Method for compensating for lateral deviation of autonomous driving caused by tire pressure problem

Abstract

This invention provides a method for compensating for lateral deviation in autonomous driving caused by tire pressure issues, comprising the following steps: Step S1, real-time acquisition of tire motion information during vehicle operation; the tire motion information includes the linear velocity and angular velocity of tire rolling; Step S2, calculation of the tire rolling radius based on the tire motion information, and determination of whether the tire pressure is abnormal using a radius iteration method, wherein the radius iteration method uses a pre-set characteristic parameter γ to represent the difference in tire rolling radius to determine whether the tire pressure is abnormal; Step S3, determination of the relationship between tire pressure and tire radius based on the tire rolling radius and characteristic parameter γ, and determination of the tire location with abnormal tire pressure; Step S4, calculation of the compensation value for the steering wheel angle based on the characteristic parameter γ.

Description

Technical Field

[0001] This invention relates to the field of autonomous vehicles, and more specifically to a method for compensating for lateral deviations in autonomous driving caused by tire pressure issues. Background Technology

[0002] With the development and continuous advancement of autonomous driving, during the development of autonomous driving control algorithms and real-vehicle testing, a situation has arisen where understeering in corners is caused by insufficient tire pressure. This situation is extremely dangerous for autonomous vehicles. Due to long-term testing and use, phenomena such as reduced tire pressure and tire wear are very common. Therefore, a method to solve the above problems is urgently needed.

[0003] Currently, there are two solutions to the above problems in this field. The first is to remotely monitor the tire pressure of L4 level autonomous vehicles to prevent flat tires or other tire problems from threatening the safety of autonomous vehicles. The second is to let the vehicle run for a period of time, calculate the lateral stiffness after the tire pressure change using relevant parameters, and then, based on the autonomous vehicle modeled with two degrees of freedom, use the parametric lateral stiffness to correct a certain amount of deviation.

[0004] However, the two methods described above still have several drawbacks. The first method only provides preventative measures against tire pressure issues and still requires manual tire inflation to ensure vehicle operation. In the second method, since autonomous vehicle algorithms often use a two-degree-of-freedom model to build the vehicle's kinematics (like a bicycle model), when one tire on the same axle has low pressure, the radii of the tires on the same axle are no longer equal, causing the two-degree-of-freedom model to break at a certain critical point. Therefore, simply using the lateral stiffness parameter to compensate for the steering wheel angle output in the algorithm may be insufficient. Furthermore, autonomous vehicles may deviate due to differences in tire radii. And this method has not been applied to Level 4 autonomous driving.

[0005] In conclusion, during testing and development, simply reminding drivers to inflate low tire pressure or replace severely worn tires may be suitable for low-level autonomous driving (L2 and below), without considering various complex scenarios and dangerous situations. However, this method cannot guarantee that the autonomous vehicle will accurately follow the planned trajectory, posing safety hazards during operation. For high-level autonomous driving, especially L4, extreme situations in special scenarios must also be considered. Summary of the Invention

[0006] The purpose of this invention is to provide a method for compensating for lateral deviations in autonomous driving caused by tire pressure issues, thereby avoiding the paranoia that occurs when the two-degree-of-freedom model is broken due to excessively low tire pressure. This method obtains characteristic parameters based on the tire motion information under different tire pressures and the rolling radius of each tire. These characteristic parameters change with tire pressure variations. The method then uses these characteristic parameters and the tire rolling motion information to determine the changes in the rolling radius of each tire to locate the low-pressure tire. Simultaneously, based on changes in tire pressure, tire angular velocity, vehicle speed, tire radius, etc., the method continuously tests the steering error under different parameters to compensate for understeering.

[0007] To achieve the above objectives, the present invention provides a method for compensating for lateral deviation in autonomous driving caused by tire pressure issues, comprising the following steps:

[0008] Step S1: Real-time acquisition of tire motion information during vehicle operation; the tire motion information includes the linear velocity and angular velocity of tire rolling.

