Method for indirect measurement of tire side slip angle in off-road vehicle travel

Abstract

The application discloses a kind of tire side slip angle indirect measurement method in vehicle wet ground driving, the method comprises: S1, measures the position parameter of vehicle partial size parameter and GPS installation point relative each wheel position;S2, acquisition vehicle and tire in driving motion state parameter;S3, using position parameter and the motion state parameter, the influence of vehicle yaw, pitch motion, roll motion is considered, the longitudinal velocity V x,ij And lateral velocity V y,ij Of tire center position under the body coordinate system is calculated;S4, using the longitudinal velocity V x,ij And the lateral velocity V y,ij The side slip angle of tire under the body coordinate system is calculated S5, using tire steering angle, the side slip angle is converted to tire coordinate system, obtains each wheel position in tire coordinate system, and the side slip angle α ij The application considers the influence of vehicle yaw, roll, pitch motion, has very high tire side slip angle measurement precision in vehicle wet ground driving condition and simultaneously containing sharp turn and sharp acceleration and deceleration extreme condition of real vehicle.

Description

Technical Field

[0001] The present 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 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 capabilities.

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

[0004] 1. Direct measurement based on optical sensors: This method uses optical sensors installed at the wheel to directly measure the longitudinal and lateral speeds of the tire, thereby calculating the tire slip angle. An example is the Kisler dual-axial speed optical sensor SFⅡ.

[0005] While direct measurement methods based on optical sensors can provide relatively accurate data, they are highly sensitive to the environment. Especially on complex road surfaces, such as wet and unpaved roads, optical sensors are easily contaminated, resulting in reduced slip angle measurement accuracy. Furthermore, optical equipment is relatively expensive.

[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] While state estimation methods based on dynamic models do not require expensive optical equipment, they are limited by the degree of 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 real world. On the other hand, when faced with extreme vehicle conditions such as rapid acceleration and deceleration or rapid cornering, the convergence speed of the state estimation algorithm may slow down or even fail, affecting the accuracy of the final results.

[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 interfered with, resulting in an increase in the slip angle measurement error; while the state estimation method based on the dynamic model often only considers the vehicle's yaw motion in its dynamic model, ignoring the influence of the vehicle's pitch and roll motion under extreme working conditions. At the same time, due to the limitation of the convergence speed of the estimation method, the measurement error of the tire slip angle will increase significantly under extreme working conditions, and its accuracy is insufficient when applied to the process of tire performance development.

[0009] It can be seen that it is still difficult to accurately obtain the tire's side slip angle under the complex wetland working conditions of real vehicles. In view of the needs of developing the tire's wetland handling performance and high-precision stability control of the vehicle, it is particularly urgent to study a high-precision and high-reliability tire side slip 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 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 dimensional 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, and roll motions, 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 tire's side slip angle 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 and rear axles 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] 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 , Distance from GPS antenna installation point to front and rear axles (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] The i=f and r in the parameter subscripts represent the front and rear axles, respectively;

[0032] The parameter subscripts j=l and r 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] longitudinal speed V of the vehicle x lateral speed V y yaw angular speed roll angular speed pitch angular speed and steering angle δ of the tire ij wherein:

[0037] the longitudinal speed V x the lateral speed V y is collected by GPS;

[0038] the yaw angular speed the roll angular speed and the pitch angular speed is collected by an inertial measurement unit, for correcting the speed difference between the GPS installation point and the wheel center;

[0039] the steering angle δ ij is collected by a tire steering angle sensor.

[0040] Further, the S3 calculates the longitudinal speed V x,ij and the lateral speed V y,ij of the tire center position in the vehicle body coordinate system, comprising:

[0041] the longitudinal speed V x,ij satisfies the formula:

[0042]

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

[0044]

[0045]

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

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

[0048]

[0049] Where: V y,ij 、V x,ij are the longitudinal velocity and lateral velocity of the tire center position 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 tire side slip angle measurement accuracy. It can be applied to the tire side slip angle measurement on complex roads such as wet and flooded roads.

[0052] On the other hand, the present invention takes into account the influence of vehicle yaw, roll, and pitch motions in the measurement of tire slip angles, and has high tire slip angle measurement accuracy under real vehicle extreme operating 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 kinematic model disclosed in an embodiment of the present invention;

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

[0057] Figure 4 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 graph showing the calculation results of the tire slip angle under the constant radius circular working condition disclosed in an embodiment of the present invention;

[0059] Figure 6 A graph showing calculation results of tire slip angles under a double lane-shifting condition disclosed in an embodiment of the present invention;

[0060] Figure 7 This is a graph showing the calculation results of the tire slip angle under the cornering braking condition disclosed in an embodiment of the present invention. DETAILED DESCRIPTION

[0061] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of 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. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0062] See also Figure 1 The present invention aims to protect a method for indirectly measuring tire slip angles that can be applied to actual vehicle operating conditions in wetlands. By comprehensively considering the effects of vehicle yaw, roll, and pitch motions, the method indirectly measures tire slip angles based on vehicle and tire response parameters, thereby ensuring the measurement accuracy of tire slip angles under 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 dimensional 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 , Distance from GPS antenna installation point to front and rear axles (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 subscripts represent the front axle and rear axle respectively, j=l, r in the parameter subscripts represent the left wheel and right wheel respectively; that is, when ij in the parameter subscripts takes fl, fr, ll, lr, they represent 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 angular velocity 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 angular velocity Roll angular velocity Pitch angular velocity The angular velocity is collected by an inertial measurement unit (IMU). The IMU 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 collected by the tire angle sensor is the real-time change in tire angle relative to its initial position. Compared with the conventional method of estimating tire angle based on the relationship between steering wheel angle and tire angle, the measurement result of this method includes the steering angle change caused by suspension movement during wheel movement, which can ensure the accuracy of 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 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 .

