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Originally Posted by billbo911
Thanks. 
I really like how clean your assembly looks!
On sensors.... from my experience with the the Vex Ultrasonics.
They do a good job of sensing objects directly in front as long as object has a surface that is perpendicular to the sensor. In other words, when approaching a wall at an angle, the sensor wont pick it up very well at all.
Additionally, if you do put your bot in a box, the walls will bounce the 40KHz signal pulses quite a bit, causing misreadings from the controller.
Here's a thought. Try using the light sensors from the Line Following kit. With a little experimentation, you should be able to fine tune an algorithm to detect the relative distance from the wall based on the amount of light being reflected off of it. The biggest problem you will face with that is consistent light levels, and that may render this option useless. (Remember the difficulties with the CMU cam. and reflected light in 2005?)  |
Thanks, and thanks for the sensor feedback. I did consider Ultasonics, but couldn't hit on a scheme I thought would be reliable. Your info on the ultrasonics and performance at oblique angle confirms that I would have had a lot of problems. So- I'm using IR, very close proximity sensors, and a timing algorithm to detect differences in IR triggering in relation to angle of approach. I also have a mechanical switch backup plan- but I'd rather keep it clean with no real contact with the walls.
Thanks again for your reply. Billbo and Colin, your designs are both inspirational. Colin- I'll put your method of joining chassis parts with bearing blocks in my mental toolkit- I'm new to vex so I appreciate seeing new uses for the parts. It's amazing what can be done with, and learned from from, common creative constraints.
I'm glad I'm contending with 4-wheel math for holonomics rather than 3 though- much simpler. Thanks, trig.