Fault diagnosis and fault tolerant control strategies for aerospace systems

Abstract

This work presents two active fault tolerant control systems for aerospace applications. The former case study regards an aircraft longitudinal autopilot and the latter one a satellite attitude control system, both in case of faults affecting the actuators. The main features of the presented active fault tolerant control schemes are the fault detection and diagnosis module and its design technique, i.e. the nonlinear geometric approach. Such approach allows, using adaptive filters in the fault detection and diagnosis module, fault detection, isolation and estimation. The fault estimates, obtained by different methods including recursive least squares and neural network, are exploited by a controller reconfiguration mechanism. In particular, by means of the nonlinear geometric approach, relying on nonlinear differential algebra, it is possible to obtain fault estimates decoupled from wind components in case of aircraft and aerodynamic disturbances in case of spacecraft, thus giving to the overall control system very good robustness properties and performances. The effectiveness of the designed solutions is shown by means of high fidelity simulators, in different flight conditions and in the presence of faults on actuators, turbulence, measurement noise, and modelling errors.