The Effect of Dual-Rate Suspension Damping on Vehicle Response to Transient Road Inputs

The acceleration response of road vehicles to shock inputs from road irregularities such as bumps and hollows is an important consideration in the design of vehicle suspensions and damping characteristics, in particular. In this paper, the influence of the damper on the shock response of a simple vehicle model is considered. An analysis is presented of a single degree-of-freedom model subjected to a transient displacement input. Simple approximate expressions are given for the peak acceleration during an impulse of both short and long durations compared to the natural period, from which the role of the damper is clearly apparent. For impulses of short duration the peak acceleration occurs during the impulse and is shown to be approximately proportional to the damping ratio. Corollary to this, the peak acceleration can be reduced by switching the damper to a lower value during the impulse. The potential benefits of doing so are illustrated through numerical simulation, and a simple formula is given for the maximum possible reduction in peak acceleration. The results are also contrasted with those of a conventional dual-rate automotive damper model. The switchable damper is found to offer sufficient benefit to warrant further investigation.