Property Analysis of an X-Coupled Suspension for Sport Utility Vehicles

The influences of fluidic X-coupling of hydro-pneumatic suspension struts on the various suspension properties are investigated for a sport utility vehicle (SUV). The stiffness and damping properties in the bounce, pitch, roll and warp modes are particularly addressed together with the couplings between the roll, pitch, bounce and warp modes of the vehicle. The proposed X-coupled suspension configuration involves diagonal hydraulic couplings among the different chambers of the four hydro-pneumatic struts. The static and dynamic forces developed by the struts of the unconnected and X-coupled suspensions are formulated using a simple generalized model, which are subsequently used to derive the stiffness and damping properties. The properties of the X-coupled suspension are compared with those of the unconnected suspension configuration, in terms of four fundamental vibration modes, namely bounce, roll, pitch and warp, to illustrate the significant effects of fluidic couplings. The results suggest that the X-coupling could help achieve greater roll and pitch stiffness and damping, with negligible effects on the bounce and warp mode properties. It is further shown that the X-coupled struts offer greater design flexibility to achieve better compromise among different conflicting measures. From the results, it was concluded that the proposed X-coupling of the suspension struts could help achieve improved roll stability, handling and pitch control, without sacrificing the bounce ride quality and road-holding performance of SUVs during both the on-and off-road driving conditions.