[SML] lay out methods

[Joe D]

While I don't have any real-world ideas to share, I have imagined a few automatic methods, but have never heard of them being done.

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the 1st, is the idea of a Roomba-like device (or actual Roomba), with a marker installed, and a solenoid to lower the marker.  The robot would need a way to accurately navigate. And before anyone suggests it, counting revolutions of the wheel are NOT anywhere near accurate enough.

Such a device would require some sort of absolute positioning system. Some years ago, I started on a project to design a navigation sytem base on a fixed laser on a Roomba, and some retro-reflective targets. The idea is that if you know the locations of 3 reflectors, and then measure the angle between them, you can calculate your position.  I did some initial proof of concept, but then realized the laser really needs to continuously navigate with a rotating laser and even then cannot measure while moving. Though the idea may still be viable, if you use wheel encoding to get to a point, and then use the laser to fine tune the final point. E-mail me privately if you want to know more.
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Another idea is to simply computerize a pair of lasers.  If a compute can rotate a pair of laser line generators, then it can position them to the correct position for a  particular point.  I calculate that to permit 1/4" accuracy, such a positioning system would need 0.0298 Deg of accuracy. 

One source (OMC-stepperonline.com) has a stepper/gearmotor item: #0259 for $33, with 0.018 Deg step angle, but the gear box has a backlash that is <1 Deg.  Perhaps if the angle of the output were always approached from one direction, it would be acceptable. Their motor controller for it, capable of 128 micro-steps, #0245 is only $20.

So, I think the motorized laser idea is quite viable.
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Since there are numerous colleges represented on this list, I imagine one of these ideas would make a great student project.  Direct them to me, if they might like more information on either of these ideas.

Joe Dunfee
jdunfee12 at yahoo.com