[0009] Step S2: Calculate the rolling radius of the tire based on the tire's motion information, and determine whether the tire pressure is abnormal using the radius iteration method. The radius iteration method uses a pre-set characteristic parameter γ to represent the difference in the tire's rolling radius in order to determine whether the tire pressure is abnormal.

[0010] Step S3: Based on the tire's rolling radius and characteristic parameter γ, determine the relationship between tire pressure and tire radius, and identify the location of tires with abnormal tire pressure; and

[0011] Step S4: Calculate the compensation value of the steering wheel angle based on the characteristic parameter γ.

[0012] In one embodiment, in step S2, when the characteristic parameter γ remains non-zero, the tire pressure is abnormal; the calculation formula for the pre-set characteristic parameter γ is as follows:

[0013]

[0014] Among them, R FL R represents the rolling radius of the left front wheel. FR R represents the rolling radius of the right front wheel. RL R represents the rolling radius of the left rear wheel. RR This represents the rolling radius of the right rear wheel.

[0015] In one embodiment, the formula for calculating the rolling radius of the tires during vehicle operation is as follows:

[0016]

[0017] Where R represents the rolling radius of the tire, and VR ω represents the linear velocity of the tire as it rolls. R This represents the angular velocity of the tire rolling.

[0018] In one embodiment, in step S2, when the rolling radius R is a constant, the calculation formula for the characteristic parameter γ is as follows:

[0019]

[0020] Among them, V FL V represents the linear velocity of the left front wheel. FR V represents the linear velocity of the right front wheel. RL V represents the linear velocity of the left rear wheel. RR ω represents the linear velocity of the right rear wheel. FL ω represents the angular velocity of the left front wheel. FR ω represents the angular velocity of the right front wheel. RL ω represents the angular velocity of the left rear wheel. RR This represents the angular velocity of the right rear wheel.

[0021] In one embodiment, step S2 further includes iteratively solving for the characteristic parameter γ in equation (3) using the recursive least squares method, as follows:

[0022] y = Ax (4)

[0023] Where A = 1;

[0024]

[0025]

[0026]

[0027] p(k)=(1-q(k))p(k-1) (8)

[0028] Where p and A satisfy the following relationship:

[0029] p = (A T A) -1 (9)

[0030] The termination condition for the iteration is:

[0031]

[0032] Where, δ γ As the termination limit, The value at which the iteration converges is γ.

[0033] In one embodiment, step S3 specifically involves:

[0034] The rolling radius of each tire is calculated using equation (2). Based on the tire radius and characteristic parameter γ, calibration is performed to determine the relationship between tire pressure and tire radius.

[0035] Compare the rolling radius of each tire and determine the location of the tire with abnormal tire pressure.

[0036] In one embodiment, in step S4, when the tire pressure on one side of the coaxial tire is insufficient, a compensation value for the steering wheel angle is calculated based on the characteristic parameter γ.

[0037] In one embodiment, step S4 specifically involves:

[0038] When the tire pressure difference between the two tires on the same axle exceeds 0.1 kPa, the compensation value for the steering wheel angle is calculated based on the characteristic parameter γ; otherwise, no compensation is made.

[0039] In one embodiment, the formula for calculating the compensation value of the steering wheel angle in step S4 is:

[0040] Steering Angle tire pressure =γ*K p *τ*lat_error (11)

[0041] Among them, Steering Angle tire pressure γ is the compensation value for the steering wheel angle; γ is the characteristic parameter calculated in step S2, which is a dynamic value under different tire motion information; τ is the pressure difference coefficient, which is dynamically calibrated according to the tire pressure under different conditions; K p The calibration coefficient is adjusted to achieve the expected value; lat_error is the lateral error.

