Inertial Musculotendons
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Date
2022-12-29
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Abstract
This thesis aims to develop a simple and practical framework for musculoskeletal simulation that accounts for the inertia of muscles.
Computer animation researchers have been using and extending muscle-driven skeletal simulations for many graphics applications. However, almost all musculoskeletal simulators used in graphics (and biomechanics) ignore the effect of the inertia of the muscles as they slide with respect to the bones. Instead, the mass of the muscles are “lumped” to the bones at the rest pose, and so the effect of the muscle inertia cannot be reflected in the dynamics of the system, even though around 40% of total body mass is from skeletal muscles. We present a novel framework for incorporating the effects of muscle inertia for all commonly used musculotendon path types, including those with multiple path points and wrapping surfaces. To maximize inter-operability with existing musculoskeletal simulators, we use the reduced coordinates of the articulated rigid body system representing the skeletal joints as the degrees of freedom. However, unlike existing musculoskeletal simulators, we take into account the inertia of the muscles as they slide with respect to the bones, by inserting mass points along the paths of the musculotendons. As the skeleton moves, these mass points move, since each musculotendon is assumed to be frictionless—the path moves such that its length is always at its local minimum. Our main technical contribution is the derivation of this mapping (i.e., Jacobian, plus its time derivative) from the skeletal motion to the muscle mass motion.
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Physical simulation, Computer graphics, Neural networks, Rigid body dynamics, Constraints, Biomechanics