditional methods typically rely on axle-level parameter estimation while neglecting individual tire differences, leading to estimation errors when tire wear is uneven or unilateral adhesion conditions change. This solution employs an innovative method of calculating and superimposing parameters for each tire, maintaining computational efficiency while improving parameter accuracy. For example, in unilateral slippage conditions on icy or snowy roads, traditional axle-level estimation distributes the impact of abnormal tires across the entire axle, while this solution accurately identifies and handles abnormal tires individually, thus providing more precise dynamic parameters for the control system.

[0075] Through the above technical solution, this application effectively solves the problem of insufficient accuracy of existing lateral stiffness estimation methods in scenarios with differences in individual tire characteristics. By combining independent calculation of each tire with axle-level superposition, the independent mechanical characteristics of each tire are preserved while meeting the axle-level parameter requirements of the vehicle dynamics model. This dual calculation structure enables the control system to more accurately predict the vehicle yaw response, especially under asymmetric loads or changes in unilateral road surface adhesion, significantly improving the intervention accuracy and response speed of the vehicle stability control system.

[0076] Reference Figure 2 As shown below, the estimation method of this application will be explained with specific examples. Figure 2 The diagram shows the overall principle of the tire lateral stiffness estimation scheme based on the vehicle motion control system.

[0077] The input signals include the target yaw rate, the actual yaw rate, vehicle speed, vehicle friction coefficient, stability control indicator, vertical force of the four wheels, longitudinal slip ratio of the four wheels, and sideslip angles of the front and rear axles. First, the maximum lateral force and total slip ratio of the four wheels are calculated. The maximum lateral force and total slip ratio of the front wheels are fed to the front wheel sideslip stiffness calculation module; the maximum lateral force of the rear wheels is fed to the rear wheel sideslip stiffness calculation module. The sideslip stiffness of the four wheels and the front and rear axles are then calculated and output from the front and rear wheel sideslip stiffness calculation modules.

[0078] Reference Figure 3 As shown, Figure 3 A flowchart illustrating the specific steps for calculating the maximum lateral force and total slip ratio of the four wheels is shown. The specific calculation steps are as follows: (1) If the difference between the target and actual yaw rate is greater than the calibration value 1 and the vehicle speed is greater than the calibration value 2, then the lateral friction coefficient is equal to the vehicle friction coefficient; if not, then the lateral friction coefficient is equal to the calibration value 3.

[0079] (2) If the stability control flag is invalid, then the maximum lateral force of the left front wheel = the vertical force of the left front wheel * the lateral friction coefficient, the maximum lateral force of the right front wheel = the vertical force of the right front wheel * the lateral friction coefficient, the maximum lateral force of the left rear wheel = max(vertical force of the left rear wheel, vertical force of the right rear wheel), and the maximum lateral force of the right rear wheel = max(vertical force of the left rear wheel, vertical force of the right rear wheel); if not, then the maximum lateral force of the left front wheel = the vertical force of the left front wheel * the lateral friction coefficient, the maximum lateral force of the right front wheel = the vertical force of the right front wheel * the lateral friction coefficient, the maximum lateral force of the left rear wheel = the vertical force of the left rear wheel, and the maximum lateral force of the right rear wheel = the vertical force of the right rear wheel.

[0080] (3) Total slip ratio of the left front wheel = [(longitudinal slip ratio of the left front wheel * calibration value 4)^2 + (front axle slip angle * calibration value 5)^2]^0.5, total slip ratio of the right front wheel = [(longitudinal slip ratio of the right front wheel * calibration value 4)^2 + (front axle slip angle * calibration value 5)^2]^0.5, total slip ratio of the left rear wheel = [(longitudinal slip ratio of the left rear wheel * calibration value 6)^2 + (rear axle slip angle * calibration value 7)^2]^0.5, total slip ratio of the right rear wheel = [(longitudinal slip ratio of the right rear wheel * calibration value 6)^2 + (rear axle slip angle * calibration value 7)^2]^0.5.

[0081] Reference Figure 4 As shown, Figure 4 A flowchart illustrating the specific steps for calculating the front wheel lateral stiffness is shown below. (1) If the vehicle speed is greater than the calibrated value of 8, then it is further determined whether the total slip ratio of the left front wheel to the right front wheel is 0; If not, then the left front wheel lateral stiffness = calibrated value 10, and the right front wheel lateral stiffness = calibrated value 10.

