Abstract
Muscle Torque Generators (MTGs) have been developed as an alternative to muscle-force models, reducing the complexity of muscle-force models to a single torque at the joint. Current MTGs can only be applied to single Degree of Freedom (DOF) joints, leading to complications in modeling joints such as the shoulder. Therefore, this project aimed to develop, for the first time, an MTG model that accounts for the coupling between 2 DOF at the shoulder joint. Three different 2 DOF MTG equations were developed to evaluate the effect of the degree of coupling between DOF. Polynomial torque-angle scaling, torque-velocity scaling, and passive functions were defined for the different coupling equations, as well as the activation function. A completely general model, a female general model, a male general model, and 13 subject-specific models were fit for the three coupling methods. It was determined that the completely general model with position and velocity coupling resulted in the lowest error of 24.6%, with the position and velocity coupling for the female general model resulting in a similar error. The male general model resulted in higher errors, with position coupling showing the best results with an error of 32.9%. For subject-specific models, it was determined that the average error was also the lowest for position coupling with an error of 30.9% and increased with position and velocity coupling. The work demonstrated that subject-specific, completely general, female general, and male general MTG models can predict torque results that are dependent on multiple DOF of the shoulder.
Presenter
Sydney Bell, MASc candidate in Systems Design Engineering