Second order sliding mode control for a quad-rotor helicopter with a nonlinear sliding surface

This paper presents a novel second order sliding mode control strategy for a robust tracking controller of a quad-rotor helicopter by utilizing a nonlinear sliding surface. The nonlinear sliding surface enables the closed loop dynamics to have a variable damping ratio, and therefore the transient time to reach the sliding mode can be shorten. The effectiveness of the proposed control strategy is proven experimentally.