Robert Gregg - Enhancing human mobility with agile robotic prostheses and orthoses

Even with the help of modern prosthetic and orthotic devices, individuals with lower-limb amputation, age-related motor deficits, or orthopedic disorders often struggle to navigate the home and community. Emerging powered prosthetic and orthotic devices could actively assist individuals to enable greater mobility, but these devices are typically designed to produce a small set of pre-defined motions. Although the field is beginning to embrace controllers that unify phases of the gait cycle, these devices still switch between distinct controllers for different tasks, e.g., uphill vs. downhill. This discrete control paradigm cannot continuously synchronize the robot’s motion to the variable activities of the human user. This talk will first present a new paradigm for controlling powered prosthetic legs over continuous variations of walking and stairs (i.e., different speeds and inclines), as well as continuous transitions between sitting and standing. These adaptable mid-level controllers facilitate a small activity space for intent classification, enabling amputee users to control activity transitions through intuitive, heuristic rules with over 99% accuracy. While these methods reproduce missing joint function, a different control philosophy is needed for exoskeletons that assist existing joint function. The last part of this talk will introduce an energetic control paradigm for backdrivable exoskeletons to reduce muscular effort by providing a faction of the human torque, without requiring explicit knowledge of the activity. This task-agnostic control method enabled a bilateral knee exoskeleton to mitigate the effects of quadriceps fatigue in able-bodied individuals during repetitive lifting-lowering and carrying over 5 terrains, thus reducing their risk for injuries due to fatigue-induced compensations. The talk will conclude with preliminary results from studies using hip and knee exoskeletons to enhance the mobility of elderly individuals in real-world scenarios.