[0042] In one embodiment, when tires on the same side simultaneously experience abnormal tire pressure, the pressure difference coefficient τ in the dynamic calibration formula (11) and the calculation formula for the characteristic parameter γ are as follows:

[0043]

[0044] Where, ω FL ω represents the angular velocity of the left front wheel. FR This represents the angular velocity of the right front wheel; the lateral error lat_error continuously converges to 0 based on the compensation value of the steering wheel angle to calibrate the error.

[0045] The beneficial effects of the method for compensating for lateral deviation in autonomous driving caused by tire pressure problems according to the present invention are as follows:

[0046] 1. When there is a minor problem with the tire pressure, but it is not enough for the driver to change the tire or inflate it, this invention ensures that the autonomous vehicle can drive more accurately along the planned trajectory.

[0047] 2. During driving, when the air pressure of a single tire suddenly becomes problematic, the method provided by this invention still compensates for the steering wheel angle to ensure that the autonomous vehicle will not be in danger due to sudden changes in physical hardware while driving at high speed. This effectively ensures the safety, continuity, and adaptability of the autonomous vehicle and can protect the safety of passengers in real time. Attached Figure Description

[0048] Figure 1 This is a flowchart illustrating a method for compensating for lateral deviation in autonomous driving caused by tire pressure issues, according to an embodiment of the present invention.

[0049] Figure 2 A flowchart illustrating a method for compensating for lateral deviation in autonomous driving caused by tire pressure issues, according to an embodiment of the present invention; and

[0050] Figure 3 This is a schematic diagram of tire pressure when the tire pressure of the same side tire is abnormal in one embodiment of the present invention; wherein, FL represents the left front tire, FR represents the right front tire, RL represents the left rear tire, and RR represents the right rear tire. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0052] Figure 1 The present invention discloses a method for compensating for lateral deviation in autonomous driving caused by tire pressure problems, specifically including the following steps:

[0053] Step S1: Collect tire motion information in real time during vehicle operation; tire motion information includes the linear velocity and angular velocity of tire rolling.

[0054] Step S2: Calculate the tire's rolling radius based on the tire's motion information, and determine whether the tire pressure is abnormal using the radius iteration method. The radius iteration method uses a pre-set characteristic parameter γ to represent the difference in the tire's rolling radius in order to determine whether the tire pressure is abnormal.

[0055] Step S3: Determine the relationship between tire pressure and tire radius based on the tire's rolling radius and characteristic parameter γ, and identify the location of tires with abnormal tire pressure; and

[0056] Step S4: Calculate the compensation value of the steering wheel angle based on the characteristic parameter γ.

[0057] Further, in step S4, when the tire pressure on one side of the coaxial tires is insufficient, a compensation value for the steering wheel angle is calculated based on the characteristic parameter γ. Preferably, in this embodiment, step S4 specifically involves: determining whether the pressure difference between the coaxial tires exceeds 0.1 kPa; if so, calculating a compensation value for the steering wheel angle based on the characteristic parameter γ; otherwise, no compensation is performed. See [link to relevant documentation]. Figure 2 .

[0058] Furthermore, in step S2, when the characteristic parameter γ remains non-zero, the tire pressure is abnormal. The pre-defined formula for calculating the characteristic parameter γ is as follows:

[0059]

[0060] Among them, R FL R represents the rolling radius of the left front wheel. FR R represents the rolling radius of the right front wheel. RL R represents the rolling radius of the left rear wheel. RR Represents the rolling radius of the right rear wheel;

[0061] During actual vehicle operation, the effective rolling radius of a tire cannot be directly measured and is usually calculated using the following method:

[0062]

[0063] Where R represents the rolling radius of the tire, and V R ω represents the linear velocity of the tire as it rolls. R This represents the angular velocity of the tire rolling.

