Nonlinear control for systems with bounded inputs: Real-time embedded control applied to UAVs

In this paper, we propose a nonlinear controller for the stabilization of a rotary-wing aircraft class. The control strategy is based on nested saturation technique which results in uncoupled and explicitly-given inputs. The introduction of positive gains in the control law has permitted to take into account the coupling terms, and to improve the dynamical performance of the closed-loop system especially the convergence speed. The controller performances have been confirmed in simulations when we have compared this approach with other existing controllers. We also present the testbed and the implementation of the control law on a quadrirotor aircraft. Using embedded sensors and onboard control, we performed a real-time autonomous flight. Indeed, experimental results have shown that the proposed control strategy is able to perform autonomously the tasks of taking-off, hovering and landing.