Calibration of a Robot's Tool Center Point Using a Laser Displacement Sensor

The conventional tool center point calibration (TCP) method requires the operator to set the actual position of the tool center point by eye. To address this lengthy workflow and low accuracy while improving accuracy and efficiency for time-saving and non-contact calibration, this paper proposes an enhanced automatic TCP calibration method based on a laser displacement sensor and implemented on a cooperative robot with six degrees of freedom. During the calibration process, the robot arm will move a given distance along the X and Y axes and collect the information when the tool passes through the laser during the process to calculate the deflection of the tool, and then continue to move a given distance along the X and Y axes for the second height calibration. After the deflection angle is calculated and calibrated by triangulation, the deflection calibration is completed and the third X and Y axis displacement is performed to find out the exact position of the tool on the X and Y axes. Finally, the tool is moved to a position higher than the laser, and the laser is triggered by moving downward to obtain information to complete the whole experimental process and get the calibrated tool center position. The whole calibration method is firstly verified in the virtual simulation environment and then implemented on the actual cooperative robot. The results of the proposed TCP calibration method can achieve a positioning accuracy of about 0.07 mm, a positioning accuracy of about 0.18 degrees, a positioning repeatability of $\boldsymbol{\pm 0.083}$ mm, and a positioning repeatability of less than $\boldsymbol{\pm 0.17}$ degrees. This result meets the requirements of TCP calibration, but also achieves the purpose of simple, economical and time-saving, and it takes only 60 seconds to complete the whole calibration process.