A road surface recognition method based on height sensor

Abstract

The present application relates to the field of automobile suspension control, in particular to a road surface identification method based on height sensor, which collects suspension dynamic travel signals in real time through height sensor, calculates road unevenness evaluation index using suspension dynamic travel, compares with the set reference index in time to judge road unevenness grade, and simultaneously calculates road excitation frequency in real time using zero-crossing method based on suspension dynamic travel signals, which is used for vibration control of suspension controller, thus being beneficial to improve tire grounding and vehicle comfort, and having good real-time performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of automobile suspension control, in particular to a road surface identification method based on height sensors. BACKGROUND

[0002] With the development of automobile chassis by-wire suspension technology, the application of damping adjustable shock absorber (CDC system) and air spring (ECAS system) is becoming more mature. In order to control the air spring, a height sensor for measuring the suspension stroke needs to be installed on the vehicle equipped with CDC and ECAS systems. In order to make the performance of CDC and ECAS system more superior under different road surfaces, it is required that the vehicle sensing system can identify the road surface in real time online, and then adjust the control parameters and control strategies under different road surfaces, so as to achieve better control effect.

[0003] At present, the road surface identification method is mainly based on the following two aspects: one is to use a camera to process the collected image signals and then obtain road feature data, which requires high hardware cost and complex algorithm; the other is to use height or acceleration sensors to perform time domain or frequency domain analysis to obtain road feature parameters, which is based on the vehicle itself sensors without additional hardware cost, but requires a suitable algorithm to reduce the calculation cost.

[0004] The patent application with the publication number CN110001335A discloses a road surface grade identification system and method based on suspension dynamic travel, wavelet denoising and signal interception processing are performed on the sampled vehicle speed signal and each suspension dynamic travel signal, and the estimation value of the road surface roughness coefficient of each suspension under a given distance is calculated, a feature matrix is established, and the similarity of the feature matrix and the judgment matrix of different grade road surfaces is compared to obtain the grade of the road surface under the given distance. However, this method designs a large number of matrix operations, which will occupy more storage space of the suspension system controller, resulting in slow road surface identification speed and even affecting the calculation speed of the vehicle control, and is not suitable for occasions with high real-time performance. The patent application with the publication number CN104309435A discloses a road surface roughness online identification system and method, a linear relationship between the quotient of the mean square value of the sprung mass vertical acceleration of the vehicle and the vehicle speed and the road surface roughness coefficient is calibrated through road tests on a sample vehicle on two different grade roads; when the vehicle is running, the sprung mass vertical acceleration and the vehicle running speed information of the vehicle are collected; finally, the collected information is compared with the calibration results of the sample vehicle, and the current road surface roughness can be obtained in real time. This method is simple to calculate and can meet the real-time requirements of the vehicle, but requires the addition of a sprung acceleration sensor, which increases the hardware cost. Both of the above-mentioned road surface identification methods only analyze the road surface roughness, and do not effectively analyze the road surface excitation frequency in real time, which cannot control the wheel vibration under special working conditions, thereby affecting the tire grounding performance and the comfort of the whole vehicle. SUMMARY

[0005] The purpose of the present application is to overcome the shortcomings of the prior art, and to provide a road surface identification method based on a height sensor, which can judge the road surface roughness grade and the road surface excitation frequency in real time, improve the real-time performance of the suspension controller control, and provide more control parameters for the suspension control to improve the comfort of the whole vehicle.

[0006] The purpose of the present application is achieved by the following scheme: a road surface identification method based on a height sensor, specifically comprising the following steps:

[0007] S1: setting the lateral acceleration threshold and the longitudinal acceleration threshold of the vehicle body, setting the first road surface reference index and the second road surface reference index, and the reference road surface condition of the first road surface reference index is better than that of the second road surface reference index;

[0008] S2: collecting the suspension dynamic travel through the height sensor, and performing band-pass filtering on the collected suspension dynamic travel signal for road surface roughness grade and road surface excitation frequency calculation;

[0009] S3: the road surface roughness grade calculation step is as follows:

