Approach of “planar muscle” suitable for musculoskeletal humanoids, especially for their body trunk with spine having multiple vertebral

For making a robot that can help people safely, a musculoskeletal humanoid is an effective approach because of the ease of high degrees of freedom. However, many musculoskeletal humanoids have not yet been equipped with really humanlike bones and muscles. For making musculoskeletal humanoids with really humanlike bones and muscles, we thought that a "planar muscle" was a key. In wire-driven systems which many musculoskeletal humanoids adopted, one motor winds only one wire. However, this "linear muscle" needs one motor per wire and complex control systems as for one humanoid. Therefore, we developed "planar muscle" that controls several wires simultaneously by using two moving-pulleys bars and one motor. The "planar muscle" fits for musculoskeletal humanoids, especially for their body trunk with a spine having multiple vertebrae that need a lot of motors and complex control systems in the case of using linear muscles. Thus, we focus on developing a body trunk of a musculoskeletal humanoid that has multiple vertebrae and uses "planar muscles" for the body trunk. In this paper, we will show the concept of "planar muscle" and evaluate its motions with body-trunk model having multiple vertebrae that we have newly developed.