matching PWMs

[jrz126]

Im working on this project in my microcontrollers class that involves constructing a Lego tank robot that has 2 small unmatched motors.
The bot has to navigate obsticles and whatnot, and I have pretty much everything figured out except for how to get the PWM's matched to get the bot to go in a straight line.
I know this should be in the robotics section, but there isnt much activity over there and its due in a couple days.
so what would be the easiest way to do this?

 

[Nigel Goodwin]

Im working on this project in my microcontrollers class that involves constructing a Lego tank robot that has 2 small unmatched motors.
The bot has to navigate obsticles and whatnot, and I have pretty much everything figured out except for how to get the PWM's matched to get the bot to go in a straight line.
I know this should be in the robotics section, but there isnt much activity over there and its due in a couple days.
so what would be the easiest way to do this?

There's no way to do it accurately without some kind of feedback, even with perfectly matched motors the loads on them will be slightly different and it won't go straight. You need to measure the exact distance the wheels move, and keep them both the same - bear in mind though, this doesn't account for wheel slip, so it still might not go straight!.

Probably the simplest way is to use steppers rather than DC motors!.

 

[jrz126]

oh yeah, I forgot to mention that I have an opical encoder connected to the one side to give me a tachometer feedback.

I was using a long piece of network cable to power the bot while testing, maybe I'll just kepp the wire on there and give it slight adjustments by pulling on the wire.