Journal of Bionic Engineering (2025) 22:1265–1286https://doi.org/10.1007/s42235-025-00690-z

Design and Experiment of a Compact 3-DOF Humanoid Wrist with High Payload Capacity

Shengyin Wang1  · Zirong Luo1  · Shanjun Chen1  · Yiming Zhu1  · Haisen Zeng1  · Jianzhong Shang1

1 College of Intelligence Science and Technology, National University of Defense Technology, Changsha 410073, China

Abstract 

The wrist unit is crucial in humanoid robots, determining their operational dexterity and precision. To address current challenges such as excessive size, limited Degrees of Freedom (DoFs), and insufficient load capacity, we propose a 3-DoF humanoid wrist inspired by the human forearm and wrist anatomy. This paper explores the principles of wrist bionic design and introduces a parallel mechanism actuated by a brushless DC motor (BLDC)-ball screw to achieve flexion/ extension (F/E) and radial flexion/ulnar deviation (R/U), as along with pronation/supination (P/S) through an end-coupling design. We conducted an analysis on the inverse kinematic model and singularities of the humanoid wrist. Additionally, the workspace and motion capabilities of the humanoid wrist were evaluated. A prototype based on this design was built to demonstrate its motion and functional performance, verifying the feasibility and practicality of the humanoid wrist. This research provides a more compact design approach for future humanoid wrist development. 

Keywords Humanoid robots · Humanoid wrist · Bionic design · 3-DoF