Improving hovering performance of tethered unmanned helicopters with nonlinear control strategies

Hovering capabilities of unmanned helicopters can be seriously affected by wind effects. One possible solution for improving hovering performance under such circumstances is the use of a tethered setup that takes advantage of the tension exerted on the cable that links the helicopter to the ground. This paper presents a more elaborated strategy for helicopter control in this augmented setup that extends previous work on the subject by the authors. Particularly, a combination of classical PID control laws together with model inversion blocks constitutes the base of the new controller. Additionally, feed-forward action for counteracting rotational couplings is also accounted for. The resulting nonlinear control structure considers the complex and nonlinear nature of the tethered system in a better way. Several demonstrating simulations under artificially generated wind influences are presented to endorse the validity of the new proposed controller.