On-orbit hand-eye calibration using cooperative target

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.