[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] When a vehicle is operating under extreme conditions, the vehicle body may experience significant pitch or roll motion. If the height difference between the GPS antenna installation point and the wheel center is large, there will also be a certain difference in the instantaneous lateral and longitudinal velocities between the two. Therefore, the longitudinal and lateral velocities at the wheel center position need to be corrected based on the pitch and roll angular velocities.

[0079] For the rolling motion of the vehicle body, it will cause the difference of lateral velocity relative to 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 pitching 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 velocities 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 rate and pitch rate 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 velocities 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 and rear axles, 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 vehicle body coordinate system Satisfies the formula:

[0090]

[0091] Where V x,ij 、V y,ij are the longitudinal velocity and lateral velocity of the tire center position 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 rotation angle is measured relative to the change in 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] Where, 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 and rear axles respectively; W f and W r Respectively front axle track and rear axle track; V 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; 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 has carried out simulation verification, and the process and results are as follows:

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

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

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

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

[0104] The vehicle starts from a stop and slowly accelerates (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 fixed radius circular working condition, the tire side slip angle error obtained by this method is very small from the linear region to the nonlinear region of the vehicle response. The root mean square error (RMSE) is 0.015°, and the error with the theoretical value is almost negligible.

[0106] Working condition 2: Double lane change 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 approximately 0.6 g. The main purpose was to examine the measurement accuracy of the tire slip angle in the vehicle nonlinear region. 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 operating completely in the nonlinear region during the lane change. However, the root mean square error of the tire slip angle obtained by this method and the theoretical value is 0.041°, indicating high slip angle measurement accuracy.

[0109] Condition 3: Cornering braking condition

[0110] The vehicle travels along the curve at a speed of 80km / h, and starts braking at a certain moment, and the vehicle speed decreases from 80km / h to 10km / h. The measurement accuracy of the tire side slip angle in the extreme working condition containing turning and braking at the same time is mainly investigated, and the simulation result is as shown in Figure 7

[0111] It can be seen that the tire side slip angle has exceeded 20° during the curve braking process, indicating that the tire has undergone significant slip during the test process. However, it can be seen from Figure 7 that the tire side slip angle error obtained by the method and the root mean square error of the theoretical value are only 0.041°, and the maximum error occurs in the low-speed area, and the side slip angle error at the large slip moment is very small, indicating that the method still has good measurement accuracy in the extreme working condition containing turning and braking at the same time.

[0112] According to the verification results of various working conditions in the experiment, the tire side slip angle indirect measurement method proposed by the application can accurately obtain the tire side slip angle of the vehicle during the complex real vehicle test on the wet ground.

[0113] Although the embodiments of the application have been shown and described, it can be understood by those of ordinary skill in the art that various changes, modifications, replacements and variations can be made to the embodiments without departing from the principles and spirits of the application, and the scope of the application is defined by the appended claims and their equivalents.​

Claims

1. A method for indirectly measuring the 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 dimensional 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 parameters and the motion state parameters to calculate the longitudinal velocity of the tire center position in the vehicle body coordinate system and lateral speed ; S4, using the longitudinal speed and the lateral velocity Calculate the tire's side slip angle 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 to obtain the side slip angle of each wheel position in the tire coordinate system , which satisfies the formula: Where: 、 、 They are the tire slip angles of the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively; 、 、 They are the tire steering angles of the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively; 、 、 are the initial toe angles of the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively; and are the longitudinal distances from the GPS antenna installation point to the front and rear axles respectively; is the height difference between the GPS antenna installation point and the wheel center; and They are the front axle track and the rear axle track respectively; and are the longitudinal and lateral velocities of the vehicle, respectively; 、 are the yaw angular velocity, roll angular velocity, and pitch angular velocity of the vehicle body respectively.

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 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 , Distance from GPS antenna installation point to front and rear axles , the height difference between the GPS antenna installation point and the wheel center and the initial toe angle of each tire ,in: Parameter subscript Represent the front axle and rear axle respectively; Parameter subscript Represent the left and right wheels respectively; Parameter subscript Pick 、 、 、 When represents the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively; The initial toe angle of each tire Obtained through vehicle four-wheel alignment.

3. The indirect measurement method of tire slip angle when a vehicle is running on wet land according to claim 2, characterized in that: The S2 collects the motion state parameters of the vehicle and tires during driving, including: Longitudinal speed of the vehicle , lateral speed , yaw angular velocity , roll angular velocity , pitch angular velocity and the steering angle of the tires ,in: The longitudinal speed , the lateral speed 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 Collected by tire angle sensor.

4. The indirect measurement method of tire slip angle when a vehicle is running on wet land according to claim 3, characterized in that: S3 calculates the longitudinal velocity of the tire center position in the vehicle body coordinate system and lateral speed ,include: The longitudinal speed , satisfying the formula: Where: 、 、 are the longitudinal speeds of the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively; The lateral speed , satisfying the formula: Where: 、 、 are the lateral velocities of the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively.

5. The indirect measurement method of tire slip angle when a vehicle is running on wet land according to claim 4, characterized in that: The S4 calculates the side slip angle of the tire in the vehicle body coordinate system , satisfying the formula: Where: 、 are the longitudinal velocity and lateral velocity of the tire center position in the vehicle body coordinate system, respectively.

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