Method for indirectly measuring side slip angle of tire during running of vehicle on wet land

Abstract

The invention discloses an indirect measurement method for a tire slip angle in the process of driving a vehicle on a wet land. The method comprises the following steps: S1, measuring partial size parameters of the vehicle and position parameters of a GPS (Global Positioning System) mounting point relative to each wheel position; s2, motion state parameters of the vehicle and the tires in the running process are collected; s3, calculating the longitudinal speed Vx, ij and the lateral speed Vy, ij of the tire center position under the vehicle body coordinate system by using the position parameters and the motion state parameters and considering the influence of vehicle yawing, pitching motion and roll motion; s4, calculating a side slip angle # imgabs0 # of the tire under a vehicle body coordinate system by using the longitudinal speed Vx, ij and the lateral speed Vy, ij; S5, converting the side slip angle # imgabs1 # into a tire coordinate system by using a tire steering angle, and obtaining a side slip angle alpha ij of each wheel position under the tire coordinate system. According to the method, the influence of vehicle yawing, side tipping and pitching motion is considered, and the method has very high tire slip angle measurement precision under the vehicle wetland driving working condition and the real vehicle limiting working condition including sudden turning and sudden acceleration and deceleration at the same time.

Description

Technical Field

[0001] The invention relates to the technical field of tire testing, and in particular to a method for indirectly measuring the tire side slip angle of a vehicle when it is running on wet land. Background Art

[0002] In the study of vehicle handling performance, tire slip characteristics are one of the most important factors. The relationship between tire slip angle and lateral force directly affects the vehicle's driving stability, steering response and extreme handling ability.

[0003] There are currently two main methods for measuring tire slip angle in the industry:

[0004] 1. The direct measurement method based on optical sensors is to directly measure the longitudinal and lateral speeds of the tire through optical sensors installed at the wheel position, thereby calculating the tire slip angle. For example, Kisler's dual-axial speed optical sensor SFⅡ.

[0005] Although the direct measurement method based on optical sensors can provide relatively accurate data, it is highly sensitive to the environment. Especially on complex roads such as wet and flooded roads and unpaved roads, optical sensors are easily polluted by the environment, resulting in reduced accuracy in side slip angle measurement. At the same time, the cost of optical equipment is also relatively high.

[0006] 2. The state estimation method based on the dynamic model uses the collected vehicle motion state parameters and vehicle dynamics model, and adopts state estimation methods such as Kalman filtering and sliding mode observation to predict the tire side slip angle. It is mainly used in the field of vehicle stability control.

[0007] Although the state estimation method based on the dynamic model does not require expensive optical equipment, it is limited by the simplification of the dynamic model and the convergence speed of the estimation method. On the one hand, the simplified vehicle dynamics model may not fully reflect all dynamic changes in the actual situation; on the other hand, when encountering extreme conditions of the actual vehicle such as severe acceleration and deceleration or fast turning, the convergence speed of the state estimation algorithm may slow down or even fail, thus affecting the accuracy of the final result.

[0008] In summary, when a vehicle is driving on a wet or flooded road, the traditional direct measurement method of the tire slip angle based on optical equipment is easily disturbed, resulting in an increase in the measurement error of the slip angle; and the state estimation method based on the dynamic model often only considers the yaw motion of the vehicle in its dynamic model, ignoring the influence of the pitch and roll motion of the vehicle under extreme conditions. At the same time, it is limited by the convergence speed of the estimation method, and the measurement error of the tire slip angle under extreme conditions will increase significantly, which is insufficient in accuracy when applied to the tire performance development process.

[0009] It can be seen that it is still difficult to accurately obtain the tire's sideslip angle under the complex working conditions of real vehicles in wetlands. In view of the needs of wetland handling performance development of tires and high-precision stability control of vehicles, it is particularly urgent to study a high-precision and high-reliability tire sideslip angle measurement method. Summary of the invention

[0010] The technical problem to be solved by the present invention is how to develop a high-precision and high-reliability indirect measurement method of the tire side slip angle of a vehicle when it is running on wet land.

