阅读说明：本技术 基于印痕法的胎路接触包络轮廓确定方法 (tire road contact envelope contour determination method based on impression method ) 是由 周兴林 杨艳梅 冉茂平 严园 肖神清 邹兰林 于 2019-09-04 设计创作，主要内容包括：本发明公开了一种基于印痕法的胎路接触包络轮廓确定方法,根据轮胎与路面的顶部部分的印痕式接触确定包络轮廓并计算接触面积,最后应用立方差值法进行内插计算,获得轮胎与路面的包络轮廓。解决了三次样条插值计算时因不必要振荡造成包络轮廓与实际包络情况不符合的问题。该方法计算的包络轮廓对应的路表纹理特征参数MPD与初始轮廓对应的具有良好的相关性,印痕包络轮廓MPD与滚动阻力系数的相关性较初始轮廓MPD有一定的提高。(The invention discloses a tire road contact envelope contour determining method based on a footprint method. The problem that the envelope contour is not consistent with the actual envelope condition due to unnecessary oscillation during cubic spline interpolation calculation is solved. The road surface texture characteristic parameter MPD corresponding to the envelope contour calculated by the method has good correlation with the original contour, and the correlation between the impression envelope contour MPD and the rolling resistance coefficient is improved to a certain extent compared with the original contour MPD.)

1. a method for determining a tire road contact envelope contour based on a footprint method is characterized by comprising the following steps:

Step S1: obtaining the impression type contact area S of the top of the rubber tread of the tire in the unit of mm in contact with the road surface²The deformation of the tread between the sharp valleys of the road surface texture is smooth;

step S2: then measuring the surface textures P of different road surfaces, and segmenting the initial texture profiles of the obtained surface textures to obtain a plurality of initial texture profiles P_n；

Step S3: multiple initial texture contours P_nObtaining a corrected texture contour P 'by performing tilt correction'_n；

step S4: from the corrected texture Profile P'_nSetting a horizontal line h corresponding to the maximum elevation value;

Step S5: calculating an area A enclosed by a curve formed by correcting the texture contour and a horizontal line;

Step S6: for each corrected texture profile P'_nIs operated toUntil A is more than or equal to S, keeping the corrected texture contour P'_npoint z having a medium elevation value greater than or equal to the elevation of the plotted horizontal line_iH > h and mark it as a blob, texture profile P 'will be corrected'_nPoint z with a medium height value less than the height of the horizontal line to be drawn_i< h is marked as interpolation point;

Step S7: and finally, carrying out interpolation calculation by using a cubic difference method to obtain an envelope contour of the tire in contact with the pavement impression.

2. The footprint-based tire road-contact envelope contour determination method of claim 1, wherein: step S1, when a impression type contact area S of the top of a tire rubber tread in contact with a road surface is obtained, a visual simulation experiment is carried out on a test road section by using plastic plasticine and a triangular groove plate, a plurality of triangular grooves with triangular sections are arranged on the triangular groove plate at intervals in parallel, the plasticine covers the triangular groove plate, the triangular grooves are used for simulating an uneven area of the road surface, and the triangular grooves form rolling deformation sections after being rolled by wheels; when the tire road is contacted, the automobile tire rolls plasticine to fill the triangular groove; the plasticine fill profile is measured using a laser profilometer.

3. The footprint-based tire road-contact envelope contour determination method of claim 1, wherein: step S1, according to the type and speed of the tested tyre, calculating the correlation coefficient between the measured plasticine contour and the envelope contour theoretically obtained by taking different S values, and selecting the impression type contact area S when the correlation coefficient is maximum.

4. The footprint-based tire road-contact envelope contour determination method of claim 1, wherein: step S2 measures two-dimensional surface textures of m road segments using a road texture test vehicle, where m is a natural number, and the initial profile p of the obtained surface texture is (x)_i，Z_i) Carrying out equal segmentation to obtain a plurality of initial texture contours P_n；x_iAbscissa, Z, of all the discrete points of the initial profile p_iTo be inclined and inclinedThe elevation values i of all discrete points of the initial profile p before the error is eliminated are 0, 1,.., N-1, and N is the discrete data points included in the correction profile.

