PT  - JOURNAL ARTICLE
AU  - Michael C. Rosenberg
AU  - Bora S. Banjanin
AU  - Samuel A. Burden
AU  - Katherine M. Steele
TI  - Predicting walking response to ankle exoskeletons using data-driven models
AID  - 10.1101/2020.06.18.105163
DP  - 2020 Jan 01
TA  - bioRxiv
PG  - 2020.06.18.105163
4099  - http://biorxiv.org/content/early/2020/09/21/2020.06.18.105163.short
4100  - http://biorxiv.org/content/early/2020/09/21/2020.06.18.105163.full
AB  - Despite recent innovations in exoskeleton design and control, predicting subject-specific impacts of exoskeletons on gait remains challenging. We evaluated the ability of three classes of subject-specific phase-varying models to predict kinematic and myoelectric responses to ankle exoskeletons during walking, without requiring prior knowledge of specific user characteristics. Each model – phase-varying (PV), linear phase-varying (LPV), and nonlinear phase-varying (NPV) – leveraged Floquet Theory to predict deviations from a nominal gait cycle due to exoskeleton torque, though the models differed in complexity and expected prediction accuracy. For twelve unimpaired adults walking with bilateral passive ankle exoskeletons, we predicted kinematics and muscle activity in response to three exoskeleton torque conditions. The LPV model’s predictions were more accurate than the PV model when predicting less than 12.5% of a stride in the future and explained 49–70% of the variance in hip, knee, and ankle kinematic responses to torque. The LPV model also predicted kinematic responses with similar accuracy to the more-complex NPV model. Myoelectric responses were challenging to predict with all models, explaining at most 10% of the variance in responses. This work highlights the potential of data-driven phase-varying models to predict complex subject-specific responses to ankle exoskeletons and inform device design and control.Competing Interest StatementThe authors have declared no competing interest.