Fault diagnosis for non-linear single output systems based on adaptive high-gain observer

This study deals with the fault diagnosis (FD) problem for affine non-linear systems with single output. Under a well-defined persistent excitation condition including m time delays, m parallel coupled adaptive high-gain FD observers have been designed in some existing literature based on Lyapunov function approach. By employing Lyapunov¿¿Krasovskiii functional approach, this study presents an alternative algorithm to design a simplified FD observer with global exponential convergence, which drastically reduces the complexity of the existing FD systems. A simulation example about a single-link robot arm is provided to illustrate the proposed theoretical results.