5. The footprint-based tire road-contact envelope contour determination method of claim 1, wherein: the corrected texture profile P 'after the tilt and offset correction in step S3'_n＝(x_i，z_i) Wherein, in the step (A),

z_i＝Z_i-b₁i-b₀，i＝0，1，...，N-1 (1)

z_iThe elevation value of the corrected texture contour after the inclination and offset errors are eliminated, and N is a discrete data point contained in the corrected contour;

Slope correction factor b₁And offset correction coefficient b₀respectively as follows:

6. The footprint-based tire road-contact envelope contour determination method of claim 1, wherein: the corrected texture profile P 'processed in step S3 is obtained in step S4'_nCorresponding maximum elevation z_mAt a maximum elevation value z_mSetting a height h ═ z_mA horizontal line of k, k ≧ 0, the initial value of k taken to be 0.

7. The footprint-based tire road-contact envelope contour determination method of claim 1, wherein: when the magnitude relationship between A and S is judged in step S6, if A is in the size relationship<S, increasing the k value by one step to set a step length, and returning to the step S4; keeping the corrected texture contour P 'processed in the step S3 until A is more than or equal to S'_nThe middle height value is greater than or equal to the value obtained in the step S4points of horizontal line elevation, i.e. z_iH or more, and marking the mark as a retention point; the corrected texture profile P 'processed in step S3'_nThe point where the middle height value is smaller than the height of the horizontal line obtained in step S4, i.e. z_iH, marking as an interpolation point; the steps S3 to S6 are repeated to process the next initial texture contour until all segmented initial texture contours are processed.

8. The footprint-based tire road-contact envelope contour determination method of claim 1, wherein: step S7 requires returning to step S2 to the initial road table texture contour p, p ═ x_i，Z_i) Making the envelope contour elevation Z of all the reserved points after the judgment of the step S6_i，envEqual to the initial profile elevation, i.e. Z_i，env＝Z_i(ii) a For all interpolation points, according to the envelope contour elevation value Z_i，envThe elevation values Z of two adjacent retention points_iPerforming interpolation calculation, connecting the interpolation point with adjacent reserved points by using smooth lines to obtain envelope contours (x) calculated by different interpolation methods_i,Z_i，env) (ii) a And selecting a linear interpolation method, a cubic spline interpolation method and a cubic interpolation method to perform interpolation calculation, comparing and analyzing envelope contours of different interpolation methods in the step, calculating texture characteristic parameters MPD corresponding to the envelope contours of different interpolation methods, analyzing the relation between the texture characteristic parameters MPD and an initial contour, and finally determining to apply a cubic difference method to perform interpolation calculation to obtain an envelope contour of the tire in contact with the pavement impression.

9. The footprint-contact-envelope-contour-determination method according to claim 1 or 8, characterized in that: the step S7 of determining the envelope contour of the tire in contact with the road surface footprint by applying the cubic difference method to perform interpolation calculation includes the following detailed steps:

Step S8: comparing the envelope contours of different interpolation methods calculated in the analysis step S7, wherein the envelope contour of the cubic spline interpolation method brings unnecessary oscillation due to a smooth curve, and particularly when S is small, the envelope contour does not accord with the actual envelope situation, the envelope contour calculated by the cubic interpolation method does not generate unnecessary oscillation, and meanwhile, the envelope contour is smoother than the contour calculated by the linear interpolation method;

step S9: calculating texture feature parameters MPD corresponding to the envelope contours of different interpolation methods obtained in the step S7, and analyzing the relation between the texture feature parameters MPD and the initial contours MPD, wherein the correlation between the MPD value of the 'pchip' envelope contour MPD and the MPD values of the initial contours MPD, the 'spline' envelope contour and the 'linear' envelope contour MPD is good; therefore, when the envelope contour is calculated by the impression method, a cubic interpolation method 'pchip' is selected for interpolation calculation;

Step S10: and calculating the footprint envelope contours of the m test road sections and corresponding texture characteristic parameters MPD and rolling resistance coefficients by using MATLAB.

Technical Field

The invention belongs to the field of road engineering detection and monitoring, and particularly relates to a method for detecting road surface contact performance.

