Output-feedback sliding-mode control for systems subjected to actuator and internal dynamics failures

This study presents an output-feedback control algorithm based on unit vector sliding mode for a class of multivariable systems. The control objective is to force each output signal to track a desired reference trajectory, while retaining good performance despite parameter uncertainties, unmatched disturbances and actuators faults that eventually may occur in the plant. Owing to the new approach proposed to tackle this problem, which involves a linear matrix inequality to be satisfied by the control distribution matrix, no upper bound on this matrix is required. Moreover, a remarkable result is that the proposed fault-tolerant controller can even handle variations in the order of the system dynamics. The analysis shows that the resulting closed-loop system is globally exponentially stable. A simulation example with a chain of trailers driven by redundant actuators illustrates the design and effectiveness of the proposed strategy.