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|Lasers and Cameras and Lights, Oh My|
Groundhog's primary sensor is a scanning laser range finder. This sensor provides a 180 degree plane of range information about the surronding area. When displayed, this data can be used by a human to teleoperate the robot. When processed using the Carmen software developed at CMU, this data can be used to recreate a map of the mine and the path that Groundhog took in going through the mine.
In addition to a forward facing scanner, an upward facing scnaner provides information about the ceiling of the mine. This data is used to estimate the angle of Groundhog, and when combined with the 2D map can be used to generate a three dimensional map of the mine.Cameras
While not useful from a the robots perspective, the onboard cameras provided the human tele-operator with an idea of what they were going into, as well as a confirmation of the data acquired by the laser scanners.
The cameras also provided images from deep within the mine that no human would be capable of acquiring. With a little bit of additional tweaking, 1394 cameras will be included instead of the current analog cameras. This will enable the robot to autonomosly take and record digital images of the mine with out requiring anything more expensive than a 70 dollar consumer webcam.Lights
Lighting was required in order to prevent the cameras from producing only completely black images. The lights also served as a binary status indicator. If the lights went off, it meant that the main power relay had shutoff and something was likely wrong with the robot. In fact, throughout the development of Groundhog, the lights have served as a means of communicating. Initial experiments of wireless range were conducted by remotely flipping the lights on and off until the robot exceeded the range of the communcations link.
The lights used are 55 Watt, environmentally sealed halogens, one forward facing and one rearward facing, to match the two cameras.Oh, My
Some final additional sensors were necessary to insure Groundhog's safe operation. Dual gas sensors were mounted on the front of Groundhog in order to detect any dangerous levels of methane. Should either of these sensors register anything, Groundhog either backs up, or shutsdown, depending on the gas concentration.
The final sensor currently on Groundhog is a steering potentiometer used for recording and adjusting the steering angle of Groundhog in a closed loop fashion. However, most teleoperated steering has been bang-bang human control rather than anything more sophisticated.