Situation-based servo braking assistance for a manual wheelchair

This paper proposes a novel driving-assistance system for manual wheelchairs with consideration of both uphill and downhill conditions. On an inclined road, there is a high risk of a wheelchair moving in a direction that the user does not intend. In our previous works, the user has driven our assistive wheelchair in the usual manner. Our proposed system estimates its user's intentions and passively works to complement their intentional force by negating the wheel traction that is generated by the road's inclination using only the servo brakes on each wheel. Nevertheless, in some cases, our system fails to assist the driving motion of its user because the user drives the wheelchair in several ways that depend upon the environmental condition, for example, during uphill or downhill driving. The required assistance is not constant according to the situation, and it is difficult to assist with one wheel-control algorithm. Therefore, in this study, we first investigate the required assistance condition according to the driving situation by conducting a preliminary experiment with wheelchair users. Considering the results of this investigation, we then propose a novel user interface that intuitively shows the system information and a wheel-control algorithm that selects a suitable wheel controller according to the driving situation.