Strategies for control, fault detection and isolation via sliding mode techniques for a 3-DOF helicopter

In this paper an underactuated 3-DOF laboratory helicopter is considered as test bed for fault detection and isolation. First, a sliding mode control strategy is suitably designed. The performance and robustness issues of the closed-loop system are illustrated in both the cases of the state-feedback control and the dynamic output-feedback control, when a nonlinear observer is exploited. Then, the fault detection and isolation problem for the 3-DOF helicopter is considered. The developed residual-based fault detection and isolation relies on the measurable output, some of its derivatives, which are provided exactly by a second-order sliding-mode differentiator, and the observer's state. The proposed methodology is able to detect and to isolate, under some mild conditions, some possible actuators faults. Simulation results illustrate the feasibility of the proposed approach.