Invariant Sets in Saturated and Robust Vehicle Suspension Control

This manuscript introduces a new robust control design of car active suspension systems using ellipsoidal techniques. The impact of road irregularities is regarded as an external disturbance. The suggested controller meets the following objectives: optimal passenger comfort, actuator control force limit satisfaction, effective disturbance rejection, and robustness against changes in passengers’ load. The passenger load variations cause system uncertainty that is modeled as norm-bounded. A new sufficient condition is established based on the invariant ellipsoid method and the linear matrix inequalities optimization to guarantee robust stability and performance for the system. Time-domain model of road roughness based on trigonometric functions is studied. The performance of the proposed controller is tested using a quarter-car model with an active suspension system. Comparative simulation with other techniques, e.g., H_∞ and regional pole placement, is given. Actuator dynamics and system nonlinearities are modeled and included in the design at the end.