Background

The tire is made of rubber material with elastic characteristics, the shape of the tire is similar to a cylinder, and if the tire is kept completely undeformed, the contact interface of the rubber tread of the tire and a smooth and dry road surface is a line. However, the rubber tread of a tire is not a completely elastic material, and when the tire is actually in contact with the road surface, the tire is not in close and complete contact with the road surface, and particularly, when the road surface has deep irregular sharp valleys (such as porous asphalt pavement) or deep regular grooves (such as transverse grooved concrete pavement), the incomplete contact phenomenon is more prominent. In fact, the tire road contact process mainly comprises deformation of tire rubber enveloping road surface structure peaks and deformation of rubber between road surface structure sharp valleys. The contact characteristic of the tire road plays an important role in the whole response research of asphalt concrete, is a key role in influencing the skid resistance of the road surface, can research the rolling resistance of the tire road according to the key role, and provides a certain basis for the performance comparison of the tire and the road surface. And the contact profile (envelope profile) of the tire and the road surface can effectively represent the contact characteristic of the tire and the road surface, so that a reasonable and effective envelope profile calculation method is sought, and the method has important guiding significance for accurately representing the research of road surface texture and rolling resistance.

At present, the practical contact between a tire and a road surface is researched by establishing a contact model between rough surfaces by adopting different methods by multiple scholars, a physical model such as a Clapp model or a Hamet-Klein model is generally adopted to calculate the envelope contour of the contact between the tire and the road surface, but the contact between the tire tread and the road surface texture is simulated into single contact between a rigid body and a semi-infinite elastomer by the physical model, the viscoelastic property of the rigid body and asphalt concrete is not consistent, and meanwhile, the actual contact mode between the single contact and the tire road is different, so that the subsequent tire road contact parameters are not accurately obtained.

Disclosure of Invention

In order to solve the above technical problems, the present invention provides a tire road contact envelope contour determining method based on a footprint method, which can truly and effectively characterize the tire road contact characteristics, and ensure that the obtained tire road contact parameters are close to the actual contact state between the tire and the road surface.

In order to solve the technical problems, the technical scheme of the invention is as follows:

a method for determining a tire road contact envelope contour based on a footprint method is characterized by comprising the following steps:

Step S1: obtaining the impression type contact area S of the top of the rubber tread of the tire in the unit of mm in contact with the road surface²The deformation of the tread between the sharp valleys of the road surface texture is smooth;

Step S2: then measuring the surface textures P of different road surfaces, and segmenting the initial texture profiles of the obtained surface textures to obtain a plurality of initial texture profiles P_n；

Step S3: multiple initial texture contours P_nobtaining a corrected texture contour P 'by performing tilt correction'_n；

step S4: from the corrected texture Profile P'_nSetting a horizontal line h corresponding to the maximum elevation value;

Step S5: calculating an area A enclosed by a curve formed by correcting the texture contour and a horizontal line;

step S6: for each corrected texture profile P'_noperation is carried out until A is larger than or equal to S, and the corrected texture contour P 'is reserved'_nPoint z having a medium elevation value greater than or equal to the elevation of the plotted horizontal line_iH > h and mark it as a blob, texture profile P 'will be corrected'_nPoint z with a medium height value less than the height of the horizontal line to be drawn_i< h is marked as interpolation point;

Step S7: and finally, carrying out interpolation calculation by using a cubic difference method to obtain an envelope contour of the tire in contact with the pavement impression.

Further, when the impression type contact area S of the top of the tire rubber tread in contact with the road surface is obtained in the step S1, a visual simulation experiment is carried out on a test road section by using plastic plasticine and a triangular groove plate, a plurality of triangular grooves with triangular sections are arranged on the triangular groove plate at intervals in parallel, the plasticine covers the triangular groove plate, the triangular grooves are used for simulating uneven areas of the road surface, and the triangular grooves form rolling deformation sections after being rolled by wheels; when the tire road is contacted, the automobile tire rolls plasticine to fill the triangular groove; the plasticine fill profile is measured using a laser profilometer.

Further, step S1 is to calculate a correlation coefficient between the measured plasticine profile and the envelope profile theoretically obtained by taking different S values according to the type of the test tire and the test speed, and to select the footprint contact area S when the correlation coefficient is the maximum.

