A state-space approach to analyzing vertical vibration behavior in wheelchair-occupant systems with a composite model

Vertical vibrations are a major source of discomfort and health risks for wheelchair users. This paper presents a mathematical model and a state-of-the-art solving method that simulate the vertical vibration responses of a wheelchair-occupant system with 11-degrees-of-freedom (DOF). The model is a composite one that integrates human and vehicle lumped parameter models, considering factors such as terrain, wheelchair components and user actions. The method employs state-space analysis and advanced modeling techniques to derive vibration transfer functions for the linear model. The paper evaluates the impact of a foam-based seat cushion on vibration transmission and ride comfort by conducting experiments and comparing the acceleration responses with the International Organization for Standardization (ISO) 2631:1978 standard for 25 -minute exposure limit. The results indicate that the torso is the most sensitive body segment, while the pelvis is the most resilient one. The results also demonstrate that the seat cushion effectively attenuates the vibration levels for all body segments and ensures that they are below the ISO exposure limit curve for 25 -minute exposure. The paper provides a useful tool for designing and testing wheelchair cushions and other interventions to enhance the ride comfort and safety of wheelchair users. The paper also introduces a cutting-edge modeling technique that can be extended to a novel multi-degree-of-freedom (MDOF) model of a wheelchair-occupant system that simulates the vertical vibrations caused by different input excitations for the four wheels. Future research will investigate the potential of Newmark algorithms in predicting this MDOF model. This paper contributes to the advancement of knowledge and practice in the field of wheelchair systems and occupant comfort.