小型无人机地面目标跟踪系统机载云台自适应跟踪控制

Adaptive control for the on-board pan-tilt camera in an UAV ground-target-tracking system

本文针对小型无人机地面目标跟踪系统，提出了一种机载云台自适应跟踪控制算法．该算法在摄像机外参数未知的情况下，利用图像信息和机载传感器得到的无人机状态进行反馈，最终实现了对云台摄像机姿态的控制，使得无人机在跟踪目标飞行过程中，地面目标可以始终保持在摄像机的图像中心．为此，论文首先通过分析无人机、目标和摄像机三者的相对位姿关系，建立了目标点在图像平面的运动学模型．在此基础上，基于李雅普诺夫稳定性理论设计了自适应控制算法．理论分析与仿真结果表明本文所设计的摄像机姿态控制器在摄像机外参数未知的情况下，可以使被跟踪目标始终保持在图像中心．

For a ground-target-tracking system in an unmanned helicopter, an adaptive on-board pan-tilt motion controller is proposed to adjust the camera＇s pose to maintain the image of the tracked ground-moving target being at the center of the viewing frame, when the extrinsic parameters of the camera are unknown. First, the dynamic characteristics of the image signal are analyzed and a kinematics model is developed for the target in the image space by the geometrical relations among the helicopter, the target and the camera. Then, an adaptive pan-tilt motion control law is proposed based on the model to keep the target being at the center of the viewing frame. The performance of the controller is demonstrated by both the theoretical stability analysis and simulation results, showing that the proposed adaptive controller can maintain the target image at the center of the viewing frame in the presence of unknown camera extrinsic parameters.