A Generalized Model of a Class of Interconnected Hydro-Pneumatic Suspensions and Analysis of Pitch Properties

Abstract

The static and dynamic properties of pitch-interconnected hydro-pneumatic vehicle suspensions are derived using a generalized analytical model. The suspensions incorporate two compact struts with integrated gas chambers and damping valves within each unit. The struts provide superior flexibility in realizing fluidic couplings, while offering large effective working area. The proposed suspension configurations consist of hydraulic, pneumatic or hybrid fluidic couplings between the front and rear suspension struts. The coupling effects due to different interconnected suspensions are established through the mathematical formulations. A generalized model of the hydro-pneumatic suspensions is developed that could be applied for either the roll or pitch plane of the vehicle, permitting analyses of suspension forces in a very simple manner. The 7-DOF pitch plane model of a heavy vehicle is analyzed to derive the relative vertical and pitch properties of different suspension configurations, in terms of suspension rates, pitch stiffness, bounce and pitch mode damping properties. The results suggest that the use of fluidic interconnections could yield considerable design flexibility and reduced coupling between the bounce and pitch stiffness properties, while the hydraulic and hybrid fluidic couplings offer added flexibility in tuning the bounce and pitch damping characteristics. The influence of load distribution on the bounce and pitch stiffness properties is also explored.