Nonlinear Robust Attitude Tracking Control of 3-DOF Helicopter Based on Output Feedback

Abstract

Three-channel attitude tracking problem is studied for an underactuated three degree of freedom (3-DOF) helicopter with only angular position measurements in this paper. To deal with the underactuated characteristics of the helicopter, an inner-outer loop structure is adopted to achieve attitude tracking of three coupling channels, i.e., the elevation, travel and pitch channels, only using two control inputs. Then, a nonlinear robust controller is proposed for each channel of the helicopter to implement accurate attitude tracking via output feedback. An auxiliary system with second order and filtered error signals are also considered in the controller. Moreover, to mitigate the effects of uncertainties and disturbances involved in the system, an uncertainties and disturbances estimator (UDE) is incorporated into controller. Simulation results are shown to illustrate feasibility of presented controller.