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

Abstract

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.

Investigation of inerter-based suspension systems for heavy vehicles

“…For comprehensiveness, the quarter vehicle parameter values of a truck and a bus were adopted, as both these heavy vehicle classes were of interest in the study of inerter's performance benefit. These are presented in Table 1 together with those of a typical passenger car as reference [14,25,26]. By quick observation, it is worth noting that each parameter value of heavy vehicles is generally an order of magnitude greater than the corresponding parameter value of a passenger car.…”

“…However, macroscopically, all these still follows the ideal force-acceleration relationship, very much like the displacementresponding behavior of a suspension spring and the velocity-responding behavior of a suspension damper. This is the fundamental inerter definition that is employed in this study, following most of the previous studies concerning inerter in vehicle suspensions [10][11][12][13][14].…”

“…As the name implies, the former has the inerter added in parallel to the spring and damper elements to form a suspension, while the latter contains a serially arranged inerter to the usual vehicle suspension with spring and damper. Within the same context of study, these layouts are often implemented in a two-degree-of-freedom (DOF) quarter vehicle model for theoretical performance analysis and optimization [10][11][12][13][14][15][16]. Following this, these layouts, together with the quarter vehicle model, are illustrated in Fig 1.…”

“…Similarly, in another study [12], the parallel inerter in a quarter vehicle model was subjected to alternative goal programming optimization method, and superior passenger comfort and tire grip were obtained while maintaining equal suspension deflection compared to conventional passive suspension without inerter. Later, with the implementation of variable or switchable inerter in mathematical vehicle models, further enhancement in suspension performance has also become achievable [14]. In a recent study, an inerter-based mechatronic device, consisting of an inerter and an electric motor with passive load, was used to achieve vehicle vibration suppression, and the study demonstrated improvements in road holding without diverse effect on ride comfort and suspension travel [15].…”

“…In line with earlier studies of inerter, the two-DOF quarter vehicle model was taken as the representative system of vehicle in this study. This is a lumped-mass, rigid body mathematical model that is commonly used in studies concerning fundamental suspension analyses, including inerter and semi-active suspensions [14]. While maintaining simplicity, it can be used to obtain qualitatively correct sprung and unsprung mass responses [23] for comparative analyses, and adequate accuracy are achievable without resorting to higher-DOF models [24].…”