BIOMECHANICAL MODELING OF THE PELVIS-FOOT MODULE OF A PASSIVE EXOSKELETON
DOI:
https://doi.org/10.34185/1991-7848.itmm.2026.01.038Keywords:
passive exoskeleton, rehabilitation, kinematics, force analysis, finite-element method, spring-damper moduleAbstract
This study presents a kinematic and force analysis of the pelvis-foot section of a passive lower-limb exoskeleton for the rehabilitation of individuals with musculoskeletal disorders. The architecture comprises a two-segment foot, shank and thigh links, a pelvic plate, and energy-storing spring-damper modules. During sit-to-stand transitions, these modules accumulate and release energy, significantly reducing user muscular effort. A closed-vector-loop kinematic model for a planar three-link chain was simulated in Mathcad and validated using a MapleSim multibody model, confirming physiologically sound joint trajectories. Force analysis addressed maximum bending moments during seating transition. Finite-element analysis of the critically loaded thigh link in SolidWorks Simulation revealed a maximum equivalent stress of 154 MPa and a tip deflection of 0.3 mm under a 1.5 kN design load. The design fully satisfies strength criteria for steel St. 3 structural elements, proving its feasibility for passive
rehabilitation assistance.
References
Rodríguez-Fernández A., Lobo-Prat J., Font-Llagunes J. M. Systematic review on wearable lower-limb exoskeletons for gait training in neuromuscular impairments. Journal of NeuroEngineering and Rehabilitation. 2021. Vol. 18, No. 1. P. 22. URL: https://doi.org/10.1186/s12984-021-00815-5
Nepomuceno P., Souza W. H., Pakosh M., Musselman K. E., Craven B. C. Exoskeleton-based exercises for overground gait and balance rehabilitation in spinal cord injury: a systematic review of dose and dosage parameters. Journal of NeuroEngineering and Rehabilitation. 2024. Vol. 21, No. 1. P. 73. URL: https://doi.org/10.1186/s12984-024-01365-2
Pai Y. C., Rogers M. W. Speed variation and resultant joint torques during sit-to-stand. Archives of Physical Medicine and Rehabilitation. 1991. Vol. 72, No. 11. P. 881–885. URL: https://doi.org/10.1016/0003-9993(91)90004-3
Lee H., Kim S. H., Park H.-S. A fully soft and passive assistive device to lower the metabolic cost of sit-to-stand. Frontiers in Bioengineering and Biotechnology. 2020. Vol. 8. P. 966. URL: https://doi.org/10.3389/fbioe.2020.00966
Korendiy V., Markovych B., Tys M., Vyshnevskyi O. Predictive Simulation of the Human Sit-to-Stand Transition // Modeling, control and information technologies (MCIT). 2025. No. 8. – P. 272–275. URL: https://doi.org/10.31713/MCIT.2025.084