[0082] (2) If the total slip ratio of the left front wheel to the right front wheel is 0, then the lateral stiffness of the left front wheel is the maximum lateral force of the left front wheel / the calibration value 9, and the lateral stiffness of the right front wheel is the maximum lateral force of the right front wheel / the calibration value 9. If not, then the left front wheel lateral stiffness = maximum lateral force of the left front wheel / total slip ratio of the left front wheel, and the right front wheel lateral stiffness = maximum lateral force of the right front wheel / total slip ratio of the right front wheel.

[0083] (3) Limit the lateral stiffness of the left front wheel / right front wheel. Front axle lateral stiffness = left front wheel lateral stiffness + right front wheel lateral stiffness.

[0084] Reference Figure 5 As shown, Figure 5 A flowchart illustrating the specific steps for calculating the rear wheel lateral stiffness is shown below. (1) If the vehicle speed is greater than the calibration value of 8, then it is further determined whether the total slip ratio of the left rear wheel / right rear wheel is 0; If not, then the left rear wheel lateral stiffness = calibrated value 12, and the right rear wheel lateral stiffness = calibrated value 12.

[0085] (2) If the total slip ratio of the left rear wheel to the right rear wheel is 0, then the lateral stiffness of the left rear wheel is equal to the maximum lateral force of the left rear wheel / the calibration value 11, and the lateral stiffness of the right rear wheel is equal to the maximum lateral force of the right rear wheel / the calibration value 11. If not, then the left rear wheel lateral stiffness = maximum lateral force of the left rear wheel / longitudinal slip ratio of the left rear wheel, and the right rear wheel lateral stiffness = maximum lateral force of the right rear wheel / longitudinal slip ratio of the right rear wheel.

[0086] (3) Limit the lateral stiffness of the left rear wheel / right rear wheel. The lateral stiffness of the rear axle = the lateral stiffness of the left rear wheel + the lateral stiffness of the right rear wheel.

[0087] Furthermore, embodiments of the present invention also provide a control device, including: at least one processor; and a memory storing instructions, which, when executed by the at least one processor, execute the tire lateral stiffness estimation method based on the vehicle motion control system described above.

[0088] Taking the example of a processor and memory in a control device being connected via a bus, memory, as a non-transitory computer-readable storage medium, can be used to store non-transitory software programs and non-transitory computer-executable programs. Furthermore, memory may include high-speed random access memory, and may also include non-transitory memory, such as at least one disk storage device, flash memory device, or other non-transitory solid-state storage device. In some embodiments, memory may optionally include memory remotely located relative to the control processor, and these remote memories can be connected to the controller via a network.

[0089] The non-transient software program and instructions required to implement the estimation method of the above embodiments are stored in memory. When executed by a processor, the estimation method in the above embodiments is executed, for example, the method described above is executed. Figure 1 The method steps S100 to S400, etc.

[0090] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.

[0091] Since the control device adopts all the technical solutions of the estimation method in the above embodiments, it has at least all the beneficial effects brought about by the technical solutions in the above embodiments, which will not be repeated here.

[0092] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for estimating tire lateral stiffness based on a vehicle motion control system, characterized in that, include: The vehicle motion control system acquires real-time signals of the vehicle and calculates the maximum lateral force and total slip ratio of the four wheels based on the real-time signals. Based on the maximum lateral force of the four wheels and the total slip ratio of the four wheels, obtain the maximum lateral force of the front wheel, the total slip ratio of the front wheel, and the maximum lateral force of the rear wheel; The front wheel lateral stiffness is calculated based on the maximum lateral force of the front wheel and the total slip ratio of the front wheel, and the rear wheel lateral stiffness is calculated based on the maximum lateral force of the rear wheel. The front and rear axle lateral stiffnesses are calculated based on the front wheel lateral stiffness and the rear wheel lateral stiffness. The front wheel lateral stiffness, the rear wheel lateral stiffness, and the front and rear axle lateral stiffnesses are used to evaluate the tire lateral stiffness of the vehicle. The real-time signals include the target value of yaw rate, the actual value of yaw rate, vehicle speed, vehicle friction coefficient, stability control indicator, vertical force of four wheels, longitudinal slip ratio of four wheels, and side slip angle of front and rear axles. The process of acquiring real-time signals from the vehicle based on the vehicle motion control system, and calculating the maximum lateral force and total slip ratio of the four wheels based on the real-time signals, includes: When the difference between the target value and the actual value of the yaw rate is greater than or equal to the first preset value, and the vehicle speed is greater than or equal to the second preset value, the vehicle friction coefficient is determined as the vehicle's lateral friction coefficient. The maximum lateral force of the four wheels is determined based on the lateral friction coefficient, the stability control flag, and the vertical force of the four wheels. The total slip ratio of the four wheels is calculated based on the longitudinal slip ratio of the four wheels and the front and rear axle slip angles.

