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Cascaded Control Design for a Stabilized Pan-Tilt Camera Platform on a Quadrotor UAV

This paper presents a new cascaded control design for a pan-tilt camera platform. The camera platform can be mounted on a quadrotor unmanned aerial vehicle (UAV) to achieve a fixed target or moving target detection and tracking. The airborne pan-tilt camera platform can effectively isolate a disturbing rotational motion of the carrier, ensuring the stabilization of the optical axis of the camera to get a clear video image. At the same time, the camera platform ensures that the target is always on the optical axis of the camera, so as to achieve the detection and tracking of targets. The control system design adopts cascaded control method based on the identified dynamics of the pan-tilt camera platform. The inner loop of the proposed controller which controls the angular velocity employs proportional-derivative (PD) control method to ensure the stability of the platform. The outer loop which controls the orientation of the optical axis employs integral separated proportional-integral-derivative (PID) control method to achieve the target tracking. The superiority performance of the proposed controller is verified by laboratory experiments.