Feb 06, 2014

Webinar: An OpenSim Framework to Estimate Muscle Dynamics during Locomotion with Elastic Exoskeletons

Learn about different approaches for modeling the interaction of exoskeletons with the musculoskeletal system

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You can view a recording of this event here.

Learn more about the studies described in the webinar in the following articles:

• Farris DJ, Robertson BD, Sawicki GS, "Passive elastic exoskeletons reduce soleus muscle force but not work in human hopping". J Appl Physiol. Sep; 115(5): 579-85
• Farris DJ, Sawicki GS, "Linking the mechanics and energetics of hopping with passive elastic ankle exoskeletons". J Appl Physiol. Dec 15; 113(12): 1862-72.

More information is also available at the project website: https://simtk.org/home/ncsu_exo_hop/.

Details

Title: An OpenSim Framework to Estimate Muscle Dynamics during Locomotion with Elastic Exoskeletons

Speakers: Dr. Dominic Farris, The University of Queensland
Dr. Gregory Sawicki, North Carolina State University and UNC-Chapel Hill

Time: Thursday, February 6, 2014 at 2:00 p.m. Pacific Standard Time

Registration

The event is free, but registration is required. To register for the event, click here

Abstract

Engineering advances have ushered in a new class of biomechatronic machines, robotic exoskeletons that can be worn by humans to either enhance or restore locomotion performance. A key goal of our recent work is to incorporate these exoskeletal devices into a modeling and simulation framework to begin to address muscle-level responses to mechanical assistance. Ultimately we hope this approach will evolve into a design tool that engineers can use to fit and prescribe optimal device parameters (e.g., stiffness) that meet specific performance objectives.

We have used two modeling approaches to investigate a class of ankle exoskeletons we developed that uses elastic storage and return of energy in springs acting in parallel with the plantarflexor (PF) muscles in order to reduce the metabolic cost of locomotion. While it is clear that such devices help unload biological tissues, they may also cause side-effects and perturb the 'tuned' muscle-tendon interaction of PFs. To test the effects of our new device, we collected data from seven participants with and without elastic ankle exoskeletons. We also used OpenSim to simulate muscle-tendon dynamics and metabolic energy expenditure, to establish a more direct link between the two and found that exoskeleton assistance may lead to non-intuitive and potentially unfavorable shifts in muscle operating length and velocity, making force production less economical.

In this presentation, we will discuss:

• The utility and drawbacks of simple 'lumped' muscle-tendon models of ankle-driven hopping with exoskeletons
• Development and implementation of an OpenSim-based approach to simulating muscle dynamics with and without ankle exoskeletons
• Results from simulations of ankle muscle dynamics during hopping in elastic ankle exoskeletons