Method and device for detecting lateral stiffness of front and rear wheels of vehicle

Abstract

The invention discloses a method and device for detecting the lateral stiffness of front and rear wheels of a vehicle, and the method comprises the steps: obtaining the static parameters of the vehicle, the static parameters comprise the weight of the vehicle, the load of a front axle, the load of a rear axle, the distance between front and rear axles, and the rotational inertia of a Z-axis; according to the static parameters of the vehicle, the distances between the mass center of the vehicle and a front axle and a rear axle are calculated; according to preset vehicle control conditions, motion parameters at the vehicle mass center under different conditions are obtained; according to the motion parameters at the vehicle mass center and the distance between the vehicle mass center and a front axle and the distance between the vehicle mass center and a rear axle, the lateral force and the side slip angle of the front axle and the rear axle are calculated; and according to the lateral force and the slip angle of the front and rear shafts, respectively calculating the lateral stiffness of the front and rear wheels. According to the method and the device for detecting the lateral stiffness of the front wheel and the rear wheel of the vehicle, a new detection method is provided, high-precision lateral stiffness can be obtained, and the method and the device can be used for simplifying establishment of a vehicle model and solving the problem of low precision of partial working conditions in whole vehicle simulation.

Description

Technical Field

[0001] The present invention relates to the technical field of autonomous driving, and particularly to a method and device for detecting the lateral stiffness of the front and rear wheels of a vehicle. Background Art

[0002] With the rapid development of sensor technology, in-vehicle computers, and artificial intelligence, autonomous driving technology has become a research hotspot worldwide in the past decade. Autonomous driving integrates perception, planning, and motion control, and trajectory tracking control is a key technology among them. The main purpose of trajectory tracking is to accurately track a reference trajectory by eliminating tracking errors. Trajectory tracking control methods mainly include feedforward-feedback control, proportional-integral-derivative control, sliding mode control, etc. Among them, model predictive control has predictive characteristics, can handle multi-objective optimization and constraint problems at the same time, and has strong robustness, so it has been widely applied.

[0003] Currently, model predictive control generally uses fixed model parameters. Due to the complex and variable actual working conditions of intelligent vehicles, which are affected by various factors such as road curvature, road surface adhesion coefficient, tire lateral stiffness, and vehicle speed, this will reduce the accuracy of the model, and continuously using fixed constraints is not conducive to the control of intelligent vehicles, thus leading to a decline in the vehicle's trajectory tracking ability.

[0004] In order to meet the needs of the new market and development cycle, virtual development, virtual matching, and virtual tuning have gradually become the main means of vehicle development. The proportion of virtual simulation in vehicle development is gradually increasing, and simulation requirements for vehicle handling stability, ride comfort, and NVH (Noise, Vibration, Harshness) are gradually rising. High-precision vehicle simulation technology is the general trend. As the only component that transmits forces and torques between the vehicle and the ground, accurate modeling of its characteristics is a key link in vehicle simulation. Among them, the tire plays an important role in the simulation of vehicle handling stability, especially the lateral stiffness of the tire has a great impact on the response of the vehicle's middle position. Therefore, how to accurately detect the lateral stiffness of the wheel has become an urgent problem to be solved. Summary of the Invention

[0005] The object of the present invention is to provide a method and device for detecting the lateral stiffness of the front and rear wheels of a vehicle, which can meet the requirements of vehicle stability control and solve the problem of accurate detection of the lateral stiffness of the wheels.

[0006] According to the first aspect of the embodiments of the present invention, a method for detecting the lateral stiffness of the front and rear wheels of a vehicle is provided, including:

[0007] Obtain static parameters of the vehicle, where the static parameters include vehicle weight, front axle load, rear axle load, front and rear wheelbase, and Z-axis moment of inertia;

[0008] Calculate the distances between the vehicle's center of mass and the front and rear axles based on the static parameters of the vehicle;

[0009] Obtain the motion parameters at the vehicle's center of mass under different conditions according to the preset vehicle handling conditions;

[0010] Calculate the lateral forces and sideslip angles of the front and rear axles based on the motion parameters at the vehicle's center of mass and the distances between the vehicle's center of mass and the front and rear axles;

[0011] Calculate the cornering stiffnesses of the front and rear wheels respectively based on the lateral forces and sideslip angles of the front and rear axles.

[0012] A further improvement of the method of the present invention is that the method further includes:

[0013] Calculate the yaw angular velocity value through the two-degree-of-freedom model using the cornering stiffness values of the front and rear wheels;

[0014] Compare the calculated yaw angular velocity value with the measured yaw angular velocity value;

[0015] Wherein, if the difference between the yaw angular velocity value and the measured yaw angular velocity value is within a preset range, confirm that the cornering stiffnesses of the front and rear wheels meet the requirements.