Further, in step S2, the two-dimensional surface texture of m road segments is measured by using the road texture testing vehicle, m is a natural number, and the initial profile p of the obtained surface texture is (x)_i，Z_i) Carrying out equal segmentation to obtain a plurality of initial texture contours P_n；x_iabscissa, Z, of all the discrete points of the initial profile p_iIn order to eliminate the elevation values of all discrete points of the initial profile p before the tilt and offset errors are eliminated, i is 0, 1.

further, the corrected texture profile P 'after the inclination and offset correction is performed in step S3'_n＝(x_i，z_i) Wherein, in the step (A),

z_i＝Z_i-b₁i-b₀，i＝0，1，...，N-1 (1)

z_iThe elevation value of the corrected texture contour after the inclination and offset errors are eliminated, and N is a discrete data point contained in the corrected contour;

Slope correction factor b₁and offset correction coefficient b₀Respectively as follows:

Further, the corrected texture profile P 'processed in the step S3 is obtained in the step S4'_ncorresponding maximum elevation z_mAt a maximum elevation value z_msetting a height h ═ z_mA horizontal line of k, k ≧ 0, the initial value of k taken to be 0.

further, when the magnitude relationship between A and S is judged in step S6, if A < S, the relationship will beThe k value is increased by one step to set the step length, and the step S4 is returned; keeping the corrected texture contour P 'processed in the step S3 until A is more than or equal to S'_nThe point where the middle elevation value is greater than or equal to the elevation of the horizontal line obtained in step S4, i.e., z_iH or more, and marking the mark as a retention point; the corrected texture profile P 'processed in step S3'_nThe point where the middle height value is smaller than the height of the horizontal line obtained in step S4, i.e. z_iH, marking as an interpolation point; the steps S3 to S6 are repeated to process the next initial texture contour until all segmented initial texture contours are processed.

Further, step S7 is as follows: returning to step S2, the road table texture initial contour p, p ═ x_i，Z_i) Making the envelope contour elevation Z of all the reserved points after the judgment of the step S6_i，envEqual to the initial profile elevation, i.e. Z_i，env＝Z_i(ii) a For all interpolation points, according to the envelope contour elevation value Z_i，envThe elevation values Z of two adjacent retention points_iPerforming interpolation calculation, connecting the interpolation point with adjacent reserved points by using smooth lines to obtain envelope contours (x) calculated by different interpolation methods_i，Z_i，env) (ii) a And selecting a linear interpolation method, a cubic spline interpolation method and a cubic interpolation method to perform interpolation calculation, comparing and analyzing envelope contours of different interpolation methods in the step, calculating texture characteristic parameters MPD corresponding to the envelope contours of different interpolation methods, analyzing the relation between the texture characteristic parameters MPD and an initial contour, and finally determining to apply a cubic difference method to perform interpolation calculation to obtain an envelope contour of the tire in contact with the pavement impression.

The step S7 of determining the envelope contour of the tire in contact with the road surface footprint by applying the cubic difference method to perform interpolation calculation includes the following detailed steps:

Step S8: comparing the envelope contours of different interpolation methods calculated in the analysis step S7, wherein the envelope contour of the cubic spline interpolation method brings unnecessary oscillation due to a smooth curve, and particularly when S is small, the envelope contour does not accord with the actual envelope situation, the envelope contour calculated by the cubic interpolation method does not generate unnecessary oscillation, and meanwhile, the envelope contour is smoother than the contour calculated by the linear interpolation method;

Step S9: calculating texture feature parameters MPD corresponding to the envelope contours of different interpolation methods obtained in the step S7, and analyzing the relation between the texture feature parameters MPD and the initial contours MPD, wherein the correlation between the MPD value of the 'pchip' envelope contour MPD and the MPD values of the initial contours MPD, the 'spline' envelope contour and the 'linear' envelope contour MPD is good; therefore, when the envelope contour is calculated by the impression method, a cubic interpolation method 'pchip' is selected for interpolation calculation;

Step S10: and calculating the footprint envelope contours of the m test road sections and corresponding texture characteristic parameters MPD and rolling resistance coefficients by using MATLAB.

