Fault-tolerant servo systems against sensor failures using limited integrators

No effective controller design for achieving the tolerance against sensor failures has been proposed for servo systems until now because it is difficult to deal with ramp signals generated by integrators in the servo performance. In this paper, we obtain a key for the limiting function in limited integrators to behave effectively as the measure against ramp signals for the first time. 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.