[0016] A further improvement of the method of the present invention is that in the calculation of the yaw angular velocity value through the two-degree-of-freedom model using the cornering stiffness values of the front and rear wheels, the formula of the two-degree-of-freedom model is:

[0017]

[0018] Wherein, k1 is the cornering stiffness value of the front wheel, k2 is the cornering stiffness value of the rear wheel, is the lateral acceleration at the vehicle's center of mass, ω r is the yaw angular velocity at the vehicle's center of mass, u is the longitudinal velocity at the vehicle's center of mass, v is the lateral velocity at the vehicle's center of mass, is the yaw angular acceleration at the vehicle's center of mass, and δ is the front wheel steering angle at the vehicle's center of mass.

[0019] A further improvement of the method of the present invention is that the calculation of the distances between the vehicle's center of mass and the front and rear axles based on the static parameters of the vehicle includes:

[0020] The distance between the vehicle's center of mass and the front axle is a, and the calculation formula for a is:

[0021]

[0022] The distance between the vehicle's center of mass and the rear axle is b, and the calculation formula for b is:

[0023]

[0024] Wherein, L is the front-to-rear wheelbase of the vehicle, G is the vehicle weight, and F Z1 is the static front axle load, and F Z2 is the static rear axle load.

[0025] A further improvement of the method of the present invention lies in that, according to the preset vehicle handling conditions, the motion parameters at the vehicle's center of mass under different conditions are obtained, including:

[0026] At different set vehicle speeds, the lateral acceleration, yaw rate, longitudinal speed, lateral speed, yaw acceleration, and front wheel steering angle at the vehicle's center of mass are respectively obtained.

[0027] A further improvement of the method of the present invention lies in that the vehicle handling conditions are:

[0028] Turn the steering wheel along a preset direction to make the vehicle's lateral acceleration reach a preset value and maintain it for a preset time to obtain the motion parameters at the vehicle's center of mass.

[0029] A further improvement of the method of the present invention further includes:

[0030] Turn the steering wheel along the first steering direction to make the vehicle's lateral acceleration reach a first preset value and maintain it for a first set time to obtain the first motion parameters at the vehicle's center of mass;

[0031] Quickly return the steering wheel to the straight-ahead position and maintain it for a second set time;

[0032] Then turn the steering wheel along the second steering direction to make the vehicle's lateral acceleration reach a second preset value and maintain it for a second preset time to obtain the second motion parameters at the vehicle's center of mass; wherein, the first steering direction and the second steering direction are opposite;

[0033] Obtain the average value according to the first motion parameters and the second motion parameters at the vehicle's center of mass.

[0034] A further improvement of the method of the present invention lies in that, according to the lateral forces and sideslip angles of the front and rear axles, the cornering stiffnesses of the front and rear wheels are respectively calculated, including:

[0035] The formula for the cornering stiffness of the front wheels is:

[0036]

[0037] The formula for the cornering stiffness of the rear wheels is:

[0038]

[0039] Wherein, F Y1 is the lateral force of the front axle, and F Y2The lateral force of the rear axle, α1 is the cornering angle of the front axle, α2 is the cornering angle of the rear axle, a is the distance from the vehicle's center of mass to the front axle, b is the distance from the vehicle's center of mass to the rear axle, m is the vehicle weight, is the lateral acceleration at the vehicle's center of mass, ω r is the yaw angular velocity at the vehicle's center of mass, u is the longitudinal velocity at the vehicle's center of mass, v is the lateral velocity at the vehicle's center of mass, is the yaw angular acceleration at the vehicle's center of mass, δ is the front wheel steering angle at the vehicle's center of mass.

[0040] According to the second aspect of the embodiments of the present invention, there is provided a detection device for the lateral stiffness of the front and rear wheels of a vehicle, including:

[0041] A first acquisition module for acquiring the static parameters of the vehicle, where the static parameters include vehicle weight, front axle load, rear axle load, front and rear wheelbase, and Z-axis moment of inertia;

[0042] A first processing module for calculating the distances from the vehicle's center of mass to the front axle and the rear axle according to the static parameters of the vehicle;

[0043] A second acquisition module for acquiring the motion parameters at the vehicle's center of mass under different conditions according to the preset vehicle handling conditions,

[0044] A second processing module for calculating the lateral forces and cornering angles of the front and rear axles according to the motion parameters at the vehicle's center of mass and the distances from the vehicle's center of mass to the front axle and the rear axle;

[0045] A third processing module for calculating the lateral stiffness of the front and rear wheels respectively according to the lateral forces and cornering angles of the front and rear axles.

