Assistive wheelchair caster unit for step climbing — Improvement of design

The objective of this study is to develop the mechanism which assists the wheelchair user to climb a step. We designed the wheelchair caster unit which has a assistive mechanism. This unit is easily replaced with the conventional wheelchair caster. The proposed caster unit has two functions for assisting a step climbing. One is the assistive plates for enlarging radius of the caster imaginarily. The other is a lock-function of caster rotation for yaw axis, which enables easy climbing with oblique approach. Our first prototype shows good performance for above mentioned two functions, and can assists step climbing. However, the first prototype is heavy, because of the electromagnetic tooth clutch for the lock-function. Therefore this paper improve the lock-function of first prototype, and report the outline of the new prototype. The new lock-function was composed by the solenoid, the lack and pinion gear. By using the solenoid, the unit realizes weight and cost saving and low power consumption.