Robust Nonlinear Tracking Control of a 2-DOF Helicopter System

A robust nonlinear output feedback control method is presented, which achieves two degrees of freedom (2-DOF) attitude tracking of a helicopter system test bed. The control law is designed to compensate for uncertainty in the helicopter system dynamic model, including input-multiplicative parametric uncertainty. To reduce the computational requirement in the closed-loop system, constant feedforward estimates of the input-multiplicative uncertainty are utilized in lieu of adaptive parameter estimates. Eschewing the high-gain feedback requirement that is characteristic of standard sliding mode observer methods, the proposed control method utilizes a bank of dynamic filters, which operates as a velocity estimator in the closed-loop system. Computer simulation and experimental results are provided to demonstrate the performance of the attitude tracking control method using the Quanser 2-DOF AERO helicopter.