JRM Vol.36 No.2 pp. 406-414
doi: 10.20965/jrm.2024.p0406


Cam-Like Mechanism in Intertarsal Joints of Ratites and its Design Framework

Kazuki Ito*, Sayaka Hida**, Tetsuya Kinugasa*** ORCID Icon, Kentaro Chiba*** ORCID Icon, Yu Okuda***, Miwa Ichikawa***, Tsukasa Okoshi***, Ryuji Takasaki*** ORCID Icon, Ryota Hayashi***, Koji Yoshida***, and Koichi Osuka* ORCID Icon

*Graduate School of Engineering, Osaka University
2-1 Yamadaoka, Suita, Osaka 565-0871, Japan

**IHI Jet Service Co., Ltd.
1-33-3 Kichijoji-honmachi, Musashino, Tokyo 180-0004, Japan

***Okayama University of Science
1-1 Ridai-cho, Kita-ku, Okayama 700-0005, Japan

September 12, 2023
November 27, 2023
April 20, 2024
intertarsal joint, engage-disengage mechanism, locomotion, passive mechanism, biomechanics

In this study, the cam-like passive mechanism, known as the engage–disengage mechanism (EDM) of the intertarsal joint of ratites, and its design principles are investigated. This mechanism operates through the interplay of a muscle and three ligaments located on the medial and lateral sides of the intertarsal joint and the articular surface morphology of the tibiotarsus. The interplay of the musculoskeletal ligamentous elements creates two stable equilibrium points when they are almost fully extended and flexed. To elucidate the EDM in the intertarsal joints of ratites, we dissected the hindlimb of an emu (Dromaius novaehollandiae) and examined anatomical features around the joint. Subsequently, we replicated the intertarsal joint of ratites using a physical model. This model consists of three-dimensional-printed ostrich bones, coil springs, and nylon strings simulating the muscle and ligaments. This model successfully replicated the EDM and facilitated the analysis of the interplay of musculoskeletal ligamentous elements. We demonstrated that the medial ligaments and the morphology of the tibiotarsal articular surface play significant roles in facilitating the execution of EDM. Furthermore, we observed that the articular surface morphology resembles a well-known cam system in engineering and is responsible for the EDM.

Cam surface and intertarsal joint motion

Cam surface and intertarsal joint motion

Cite this article as:
K. Ito, S. Hida, T. Kinugasa, K. Chiba, Y. Okuda, M. Ichikawa, T. Okoshi, R. Takasaki, R. Hayashi, K. Yoshida, and K. Osuka, “Cam-Like Mechanism in Intertarsal Joints of Ratites and its Design Framework,” J. Robot. Mechatron., Vol.36 No.2, pp. 406-414, 2024.
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Last updated on May. 19, 2024