基于合作靶标的在轨手眼标定

On-orbit hand-eye calibration using cooperative target

针对空间站机械臂的在轨手眼标定问题,提出了一种利用合作靶标位姿求解手眼关系的方法。机械臂执行2次小幅度运动,让安装在机械臂末端的摄像机在3个不同的位置拍摄合作靶标图像;提取每幅图像中3个特征点的图像像素坐标,结合预标定的摄像机内部参数求解出与其对应的图像物理坐标;接着用P3P算法求取每幅图对应的摄像机外部参数;再根据摄像机外部参数和机械臂的2次运动参量,用矩阵重排的方法求解手眼转换矩阵。采用六自由度转台对此方法进行了验证,实验结果表明手眼标定误差小于0.05 mm,满足机械臂系统精度要求。该方法同时完成了单目位姿测量和手眼标定,操作步骤简单、计算量小、精度高。

Aiming at the on-orbit hand-eye calibration problem of space robot arm,a new method for solving the position and orientation of the wrist-mounted camera with respect to the robot wrist is proposed using cooperative target.The camera mounting position can be found by performing the following procedures.Firstly,the robot arm is moved twice in small step and the wrist-mounted camera is used to take the pictures of the cooperative target in three different positions.Secondly,the pixel coordinates of three feature points on the cooperative target are extracted in each image and then the pre-calibrated intrinsic camera parameters are used to calculate their corresponding physical image coordinates.Thirdly,the P3P algorithm is used to solve the extrinsic camera parameters for each image.Lastly,combining the camera extrinsic parameters with robot arm motion parameters for the two movements,the hand-eye transformation matrix can be easily obtained using matrix algebraic rearrangement.Experiment on a six-DOF turntable was performed to verify the proposed method; experiment results show that this calibration method can achieve a hand-eye calibration error of 0.05 millimeter,which meets the precision requirement of the space robot arm system very well.The proposed method is able to complete position-pose measurement and hand-eye calibration simultaneously.Moreover,the method features simple operation,less calculation task and high precision.