Improving Human-Exoskeleton Fluency Through an Investigation of Dynamic Control Parameters

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Wearable robotic exoskeletons have potential to reduce workplace injuries by providing assistive forces that decrease the physical loads human workers experience. The goal of this project is to study the usability and user psychological comfort of an ankle exoskeleton during its interactions with its user. The device will be programmed to provide dynamic support as people walk and change walking speeds. The long term goals are to develop technology that infers and anticipates its user's intent, and to use that information to adapt the exoskeleton's behavior to maximize the user's trust in the exoskeletal system and the human-exoskeletal "fluency", defined as the synchronized meshing of actions within the human-technology team. Human-exoskeleton fluency results from the co-adaptation between the human and exoskeleton, driven by the motor strategies selected by the human when using the system and by the updates in the control policy based on the human. The goal of this project is to examine how uncertainty in the timing and presence of assistive force actuations impacts human-exoskeleton fluency and human trust in the exoskeletal system. This research will be impactful both for military applications, where high rates of musculoskeletal overuse injury threaten military readiness, and for industrial applications, where muscle strains, sprains, and tears cause about one third of the reported cases of lost work days. By integrating models of user intent, human trust, and human-exoskeleton fluency with the Dephy Bionic Boot, this project will advance the NSF mission to promote the progress of science and advance national health by exploring fundamental relationships human behavior, motor control, and machine manipulation within the context of exoskeletal gait assistance. The project supports K-5, undergraduate and graduate education through outreach, curriculum development, and mentorship.As a first step towards developing an anticipatory assistive exoskeleton controller that co-adapts with its human user, the specific objective of the proposed research is to test the hypotheses that human trust and human-exoskeleton fluency are affected by (1) assistive force transition timing and (2) early, late, or missed actuations within the gait cycle. This project has three aims. The first seeks to evaluate the effect of variations in assistive force transition timing on human-exoskeleton fluency. The second evaluates how uncertainty in the timing and presence of assistive force actuations impacts human performance and system trust. The third aim develops a co-adaptive controller that seeks to continuously increase fluency in real-time. The research team uses the commercially available Dephy Bionic Boot with custom control algorithms to permit hypothesis evaluation. The study will be performed within a CAREN virtual reality environment on a split-belt, instrumented treadmill that permits self-pacing. Subjects will perform speed changing tasks while also performing dual tasks and responding to questions designed to probe situation awareness. New measures of human-exoskeleton fluency and trust are analyzed. This work could lead to significant improvements in the adaptability, capability, and usability of wearable exoskeletal systems for human performance enhancement in industrial and military applications.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.