Development of Deep Biomimetic Quadruped Robot with Bow-string Structure in Cursorial Mammals

The flexible trunk of quadrupedal mammals plays an essential role in achieving agile movements. The mammalian trunk, segmented into the cervical, thoracic, lumbar, sacral, and caudal vertebrae, allows sagittal bending for high-speed running, axial rotation for balance, and lateral bending for turning. While the trunk achieves flexibility, it must also provide sufficient stiffness for weight-bearing. To extract design principles for a flexible trunk in agile robots, this study develops a "deep'' biomimetic quadruped robot that mimics both the macroscopic weight-bearing structure, i.e., the bow-string structure, and the deep-layered structure of the abdominal wall. The developed robot demonstrated that the proposed trunk design can implement flexibility in the roll, pitch, and yaw axes, as well as the ability to bear the body weight during walking.