Ride comfort and energy dissipation of vehicle suspension system under non-stationary random road excitation

Response of vehicle suspension system has traditionally been studied under the assumption of stationary road excitation. However, road excitation becomes a non-stationary random input in the time domain when the vehicle travels at a varying speed. In this paper, we investigate the non-stationary response of vehicle suspension under random road excitation. Despite its importance and relevant applications, this problem has not been well addressed in the literature. The non-stationary random road excitations in the time domain are computed using a high precision Gaussian-Legendre integration method. The evolutionary spectral theory is then applied to evaluate the response in the time-frequency domain. Numerical results for a quarter-car model are presented and effects of vehicle acceleration and road roughness on the ride comfort, energy dissipation from the suspension, and time-variant half-power frequency band for the constant speed and various constant acceleration cases are examined. The consideration of energy dissipation provides new insights on the relationships between ride comfort and fuel consumption, which is important for designs of optimized energy-ride comfort suspension systems under nonstationary road excitations.