Analysis and simulation of road profiles

The power spectral density (PSD) estimate is a parameter commonly used to characterize the acceleration of vehicles and, in conjunction with closed-loop random vibration controllers, to simulate the transport environment. The vertical acceleration experienced by the loading tray of road transport vehicles is mainly a function of the type of suspension, load, vehicle speed, and road surface characteristics. While the first three parameters may vary considerably between and during journeys, the statistical parameters used to describe road surface profiles are much less susceptible to change with respect to time. This paper presents a brief analysis and discussion of the spectral and statistical characteristics of actual road surface elevation records. The deviation of the road profile distribution from the Gaussian distribution is revealed, and it is shown that roads of different roughness seem to retain their spectral shape. In addition, a range of statistical parameters are introduced and recommended for use in the classification of road profiles. A technique in which a random vibration controller is used to; simulate road profile spectra by controlling the displacement instead of the acceleration of a shaker table is demonstrated. The technique uses a physical model of a vehicle suspension to account for the dynamic characteristics of the vehicle. Finally, the use of digital signal processors (DSP) together with a time domain adaptive filter control technique for the accurate reproduction of synthesized demand signals is presented.