In this paper, we propose a novel linear matrix inequality-based nonlinear adaptive robust control algorithm to design the attitude and position controllers for an X-conflguration quadrotor helicopter. The inner-loop of the autopilot controls the attitude and altitude of the quadrotor, and the outer-loop controls its position in the earth-fixed coordinate frame. By assuming knowledge of the bounds of the quadrotor's uncertain parameters (e.g. mass and moments of inertia) and predetermined bounds on the external and unstructured disturbances (e.g. wind gusts and unmodeled dynamics), we attain a guaranteed transient and steady state tracking performance. We demonstrate the performance of the controllers via two illustrative examples. In the first example mission, the quadrotor follows an altitude reference trajectory in the presence of wind gusts and delivers a package of uncertain mass mid-flight. The second example presents an autonomous waypoint flight in the presence of wind disturbances. The results of our simulations indicate that our controller design is useful for a variety of quadrotor applications, including precise trajectory tracking, autonomous waypoint navigation in the presence of disturbances, and package delivery without loss of performance.
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