[0046] A further improvement of the device of the present invention is that the device further includes:

[0047] A calculation module for calculating the yaw angular velocity value through the two-degree-of-freedom model based on the lateral stiffness values of the front and rear wheels;

[0048] A comparison module for comparing the yaw angular velocity value with the measured yaw angular velocity value;

[0049] A fourth processing module for confirming that the lateral stiffness of the front and rear wheels meets the requirements if the difference between the yaw angular velocity value and the measured yaw angular velocity value is within the preset range.

[0050] According to the detection method and device for the lateral stiffness of the front and rear wheels of the vehicle provided by the present invention, a new detection method is proposed, which can obtain high-precision lateral stiffness, and can be used to simplify the establishment of the vehicle model and solve the problem of low accuracy in some working conditions in the vehicle whole vehicle simulation. Description of the Drawings

[0051] The present invention will be described in detail below with reference to the accompanying drawings via exemplary embodiments, where:

[0052] Figure 1 The flowchart showing the method for detecting the lateral stiffness of the front and rear wheels of a vehicle provided by an embodiment of the present invention is shown;

[0053] Figure 2 The flowchart showing the method for detecting the lateral stiffness of the front and rear wheels of a vehicle provided by another embodiment of the present invention is shown;

[0054] Figure 3 The structural block diagram showing the device for detecting the lateral stiffness of the front and rear wheels of a vehicle provided by an embodiment of the present invention is shown;

[0055] Figure 4 The structural block diagram showing the device for detecting the lateral stiffness of the front and rear wheels of a vehicle provided by another embodiment of the present invention is shown.

[0056] The accompanying drawings are only schematic and are not necessarily drawn to scale. In addition, they only show those parts necessary for clarifying the present invention, while other parts may be omitted or only simply mentioned. That is, in addition to the components shown in the accompanying drawings, the present invention may also include other components. Detailed Embodiments

[0057] The following specific embodiments illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Although the description of the present invention will be introduced in conjunction with preferred embodiments, this does not mean that the features of this invention are limited to this implementation manner. On the contrary, the purpose of introducing the invention in conjunction with the implementation manner is to cover other alternatives or modifications that may be extended based on the claims of the present invention. In order to provide a deep understanding of the present invention, many specific details will be included in the following description. The present invention can also be implemented without using these details. In addition, in order to avoid confusing or obscuring the key points of the present invention, some specific details will be omitted in the description. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0058] It should be noted that in this specification, similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0059] In the description of this embodiment, it should be noted that the orientation or positional relationship indicated by terms such as "upper" and "inner" is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the inventive product is usually placed during use. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the present invention.

[0060] Terms such as "first" and "second" are only used for distinguishing descriptions and cannot be construed as indicating or implying relative importance.

[0061] In the description of this embodiment, it should also be noted that unless otherwise clearly specified and defined, the terms "set", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in this embodiment can be understood according to specific situations.

[0062] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below in conjunction with the drawings.

[0063] Figure 1 The flowchart showing the method for detecting the lateral stiffness of the front and rear wheels of a vehicle provided by an embodiment of the present invention is shown.

[0064] Refer to Figure 1 , the method for detecting the lateral stiffness of the front and rear wheels of a vehicle according to an embodiment of the present invention includes:

[0065] S101. Obtain the static parameters of the vehicle, where the static parameters include the vehicle weight, front axle load, rear axle load, front and rear wheelbase, and Z-axis moment of inertia.

[0066] In this embodiment, the static parameters of the vehicle are pre-tested for subsequent further model calculations, and the vehicle can be a test vehicle. Among them, the static parameters are the data detected when the vehicle is in a static state, and the static parameters include the vehicle weight G (m = G / 9.8), the front axle load F Z1 , the rear axle load F Z2 , the front and rear wheelbase L, and the Z-axis moment of inertia I Z .

[0067] S102. Calculate the distances between the vehicle's center of mass and the front and rear axles according to the static parameters of the vehicle.

[0068] In this embodiment, according to the detected static parameters mentioned above, the distances between the vehicle's center of mass and the front axle and the rear axle are calculated respectively through formulas. Among them, the distance between the vehicle's center of mass and the front axle is a, and the calculation formula for a is:

[0069]

[0070] The distance between the vehicle's center of mass and the front axle is b, and the calculation formula for b is:

[0071]

[0072] Among them, L is the distance between the front and rear axles of the vehicle, G is the vehicle weight, F Z1 is the static front axle load, and F Z2 is the static rear axle load.

