Fault-tolerant servo systems using integrators with variable limits

No effective controller design methods for achieving the tolerance against sensor and/or actuator failures have not yet been proposed for servo systems because it is difficult to deal with divergent signals such as ramp signals generated by integrators for servo performance. We obtained the key values for the limiting function implemented in limited integrators to behave effectively as a measure against divergent signals. In this paper, we propose the limiting function with variable limits for better fault-tolerance, i.e., for suppressing the fluctuation in transient responses in a normal loop immediately after failures. The obtained result succeeds in establishing the potential applicability of limited integrators to fault-tolerant servo systems.