A Preliminary Study of a Polarizing Effect Based Torsion Sensor for a Power Assisted Wheelchair Driving Control

Abstract

A handrim-activated power-assisted wheelchair (HAPAW) is a special wheelchair that combines the advantages of a manual wheelchair with those of an electric-powered wheelchair. In this study, we develop a polarizing-effect-based noncontact torque sensor for a HAPAW. Two main considerations were taken when developing the HAPAW: first, effectively sensing the user-propelled torque applied to the handrim is important, and second, developing a small lightweight driving mechanism consisting of a motor and gears is essential. Therefore, this study presents a new noncontact torque recognition method based on the polarizing effect of light. Two polarizers are placed in parallel on the wheel hub and the handrim to determine the driving intention of the user by sensing the changing intensity of the light passing through the polarizers that is proportional to the handrim movement. A mock-up was fabricated and the changes in light intensity were measured with optical detectors to verify the proposed sensor mechanism. The experimental results are in good agreement with the simulation results. The measured sensor output had enough resolution and accuracy to evaluate the driving intention of the HAPAW user.