Study On The Evaluation And Analysis Technology Of Road Roughness

Road roughness is a complex and important issue which refers to person, vehicle and road. The fundamental relationship found from the AASHTO road test shows that approximately 95% of the PSI is contributed by roughness. However, almost all the current used road roughness indices such as the International Roughness Index (IRI), the Mean Square Deviation (σ), the Power Spectral Density (PSD), the Root Mean Square Vertical Acceleration (RMSVA), etc are statistical, and they do not retain the actual detailed contents of profiles that play a important role in studying on roughness and ride comfort. This causes that different road sections may have the similar index value. This paper studys on road wave and vehicle response according to the shortages of IRI,σand PSD.This paper indicates that variation characteristic of road wave can be represented in frequency domain but not in distance domain using the Fourier transform. So the S-transform is proposed after comparing the common time-frequency analysis methods. The S-transform is a new multiresolution time-frequency analysis method which is lossless and reversible. It can represent a energy spectral density (ESD) distribution through which composition of road wave could be determinated both in distance and frequency domains. In order to analyse the relationship between road wave and vehicle vibration, this paper establishes a half vehicle-road model with four freedom degrees and the time domain simulation system of the model is built in Matlab. Using this system the accelerations of vibration of centroid of autobody are calculated with different input variables which are road wave amplitude, wavelength and vehicle parameters. Through analyzing the results the relationship between vibration of centroid of autobody and amplitude is achieved, and sensitive wavelength of vibration of centroid of autobody is related to wheelbase, modality inherent frequency of autobody and vehicle speed. Finally the weighted ESD is proposed to be a supplement evaluation of roughness.The practical examples are analyzed using the weighted ESD and the current used road roughness indices such as IRI,σand PSD. And based on the analysis, some suggestions of road roughness evaluation are put forward.