Active Control for Single Wheel Suspension of Off-Road Track Vehicle

Abstract

The main objective of ground vehicles suspension system is to isolate a vehicle body (sprung mass) from road irregularities in order to maximize the passenger ride comfort and produce continuous road-wheel contact in order to provide vehicle holding quality. An appropriate active suspension design must resolve the inherent tradeoffs between ride comfort, road holding quality and suspension travel. In this study a robust controller for the active suspension of an off-road, high-mobility tracked vehicle is designed using Quantitative Feedback Theory (QFT). A simulation model of a single suspension unit of the armored personnel carrier vehicle M-113 was used to get a proper active suspension design. Two measured states of the 3 degrees-of-freedom mathematical model were used as feedback signals in a cascaded SISO control system. The nonlinear dynamics of the tracked vehicle suspension unit was represented as a set of linear time invariant (LTI) transfer functions which were identified with the Fourier integral method. Computer simulations of the vehicle with passive and active suspension systems over different terrain profiles are provided. Significant reduction of the vertical accelerations induced to the sprung mass (i.e. ride comfort improvement) was achieved while keeping the road-arm between suspension travel limits (i.e. handling quality). Hence a potential important improvement in cross-country mobility for a wide range of ride conditions could possibly be achieved by application of linear robust control for active suspension design for off-road tracked vehicles.