Design of the mechanical arm joint structure

Abstract

This paper investigates robotic arm joints utilizing double universal joint J structural design and structural optimization. In a robotic drive system, a standard single universal joint introduces fixed angular velocity fluctuations, leading to mechanical vibration and reduced control accuracy. To address these issues, this study focuses on double universal joints, aiming to achieve constant velocity transmission through kinematic phase compensation. The study first quantifies the inhomogeneity of velocity relative to axial angle through theoretical kinematic analysis. A comprehensive model of the 3D joint assembly, including intermediate shafts, cross-threads, and sliding shoulder frames, was developed to promote the integration of rotational flexibility and axial displacement compensation. Subsequently, the structural reliability of the component was verified by finite element analysis (FEA) in an ANSYS environment. A high-quality hexahedral mesh was employed, with special attention to local refinement in the critical stress concentration zones to ensure numerical convergence and accuracy. The simulation results showed that the double universal joint effectively eliminated the periodic speed fluctuations unique to single universal joint systems. The structural analysis showed that the maximum stress under peak torque conditions was within the yield strength limit of the selected alloy steel, ensuring a sufficient safety factor for high-torque robot maneuvers. In addition, the integration of sliding forks provided effective axial compensation for structural deflection. The research results confirm that the proposed joint design provides a robust and stable solution for robotic applications requiring high loads and smooth motion trajectories.