Electronic – Infrared ranging

infraredrange-detector

I've been taking a look at these swarm robots and am very impressed. There is, however, one aspect of the robots I'm confused about, which is the infrared ranging they use.

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The robots have a wide angle infrared transceiver on their undersides, and bounce the beam off the table they stand on to communicate with other robots. This I can understand, but what I can't is the ranging part as stated above. Could someone shed some light on how these robots calculate their range from one another using this infrared method? A general explanation or links to an article would be most appreciated.

Best Answer

The answer is already present in the page whose link you posted:

From Technical Report TR-06-11, "B. Communication and Sensing", pg. 4

During any communication between robots, the receiving robot also measures the intensity of the incoming infrared light. This incoming light intensity is a monotonically de- creasing function of the distance between the transmitter and the receiver; therefore the distance to the transmitter can be calculated by the receiver. In practice, the incoming intensity of light is also affected by noise and manufacturing variances, which leads to sensing accuracy of ±2 mm, and precision under 1 mm.

(emphasis mine)

I suppose they experimentally found the relation between distance between Tx/Rx and received intensity (or have access to some characteristic graph from the manufacturer of the IR modules), and used that to base the distance calculations.

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