Posture adjustment according to load inclination for a passive-type assistive wheelchair

Abstract

Considering the road inclination conditions, we proposed an upper body posture adjustment system for a passive-type assistive wheelchair. On an inclined road, there is a high probability that a wheelchair will move in a direction that is different from that desired by its user. In our previous research, we proposed a system that estimated a wheelchair user's intentions and worked passively to complement their intentional force. This was accomplished by negating the wheel traction that was generated by the road's inclination using only the servo brakes on each wheel. However, in some cases, our system failed to assist the driving motion of the user because it negated only the gravitational force. Therefore, our wheelchair succeeded in avoiding the unintended movement, but its user was required to row the hand rims with a considerable amount of force to overcome these braking forces. Consequently, we proposed an upper body posture adjustment system that adapts to the inclined road conditions and reduces the wheel traction that is generated by gravity. The proposed system inclined the wheelchair seat and aligned the upper body posture of its user to the center position of the wheelchair. Using this method, the proposed system maintained the position of the user's center of gravity with respect to the center position of the wheelchair. Our experimental findings suggested that the proposed passive-type assistive wheelchair can complement the user's intentional force with smaller brake tractions, indicating that the user can drive the wheelchair using less physical strength.