[0064] Furthermore, assuming the rolling radius R is constant, the characteristic parameter γ can be calculated using the tire's motion information, as shown in the following formula:

[0065]

[0066] Among them, V FL V represents the linear velocity of the left front wheel. FR V represents the linear velocity of the right front wheel. RL V represents the linear velocity of the left rear wheel. RR ω represents the linear velocity of the right rear wheel. FL ω represents the angular velocity of the left front wheel. FR ω represents the angular velocity of the right front wheel. RL ω represents the angular velocity of the left rear wheel. RR This represents the angular velocity of the right rear wheel.

[0067] The tire motion information needs to be filtered, but even after processing, the feature parameter γ will still oscillate violently due to road conditions, making it impossible to obtain its exact range. Therefore, the recursive least squares (RLS) method is used to iteratively solve for the feature parameter γ. The specific steps are as follows:

[0068] y = Ax (4)

[0069] Where A = 1;

[0070]

[0071]

[0072]

[0073] p(k)=(1-q(k))p(k-1) (8)

[0074] Where p and A satisfy the following relationship:

[0075] p = (A T A) -1 (9)

[0076] The termination condition for the iteration is:

[0077]

[0078] Where, δ γ As the termination limit, The value at which the iteration converges is γ. During normal vehicle operation, if the characteristic parameter γ remains non-zero, it is considered that there is a problem with the tire pressure. However, this characteristic parameter cannot pinpoint which tire is flat. Therefore, it is necessary to determine the relationship between tire pressure and tire radius based on the tire's rolling radius and the characteristic parameter γ to determine the location of the tire with abnormal tire pressure, i.e., step S3 mentioned above.

[0079] In this embodiment, step S3 specifically includes:

[0080] The only parameter representing tire pressure using the radius iteration method is γ, and the coefficient γ in the formula is such that the linear velocity of the four tires of the vehicle is within a certain range. Even then, the coefficients will still converge.

[0081] For example, this coefficient convergence will occur when both the left front tire and the left rear tire have low pressure. Therefore, the radius of each tire needs to be calculated using the following formula:

[0082]

[0083] At the same time, calibration is performed based on the tire radius and tire pressure coefficient to determine the approximate relationship between tire pressure and tire radius;

[0084] By comparing the radii of the four wheels, we can ultimately determine which tire pressure is the problem when there is an issue.

[0085] The specific information for all four tires when the left front tire pressure is unstable is shown in Table 1 below. Generally, lower tire pressure results in higher linear velocity. Therefore, we can use this method to pinpoint which tire has low pressure.

[0086] Table 1. Specific information for all four tires when the left front tire (FL) pressure is unstable.

[0087] tire linear velocity angular velocity radius Tire pressure FR 5.54m / s 17.64 rad / s 31.40cm 2.5 kPa FL 5.89m / s 19.95 rad / s 29.52cm 2.0 kPa RR 5.55m / s 17.66 rad / s 31.42cm 2.5 kPa RL 5.56m / s 17.65 rad / s 31.50cm 2.5 kPa

[0088] In this embodiment, step S4 specifically includes:

[0089] For autonomous driving control algorithms built using a two-degree-of-freedom model, the impact of both tires on the same axle being too low is not significant. However, when the tire pressure on one side of the front wheel or one side of the rear wheel is insufficient, the two degrees of freedom are broken. That is, when the tire pressure difference on the same axle exceeds 0.1 kPa, the steering wheel compensation value needs to be calculated. The calculation method is as follows:

[0090] Based on γ calculated using the radius iteration method, the compensation value for the steering wheel angle, SteeringAngle, is calculated. tire pressure :

[0091] The formula for calculating the compensation value of the steering wheel angle in step S4 is:

[0092] Steering Angle tire pressure =γ*K p *τ*lat_error (11)

[0093] Among them, Steering Angle tire pressure γ is the compensation value for the steering wheel angle; τ is the characteristic parameter calculated in step S2; τ is the pressure difference coefficient, which is dynamically calibrated according to the tire pressure under different conditions, and is usually 1; K p These are the calibration coefficients that need to be adjusted to achieve the expected values; lat_error is the lateral error.

