Fault diagnosis with disturbance rejection performance based on disturbance observer

In this paper, a new fault diagnosis approach presented for a class of non-linear systems with external disturbances. The unknown disturbances are supposed to be rated by an exogenous system, where some classical assumptions on disturbances can be removed. It is shown that it will be difficult to diagnose the fault if disturbances and faults exist simultaneously in the system. To overcome this obstacle, a new composite observer is constructed by combining a fault diagnosis observer with a disturbance observer, with which the fault can be estimated and the disturbances can be rejected at the same time. Finally, simulation is given to show the efficiency of the proposed approach.