[0011] In order to solve the above technical problems, the present invention provides a method for indirectly measuring the tire side slip angle of a vehicle when driving on wet land, the method comprising the following steps:

[0012] S1. Adjust the vehicle loading to the corresponding test value, measure the vehicle's partial dimension parameters and the position parameters of the GPS installation point relative to each wheel position;

[0013] S2, collecting motion state parameters of the vehicle and tires during driving;

[0014] S3, using the position parameters and the motion state parameters, taking into account the influence of the vehicle's yaw, pitch motion, and roll motion, calculate the longitudinal velocity V of the tire center position in the vehicle body coordinate system x,ij and lateral velocity V y,ij ;

[0015] S4, using the longitudinal velocity V x,ij and the lateral velocity V y,ij Calculate the side slip angle of the tire in the vehicle body coordinate system

[0016] S5, using the tire steering angle and toe angle to adjust the side slip angle Convert to the tire coordinate system and obtain the side slip angle α of each wheel position in the tire coordinate system ij .

[0017] Furthermore, the side slip angle α of each wheel position in the tire coordinate system in S5 is ij , satisfying the formula:

[0018]

[0019]

[0020] Where:

[0021] α fl , α fr , α rl , α rr They are the tire slip angles of the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively;

[0022] δ fl ,δ fr ,δ rl ,δ rr They are the tire steering angles of the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively;

[0023] β fl , β fr , β rl , β rr are the initial toe angles of the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively;

[0024] L f and L r are the longitudinal distances from the GPS antenna installation point to the front axle and the rear axle respectively;

[0025] h is the height difference between the GPS antenna installation point and the wheel center;

[0026] W f and W r They are the front axle track and the rear axle track respectively;

[0027] V x and V y are the longitudinal and lateral velocities of the vehicle, respectively;

[0028] They are the yaw angular velocity, roll angular velocity and pitch angular velocity of the vehicle body respectively.

[0029] Furthermore, the measurement of the vehicle's dimensional parameters and the position parameters of the GPS installation point relative to each wheel position in S1 includes:

[0030] Wheelbase W i , GPS antenna installation point to the front and rear axle distance L i , the height difference h between the GPS antenna installation point and the wheel center, and the initial toe angle β of each tire ij ,in:

[0031] i=f, r in the parameter subscripts represent the front axle and rear axle respectively;

[0032] The j=l and r in the parameter subscripts represent the left and right wheels respectively;

[0033] When ij in the parameter subscript is fl, fr, ll, lr, it represents the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively;

[0034] The initial toe angle β of each tire ij Obtained through vehicle four-wheel alignment.

[0035] Furthermore, the S2 collects the motion state parameters of the vehicle and tires during driving, including:

[0036] The longitudinal velocity of the vehicle V x , lateral speed V y , yaw rate Roll angular velocity Pitch angular velocity and the tire steering angle δ ij ,in:

[0037] The longitudinal velocity V x , the lateral speed V y Collected through GPS;

[0038] The yaw rate The roll angular velocity And the pitch angular velocity The inertial measurement unit is used to collect and correct the speed difference between the GPS installation point and the wheel center;

[0039] The steering angle δ ij Collected by tire angle sensor.

[0040] Furthermore, the S3 calculates the longitudinal velocity V of the tire center position in the vehicle body coordinate system. x,ij and lateral velocity V y,ij ,include:

[0041] The longitudinal velocity V x,ij , satisfying the formula:

[0042]

[0043] Where: V x,fl 、V x,fr 、V x,rl 、V x,rr are the longitudinal speeds of the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively; the lateral speed V y,ij , satisfying the formula:

[0044]

[0045]

[0046] Where: V y,fl 、V y,fr 、V y,rl 、V y,rr They are the lateral speeds of the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively.

