System to Apply Continuous Forces to People Walking; Early History of Optical Motion Capture

Walking requires energy. This required energy can be much greater energy among certain clinical populations, such as the elderly or those with cerebral palsey (CP). Individuals with CP typically expend several times more energy than their counterparts without CP. Assistive devices can increase mobility, but do not directly reduce the metabolic demand of walking, leading to faster exhaustion and reduced overall mobility. Previous studies have shown that linear forward assistive forces can reduce the metabolic demand of walking, but these studies have not yet been replicated in overground walking conditions. We designed and built a system that would provide forward assistive forces with a goal of producing consistent constant force. This system was designed with the goal of verifying these studies, as well as other computational models which showed similar results. Assistive forces were applied from this system to a single subject, whose walking was quantitatively measured using a Vicon optical motion capture system. Force application could not achieve desired consistency due to equipment limitations and inconsistencies in speed over the course of a subject’s gait cycle. Despite these limitations, significant changes in some gait cycle parameters were observed under some assistive force conditions, indicating that these forces do alter gait. While no metabolic metrics could be measured using this setup due to inability to achieve steady state walking, subjects did anecdotally note that walking felt easier, suggesting that forces of this nature could be a promising method for reducing metabolic demand of walking.
The STS research paper portion of this portfolio focuses on the history of optical motion capture, with a particular emphasis on social groups that contributed to its development and the social ramifications of its adoption. Optical motion capture is a technology that uses video cameras to track the motion of markers through three-dimensional space. This data can be used to create riggings of humans, which can be used to study motion or create artificial representations of realistic human motion for entertainment. This paper details a timeline of events surrounding the precursors to and early versions of optical motion capture. It also views optical motion capture from the perspective of medical scientists, artists and animators, animation studios, and device manufacturers to gain a better understanding of how this technology developed, and why it developed the way it did. In it, I will examine a number of sources, including conference documents, union agreements, scientific journals, and the works of historical scholars to better understand the complex social dynamics underlaying the development of this technology. I will argue that, while many of the first developments were in government and medical sectors, the major driving force behind modern optical motion capture was its use as a cost-saving measure for entertainment studios. This technology has grown rapidly over the last 20 years, but understanding the story of its development and the reasons for certain aspects of it can and should inform an understanding of its modern use and purposes.
These two projects are bridged by the presence of motion capture technology. Many modern biomechanics studies rely on motion capture, including the studies performed as part of our capstone. Vicon motion capture was used to track markers on subjects inside of the force application system. This tracking data was used to measure a variety of spatio-temporal parameters and examine what changes in gait were occurring as a result of force application. This has little direct relation to the history of optical motion capture and its development. However, responsible use of technology can involve an understanding of that technology’s history and development. In addition to aiding in responsible use, understanding of history can also lead to the discovery or rediscovery of tools and techniques that can improve results and enhance scientific research. While my research paper did focus more on entertainment, especially with regards to the film and television industry’s impact, medical scientists are still among the most important figures in this development, especially at the very beginning. As an engineer and medical scientist, it is appropriate for me to consider the use of motion capture and actions of motion capture companies, including but not limited to the actions of my predecessors in the biomechanics community.

School of Engineering and Applied Science

Bachelor of Science in Biomedical Engineering

Technical Advisor: Shawn Russell

STS Advisor: Joshua Earle

Technical Team Members: Thomas Brown, Janet Le