The design and control of the flexible spine of a fully tendon-driven humanoid "Kenta"

We are trying to realize a humanoid which has flexibility. If humanoids have a flexible structure, safety and posture variety can be achieved. We focus on the role of the human spine and muscle-driven system. By having a flexible spine, a humanoid will have safety and many degrees of freedom to realize a variety of postures. By driving joints by tension-controllable tendons, flexibility of the joints can be controlled. We developed a whole-body tendon-driven flexible-spine humanoid named "Kenta". This paper describes the design and control of Kenta, focusing on the design of the spine. The spine consists of ten joints, vertebrae and rubber disks, ribs, and forty muscles equipped with tension sensors. We also propose control methods of the spine. One uses a geometric virtual robot model and another is based on direct teaching. Using these methods, some whole-body motions are presented.