Applying adaptive fuzzy sliding mode control to an underactuated system

In this study, an adaptive fuzzy sliding-mode control (AFSMC) approach is adopted to control the position and attitude of a quadrotor helicopter. Control of this vehicle is difficult because of the unstable nonlinear underactuated dynamic behavior. The proposed control system combines great advantages of adaptive sliding mode control (ASMC) and fuzzy control. The controller has been applied to Z position and its attitude. Besides, to control of X and Y position, their error has been considered in the desired inputs of θ and φ. An on-line adaptive tuning algorithm based on Lyapunov function and Barbalat lemma is designed, thus the stability of the system can be guaranteed. The chattering phenomenon in the sliding mode control is reduced and the steady error is also alleviated. Numerical results indicate that the presented adaptive design of fuzzy sliding mode controller performs very well in the presence of high sensor noise and external disturbances such as ground effects.