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Originally Posted by Josh Siegel
On an unrelated topic, has anyone worked on large scale ackerman steering with PID threads? My high traction wheels are causing some trouble for the servo motors (a modified 18V drill), and was wondering what you might suggest. The total vehicle will weigh about 200lbs, I think.
Thanks!
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Team 95 attempted a 4 wheel drive crab drive that could do ackerman steering.
It turned out to be a mess. I think we faced the same problem. It was difficult to account for the friction of the wheel against the carpet in the steering motors programing. Basically, we could never get the ramp up and ramp down curves right, so the wheels would over or under shoot their target positions. We got close, but had to forever tweak them, and only really got it to work on a cement floor. Compounding that problem where the poor pots we used. They tended to drift and developed big dead bands at seemingly random points along their range. It was maddening.
The other big problem we had was getting all the trig to work on the BASIC stamp. I couldn't even begin to explain all the hoops that had to be jumped though to do a lot of trig with out the required trig commands. Suffice to say that after all was said and done the stamp was running at a crawl and there was no programming space left.
My suggestion is to gear the servo motors way down and reduce youre overall speed. At high speed I think you will just have to much stuff moving with to much momentum for the computing side of the bot to keep up. The lower ratios will help your servos 'sneak up' on the target position.
I can try to get a hold of that robots programmer if you like. It's a been a while though...
I've also looked for a laser range finder suitible for a robot. I wanted about a 500 ft range on a single target. It turns out that kind of equipment is very, very expensive. If you happen to find something better, please, let us know about it!
-Andy A.
Edit- fixed a few of many spelling errors, I'm sure.