Method and device for estimating longitudinal slope of a vehicle

Abstract

The application discloses a vehicle longitudinal slope estimation method and device, and belongs to the technical field of vehicle data processing. The estimation method comprises the following steps: acquiring a vehicle body lateral speed, an original longitudinal acceleration and a pitch angular speed; obtaining a corrected longitudinal acceleration according to the vehicle body lateral speed and the original longitudinal acceleration; obtaining a first pitch angle gravity component according to the corrected longitudinal acceleration and the pitch angular speed; and obtaining a first slope estimation value according to the first pitch angle gravity component. The longitudinal acceleration of the vehicle is corrected through the vehicle body lateral speed, the estimation value of the slope is calculated through the corrected corrected longitudinal acceleration, the coupling interference of the lateral motion is eliminated, and the accuracy of the slope estimation is improved.

Description

Technical Field

[0001] This application relates to the field of vehicle data processing technology, specifically to a method and apparatus for estimating the longitudinal slope of a vehicle. Background Technology

[0002] Vehicle longitudinal slope estimation is one of the key input parameters for vehicle dynamics control. Functions such as automatic transmission shift strategies, adaptive cruise control, and hill start assist all rely on the vehicle's longitudinal slope. Most slope estimation methods are based on longitudinal acceleration sensors and the differential signal of vehicle speed, calculating the road slope using simple dynamic formulas. However, when the vehicle is moving laterally, the sensor measurements become coupled with the lateral acceleration component, causing distortion in the longitudinal acceleration measurement. This, in turn, affects the accuracy of slope estimation and ultimately impacts vehicle driving safety. Summary of the Invention

[0003] This application provides a method and apparatus for estimating the longitudinal slope of a vehicle, aiming to improve the problem of low estimation accuracy of the longitudinal slope of a vehicle when it is in lateral motion.

[0004] In a first aspect, embodiments of this application provide a method for estimating the longitudinal slope of a vehicle, the estimation method comprising the following steps: Obtain the vehicle's lateral velocity, original longitudinal acceleration, and pitch angular velocity; The corrected longitudinal acceleration is obtained based on the vehicle's lateral velocity and the original longitudinal acceleration. The first pitch angle gravity component is obtained based on the corrected longitudinal acceleration and pitch angular velocity; The first slope estimate is obtained based on the gravity component of the first pitch angle.

[0005] In some embodiments, obtaining the vehicle's lateral velocity includes: Obtain lateral acceleration, yaw rate, reference vehicle speed, and front wheel angle; The enable flag is determined based on the lateral acceleration and yaw rate. When the enable indicator is active, the vehicle's lateral velocity is obtained based on the observer model using the yaw rate, reference vehicle speed, and front wheel steering angle. The observer model is used to characterize the relationship between the yaw rate, reference vehicle speed, front wheel steering angle, and vehicle lateral velocity.

[0006] In some embodiments, determining the enable flag based on lateral acceleration and yaw rate includes: If the lateral acceleration is less than a preset lateral acceleration threshold and the yaw rate is greater than a preset yaw rate threshold, the enable flag is determined to be active.

[0007] In some embodiments, the corrected longitudinal acceleration is obtained based on the vehicle's lateral velocity and the original longitudinal acceleration, including: Correction parameters are obtained based on the vehicle's lateral velocity and yaw rate, and the corrected longitudinal acceleration is obtained based on the correction parameters and the original longitudinal acceleration.

[0008] In some embodiments, obtaining the first pitch angle gravity component based on the corrected longitudinal acceleration and pitch angular velocity includes: The rate of change of gravity at the pitch angle is calculated based on the pitch angular velocity. The first pitch angle gravity component is obtained based on the reference vehicle speed, corrected longitudinal acceleration, and pitch angle gravity change rate using Kalman filtering.

[0009] In some embodiments, the estimation method further includes: Get the current slope condition type; The first slope estimate is corrected based on the current slope condition to obtain the second slope estimate.

[0010] In some embodiments, obtaining the current slope condition type includes: If the original longitudinal acceleration is within the range of the error and the gravity component of the second pitch angle, the current slope condition is determined to be a variable slope condition; if the original longitudinal acceleration is not within the range of the error and the gravity component of the second pitch angle, the current slope condition is determined to be a non-variable slope condition. The gravity component of the second pitch angle is obtained from the pitch angular velocity, and the error is the difference between the gravity component of the second pitch angle and the original longitudinal acceleration.

[0011] In some embodiments, correcting the first slope estimate based on the current slope condition type to obtain a second slope estimate includes: The current pitch angle is obtained based on the gravity component of the second pitch angle. When the current slope condition is a variable slope condition, the second slope estimate is obtained by adding the current pitch angle to the first slope estimate. When the current slope condition is a non-variable slope condition, the second slope estimate is obtained by subtracting the current pitch angle from the first slope estimate.

