Using navX MXP to get robot velocity

[Alan Anderson]

Originally Posted by slibert

The vibration part would seem to be managed by a very high framerate in the sensor, our previous experiments worked w/the ADNS3080 optical mouse sensor which had a 6400hz framerate if I recall correctly. What framerate were you using, and what was the general frequency of the vibration?

Frame rate wouldn't seem to be relevant. Our test system could track the carpet at more than 20 feet per second from about 2.5 cm, and at least 30 feet per second at 4-5 cm. The problem wasn't related to the speed of horizontal tracking, it was because the vertical distance between sensor and carpet was varying. Moving the sensor upward or downward by less than a millimeter, corresponding to about 2-4 percent of the separation, would throw off the distance measurements by about 5-10 percent. We thought about trying to mount the mouse much higher to make the error a lower percentage, but we didn't have the lenses available to get the focus to work.

The vibration on our test rig was induced by a 2004-vintage Thomas air compressor (we used a pneumatic linear actuator to move a strip of carpet a known distance), at I'd guess a few dozen Hertz. When we tried to use the sensors on an actual robot, the roughness of the wheels and the compliance of the carpet induced enough bounce and other vertical "noise" to make the readings nearly useless.