Motion pattern analysis of semi-looper type robots with four links

For worm robots applied to pipe inspection and colonoscopy, earthworm-like robots with a locomotion pattern in backward wave or green caterpillar-like robots with a locomotion pattern in forward wave have been studied widely. It should be noted, however, that a method using a single and fixed locomotion pattern is not desirable in the sense of mobility cost, if there are various changes in pipe diameter. In this paper, locomotion patterns are considered for a semi-looper-like robot, which adopts a locomotion pattern of green caterpillars as the basic motion and sometimes can realize a locomotion pattern of looper, whose motion approximately consists of two rhythms or relatively low rhythm.