[0012] In some embodiments, the estimation method further includes: The actual vehicle body acceleration is obtained based on the reference vehicle speed. The attenuation coefficient is obtained based on the actual vehicle body acceleration and a preset attenuation coefficient table. The attenuation coefficient table is used to characterize the relationship between the corrected longitudinal acceleration and the attenuation coefficient. The third slope estimate is obtained based on the attenuation coefficient and the second slope estimate.

[0013] Secondly, embodiments of this application provide a device for estimating the longitudinal slope of a vehicle, the device comprising: The data acquisition module is used to acquire the vehicle's lateral velocity, original longitudinal acceleration, and pitch angular velocity. The longitudinal acceleration correction module is used to obtain the corrected longitudinal acceleration based on the vehicle's lateral velocity and the original longitudinal acceleration. The first slope estimation module is used to obtain the first pitch angle gravity component based on the corrected longitudinal acceleration and pitch angular velocity; and to obtain the first slope estimate based on the first pitch angle gravity component.

[0014] This application corrects the longitudinal acceleration of a vehicle by using the lateral velocity of the vehicle body, and calculates the estimated value of the slope using the corrected longitudinal acceleration, thereby eliminating the coupling interference of lateral motion and improving the accuracy of slope estimation. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a flowchart illustrating a method for estimating the longitudinal slope of a vehicle according to an exemplary embodiment of this disclosure; Figure 2 This is a schematic flowchart illustrating the process of obtaining the lateral velocity of a vehicle body using a method for estimating the longitudinal slope of a vehicle according to an exemplary embodiment of this disclosure. Figure 3 This is a flowchart illustrating the process of calculating the lateral velocity of a vehicle body using a method for estimating the longitudinal slope of a vehicle according to an exemplary embodiment of this disclosure. Figure 4 This is a flowchart illustrating the process of calculating a first slope estimate using a vehicle longitudinal slope estimation method provided in an exemplary embodiment of this disclosure. Figure 5 This is a planar driving schematic diagram of a method for estimating the longitudinal slope of a vehicle provided by an exemplary embodiment of this disclosure; Figure 6 This is a planar driving error curve diagram of a method for estimating the longitudinal slope of a vehicle provided by an exemplary embodiment of this disclosure; Figure 7 This is a slope driving diagram illustrating a method for estimating the longitudinal slope of a vehicle provided by an exemplary embodiment of this disclosure; Figure 8 This is a slope driving error curve diagram of a method for estimating the longitudinal slope of a vehicle provided by an exemplary embodiment of this disclosure; Figure 9This is a flowchart illustrating the calculation of the error in a method for estimating the longitudinal slope of a vehicle according to an exemplary embodiment of this disclosure. Figure 10 This is a graph showing the relationship between the second pitch angle gravity component, the original longitudinal acceleration, and the error in a method for estimating the longitudinal slope of a vehicle provided by an exemplary embodiment of this disclosure. Figure 11 This is a curve showing the change of the current pitch angle of a vehicle under continuous acceleration conditions, provided by an exemplary embodiment of the present disclosure for a method of estimating the longitudinal slope of a vehicle. Figure 12 This is a flowchart illustrating a method for estimating the longitudinal slope of a vehicle according to an exemplary embodiment of this disclosure; Figure 13 This is a schematic diagram of the structure of a vehicle longitudinal slope estimation device provided in an exemplary embodiment of this disclosure.

[0017] Explanation of icon numbers: 100. Estimation device; 101. Data acquisition module; 102. Longitudinal acceleration correction module; 103. First slope estimation module; 104. Second slope estimation module; 105. Third slope estimation module. Detailed Implementation

[0018] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0019] In the description of this application, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are used only for the convenience of describing this application 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, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified.

[0020] "A and / or B" includes the following three combinations: A only, B only, and a combination of A and B.

[0021] The use of "applies to" or "configured to" in this application implies open and inclusive language, which does not exclude the applicability to or configuration to devices performing additional tasks or steps. Additionally, the use of "based on" implies openness and inclusivity, because processes, steps, calculations, or other actions "based on" one or more of the stated conditions or values ​​may in practice be based on additional conditions or values ​​beyond those stated.

[0022] In this application, the term "exemplary" is used to mean "used as an example, illustration, or description." Any embodiment described as "exemplary" in this application is not necessarily to be construed as being more preferred or advantageous than other embodiments. The following description is provided to enable any person skilled in the art to make and use this application. Details are set forth in the following description for purposes of explanation. It should be understood that those skilled in the art will recognize that this application can be made without using these specific details. In other instances, well-known structures and processes are not described in detail to avoid obscuring the description of this application with unnecessary detail. Therefore, this application is not intended to be limited to the embodiments shown, but is consistent with the broadest scope of the principles and features disclosed in this application.

