Realization of Advanced Contact Motion with Low Moment of Inertia Using In-Link Actuators

Robots should be able to interact more actively with the general public to operate close to them. However, human communication is sometimes performed at high speed and involves collisions, which poses a safety problem when humans and robots interact. To perform these actions safely, the energy involved in a collision should be reduced, and it is useful to reduce the inertia of the robot. Additionally, it is crucial that the back-drivability is sufficiently large to follow external forces. We used an in-link actuator to reduce the inertia of a robot with direct-drive joints. In-link actuators, with a drive mechanism incorporated into the links, enable the creation of a low-inertia robot with joints that can be driven quickly even with a small torque. Experiments were conducted to confirm the effectiveness of the in-link actuator in contact motion. By measuring the force during a collision and moving while holding down a fragile object, we demonstrate that the use of in-link actuators enables a higher level of interaction without damaging the outside object compared to the use of motors.