Therefore, the invention discloses a tire road contact envelope contour determination method based on a footprint method, which characterizes tire road contact characteristics according to an envelope contour, and firstly assumes that the contact of a tire and a road surface is a footprint-type contact of a top part, and the contact area is Smm²The deformation of the tread between the sharp valleys of the road surface texture is smooth, then the surface texture of different road surfaces is measured by adopting a road surface texture testing vehicle, the initial contour of the obtained texture is evenly divided, and a plurality of initial texture contours P are obtained_nInclination correction is carried out to obtain P'_n(ii) a According to profile P'_nSetting a horizontal line h corresponding to the maximum elevation value, and calculating an area A enclosed by the contour curve and the horizontal line; forward operation is carried out on each correction contour until A is larger than or equal to S, and texture contour P 'is reserved'_nPoints (z) having a medium elevation value greater than or equal to the elevation of the plotted horizontal line_iH) and mark it as a blob, texture profile P'_nPoint (z) where the value of the mid-height is less than the height of the horizontal line drawn_i< h) the marker is an interpolation point; and finally, carrying out interpolation calculation by using a cubic difference method to obtain the envelope contour of the tire and the road surface. The problem that the envelope contour is not consistent with the actual envelope condition due to unnecessary oscillation during cubic spline interpolation calculation is solved. The road surface texture characteristic parameter MPD corresponding to the envelope contour calculated by the method has good correlation with the original contour, and the correlation between the impression envelope contour MPD and the rolling resistance coefficient is improved to a certain extent compared with the original contour MPD. Overcomes the defects that the viscoelastic characteristics of the rigid body and the asphalt concrete are not accordant in the existing profile model, and the true contact mode of single contact and tire road existsA defect in the difference.

Drawings

FIG. 1 is a flow chart of the method of the present invention;

FIG. 2 is a schematic structural diagram of a visual simulation model of the imprinting method of the present invention;

FIG. 3 is a comparison diagram of MPD corresponding to envelope contours and MPD corresponding to initial contours calculated by different interpolation methods according to the present invention;

FIG. 4 is a graph showing the correlation between MPD and original MPD profile according to the interpolation method of the present invention;

FIG. 5 is a comparison of MPD values corresponding to different envelope profiles according to the present invention; (a) a 'pchip' envelope profile and a 'spline' envelope profile; (b) a 'pchip' envelope profile and a 'linear' envelope profile.

FIG. 6 is a graph of the relationship between MPD and rolling resistance coefficient for an initial profile according to the present invention;

FIG. 7 is a graph showing the relationship between MPD and rolling resistance of the footprint envelope profile of the present invention.

Detailed Description

The principles and features of this invention are described below in conjunction with the following drawings, which are set forth by way of illustration only and are not intended to limit the scope of the invention.

The embodiment provides a tire road contact characteristic characterization method based on a footprint method, which comprises the following steps:

Step S1: assuming that the contact of the tire 1 with the road surface 2 is a footprint-type contact of the top portion, the contact area S thereof is determined according to the test tire type and the test speed. As shown in fig. 2, a visual simulation experiment is carried out on a test road section by using plastic plasticine 3 and a wooden triangular groove plate 4, a plurality of triangular grooves 5 with triangular sections at intervals in parallel are arranged on the triangular groove plate 4, the plasticine 3 covers the triangular groove plate 4, the triangular grooves 5 are used for simulating uneven areas of a road surface, the triangular grooves 5 form rolling deformation sections after being rolled by wheels, and the section area of each triangular groove is about 0.3 multiplied by 0.3 square meter of the simulated road surface; when the tire road contacts with the automobile tire, the automobile tire 1 rolls the plasticine 3 to fill the triangular groove 5; and measuring the plasticine filling profile by using a laser profiler so as to obtain the contact area.

Calculating correlation coefficient of the actually measured plasticine profile and the profile obtained by theoretically calculating different S values, and selecting the S value when the correlation coefficient is maximum to be 10mm²。

Step S2: measuring two-dimensional surface textures of 13 road sections by adopting a road texture testing vehicle, and calculating an initial contour p (x ═ of the obtained texture)_i，Z_i) MPD) and the initial contour p is equally divided by an equal division length L of 90 mm. After the equal division, a plurality of initial texture contours P are obtained_n(n＝1，2，3.....)；

Step S3: the following method is adopted for the initial texture contour P in the step S2_nAnd performing tilt correction to eliminate tilt and offset errors of the initial profile. Texture contour P 'after inclination and offset correction'_n＝(x_i，z_i) And (4) showing.