[0047] Furthermore, the S4 calculates the side slip angle of the tire in the vehicle body coordinate system Satisfy the formula:

[0048]

[0049] Where: V y,ij 、V x,ij are the longitudinal velocity and lateral velocity of the tire center in the vehicle body coordinate system, respectively.

[0050] Compared with the prior art, the embodiments of the present invention have the following beneficial effects:

[0051] On the one hand, the present invention does not require an optical sensor, thus avoiding the problem that the optical sensor is easily affected by the environment and causes a decrease in the measurement accuracy of the tire slip angle. It can be applied to the measurement of the tire slip angle on complex roads such as wet and flooded roads.

[0052] On the other hand, the present invention takes into account the influence of the vehicle's yaw, roll and pitch motions in measuring the tire slip angle, and has high tire slip angle measurement accuracy under actual vehicle extreme working conditions including sharp turns and rapid acceleration and deceleration. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0054] Figure 1 A flowchart of the disclosed embodiment of the present invention;

[0055] Figure 2 A schematic diagram of a vehicle kinematics model disclosed in an embodiment of the present invention;

[0056] Figure 3 A schematic diagram of a model of the influence of the roll motion on the lateral velocity disclosed in an embodiment of the present invention;

[0057] Figure 4 A schematic diagram of a model of the effect of pitching motion on longitudinal velocity disclosed in an embodiment of the present invention;

[0058] Figure 5 A curve diagram of the calculation results of the tire side slip angle under the condition of turning a circle with a constant radius disclosed in an embodiment of the present invention;

[0059] Figure 6 is a curve diagram of the calculation results of the tire side slip angle under the double lane shifting condition disclosed in the embodiment of the present invention;

[0060] Figure 7 It is a curve diagram of the calculation results of the tire slip angle under the cornering braking condition disclosed in the embodiment of the present invention. DETAILED DESCRIPTION

[0061] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0062] See also Figure 1 The present invention aims to protect an indirect measurement method of tire slip angle that can be applied to actual vehicle conditions in wetlands. By comprehensively considering the influence of vehicle yaw, roll, and pitch motion, the tire slip angle is indirectly measured based on vehicle and tire response parameters to ensure the measurement accuracy of the tire slip angle under vehicle wetland driving conditions. The method mainly includes the following steps:

[0063] Step 1: Adjust the vehicle loading to the corresponding test value, and measure the vehicle's partial dimension parameters and the position parameters of the GPS installation point relative to each wheel position.

[0064] In a further embodiment, the initial toe angle β of each tire is ij Obtained through vehicle four-wheel alignment; the parameters to be measured include wheelbase W i , GPS antenna installation point to the front and rear axle distance L i , the height difference h between the GPS antenna installation point and the wheel center, and the initial toe angle β of each tire ij , where: i=f, r in the parameter subscript represent the front axle and rear axle respectively, j=l, r in the parameter subscript represent the left wheel and right wheel respectively; that is, when ij in the parameter subscript takes fl, fr, ll, lr, it represents the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively.

[0065] It should be noted that the GPS antenna installation point should be selected on a flat position on the top of the vehicle and located at a point on the left-right symmetrical plane of the vehicle.

[0066] Step 2: Collect the motion state parameters of the vehicle and tires during driving.

[0067] In a further solution, the motion state parameters of the vehicle and tires during driving are collected, including: the longitudinal speed V of the vehicle x , lateral speed V y , yaw rate Roll angular velocity Pitch angular velocity Tire steering angle δ ij .

[0068] In this embodiment, the longitudinal and lateral speeds of the vehicle are collected using GPS, and the speed measurement results correspond to the speeds in each direction of the GPS installation point on the top of the vehicle.

[0069] Yaw rate Roll angular velocity Pitch angular velocity The inertial measurement unit is used to collect the data. The inertial measurement unit is rigidly connected to the vehicle body, and its angular velocity measurement results correspond to the angular velocity of the vehicle body in all directions.

