An Improved Model to Estimate Muscle-Tendon Mechanics and Energetics During Walking with a Passive Ankle Exoskeleton
One experiment has shown that wearing an elastic ankle exoskeleton can reduce the metabolic cost of walking by \(7.2\pm 2.6\%\), and the best exoskeleton stiffness is 180 Nm/rad. A model has evaluated the plantar flexor muscle-tendon mechanics and energetics during walking with this unpowered exoskeleton, but the optimal stiffness value is twice that of the experiment, so the simulated muscle-tendon mechanics and energetics may be somewhat biased. The purpose of this paper is to develop a model to match the simulation results to the experimental results and to better explore the muscle-tendon mechanics and energetics. The main improvements of this study are: (1) adding the modeling of dorsiflexor to match the work efficiency of plantar flexor and dorsiflexor, (2) analyzing the distribution of moments when the assistant moment is too large, and (3) updating the calculation process. By the improved model, the error of the optimal stiffness is reduced to 3.3%, and the error of the reduction rate of metabolic cost is reduced to nearly 0%.
KeywordsAnkle joint Human walking Muscle-tendon dynamics Metabolic energy cost Passive elastic exoskeleton
The authors would like to gratefully acknowledge the reviewers comments. This work is supported by National Natural Science Foundation of China (Grant Nos. U1713207), Science and Technology Planning Project of Guangdong Province (2017A010102005), Key Program of Guangzhou Technology Plan (Grant No. 201904020020).
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