Automatic Levelling Of A Prosthetic Wrist

• Author / Creator

  Brenneis, Dylan

• Upper limb amputation is a debilitating condition that affects over 41,000 people in the United States alone. Largely because of limitations in wrist prostheses, many people affected by upper limb amputation are compelled to use compensatory movements to perform tasks of daily living, which often result in overuse injuries in the back and shoulder. Some research has shown that adaptable wrists that either passively or actively adapt their angle without direct user input can reduce compensatory movements. The work presented in this thesis represents the first attempt to design and evaluate an active self-adjusting prosthetic wrist that relies only on its internal state to perform automatic levelling. The work follows the arc of the design process, first determining an appropriate user interface, then outlining the design of the prosthesis itself, and finally the evaluation of the effect of the device on the users. The first study provides evidence that an appropriate interface with a self-levelling wrist will keep the terminal device level any time the user is not directly controlling the wrist position. With this information, the design of the prosthesis and explanation of the automatically levelling system is outlined in detail. The system makes use of a single inertial measurement unit mounted in the base of the terminal device to perform all automatic levelling calculations. The second study, focusing on the effect of the device on users, suggests that the automatically levelling wrist may provide reduced compensation in shoulder flexion on a vertically-oriented task, but does not provide any compensatory benefit compared to conventional sequential-switching on a horizontally-oriented task. Further, users indicated that the automatically levelling system was less intuitive and less reliable to use compared to other control mechanisms. This thesis represents three main contributions to the field of wrist prosthesis research: an initial investigation of an appropriate control interface for automatic levelling, the development of a hardware prototype for testing with able-bodied people, and evaluation of effect of the system on users’ movement strategies and performance. By these contributions we show that an automatically levelling wrist may provide benefits by reducing compensatory movements in vertically-oriented tasks, but that the current implementation of automatic levelling suffers from limitations in terms of reliability and intuitiveness. Future research efforts should focus on increasing reliability, and on the evaluation of compensatory movements with prosthesis-users.

• Subjects / Keywords

  • Prosthesis
  • Automatic Levelling
  • Wrist
  • Compensatory Movement

• Graduation date

  Spring 2019

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-77sq-kd43

• License

  Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.