[0010] S3-1) comparing the real-time acquired lateral acceleration and longitudinal acceleration with the lateral acceleration threshold value and the longitudinal acceleration threshold value respectively, if the lateral acceleration is less than the lateral acceleration threshold value and the longitudinal acceleration is less than the longitudinal acceleration threshold value, then proceed to the next step, otherwise, stop calculation;

[0011] S3-2) calculating the reference index of the current road surface by using the filtered suspension dynamic travel signal;

[0012] S3-3) comparing the reference index of the current road surface with the first road surface reference index and the second road surface reference index to determine the unevenness level of the current road surface;

[0013] S4: the road surface excitation frequency calculation step is as follows:

[0014] S4-1) performing differential calculation on the suspension dynamic travel signal to obtain the suspension vertical velocity;

[0015] S4-2) determining the zero-crossing point of the suspension vertical velocity according to the relationship between the suspension vertical velocity and time, and recording the zero-crossing point for calculating the time interval and the number of sampling points between the zero-crossing point and the next sampling point after the zero-crossing point;

[0016] S4-3) calculating the suspension vibration frequency of one sampling period according to the time interval between the first zero-crossing point and the next sampling point after the first zero-crossing point, the time interval between the third zero-crossing point and the next sampling point after the third zero-crossing point, and the number of sampling points between the first zero-crossing point and the third zero-crossing point, if the suspension vibration frequency is less than or equal to 3Hz, then end the calculation and output the suspension vibration frequency as the current road surface excitation frequency; otherwise, proceed to the next step;

[0017] S4-4) calculating the suspension vibration frequency of two sampling periods according to the time interval between the first zero-crossing point and the next sampling point after the first zero-crossing point, the time interval between the fifth zero-crossing point and the next sampling point after the fifth zero-crossing point, and the number of sampling points between the first zero-crossing point and the fifth zero-crossing point, if the suspension vibration frequency is less than or equal to 8Hz, then end the calculation and output the suspension vibration frequency as the current road surface excitation frequency; otherwise, proceed to the next step;

[0018] S4-5) calculating the suspension vibration frequency of three sampling periods according to the time interval between the first zero-crossing point and the next sampling point after the first zero-crossing point, the time interval between the seventh zero-crossing point and the next sampling point after the seventh zero-crossing point, and the number of sampling points between the first zero-crossing point and the seventh zero-crossing point, and output the suspension vibration frequency as the current road surface excitation frequency.

[0019] Preferably, the lateral acceleration threshold value and the longitudinal acceleration threshold value of the vehicle body are determined according to the change of the vehicle body posture under different lateral and longitudinal accelerations.

[0020] Preferably, the reference road surfaces corresponding to the first road surface reference index and the second road surface reference index are determined based on vehicle comfort indexes.

[0021] Preferably, the time interval is calculated according to the following formula:

[0022]

[0023] In the formula, T n T is the time interval between the current zero-crossing point and the next sampling point after that zero-crossing point; sample V is the sampling period of the altitude sensor; n V represents the vertical velocity of the suspension at the sampling point preceding the current zero-crossing point. n+1 This represents the vertical speed of the suspension at the sampling point one after the current zero-crossing point.

[0024] Preferably, the formula for calculating the suspension vibration frequency over one sampling period is:

[0025]

[0026] In the formula, f onecycle The current suspension vibration frequency is the same as the current road surface excitation frequency; T sample N is the sampling period of the height sensor; N is the number of sampling points within one cycle of suspension vibration; T n T represents the time interval between the first zero-crossing point and the sampling point following the first zero-crossing point within the current cycle of suspension vibration. n+2 The time interval between the third zero-crossing point and the sampling point after the third zero-crossing point within the current cycle of suspension vibration.

[0027] Preferably, the formula for calculating the suspension vibration frequency over two sampling periods is:

[0028]

[0029] In the formula, f twocycle The current suspension vibration frequency is the same as the current road surface excitation frequency; T sample N is the sampling period of the height sensor; N is the number of sampling points within two cycles of suspension vibration; T n T represents the time interval between the first zero-crossing point and the sampling point following the first zero-crossing point within the current two cycles of suspension vibration. n+4 The time interval between the fifth zero-crossing point and the sampling point after the fifth zero-crossing point within the current two cycles of suspension vibration.

