Semi-active vibration isolation of a quarter car model under random road excitations using magnetorheological damper

Semi active control systems are becoming increasingly popular because they offer reliability of passive systems combined with high performance and versatility of active control systems but with low power consumptions. As Magnetorheological (MR) fluids can produce good controllable damping force under application of magnetic field, MR damper can be used as effective element in semiactive vibration control. A phenomenological model of MR damper is considered in the present study. Out of various semi-active control strategies, the on-off sky-hook control strategy is used in this work. To check the performance of the proposed on-off controller with MR damper, a single degree of freedom system with MR damper under sinusoidal excitation is first studied. This control scheme is then applied to a two degree-of freedom quarter car model. The parameters of MR damper in the model are varied by changing the input voltage according to the control scheme. The vehicle is assumed to travel with a constant forward velocity and excitation from road irregularities is simulated considering suitable profile spectral density of road. Performances of this controller for two types of road profiles, namely, sinusoidal road profile, random road profile are studied. The control strategy is found to be effective for a quarter car model. To examine optimal damper force vehicle required to isolate the vibration several performance indices have been chosen which are functions of vehicle performance measures such as sprung mass acceleration, vehicle handling and working space.