Feedback Control Design for Bipedal Robots

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The motivation for studying walking robots arises from diverse sociological and commercialinterests, ranging from the desire to replace humans in hazardous occupations, to the restoration ofmotion in the disabled, the possibility of using legged locomotion in terrain that is unsuitable forwheeled locomotion, and the psychological appeal of machines that operate in anthropomorphic oranimal-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 offreedom in the mechanisms, the intermittent and unilateral nature of the contact conditions withthe environment, and underactuation. The most technologically advanced biped robots today arewalking on the basis of a heuristic control principle that imposes a flat-footed walking motion inorder to avoid dealing with the underactuation that comes with foot rotation (i.e., toe roll andheel strike). Professor Grizzle's research will develop the analytical foundations of walking with ananthropomorphic gait. By not relying on heuristics, significantly improved feedback controllers willbe designed that allow the natural rotation of the foot during the stance phase of walking, whilestill guaranteeing stability of the walking motion. Beyond a certain speed, walking is no longerefficient (or even possible). The extremely challenging problem of controlling a running motionof a bipedal robot will be investigated, both theoretically and experimentally. These results willgreatly enhance the ability to design machines that can perform human-like tasks. Another portionof the research will look at controlling a robot with a passive knee (active damping but otherwiseunactuated), analogous to walking with a modern prosthetic.Professor Grizzle is actively engaged in undergraduate and graduate student education. NSFsupport of this research proposal is enhancing the research and education infrastructure at theUniversity of Michigan through the construction of a biped robot prototype. The robot affordsexperimental facilities and numerous projects for students. This research grant provides for thetraining of one PhD student, and a Research Experience for Undergraduates (REU) supplement tothis grant will provide a meaningful research experience for two undergraduate students. Specialattention 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 engineeringby making presentations on bipedal walking robots to undergraduate student groups, and highschool students. On the basis of his research findings in biped robot locomotion control, ProfessorGrizzle is forging research relationships with colleagues in neurology and rehabilitation. His goalis to transfer the deeper understanding of bipedal posture and locomotion that is resulting fromthe study of robots, to the development of improved rehabilitation therapies for a class of patientswho have suffered strokes or spinal cord injuries.The research findings of this grant are maintained on Professor Grizzle's web site; see above forthe URL.