Vibration Control Schemes of Semi- Active Hydro-Pneumatic Dampers for Military Vehicle Suspension

Abstract

Hydro-pneumatic dampers are widely used in military and heavy vehicle suspension systems, where large suspension travel (more than 20 inches) is expected. Due to the nonlinear characteristics of these elements, suspension system performance and in particular ride comfort and road handling capabilities of the vehicle are altered. Although these nonlinear characteristics are inherent in nearly all vehicles suspension systems, their effects are dominant in certain maneuvers and especially in off-road conditions where the suspension system experiences rather large displacements. This paper investigates the control of a hydropneumatic damper suspension system, a highly nonlinear system comprised of a pneumatic spring (gas-spring) and a hydraulic damper. First, the hydro-pneumatic damper of a military vehicle is modeled. The model is validated using experiments performed with a dynamometer test machine. Based on the validated model, a 2DOF quarter car model is developed, simulated and analyzed. Secondly, the performance of two well-known semiactive control methods - Skyhook and Rakheja-Sankar (R-S) - are investigated as applied to suspension control in the 2DOF car model. To analyze the performance of these control strategies in the suspension systems where the nonlinear components exist, the method of averaging is deployed. Finally, a new control strategy based on Skyhook and R-S is proposed to address ride comfort and road handling utilizing the variable stiffness gas-spring together with a semiactive damper. The results of this new controller are then compared to that of several well known suspension control methods such as Skyhook to demonstrate the effectiveness of the method.