Development of an Omnidirectional Rolling Leg Mechanism for Application in a Locomotion Machine
Nobutoshi Yamazaki and Takehiro Nishiie
Faculty of Science and Technology, Keio University, 3-14-1 Hiyosi, Kouhoku-ku, Yokohama 223-8522, Japan
The wheelchair is a superior assistive apparatus in open and flat spaces; however, in Japanese style houses, the conventional wheelchair has several drawbacks, including difficulty in negotiating tight corners and moving over obstacles such as thresholds, as well as damage to delicate surfaces such as Tatami mats. Therefore, we developed a new six-legged mobility assisting machine. The individual legs are designed to have a semi-circular arced sole, which can be made to roll like a wheel in the stance phase using a cam and crank mechanism. Therefore, the machine can move efficiently without vertical sway and can pass over step-like obstacles twice as high as those that can be passed over in a wheelchair having wheels with the same radius of curvature. Furthermore, the machine can move in any direction while keeping the passenger facing in the same direction. This is accomplished by simultaneously rotating all six legs around their respective vertical axes at the sole contact point. A 2/3-scale prototype machine (hexagon side: 232mm, height: 222mm, leg length: 100mm, and total weight: 8kg) produced smooth movement. The prototype has a velocity of 2.7m/min and a turning speed of 90degree/sec and has a passable step height of 13mm. The machine is easy to control because it is driven by only two motors: one for propulsion and one for turning.
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