Society of Robots - Robot Forum
Mechanics and Construction => Mechanics and Construction => Topic started by: Marvin on March 08, 2010, 12:11:49 AM
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3 questions.
1. Are omni-wheels the most practical and cheapest way to add another pair of actuator(servo) driven wheels to a differential drive robot? (this means i'd have a 4wd robot)
2. Would the actuators on the extra pair of wheels (omni ones) use identical PWM signals as the front 2 differentially drive actuators (servos)
3. Where in Australia (online) can you buy omni-wheels or any pointers to where i might search for them?
sry my job makes me parenthesize too much(Cheers)
update, i found rotacaster.com.au though they don't appear to be suited to slippery terrains
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yay, another aussie. Unfortunately the 3 sites i know of in Australia dont have them and to have a few wheels shipped from over seas could cost you 20 bucks easy. I'll keep looking and there may be a place that i have missed some where.
If you added an extra 2 servos to a differential drive robot wouldn't it still be diff drive and not need omni wheels.(or have i understood wrong?)
If you did use a extra 2 servos i would imagine you would use the same pwm as for the original 2 as they are still a servo.
the most common use for a omni wheel is for differential drive robots with 2 motors. they are often used to replace castor's by using only 1 or if you want a sturdier platform you can use 2 like admins ERP. castor's would be a really cheap way to go but i to would much prefer to find some omni wheels.
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A four wheel differential drive does work without the need of Omni wheels. There is some wheel scrubbing in turns just like in the treaded vehicle (tank). Here's a link to some four wheel diff drive bots.
http://www.robotmarketplace.com/products/battlekits.html (http://www.robotmarketplace.com/products/battlekits.html)
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3 Wheels with onmi wheels work great. check out my tutorial on EXMod. He will eventually have true omnidirectional movement but right now I just drive with the front wheels and steer with the rear.
http://www.societyofrobots.com/member_tutorials/node/362 (http://www.societyofrobots.com/member_tutorials/node/362)