[0023] Firstly, this embodiment provides a method for estimating the longitudinal slope of a vehicle, such as... Figure 1 As shown, the estimation method includes the following steps: S101, Obtain the vehicle's lateral velocity, original longitudinal acceleration, and pitch angular velocity.

[0024] Specifically, the lateral velocity of the vehicle body is the velocity of the vehicle in a direction perpendicular to its direction of travel, used to reflect the degree of sideslip or drifting during cornering. The original longitudinal acceleration is the acceleration along the vehicle's direction of travel directly measured by an inertial measurement unit (IMU). The pitch rate is the velocity of the vehicle's rotation about its body in a direction perpendicular to its direction of travel.

[0025] S102. Obtain the corrected longitudinal acceleration based on the vehicle's lateral velocity and the original longitudinal acceleration.

[0026] Specifically, the corrected longitudinal acceleration is the vehicle's actual longitudinal acceleration after removing the influence of the vehicle's lateral velocity from the original longitudinal acceleration.

[0027] When a vehicle turns, its longitudinal acceleration consists of two parts: one part is its own longitudinal acceleration along the direction of the front of the vehicle, and the other part is the additional acceleration caused by yaw. However, the inertial measurement unit can only measure the first part and cannot measure the second part. Therefore, the longitudinal acceleration measured by the inertial measurement unit under turning conditions will be smaller than the theoretical value, which will eventually lead to an underestimation of the slope. Thus, the longitudinal acceleration measured by the inertial measurement unit will produce errors.

[0028] By using the vehicle's lateral velocity to correct the original longitudinal acceleration measured by the inertial measurement unit, the influence of the vehicle's lateral velocity is removed, thus improving the accuracy of the subsequent slope estimation.

[0029] S103. Obtain the first pitch angle gravity component based on the corrected longitudinal acceleration and pitch angular velocity, and obtain the first slope estimate based on the first pitch angle gravity component.

[0030] Specifically, the first pitch angle gravity component is the projection component of the gravitational acceleration caused by the road slope onto the longitudinal direction of the vehicle, and is used to calculate the slope. The first slope estimate is the estimated value of the slope calculated based on the first pitch angle gravity component.

[0031] The longitudinal acceleration of the vehicle is corrected by the lateral velocity of the vehicle body. The estimated value of the slope is calculated by the corrected longitudinal acceleration, which eliminates the coupling interference of lateral motion and improves the accuracy of slope estimation.

[0032] In some embodiments, such as Figure 2 As shown, the lateral velocity of the vehicle body is obtained, including steps A1 to A3.

[0033] A1. Obtain lateral acceleration, yaw rate, reference vehicle speed, and front wheel angle.

[0034] Specifically, lateral acceleration is the acceleration of the vehicle in a direction perpendicular to its direction of travel, measured by an inertial measurement unit (IMU). Yaw rate is the angular velocity of the vehicle's rotation about its vertical axis, generated when the vehicle is turning; it is approximately 0 rad / s when traveling straight, and is also measured by an IMU. Reference speed is the vehicle's longitudinal speed, obtained from wheel speed sensors. Front wheel angle is the front wheel deflection angle output by the steering angle sensor, obtained from the steering wheel sensor and steering ratio.

[0035] A2. Determine the enable flag based on the lateral acceleration and yaw rate.

[0036] Specifically, the enable flag is used to control whether the observer model is activated. The enable flag includes an active state and a deactivated state. The observer model is started when the enable state is active and deactivated when the enable state is deactivated.

[0037] When a vehicle makes sharp turns or turns with large steering inputs, the tires deviate from the linear range, making the single-track dynamics model prone to distortion and significant errors, resulting in large deviations in the estimated gradient. When the vehicle is traveling straight, the yaw rate approaches 0 rad / s, activating the observer model increases computational power and load consumption.

[0038] Therefore, the enable flag is determined by lateral acceleration and yaw rate. The observer model is only started when the enable flag is active. The observer model is started when the steering is large or when making sharp turns to improve calculation accuracy and reduce errors. The observer model is turned off when going straight to reduce the load and computing power consumption.

[0039] In some examples, the enable flag is determined to be active when the lateral acceleration is less than a preset lateral acceleration threshold and the yaw rate is greater than a preset yaw rate threshold.