[0070] Tire steering angle δ ij The measurement result is collected by the tire angle sensor, which is the real-time change of the tire angle relative to its initial position. Compared with the conventional method of estimating the tire angle by using the relationship between the steering wheel angle and the tire angle, the measurement result of this method includes the steering angle change caused by the suspension movement during the wheel movement, which can ensure the accuracy of the tire angle measurement after the vehicle enters the nonlinear response area.

[0071] Step 3: Using the above position parameters and motion state parameters, taking into account the influence of vehicle yaw, pitch and roll motion, calculate the longitudinal velocity V of the tire center position in the vehicle body coordinate system. x,ij and lateral velocity V y,ij .

[0072] In a further solution, the vehicle kinematic model considering the influence of yaw motion is as follows Figure 2 As shown. In the vehicle body coordinate system:

[0073] The longitudinal velocity difference between the GPS installation point and each wheel position due to yaw motion can be expressed as:

[0074]

[0075] The lateral velocity difference between the GPS installation point and each wheel position due to yaw motion can be expressed as:

[0076]

[0077] Where W i is the front or rear axle track, L i It is the longitudinal distance from the GPS antenna installation point to the front axle or rear axle.

[0078] Because the vehicle is running under extreme conditions, the body may have significant pitch or roll movement. If the height difference between the GPS antenna installation point and the wheel center is large, there will be a certain difference in the instantaneous lateral and longitudinal speeds between the two. Therefore, it is necessary to correct the longitudinal and lateral speeds of the wheel center position according to the pitch and roll angular velocity.

[0079] For the rolling motion of the vehicle body, it will cause the difference of lateral velocity at different height positions, such as Figure 3 The lateral velocity difference of the wheel center relative to the GPS installation point caused by the roll can be expressed as:

[0080]

[0081] For the pitch motion of the vehicle body, it will cause the difference of longitudinal velocity at different height positions, such as Figure 4 The longitudinal velocity difference of the wheel center relative to the GPS installation point caused by pitch can be expressed as:

[0082]

[0083] Combined with the position relationship of each wheel position relative to the GPS installation point, the longitudinal speed V of each wheel position x,ij It can be expressed as:

[0084]

[0085] Where V x,fl 、V x,fr 、V x,rl 、V x,rr are the longitudinal speeds of the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively; V x is the longitudinal velocity of the vehicle; W f and W r are the front axle track and the rear axle track respectively; j is the height difference between the GPS antenna installation point and the wheel center; and are the yaw angular velocity and pitch angular velocity of the vehicle body respectively.

[0086] Combined with the position relationship of each wheel position relative to the GPS installation point, the lateral speed V of each wheel position is y,ij It can be expressed as:

[0087]

[0088] Where V y,fl 、V y,fr 、V y,rl 、V y,rr are the lateral speeds of the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively; V y is the lateral speed of the vehicle; L f and L r are the longitudinal distances from the GPS antenna installation point to the front axle and the rear axle respectively; h is the height difference between the GPS antenna installation point and the wheel center; and are the yaw angular velocity and roll angular velocity of the vehicle body respectively.

[0089] Step 4: Use the calculated longitudinal velocity V x,ij and lateral velocity V y,ij , further calculate the side slip angle of the tire in the body coordinate system Satisfy the formula:

[0090]

[0091] Where V x,ij 、V y,ij are the longitudinal velocity and lateral velocity of the tire center in the vehicle body coordinate system, respectively.

[0092] Step 5: Use the tire steering angle and toe angle to adjust the side slip angle Convert to the tire coordinate system and obtain the side slip angle α of each wheel position in the tire coordinate system ij .

[0093] In a further solution, since the tire angle measurement is the change in the tire angle relative to its initial position, if the vehicle has a toe angle in the initial positioning, the initial toe angle β needs to be used. ij Correct the tire steering angle.

