Mecanum Wheels Veering Left on Acceleration

So it’s probably a little late to be posting this as states are tomorrow for us but we’ve been having problems with our autonomous when we start the drive going forward. When we start the drive it turns left about 10 degrees and then goes straight in that direction. We didn’t have this problem until recently and we haven’t changed anything on the base. Right now we have the right motors going slower than the left in auton but it’s pretty janky and makes it inconsistant. Any ideas would be appreciated. Maybe some sort of smoothing function for the acceleration?

It could be a few things. You should check to make sure it’s not physical first though (e.g. too much friction on wheel, bad motor, bad ports on brain or motor, bad wire). I’m assuming you’ve changed out the battery as well, a drained battery can do some weird things lol.

I’d suggest pulling the axles out of the motors and seeing if they spin freely in your bearings. If you’re using a flat bearing, drill out the hole the axle goes through. If you’re using a pillow block, we’ve found that they should be attached with nylocks and left slightly loose.
Hope this helps and good luck tomorrow!

Our girls found last year that the way they coded contributed to a slight turn every time. For some reason the code was written to turn on both left side motors, then both right side motors.
motor[leftfront] = 100;
motor[leftrear] = 100;
motor[rightfront] = 100;
motor[rightrear] = 100;

after thinking about things, and looknig at the code, they made a change to
motor[leftfront] = motor[rightfront] = 100;
motor[leftrear] = motor[rightrear] = 100;

this helped.

something else that they noticed this year is that we have some drive train slop due to aged parts. The robot started erratically, sometimes going straight, sometimes, left a little, sometimes right a little. After setting the robot in place, they started pushing the robot forward then pulling it back so all the slop was always consistent. We can deal with consistent. Its the random crap that they had trouble with.

Hope that makes sense.

I wouldn’t have thought that it would have been that sensitive to order. There must have been more to the code than that.

Worn parts are an issue. Metal shafts in the plastic with cantilevered wheels are the worst. You can see the plastic worn away.

I wouldn’t have expeted it either. Mind you, it wasn’t a drastic difference but the robot always kicked one way when the motors started. a change in the code made it slightly more reliable and was easy to do.

We have a pretty strict budget, so most parts are reused. I think we are getting some slop from motor out to wheel.

I did try changing the order and it helped. It still starts a little wierd but it’s manageable. Happy to say the auton works now. Wish me luck at states tomorrow!

You can also do some stuff in code to completely eliminate this with either a gyro or tracking wheels. It’s actually quite simple to do.