Autonomous precision formation flying: a proposed fault tolerant attitude control strategy

Future space missions, such as those involving formation flying of multiple satellites require high operational autonomy mainly with the aim of reducing the operation costs and improving reactivity to sensed data. In particular, stringent performance requirements envisaged precision formation flying cannot be achieved by currently available technologies. One of the main challenges in achieving autonomy is the capability of fault management without extensive involvement of ground station operators. This paper uses a second order nonlinear sliding mode observer to detect actuator faults in the attitude control system of a satellite with four reaction wheels in a tetrahedron configuration. A post-processing of residuals is required to isolate and reconstruct the faults in all four reaction wheels. Furthermore, the control strategy needs to be reconfigured to recover faults. Simulation results show that the proposed strategy can detect, isolate and reconstruct reaction wheel faults in the attitude control system of a satellite.