[0040] The lateral acceleration threshold is a critical value for the vehicle's lateral acceleration. When the vehicle's lateral acceleration is less than the preset threshold, the tire lateral force and sideslip angle have a linear relationship, and the single-track dynamics model calculation is valid. Exceeding this threshold, the tire enters the nonlinear region, and the model fails. The lateral acceleration threshold can be set to 0.35 times the gravitational acceleration to ensure that the tire is within the linear range.

[0041] The yaw rate threshold is a calibrated value for the yaw rate, used to filter out invalid yaw signals caused by minor jitters when driving straight.

[0042] If both the lateral acceleration and yaw rate are less than a preset lateral acceleration threshold and greater than a preset yaw rate threshold, the enable flag is set to active, and the observer model is started.

[0043] A3. When the enable indicator is active, the vehicle's lateral velocity is obtained based on the observer model according to the yaw rate, reference vehicle speed, and front wheel steering angle.

[0044] Specifically, the observer model is used to characterize the relationship between yaw rate, reference vehicle speed, front wheel steering angle, and vehicle lateral velocity. The observer model can calculate the vehicle's lateral velocity based on data measured by existing sensors such as the vehicle's inertial measurement unit, wheel speed sensors, and steering angle sensors, thus providing a data foundation for subsequent corrections to the vehicle's longitudinal acceleration.

[0045] The observer model can be a Romberg observer, as shown in the following formula: ; in, For state vectors, For control vectors, For the output vector, Here is the state transition matrix. For the control matrix, For the output matrix, This is the gain coefficient matrix.

[0046] State vector for: ; in, for Lateral velocity at time t, in units of , for The yaw rate at time t, in units of .

[0047] Control Vector for: ; in, for Lateral acceleration at time t, in units of , for The front wheel steering angle at any given time is measured in degrees.

[0048] Output vector for: ; in, for The yaw rate at time t, in units of .

[0049] State transition matrix for: ; in, for Reference speed at any given time, in units of , The algorithm's running cycle, This is the distance from the front axle to the center of gravity, in units of... , For front axle lateral stiffness, This is the distance from the rear axle to the center of gravity, in units of... , For rear axle lateral stiffness, The moment of inertia of the vehicle about its vertical axis (z-axis), expressed in units of 1000 ppm. .

[0050] Control Matrix for: ; in, The algorithm's running cycle, This is the distance from the front axle to the center of gravity, in units of... , For front axle lateral stiffness, The moment of inertia of the vehicle about its vertical axis (z-axis), expressed in units of 1000 ppm. .

[0051] Output matrix for: ; G is the gain coefficient matrix; by adjusting G, the observed... It converges to a suitable value.

[0052] like Figure 3 As shown, the enable flags for obtaining lateral velocity and yaw rate are determined by the inertial measurement unit. When the enable flags are active, the yaw rate, the reference vehicle speed obtained from the wheel speed sensor, and the front wheel steering angle obtained from the steering angle sensor are input into the Romberg observer to calculate the lateral velocity of the vehicle body.

[0053] In some embodiments, obtaining the corrected longitudinal acceleration based on the vehicle's lateral velocity and the original longitudinal acceleration includes: obtaining a correction parameter based on the vehicle's lateral velocity and yaw rate, and obtaining the corrected longitudinal acceleration based on the correction parameter and the original longitudinal acceleration.

[0054] Specifically, the correction parameter is the additional longitudinal acceleration generated by the coupling during vehicle steering. The inertial measurement unit can only collect the vehicle's direct acceleration and cannot collect the additional longitudinal acceleration generated by the steering coupling, resulting in the original longitudinal acceleration measurement value being too small, and the final estimated slope value being smaller than the actual road surface.

[0055] The formula for calculating the correction parameter is: ; in, To correct the parameters, The original longitudinal acceleration is expressed in units of 1 / 2. , The lateral velocity of the vehicle body, in units of , The yaw rate is expressed in units of . .

[0056] In some embodiments, obtaining the first pitch angle gravity component based on the corrected longitudinal acceleration and pitch angular velocity includes: calculating the pitch angle gravity change rate based on the pitch angular velocity; and obtaining the first pitch angle gravity component based on Kalman filtering according to the reference vehicle speed, the corrected longitudinal acceleration, and the pitch angle gravity change rate.

[0057] Specifically, the pitch angular velocity is the rotational speed of the vehicle body about a direction perpendicular to the vehicle's direction of travel, acquired by an inertial measurement unit. The pitch angle gravity change rate is the rate of change of the vehicle body's pitch attitude over time. The first pitch angle gravity component is the gravity projection of the suspension beam pitch angle along the vehicle's longitudinal direction, used to quantify the disturbance caused by the suspension beam to the vehicle's acceleration.

[0058] The pitch angular velocity is measured by an inertial measurement unit, and the angle is obtained by integrating the pitch angular velocity. Multiply by the acceleration due to gravity. The gravity component at the first pitch angle is obtained by differentiation.

