A CRB-Embedded Joint Torque Sensor with Low Crosstalk Error

Collaborative robots need to estimate external forces applied to the end-effector or body to enable precise direct teaching and collision detection. For this purpose, many robots are equipped with Joint Torque Sensors (JTS), which estimate external forces at the robot's end by measuring the torque at each joint. Robot joints are subjected to complex loads, including moment, axial, and radial loads, in addition to torque loads due to the robot's movements and posture. Therefore, accurate torque measurement is crucial even under these conditions. Existing JTS designs use Cross-Roller Bearings (CRB) to support complex loads and minimize crosstalk errors. However, they are affected by vibrations, torque ripple, and assembly stress from the reducer's operation, and are limited to specific types of reducers. In this study, we developed a JTS with an embedded CRB to minimize crosstalk errors and withstand complex loads. The developed JTS can be used as an independent sensor, making it widely applicable to robots using various types of reducers.