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ME Faculty Candidate Seminar: Robert Gregg
WhenMonday, Dec 10, 2018, 3:30 – 4:30 p.m.
Campus locationStudent Union Building (HUB)
Campus room214
Event typesAcademics, Lectures/Seminars
Event sponsorsDepartment of Mechanical Engineering

From kinematic to energetic design and control of wearable robots for agile human locomotion
Robert D.Gregg, Ph.D.
Assistant Professor,Eugene McDermott Professor,Department of Bioengineering,
Department of Mechanical Engineering

ABSTRACT: Emerging robotic prostheses and orthoses can actively assist individuals with limb lossor stroke to achieve greater mobility, but current devices are limited to performing a small set of predefined motions. This talk will present three recent developments toward agile wearable robots: 1) user-synchronized kinematic control of powered prostheses, 2) optimal design of series elastic actuators for awide range of activities, and 3) design of partial-assist exoskeletons that control body energy rather thankinematics. Typically, finite state machines are used to switch controllers between discrete phases of thegait cycle and between different tasks, but this approach cannot continuously synchronize the robot’smotion to the timing or activity of the human user. This talk will first present a continuous parameterizationof human joint kinematics based on a phase variable that robustly represents the timing of the human gaitcycle and task variables representing ground slope and walking speed. This parameterization is employedfor user-synchronized control of a powered knee-ankle prosthesis, which enables above-knee amputeesubjects to walk at variable speeds/inclines with reduced compensations of intact joints. To fully leveragethis control approach, prosthetic legs must be designed to efficiently perform a wide range of activitieswhile satisfying actuator constraints. A convex optimization framework will be introduced for the design ofseries elastic actuators that utilize nonlinear elasticity to minimize energy consumption and extend therange of achievable tasks. While these methods reproduce missing joint function, a different design andcontrol philosophy is needed for exoskeletons that assist existing joint function. This talk will describe anenergetic control paradigm for exoskeletons to alter the human body’s dynamics without prescribing jointkinematics. This control approach requires highly backdrivable actuators to facilitate voluntary humanmotion, motivating its implementation in exoskeletons with quasi direct-drive actuators. Applications instroke, osteoarthritis, and elderly assist will be discussed.

SPEAKER BIO: Robert D. Gregg IV received the B.S. degree in electricalengineering and computer sciences from the University of California, Berkeley in 2006and the M.S. and Ph.D. degrees in electrical and computer engineering from theUniversity of Illinois at Urbana-Champaign in 2007 and 2010, respectively. He joinedthe Departments of Bioengineering and Mechanical Engineering at the University ofTexas at Dallas (UTD) as an Assistant Professor in June 2013 with an adjunctappointment at the UT Southwestern Medical Center. Prior to joining UTD, he was aResearch Scientist at the Rehabilitation Institute of Chicago and a Postdoctoral Fellowat Northwestern University. Dr. Gregg directs the Locomotor Control SystemsLaboratory, which conducts research on the control mechanisms of bipedallocomotion with applications to wearable and autonomous robots. He is a recipient ofthe Eugene McDermott Endowed Professorship, NSF CAREER Award, NIH Director’sNew Innovator Award, and Career Award at the Scientific Interface from theBurroughs Wellcome Fund. Dr. Gregg is a Senior Member of the IEEE.

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