A Study of the Wheel-Feet Mechanism for Stair Climbing.

Although wheels are very efficient on flat and tight terrain locomotion, they cannot climb up stairs or even a step. Stairs or steps are the most popular obstacles in outside applications of mobile robots especially in artificial environments.This paper provides a new wheel-feet hybrid mechanism, named as Enhanced Wheel System (EWS), for rough terrain locomotion especially for climbing up stairs or a step. To climb up stairs or a step by the EWS, several ‘feet’ combined on each wheel (named as ‘wheel-feet’) are kept always horizontal by parallel link mechanisms controlled by the servo-mechanism. Some prototype machines with the EWS have been made to show that they are able to run smoothly on flat terrain by wheels and climb up and down stairs using those ‘feet’.In this paper, the authors describe a new prototype machine (EWS-4) with a carrier has been made to certify that the EWS can be used in actual use, carrying about 100[kg] of payload on a carrier. EWS-4 has 4 ‘wheel-feet’ with 4 ‘feet’ in each ‘wheel-feet’, and 4 wheels to run. The specifications of EWS-4 are that 1600[mm] long, 980[mm] wide, 950[mm] high, 1000[mm] of wheel base, 600[mm] of tread and about 200[kg] of weight. Experiments to climb up and down stairs of 150[mm] high and 350[mm] deep, were held successfully carrying about 70[kg] operator and control units.