Motion Control of Cycling Wheelchair with Continuously Variable Transmission and Clutch

The cycling wheelchair, which is pedaled like a bicycle, is an effective device for improving its user's activities of daily living. It is commercially available in Japan, and is currently being used by hospitals and rehabilitation facilities. However, many patients, particularly those with lower-limb disabilities, would like to use it both indoors and outdoors. Indoor use requires relatively slow forward and backward movement combined with a small turning radius, all of which increase maneuverability in confined spaces. In contrast, outdoor use requires the cycling wheelchair to move faster with bicycle-like mobility and a freewheel mechanism for comfortable driving, although the latter precludes pedaling backward. In addition, the user would like to ascend slopes easily and descend them safely. Hence, the cycling wheelchair requires a transmission system that can change the gear ratio based on the environment, and an automatic braking system. In this letter, we discuss in more detail the assistive functions required of the cycling wheelchair, and we realize them by developing a new cycling wheelchair with a continuously variable transmission and clutch. In addition, we conduct experiments to illustrate the validity of the proposed cycling wheelchair and its control method.