Fault-tolerant control with state and disturbance observers for vehicle active suspension systems

Abstract

This paper deals with the design of a fault-tolerant control scheme of active suspension systems for vehicle ride comfort. Unknown actuator failures from a variety of reasons cause performance deterioration of the active suspension controller. The proposed fault-tolerant control algorithm consists of two parts: a compensation for actuator failure and a fault mode selector. The main function of the fault compensation strategy is to estimate and compensate for the loss of effectiveness of the actuators. A suspension state observer and a disturbance observer operate simultaneously to determine the feedback control input. The controller and observer have been developed based on a reduced full-car dynamic model that contains only the vehicle body dynamics. The main advantage of the proposed observer is that an easily accessible and inexpensive measurement is only required and the effect of unknown road disturbance on the estimation error is completely removed. To cope with complete failure cases, the fault mode selector is also designed to redistribute the control input to the remaining healthy actuators. Tracking of the loss of effectiveness of the actuators is used for the fault model identification. The performance of the proposed approach has been evaluated via simulation studies. It is shown that the vehicle ride comfort in the presence of actuator faults can be improved by the proposed combined strategy of the fault compensation method and the fault mode selector.