[0094] Depending on the tire speed, γ will be a dynamic value. The final result will be the steering angle calculated based on data and calculations from the actual vehicle driving dynamics. tire pressure This method compensates for lateral deviations caused by unstable tire pressure.

[0095] But when such a situation occurs Figure 3 In the case shown, the γ parameter is due to the formula. It will be very close to 0, but at this point, the problem of insufficient tire pressure still occurs.

[0096] When assessing tire pressure relationships, if both FR and RR tires exhibit excessively low rotation radii, or if both FL and RL tires exhibit excessively low rotation radii simultaneously, then this situation is considered to have occurred. The formula for this situation is as follows:

[0097]

[0098] Where, ω FL ω represents the angular velocity of the left front wheel. FR This represents the angular velocity of the right front wheel. The parameter τ will also change from 1 to 2, dynamically calibrated according to tire pressure conditions under different circumstances. The lateral error lat_error will also converge towards 0 based on the compensated parameter value, thus achieving error calibration. As shown in Table 2 below, when both tires on the same side have low pressure, parameter τ is required for calibration.

[0099] Table 2. Specific information for all four tires when the tire pressure on the same side is low.

[0100] tire linear velocity angular velocity radius Tire pressure FR 5.57m / s 17.69 rad / s 31.48cm 2.5 kPa FL 6.01m / s 19.50 rad / s 30.82cm 2.0 kPa RR 5.49m / s 17.42 rad / s 31.51cm 2.5 kPa RL 5.97m / s 19.52 rad / s 30.58cm 2.0 kPa

[0101] The beneficial effects of the method for compensating for lateral deviation in autonomous driving caused by tire pressure problems according to the present invention are as follows:

[0102] 1. When there is a minor problem with the tire pressure, but it is not enough for the driver to change the tire or inflate it, this invention ensures that the autonomous vehicle can drive more accurately along the planned trajectory.

[0103] 2. During driving, when the air pressure of a single tire suddenly becomes problematic, the method provided by this invention still compensates for the steering wheel angle to ensure that the autonomous vehicle will not be in danger due to sudden changes in physical hardware while driving at high speed. This effectively ensures the safety, continuity, and adaptability of the autonomous vehicle and can protect the safety of passengers in real time.

[0104] Although the methods described above are illustrated and depicted as a series of actions for the sake of simplicity, it should be understood and appreciated that these methods are not limited by the order of the actions, as some actions may occur in a different order and / or concurrently with other actions from the illustrations and descriptions herein or not illustrated and described herein but which may be understood by those skilled in the art, according to one or more embodiments. As indicated in this application and claims, unless the context clearly indicates otherwise, the words "a," "an," etc., do not specifically refer to the singular and may also include the plural. Generally speaking, the term "comprising" only indicates the inclusion of explicitly identified steps, and these steps do not constitute an exclusive list; the method may also include other steps.

[0105] The embodiments described above are merely further illustrations of the present invention and are not intended to limit the present invention in any other way. The present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding modifications and changes based on the present invention, but all such modifications and changes should fall within the protection scope of the present invention.

Claims

1. A method for compensating for lateral deviation in autonomous driving caused by tire pressure issues, characterized in that, Includes the following steps: Step S1: Real-time acquisition of tire motion information during vehicle operation; the tire motion information includes the linear velocity and angular velocity of tire rolling. Step S2: Calculate the rolling radius of the tire based on the tire's motion information, and determine whether the tire pressure is abnormal using the radius iteration method. The radius iteration method uses a pre-set characteristic parameter γ to represent the difference in the tire's rolling radius in order to determine whether the tire pressure is abnormal. Step S3: Based on the tire's rolling radius and characteristic parameter γ, determine the relationship between tire pressure and tire radius, and identify the location of tires with abnormal tire pressure; and Step S4: Calculate the compensation value of the steering wheel angle based on the characteristic parameter γ; In step S2, when the characteristic parameter γ remains non-zero, the tire pressure is abnormal; the calculation formula for the pre-set characteristic parameter γ is as follows: （1） Among them, R FL R represents the rolling radius of the left front wheel. FR R represents the rolling radius of the right front wheel. RL R represents the rolling radius of the left rear wheel. RR This represents the rolling radius of the right rear wheel.

