Delayed Output Feedback Control for Gait Assistance with a Robotic Hip Exoskeleton
Journal
IEEE TRANSACTIONS ON ROBOTICS
Date
2019.05.16
Abstract
We propose a new control strategy for gait assistance with a hip exoskeleton robot. This controller is based on the time-delayed self-feedback, which is known for stabilizing oscillatory systems under certain conditions. The controller does not have a gait phase estimator or recognizer that greatly affects assistance performance. We first define a state variable representing the current leg‘s movement with hip joint angles. A simple assistance control can be described in closed-loop form with the delayed state feedback. By assigning the appropriate time-delay and feedback gain, we can generate assistive torques stably under the interaction between human and exoskeleton. We validate the proposed method experimentally by measuring metabolic energy expenditure. The numerical study of the controller stability is also performed with simple pendulum models. The controller provides immediate and smooth assistance to user movement by reflecting the change of leg motion at every control cycle. The proposed delayed-feedback assistance controller also adapts to various gait speeds and environmental changes (e.g., stairs and ramps) without any additional sensors and computational processing.
Reference
IEEE Transactions on Robotics ( Volume: 35 , Issue: 4 , Aug. 2019 )