3 Jan 2006 cschur   » (Master)

HI all,

Great progress this holiday weekend on the Geobot. We added the IS417 based infrared wheel encoder to one side of the tracked base. The rear "cog" has seven holes in it, an gives 2.7 inches per hole on the ground. I made up my own circuit boards for these cool parts, they not only provide the modulated drive source for the twin IR leds, they also filter the IR with a built in filter, and also only look for the 38khz frequency. What a killer part. Anyway, we took it out into the sun today, and with the sunlight shining right at the sensor, and I mean right ON it, it easily picked up the single LED trasmitter on the outside of the hub about 4 inche out. Next, we set the software to count to 45 spokes on the hub and stop. Thats 120 inches, and after 10 feet on hideously rocky ground, it stopped.

Here is my feel for outdoor robot odometry, two wheel odometric navigation is almost impossible unless the ground is pefectly and unrealisticly smooth. What you CAN do is get a single wheel to give you the approximate distance youve traveled, despite the rocks and bumps to get you close enough to your target (via compass navigation) to see it with your other sensors. We have base ball sized and larger rocks in our test course (my backyard) and there was no way we could get a dual wheel odometric system to give you some sort of x-y coordinate of where you were. So we are opting for a digital compass, and a cucam, to spot the target area, probably a orange cone, to start its distant work. Well, thats all for now, I will post some images soon of our IR setup on the wheel - er tank hub.


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