Fault-tolerant servo systems against actuator failures using limited integrators

An effective controller design for achieving the tolerance against actuator failures has not yet been proposed for servo systems because it is difficult to deal with divergent signals generated by integrators for servo performance. In this study, we obtain for the first time key values for the limiting function in limited integrators to behave effectively as a measure against divergent signals. Then, the limiting function and a controller can be designed in a unified framework of simultaneous optimization with consideration given to the servo performance in the normal case and in faulty cases. The obtained result succeeds in establishing the potential applicability of limited integrators to fault-tolerant servo systems.