Power-assist Control of an Add-on Type Electric Wheelchair with the Active-caster

In this paper, we propose an add-on electric drive system for manual wheelchairs using one active caster, which has been the driving wheel developed for omnidirectional robots. Active casters can instantly generate a velocity vector in any direction by the cooperative control of two motors. The active-caster is installed at the rear of a manual wheelchair to control the two degrees of freedom of the wheelchair movements: forward movement and turning. Furthermore, a torque detection system is installed into the power transmission of the active caster to measure the direction and magnitude of an applied force acting on the wheel. A power assist control of the wheelchair is performed based on this force detection. Therefore, there is no need to install any force detection devices on a manual wheelchair, it is possible to create wheelchair motions with electric motor support by applying force to any part of the wheelchair. This makes it possible for the wheelchair to be moved by pushing and pulling the wheelchair by a caregiver, by operating the large wheels by the passenger himself, by pushing the floor with his legs, or by pushing and pulling the desk with his hands. We demonstrate the feasibility of these functions through experiments using a prototype wheelchair.