[0059] The discretization formula for the state equation of Kalman filtering is as follows: ; in, For state vectors, Here is the state transition matrix. This is the process noise matrix.

[0060] State vector for: ; in, for Reference speed at any given time, in units of , for acceleration at time t, in units of , for time The derivative, for The first pitch angle gravitational component at time t, in units of , This is the derivative of the gravitational component at the first pitch angle.

[0061] State transition matrix for: ; in, This represents the step size for the algorithm.

[0062] A matrix is ​​defined as , This indicates that the random variable follows a multivariate normal distribution.

[0063] The discretization formula for the observation equation is shown below: ; in, for Reference speed at any given time, in units of , To correct for longitudinal acceleration, the unit is... , This is the derivative of the gravitational component at the first pitch angle.

[0064] Observation matrix As shown below: ; Measurement noise matrix Defined as: , This indicates that the random variable follows a multivariate normal distribution.

[0065] Using the Kalman equations described above, the following can be estimated by adjusting matrices Q and R: This allows us to further obtain the slope. .

[0066] like Figure 4 As shown, the vehicle's lateral velocity is acquired, and the original longitudinal acceleration and pitch angular velocity are collected via an inertial measurement unit. A reference vehicle speed is obtained using wheel speed sensors. The lateral velocity and original longitudinal acceleration are preprocessed to obtain a corrected longitudinal acceleration, and the pitch angular velocity is preprocessed to obtain the pitch angle gravity change rate. The reference vehicle speed, corrected longitudinal acceleration, and pitch angle gravity change rate are then used to calculate the first pitch angle gravity component based on Kalman filtering. The slope angle is then calculated based on this first pitch angle gravity component.

[0067] Since the inertial measurement unit is mounted on the vehicle body, in actual working conditions, the longitudinal acceleration measured by the inertial measurement unit is obtained by coupling three parts: the longitudinal acceleration of the vehicle, the pitch angle of the vehicle body caused by the suspension deformation, and the slope of the road.

[0068] Taking the acceleration of a vehicle on a flat road as an example, due to the load being transferred to the rear, the rear suspension is compressed, and the vehicle body will have a small upward angle. Therefore, the slope calculated by subtracting the longitudinal acceleration from the vehicle body acceleration using the IMU will have a positive error. Moreover, the greater the acceleration and the softer the suspension, the more severe the vehicle's nose-up, and the greater this error will be.

[0069] The slope estimation formula is shown below: ; ; in, The estimated slope is in degrees. The original longitudinal acceleration measured by the inertial measurement unit, in units of... , This represents the vehicle's actual longitudinal acceleration, in units of... , This represents the actual slope, in units of... , The pitch angle of the vehicle caused by suspension deformation, expressed in degrees.

[0070] like Figure 5 As shown, when driving on a flat surface (0 degrees slope), due to the deformation of the vehicle suspension beam, there is an error between the actual vehicle body plane and the ideal vehicle body plane. Therefore, the comparison between the estimated slope and the actual slope at this time is as follows: Figure 6 As shown, the actual slope is 0 degrees, and the estimated slope is represented by the dashed curve, which is larger than the actual slope.

[0071] Similar errors can also be introduced when a vehicle is driving under varying gradient conditions, such as... Figure 7 As shown, taking an uphill slope as an example, the vehicle's front suspension is compressed, and the vehicle body has a downward angle relative to its theoretical position. In this case, the estimated slope will be smaller than the actual value. Furthermore, under varying slope conditions, the convergence of the estimated slope value will be slower. Figure 8 As shown, the dashed line represents the actual slope, and the solid line represents the estimated slope. Therefore, the estimated slope value has an error.

[0072] To solve the above problems, it is necessary to identify the vehicle's operating condition and correct the estimated slope.

[0073] In some embodiments, the estimation method further includes: obtaining the current slope condition type; and performing a correction on the first slope estimate based on the current slope condition type to obtain a second slope estimate.

[0074] Specifically, since the vehicle's pitch is opposite to the ideal situation when driving on a fixed slope and when the slope changes, it is necessary to first identify the current slope condition type. Based on the current slope condition type, the first slope estimate is corrected to obtain a more accurate second slope estimate.

[0075] In some embodiments, obtaining the current slope condition type includes: if the original longitudinal acceleration is between the error and the gravity component of the second pitch angle, determining the current slope condition type as a variable slope condition; if the original longitudinal acceleration is not between the error and the gravity component of the second pitch angle, determining the current slope condition type as a non-variable slope condition.

