A method for estimating a road adhesion coefficient based on a tire slip start position parameter

Abstract

The application provides a method for estimating road adhesion coefficient based on tire slip starting position parameter, which is based on the vehicle motion signals output by the automobile speed sensor, the wheel speed sensor and the tire inner lining acceleration sensor, the rolling tire real-time slip rate and the corresponding slip starting position coordinates are obtained through the slip starting position calculation module of the rolling tire, and then the tire road adhesion coefficient estimation model is established to obtain the road adhesion coefficient corresponding to the rolling tire real-time slip rate. The input parameters required by the intelligent tire system collection algorithm of multiple sensors are set; according to the vehicle motion signals provided by the automobile sensor and the design of the specific estimation method, the rapid and accurate estimation of the rolling tire real-time slip rate, the slip starting position coordinates and the road adhesion coefficient can be realized, which lays a good method guidance and theoretical basis for the wide application of intelligent automobiles and vehicle dynamics control.

Description

Technical Field

[0001] This invention relates to a method for estimating the road surface adhesion coefficient, specifically a method for estimating the road surface adhesion coefficient based on the tire slip start point position parameter, belonging to the field of vehicle engineering technology. Background Technology

[0002] Slip ratio refers to the ratio between the wheel's rotational speed and the vehicle's speed, commonly used to describe the relative slippage between the wheel and the ground, ranging from 0 to 1. The slip initiation point is the critical point between the adhesion zone and the slip zone in the tire-ground contact area. It is key to distinguishing between the contact patch adhesion zone and the slip zone, and the slip initiation point changes with different slip ratios. Calculating the slip initiation point allows for the determination of the vehicle's adhesion and slippage state, which is crucial for driving safety. The road surface adhesion coefficient refers to the frictional characteristics between the road surface and the vehicle's wheels, also known as the coefficient of friction. It is the ratio of tire adhesion force to the wheel's normal (perpendicular to the road surface) pressure. The higher the road surface adhesion coefficient, the greater the available adhesion force, and the less likely the vehicle is to slip. The road surface adhesion coefficient is affected by various factors, including road material, road conditions (such as dryness, wetness, oiliness, etc.), temperature, tire type, and condition. The coefficient of adhesion can vary greatly under different road conditions, which affects the vehicle's handling, braking, and acceleration performance. Therefore, when the vehicle's operating conditions change, the change in the slip start position under different slip ratios leads to a change in the ratio between the wheel contact imprint adhesion zone and the slip zone, which is reflected in the coefficient of adhesion between the wheel and the ground at this time. Therefore, accurately and in real time estimating the road surface adhesion coefficient when the vehicle is driving is of great significance to the vehicle's driving safety.

[0003] During vehicle operation, the coefficient of friction between the tires and the road surface is a key factor affecting acceleration, braking, and handling stability. Based on different testing methods and measurement parameters, road surface friction coefficient estimation algorithms are divided into cause-based and effect-based types. However, with the continuous development of vehicle intelligence, methods that use sensors installed inside the tires to monitor tire status information in real time have received increasing attention. Currently, common methods for estimating the road surface friction coefficient include using neural network models and support vector machine algorithms. These methods offer high prediction accuracy but have significant limitations; they are only applicable to the tested tires, and the estimation results can vary greatly for different tires. Summary of the Invention

[0004] Objective of the invention: To address the shortcomings of existing technologies, this invention provides a method for estimating the road surface adhesion coefficient based on tire slip start point position parameters. The method involves collecting vehicle signals from a vehicle speed sensor, wheel speed sensors, and tire inner liner acceleration sensors. A slip start point position calculation module is used to obtain the real-time slip ratio and slip start point position coordinates. Furthermore, an adhesion coefficient calculation model is established based on the ground pressure distribution theory and the tire pure longitudinal slip brush model to obtain the road surface adhesion coefficient corresponding to the real-time slip ratio.

[0005] Technical solution: A method for estimating road adhesion coefficient based on tire slip start point position parameters, comprising the following steps: S1, setting up a multi-sensor intelligent tire system, specifically, installing a vehicle speed sensor and a wheel speed sensor on the vehicle body, and installing an acceleration sensor at the longitudinal centerline position of the tire inner liner, wherein the vehicle speed sensor, the wheel speed sensor and the tire inner liner acceleration sensor are all signal connected to the slip start point position calculation module;

[0006] S2. By collecting signals output by the vehicle speed sensor and the wheel speed sensor, the real-time slip ratio of the rolling tire can be quickly calculated.

