Tip force depend on the motor distribution with bi-article arm using planetary gear

In conventional robot arms, one motor is placed in one joint. The human upper extremities can be simplified into three antagonistic pairs of muscles, those which are a pair of shoulder mono-articular muscles, a pair of elbow mono-articular and a pair of elbow/shoulder bi-articular muscles. In the present study, it is assumed that the bi-articular muscles have a profound effect on not only the position control but power output and rigidity of the arm tip. This study reports that the system is able to imitate the function of bi-article muscles in human uppers by using rotary motors and planetary gears.