Mechanism Design and Evaluation of a Threaded Rod-Driven Wheelchair-to-Bed Transformation System

This study presents the design and simulation-based evaluation of a low-cost, multifunctional wheelchair-to-bed transformation system powered by a threaded rod mechanism. Developed to enhance autonomy, comfort, and safety for paraplegic and quadriplegic patients, the proposed system utilizes a self-locking DC motor-driven threaded shaft that enables smooth, controlled transitions between sitting and lying positions without requiring caregiver assistance. Unlike conventional systems that employ hydraulic or hydrostatic actuators often associated with complexity, maintenance challenges, and high cost—this design prioritizes mechanical simplicity, affordability, and user accessibility. The system supports voice and joystick-based control, catering to users with varying physical capabilities. SolidWorks simulations and performance analysis demonstrate that the mechanism completes full transformation in 28 seconds under a 150 kg load, ensuring stability, energy efficiency, and ease of use. Comparative evaluation with existing actuator-based systems confirms the advantages of the threaded rod mechanism in terms of reliability, power consumption, and passive safety. This research introduces a simple and affordable assistive mobility solution with strong applicability in clinical and home care environments.