[0007] S3. Import the real-time slip ratio obtained in S2 into the slip start position calculation module to obtain the slip start position of the rolling tire;

[0008] S4. By collecting the signal output from the rolling tire inner liner acceleration sensor, the radial acceleration is obtained to calculate the tire contact length.

[0009] S5. Establish a road surface adhesion coefficient estimation model using tire contact length and contact pressure distribution function;

[0010] S6. Substitute the parameters such as the real-time slip ratio of the rolling tire, the slip start position, and the tire contact length obtained in S2-S4 into the road adhesion coefficient estimation model to perform real-time estimation of the road adhesion coefficient under different slip ratios of the rolling tire.

[0011] This invention sets the input parameters required for the intelligent tire system acquisition algorithm using multiple sensors, resulting in a more accurate and faster coefficient of friction estimation method. Based on the signals provided by the vehicle sensors and the design of a targeted estimation method, it can achieve real-time estimation of tire slip ratio, slip start point coordinates, and road surface coefficient of friction, providing effective and reliable data support for better understanding of vehicle information and timely control.

[0012] In a preferred embodiment, S1 specifically includes:

[0013] The wheel speed sensor is mounted on the wheel hub of the vehicle, the vehicle speed sensor is mounted on the vehicle frame, and the acceleration sensor is mounted on the longitudinal centerline of the tire liner. The wheel speed sensor, the vehicle speed sensor, and the tire liner acceleration sensor are all connected to the slip start position calculation module via a CAN line.

[0014] In a preferred embodiment, S2 specifically comprises:

[0015] The rolling tire slip start position calculation module receives signals from the vehicle speed sensor and wheel speed sensor, processes the information to obtain the vehicle speed V and wheel speed W parameters, and substitutes these parameters into the slip ratio calculation formula to calculate the real-time slip ratio. The formula for calculating the real-time slip ratio of the rolling tire is as follows:

[0016]

[0017] In the formula, R is the free rolling radius of the wheel, V is the vehicle speed, and W is the wheel rotation speed.

[0018] In a preferred embodiment, S3 specifically includes:

[0019] The slip initiation position u is established using a tire pure longitudinal slip brush model and arbitrary ground pressure distribution theory. c Theoretical calculation formula:

[0020] u c =AF z u s (Bz i 5 -z i 4 -Bz i -1)-2k tx S x z i (2)

[0021] In the formula, z i A and B are undetermined coefficients, i = 1, 2, ... 5, F z For the vertical load of the tire, k tx For the tread element stiffness, u s It is the static friction coefficient.

[0022] Using the controlled variable method, by changing the parameter F in equation (2) z k tx S x Calculate the starting position u of the slippage under different parameters. c The formula for calculating the slip start position is obtained by fitting the data using the least squares polynomial fitting method, as shown in equation (3), and the values ​​of the characteristic parameters p1, p2, p3, and p4.

[0023]

[0024] In the formula, p1, p2, p3, and p4 are characteristic parameters, and S x Real-time slip ratio of rolling tires.

[0025] In a preferred embodiment, S4 specifically comprises:

[0026] A rolling tire model is established using the finite element method to obtain the rolling tire acceleration signal. This is achieved by receiving the radial acceleration signal 'a' from the tire's inner liner acceleration sensor. y At that time, the time interval t1 between the two peaks of the acceleration curve is initially calculated;

[0027] For radial acceleration curve a y The first derivative curve of radial acceleration is processed by differentiation, and the time interval t2 between the two peaks of the radial acceleration curve after differentiation is calculated.

[0028] Calculate the grounding angle θ:

[0029]

[0030] Calculate the grounding trace length L:

[0031]

[0032] In the formula, a is the half length of the grounding imprint, 0.5*L.

[0033] In a preferred embodiment, S5 specifically includes:

[0034] According to the pure longitudinal slip brush model of the tire, the starting position of the rolling tire slip is the key to dividing the tire contact patch area into two parts: the slip zone and the adhesion zone. The expression for the longitudinal force of the tire in the adhesion zone of the contact patch is given by equation (6):

[0035]

[0036] In equation (6), k tx denoted as tread element stiffness; 'a' is half-length of the ground imprint; 'u' is the normalized ground imprint coordinates; u c The coordinates of the starting point of the slide;

[0037] The expression for the longitudinal force of the tire within the slip zone of the ground imprint is given by equation (7):

[0038]

[0039] In equation (7), q z (u) is a function representing any ground pressure distribution within the tire contact patch area, specifically expressed as:

[0040]