z_i＝Z_i-b₁i-b₀，i＝0，1，...，N-1 (1)

Z_iAnd z_iElevation values of the profile before and after the tilt and offset error elimination, respectively, and N is a discrete data point included in the corrected profile. Slope correction factor b₁And offset correction coefficient b₀The calculation formulas are respectively as follows:

step S4: according to the profile P 'processed by the step S3'_nCorresponding maximum elevation z_mSetting a height h ═ z_m-k (k ≧ 0) horizontal line, the initial value of k taking 0;

step S5: calculating the contour P 'processed by step S3'_nThe area enclosed by the horizontal line h in step S4 is denoted by a. And judging the size relationship between A and S. If A<S, increasing the k value by one step (the step length of the k value can be 0.01mm), and returning to the step 4;

Step S6: until A is more than or equal to S, the menstrual step is retainedTexture contour P 'processed in step S3'_na point (z) at which the middle elevation value is greater than or equal to the elevation of the horizontal line obtained in step S4_ih) or more, and marking the mark as a retention point; the texture profile P 'processed by the step S3'_nA point (z) where the middle height value is smaller than the horizontal line height obtained in step S4_i< h) the marker is an interpolation point; repeating steps S3-S6 to process the next initial texture contour until all segmented initial texture contours are processed;

step S7: return to step S2 is made to the road table texture initial contour p (p ═ x)_i，Z_i) For all the remaining points i judged in the step S6, the envelope contour elevation Z is adjusted_i，envEqual to the initial profile elevation, i.e. Z_i，env＝Z_i(ii) a For all interpolation points, the envelope profile elevation value Z_i，envAccording to the elevation Z of the two adjacent reserved points_iPerforming interpolation calculation, connecting the interpolation point with adjacent reserved points by using a smooth line as much as possible, and performing interpolation calculation by selecting a linear interpolation method ('linear'), a cubic spline interpolation method ('spline') and a cubic interpolation method ('pchip') to obtain envelope profiles (x) calculated by different interpolation methods_i，Z_i，env) The envelope profile is shown in fig. 3.

The method for determining the interpolation calculation by applying the cubic difference method to obtain the envelope contour of the tire in contact with the pavement impression comprises the following detailed steps:

Step S8: comparing the envelope contours of different interpolation methods calculated in the analysis step S7, the envelope contour of the cubic spline interpolation method brings unnecessary oscillation (especially when S is small) due to the smooth curve, so that the envelope contour does not conform to the actual envelope situation, and the envelope contour calculated by the cubic interpolation method does not generate unnecessary oscillation and is smoother than the contour calculated by the linear interpolation method.

Step S9: and calculating the texture feature parameter MPD corresponding to the different interpolation envelope profiles obtained in step S7, wherein the correlations between the MPD of the different interpolation envelope profiles and the original profile MPD are shown in fig. 4, the correlations between MPD values of the different interpolation envelope profiles are shown in fig. 5, and after analyzing fig. 4 and 5, the correlations between the MPD value of the 'pchip' envelope profile and the original profile MPD, the 'spline' envelope profile and the 'linear' envelope profile MPD value are good, the correlations between the MPD value of the 'pchip' envelope profile and the original profile MPD value are up to 98%, and the texture feature parameter MPD of the road surface can be calculated by using the envelope profile calculated by the impression method. Therefore, cubic interpolation ('pchip') should be used for interpolation when envelope contour is calculated by the imprinting method.

Step S10: the rolling resistance of 13 test sections was measured using a trailer, and the R using a TUG was measured²MK.2 trailer, measuring 80km/h, using a light truck reference tire SRTT (indicated by P1 profile) for the measured tire, with a tire pressure of 210kPa and an axle load of 408 kg.

step S11: and calculating the mark printing method envelope contours of the 13 test road sections and corresponding texture characteristic parameters MPD and rolling resistance coefficients by using MATLAB, and analyzing the relationship between the rolling resistance coefficients and the mark printing method envelope contours and the initial envelope contours MPD, wherein the relationship graphs are respectively shown in fig. 6 and fig. 7, and the correlation coefficients of the rolling resistance coefficients and the mark printing method MPD are found to be improved to a certain extent.