Quasi-static feedback linearization for the translational dynamics of a quadrotor helicopter

This paper presents an exact input-output linearization for the translational dynamics of a quadrotor helicopter. The approach utilizes an attitude parametrization based on quaternions and consists of the following two stages. First an input-output linearization from the z position to the thrust is performed, followed by a second input-output linearization from the xy position to the control torques. This separation leads to a so called quasi-static feedback linearization that omits additional controller states. Since the translational dynamics depend only on the orientation of the thrust vector, the required attitude information can be described by only two degrees of freedom. This enables a model of reduced order for the translational dynamics which is decoupled from the yaw dynamics. The suggested feedback linearization was successfully tested in first experimental indoor flights.