Disturbance Observer-based Trajectory Tracking Control for Small-scale Unmanned Helicopters

A non-singular terminal sliding mode controller is proposed for trajectory tracking of small-scale unmanned helicopters. The helicopter model is firstly decomposed into a nominal one with unmodelled dynamics. Based on the decomposed model, the controller is designed with the hierarchical inner-outer loop with Two-Timescale structure. The non-singular terminal sliding mode approach is employed to design the outer position loop controller and the inner attitude loop controller. In addition, in order to improve the tracking performance, observers are employed to compensate the disturbance. The stability of the closed-loop system is rigorously proved by Lyapunov techniques. The time taken to reach the equilibrium point from any initial state is guaranteed to be finite time. Simulation results are presented to validate the analysis.