The effect of a lower-Body exoskeleton on physical and cognitive warfighter performance

Abstract

United States warfighters carry very heavy equipment into battle; robotic exoskeletons offer a promise to off-load the warfighter. While exoskeletons are currently evaluated for their effects on the user's physical performance, their cognitive effects are not currently considered in the literature. This study analyzed the performance of twelve military members in a simulated, fatigue-inducing patrol task under three conditions: wearing a powered exoskeleton (PWR), wearing an unpowered exoskeleton (UNP), and without wearing an exoskeleton (OFF). While walking with weight at a prescribed pace over obstacles while following a confederate, participants were subject to a dual-task cognitive test in which they answered radio calls and visually scanned for lighted targets. Cognitive load was varied through a secondary radio task and measured with a visual reaction time test and the radio task. Physical load was varied by switching between a light and heavy backpack. The primary objective of this study was to determine the effects of the exoskeleton on physical and cognitive performance. The secondary objective was to examine the interaction of the exoskeleton conditions with physical and cognitive loading settings. The dependent measures under consideration were visual hit/miss rate, visual reaction time, audio hit/miss rate, audio reaction time, incremental lag time, and NASA-TLX scores. Key findings were differences between exoskeleton conditions, loading settings, and the Subject*Condition interaction effect. Subjects did the best at the follow task with OFF, second-best with PWR, and third-best with UNP. Changes in cognitive performance were complex; in summary, interacting with the powered exoskeleton appeared to have a cognitive cost, but the mechanism creating this interference is unknown. The results also highlight the importance of the Subject*Condition interaction. The Subject*Condition interaction was a significant effect for visual reaction time, visual hit/miss rate and follow task metrics including incremental lag time variance. Understanding the interactions between subjects and exoskeleton usage will help inform exoskeleton development, operator selection, and use cases.