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UBC Theses and Dissertations

3D biomechanical simulation and control of the human hand Sachdeva, Prashant

Abstract

The goal of this thesis is to develop novel computational tools and software for detailed modelling of dynamics of biomechanical systems such as the human hand, with potential applications in prosthetics, surgery, robotics, and virtual reality. We study the effect of the finger extensor mechanism, and musculotendon control on the kinematic and dynamic function of the hand. Hand tendons form a complex network of sheaths, pulleys, and branches. A three dimensional model capturing its detailed anatomy would help simulate the coordination and internal dynamics of the musculoskeletal system. Previous approaches include resource-intensive cadaver studies and mathematical force-transmission models, which cannot compute hand motion under muscle action. We developed a modelling and control framework for hand musculotendon dynamics to overcome these limitations. This approach uses Eulerian-on-Lagrangian discretization of tendons with a selective quasistatic assumption, eliminating unnecessary degrees of freedom and the need for generic collision detection. Unlike previous approaches, our approach efficiently and accurately handles constrained musculotendon dynamics. Using this framework, two control approaches were developed for precise fingertip trajectory tracking. To apply these techniques, software tools were developed with goals of interactive design, experimentation, and control of hand biomechanics. They overcome limitations of other available biomechanics software, enabling modelling of complex tendon arrangements, such as the finger extensor assembly. These tools can simulate all musculoskeletal elements of the hand, and allow closed-loop simulation control. With these software tools, we built a detailed anatomical model of the lumbrical muscle of the finger and simulated its role in reshaping finger flexion. The lumbrical plays an important role in determining the flexion order for the interphalangeal and metacarpophalageal joints. Prior cadaver studies have recorded this role, providing an opportunity for model validation. The in vitro experiments were reproduced successfully, establishing its role in increasing the grasp reach of the hand. We also modelled the in vivo function of the activated lumbrical, overcoming the limitations of cadaver experiments. Finally, a preliminary model of the full hand was constructed with the thumb and the wrist, and simulations of tenodesis grasp and simple thumb motions are presented.

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Attribution-NonCommercial-NoDerivatives 4.0 International

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