[0076] Specifically, the gravity component of the second pitch angle is obtained from the pitch angular velocity, and the error is the difference between the gravity component of the second pitch angle and the original longitudinal acceleration.

[0077] like Figure 9As shown, the pitch angular velocity is high-pass filtered to obtain a high-frequency signal, then integrated to obtain a non-divergent pitch angle. The pitch angle is then transformed using a sin trigonometric function and multiplied by the gravitational acceleration. The gravity component at the second pitch angle is obtained. The error is obtained by subtracting the gravity component at the second pitch angle from the original longitudinal acceleration.

[0078] The high-pass filter coefficients need to be calibrated, following two principles. The first principle is to ensure that the integrated value does not diverge continuously; that is, when the vehicle is pitching, the integrated value should not be zero, but when the vehicle is stationary, the integrated value should converge to zero. The second principle is to make the integrated value as large as possible when there is pitching motion.

[0079] The relationship curves between the gravity component at the second pitch angle, the original longitudinal acceleration, and the error are as follows: Figure 10 As shown. When the error < the original longitudinal acceleration < the gravity component of the second pitch angle, the vehicle is transitioning from a flat road to a downhill slope; when the gravity component of the second pitch angle < the original longitudinal acceleration < the error, the vehicle is transitioning from a flat road to an uphill slope.

[0080] The original longitudinal acceleration is either one of the two cases mentioned above, which is a variable slope condition; the other cases are non-variable slope conditions.

[0081] In some embodiments, the correction of the first slope estimate to obtain a second slope estimate is performed according to the current slope condition type, including: obtaining the current pitch angle based on the gravity component of the second pitch angle; if the current slope condition type is a variable slope condition, adding the current pitch angle to the first slope estimate to obtain the second slope estimate; if the current slope condition type is a non-variable slope condition, subtracting the current pitch angle from the first slope estimate to obtain the second slope estimate.

[0082] Specifically, the current pitch angle is the instantaneous attitude angle of the suspension frame, used to characterize the angle of the vehicle body caused by the deformation of the suspension frame, and is unrelated to the actual slope of the road surface.

[0083] After identifying the variable slope condition, the current pitch angle is added to the first slope estimate to obtain the second slope estimate.

[0084] After identifying the non-variable slope condition, the second slope estimate is obtained by subtracting the current pitch angle from the first slope estimate.

[0085] Differentiated compensation is applied based on working conditions to adapt to different working condition types and improve the comprehensiveness of the method's adaptability.

[0086] In some embodiments, the estimation method further includes: obtaining the actual vehicle body acceleration based on the reference vehicle speed; obtaining the attenuation coefficient based on the actual vehicle body acceleration using a preset attenuation coefficient table; and obtaining the third slope estimate based on the attenuation coefficient and the second slope estimate.

[0087] Specifically, the reference vehicle speed is measured by the vehicle's wheel speed sensors, and the actual vehicle acceleration is obtained by differentiating the reference vehicle speed.

[0088] Since the current pitch angle is obtained through high-pass filtering and integration, the effect of high-pass filtering is more pronounced in order to prevent the integral from diverging, i.e., to remove more low-frequency components. Therefore, during continuous acceleration or deceleration of the vehicle, even though the vehicle body always has a pitch angle, the current pitch angle will gradually converge to 0. Thus, the current pitch angle calculated at this time loses its correction effect on the slope. In other words, the correction of the second slope estimate is only effective for a short period of time when the vehicle pitches up or down.

[0089] like Figure 11 As shown, when the vehicle is continuously accelerating, the current pitch angle will become 0.

[0090] Therefore, in order to ensure the accuracy of the slope estimation under continuous acceleration and deceleration conditions, the second slope estimation is corrected based on the actual vehicle acceleration.

[0091] A pre-set attenuation coefficient table is used to characterize the relationship between the actual vehicle acceleration and the attenuation coefficient, with each actual vehicle acceleration corresponding to a specific attenuation coefficient. The attenuation coefficient is then applied to the second slope estimate to obtain the third slope estimate.

[0092] like Figure 12 As shown, the pitch angular velocity is high-pass filtered to obtain a high-frequency signal. The high-frequency signal is integrated to obtain the current, non-divergent pitch angle. The gravity component of the second pitch angle is obtained based on trigonometric function changes and gravitational acceleration. The error is obtained by subtracting the gravity component of the second pitch angle from the original longitudinal acceleration. It is determined whether the original longitudinal acceleration falls between the error and the gravity component of the second pitch angle. If it does, the current pitch angle is added to the first slope estimate; otherwise, the current pitch angle is subtracted to obtain the second slope estimate. A third slope estimate is obtained based on the actual vehicle acceleration and attenuation coefficient table. The third slope estimate is low-pass filtered to obtain the final slope value.

