Abstract: Aiming at the problem that the quadrotor has fined angle of view during the tracking process and is easy to lose the targot，a four-rotor UAV ( Unmanned Aerial Vehicle) tracking control system based on pan /tilt camera is designed for the problem of quadrotor UAV． Firstly，the head camera is used to shoot the ground moving target． By detecting and recognizing the color and shape features of the target，the KCF ( Kernel Correlation Filter) method is used for visual tracking，and the position of the ground moving target in the image coordinate system is obtained and used． The method of cascading PD( Proportion-Differential) control is used to move the perspective of the PTZ ( Pan /Tilt /Zoom ) camera to achieve tracking of the target． Then，by establishing a pinhole model，the relative positional relationship between the drone and the ground target when the PTZ camera has a pitch angle is calculated． Finally，a discrete cascading PID ( Proportion-Integral-Differential) controller is designed to realize the tracking of the quadrotor UAV． The experimental results show that the four-rotor UAV tracking control system designed in this paper can achieve stable tracking of ground moving targets．

Key words: visual tracking, pan /tilt /zoom ( PTZ) camera, pinhole model, relative position solution, tracking control of quadrotor