[0030] Preferably, the formula for calculating the suspension vibration frequency over three sampling periods is:

[0031]

[0032] In the formula, fthreecycle is the current road surface excitation frequency; T sample is the sampling period of the height sensor; N is the number of sampling points in three sampling periods of suspension vibration; T n is the time interval between the first zero-crossing point in the current three sampling periods of suspension vibration and the sampling point after the first zero-crossing point; T n+6 is the time interval between the seventh zero-crossing point in the current three sampling periods of suspension vibration and the sampling point after the seventh zero-crossing point.

[0033] Preferably, the lateral acceleration and the longitudinal acceleration are obtained in real time from the ESP system of the vehicle.

[0034] With the above scheme, the road unevenness level and the road excitation frequency are calculated in real time through the suspension dynamic stroke signal, which is used for the control strategy and algorithm development of the subsequent CDC system and ECAS system, and the suspension system can have good performance under different road conditions, which can effectively improve the comfort of the vehicle; the evaluation index of the road is calculated by using the suspension dynamic stroke signal collected by the height sensor and compared with the set reference index to obtain the current road unevenness level, and the reference index is set according to ISO 8608 (Road surface profile. Measurement data report), the actual vehicle model, and the comfort requirement, that is, it is beneficial to different performance goals and real vehicle road evaluation of different suspension systems of different vehicles, and targeted control is facilitated, at the same time, the application range is wide, and it can be effectively promoted; the data collected by the original height sensor of the vehicle with air springs is used for calculation, which avoids increasing the hardware cost, and the calculation is simple, and the road unevenness level can be obtained in real time, and the real-time performance is good; the road excitation frequency is calculated by using the zero-crossing method, the calculation time is short, the real-time performance is high, and the hardware memory requirement is low; the road excitation frequency is divided into three frequency bands, i.e., low (<3Hz), medium (3Hz~8Hz), and high (>8Hz), and the average vibration frequency of one period, two periods, and three periods is calculated respectively, so as to reduce the influence of high-frequency interference on the identification result.

[0035] The application will be further described below in conjunction with the drawings and specific embodiments in the specification. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 is the calculation flowchart of the application;

[0037] Figure 2 is the relationship diagram of the suspension dynamic stroke and the vehicle driving distance of the application, and the relationship diagram of the evaluation index and the dynamic stroke integral result;

[0038] Figure 3 is the comparison diagram of the simulation results of the frequency band calculation of the suspension vibration frequency and the single period calculation of the suspension vibration frequency of the application;

[0039] Figure 4 Suspension vibration frequency simulation identification result diagram of the present application under 0Hz~20Hz sweep input;

[0040] Figure 5 Road surface inequality evaluation index of the present application Simulation calculation result under A grade and C grade road surface input specified in standard ISO 8608. DETAILED DESCRIPTION

[0041] Reference Figures 1 to 5 A road surface identification method based on height sensor, specifically comprising the following steps:

[0042] S1: setting lateral acceleration threshold value and longitudinal acceleration threshold value of vehicle body, setting first road surface reference index and second road surface reference index, the reference road surface condition of the first road surface reference index is better than that of the second road surface reference index. The lateral acceleration threshold value and longitudinal acceleration threshold value of the vehicle body are determined according to the change of vehicle body posture under different lateral and longitudinal accelerations. The reference road surface corresponding to the first road surface reference index and the second road surface reference index is determined according to vehicle comfort index.

[0043] S2: collecting suspension dynamic travel through height sensor, and using the collected suspension dynamic travel signal after band-pass filtering for road surface inequality grade and road surface excitation frequency calculation;

[0044] S3: the road surface inequality calculation steps are as follows:

[0045] S3-1) acquiring the lateral acceleration and longitudinal acceleration from the ESP system of the vehicle in real time, comparing the acquired lateral acceleration and longitudinal acceleration with the lateral acceleration threshold value and longitudinal acceleration threshold value respectively, if the lateral acceleration is less than the lateral acceleration threshold value and the longitudinal acceleration is less than the longitudinal acceleration threshold value, it is considered that the change of vehicle body posture caused by lateral and longitudinal operation is small, at this time, the change of suspension dynamic travel can be considered to be affected only by road surface excitation, and the next step is performed, otherwise, the calculation is stopped;

