Raymond's Homepage
Partway through 2003, a friend, David Wyatt, and I came across a design in Dr. Hans Moravec's book, "Mind Children", for a novel design for robot locomotion. A cross between wheels and legs, this design could run across a smooth surface as quickly and efficiently as any wheeled vehicle, yet it could climb stairs, including open stairs, as well as any equivalent legged vehicle! The key to this high degree of mobility lay in the robot having 5 vertically telescopic legs, arranged at the points of a regular pentagon, at the base of which was a wheel. Travelling on a flat surface, each wheel simply rotates as normal (and in the original design, attributed to Hitachi, was steerable). To climb stairs and other obstacles, each wheel was raised in turn, the robot rolled forward then the leg put down on top of whatever obstacle was encountered. We decided to build this robot and, over the course of a couple of months, designed and manufactured the 5 leg modules, each consisting of two servos, sense switches, telescoping mechanism and microcontroller board, and programmed these boards and a central microcontroller to automatically climb stairs! The control mechanism was elegantly simple - each leg was raised if its forward bump sensor hit something except of another leg was already raised, then the robot was moved forward, then the leg put down until its vertical contact sensor was activated. A leg that fell off an obstacle would be put down until its vertical contact sensor was reactivated. We were very fortunate when we demonstrated the robot - we encountered a case of the inverse demo effect! We couldn't get it to work in practice but in front of the professor, it worked beautifully! It climbed and descended stairs we had built for it 3 times and climbed over a multimeter without missing a beat! Pitty we couldn't make it do the same when we wanted to video it ... ah well :-) We looked through publications, patent records and the like and couldn't find any reference to the Hitachi robot, we even asked Dr. Moravec if he had any more details about the robot but he couldn't find anything. Then in 2004, I was in contact with Dr. Shigeo Hirose who had more recently also developed a similar 8 wheeled robot, dubbed "ZeroCarrier"! According to him, the Hitachi robot was by a Dr. Ichikawa but no reference could be found to it either. My old photo gallery of it is still up here! |
