Analysis of shoulder motion kinematics based on a spatial linkage model and validation using Vicon motion capture.

As the central hub connecting the upper limb and torso, the shoulder has complex spatial kinematics driven by multi-joint coordination. To realize structured modeling and quantitative evaluation of natural shoulder motion, this study proposes a kinematic modeling approach based on an open-chain spatial hybrid linkage mechanism, validated by the Vicon motion capture system. A 7-degree-of-freedom spatial linkage model incorporating SC, AC, GH and ST joints is constructed, with defined degrees of freedom and coupling relationships. Static equilibrium models in three planes are established to assess joint torque distribution. Vicon-based 3D trajectory data of anatomical markers are analyzed for motion consistency, verifying the model's biomechanical plausibility and reconstruction accuracy, which lays a theoretical foundation for shoulder rehabilitation robots and intelligent exoskeletons.