[0046] S3-2) calculating the evaluation index of current road surface by using the filtered suspension dynamic travel signal;

[0047] The calculation method of the evaluation index of current road surface is as follows:

[0048] S3-2-1) integrating the absolute value of suspension dynamic travel within a specified vehicle driving distance to obtain real-time integral value; the specified vehicle driving distance is determined according to vehicle type and sensitivity and accuracy requirement of road surface inequality identification result, in the embodiment, the specified vehicle driving distance is 5 meters;

[0049] The calculation formula is as follows:

[0050]

[0051] In the formula, E i is the road evaluation index in the ith driving distance, S i+1 is the end point of the ith driving distance, S i is the start point of the ith driving distance, S i+1 - S i = 5 m, H i is the suspension dynamic travel in the ith driving distance;

[0052] As Figure 2 shown, it is the relationship between the suspension dynamic travel and the vehicle driving distance in a specified vehicle driving distance. The larger the area between the suspension dynamic travel and the vehicle driving distance, the greater the vibration of the suspension affected by the road input in the current stage, and the higher the road roughness level;

[0053] S3-2-2) Since the suspension dynamic travel is mainly affected by the road input and the vehicle speed, in order to verify the relationship between the road evaluation index specified in step S3-2-1) and the vehicle speed and the road roughness, the real-time integral value of the absolute value of the suspension dynamic travel in the simulation period is calculated, and the average value of the integral value is calculated. The simulation road input uses the A-E level road specified in ISO 8608. The road level specified in ISO 8608 is introduced in order to generate a random road signal for verifying whether the road evaluation index given by the method is reasonable, and is not used as a basis for dividing the road roughness level;

[0054] The average value of the integral value is calculated as follows:

[0055]

[0056] In the formula, E i is the road evaluation index in the ith driving distance calculated by simulation, n is the number of specified driving distances traveled by the vehicle in the simulation period, is the average value of the evaluation index E i in the simulation period;

[0057] represents the average evaluation index of a certain level road traveled at a certain fixed speed in the simulation period. The calculation results are as shown in Table 1.

[0058] Table 1 Evaluation index and related parameter calculation results under different level roads and different speeds

[0059]

[0060] From Table 1, it can be seen that the integral results of different levels at the same speed are quite different, but the higher the speed, the smaller the integral result value, for example, the calculation result of 80km / h under C level road surface is 94, and the calculation result of 20km / h under B level road surface is 89.8, which are close to each other. In order to reduce the influence of speed on the recognition result, a correction coefficient a is introduced, and the calculation method of the correction coefficient is shown in steps S3-2-3) to S3-2-4).

[0061] S3-2-3) Calculate the average value of the integral value of different speeds under the same road roughness level , that is

[0062]

[0063] In the formula, is the average value of the integral value of different speeds under the same road roughness level ; m is the number of simulated speed samples, and in this embodiment, m = 4;

[0064] The calculation result is shown in Table 1 of step S3-2-2).

[0065] S3-2-4) Calculate the correction coefficient under different speeds, and the correction coefficient calculation formula is as follows:

[0066]

[0067] In the formula, a is the correction coefficient, which is actually the ratio of , and the calculation result is shown in Table 1 of step S3-2-2).

[0068] It can be seen that the ratio a corresponding to the same speed under different levels of road surface is basically the same, that is, a is only affected by speed and not affected by the level of road roughness. Therefore, the introduction of the correction coefficient a can effectively exclude the influence of speed on the calculation result of the index, and at the same time, it will not affect the recognition result of the road roughness level.

[0069] S3-2-5) Correct the real-time integral value of the absolute value of the suspension dynamic stroke within the specified vehicle driving distance, and the formula is as follows:

[0070]

[0071] In the formula, is the corrected real-time integral value.

[0072] Repeat step S3-2-2) to calculate the average value of the corrected index corresponding to different speeds under each level of road surface The results are shown in Table 1 in step S3-2-2.

