Nondeterministic Analysis of a Four-Wheeled Model Vehicle Traversing a Simulated Random Terrain

In order to increase confidence in the reliability and accuracy of the linear random vibration theory in predicting vehicular behavior, an experiment was performed with a four-wheeled model vehicle with an independent suspension system. The vehicle has three degrees of freedom - vertical translation, pitch, and roll - and was made to traverse at different speeds, a simulated road bed with randomly distributed surface roughness. Using linear random vibration theory, equations giving the power spectral density of each degree of freedom about the center of gravity of the vehicle were derived as a function of the power spectral density of the vertical displacement of the four wheels. Utilizing both numerical and experimental techniques, a direct comparison was made between theoretical predictions and experimental results.

The linear random vibration theory was found to give reliable predictions at higher speeds and at rougher terrain. Deliberate asymmetrical loading of the model vehicle was found to have little effect in the reliability of the linear random vibration theory predictions.

A comparison between results of linear random vibration theory and a numerical - nonlinear technique has shown the superiority of the former in predicting experimental results and with relatively minimal computing time requirement.