2. The tire lateral stiffness estimation method based on a vehicle motion control system according to claim 1, characterized in that, The method of acquiring real-time signals of the vehicle based on the vehicle motion control system, and calculating the maximum lateral force and total slip ratio of the four wheels of the vehicle based on the real-time signals, further includes: When the difference between the target value and the actual value of the yaw rate is greater than or equal to the first preset value, and the vehicle speed is greater than or equal to the second preset value, the lateral friction coefficient is set to the third preset value.

3. The tire lateral stiffness estimation method based on a vehicle motion control system according to claim 1 or 2, characterized in that, The maximum lateral force of the four wheels includes the maximum lateral force of the left front wheel, the maximum lateral force of the right front wheel, the maximum lateral force of the left rear wheel, and the maximum lateral force of the right rear wheel; the vertical force of the four wheels includes the vertical force of the left front wheel, the vertical force of the right front wheel, the vertical force of the left rear wheel, and the vertical force of the right rear wheel. The step of determining the maximum lateral force of the four wheels based on the lateral friction coefficient, the stability control flag, and the vertical force of the four wheels includes: When the stability control flag is invalid, the maximum lateral force of the left front wheel is the product of the vertical force of the left front wheel and the lateral friction coefficient; the maximum lateral force of the right front wheel is the product of the vertical force of the right front wheel and the lateral friction coefficient; the maximum lateral force of the left rear wheel is the largest of the vertical forces of the left rear wheel and the right rear wheel; and the maximum lateral force of the right rear wheel is the largest of the vertical forces of the left rear wheel and the right rear wheel. When the stability control flag is invalid, the maximum lateral force of the left front wheel is the product of the vertical force of the left front wheel and the lateral friction coefficient, the maximum lateral force of the right front wheel is the product of the vertical force of the right front wheel and the lateral friction coefficient, the maximum lateral force of the left rear wheel is equal to the vertical force of the left rear wheel, and the maximum lateral force of the right rear wheel is equal to the vertical force of the right rear wheel.

4. The tire lateral stiffness estimation method based on a vehicle motion control system according to claim 1, characterized in that, The four-wheel longitudinal slip ratio includes the longitudinal slip ratio of the left front wheel, the longitudinal slip ratio of the right front wheel, the longitudinal slip ratio of the left rear wheel, and the longitudinal slip ratio of the left rear wheel; the front and rear axle sideslip angles include the front axle sideslip angle and the rear axle sideslip angle; the four-wheel total slip ratio includes the total slip ratio of the left front wheel, the total slip ratio of the right front wheel, the total slip ratio of the left rear wheel, and the total slip ratio of the right rear wheel; The calculation of the total slip ratio of the four wheels based on the longitudinal slip ratio of the four wheels and the front and rear axle slip angles includes: The values ​​of the total slip ratio of the left front wheel, the total slip ratio of the right front wheel, the total slip ratio of the left rear wheel, and the total slip ratio of the right rear wheel are calculated according to the following formulas: The total slip ratio of the left front wheel = [(longitudinal slip ratio of the left front wheel * fourth preset value)^2 + (front axle sideslip angle * fifth preset value)^2]^0.5; The total slip ratio of the right front wheel = [(longitudinal slip ratio of the right front wheel * fourth preset value)^2 + (front axle sideslip angle * fifth preset value)^2]^0.5; The total slip ratio of the left rear wheel = [(longitudinal slip ratio of the left rear wheel * sixth preset value)^2 + (rear axle slip angle * seventh preset value)^2]^0.5; The total slip ratio of the right rear wheel is calculated as follows: [(longitudinal slip ratio of the right rear wheel * sixth preset value)^2 + (rear axle slip angle * seventh preset value)^2]^0.

