  This paper proposes several nonlinear control strategies for trajectory
tracking of a quadcopter system based on the property of differential flatness.
Its originality is twofold. Firstly, it provides a flat output for the
quadcopter dynamics capable of creating full flat parametrization of the states
and inputs. Moreover, B-splines characterizations of the flat output and their
properties allow for optimal trajectory generation subject to way-point
constraints. Secondly, several control strategies based on computed torque
control and feedback linearization are presented and compared. The advantages
of flatness within each control strategy are analyzed and detailed through
extensive simulation results.
