omni-wheels

[Marvin]

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

[Joker94]

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.

[waltr]

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

[Asellith]

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