Performance evaluation of self-healable torque transmission mechanism using phase change of low-melting-point-metal and application to robot joints

Self-healing properties of robots can aid in achieving a high level of motion continuity despite the absence of manual maintenance. Therefore, various studies have been conducted on self-healing materials and mechanisms to incorporate self-healing properties in robots. However, the self-healing performance of a motor rotation system, which is the power source of existing robots, has not been realized owing to the unsuitability of the self-healing method and material strength. Therefore, we propose a self-healable torque transmission mechanism using a low-melting-point metal that can be applied to transmission elements because of its strength and rigidity. Additionally, heating for self-healing can be performed without contact through induction heating. Hence, a self-healable torque transmission mechanism with a simple structure can be applied to a motor drive system where continuous rotation occurs. We evaluated the performance of the proposed mechanism experimentally by measuring the transmittable torque and the amount of energy absorbed when the torque transmission is interrupted. The results verify that the healing performance and energy absorption of the proposed mechanism remain stable, and the mechanism can heal without any performance degradation. Furthermore, the proposed mechanism was implemented in a robot to demonstrate its practical applications. It was found that this mechanism enables the robot to re-operate by self-repair even if it receives a load that can destroy the joint due to overload, and the robot’s ability to continue motion could thus be improved.