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Author Topic: The Straight and Narrow  (Read 517 times)

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Offline ksquaredTopic starter

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The Straight and Narrow
« on: October 31, 2011, 09:21:24 AM »
My $50 dollar tutorial robot has issues going in a straight line.  (Not that it needs to in order to be a photovore.)  I believe the servos rotate at slightly different speeds even though I modifed them by taking out the potentiometer and soldering fixed 1% tolerance resistors in its place.  I used a 30 watt iron and a heatsink, could this have altered their resistance wtih too much heat?  Could I have hit something on the PCB in the servo itself?  I replaced the servo horns with wheels so they shouldn't be an issue. 

So, should I be able to get a robot to go on a line on a straight surface without feedback or is it relativly normal to have some issues with this?  Would it be easier to do this using an h-bridge and straight motors instead of servos or something?

PS: I'm using PWM (yes, I put some extra headers on the board to expose those microcontroller pins) rather than the timing loop provided in the tutorial. 

Offline newInRobotics

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Re: The Straight and Narrow
« Reply #1 on: October 31, 2011, 11:14:18 AM »
So, should I be able to get a robot to go on a line on a straight surface without feedback or is it relativly normal to have some issues with this?
It is totally normal as there is no feedback. If shaft encoder is not used, different motors will spin at different RPM. As PWM is used in Your case, You can hand tune PWM compare value so motors spin more alike.

Would it be easier to do this using an h-bridge and straight motors instead of servos or something?
That would not change a thing.
"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

 


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