Abstract Excessive oscillation of the load centroid in the sagittal plane imposes impact and oscillatory force on the shoulders and back, contributing to upper-body muscle fatigue. To address this issue, this paper investigates a hip-joint driven backpack exoskeleton with a passive adaptive centroid adjustment mechanism, integrating a four-bar linkage with a sinusoidal mechanism to dynamically regulate the load centroid. Kinematics models of the human-load and human-exoskeleton-load systems are developed based on an extended six-bar representation, enabling comparative analysis of centroid trajectories. Dynamic models for the upper torso, single-leg, and double-leg support phases are constructed to evaluate pressure and joint torques variations. OpenSim-based musculoskeletal simulations further analyze torque distribution and metabolic activity of key gait-related muscles. Results demonstrate that the exoskeleton effectively reduces load centroid fluctuation and redistributes joint torques. Experimentally, it achieves an 85% reduction in peak load centroid displacement, a 49% decrease in total shoulder pressure, and a 50% reduction in lumbar swing amplitude during the single support phase. Simulations show lumbar and hip torque reductions of 52.68% and 23.64%, respectively, and a 32.85% decrease in erector spinae metabolic activity. This work addresses a gap in passive exoskeletons by introducing a rigid mechanism that adaptively shifts the load centroid without active control, verified through integrated modeling and experiment. It provides an effective strategy to reduce upper-body strain and improve gait efficiency during load-bearing locomotion.
Wei et al. (Thu,) studied this question.