Stochastic optimal active control of a 2-DOF quarter car model with non-linear passive suspension elements

Active control of the time varying response to a stationary random excitation of a two-degree-of-freedom vehicle model with non-linear passive suspension elements is considered in this paper. The method of equivalent linearization is used to derive the equivalent linear model and the optimal control laws are obtained by using stochastic optimal control theory based on full state information. Velocity squared damping and hysteresis type of stiffness non-linearities are considered. The performance of active suspensions with non-linear passive elements is found to be superior to the corresponding passive suspension systems. As a check on the accuracy of the equivalent linearization technique, a Monte Carlo simulation has also been performed. The results are compared with the results obtained from linearized vehicle model and good agreement between the results has been observed. (C) 1998 Academic Press Limited.