Title: Design and control of the bionic ankle joint with multiple pneumatic artificial muscles

Authors: Delei Fang; Fangyuan Ren; Hao Wen; Zhenyu Yan; Jianwei Wang; Feipeng Li; Jie Tang; Junxia Zhang

Addresses: College of Mechanical Engineering, Tianjin University of Science and Technology, Tianjin, 300222, China ' College of Mechanical Engineering, Tianjin University of Science and Technology, Tianjin, 300222, China ' College of Mechanical Engineering, Tianjin University of Science and Technology, Tianjin, 300222, China ' School of Engineering Mathematics and Technology, University of Bristol, Bristol, BS8 1TW, UK ' College of Mechanical Engineering, Tianjin University of Science and Technology, Tianjin, 300222, China ' College of Mechanical Engineering, Tianjin University of Science and Technology, Tianjin, 300222, China ' Aeronautical Engineering Institute, Civil Aviation University of China, Tianjin, 300300, China ' College of Mechanical Engineering, Tianjin University of Science and Technology, Tianjin, 300222, China

Abstract: To address the time-varying output force and compliance issues in pneumatic artificial muscle-driven robots, this paper proposes a bionic ankle joint inspired by human muscle structure. By recruiting multiple pneumatic artificial muscles and implementing compliance control, the overall output performance is enhanced. This study presents the structural design of the bionic ankle joint with multiple pneumatic artificial muscles and analyses its bionic actuation mechanism. Furthermore, impedance control and adaptive impedance control models are developed, followed by a simulation-based analysis of the output angular characteristics and force response. A performance evaluation platform is constructed for experimental validation. The results indicate that the bionic ankle joint with adaptive impedance control effectively reduces angular tracking errors and output force deviations, while improving joint compliance.

Keywords: bionic ankle joint; pneumatic artificial muscle; impedance control.

DOI: 10.1504/IJHM.2026.152973

International Journal of Hydromechatronics, 2026 Vol.9 No.1, pp.128 - 154

Received: 29 Jun 2025
Accepted: 25 Aug 2025
Published online: 17 Apr 2026 *

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