Let's Make Robots!

Walter Docking off of Compass and IR Beacon

Done. Done. Here is what I have learned. Compasses are great, just great --I am using a HMC6352 (because of a kind LMR brotha) and it simply puts out good clean data with very little flutter. HOWEVER... I have quickly discovered that these compasses do not like magnets --or to the point, they like them way too much! I had to remove my big-ass speakers from the room as the the big magnets on the woofers were throwing things off. With them removed and a quick calibration routine I am getting solid numbers each time. This leads to the second issue I had --My drive system is not quite as accurate as the compass numbers are. As many people know, Walter uses 2 DeWalt drill motors for locomotion through a chain-drive. The chains are not taught, nor should they be and this leaves a little slop in terms of what the encoders counted vs. how much the wheels actually turned. --I can loose or gain up to 4 counts when the motors stop and start --this can be almost 5% if you work it out. In addition, my encoders read actual marks on the wheels, not the motors so the count is done after the final gearing instead of counting the turns of the motors which would be a much more refined count. I have a total of 48 marks on the wheels which equals 96 edges or white/black "changes" so if I need to make a very small change, say one or two compass degrees, it can be sorta hard. Never the less, I have fudged everything, added "rechecks" to the code, and all-for-all I have a working proof of concept.

The video should explain it all.

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It’s good to see that your docking routine is coming along, but one thing puzzles me. What is this calibration of the compass that you are talking about? I have the exact same compass on Whirligig and it seems pretty accurate for my work at least. Is this more a calibration of your encoding system then the compass itself? Please elaborate.

Nice work Chris !

The IR sensor is just the standard 38khz 3-pin sensor --the same one everyone uses.

I will be using them soon on my next project. Already got some ideas.  I was reading about those a lot lately.

The one in the tube.

Looking good!

What are your charging posts going to look like? Do you plan to provide any kind of physical guides that will help align Walter in case he is 1-2 degrees off square? Or will you rely entirely on the compass and line following for alignment?

Congrats. Beware of the pieces of cake! I just wasted my weekend on just one!

Awesome result. Video makes it very clear now. The Voice is doing an incredible job. About turning on the line. Perhaps pivoting instead of spinning would work? Just fire left motor for 90 degrees of heading? That distance looks about the same as Walter's turn radius,