Adaptive fault tolerant control for reconfigurable systems

Reconfigurable systems are the safe dynamical systems wherein the health of the control input and/or sensor output variables are continuously monitored and then they are reconfigured, if necessary, in an event of an unexpected fault detected online. This idea is applied, in particular, at the reconfigurable system where the number of control variables is more than the state variables considered to define its motion. In this paper, an adaptive pole placing controller is developed for use in such reconfigurable systems. Adaptive pole placing controller, in theory, is adaptive to take a fault size and retain the closed loop poles it assigns at fixed locations in the open left half plane of the complex plane. As a result, when the controller is not adaptive, it means that the pole perturbations could lead to catastrophes. However, to design adaptive pole placing controller for a reconfigurable system, fault size is required. Hence, the primary objective of the paper is to present a simple procedure that determines the fault size for tuning in the adaptive pole placing controller. Both direct and full-order Luenberger observer based state feedback adaptive pole placing controllers are presented. In situations where the adaptive pole placing controller is not possible, the fault size for which the reconfigurable system with a non-adaptive pole placing controller would transit from a stable to unstable system (referred as fault tolerant margin with respect to the non-adaptive pole placing controller) is also presented. Some of these features of this paper are illustrated by using the reconfigurable aircraft model available in the literature.