Date of Award

Spring 2021

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Mechanical Engineering & Materials Science (ENAS)

First Advisor

Dollar, Aaron

Abstract

Controlling a complex upper limb prosthesis, akin to a healthy arm, is still an open challenge due to the inadequate number of inputs available to amputees. Designs have therefore largely focused on a limited number of controllable degrees of freedom, developing a complex hand and grasp functionality rather than the wrist. This thesis investigates joint coordination based on human demonstrations that aims to vastly simplify the controls of wrist, elbow-wrist, and shoulder-elbow wrist devices.The wide range of motions performed by the human arm during daily tasks makes it desirable to find representative subsets to reduce the dimensionality of these movements for a variety of applications, including the design and control of robotic and prosthetic devices. Here I present the results of an extensive human subjects study and two methods that were used to obtain representative categories of arm use that span naturalistic motions during activities of daily living. First, I sought to identify sets of prototypical upper-limb motions that are functions of a single variable, allowing, for instance, an entire prosthetic or robotic arm to be controlled with a single input from a user, along with a means to select between motions for different tasks. Second, I decouple the orientation from the location of the hand and analyze the hand location in three ways and orientation in three reference frames. Both of these analyses are an application of data driven approaches that reduce the wide range of hand and arm use to a smaller representative set. Together these provide insight into our arm usage in daily life and inform an implementation in prosthetic or robotic devices without the need for additional hardware. To demonstrate the control efficacy of prototypical arm motions in upper-limb prosthetic devices, I developed an immersive virtual reality environment where able-bodied participants tested out different devices and controls. I coined prototypical arm motion control as trajectory control, and I found that as device complexity increased from 3 DOF wrist to 4 DOF elbow-wrist and 7 DOF shoulder-elbow-wrist, it enables users to complete tasks faster with a more intuitive interface without additional body compensation, while featuring better movement cosmesis when compared to standard controls.

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