Control reconfiguration after actuator failures using disturbance decoupling methods

This paper addresses the control of a system after an actuator has failed: A reconfiguration of the control structure is sought which keeps the system operational. The goal is to find a different set of actuators for controlling the plant and to use them in such a way that the plant output is identical to the output of the nominal closed-loop system. It is further required that the nominal controller remains part of the reconfigured control loop. This paper shows that this reconfiguration problem is equivalent to a disturbance decoupling problem which is solved by means of the geometric approach. The resulting solution is a reconfiguration block, which generates suitable inputs for the faulty plant based on the output of the nominal controller. The feasibility of this approach is demonstrated by a physical experiment with a helicopter model.