An Anthropomorphic Robotic Finger with Innate Human-Finger-Like Biomechanical Advantages Part I: Design, Ligamentous Joint and Extensor Mechanism

Exploring human hand fundamental biomechanical features and exploiting them to robotic hands have been proven to be an effective approach to enhancing artificial hands’ perfor- mance, especially when interacting with various objects in dynamic unstructured environments. In this article, a bioinspired anthro- pomorphic robotic finger is first proposed, which embeds human finger musculoskeletal features in the design. Based on this design, three human-finger-like biomechanical advantages are systemati- cally investigated and embodied in the bioinspired robotic finger. This article for the first time derives, presents, and experimentally verifies the mathematical models for the variable stiffness of finger ligamentousjointsandself-adaptivemorphingmechanismoffinger flexible tendon sheaths, and validates and compares the influence of the reticular and linear extensor morphologies on fingertip feasible forces in three-dimensional (3-D) space. In this Part I of the article, two of the biomechanical properties, i.e., joint stiffness generated by the ligamentous joint of the finger, and fingertip feasible force space influenced by the reticular extensor mecha- nism are systematically investigated through theoretical modeling and experimental verification. Correspondingly, two biomechani- cal advantages were found, i.e., the ligamentous joint of the finger could provide anisotropic variable joint stiffness, enhancing the adaptivity, dexterity, and stability of fingers; and a reticular exten- sor mechanism could enlarge the fingertip feasible force space in 3-D space by 30.9% theoretically and 146.4% experimentally on Manuscript received 19 May 2022; accepted 16 July 2022. Date of publication 5 September 2022; date of current version 8 February 2023. This work was supported in part by the Project of National Key R&D Program of China under Grant 2018YFC2001300 and in part by the Project of National Natural Science Foundation of China under Grant 91948302, Grant 91848204, Grant 52005209, and Grant 51675222. This paper was recommended for publication by Associate Editor F. Ficuciello and Editor E. Yoshida upon evaluation of the reviewers’ comments. (Corresponding authors: Guowu Wei; Lei Ren.) Yiming Zhu is with the School of Mechanical and Aerospace and Civil Engi- neering, University of Manchester, M13 9PL Manchester, U.K., and also with the College of Intelligence Science and Technology, National University of Defense Technology, 410073 Changsha, China (e-mail: yiming.zhu@manchester.ac.uk). Guowu Wei is with the School of Science, Engineering, and Environment, University of Salford, M5 4WT Salford, U.K. (e-mail: g.wei@salford.ac.uk). Lei Ren is with the School of Mechanical, Aerospace, and Civil Engineering, University of Manchester, M13 9PL Manchester, U.K., and also with the Key Laboratory of Bionic Engineering and Ministry of Education, Jilin University, Changchun 130012, China (e-mail: lei.ren@manchester.ac.uk). Zirong Luo and Jianzhong Shang are with the College of Intelligence Science and Technology, National University of Defense Technology, 410073 Changsha, China (e-mail: luozirong@nudt.edu.cn; jz_shang_nudt@163.com). Color versions of one or more figures in this article are available at https://doi.org/10.1109/TRO.2022.3200006. Digital Object Identifier 10.1109/TRO.2022.3200006 average compared with the linear extensor, contributing to enrich force conditions during interactions. The third biomechanical ad- vantage, i.e., fingertip force–velocity workspace can be augmented through the flexible tendon sheath, and grasping tests for a robotic hand designed with the aforementioned advantages are presented in Part II of this article.