Abstract
Exoskeletons and other wearable robotic devices have a wide range of potential applications, including assisting patients with walking pathologies, acting as tools for rehabilitation, and enhancing the capabilities of healthy humans. However, applying these devices effectively in a real-world setting can be challenging, as the optimal design features and control commands for an exoskeleton are highly dependent on the current user, task and environment. Consequently, robust metrics and methods for quantifying exoskeleton performance are required. This work presents an analysis of walking data collected for healthy subjects walking with an active pelvis exoskeleton over three assistance scenarios and five walking contexts. Spatial and temporal, kinematic, kinetic and other novel dynamic gait metrics were compared to identify which metrics exhibit desirable invariance properties, and so are good candidates for use as a stability metric over varying walking conditions. Additionally, using a model-based approach, the average metabolic power consumption was calculated for a subset of muscles crossing the hip, knee and ankle joints, and used to analyse how the energy-reducing properties of an exoskeleton are affected by changes in walking context. The results demonstrated that medio-lateral centre of pressure displacement and medio-lateral margin of stability exhibit strong invariance to changes in walking conditions. This suggests that these dynamic gait metrics are optimised in human gait and are potentially suitable metrics for optimising in an exoskeleton control paradigm. The effectiveness of the exoskeleton at reducing human energy expenditure was observed to increase when walking on an incline, where muscles aiding in hip flexion were assisted, but decrease when walking at a slow speed. These results underline the need for adaptive control algorithms for exoskeletons if they are to be used in varied environments.
Highlights
Exoskeletons are being used to great effect for the rehabilitation of people with lowerlimb pathologies (Dollar and Herr, 2008)
The use of exoskeletons in a real-world setting, e.g. to assist the elderly in everyday life, is made difficult by the number of variables to consider as a human walks in an uncontrolled environment — for example, walking speed, or whether the subject is walking on an incline
If exoskeletons are to become widely used devices outside of a clinical setting it is important that a suitable control paradigm is developed that, either implicitly or explicitly, applies assistance that accounts for these variables
Summary
Exoskeletons are being used to great effect for the rehabilitation of people with lowerlimb pathologies (Dollar and Herr, 2008). In a similar analysis to what is outlined above, the effect of different walking contexts and exoskeleton forces on healthy walking can be measured in terms of the metabolic energy consumed by the muscles of the subject This relationship could be optimised as part of a model-based exoskeleton control paradigm, alongside a stability metric, where the aim is to reduce total human energy expenditure or, alternatively, target specific groups of muscles for rehabilitation or assistance. Once known, this relationship can be used to inform how exoskeleton controllers are implemented for use in real-world settings where steady, flat walking is not guaranteed. Metabolic energy consumption was calculated and is reported for a subset of muscles crossing the hip, knee and ankle joints, and the effect of variations in walking context and exoskeleton assistance level on these representative muscles is discussed
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
