"TRANSLATIONAL CONTROL DESIGN FOR LOWER-LIMB PROSTHETICS AND ORTHOTICS: LESSONS FROM ROBOT LOCOMOTION"
Robert D. Gregg, Postdoctoral Fellow,
Center for Bionic Medicine Rehabilitation Institute of Chicago
This talk will discuss ongoing efforts at translating theoretical control approaches from robot walking into biomimetic control strategies for clinically viable wearable robots. Estimates indicate that by 2050 the U.S. will incur a two-fold increase in the incidence of stroke and amputation, due in large part to the prevalence of cardiovascular disease. High-performance prostheses and orthoses (i.e., exoskeletons) could significantly improve the quality of life for over 600,000 lower-limb amputees and 1.6 million stroke survivors in the U.S., whose ambulation is slower, more asymmetric, less stable, and requires more energy than able-bodied individuals.
Most wearable robots and autonomous humanoids to date rely on control strategies that track time-based reference trajectories, typically in the form of joint torques, kinematics (angles/velocities), or impedances (stiffness/viscosity). These trajectories are difficult to generalize across tasks, environments, and users, and this time-dependent control approach is not necessarily robust to external perturbations that push joint kinematics forward or backward in the gait cycle.
However, recent work in the field of dynamic walking has produced time-invariant, provably stabilizing strategies from feedback control theories such as energy shaping and virtual constraints. This talk will present the application of energy shaping to a powered ankle-foot orthosis that provides body-weight support during the stance cycle, followed by the application of virtual constraints to a powered prosthetic leg. In order to derive a biomimetic virtual constraint, this work attempts to address a fundamental gap in knowledge about how the human nervous system knows its location in the gait cycle (i.e., the biomechanical sense of phase). Future directions for the field will also be discussed, including neural feedback for subconscious control adaptation, wearable biomechanical sensors for feedback control, and clinical applications of spontaneous symmetry-breaking in human locomotion.
Robert D. Gregg received the B.S. in Electrical Engineering and Computer Sciences from the University of California, Berkeley in 2006. He received the M.S. in 2007 and Ph.D. in 2010 from the department of Electrical and Computer Engineering at the University of Illinois at Urbana-Champaign. Robert is now an Engineering into Medicine Postdoctoral Fellow in the Department of Mechanical Engineering, Northwestern University and the Center for Bionic Medicine, Rehabilitation Institute of Chicago.
His research is in the control mechanisms of bipedal locomotion with application to both autonomous and wearable robots, and his current work concerns the translation of robot control theories into biomimetic strategies for powered prosthetic legs. Robert received the Best Technical Paper Award of the 2011 International Conference on Climbing and Walking Robots, the 2009 O. Hugo Schuck Award from the IFAC American Automatic Control Council, and the Best Student Paper Award of the 2008 American Control Conference. Robert is a member of the IEEE Control Systems Society and Robotics & Automation Society, and he was co-chair of the 2010 Symposium on Control and Modeling of Biomedical Systems.