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A Data-Driven Approach to Estimate Human Center of Mass State During Perturbed Locomotion Using Simulated Wearable Sensors

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Center of mass (COM) state, specifically in a local reference frame (i.e., relative to center of pressure), is an important variable for controlling and quantifying bipedal locomotion. However, this metric is not easily attainable in real time during human locomotion experiments. This information could be valuable when controlling wearable robotic exoskeletons, specifically for stability augmentation where knowledge of COM state could enable step placement planners similar to bipedal robots. Here, we explored the ability of simulated wearable sensor-driven models to rapidly estimate COM state during steady state and perturbed walking, spanning delayed estimates (i.e., estimating past state) to anticipated estimates (i.e., estimating future state). We used various simulated inertial measurement unit (IMU) sensor configurations typically found on lower limb exoskeletons and a temporal convolutional network (TCN) model throughout this analysis. We found comparable COM estimation capabilities across hip, knee, and ankle exoskeleton sensor configurations, where device type did not significantly influence error. We also found that anticipating COM state during perturbations induced a significant increase in error proportional to anticipation time. Delaying COM state estimates significantly increased accuracy for velocity estimates but not position estimates. All tested conditions resulted in models with R2 > 0.85, with a majority resulting in R2 > 0.95, emphasizing the viability of this approach. Broadly, this preliminary work using simulated IMUs supports the efficacy of wearable sensor-driven deep learning approaches to provide real-time COM state estimates for lower limb exoskeleton control or other wearable sensor-based applications, such as mobile data collection or use in real-time biofeedback.

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The authors would like to thank Z. Centeno Sanz and V. Iyer for their help building the code for COP correction, P. Golyski and D. Espinal for their help with data collection, D. Molinaro for providing guidance on the TCN model, and E. Schonhaut for his assistance running models. This work was supported by National Science Foundation Research Traineeship: Accessibility, Rehabilitation, and Movement Science (NSF NRT ARMS) Program Award #1545287, National Science Foundation Graduate Research Fellowship Program (NSF GRFP) Award #1324585, the Georgia Institute of Technology Petit Institute Pruitt Scholarship, and NIH Director’s New Innovator Award DP2-HD111709.

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Correspondence to Jennifer K. Leestma.

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Leestma, J.K., Smith, C.R., Sawicki, G.S. et al. A Data-Driven Approach to Estimate Human Center of Mass State During Perturbed Locomotion Using Simulated Wearable Sensors. Ann Biomed Eng (2024).

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