Ride Performance Analysis of Semiactive Suspension Systems Based on a Full-Car Model

This paper extends the results for active suspensions obtained by Chalasani in 1986, by evaluating the potential of semiactive suspensions for improving ride performance of passenger vehicles. Numerical simulations are performed on a seven-degree-of-freedom full vehicle model in order to confirm the general trends found for a quarter-car model, used by the authors in an earlier study. This full car model is used not only to study the heave, but also the pitch and roll motions of the vehicle for periodic and discrete road inputs. 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 results of this study obtained with the periodic inputs indicate that the motion of the quarter-car model is not only a good approximation of the heave motion of a full-vehicle model, but also of the pitch and roll motions since both are very similar to the heave motion. The results obtained with the discrete road input show that, for the example used in this study, the hybrid configuration clearly yields better results than the passive configuration when the objective is to minimize different deflections, angles, and accelerations at the same time.