A Guidance-Based Robust Controller for Unmanned Helicopter on Three-Dimensional Path Following

A three-dimensional robust path following controller is proposed for an unmanned helicopter with uncertain external disturbance, which is implemented by using dual-loop structure, including an outer-loop for three-dimensional nonlinear path following and an inner-loop for the attitude control. The outer-loop controls the attitude angles and lift to track the expected path and velocity based on the line-of-sight guidance law derived in the flight-path coordination, and the inner-loop was designed based on a backstepping controller in the inertial coordination. The external disturbance were also compensated by using sliding mode disturbance observer based on super-twisting in the inner-loop and the torques were controlled to track the desired attitude. To provide a number of key parameters for path following, the calculation methods are presented. Finally a simulation was carried out to demonstrate the feasibility and performance of the proposed controller.