Improvement of assistive wheelchair caster unit for step climbing

The objective of this study is to develop the mechanism which assists the wheelchair user to climb a step. The wheelchair caster unit with an assistive mechanism is developed. This unit is easily replaced with the conventional wheelchair caster. The proposed caster unit has two functions to assist the step climbing. One is the assistive plates to enlarge the caster radius imaginarily. The other is a lock-function to yaw axis caster rotation, which realize 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 is used 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 rack and pinion gear. By using the solenoid, the unit realizes weight and cost saving and low power consumption, and it is more practical design than first prototype.