Bi-articular muscle as a principle keyword for biomimetic motor link system

Unique functional properties of the bi-articular muscles were examined and discussed in terms of EMG kinesiology with human subjects and robotics utilizing a mechanical two-joint link model provided with bi-articular actuators as well as monoarticular actuators. It was revealed that one antagonistic pair of the bi-articular muscles and two antagonistic pairs of the mono-articular muscles demonstrated a perfectly coordinating activity pattern and contributed to output force direction control at the endpoint of the extremities. The coordinating activities of three pairs of antagonistic muscles were able to reproduce by a single command signal informing force direction via a proposed simple spinal level neural network. Thus, the existence of the bi-articular muscles in animals might mechanically support animal like unique motor control properties with very simple control mechanisms.