Assistive Caster Unit of Wheelchair for Step Climbing

Th is paper proposes the wheelchair caster unit which assists manual wheelchair users in a step climbing. Th is caster unit has 2 functions. First one is the assistive plate which en larges radius of a front wheel equivalently in the limited space between main frame and foot rest. When the caster meets the step, the assistive plates are rotated as same manner as a general big wheel. Thus, the user driving force is reduced compared with conventional small caster wheel. Second one is the lock mechanism. Th is mechanism enables to make fu ll use of user's driv ing force in case of oblique climbing by holding yaw axis rotation of the caster. In addition, the caster unit can be easily converted from a conventional caster without any modifications on the main frame. In order to verify the efficiency of proposed caster unit, this paper conducted two experiments: I) Dynamics simulation before constructing a prototype. II) Evaluation experiment using a prototype. In the I) simulation stage, we verified two functions by measuring the driving torque of main wheel in a dynamics simulation. In the II) real experiment, we measured the strain between hand rim and main wheel by using the load cell. In both verifications, the efficiency was verified. Thus it turned out that proposed caster unit can reduce user's driving force, namely it can assist manual wheelchair user in a step climbing.