| CPC G06F 30/17 (2020.01) [G01J 5/00 (2013.01); G01J 2005/0077 (2013.01)] | 4 Claims |
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1. A method for predicting a vibration of a bicycle when being rode on a road, applied to a system for predicting the vibration of the bicycle,
wherein the system comprises:
a support frame arranged on the road and configured to support a rear wheel of the bicycle in such a manner that the rear wheel of the bicycle is off ground;
a fixing belt configured to fix spokes of a front wheel and a front fork of the bicycle to prevent the front wheel from rotating during a test;
a level bubble installed onto the front fork of the bicycle;
an infrared thermal camera arranged on the road and configured to measure a surface temperature of the road in a road test zone;
a humidity sensor configured to measure a surface relative humidity of the road in the road test zone; and
a pressure film arranged in the road test zone, wherein the front wheel of the bicycle is pressed against the pressure film at beginning of the test,
wherein the method comprises:
a step S1 of removing sundries covering a surface of a tested asphalt road;
a step S2 of measuring the surface temperature of the road in the road test zone by the infrared thermal camera and measuring the relative surface humidity of the road by the humidity sensor;
a step S3 of placing the rear wheel of the bicycle onto the support frame and fixing the spokes of the front wheel and the front fork of the bicycle together by the fixing belt to avoid a deviation generated during the test;
a step S4 of cutting the pressure film into a required dimension and arranging the pressure film steadily at a test point in such a manner that the pressure film is not in contact with a front tire of the bicycle and the front tire of the bicycle is next to the pressure film before the test starts;
a step S5 of first straddling, by a tester, the bicycle and adjusting an angle of the front tire of the bicycle by observing the level bubble; and then placing, by the tester, the front tire of the bicycle onto the pressure film vertically when it is determined that the front tire of the bicycle is perpendicular to the road;
a step S6 of sitting, by the tester, on a saddle of the bicycle, and keeping a test state stable for a specified period;
a step S7 of removing, by a cyclist, the front tire of the bicycle, and taking away the pressure film and saving the pressure film in a dark environment; and repeating the step S1 through the step S7 to measure at least three pressure films at different positions of each tested road section, and then ending an outdoor test;
a step S8 of digitizing each of the obtained pressure films through a scanner with a scanning mode of a grayscale mode, wherein information recorded by the pressure film in the grayscale mode is converted into a grayscale value ranging from 1 to 255, and a scanning quality is greater than or equal to 600*600 dpi;
a step S9 of determining a unit pixel area of each of the digitized pressure films based on Formula 1;
 where Rp represents an area of one pixel of the digitized pressure film in a real world and has a unit of mm2, w and l respectively represent a width and a length of the pressure film in the real world and have a unit of mm, and pw and pl respectively represent a number of pixels in a direction of the width of the digitized pressure film and a number of pixels in a direction of the length of the digitized pressure film;
a step S10 of calculating an average bearing area Bu, wherein the average bearing area Bw is defined as a ratio of a contact area Ac to a number nk of granular contact regions in a contact interface recorded by each of the digitized pressure films; and first, the contact area Ac between the road and a bicycle tire is calculated based on Formula 2, and then the average bearing area Bu is calculated based on Formula 3:
 where p represents a total number of pixels of each of the digitized pressure film whose grayscale is not equal to 255, and nk represents a number of regions of the digitized pressure film which are distributed in a granular manner;
a step S11 of calculating an average stress peak distance Spa, wherein five grayscale value distribution curves are extracted from each of the digitized pressure films along a forward riding direction by using digital image analysis software, and each of the five grayscale value distribution curves is subjected to a lowpass filtering to improve precision for recognizing a stress peak; according to an inverse correspondence between a grayscale value and a stress value, a grayscale valley corresponds to a stress peak; and the five grayscale value distribution curves are taken every 0.5 cm along a width direction of an image, the average stress peak distance Spa of each of the five grayscale value distribution curves is calculated based on Formula 4, and an average value of the calculated Spa of the five grayscale value distribution curves is reserved,
 where n represents a number of stress peaks of one grayscale distribution curve, and xi+1 and xi respectively represent a coordinate of an (i+1)th stress peak and a coordinate of an ith stress peak on an x-axis in the forward riding direction; and
a step S12 of calculating a predicted vibration value Pv, wherein Spa and Bu are substituted into Formula 5 to calculate the predicted vibration value Pv (m/s2):
Pv=0.145×Bu+0.404×Spa−1.155 Formula 5.
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