Motor performance discrepancies

mhosmer

Hello,

I'm relatively new to robotics and have undertaken to build my first robot. I'm using the BS2, along with the PMWPAL and a home built h-bridge. I've finally reached the point where I'm experimenting with making my robot move around.

I used 2 identical motors and find that at 100% power both of my motor seem to run about the same speed but at lower speeds one motor will run faster than the other (of course this causes the robot to turn).

Is this normal for two identical motors? (perhaps I just have the motors misaligned)
What's the preferred method of resolving the discrepancy?
A lookup table for predefined speeds?
As it happens, I have motor spindle sensors and counters on the PMWPAL I suppose I could attempt to adjust the faster motor on the fly but if it did not adjust quickly I could imagine a fair amount of oscillation in the track.

Thanks,

Mark

kwinn

No two motors will ever run at exactly the same speed with the same applied voltage. Manufacturing tolerances will result in slight differences in the resistance of the wires and connections, the amount of friction in the bearings or bushings, clearance between the armature and stator etc. etc. To get them to run at the same speed you need a control system to compensate for these differences.