SII 2022: A Highly Backdrivable Robotic Arm using Low Friction and High Accuracy Geared Motors

We have developed a robotic arm using low friction and high accuracy geared motors. Reducers installed in conventional industrial robots are designed to have a low backlash of approximately 3 arcmin (0.05 degree) or less to suppress lost motion. However, the joints of the robot are stiff, and thus it is difficult to backdrive by a small external force. This problem limits applications of existing industrial robots, particularly for tasks that require mechanical contact between the robot and the external environment. Although a low friction geared motor constitutes a possible solution, backlash leads to an increase in lost motion. Therefore, this study presents a combination of electric motor and cycloidal drive with a 20:1 reduction ratio, 1 arcmin of backlash, and low backdrive torque (low friction) of 1 Nm. Experiments verify position and orientation repeatability, as well as force accuracy, estimated from the motor-current based joint torque.

*This paper is based on results obtained from a project commissioned by the New Energy and Industrial Technology Development Organization (NEDO).

This study has been reported in the IEEE/SICE International Symposium on System Integration (SII 2022), January 2022.
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