5.

5. The tire lateral stiffness estimation method based on a vehicle motion control system according to claim 1, characterized in that, The maximum lateral force of the front wheels includes the maximum lateral force of the left front wheel and the maximum lateral force of the right front wheel; the total slip ratio of the front wheels includes the total slip ratio of the left front wheel and the total slip ratio of the right front wheel; the lateral stiffness of the front wheels includes the lateral stiffness of the left front wheel and the lateral stiffness of the right front wheel. The calculation of the front wheel lateral stiffness based on the maximum lateral force of the front wheel and the total slip ratio of the front wheel includes: When the vehicle speed is greater than or equal to the eighth preset value, and the total slip ratio of the left front wheel or the total slip ratio of the right front wheel is zero, the lateral stiffness of the left front wheel is the value of the maximum lateral force of the left front wheel divided by the ninth preset value, and the lateral stiffness of the right front wheel is the value of the maximum lateral force of the right front wheel divided by the ninth preset value. When the vehicle speed is greater than or equal to the eighth preset value, and the total slip ratio of the left front wheel or the total slip ratio of the right front wheel is zero, the lateral stiffness of the left front wheel is the value of the maximum lateral force of the left front wheel divided by the total slip ratio of the left front wheel, and the lateral stiffness of the right front wheel is the value of the maximum lateral force of the right front wheel divided by the total slip ratio of the right front wheel.

6. The tire lateral stiffness estimation method based on a vehicle motion control system according to claim 5, characterized in that, The calculation of the front wheel lateral stiffness based on the maximum lateral force of the front wheel and the total slip ratio of the front wheel also includes: When the vehicle speed is less than the eighth preset value, the left front wheel lateral stiffness and the right front wheel lateral stiffness are respectively set to the tenth preset value.

7. The tire lateral stiffness estimation method based on a vehicle motion control system according to claim 1, characterized in that, The maximum lateral force of the rear wheels includes the maximum lateral force of the left rear wheel and the maximum lateral force of the right rear wheel; the lateral stiffness of the rear wheels includes the lateral stiffness of the left rear wheel and the lateral stiffness of the right rear wheel; The calculation of the rear wheel lateral stiffness based on the maximum lateral force of the rear wheel includes: When the vehicle speed is greater than or equal to the eighth preset value, and the longitudinal slip ratio of the left rear wheel or the longitudinal slip ratio of the right rear wheel is zero, the lateral stiffness of the left rear wheel is the value of the maximum lateral force of the left rear wheel divided by the eleventh preset value, and the lateral stiffness of the right rear wheel is the value of the maximum lateral force of the right rear wheel divided by the eleventh preset value. When the vehicle speed is greater than or equal to the eighth preset value, and the longitudinal slip ratio of the left rear wheel or the longitudinal slip ratio of the right rear wheel is zero, the lateral stiffness of the left rear wheel is the value of the maximum lateral force of the left rear wheel divided by the longitudinal slip ratio of the left rear wheel, and the lateral stiffness of the right rear wheel is the value of the maximum lateral force of the right rear wheel divided by the longitudinal slip ratio of the right rear wheel. When the vehicle speed is less than the eighth preset value, the left rear wheel lateral stiffness and the right rear wheel lateral stiffness are respectively set to the twelfth preset value.

8. The tire lateral stiffness estimation method based on a vehicle motion control system according to claim 1, characterized in that, The front and rear axle lateral stiffness includes the front axle lateral stiffness and the rear axle lateral stiffness; the front wheel lateral stiffness includes the left front wheel lateral stiffness and the right front wheel lateral stiffness; the rear wheel lateral stiffness includes the left rear wheel lateral stiffness and the right rear wheel lateral stiffness. The calculation of the front and rear axle lateral stiffness based on the front wheel lateral stiffness and the rear wheel lateral stiffness includes: The front axle lateral stiffness is the sum of the left front wheel lateral stiffness and the right front wheel lateral stiffness; The rear axle lateral stiffness is the sum of the left rear wheel lateral stiffness and the right rear wheel lateral stiffness.

9. A control device, characterized in that, include: At least one processor; And a memory storing instructions that, when executed by at least one processor, perform the tire lateral stiffness estimation method based on a vehicle motion control system as described in any one of claims 1 to 8.

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