Novel 7-DoF Kinematic Architecture for Occupational Upper-Limb Exoskeletons with Explicit Scapulothoracic Mobility and Integrated Trunk–Shoulder–Elbow Coupling

Upper-limb exoskeletons require precise geometric alignment between the device’s mechanical axes and the user’s anatomical joints to preserve physiological mobility and prevent functional constraints; however, many occupational exoskeleton designs oversimplify scapulothoracic mobility, potentially reducing the functional workspace and leading to kinematic misalignment during arm elevation tasks. In this context, the present study addresses this limitation by developing the design, kinematic modeling, and experimental validation of a 7-DoF passive upper-limb exoskeleton organized into dorsal, shoulder, and elbow modules, where the proposed architecture explicitly incorporates 3-DoFs in the dorsal region to accommodate scapular motion within a unified serial kinematic chain. From a modeling standpoint, the kinematic formulation is established using the Denavit–Hartenberg convention, enabling the analysis of the workspace, the properties of the Jacobian matrix, and the identification of potential singular configurations; simulation results demonstrate a continuous workspace within the evaluated functional range, with no singularities detected in the region of interest. Regarding experimental validation, two complementary approaches are implemented: a 2D video-based analysis using Kinovea compares joint trajectories with and without the exoskeleton, revealing strong kinematic agreement (RMSE⩽ 6.11 mm, R2≥ 0.8746), while a 3D motion-capture validation using the Qualisys system evaluates the kinematic coupling between the human arm and the exoskeleton during assisted movement, yielding high correspondence between both trajectories (R2 = 0.975). Overall, the results confirm the geometric consistency of the proposed architecture and provide a solid methodological foundation for the future development of passive or hybrid upper-limb exoskeletons with integrated dorsal mobility.