This article describes research which investigates a control strategy for a semi active suspension system which does not rely on the measurement of the distance between the ground and the vehicle body (the road/axle displacement). In this new system the control method is based on a comparison between the response of the actual vehicle and that of a simulation model. In this model the suspension system is termed "semi-active" because the damping coefficient is varied instead of having a force generator acting directly on the system. A sky-hook model is used, and measured inputs such as the wheel to body relative displacement are fed into the model and the ideal response required is calculated. In this case the ideal response is the acceleration of mass M2. This calculated response is then compared with the actual response of a system under identical wheel to body relative displacement measured using an accelerometer. The difference between the results is minimized by adjusting the damper. The algorithm developed using this model is then applied to a two dimensional (two wheeled) model which takes pitching into account, and which considers the 2 wheels to be independent. Since the two wheels are independent, the coupling between the two wheels is not taken into account. The model also gives preference to the drivers comfort by minimising acceleration changes, and does not modify the road holding capacity of the vehicle.
Abstract