[0073] It can be seen that the average value of the modified evaluation index The influence of vehicle speed is basically excluded, and the calculation results of different grades of road surfaces are obviously different, indicating that the modified evaluation index can be used for identification of the grade of road surface unevenness.

[0074] Figure 5 For real-time simulation results of A-grade road surfaces and C-grade road surfaces calculated by the method, it can be seen that the evaluation index obtained under the conditions of A-grade road surfaces and C-grade road surfaces has good discrimination, indicating that the method can effectively distinguish the unevenness of different grades of road surfaces.

[0075] S3-3) comparing the evaluation index value of the current road surface with the first road surface reference index and the second road surface reference index to determine the unevenness grade of the current road surface;

[0076] The judgment rule of the unevenness grade of the road surface is as follows:

[0077] When the evaluation index of the current road surface is less than the first road surface reference index, it is determined that the road surface grade of the current road surface is excellent, and the road condition is good;

[0078] When the evaluation index of the current road surface is greater than or equal to the first road surface reference index and less than or equal to the second road surface reference index, it is determined that the road surface grade of the current road surface is good, and the road condition is general;

[0079] When the evaluation index of the current road surface is greater than the second road surface reference index, it is determined that the road surface grade of the current road surface is poor, and the road condition is poor.

[0080] In actual application, the greater the difference in unevenness of the reference road surfaces corresponding to the selected first road surface reference index and second road surface reference index, the more accurate the identification result.

[0081] S4: The road surface excitation frequency calculation step is as follows:

[0082] S4-1) performing differential calculation on the suspension dynamic stroke signal to obtain the suspension vertical velocity;

[0083] S4-2) determining the zero-crossing point of the suspension vertical velocity according to the relationship between the suspension vertical velocity and time, recording the zero-crossing point for calculating the time interval between the zero-crossing point and the next sampling point and the number of sampling points in the calculation period; when the product of the suspension vertical velocities of two adjacent sampling points is less than or equal to zero, it is considered that there is a zero-crossing point between the two sampling points; the sampling points are the suspension velocity sampling points obtained by differential calculation of the suspension dynamic stroke signal;

[0084] The time interval between the zero-crossing point and the next sampling point is calculated according to the following calculation formula:

[0085]

[0086] In the formula, T n is the time interval between the current zero-crossing and the next sampling point after the zero-crossing; T sample is the sampling period of the height sensor; V n is the suspension vertical velocity of the previous sampling point before the current zero-crossing; V n+1 is the suspension vertical velocity of the next sampling point after the current zero-crossing.

[0087] S4-3) According to the time intervals between the first zero-crossing and the next sampling point after the first zero-crossing, the third zero-crossing and the next sampling point after the third zero-crossing, and the number of sampling points between the first zero-crossing and the third zero-crossing, the suspension vibration frequency of one sampling period is calculated. If the suspension vibration frequency is less than or equal to 3 Hz, the calculation is ended and the suspension vibration frequency is output as the current road excitation frequency. Otherwise, the next step is performed.

[0088] The formula for calculating the suspension vibration frequency of one sampling period is:

[0089]

[0090] In the formula, f onecycle is the current suspension vibration frequency, which is the current road excitation frequency; T sample is the sampling period of the height sensor; N is the number of sampling points in one cycle of suspension vibration; T n is the time interval between the first zero-crossing and the next sampling point after the first zero-crossing in the current cycle of suspension vibration; T n+2 is the time interval between the third zero-crossing and the next sampling point after the third zero-crossing in the current cycle of suspension vibration.

[0091] S4-4) According to the time intervals between the first zero-crossing and the next sampling point after the first zero-crossing, the fifth zero-crossing and the next sampling point after the fifth zero-crossing, and the number of sampling points between the first zero-crossing and the fifth zero-crossing, the suspension vibration frequency of two sampling periods is calculated. If the suspension vibration frequency is less than or equal to 8 Hz, the calculation is ended and the suspension vibration frequency is output as the current road excitation frequency. Otherwise, the next step is performed.