2. The method for compensating for lateral deviation in autonomous driving caused by tire pressure problems according to claim 1, characterized in that, The formula for calculating the rolling radius of a tire during vehicle operation is as follows: （2） Where R represents the rolling radius of the tire, and V R ω represents the linear velocity of the tire as it rolls. R This represents the angular velocity of the tire rolling.

3. The method for compensating for lateral deviation in autonomous driving caused by tire pressure problems according to claim 2, characterized in that, In step S2, when the rolling radius R is a constant, the calculation formula for the characteristic parameter γ is as follows: （3） Among them, V FL V represents the linear velocity of the left front wheel. FR V represents the linear velocity of the right front wheel. RL V represents the linear velocity of the left rear wheel. RR ω represents the linear velocity of the right rear wheel. FL ω represents the angular velocity of the left front wheel. FR ω represents the angular velocity of the right front wheel. RL ω represents the angular velocity of the left rear wheel. RR This represents the angular velocity of the right rear wheel.

4. The method for compensating for lateral deviation in autonomous driving caused by tire pressure problems according to claim 3, characterized in that, Step S2 also includes iteratively solving for the characteristic parameter γ in equation (3) using the recursive least squares method. The specific steps are as follows: （4） Where A=1; ; ; （5） （6） （7） （8） Where p and A satisfy the following relationship: （9） The termination condition for the iteration is: （10） in, As the termination limit, The value at which the iteration converges is .

5. The method for compensating for lateral deviation in autonomous driving caused by tire pressure problems according to claim 2, characterized in that, Step S3 is as follows: The rolling radius of each tire is calculated by formula (2). Based on the tire radius and characteristic parameter γ, the tire pressure and tire radius are calibrated and the relationship between tire pressure and tire radius is determined. Compare the rolling radius of each tire and determine the location of the tire with abnormal tire pressure.

6. The method for compensating for lateral deviation in autonomous driving caused by tire pressure problems according to claim 1, characterized in that, In step S4, when the tire pressure on one side of the coaxial tire is insufficient, the compensation value of the steering wheel angle is calculated based on the characteristic parameter γ.

7. The method for compensating for lateral deviation in autonomous driving caused by tire pressure problems according to claim 6, characterized in that, Step S4 specifically involves: When the tire pressure difference between the two tires on the same axle exceeds 0.1 kPa, the compensation value for the steering wheel angle is calculated based on the characteristic parameter γ; otherwise, no compensation is made.

8. The method for compensating for lateral deviation in autonomous driving caused by tire pressure problems according to claim 6 or 7, characterized in that, The formula for calculating the compensation value of the steering wheel angle in step S4 is as follows: （11） in, γ is the feature parameter calculated in step S2. Under different tire motion information, γ is a dynamic value. This is the differential pressure coefficient, which is dynamically calibrated based on tire pressure conditions under different circumstances. The calibration coefficient is adjusted to achieve the expected value; lat_error is the lateral error.

9. The method for compensating for lateral deviation in autonomous driving caused by tire pressure problems according to claim 8, characterized in that, When tires on the same side experience abnormal tire pressure simultaneously, the pressure difference coefficient in the dynamic calibration formula (11) And the formula for calculating the characteristic parameter γ is as follows: （12） Where, ω FL ω represents the angular velocity of the left front wheel. FR This represents the angular velocity of the right front wheel; the lateral error lat_error continuously converges to 0 based on the compensation value of the steering wheel angle to calibrate the error.

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