Robust fault tolerant controller in parabolic distributed parameter systems with actuator faults

The objective of this note is to provide an actuator switching scheme in a distributed parameter system whose actuators exhibit linear dynamics for only a short time period before reverting to nonlinear actuator map. It is assumed that multiple actuating devices are available for utilization, but only a smaller subset may be used in a given time interval due to this temporary linear actuator map. In order to retain this linear actuator map and hence avoid inclusion of additional nonlinear dynamics into the model, the monitoring scheme only selects an actuator from the category of healthy actuators which exhibits linear dynamics for the duration of a given time interval. Once a given actuator is used for the duration at which it exhibits linear dynamics, it is placed in the set of recuperating actuators and considered as a viable actuator only after it has recuperated. In addition to the policy for actuator switching, the monitoring scheme also provides the control signal to be used in the actuating device in use. Using a global feedback controller that is a stabilizing controller regardless of the actuating device used, the monitoring and switching policy simplifies to that of switching only the actuating devices at different time intervals. The efficacy of the proposed scheme is applied to a thermal process with multiple actuators and the success of the actuator switching over the case of a permanently used nonlinear actuator is presented.