Least square based sliding mode control for a quad-rotor helicopter

In this paper, we design a least square based sliding mode control to solve the over determined problem in translation motion of a quad-rotor helicopter while in rotational motion we employ a regular sliding mode control. A saturation function is designed around a boundary layer to reduce the chattering phenomenon that occurs in a sliding mode control. The dynamics of the quad-rotor helicopter is derived by the Newton-Euler formulation for a rigid body. A constant plus proportional reaching law is utilized to increase reaching rate of the sliding mode controller. The stability of the proposed algorithm is evaluated on the basis of Lyapunov stability theory. Experimental results under wind disturbance are presented to show the robustness and effectiveness of the proposed control algorithm.