How to do the gripper calibration to add gripper into URDF

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Hi

i have a 2 finger gripper and a 6 DOF aubo i5 robot. i want to add the gripper into robot's urdf. But i dont know how to find the position of the gripper end point with respect to last link of the robot. Is there any standard procedure to find the position and orientation of the gripper like how we calibrate camera using Visp package. Ultimately i want to find the below values for my gripper to add into the urdf.

xyz=" " and rpy=" "