Wednesday, August 19, 2009

Optical Sensing of Elevator State

The two optical methods I had in mind for sensing the elevator's state were video analysis of the elevator display (using a web cam pointed at the display) or mounting eight photoresistors in a frame to surround the display. Since video analysis involves less work I decided to try that first. I made a test patch in PD with simulated elevator display images (see below). My first test was to see if "blob tracking" would be able to distinguish the various elevators states. Clearly, blob size alone will not do. The display images with the same number of segments (2 and 3, either up or down) have the exact same blob size. Vertical blob position values for those same images are indentical too. Fortunately there is sufficient difference in horizontal blob positions to distinguish the six floor states. Now we need to record video of the actual display in the elevator to confirm my simulation and note the dynamics. - Drew

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