Planar trajectory tracking controller for a small-sized helicopter considering servos and delay constraints

The problem of planar navigation of an autonomous helicopter in hover/low-speed flight condition with servo and delay constraints is considered. For controller design and testing purposes, we analytically derive a complete nonlinear model of a small size helicopter with no stabilizing bar (flybar) and the helicopter linear model. In order to stabilize the helicopter, the linear quadratic regulator with integral action (LQI) is used. We show that, the maximum amount of delay in the system before it goes unstable (delay margin) is inversely related to the strength of the feedback gain and therefore helicopter performance in following trajectories. To improve the performance, we apply a feedback-feedforward control structure and show that the system is robust for the entire range of delays up to delay margin. The comparison of simulation results shows considerable improvements in helicopter performance for following highly maneuvering and fast trajectories for the hybrid feedback-feedforward control structure over the LQI method.