Braided thin McKibben muscles for musculoskeletal robots

The McKibben artificial muscle is considered to be a good actuator for musculoskeletal robots because its compliance and contraction properties are similar to those of animal muscles. However, there are still some limitations to its application to musculoskeletal robots. Although the thin McKibben muscle developed by our research group is an improvement from the conventional one, it has a fatal disadvantage-it cannot be relaxed unlike real muscles. However, the braided McKibben muscle, previously proposed by our research group, can be elongated by applying an external force that can realize muscle relaxation. In this study, we improved its existing structure to provide sufficient durability, enabling its application to musculoskeletal robots, and investigated the muscle with a focus on passive relaxation. The improved braided McKibben muscle increased the driving range of the joint of a musculoskeletal arm model, and the results were verified numerically and experimentally.