Retrofit reconfigurable fault tolerant control for mechanical systems

This paper investigates a difficult problem of retrofit reconfigurable control design that retains a baseline/nominal controller and, at the same time, accommodates actuator faults and uncertain dynamics so that the overall system is stable and the control objective is met. A theoretical retrofit control architecture is developed for a class of mechanical systems. This is accomplished using minimum prior information regarding the baseline/nominal controller. A reconstruction mechanism is firstly designed to precisely estimate system uncertainties and actuator fault. Using such reconstructed value, a retrofit control signal is generated as a compensation effort, and added to the nominal controller to compensate for uncertainties and faults. It is shown that the closed-loop system resulted from the proposed retrofit controller has the same properties of the nominal closed-loop system, which consists of the certain system dynamics and the dynamics of the nominal controller. The performance of this retrofit reconfigurable control design is verified with simulation results.