Feedback Control Design for Bipedal Robots

Regents Of The University Of Michigan - Ann Arbor, Ann Arbor MI

Investigators

Abstract

The motivation for studying walking robots arises from diverse sociological and commercial interests, ranging from the desire to replace humans in hazardous occupations, to the restoration of motion in the disabled, the possibility of using legged locomotion in terrain that is unsuitable for wheeled locomotion, and the psychological appeal of machines that operate in anthropomorphic or animal-like ways. Feedback control is an integral part of achieving bipedal locomotion. Control system design for biped robots poses numerous challenges due to the many degrees of freedom in the mechanisms, the intermittent and unilateral nature of the contact conditions with the environment, and underactuation. The most technologically advanced biped robots today are walking on the basis of a heuristic control principle that imposes a flat-footed walking motion in order to avoid dealing with the underactuation that comes with foot rotation (i.e., toe roll and heel strike). Professor Grizzle's research will develop the analytical foundations of walking with an anthropomorphic gait. By not relying on heuristics, significantly improved feedback controllers will be designed that allow the natural rotation of the foot during the stance phase of walking, while still guaranteeing stability of the walking motion. Beyond a certain speed, walking is no longer efficient (or even possible). The extremely challenging problem of controlling a running motion of a bipedal robot will be investigated, both theoretically and experimentally. These results will greatly enhance the ability to design machines that can perform human-like tasks. Another portion of the research will look at controlling a robot with a passive knee (active damping but otherwise unactuated), analogous to walking with a modern prosthetic. Professor Grizzle is actively engaged in undergraduate and graduate student education. NSF support of this research proposal is enhancing the research and education infrastructure at the University of Michigan through the construction of a biped robot prototype. The robot affords experimental facilities and numerous projects for students. This research grant provides for the training of one PhD student, and a Research Experience for Undergraduates (REU) supplement to this grant will provide a meaningful research experience for two undergraduate students. Special attention is being paid to recruiting at least one of these students from an underrepresented group. Professor Grizzle is also more broadly sharing the excitement of a research career in engineering by making presentations on bipedal walking robots to undergraduate student groups, and high school students. On the basis of his research findings in biped robot locomotion control, Professor Grizzle is forging research relationships with colleagues in neurology and rehabilitation. His goal is to transfer the deeper understanding of bipedal posture and locomotion that is resulting from the study of robots, to the development of improved rehabilitation therapies for a class of patients who have suffered strokes or spinal cord injuries. The research findings of this grant are maintained on Professor Grizzle's web site; see above for the URL.