What is the key advantage of using a laser tracker for robot calibration compared to traditional methods?

The key advantage of using a laser tracker for robot calibration compared to traditional methods is its ability to accurately measure the robot's position and orientation in 3D space over a large working volume. Traditional methods, such as using dial indicators, gauge blocks, or coordinate measuring machines (CMMs), often have limitations in terms of measurement range and accuracy, especially when dealing with large robots or complex robot cells. A laser tracker uses a laser beam to precisely track the position of a reflector (typically a spherically mounted retroreflector, or SMR) that is moved to various points within the robot's workspace. By measuring the distances and angles to the reflector, the laser tracker can determine the 3D coordinates of these points with very high accuracy, typically on the order of tens of micrometers. This allows for a comprehensive assessment of the robot's volumetric accuracy, identifying errors in joint parameters, link lengths, and other kinematic parameters. For example, if a robot is supposed to move to a specific point in space, the laser tracker can precisely measure the actual position of the robot's end-effector and compare it to the commanded position. The data from the laser tracker can then be used to update the robot's control system, improving its accuracy and repeatability. Compared to traditional methods that may only measure a few specific points or require physical contact with the robot, a laser tracker provides a more complete and accurate picture of the robot's performance across its entire working volume.