[0092] The formula for calculating the suspension vibration frequency of two sampling periods is:

[0093]

[0094] In the formula, f twocycle is the current suspension vibration frequency, which is the current road excitation frequency; T sampleN is the sampling period of the height sensor; N is the number of sampling points within two cycles of suspension vibration; T n T represents the time interval between the first zero-crossing point and the sampling point following the first zero-crossing point within the current two cycles of suspension vibration. n+4 The time interval between the fifth zero-crossing point and the sampling point after the fifth zero-crossing point within the current two cycles of suspension vibration;

[0095] S4-5) Based on the time interval between the first zero-crossing point and the sampling point after the first zero-crossing point, the time interval between the seventh zero-crossing point and the sampling point after the seventh zero-crossing point, and the number of sampling points between the first zero-crossing point and the seventh zero-crossing point, calculate the suspension vibration frequency for three sampling cycles, and output the suspension vibration frequency as the current road surface excitation frequency.

[0096] The formula for calculating the suspension vibration frequency over three sampling periods is:

[0097]

[0098] In the formula, f threecycle The current suspension vibration frequency is the same as the current road surface excitation frequency; T sample N is the sampling period of the height sensor; N is the number of sampling points in three sampling periods of suspension vibration; T n T represents the time interval between the first zero-crossing point and the next sampling point within the current three sampling periods of suspension vibration. n+6 The time interval between the seventh zero-crossing point and the next sampling point within the current three sampling periods of suspension vibration.

[0099] Figure 4 The output results of the frequency identification method described above are obtained under a 0Hz–20Hz (common vibration frequency for suspension vibration control) sweep frequency signal input. It can be seen that the output frequency identification results of the road excitation frequency identification method of this invention have a high degree of agreement with the actual input sweep frequency signal, exhibiting good accuracy and real-time performance. Dividing the road excitation frequency into three frequency bands—low (<3Hz), medium (3Hz–8Hz), and high (>8Hz)—and calculating the average vibration frequency for one, two, and three cycles respectively aims to reduce the impact of high-frequency interference on the identification results; for example... Figure 3 The figure shown is a comparison of the frequency identification results of a single cycle and the frequency identification results of the present invention under the input of a certain random road surface.

[0100] It can be seen that frequency-band calculation effectively filters out the impact of high-frequency interference signals on the recognition results. Using the calculated road surface unevenness level and road excitation frequency in the subsequent control strategy and algorithm of the steerable suspension system can provide more control parameters, achieve more control functions, and thus improve overall vehicle comfort.

[0101] The output road uneven level and road excitation frequency results are input into the vibration control system of the suspension controller, so that the suspension controller can receive and judge road information in time, and the tire ground contact and the comfort of the vehicle are improved, and the real-time performance is better.

[0102] The above only describes the preferred embodiments of the present application and is not used to limit the present application, and the modifications made by the person skilled in the art without departing from the spirit of the present application fall within the protection scope of the present application.

Claims

1. A road surface recognition method based on a height sensor, characterized in that, Specifically, the following steps are included: S1: Set the lateral acceleration threshold and longitudinal acceleration threshold of the vehicle body, set the first road surface reference index and the second road surface reference index, and the reference road surface condition of the first road surface reference index is better than that of the second road surface reference index. S2: The suspension dynamic travel is collected by the height sensor. The collected suspension dynamic travel signal is bandpass filtered and then used to calculate the road surface inequality level and road surface excitation frequency. S3: The calculation steps for road surface inequality level are as follows: S3-1) Compare the real-time acquired lateral acceleration and longitudinal acceleration with the lateral acceleration threshold and longitudinal acceleration threshold, respectively. If the lateral acceleration is less than the lateral acceleration threshold and the longitudinal acceleration is less than the longitudinal acceleration threshold, proceed to the next step; otherwise, stop the calculation. S3-2) Calculate the current road surface evaluation index using the filtered suspension dynamic travel signal; S3-3) Compare the current pavement evaluation index with the first pavement reference index and the second pavement reference index to determine the current pavement inequality level; S4: The steps for calculating the road surface excitation frequency are as follows: S4-1) Perform differential calculation on the suspension dynamic travel signal to obtain the suspension vertical velocity; S4-2) Based on the relationship between the vertical speed of the suspension and time, determine the zero-crossing point of the vertical speed of the suspension and record the zero-crossing point for calculating the time interval between the zero-crossing point and the next sampling point and the number of sampling points in the calculation period. S4-3) Based on the time interval between the first zero-crossing point and the sampling point after the first zero-crossing point, the time interval between the third zero-crossing point and the sampling point after the third zero-crossing point, and the number of sampling points between the first zero-crossing point and the third zero-crossing point, calculate the suspension vibration frequency of one sampling period. If the suspension vibration frequency is less than or equal to 3Hz, the calculation ends and the suspension vibration frequency is output as the current road surface excitation frequency; otherwise, proceed to the next step. S4-4) Based on the time interval between the first zero-crossing point and the sampling point after the first zero-crossing point, the time interval between the fifth zero-crossing point and the sampling point after the fifth zero-crossing point, and the number of sampling points between the first zero-crossing point and the fifth zero-crossing point, calculate the suspension vibration frequency for two sampling periods. If the suspension vibration frequency is less than or equal to 8Hz, the calculation ends and the suspension vibration frequency is output as the current road surface excitation frequency; otherwise, proceed to the next step. S4-5) Based on the time interval between the first zero-crossing point and the sampling point after the first zero-crossing point, the time interval between the seventh zero-crossing point and the sampling point after the seventh zero-crossing point, and the number of sampling points between the first zero-crossing point and the seventh zero-crossing point, calculate the suspension vibration frequency for three sampling cycles, and output the suspension vibration frequency as the current road surface excitation frequency.

