Analysis of Active Suspension Performance Improvement Based on Introducing Front/Rear LQ Control Coupling

Abstract

The paper investigates the potential of improving vehicle ride comfort based on introducing control design coupling between front- and rear-axle active suspensions. The considered linear quadratic regulator (LQR) cost function includes conflicting criteria related to ride comfort, vehicle handling, and suspension stroke. A covariance analysis related to standard deviations of cost function criteria with respect to stochastic road profile input is carried out for half-car models with two and four degrees of freedom. The presented results show that the control-design coupling can considerably improve the ride comfort in terms of reduced sprung mass pitch or heave acceleration with a relatively small sacrifice of vehicle handling and suspension stroke. The performance improvement is explained by the fact that the rear suspension controller uses state information from the front axle (and vice versa), which may be considered as a kind of preview action.