Fault Tolerant Control in a semi-active suspension

Abstract

A Fault Tolerant Control System (FTCS) in a Quarter of Vehicle (QoV) model is proposed. The control law is time-varying using a Linear Parameter-Varying (LPV) based controller, which includes two scheduling parameters. One parameter for monitoring the nonlinear behavior of the damper, and another for fault accommodation using a reference model obtained by a state observer of the normal operating regime. The QoV model represents a semi-active suspension, including an experimental magneto-rheological damper model. The FTCS is analyzed when the velocity sensor fails abruptly and the QoV model is susceptible to disturbances in the road profile. Simulation results show the effectiveness of the FTCS in terms of vehicle comfort, suspension deflection and road holding in comparison with a conventional LPV based control system. In the FTCS, the comfort index based on the power spectral density is within the desirable bound (1.8) in all range of frequencies, once the sensor fault has occurred; while, the conventional control system deteriorates the comfort 54 %, specially at low frequencies (0-4 Hz). Additionally, the FTCS improves the road holding and suspension deflection indexes, 33% and 39% respectively, when the fault accommodation is considered. © 2012 IFAC.