"Body-In-The-Loop": Optimizing Device Parameters Using Measures of Instantaneous Energetic Cost

• DOI: 10.1371/journal.pone.0135342
• Publication Date: 2015-08-19T18:09:27Z
• Authors: Wyatt Felt; Jessica C. Selinger; J. Maxwell Donelan; C. David Remy
• Keywords: Maxima and minima; Metronome; Instantaneous phase

This paper demonstrates methods for the online optimization of assistive robotic devices such as powered prostheses, orthoses and exoskeletons. Our algorithms estimate value a physiological objective in real-time (with body "in-the-loop") use this information to identify optimal device parameters. To handle sensor data that are noisy dynamically delayed, we rely on combination dynamic estimation response surface identification. We evaluated three (Steady-State Cost Mapping, Instantaneous Gradient Search) with eight healthy human subjects. Steady-State Mapping is an established technique fits cubic polynomial averages steady-state measures at different parameter settings. The determined from fit. Using continuous sweep over range parameters taking into account measurement dynamics, identifies more quickly. Search uses similar iteratively approach using estimates local gradient. evaluate these simple repeatable way, prescribed step frequency via metronome optimized minimize metabolic energetic cost. allows comparison our results techniques enables others replicate methods. show all achieve accuracy estimating frequency. For methods, average error between predicted minima subjects' preferred frequencies was less than 1% standard deviation 4% 5%. were able reduce subject walking-time hour 10 minutes. While, single parameter, not much faster extends favorably multi-dimensional spaces.