[0073] S103. According to the preset vehicle handling conditions, obtain the motion parameters at the vehicle's center of mass under different conditions.

[0074] In this embodiment, at different set vehicle speeds, the lateral acceleration, yaw rate, longitudinal speed, lateral speed, yaw acceleration, and front wheel steering angle at the vehicle's center of mass are obtained respectively. Then, in order to obtain the parameters required for each vehicle speed stage through the calculation model at each vehicle speed.

[0075] In one embodiment, the vehicle handling conditions of the present invention are: turn the steering wheel along a preset direction to make the vehicle's lateral acceleration reach a preset value and maintain it for a preset time to obtain the motion parameters at the vehicle's center of mass.

[0076] Specifically, the vehicle handling conditions are: turn the steering wheel along the first steering direction to make the vehicle's lateral acceleration reach the first preset value and maintain it for the first set time to obtain the first motion parameters at the vehicle's center of mass. Quickly return the steering wheel to the straight-ahead position and maintain it for the second set time; then turn the steering wheel along the second steering direction to make the vehicle's lateral acceleration reach the second preset value and maintain it for the second preset time to obtain the second motion parameters at the vehicle's center of mass; where the directions of the first steering and the second steering are opposite; obtain the average value according to the first motion parameters and the second motion parameters at the vehicle's center of mass.

[0077] In one example, a step input is applied to the steering wheel. When the vehicle speed is 30 Kph, the steering wheel is quickly turned to make the lateral acceleration of the vehicle reach 0.4 g, and this position is maintained for 1 - 2 seconds. At this time, the lateral acceleration, yaw rate, longitudinal speed, lateral speed, yaw acceleration, and front wheel angle at the vehicle's center of mass are respectively obtained. The steering wheel is quickly returned to the zero position, that is, the steering wheel is at the zero position, and this is maintained for 1 - 2 seconds. Then, a step input is applied to the steering wheel in the reverse direction, and the steering wheel is quickly turned to make the lateral acceleration of the vehicle reach -0.4 g, and this is maintained for 1 - 2 seconds. At this time, the lateral acceleration, yaw rate, longitudinal speed, lateral speed, yaw acceleration, and front wheel angle at the vehicle's center of mass are respectively obtained. Then, the two sets of data are averaged (that is, the values obtained from the first steering and the second steering above), and this average value is used as the motion parameters at the center of mass.

[0078] According to the same detection method, when the vehicle speeds are 60 Kph, 90 Kph, and 120 Kph respectively, the motion parameters at the center of mass are respectively obtained. Of course, in the present invention, it is not limited to these speed conditions. Other speeds can also be tested. The lateral acceleration value of the vehicle caused by the direction control is not the above - mentioned example value, and other values can also be applicable. The holding time can also be set according to actual needs, and the present application does not make specific limitations on these values.

[0079] S104. Calculate the lateral forces and sideslip angles of the front and rear axles according to the motion parameters at the vehicle's center of mass and the distances between the vehicle's center of mass and the front and rear axles.

[0080] In this embodiment, according to the motion parameters at the vehicle's center of mass obtained in the above steps and the distances between the vehicle's center of mass and the front and rear axles, the lateral forces and sideslip angles of the front and rear axles are calculated. Among them, the calculation formula for the lateral force of the front axle is:

[0081]

[0082] The calculation formula for the lateral force of the rear axle is:

[0083]

[0084] Among them, F Y1 is the lateral force of the front axle, F Y2 is the lateral force of the rear axle, a is the distance between the vehicle's center of mass and the front axle, b is the distance between the vehicle's center of mass and the rear axle, m is the vehicle mass, is the lateral acceleration at the vehicle's center of mass, ω r1 is the yaw rate at the vehicle's center of mass, u is the longitudinal speed at the vehicle's center of mass, v is the lateral speed at the vehicle's center of mass, is the yaw acceleration at the vehicle's center of mass, I Z is the moment of inertia about the Z - axis.

[0085] The calculation formula for the sideslip angle of the front axle is:

[0086] α1 = (v + ω r1 a - δu) / u

[0087] The calculation formula for the rear axle sideslip angle is:

[0088] α2 = (v - ω r1 b) / u

[0089] Where α1 is the front axle deviation angle, α2 is the rear axle deviation angle, a is the distance from the vehicle's center of mass to the front axle, b is the distance from the vehicle's center of mass to the rear axle, ω r1 is the yaw angular velocity at the vehicle's center of mass, u is the longitudinal velocity at the vehicle's center of mass, v is the lateral velocity at the vehicle's center of mass, and δ is the front wheel steering angle at the vehicle's center of mass.

