Abstract
Even with the help of modern prosthetic and orthotic devices, individuals with lower-limb amputation, neurological disorders, or orthopaedic disorders often struggle to walk in the home and community. Emerging powered prosthetic and orthotic devices could actively assist patients to enable greater mobility, but these devices are currently designed to produce a small set of pre-defined motions.
Finite state machines are typically used to switch controllers between discrete phases of the gait cycle, e.g., heel contact vs. toe contact, and between different tasks, e.g., uphill vs. downhill. However, this discrete methodology cannot continuously synchronise the robot’s motion to the timing or activity of the human user.
In this seminar, Robert will first present a continuous parameterization of human joint patterns based on 1) a phase variable that robustly represents the timing of the human gait cycle, and 2) task variables representing ground slope and walking speed.
This parameterization is employed for synchronised control of a new powered knee-ankle prosthesis, which enables above-knee amputee subjects to walk at variable speeds/inclines with reduced compensations of intact joints. This approach will also be extended to continuously-varying impedance control to provide more normative joint energetics. While these methods reproduce missing joint function, a different control philosophy is needed for exoskeletons that assist existing joint function.
Robert will also introduce an energetic control paradigm for back-drivable exoskeletons to alter the human body’s dynamics without prescribing joint kinematics, e.g., reducing the perceived weight and inertia of the limbs. This control approach is implemented on exoskeletons with high-torque, low-impedance actuators, which provide the necessary back-drivability to facilitate volitional human control.
About the Aerodynamics & Control Seminar Series
The Aerodynamics & Control Seminars, hosted by the Department of Aeronautics, are a series of talks by internationally renowned academics covering a broad range of topics in fluid mechanics, control, and the intersection of these two areas.