Differential flatness based LQR control of a magnetorheological damper in a quarter car semi-active suspension system

Semi-active suspension is widely used in automotive applications, as it is providing good ride quality at reasonably low cost. Among the various methods available for enhancing ride comfort, magnetorheological (MR) suspension has drawn much attention due to its robustness and fail-safe nature as compared to electrorheological suspension. In semi-active suspension, the damping coefficient of the MR damper is varied by modulating the current supplied to damper coil. In the present work, a quarter car with semi-active suspension system is modeled and its performance is studied through simulation under the MATLAB / Simulink environment. A hybrid control algorithm consisting of differential flatness along with LQR (linear quadratic regulator) is proposed to vary the current input for the magnetorheological damper for reducing the sprung mass acceleration, jerk and to improve ride quality. The simulation results also show that the performance of semi-active suspension that uses magnetorheological damper along with developed hybrid algorithm is superior to the LQR controlled suspension, when subjected to random road profiles.