[0090] S105. Calculate the cornering stiffness of the front and rear wheels respectively according to the lateral forces and sideslip angles of the front and rear axles.

[0091] In this embodiment, the cornering stiffness of the front and rear wheels is calculated respectively according to the lateral forces and sideslip angles of the front and rear axles. The formula for the cornering stiffness of the front wheel is:

[0092]

[0093] The formula for the cornering stiffness of the rear wheel is:

[0094]

[0095] Where F Y1 is the lateral force of the front axle, F Y2 is the lateral force of the rear axle, α1 is the sideslip angle of the front axle, α2 is the sideslip angle of the rear axle, a is the distance from the vehicle's center of mass to the front axle, b is the distance from the vehicle's center of mass to the rear axle, m is the vehicle mass, is the lateral acceleration at the vehicle's center of mass, ω r1 is the yaw angular velocity at the vehicle's center of mass, u is the longitudinal velocity at the vehicle's center of mass, v is the lateral velocity at the vehicle's center of mass, is the yaw angular acceleration at the vehicle's center of mass, and δ is the front wheel steering angle at the vehicle's center of mass.

[0096] Under the vehicle control conditions of the present invention, calculate the cornering stiffness of the front and rear wheels at each speed value respectively, and then obtain the final cornering stiffness k1 of the front wheel and k2 of the rear wheel by taking the average value, so as to make the obtained cornering stiffness values of the front and rear wheels more accurate.

[0097] Furthermore, as Figure 2 shown, the detection method for the cornering stiffness of the front and rear wheels of the vehicle of the present invention also verifies the calculated cornering stiffness to ensure that the cornering stiffness of the front and rear wheels meets the requirements of precision control. This method also includes:

[0098] S201. Calculate the yaw rate value through the two-degree-of-freedom model based on the cornering stiffness values of the front and rear wheels.

[0099] In this embodiment, the formula of the two-degree-of-freedom model is:

[0100]

[0101] where k1 is the cornering stiffness value of the front wheel, k2 is the cornering stiffness value of the rear wheel, is the lateral acceleration at the vehicle's center of mass, u is the longitudinal speed at the vehicle's center of mass, v is the lateral speed at the vehicle's center of mass, is the yaw acceleration at the vehicle's center of mass, and δ is the front wheel steering angle at the vehicle's center of mass.

[0102] By substituting the values of k1 and k2 into the above formula and combining with the obtained lateral acceleration at the vehicle's center of mass the longitudinal speed u at the vehicle's center of mass, the lateral speed v at the vehicle's center of mass, the yaw acceleration at the vehicle's center of mass the front wheel steering angle δ at the vehicle's center of mass, calculate the model value of ω in real time r of.

[0103] S202. Compare the calculated yaw rate value with the measured yaw rate value.

[0104] S203. If the difference between the yaw rate value and the measured yaw rate value is within the preset range, confirm that the cornering stiffness of the front and rear wheels meets the requirements.

[0105] In the above two steps, compare the calculated yaw rate value with the yaw rate value measured by the sensor. If the difference between the yaw rate value and the measured yaw rate value is within the preset range, then confirm that the cornering stiffness of the front and rear wheels meets the requirements. If the difference between the yaw rate value and the measured yaw rate value exceeds the preset range, then repeat steps 103 - 105 and steps 201 - 203 until the difference between the yaw rate value and the measured yaw rate value is within the preset range.

[0106] The present invention proposes a new detection method. By means of vehicle control conditions, obtain the motion parameters at the vehicle's center of mass under different conditions to obtain the cornering stiffness of the front and rear wheels and calculate the yaw rate value through writing the cornering stiffness values of the front and rear wheels into the two-degree-of-freedom model, and compare the yaw rate value with the detected yaw angle value so that the difference between the calculated yaw rate value and the detected yaw angle value is within the preset range, thereby high-precision cornering stiffness can be obtained, which can be used to simplify the establishment of the vehicle model and solve the problem of low accuracy in some working conditions in the vehicle whole vehicle simulation.

[0107] Such as Figure 3As shown, according to another aspect of the embodiments of the present invention, a detection device for the lateral stiffness of the front and rear wheels of a vehicle is further provided. The device includes:

[0108] A first acquisition module 301, configured to acquire static parameters of the vehicle. The static parameters include vehicle weight, front axle load, rear axle load, front and rear wheelbase, and Z-axis moment of inertia.

