Real-time nonlinear embedded control for an autonomous quadrotor helicopter

Control system design of aerospace vehicles with actuator saturation is an important practical design problem that many previous approaches to nonlinear autopilot design did not consider. In particular, small unmanned aerial vehicle rotorcraft actuators often have physical limitations such as a restricted onboard power supply. Disregard of actuator saturation can affect the final performance, but the reduction in performance can be mitigated if actuator saturation is included in the controller design. In this paper, we propose a nested-saturation-based nonlinear controller for the stabilization of a rotary-wing aircraft. This control strategy allows the incorporation of actuator magnitude saturation and has satisfactory dynamic performance. The nested-saturation technique enables the controller to ensure the global asymptotic stability of a quadrotor helicopter while improving the performance of the closed-loop system. By using Lyapunov analysis, the convergence property is established for the complete nonlinear model of the quadrotor rotorcraft. Simulation results show the performance of the proposed control strategy. 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 autonomously perform the tasks of taking off, hovering, and landing.