Design and Evaluation of a Low-Cost Mount for Attaching a Laser Tracker’s SMR to a Robot Flange

Robot measurements for calibration and modelling are typically performed using a laser tracker. To measure three-dimensional positions, a Spherically-Mounted Retroreflector (SMR) is attached to the robot. Some researchers use adhesive bonds to attach the SMR, but this makes the positioning of the SMR inaccurate, unstable and unrepeatable, which affects the measurement itself and the traceability of the research results. We therefore investigated ways of attaching a SMR to the robot’s flange for accurate and repeatable measurements. At the same time, we observed measurement errors that occur when using a tool to attach a SMR to the flange. The solution that we developed is a 3D printed mount that can be attached to the flange. We evaluated the accuracy of the mount by measuring its eccentricity and the repeatability of placing the SMR in the mount. Our experiments showed that with an eccentricity radius of 0.35 mm and a repeatability inaccuracy of X=0.075 mm, Y=0.328 mm and Z=0.485 mm the mount has a sufficient accuracy to support calibration processes, traceability of research results and to replace adhesive bond.