An adjustable robot arm mechanism with the muscle coordinate system performing contact tasks

The extremities of both humans and animals have a muscle coordinate system. This muscle coordinate system consists of three pairs of antagonistic muscles, one antagonistic pair of bi-articular muscles, and two antagonistic pairs of mono-articular muscles. Motion control, using a muscle coordinate system, has been confirmed using robotics, and verified using a robotic arm equipped with three pairs of antagonistic actuators. In a two-joint link model, equipped with a muscle coordinate system, the moment arms and elastic coefficient of the bi-articular actuators and the mono-articular actuators at the first joint contribute to both the control of the elastic ellipse and the trajectoiy exerted at the endpoint. The present study investigates the use of a two- joint link mechanism, based on the human muscle coordinate system, to complete contact tasks. The mechanical properties of the muscle coordinate system were examined both theoretically and experimentally in terms of robotics, and the results demonstrate that a robotic ann provided with these mechanical properties could resolve a contact task in both the active condition and the passive condition.