Effect of Non-Linear Components on the Performance of a Hydro -Pneumatic Slow-Active Suspension System

Abstract

In this work, the effects of component non-linearities on the ride performance of a hydro-pneumatic slow-active suspension system are studied theoretically. Based on the quarter car linear model, linear optimal control theory is used to calculate the feedback and feedforward gains. These gains are used in both linear and non-linear models with and without preview control. The Pade approximation technique is used to represent the preview time resulting from a preview sensor mounted on the vehicle front bumper to measure the road irregularities ahead of the front wheel. The results on a typical major road showed that at similar r.m.s. values of suspension working space, the non-linear slow-active system with preview provided a 28 per cent improvement in ride comfort and a 17 per cent reduction in dynamic tyre load compared with a passive system. However, the inclusion of non-linear effects of the components increases the ride comfort acceleration by 10 per cent and suspension working space by 12 per cent compared to the equivalent linear model at approximately equal values of r.m.s. dynamic tyre load.