[0041] In equation (8), n = 1, 2, 3; let the vertical load offset of the tire be Δ, and according to the mechanical characteristics of the tire, the ground pressure distribution q z (u i ) and the vertical load F of the tire z The relationship needs to satisfy and Let η(u)=A·(1-u 2n )·(1-Bu), should satisfy the boundary condition of equation (9):

[0042]

[0043] According to the grounding pressure distribution q z (u i The boundary conditions that need to be satisfied can be expressed as follows:

[0044]

[0045] The longitudinal force in the tire contact area is the sum of the longitudinal force in the slip zone and the longitudinal force in the adhesion zone, as shown in equation (11):

[0046]

[0047] Finally, based on the friction theorem, the relationship between the road surface adhesion coefficient and the slip ratio is obtained, as shown in equation (12).

[0048]

[0049] In equation (12), To estimate the obtained road surface adhesion coefficient.

[0050] Beneficial effects: This invention sets the input parameters required for the intelligent tire system acquisition algorithm using multiple sensors, resulting in a more accurate and faster coefficient of friction estimation method. Based on the signals provided by the sensors and the design of targeted estimation methods, it can achieve real-time estimation of tire slip ratio, slip start point coordinates, and road surface coefficient of friction, providing effective and reliable data support for better understanding of vehicle information and timely control.

[0051] The present invention establishes a method for estimating the road surface adhesion coefficient based on the tire slip start position parameter. While calculating the road surface adhesion coefficient under different slip ratios, it also completes the calculation of real-time slip ratio, slip start position coordinates, and tire longitudinal force, which has a wider range of applications for vehicle dynamics control.

[0052] In summary, this invention can accurately estimate the road surface adhesion coefficient in real time under different slip ratios, and can be widely applied to the real-time estimation of road surface adhesion coefficient by smart tires. Attached Figure Description

[0053] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0054] Figure 1 This is a flowchart of the adhesion coefficient estimation method of the present invention.

[0055] Figure 2 This is a simplified physical model diagram of the tire of this invention.

[0056] Figure 3 The coordinates of the slip start point position for different slip ratios are estimated by this invention.

[0057] Figure 4 This is a diagram showing the longitudinal force distribution of tire contact patch under different slip ratios as estimated by the present invention.

[0058] Figure 5 The results show the estimated road surface adhesion coefficient under different slip ratios according to the present invention. Detailed Implementation

[0059] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0060] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0061] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0062] like Figure 1 As shown, a method for estimating the road surface adhesion coefficient based on tire slip start point position parameters includes the following steps:

[0063] S1. An intelligent tire system with multiple sensors, specifically, a vehicle speed sensor and a wheel speed sensor are installed on the vehicle body, and an acceleration sensor is installed at the longitudinal centerline of the tire liner. The vehicle speed sensor, the wheel speed sensor, and the tire liner acceleration sensor are all connected to the slip start position calculation module.

[0064] Specifically, S1 is:

[0065] The wheel speed sensor is mounted on the wheel hub of the vehicle, and the vehicle speed sensor is mounted on the vehicle frame. The acceleration sensor, wheel speed sensor, and vehicle speed sensor are connected to the slip start position calculation module via a CAN line.

[0066] This invention sets the input parameters required for the intelligent tire system acquisition algorithm using multiple sensors, resulting in a more accurate and faster coefficient of friction estimation method. Based on the signals provided by the sensors and the design of targeted estimation methods, it can accurately estimate the real-time tire slip ratio, the coordinates of the slip start point, and the road surface coefficient of friction, providing effective and reliable data support for better understanding of vehicle information and timely control.

[0067] like Figures 2 to 5 As shown, S2 collects the signals output by the wheel speed sensor and the vehicle speed sensor, and calculates the real-time slip rate of the rolling tire.

[0068] Specifically, S2 is:

[0069] The rolling tire slip start position calculation module receives signals from the vehicle speed sensor and wheel speed sensor, processes the information to obtain the vehicle speed V and wheel speed W parameters, and substitutes the vehicle speed V, wheel speed W parameters, and tire free rolling radius into the slip ratio calculation formula to calculate the real-time slip ratio S. xThe calculation formula is

[0070]

[0071] In the formula, R is the free rolling radius of the wheel, V is the vehicle speed, and W is the wheel rotation speed.