2. The road surface recognition method based on a height sensor according to claim 1, characterized in that, The lateral acceleration threshold and longitudinal acceleration threshold of the vehicle body are determined based on the changes in the vehicle body attitude under different lateral and longitudinal accelerations.

3. The road surface recognition method based on a height sensor according to claim 1, characterized in that, The reference road surfaces corresponding to the first road surface reference index and the second road surface reference index are determined based on vehicle comfort indexes.

4. The road surface recognition method based on a height sensor according to claim 1, characterized in that, The time interval is calculated according to the following formula: In the formula, T n T is the time interval between the current zero-crossing point and the next sampling point after that zero-crossing point; sample V is the sampling period of the altitude sensor; n V represents the vertical velocity of the suspension at the sampling point preceding the current zero-crossing point. n+1 This represents the vertical speed of the suspension at the sampling point one after the current zero-crossing point.

5. The road surface recognition method based on a height sensor according to claim 1, characterized in that, The formula for calculating the suspension vibration frequency over one sampling period is: In the formula, f onecycle The current suspension vibration frequency is the same as the current road surface excitation frequency; T sample N is the sampling period of the height sensor; N is the number of sampling points within one cycle of suspension vibration; T n T represents the time interval between the first zero-crossing point and the sampling point following the first zero-crossing point within the current cycle of suspension vibration. n+2 The time interval between the third zero-crossing point and the sampling point after the third zero-crossing point within the current cycle of suspension vibration.

6. The road surface recognition method based on a height sensor according to claim 1, characterized in that, The formula for calculating the suspension vibration frequency over two sampling periods is: In the formula, f twocycle The current suspension vibration frequency is the same as the current road surface excitation frequency; T sample N is the sampling period of the height sensor; N is the number of sampling points within two cycles of suspension vibration; T n T represents the time interval between the first zero-crossing point and the sampling point following the first zero-crossing point within the current two cycles of suspension vibration. n+4 The time interval between the fifth zero-crossing point and the sampling point after the fifth zero-crossing point within the current two cycles of suspension vibration.

7. The road surface recognition method based on a height sensor according to claim 1, characterized in that, The formula for calculating the suspension vibration frequency over three sampling periods is: In the formula, f threecycle The current suspension vibration frequency is the same as the current road surface excitation frequency; T sample N is the sampling period of the height sensor; N is the number of sampling points in three sampling periods of suspension vibration; T n T represents the time interval between the first zero-crossing point and the next sampling point within the current three sampling periods of suspension vibration. n+6 The time interval between the seventh zero-crossing point and the next sampling point within the current three sampling periods of suspension vibration.

8. The road surface recognition method based on a height sensor according to claim 1, characterized in that, The lateral and longitudinal accelerations are obtained in real time from the vehicle's ESP system.

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