Assessment of adjustable damping in the ride comfort of a baja SAE vehicle

Abstract

The paper presents a case study of a small off-road vehicle and its response to ground excitations regarding the geometrical suspension properties and the variation of adjustable damping parameters, that can change restoring force in fast bump, slow bump and rebound zones. The shock absorber behaviour in force–velocity graphs is obtained from experimental data and introduced in the simulation by a lookup table strategy, without a mathematical model describing the damping behaviour. The analysis is done through a seven degrees-of-freedom model, describing the full vehicle, and assembled in a state space form. Ground excitations are inserted as wheel displacement from random road vibrations and a single road bump, with the use of a roller contact model. The acceleration transmitted to the driver is compared to comfort standards to verify possible discomfort or danger to health damages in long exposure. The outputs are validated with linear potentiometers, showing that the model can accurately predict the shock absorbers behaviour and, consequently, the accelerations transmitted to the driver. To the shock absorbers studied, low bump velocities do not affect significantly exposure risk to vibrations and present a small comfort improvement. Otherwise, through road bumps, a softer regulation ensures a better performance, reducing sprung mass displacement in 31% and accelerations transmitted in 33% at the shock absorber regulation range.