Non-Dimensional Analysis of the Performance of Semiactive Vehicle Suspensions

An analytical study that evaluates the response characteristics of a two-degree-of freedom quarter-car model using passive and semi-active dampers is provided as an extension to the results published by Chalasani for active suspensions. The behavior of a semi-actively suspended vehicle is evaluated using the hybrid control policy, and compared to the behavior of a passively suspended vehicle. The relationship between vibration isolation, suspension deflection, and road-holding is studied for the quarter-car model. Three performance indices are used as a measure of vibration isolation (which can be seen as a comfort index), suspension travel requirements, and road-holding quality. These indices are based on the mean square responses to a white noise velocity input for three motion variables: the vertical acceleration of the sprung mass, the deflection of the suspension, and the deflection of the tire, respectively. The results of this study indicate that the hybrid control policy yields better comfort than a passive suspension, without reducing the road-holding quality or increasing the suspension displacement for typical passenger cars.