[0109] In this embodiment, the static parameters of the vehicle are pre-tested for subsequent further model calculations. The vehicle can be a test vehicle. Among them, the static parameters are the data detected when the vehicle is in a static state. The static parameters include vehicle weight G (m = G / 9.8), front axle load F Z1 , rear axle load F Z2 , front and rear wheelbase L, and Z-axis moment of inertia I Z .

[0110] A first processing module 302, configured to calculate the distances between the vehicle's center of mass and the front and rear axles according to the static parameters of the vehicle.

[0111] In this embodiment, according to the above-detected static parameters, the distances between the vehicle's center of mass and the front and rear axles are calculated respectively by formulas. Among them, the distance between the vehicle's center of mass and the front axle is a, and the calculation formula of a is:

[0112]

[0113] The distance between the vehicle's center of mass and the rear axle is b, and the calculation formula of b is:

[0114]

[0115] Among them, L is the front and rear wheelbase of the vehicle, G is the vehicle weight, F Z1 is the static front axle load, and F Z2 is the static rear axle load.

[0116] A second acquisition module 303, configured to acquire the motion parameters at the vehicle's center of mass under different conditions according to preset vehicle control conditions.

[0117] In this embodiment, at different set vehicle speeds, the lateral acceleration, yaw rate, longitudinal speed, lateral speed, yaw acceleration, and front wheel steering angle at the vehicle's center of mass are acquired respectively. Then, in order to obtain the parameters required for each vehicle speed stage through the calculation model at each vehicle speed.

[0118] In one embodiment, the vehicle control condition of the present invention is: turning the steering wheel along a preset direction to make the vehicle's lateral acceleration reach a preset value and maintaining it for a preset time to obtain the motion parameters at the vehicle's center of mass.

[0119] Specifically, the vehicle handling conditions are as follows: turn the steering wheel along the first steering direction to make the lateral acceleration of the vehicle reach the first preset value, and maintain it for the first set time to obtain the first motion parameter at the vehicle's center of mass. Quickly return the steering wheel to the straight-ahead position and maintain it for the second set time; then turn the steering wheel along the second steering direction to make the lateral acceleration of the vehicle reach the second preset value, and maintain it for the second set time to obtain the second motion parameter at the vehicle's center of mass; where the directions of the first steering and the second steering are opposite; obtain the average value according to the first motion parameter and the second motion parameter at the vehicle's center of mass.

[0120] The second processing module 304 is configured to calculate the lateral forces and sideslip angles of the front and rear axles according to the motion parameter at the vehicle's center of mass and the distances between the vehicle's center of mass and the front and rear axles.

[0121] In this embodiment, according to the motion parameter at the vehicle's center of mass and the distances between the vehicle's center of mass and the front and rear axles obtained in the above steps, calculate the lateral forces and sideslip angles of the front and rear axles. Among them, the calculation formula for the lateral force of the front axle is:

[0122]

[0123] The calculation formula for the lateral force of the rear axle is:

[0124]

[0125] Among them, F Y1 is the lateral force of the front axle, F Y2 is the lateral force of the rear axle, a is the distance between the vehicle's center of mass and the front axle, b is the distance between the vehicle's center of mass and the rear axle, m is the vehicle mass, is the lateral acceleration at the vehicle's center of mass, ω r1 is the yaw angular velocity at the vehicle's center of mass, u is the longitudinal velocity at the vehicle's center of mass, v is the lateral velocity at the vehicle's center of mass, is the yaw angular acceleration at the vehicle's center of mass, I Z is the moment of inertia about the Z axis.

[0126] The third processing module 305 is configured to calculate the cornering stiffnesses of the front and rear wheels respectively according to the lateral forces and sideslip angles of the front and rear axles.

[0127] In this embodiment, calculate the cornering stiffnesses of the front and rear wheels respectively according to the lateral forces and sideslip angles of the front and rear axles. The formula for the cornering stiffness of the front wheel is:

[0128]

[0129] The formula for the cornering stiffness of the rear wheel is:

[0130]

[0131] Among them, F Y1is the lateral force of the front axle, F Y2 is the lateral force of the rear axle, α1 is the side slip angle of the front axle, α2 is the side slip angle of the rear axle, a is the distance from the vehicle's center of mass to the front axle, b is the distance from the vehicle's center of mass to the rear axle, m is the vehicle mass, is the lateral acceleration at the vehicle's center of mass, ω r1 is the yaw angular velocity at the vehicle's center of mass, u is the longitudinal velocity at the vehicle's center of mass, v is the lateral velocity at the vehicle's center of mass, is the yaw angular acceleration at the vehicle's center of mass, δ is the front wheel steering angle at the vehicle's center of mass.

