### Author Topic: Choosing motors for an arduino robot to compete in robocup jnr  (Read 1321 times)

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#### keyboard1333

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##### Choosing motors for an arduino robot to compete in robocup jnr
« on: October 03, 2012, 06:52:25 PM »
Hey Guys!
Me and a friend recently started plans to build a robot using an Arduino Uno to compete in the Australian Robocup Junior Soccer competion.

A friend who has competed in previous years, used 200rpm 12v 1.2A motors.
Do you think that that is enough power to move a robot weighing a couple of kilos rather quickly?
(Like half a meter a second)
If not, what are the specs for the kind of motor that we want?
Thanks, keyboard1333

#### newInRobotics

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##### Re: Choosing motors for an arduino robot to compete in robocup jnr
« Reply #1 on: October 04, 2012, 03:03:34 AM »
You didn't mention wheel diameter
"Computer games don't affect kids; I mean if Pac-Man affected us as kids, we'd all be running around in darkened rooms, munching magic pills and listening to repetitive electronic music." - Kristian W

#### keyboard1333

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##### Re: Choosing motors for an arduino robot to compete in robocup jnr
« Reply #2 on: October 04, 2012, 04:07:01 AM »
Between 1 & 2 inches.

#### newInRobotics

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##### Re: Choosing motors for an arduino robot to compete in robocup jnr
« Reply #3 on: October 04, 2012, 06:06:52 AM »
Then max velocity achievable (without taking friction into consideration) will be between ~0.27 m/s to ~0.53 m/s. It's clear that 1" wheels don't really cut it, hence let's go with 2" wheels.
• Circumference = Diameter * pi
• Velocity = Circumference * RPM

To have acceleration of 0.25 m/s2 (to be able to reach 0.5 m/s velocity in 2 seconds) each motor has to be capable of at least 63.5 mN*m torque.
• Force = Mass * Acceleration
• Torque = Radius * Force

You probably don't want to run motors at 100% duty cycle all the time, so to be on a safe side lets say that You want to achieve aforementioned results while running motors at 75% duty cycle. So, max motor RPM has to be at least ~252 RPM and stall torque has to be at least ~85 mN*m.

For what You want, something like 300 RPM 12V 0.39 N*m motor would be more that enough. Of course if plan on using 12V. What voltage are You planning to use?
« Last Edit: October 04, 2012, 08:01:31 AM by newInRobotics »
"Computer games don't affect kids; I mean if Pac-Man affected us as kids, we'd all be running around in darkened rooms, munching magic pills and listening to repetitive electronic music." - Kristian W