Development of Power-Assisted Attendant-Propelled Wheelchair.

Different types of power add-on units for attendant propelled wheelchairs have been developed and some of them are available on the market. Most of them do not consider the operator's pushing or pulling capability and he must adjust the power with a switch while holding the pushing handle. It is not easy for elderly people to do so especially when they need to take a prompt action such as sudden stop. Sensing the propulsion force would make the operation much easier instead of operating the switch. In this study, one motor system is adopted with a differential gear for maneuverability and compactness. As propulsion force sensor, a magnetostrictive sensor is employed and it detects pushing or pulling force by the operator. As control method a model reference control is proposed. The power assist is controlled as if a lightweight wheelchair was operated on solid flat ground by the operator. The model is described with mass and viscous damping factor. A prototype was made and initially tested on floor and slope. It was found effective to reduce operator's propelling force. This paper describes its control method, mechanical design, control circuit, control simulation and test results of the prototype.