[0132] Under the vehicle control conditions of the present invention, the side slip stiffness of the front and rear wheels is calculated respectively at each speed value, and then the final side slip stiffness k1 of the front wheel and the side slip stiffness k2 of the rear wheel are obtained by taking the average value, so as to make the obtained side slip stiffness values of the front and rear wheels more accurate.

[0133] Furthermore, as Figure 4 shown, the detection device for the side slip stiffness of the front and rear wheels of the vehicle further includes:

[0134] A calculation module 401, configured to calculate the yaw angular velocity value through the two-degree-of-freedom model based on the side slip stiffness values of the front and rear wheels;

[0135] In this embodiment, the two-degree-of-freedom model formula is:

[0136]

[0137] where k1 is the front wheel side slip stiffness value, k2 is the rear wheel side slip stiffness value, is the lateral acceleration at the vehicle's center of mass, u is the longitudinal velocity at the vehicle's center of mass, v is the lateral velocity at the vehicle's center of mass, is the yaw angular acceleration at the vehicle's center of mass, δ is the front wheel steering angle at the vehicle's center of mass.

[0138] By substituting the values of k1 and k2 into the above formula, and combining the obtained lateral acceleration at the vehicle's center of mass the longitudinal velocity u at the vehicle's center of mass, the lateral velocity v at the vehicle's center of mass, the yaw angular acceleration at the vehicle's center of mass the front wheel steering angle δ at the vehicle's center of mass, the model value of ω r is calculated in real time.

[0139] A comparison module 402, configured to compare the yaw angular velocity value with the measured yaw angular velocity value;

[0140] A fourth processing module 403, configured to confirm that the side slip stiffness of the front and rear wheels meets the requirements if the difference between the yaw angular velocity value and the measured yaw angular velocity value is within a preset range.

[0141] In the above two modules, the calculated yaw rate value is compared with the yaw rate value measured by the sensor. If the difference between the yaw rate value and the measured yaw rate value is within the preset range, it is confirmed that the lateral stiffness of the front and rear wheels meets the requirements. If the difference between the yaw rate value and the measured yaw rate value exceeds the preset range, then steps 103 - 105 and steps 201 - 203 are performed again until the difference between the yaw rate value and the measured yaw rate value is within the preset range.

[0142] The present invention provides a method and device for detecting the lateral stiffness of the front and rear wheels of a vehicle. By the vehicle control conditions, the motion parameters at the vehicle's center of mass under different conditions are obtained to obtain the lateral stiffness of the front and rear wheels, and the yaw rate value is calculated by writing the lateral stiffness values of the front and rear wheels into a two-degree-of-freedom model. The yaw rate value is compared with the detected yaw angle value so that the difference between the calculated yaw rate value and the detected yaw angle value is within the preset range, thereby high-precision cornering stiffness can be obtained, which can be used to simplify the establishment of the vehicle model and solve the problem of low accuracy in some working conditions in the vehicle whole vehicle simulation.

[0143] Although the present invention has been illustrated and described by referring to some preferred embodiments of the present invention, those of ordinary skill in the art should understand that the above content is a further detailed description of the present invention in combination with specific embodiments, and it cannot be determined that the specific implementation of the present invention is only limited to these descriptions. Those skilled in the art can make various changes in form and details, including making several simple deductions or substitutions, without departing from the spirit and scope of the present invention.

Claims

1. A method for detecting the lateral stiffness of the front and rear wheels of a vehicle, characterized in that, Including: Obtain the static parameters of the vehicle, where the static parameters include vehicle weight, front axle load, rear axle load, front and rear wheelbase, and Z-axis moment of inertia; Calculate the distances between the vehicle's center of mass and the front and rear axles based on the static parameters of the vehicle; Obtain the motion parameters at the vehicle's center of mass under different conditions according to the preset vehicle handling conditions; Calculate the lateral forces and sideslip angles of the front and rear axles based on the motion parameters at the vehicle's center of mass and the distances between the vehicle's center of mass and the front and rear axles; Calculate the cornering stiffnesses of the front and rear wheels respectively based on the lateral forces and sideslip angles of the front and rear axles; 2. The method according to claim 1, wherein The method further includes: Calculate the yaw rate value through the two-degree-of-freedom model using the cornering stiffness values of the front and rear wheels; Compare the calculated yaw rate value with the measured yaw rate value; Wherein, if the difference between the yaw rate value and the measured yaw rate value is within the preset range, it is confirmed that the cornering stiffnesses of the front and rear wheels meet the requirements.

