Evaluation of a 3-dimensional inertial tracking system for quantifying human movement

The purpose of this study was to evaluate an inertial tracking unit (ITU) by comparing it to an optical tracking system. The ITU was attached to a bowling ball along with reflective markers for the optical system. Each trial started with the ball at rest on a pedestal the ball was then hung from a steel cable 10 feet long and set in motion in an elliptical pattern for approximately 25 seconds. The ball was then removed from the cable and returned to the pedestal so as to end each trial at rest. This was repeated 10 times with 5 trials chosen for analysis. A 10 second section starting with the ball at rest was taken from each data set for analysis. Maximum and minimum values for position and acceleration were compared between the two systems. Correlation coefficient and Root Mean Square were calculated for position and acceleration between the two systems. Maximum and minimum displacements in the Z plane were different between the two systems, while maximum acceleration in the Y plane and maximum and minimum acceleration in the Z plane were different. Only acceleration in the Z plane was strongly correlated between the two systems. As configured for this experiment the ITU did not reliably track the same motion as the optical system most likely due to slight misalignment of the gyroscopes.