Real-time Feedback in a Volumetric Display for Motor Learning Applications

Open Access
Miller, John Robert
Area of Honors:
Bachelor of Science
Document Type:
Thesis Supervisors:
  • Stephen Jacob Piazza, Thesis Supervisor
  • Keefe B Manning, Honors Advisor
  • volumetric display
  • motor learning
  • 3D
  • training
  • feedback
  • motion capture
  • real-time
The goal of this thesis is to develop a volumetric display for portraying human body motions in real-time. The results of three-dimensional motion analyses are typically displayed on a two-dimensional video screen. While such views may be rotated to give the appearance of a three dimensional motion, viewing a flat screen is inherently different from a truly three-dimensional display. A volumetric display would allow perception of the motion in three true dimensions and multiple observers could simultaneously view the same motion from different angles. Two different approaches to volumetric displays were explored, an LED display and a projected-light string display. The former is controlled by a microcontroller that is programmed to light a 3-D array of LEDs, and the latter involves projection of a two-dimensional image onto an array of vertical strings to create the three-dimensional image. Because it was less expensive to fabricate and easier to interface with the motion capture system, it was decided to move forward with the projected-light string display. Using a six camera Eagle Motion System, the coordinates of markers placed on human body segments were recorded and accessed in MATLAB in real-time. The marker data were used to calculate intersections between the body segments and the strings in the display. These intersections were represented as rectangles in a two-dimensional image projected onto the strings to create the three-dimensional image. Three applications were developed to demonstrate the capabilities of the display: (1) real-time posture assessment and training; (2) feedback of trunk lean angles during walking to lessen loads on painful joints; and (3) feedback of low back loads during a lifting task. Preliminary data collected during tests of these applications suggest that the use of the display conveys benefits to motor learning. To evaluate these effects more completely, further research is needed to compare the use of volumetric displays to other forms of feedback commonly used to enhance motor learning.