[0094] The calculation formula for the left wheel slip angle is:

[0095]

[0096] The calculation formula for the right wheel slip angle is:

[0097]

[0098] In the formula, α fl , α fr , α rl , α rr are the tire slip angles of the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively; δ fl ,δ fr ,δ rl ,δ rr are the tire steering angles of the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively; β fl , β fr , β rl , β rr are the initial toe angles of the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively; L f and L r are the longitudinal distances from the GPS antenna installation point to the front axle and the rear axle respectively; W f and W r V is the front axle track and the rear axle track respectively; x is the vehicle longitudinal velocity, V yis the lateral speed of the vehicle; h is the height difference between the GPS antenna installation point and the wheel center; They are the yaw angular velocity, roll angular velocity and pitch angular velocity of the vehicle body respectively.

[0099] In order to verify the accuracy of the method provided by the present invention, this embodiment performs simulation verification on it, and the process and results are as follows:

[0100] The vehicle dynamics simulation software Carsim is used to perform vehicle simulation under multiple working conditions. The vehicle motion parameters and dimensional parameters required for calculation by this method are extracted from the model. The tire slip angle is calculated indirectly using this method and then compared with the tire slip angle directly output by Carsim (the left front wheel slip angle is selected for comparison here) to verify the reliability of this method under various working conditions.

[0101] The test conditions include: fixed radius circle condition, double lane change condition, and curve braking condition.

[0102] The road friction coefficient was set to 0.65 to simulate a wet asphalt road.

[0103] Working condition 1: Fixed radius circle working condition

[0104] The vehicle starts to slowly accelerate from a stop (the acceleration is very small, close to steady state), travels around a circular track with a radius of 60m, and accelerates until the vehicle can no longer stay on the track. The simulation results are as follows: Figure 5 shown.

[0105] It can be seen that under the condition of constant radius circular driving, the tire slip angle error obtained by this method is very small from the linear region to the nonlinear region of the vehicle response, and the root mean square error (RMSE) is 0.015°, which is almost negligible compared with the theoretical value.

[0106] Working condition 2: Double lane shifting working condition

[0107] The vehicle was tested for double lane change at a speed of 80 km / h, with a lane offset of 3.5 m and a maximum lateral acceleration of about 0.6 g. The main purpose was to investigate the measurement accuracy of the tire slip angle in the nonlinear region of the vehicle. The simulation results are shown in Figure 2. Figure 6 shown.

[0108] It can be seen that during the double lane change process, the tire's slip angle reaches 7.5°, and the vehicle is completely operating in the nonlinear region during lane change. However, the root mean square error between the tire slip angle obtained by this method and the theoretical value is 0.041°, and the slip angle measurement accuracy is relatively high.

[0109] Condition 3: Corner braking condition

[0110] The vehicle is traveling along a curve at a speed of 80 km / h. At a certain moment, it starts braking and the speed drops from 80 km / h to 10 km / h. The main purpose is to investigate the measurement accuracy of the tire slip angle under the extreme conditions of turning and braking. The simulation results are shown in Figure 2. Figure 7 shown.

[0111] It can be seen that during the cornering braking process, the tire slip angle has exceeded 20°, indicating that the tires of the vehicle have slipped significantly during the test. Figure 7 It can be seen that the root mean square error of the tire slip angle obtained by this method is only 0.041° compared with the theoretical value, and the maximum error occurs in the low-speed area. The slip angle error at the moment of large slip is very small, indicating that this method still has good measurement accuracy under extreme conditions that include both turning and braking.

[0112] Based on the verification results under various working conditions of the comprehensive experiment, the tire slip angle indirect measurement method proposed in the present invention can accurately obtain the tire slip angle of the vehicle when the vehicle is undergoing complex actual vehicle testing on a wet ground.