[0072] S3. Import the slip ratio obtained in S2 into the slip start position calculation module to obtain the slip start position;

[0073] Specifically, S3 is:

[0074] The slip initiation position u is established using a pure longitudinal slip tire brush model and the theory of arbitrary ground pressure distribution. c Theoretical calculation formula

[0075] u c =AF z u s (Bz i 5 -z i 4 -Bz i -1)-2k tx S x z i (2)

[0076] In the formula, z i A and B are undetermined coefficients, i = 1, 2, ... 5, F z For the vertical load of the tire, k tx For the tread element stiffness, u s Let F be the static friction coefficient. Using the controlled variable method, the parameter F in equation (2) is changed. z k tx S x Calculate the starting position u of the slippage under different parameters. c For data fitting, as shown in the table below, the slip start position under different slip ratios when the tire tread stiffness is 5680000 and the load on the tire is 2800N, 3800N, and 4800N. Similarly, by changing the tire tread longitudinal stiffness to 3680000 and 4680000 and repeating the calculation, the influence data of the tire tread longitudinal stiffness on the slip start position can be obtained. The calculation formula of the slip start position is obtained by fitting the least squares polynomial method as shown in the following formula (3), as well as the values ​​of the characteristic parameters p1, p2, p3, and p4.

[0077]

[0078] In the formula, p1, p2, p3, and p4 are characteristic parameters, and S x Longitudinal slip ratio.

[0079]

[0080]

[0081] S4. Acquire the acceleration signal output by the tire inner liner acceleration sensor, obtain the radial acceleration, and calculate the tire contact length.

[0082] Specifically, S4 is:

[0083] A rolling tire model is established using the finite element method to obtain the rolling tire acceleration signal. This is achieved by receiving the radial acceleration signal 'a' from the tire's inner liner acceleration sensor. y At that time, the time interval t1 between the two peaks of the acceleration curve is initially calculated;

[0084] For radial acceleration curve a y The first derivative curve of radial acceleration is obtained by performing differentiation, and the time interval t2 between the two peaks of the radial acceleration curve after differentiation is calculated.

[0085] Calculate the grounding angle θ:

[0086]

[0087] Calculate the grounding trace length L:

[0088]

[0089] In the formula, 'a' represents the half-length of the tire contact patch, which is 0.5 * L.

[0090] S5. Establish a road surface adhesion coefficient estimation model using tire contact length and contact pressure distribution function;

[0091] Specifically, S5 is:

[0092] According to the pure longitudinal slip brush model of the tire, the starting position of the rolling tire slip is the key to dividing the tire contact patch area into two parts: the slip zone and the adhesion zone. The expression for the longitudinal force of the tire in the adhesion zone of the contact patch is given by equation (6):

[0093]

[0094] In equation (6), k tx denoted as tread element stiffness; 'a' is half-length of the ground imprint; 'u' is the normalized ground imprint coordinates; u c The coordinates of the starting point of the slide;

[0095] The expression for the longitudinal force of the tire within the slip zone of the ground imprint is given by equation (7):

[0096]

[0097] In equation (7), q z (u) is a function representing any ground pressure distribution within the tire contact patch area, specifically expressed as:

[0098]

[0099] In equation (8), n = 1, 2, 3; let the vertical load offset of the tire be Δ, and according to the mechanical characteristics of the tire, the ground pressure distribution q z (u i ) and the vertical load F of the tire z The relationship needs to satisfy and Let η(u)=A·(1-u 2n )·(1-Bu) should satisfy the following boundary conditions:

[0100]

[0101] According to the grounding pressure distribution q z (u i The boundary conditions that need to be satisfied can be expressed as follows:

[0102]

[0103] The longitudinal force in the tire contact area is the sum of the longitudinal force in the slip zone and the longitudinal force in the adhesion zone, as shown in equation (11):

[0104]

[0105] Finally, based on the friction theorem, the relationship between the road surface adhesion coefficient and the slip ratio is obtained, as shown in equation (12).

[0106]

[0107] In equation (12), To estimate the obtained road surface adhesion coefficient.

[0108] S6. Substitute the real-time slip ratio, slip start position and tire contact length parameters obtained from S2-S4 into the road adhesion coefficient estimation model to perform real-time estimation of the road adhesion coefficient under different slip ratios.

