Observer-Based Sliding Mode Control of a 2-DOF Helicopter System

A sliding mode control (SMC) strategy is presented for a 2 degrees of freedom (DOF) helicopter system, which achieves asymptotic attitude regulation to desired set points as well as trajectory tracking. A rigorous Lyapunov-based analysis is provided to prove convergence to the desired set points. To overcome the practical limitations of velocity measurements, a sliding mode observer is designed to estimate the angular velocities. The convergence of the estimated velocities to the actual velocities is proven via a rigorous Lyapunov-based analysis and illustrated through computer simulations. In addition, computer simulations are presented, to demonstrate the effectiveness of the control law when applied to the complete nonlinear system dynamics. Finally, the control strategy is experimentally tested on the Quanser 2-DOF AERO helicopter. The results of the observer-based SMC strategy are compared to a conventional PID-controller.