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 e nvironment. The vertical acceleration experienced by the loading tray of road transport vehicles is mainly a function of the type of suspens ion, load, vehicle speed, and road surface characteristics. While the first three parameters may vary considerably between and during journe ys, the statistical parameters used to describe road surface profiles are much less susceptible to change with respect to time. This paper p resents a brief analysis and discussion of the spectral and statistica l characteristics of actual road surface elevation records. The deviat ion of the road profile distribution from the Gaussian distribution is revealed, and it is shown that roads of different roughness seem to r etain their spectral shape. In addition, a range of statistical parame ters are introduced and recommended for use in the classification of r oad profiles. A technique in which a random vibration controller is us ed to; simulate road profile spectra by controlling the displacement i nstead of the acceleration of a shaker table is demonstrated. The tech nique uses a physical model of a vehicle suspension to account for the dynamic characteristics of the vehicle. Finally, the use of digital s ignal processors (DSP) together with a time domain adaptive filter con trol technique for the accurate reproduction of synthesized demand sig nals is presented.