DESIGN AND COMPARISON BASED ON FINITE ELEMENT ANALYSIS OF A NON-PNEUMATIC WHEEL TO IMPROVE WHEELCHAIR COMFORT

The standard wheelchair design features two large rear wheels fixed parallel to the seat and two smaller, front swivel wheels. While functional, this configuration transmits terrain-induced vibrations directly to the user, especially through the front wheels, which have limited shock-absorption capacity. For users with neuromuscular conditions, such vibrations can trigger spastic responses, reducing comfort and overall usability. This study explores non-pneumatic tires (NPTs) as a viable alternative to traditional front wheels, focusing on structural performance and ergonomic improvements. A non-pneumatic front wheel based on cellular/lattice structures is proposed to mitigate vibrations from irregular terrain without relying on external damping systems. The goal is to increase comfort, enhance user stability, and maintain manoeuvrability. To support this goal, one of the main objectives of this work is to use finite element analysis (FEA) as an initial comparison tool among different internal NPT geometries, enabling their mechanical behaviour to be evaluated under equivalent conditions and thereby supporting the selection of the most suitable alternative for subsequent experimental validation and additive manufacturing. Three-dimensional wheel models were created in CAD and analysed through non-linear static finite element simulations, assigning thermoplastic polyurethane (TPU) to the tire–spoke assembly and polylactic acid (PLA) to the rim. The designs were compared in terms of stress distribution, axial displacements, strain levels, structural stiffness, and stiffness-to-mass efficiency, while maintaining identical boundary conditions and material settings. Design optimisation focused on variables including material thickness, spoke inclination, and spoke count, striking a balance between rigidity and flexibility. The analysed configurations combine a rigid PLA rim with a flexible TPU tire and spoke system, providing controlled deformation while preserving mechanical strength. Among the three geometries studied, the honeycomb lattice showed the most favourable stiffness-to-mass balance and was identified as the most suitable candidate for future 3D-printed prototyping and bench testing. Overall, the results support the feasibility of incorporating additively manufactured NPT front wheels into conventional wheelchairs to improve accessibility and comfort. Key Words: wheelchairs, cellular structures, 3D printing, impact absorption, finite elements,