[0113] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for indirect measurement of tire slip angle of a vehicle while driving on wet land, characterized in that: The method comprises the following steps: S1. Adjust the vehicle loading to the corresponding test value, measure the vehicle's partial dimension parameters and the position parameters of the GPS installation point relative to each wheel position; S2, collecting motion state parameters of the vehicle and tires during driving; S3, using the position parameter and the motion state parameter, calculate the longitudinal velocity V of the tire center position in the vehicle body coordinate system x,ij and lateral velocity V y,ij ; S4, using the longitudinal velocity V x,ij and the lateral velocity V y,ij Calculate the side slip angle of the tire in the vehicle body coordinate system S5, using the tire steering angle and toe angle to adjust the side slip angle Convert to the tire coordinate system and obtain the side slip angle α of each wheel position in the tire coordinate system ij .

2. The indirect measurement method of tire slip angle when a vehicle is running on wet land according to claim 1, characterized in that: The side slip angle α of each wheel position in the tire coordinate system in S5 ij , satisfying the formula: Where: α fl , α fr , α rl , α rr They are the tire slip angles of the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively; δ fl ,δ fr ,δ rl ,δ rr They are the tire steering angles of the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively; β fl , β fr , β rl , β rr are the initial toe angles of the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively; L f and L r are the longitudinal distances from the GPS antenna installation point to the front axle and the rear axle respectively; h is the height difference between the GPS antenna installation point and the wheel center; W f and W r They are the front axle track and the rear axle track respectively; V x and V y are the longitudinal and lateral velocities of the vehicle, respectively; They are the yaw angular velocity, roll angular velocity and pitch angular velocity of the vehicle body respectively.

3. The indirect measurement method of tire slip angle when a vehicle is running on wet land according to claim 1, characterized in that: The measurement of the vehicle's dimensional parameters and the position parameters of the GPS installation point relative to each wheel position in S1 includes: Wheelbase W i , GPS antenna installation point to the front and rear axle distance L i , the height difference h between the GPS antenna installation point and the wheel center, and the initial toe angle β of each tire ij ,in: i=f, r in the parameter subscripts represent the front axle and rear axle respectively; The j=l and r in the parameter subscripts represent the left and right wheels respectively; When ij in the parameter subscript is fl, fr, ll, lr, it represents the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively; The initial toe angle β of each tire ij Obtained through vehicle four-wheel alignment.

4. The indirect measurement method of tire slip angle when a vehicle is running on wet land according to claim 3, characterized in that: The S2 collects the motion state parameters of the vehicle and tires during driving, including: The longitudinal velocity of the vehicle V x , lateral speed V y , yaw rate Roll angular velocity Pitch angular velocity and the tire steering angle δ ij ,in: The longitudinal velocity V x , the lateral speed V y Collected through GPS; The yaw rate The roll angular velocity And the pitch angular velocity The data is collected by an inertial measurement unit and used to correct the speed difference between the GPS installation point and the wheel center; The steering angle δ ij Collected by tire angle sensor.

5. The indirect measurement method of tire slip angle of a vehicle running on wet land according to claim 4, characterized in that: S3 calculates the longitudinal velocity V of the tire center position in the vehicle body coordinate system x,ij and lateral velocity V y,ij ,include: The longitudinal velocity V x,ij , satisfying the formula: Where: V x,fl 、V x,fr 、V x,rl 、V x,rr are the longitudinal speeds of the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively; The lateral speed V y,ij , satisfying the formula: Where: V y,fi 、V y,fr 、V y,rl 、V y,rr They are the lateral speeds of the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively.

6. The indirect measurement method of tire slip angle of a vehicle running on wet land according to claim 5, characterized in that: S4 calculates the side slip angle of the tire in the vehicle body coordinate system Satisfy the formula: Where: V y,ij 、V x,ij are the longitudinal velocity and lateral velocity of the tire center in the vehicle body coordinate system, respectively.

Images