Design and implementation of a nonlinear flight control law for the yaw channel of a UAV helicopter

We present in this paper a flight control system design for the yaw channel of a UAV helicopter using a newly developed composite nonlinear feedback (CNF) control technique. From the actual flight tests on our UAV helicopter, it has been found that the commonly used yaw dynamical model for the UAV helicopter proposed in the literatures is very rough and inaccurate. This motivates us to first obtain a comprehensive model for the yaw channel of our UAV helicopter. The CNF control method is then utilized to design an efficient control law, which gives excellent overall performance. In particular, our design has achieved a level 1 performance according to the standards set for military rotorcraft. The results are verified through actual flight tests.