Ride improvement of vehicle suspensions with switchable inerter based on force cancellation strategy

Inerter is a recent advancement in vehicle suspension that have been shown to be capable of improving vehicle ride comfort, however its ride improvement is less encouraging in the parallel layout. This study investigated the possibility of further ride improvement brought by vehicle suspensions with a switchable parallel inerter instead. In this theoretical study, the inerter was assumed to be on-off switchable based on semi-active force cancellation strategy. A two-degree-of-freedom quarter vehicle model was used to evaluate several cases of suspension system, which included ordinary passive suspension as reference, a system with switchable inerter and a system with both switchable damper and inerter. The model was solved mathematically with random road profile and step profile as ground excitations. Results showed that the use of switchable inerter in parallel to spring and damper in the different test cases was capable of reducing vertical sprung mass acceleration by a healthy 12 %, which is far superior to a mere 2 % achieved by a passive parallel inerter, as well as comparable to that achieved by a switchable damper. When both sprung mass acceleration and dynamic tire load were considered, comparison made on the Pareto fronts indicated that the switchable capability of an inerter managed to further improve the Pareto optimal sets over those obtained for cases with passive inerter.