Performance of the minnesota scanner: A prototype for 3-D tracking of moving body segments

An advanced method of tracking the three-dimensional motion of bodies has been developed. This system has the potential of dynamically characterizing robot motion and facilitating their end-point control. Three rotating planes of laser light, fixed and moving photovoltaic diode targets, and a pipe-lined architecture of analog and digital electronics are used to locate multiple targets whose number is only limited by available computer memory. Data collection rates are a function of the laser scan rotation speed and are currently selectable up to 480 hz. The tested performance on a preliminary prototype designed for 0.1 in accuracy (for tracking human motion) at a 480 hz data rate includes a resolution of 0.8 mm (0.03 inches), a repeatability of ± 0.635mm (± 0.025 inches), and an absolute accuracy of ± 2.0mm (± 0.08 inches) within an eight cubic meter volume with all results applicable at the 95% level of confidence along each coordinate direction. The system can be used to reduce XYZ target position data to body angular orientation for this first prototype ranges from ± 0.5 to ± 1 degree. Moving targets can be tracked at speeds exceeding 1 m/s with signal integrity tested but not limited to 25 hz motions.