[0093] Secondly, embodiments of this application provide a vehicle longitudinal slope estimation device 100, such as... Figure 13 As shown, the estimation device 100 includes a data acquisition module 101, a longitudinal acceleration correction module 102, and a first slope estimation module 103.

[0094] The data acquisition module 101 is used to acquire the vehicle's lateral velocity, original longitudinal acceleration, and pitch angular velocity.

[0095] Specifically, the lateral velocity of the vehicle body is the velocity of the vehicle in a direction perpendicular to its direction of travel, used to reflect the degree of sideslip or drifting during cornering. The original longitudinal acceleration is the acceleration along the vehicle's direction of travel directly measured by an inertial measurement unit (IMU). The pitch rate is the velocity of the vehicle's rotation about its body in a direction perpendicular to its direction of travel.

[0096] The longitudinal acceleration correction module 102 is used to obtain the corrected longitudinal acceleration based on the vehicle's lateral velocity and the original longitudinal acceleration.

[0097] Specifically, the corrected longitudinal acceleration is the vehicle's actual longitudinal acceleration after removing the influence of the vehicle's lateral velocity from the original longitudinal acceleration.

[0098] When a vehicle turns, its longitudinal acceleration consists of two parts: one part is its own longitudinal acceleration along the direction of the front of the vehicle, and the other part is the additional acceleration caused by yaw. However, the inertial measurement unit can only measure the first part and cannot measure the second part. Therefore, the longitudinal acceleration measured by the inertial measurement unit under turning conditions will be smaller than the theoretical value, which will eventually lead to an underestimation of the slope. Thus, the longitudinal acceleration measured by the inertial measurement unit will produce errors.

[0099] By using the vehicle's lateral velocity to correct the original longitudinal acceleration measured by the inertial measurement unit, the influence of the vehicle's lateral velocity is removed, thus improving the accuracy of the subsequent slope estimation.

[0100] The first slope estimation module 103 is used to obtain the first pitch angle gravity component based on the corrected longitudinal acceleration and pitch angular velocity; and to obtain the first slope estimate based on the first pitch angle gravity component.

[0101] Specifically, the first pitch angle gravity component is the projection component of the gravitational acceleration caused by the road slope onto the longitudinal direction of the vehicle, and is used to calculate the slope. The first slope estimate is the estimated value of the slope calculated based on the first pitch angle gravity component.

[0102] The longitudinal acceleration of the vehicle is corrected by the lateral velocity of the vehicle body. The estimated value of the slope is calculated by the corrected longitudinal acceleration, which eliminates the coupling interference of lateral motion and improves the accuracy of slope estimation.

[0103] In some embodiments, a second slope estimation module 104 is further included, which is used to obtain the current slope condition type and perform a correction on the first slope estimate based on the current slope condition type to obtain a second slope estimate.

[0104] Specifically, since the vehicle's pitch is opposite to the ideal situation when driving on a fixed slope and when the slope changes, it is necessary to first identify the current slope condition type. Based on the current slope condition type, the first slope estimate is corrected to obtain a more accurate second slope estimate.

[0105] In some embodiments, obtaining the current slope condition type includes: if the original longitudinal acceleration is between the error and the gravity component of the second pitch angle, determining the current slope condition type as a variable slope condition; if the original longitudinal acceleration is not between the error and the gravity component of the second pitch angle, determining the current slope condition type as a non-variable slope condition.

[0106] In some embodiments, a third slope estimation module is further included, which is used to obtain the actual vehicle body acceleration based on the reference vehicle speed, obtain the attenuation coefficient based on the actual vehicle body acceleration and a preset attenuation coefficient table, and obtain the third slope estimation value based on the attenuation coefficient and the second slope estimation value.

[0107] Specifically, in order to ensure the accuracy of the slope estimation under continuous acceleration and deceleration conditions, the second slope estimation is corrected based on the vehicle's acceleration.

[0108] A pre-set attenuation coefficient table is used to characterize the relationship between the actual vehicle acceleration and the attenuation coefficient, with each actual vehicle acceleration corresponding to a specific attenuation coefficient. The attenuation coefficient is then applied to the second slope estimate to obtain the third slope estimate.

