Because a complete mathematical model of a quadrotor is complicated, the controller design is
usually based on a simplified model. In this paper, we analyze the limitation of such simplification, and consider
nonlinear trajectory tracking control based on its original model. A tracking error control system consisting
of two independent subsystems is established to track the expected trajectory. The attitude subsystem is
described using the quaternion of rigid body’s rotation as the system state. A backstepping based approach is
proposed to stabilize the subsystems exponentially. Based on the global stability criterion of cascade systems
and analysis of the properties of coupled parts, globally exponential stability of the system is proved. Simulation
results show that the proposed method enables the quadrotor to track a trajectory.