CubiXMusashi: Fusion of Wire-Driven CubiX

and Musculoskeletal Humanoid Musashi

toward Unlimited Performance

Humanoids 2024

Humanoids exhibit a wide variety in terms of joint configuration, actuators, and degrees of freedom, resulting in different achievable movements and tasks for each type. Particularly, musculoskeletal humanoids are developed to closely emulate human body structure and movement functions, consisting of a skeletal framework driven by numerous muscle actuators. The redundant arrangement of muscles relative to the skeletal degrees of freedom has been used to represent the flexible and complex body movements observed in humans. However, due to this flexible body and high degrees of freedom, modeling, simulation, and control become extremely challenging, limiting the feasible movements and tasks. In this study, we integrate the musculoskeletal humanoid Musashi with the wire-driven robot CubiX, capable of connecting to the environment, to form CubiXMusashi. This combination addresses the shortcomings of traditional musculoskeletal humanoids and enables movements beyond the capabilities of other humanoids. CubiXMusashi connects to the environment with wires and drives by winding them, successfully achieving movements such as pull-up, rising from a lying pose, and mid-air kicking, which are difficult for Musashi alone. This concept demonstrates that various humanoids, not limited to musculoskeletal humanoids, can mitigate their physical constraints and acquire new abilities by connecting to the environment and driving through wires.

Overall Structure of CubiXMusashi

CubiXMusashi is a robot that combines the wire-driven robot CubiX, which is capable of environment connection, with the musculoskeletal humanoid Musashi using connector parts. CubiX and Musashi were assembled on the back pelvic area of Musashi using connector parts.

System Configuration and Controller of CubiXMusashi

CubiXMusashi is a robot that combines 2 robots into one, but they have separate power systems and computers. Regarding robot control, each robot is controlled by its respective computer, and their synchronization is achieved through communication between the 2 computers to generate the overall movement of CubiXMusashi. Musashi was controlled using inference by neural networks, and CubiX used wire length control.

Experiments

Pull-up Motion Experiment


CubiXMusashi connects 4 wires upward to the environment and grips the pull-up bar with both hands. The controlled parts of Musashi's body include the hands gripping the bar, the neck, waist, and legs for maintaining body pose, while no force is generated in the arms. The pull-up is executed by controlling the length of the 4 wires connected to the environment. This demonstrates that CubiXMusashi successfully performed a pull-up motion, lifting the entire body approximately 0.53 m while compensating for its own weight.

Rising from a Lying Pose Experiment


CubiXMusashi connects 6 wires extending upwards from CubiX to the environment. Among these 6 wires, 2 wires pass through Musashi's shoulders and connect to the environment. Additionally, to offset the forces attempting to bend Musashi's waist forward generated by these 2 wires, 2 wires, shown in orange, are connected from CubiX to Musashi's shoulders. CubiXMusashi demonstrates the ability to rise from a lying pose on the ground to a standing pose in this experiment.

Mid-Air Kicking


CubiXMusashi is connected to the environment by 5 wires. 4 wires of them are connected upwards, and 1 wire, shown in orange, is connected forwards for rotation during the kick. It is demonstrated that CubiXMusashi can achieve a kicking motion while rotating its body in the air.

Bibtex

@inproceedings{inoue2024cubixmusashi,
  title={{CubiXMusashi: Fusion of Wire-Driven CubiX and Musculoskeletal Humanoid Musashi toward Unlimited Performance}},
  author={Shintaro Inoue and Kento Kawaharazuka and Temma Suzuki and Sota Yuzaki and Yoshimoto Ribayashi and Yuta Sahara and Kei Okada},
  booktitle={2024 IEEE-RAS International Conference on Humanoid Robots},
  year={2024},
}

Contact

If you have any questions, please feel free to contact Shintaro Inoue.