[0109] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0110] The foregoing has provided a detailed description of a method and apparatus for estimating the longitudinal slope of a vehicle according to embodiments of this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are only for the purpose of helping to understand the method and its core ideas. At the same time, those skilled in the art will recognize that there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for estimating the longitudinal slope of a vehicle, characterized in that, The estimation method includes the following steps: Obtain lateral acceleration, yaw rate, raw longitudinal acceleration, and pitch rate; The enable flag is determined based on the lateral acceleration and the yaw rate, and the vehicle lateral velocity is obtained when the enable flag is in an active state. The corrected longitudinal acceleration is obtained based on the vehicle's lateral velocity and the original longitudinal acceleration. The first pitch angle gravity component is obtained based on the corrected longitudinal acceleration and the pitch angular velocity; The first slope estimate is obtained based on the gravity component of the first pitch angle; Based on the current slope condition type, the first slope estimate is corrected according to the current pitch angle to obtain the second slope estimate; The actual vehicle body acceleration is obtained based on the reference vehicle speed. The attenuation coefficient is obtained based on the actual vehicle body acceleration using a preset attenuation coefficient table, which is used to characterize the relationship between the actual vehicle body acceleration and the attenuation coefficient. The third slope estimate is obtained based on the attenuation coefficient and the second slope estimate. The third slope estimate is low-pass filtered to obtain the final slope value.

2. The estimation method according to claim 1, characterized in that, Acquiring the vehicle's lateral velocity when the enable indicator is active includes: Obtain reference vehicle speed and front wheel steering angle; When the enable flag is in an active state, the vehicle lateral velocity is obtained based on the yaw rate, the reference vehicle speed, and the front wheel steering angle using an observer model. The observer model is used to characterize the relationship between the yaw rate, the reference vehicle speed, the front wheel steering angle, and the vehicle lateral velocity.

3. The estimation method according to claim 2, characterized in that, The enable flag is determined based on the lateral acceleration and the yaw rate, including: If the lateral acceleration is less than a preset lateral acceleration threshold and the yaw rate is greater than a preset yaw rate threshold, the enable flag is determined to be active.

4. The estimation method according to claim 2, characterized in that, The corrected longitudinal acceleration is obtained based on the vehicle body's lateral velocity and the original longitudinal acceleration, including: The correction parameters are obtained based on the vehicle body lateral velocity and the yaw rate, and the corrected longitudinal acceleration is obtained based on the correction parameters and the original longitudinal acceleration.

5. The estimation method according to claim 2, characterized in that, The first pitch angle gravity component is obtained based on the corrected longitudinal acceleration and the pitch angular velocity, including: The rate of change of gravity at the pitch angle is calculated based on the pitch angular velocity. The first pitch angle gravity component is obtained based on the reference vehicle speed, the corrected longitudinal acceleration, and the pitch angle gravity change rate using Kalman filtering.

6. The estimation method according to claim 1, characterized in that, The estimation method further includes: Obtain the current slope condition type.

7. The estimation method according to claim 6, characterized in that, Obtaining the current slope condition type includes: If the original longitudinal acceleration is between the error and the second pitch angle gravity component, the current slope condition type is determined to be a variable slope condition; if the original longitudinal acceleration is not between the error and the second pitch angle gravity component, the current slope condition type is determined to be a non-variable slope condition; wherein the second pitch angle gravity component is obtained from the pitch angular velocity, and the error is the difference between the second pitch angle gravity component and the original longitudinal acceleration.

8. The estimation method according to claim 7, characterized in that, Based on the current slope condition type and the current pitch angle, the first slope estimate is corrected to obtain a second slope estimate, including: The current pitch angle is obtained based on the gravity component of the second pitch angle; When the current slope condition is the variable slope condition, the second slope estimate is obtained by adding the current pitch angle to the first slope estimate. When the current slope condition is the non-variable slope condition, the second slope estimate is obtained by subtracting the current pitch angle from the first slope estimate.

9. A device for estimating the longitudinal slope of a vehicle, characterized in that, The estimation device includes: The data acquisition module is used to acquire lateral acceleration, yaw rate, original longitudinal acceleration, and pitch rate; determine an enable flag based on the lateral acceleration and the yaw rate; and acquire the vehicle body lateral velocity when the enable flag is in an active state. A longitudinal acceleration correction module is used to obtain a corrected longitudinal acceleration based on the vehicle body's lateral velocity and the original longitudinal acceleration. The first slope estimation module is used to obtain the first pitch angle gravity component based on the corrected longitudinal acceleration and the pitch angular velocity; and to obtain the first slope estimate based on the first pitch angle gravity component. The second slope estimation module is used to correct the first slope estimation value based on the current pitch angle according to the current slope condition type, so as to obtain the second slope estimation value. The third slope estimation module is used to obtain the actual vehicle body acceleration based on the reference vehicle speed, and to obtain the attenuation coefficient based on the actual vehicle body acceleration using a preset attenuation coefficient table, which is used to characterize the relationship between the actual vehicle body acceleration and the attenuation coefficient; to obtain the third slope estimation value based on the attenuation coefficient and the second slope estimation value; and to perform low-pass filtering on the third slope estimation value to obtain the final slope value.

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