3. The method according to claim 2, wherein In the calculation of the yaw rate value through the two-degree-of-freedom model using the cornering stiffness values of the front and rear wheels, the formula of the two-degree-of-freedom model is: where k1 is the front wheel cornering stiffness value and k2 is the rear wheel cornering stiffness value, is the lateral acceleration at the vehicle's center of mass, ω r is the yaw angular velocity at the vehicle's center of mass, u is the longitudinal velocity at the vehicle's center of mass, v is the lateral velocity at the vehicle's center of mass, is the yaw angular acceleration at the vehicle's center of mass, and δ is the front wheel steering angle at the vehicle's center of mass.

4. The method according to claim 1, characterized in that, The calculation of the distances between the vehicle's center of mass and the front and rear axles based on the static parameters of the vehicle includes: The distance between the vehicle's center of mass and the front axle is a, and the calculation formula of a is: The distance between the vehicle's center of mass and the rear axle is b, and the calculation formula of b is: wherein, L is the wheelbase of the vehicle from front to rear, G is the weight of the vehicle, F Z1 is the static front axle load, and F Z2 is the static rear axle load.

5. The method according to claim 1, characterized in that The obtaining of the motion parameters at the vehicle's center of mass under different conditions according to the preset vehicle handling conditions includes: At different set vehicle speeds, respectively obtain the lateral acceleration, yaw rate, longitudinal speed, lateral speed, yaw acceleration, and front wheel steering angle at the vehicle's center of mass.

6. The method according to claim 5, wherein The vehicle handling conditions are: Turn the steering wheel along the preset direction to make the vehicle's lateral acceleration reach the preset value and maintain it for the preset time to obtain the motion parameters at the vehicle's center of mass.

7. The method according to claim 6, wherein Also including: Turn the steering wheel along the first steering direction to make the vehicle's lateral acceleration reach the first preset value and maintain it for the first set time to obtain the first motion parameters at the vehicle's center of mass; Quickly return the steering wheel to the straight-ahead position and maintain it for the second set time; Then turn the steering wheel along the second steering direction to make the vehicle's lateral acceleration reach the second preset value and maintain it for the second preset time to obtain the second motion parameters at the vehicle's center of mass; where the directions of the first steering and the second steering are opposite; Obtain the average value based on the first motion parameters and the second motion parameters at the vehicle's center of mass.

8. The method according to claim 1, characterized in that, The calculation of the cornering stiffnesses of the front and rear wheels respectively based on the lateral forces and sideslip angles of the front and rear axles includes: The formula for the cornering stiffness of the front wheel is: The formula for the cornering stiffness of the rear wheel is: wherein, the F Y1 is the lateral force of the front axle, the F Y2 is the lateral force of the rear axle, α1 is the cornering angle of the front axle, α2 is the cornering angle of the rear axle, a is the distance from the vehicle's center of mass to the front axle, b is the distance from the vehicle's center of mass to the rear axle, m is the vehicle weight, is the lateral acceleration at the vehicle's center of mass, ω r is the yaw rate at the vehicle's center of mass, u is the longitudinal velocity at the vehicle's center of mass, v is the lateral velocity at the vehicle's center of mass, is the yaw acceleration at the vehicle's center of mass, and δ is the front wheel steering angle at the vehicle's center of mass.

9. A detection device for the lateral stiffness of the front and rear wheels of a vehicle, characterized in that, Including: A first acquisition module for obtaining the static parameters of the vehicle, where the static parameters include vehicle weight, front axle load, rear axle load, front and rear wheelbase, and Z-axis moment of inertia; A first processing module for calculating the distances between the vehicle's center of mass and the front and rear axles based on the static parameters of the vehicle; A second acquisition module for obtaining the motion parameters at the vehicle's center of mass under different conditions according to the preset vehicle handling conditions, A second processing module for calculating the lateral forces and sideslip angles of the front and rear axles based on the motion parameters at the vehicle's center of mass and the distances between the vehicle's center of mass and the front and rear axles; A third processing module, configured to calculate the cornering stiffnesses of the front and rear wheels respectively according to the lateral forces and sideslip angles of the front and rear axles.

10. The device according to claim 9, characterized in that, The device further includes: A calculation module, configured to calculate a yaw rate value through a two-degree-of-freedom model using the cornering stiffness values of the front and rear wheels; A comparison module, configured to compare the yaw rate value with the measured yaw rate value; A fourth processing module, configured to confirm that the cornering stiffnesses of the front and rear wheels meet the requirements if the difference between the yaw rate value and the measured yaw rate value is within a preset range.

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