Accurate diagnosis on process fault parameters of nonlinear actuator based on adaptive observer and extended state observer

As an important component of a dynamics system,the actuator is generally nonlinear and its output is immeasurable.It is a challenging problem for diagnosing and estimating process fault parameters of nonlinear actuator.Aimed at this problem,a joint observer method is proposed to observe control system and actuator.A novel nonlinear adaptive observer(NAO) is first proposed to estimate the actuator output of the dynamics system with nonlinear actuator and diagnosis fault.The output estimate and control input is then feed to extended state observer(ESO) to estimate process fault parameters.Finally,the proposed FD scheme is applied to a high-fidelity Reaction Wheel(RW) in Satellite Attitude Control System(SACS),and a kind of partial Loss Of Effect(LOE) fault named as augmentation of friction torque is considered in our case study.The results of the case study demonstrate the effectiveness and superiority of our FD scheme.