The purpose of this paper is to realize a kind of more natural and efficient walking fot a biped robot. In the beginning of paper, we discuss methods of walking based on passive dynamic walking mechanism and naturalness of walking. Next, we introduce some kinds of walking using variable length knees with constraint control of a body.
Finally, our biped called Prototype Biped Emu IV (PBEmu-IV) is introduced, some experimented results are shown to verify the effectiveness of our strategy for biped walking, and the frequency analysis is introduced for walking. As the results, walking frequencies only depended on frequencies of knee length variations, and walking is excited around the characteristics frequency of a leg. That is to say, some effective frequencies for biped walking are appeared in the sense of high walking gains.
