The 8 degrees of freedom are achieved by combining a Unimation Puma arm (6 degrees of freedom) with a Directed Perception Pan/Tilt device (2 degrees of freedom). The pan/tilt device is mounted on the end of the Puma arm with a custom-built mount, and a CCD camera is mounted on the Pan/Tilt device. We are calibrating the device using a calibration plate, and following the procedure in the paper by Tsai and Lenz, "Overview of a Unified Calibration Trio for Robot Eye, Eye-to-Hand, and Hand Calibration using 3D Machine Vision."
The Directed Perception Pan/Tilt device gives us accuracy within 3 arc minutes, which allows us to precisely position the viewing angle, while it also gives us reasonable velocity and acceleration. It is controlled by hardware that automatically controls the acceleration curves, while allowing the programmer to set the velocity and acceleration parameters.
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