Forward Neuromusculoskeletal Dynamics With Continuous Muscle Wrapping

Abstract

This paper investigates an explicit biomechanical framework to solve forward neuromusculoskeletal models (NMSMs), which includes muscle-tendon activation and contraction dynamics, musculoskeletal coupling, and multibody dynamics. The study addresses a novel muscle-wrapping method to compute the shortest muscle-tendon path using a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mathcal {C}^{1}$</tex-math></inline-formula> geodesic-based approach subject to tangency constraints, yielding an analytical formulation of muscle-tendon length and velocity, and a closed-form moment arm Jacobian matrix. A simple but representative upper limb NMSM was simulated under two conditions: (I) with no external wrench applied and (II) with a time-varying external wrench applied on the wrist simulating an interaction with a robot. For condition (I), our proposal was compared with OpenSim. Results from simulation under condition (I) show that the waveform of the analyzed parameters is similar to that obtained in OpenSim. Still, the proposed method yields overall improved results due to the analytical computation of muscle-tendon velocity and moment arm Jacobian matrix. Regarding the results under condition II, they show the reliability of the proposed modular NMSM framework to simulate human-robot interaction dynamics. Henceforth, our continuous wrapping-based NMSM proposal contributes as a baseline to model and study more representative forward NMSMs to assess human movement, including interaction with robots.