[0109] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0110] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for estimating road surface adhesion coefficient based on tire slip start point position parameters, characterized in that, Includes the following steps: S1. An intelligent tire system with multiple sensors, specifically, a vehicle speed sensor and a wheel speed sensor are installed on the vehicle body, and an acceleration sensor is installed at the longitudinal centerline of the tire liner. The vehicle speed sensor, the wheel speed sensor, and the tire liner acceleration sensor are all connected to the slip start position calculation module. S2. Estimate the real-time slip rate of the rolling tires by collecting the signals output by the vehicle speed sensor and the wheel speed sensor. S3. Import the real-time slip ratio of the rolling tire obtained in S2 into the slip start position calculation module to obtain the slip start position of the rolling tire. S4. By collecting the signal output by the acceleration sensor, the radial acceleration is obtained to estimate the tire contact length; S5. Based on the pure longitudinal skidding brush model of the tire, combined with the tire ground contact length and ground pressure distribution function, and coupled with the correlation between the real-time slip ratio of the rolling tire and the slip start position, a road surface adhesion coefficient estimation model is established. S6. Substitute the real-time slip ratio, slip start position and tire ground contact length parameters obtained from S2-S4 into the road surface adhesion coefficient estimation model in S5 to perform real-time estimation of the road surface adhesion coefficient under different slip ratios of the rolling tire.

2. The method for estimating the road adhesion coefficient based on tire slip start point position parameters according to claim 1, characterized in that, Specifically, S1 is: The wheel speed sensor is mounted on the wheel hub of the vehicle, and the vehicle speed sensor is mounted on the vehicle frame; the wheel speed sensor, the vehicle speed sensor, and the tire liner acceleration sensor are all connected to the S3 slip start position calculation module via a CAN line.

3. The method for estimating the road adhesion coefficient based on tire slip start point position parameters according to claim 1, characterized in that, Specifically, S2 is: The rolling tire slip start position calculation module obtains the vehicle speed by receiving signals from the vehicle speed sensor and wheel speed sensors. Wheel speed The parameters will yield the car speed. Wheel speed The real-time slip ratio of the rolling tire is calculated by substituting the parameters into the calculation formula. The calculation formula is: （1） In the formula, Let the radius be the radius of free rolling of the wheel. For car speed, This refers to the wheel rotation speed.

4. The method for estimating the road adhesion coefficient based on tire slip start point position parameters according to claim 1, characterized in that, Specifically, S3 is: The slip initiation position u is established using a tire pure longitudinal slip brush model and arbitrary ground pressure distribution theory. c The theoretical calculation formula is: （2） In the formula, A and B are undetermined coefficients, i = 1, 2, ...

5. For the vertical load of the tire, For the tread element stiffness, The coefficient of static friction; Using the controlled variable method, by changing the parameters in equation (2) , , Calculate the starting position u of the slippage under different parameters. c The formula for calculating the slip start position is obtained by using the least squares polynomial fitting method, as shown in equation (3), and the characteristic parameters are used for data fitting. , , , The value; （3） In the formula, , , , For characteristic parameters, Real-time slip ratio of rolling tires.

5. The method for estimating the road adhesion coefficient based on tire slip start point position parameters according to claim 1, characterized in that, Specifically, S4 is: By receiving the radial acceleration signal a from the tire liner acceleration sensor y At that time, the time interval t1 between the two peaks of the acceleration curve is initially calculated; For radial acceleration curve a y The first-order radial acceleration curve is obtained by performing differentiation, and the time interval t2 between the two peaks of the radial acceleration curve after differentiation is calculated. Calculate the grounding angle : （4） Calculate the grounding trace length L: （5） In the formula, a is the half length of the grounding imprint, 0.5*L.

6. The method for estimating the road adhesion coefficient based on tire slip start point position parameters according to claim 1, characterized in that, Specifically, S5 is: According to the tire pure longitudinal slip brush model, the expression for the tire longitudinal force in the adhesion zone of the contact patch is Equation (6): (6) In equation (6), For tread unit stiffness; The grounding imprint is half the length; These are the normalized coordinates of the grounding imprint. The coordinates of the starting point of the rolling tire's slippage; The expression for the longitudinal force of the tire within the slip zone of the tire contact patch is given by equation (7): (7) In equation (7), Let be the function representing any ground pressure distribution within the tire ground imprint area, specifically expressed as equation (8): (8) In equation (8), n = 1, 2, 3; let the vertical load offset of the tire be... Based on the mechanical properties of the tire, the ground pressure distribution Vertical load F of tire z The relationship needs to satisfy and ,make The boundary conditions of equation (9) should be satisfied: （9） According to the grounding pressure distribution The boundary conditions that need to be satisfied can be expressed as equation (10) for A and B: （10） The longitudinal force in the tire contact area is the sum of the longitudinal force in the slip zone and the longitudinal force in the adhesion zone, as shown in equation (11): （11） Finally, the relationship between the road surface adhesion coefficient and the slip ratio is obtained according to the friction theorem, as shown in equation (12). （12） In equation (12), φ is the estimated road surface adhesion coefficient.

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