jicx:
CalinTamaian:
You could use 4 ultrasonic sensors ( one on top, one behind and one on each side). The ultrasonic sensors will report the distance to the first object. Depending on the readings you can triangulate the position. GPS works pretty much the same but at bigger scale.Thanks for your reply.
The precision of ultrasonic module is ideal. The concern is that the ultrasonic module is very directional, like the infrared sensor. Perhaps the ultrasonic module is wider than the infrared sensor. It is still necessary to have many in order to have the good accuracy, since the space is about 8m x 5m.
Maybe the only solution is RSSI with XBee? I am now wondering, if the Xbees can determine the position through Trilateration :Trilateration using RSSI - Networking, Protocols, and Devices - Arduino Forum
Any kinds of your information or experiences would be appreciated.
The ultrasonic sensors have way bigger angle than an IR LED for example. The high frequency ones ( above 200Khz ) do have low directivity ( 9 degrees or so), but the lower frequency ones (25-40 KHz ) have big angles. At above 2m from the sensor I would expect to cover at least 2m left and right from the sensor. ( a 25 degrees sensor detects an object at 1.5m outside his straight line ; I know for sure because this was an unforeseen project issue).
The speed on sound is however dependent on air humidity , heat and pressure. Without compensation you might get some errors but you should have 10 mm resolution either way..... Unless the atmosphere is really incendiary 