Controlled bi-articular robot arm with planetary gear

In conventional robot arms, one motor is placed in one joint. The other hand, the human upper extremities with bi-articular muscles bind on shoulder and elbow. However, we have introduced the robotic arm with planetary gear imitated bi-articular muscles. The two-link arm with three-actuator has a redundant mechanism. This paper reports on 2 methods for sharing of arm tip force. One is method to minimize 2-norm. The other is equipotential method that has motor gain to decide much the same direction of displacement and force. The 2-norm method shows smaller torque than the other one. The trajectory of the arm tip is plotted close to our target. As a result, the 2-norm method in trajectory control and the motor gain method in compliance control are integrated to produce much advantageous control.