ROBUST FDI APPLIED TO THRUSTER FAULTS OF A SATELLITE SYSTEM

This paper addresses the problem of the detection and isolation of the faults affecting the thrusters of a satellite system, which is characterised by a nonlinear model, in the presence of measurement errors, uncertainty and disturbance. In particular, this work proposes a robust estimation approach to the problem of the design of residual generators in order to realise complete diagnosis schemes when realistic faults are present on the simulated system. This approach leads to dynamic observers that can achieve both good disturbance de-coupling and robustness properties with respect to linearisation error, uncertainty and measurement noise. The description of the satellite structure is provided in order to highlight the main sources of uncertainty and disturbance. The faulty behaviour of the satellite Mars Express (MEX) nonlinear model and a comparison with the existing fault diagnosis scheme implemented on-board are reported. Finally, suitable performances criteria are introduced together with the Monte Carlo analysis for assessing the robustness and performance evaluation of the suggested FDI design methodology.