Comparison of Roll Properties of Hydraulically and Pneumatically Interconnected Suspensions for Heavy Vehicles

Two different concepts in hydro-pneumatic suspension struts are formulated to conveniently realize either hydraulic or pneumatic interconnections between the struts within different wheel suspensions. The formulation employs a compact strut design that integrates a gas chamber and damping valves within the same unit, and provides considerably enhanced working area to appreciably reduce the operating pressure. A transverse interconnection between the hydro-pneumatic struts in the roll plane is analyzed to investigate its static and dynamic heave and roll properties, and relative potential benefits in enhancing the roll properties, while retaining the soft heave ride. Different hydraulically and pneumatically interconnected strut configurations are analyzed for a heavy vehicle, with appropriate considerations of the fluid compressibility, while the feedback effects associated with the interconnections are emphasized. The vertical and roll properties of different configurations are derived and compared with those of the unconnected struts with an anti-roll bar in terms of suspension rate, roll stiffness and damping characteristics. The influences of various strut and interconnection parameters, and fluid properties on the resulting suspension properties are further presented. The results of the study suggest that both hydraulically and pneumatically roll-interconnected struts could yield high effective roll stiffness, and hydraulic interconnection could further improve the low-speed roll mode damping, so as to achieve improved anti-roll performance, while preserving soft heave ride. The most significant benefit of the interconnected suspension lies in its flexibility for tuning of the suspension properties.