Design and analysis of an affordable manual sit-to-stand wheelchair for disabled individuals

PURPOSE: The individuals with lower-limb disabilities often experience considerable difficulty during sit-to-stand (STS) transitions, limiting their independence and increasing reliance on caregivers. According to the World Health Organisation (WHO, 2023), nearly 80 million people worldwide require wheelchairs. METHOD: This study presents the design and performance evaluation of an affordable manual sit-to-stand wheelchair that incorporates ergonomic and anthropometric design principles with a three-bar linkage mechanism, ball screw drive, scissor-lift structure, force-balancing mechanism, and optimised gear ratio to ensure stable, controlled, and energy-efficient operation without electrical actuators. Structural validation of design using finite element analysis demonstrated a maximum frame deformation of 2.2 mm and a factor of safety of 2.5 under a static load of 120 kg, confirming the mechanical reliability of the design. Human testing is conducted with 25 participants (15 wheelchair users and 10 healthy volunteers), while clinical evaluation is performed under a physiotherapist's supervision using standardised functional assessment protocols. RESULT: The average sit-to-stand transition time is 9.5 ± 1.8 s, with 90% of participants achieving successful independent standing. Force analysis indicated that the proposed linkage mechanism reduced the operating force to approximately 10 N, corresponding to a 45.6% reduction in user effort. Furthermore, usability assessment yielded a mean System Usability Scale (SUS) score of 86.3/100, indicating excellent user acceptance. CONCLUSION: The findings demonstrate that the proposed STS wheelchair is a safe, mechanically robust, and cost-effective assistive mobility solution that enhances user independence, reduces caregiver burden, and improves the quality of life for individuals with mobility impairments, particularly in low-resource settings.