View Single Post
  #8   Spotlight this post!  
Unread 18-01-2014, 12:45
raptaconehs raptaconehs is offline
Registered User
FRC #3200
 
Join Date: Dec 2013
Location: Colorado
Posts: 54
raptaconehs will become famous soon enoughraptaconehs will become famous soon enough
Re: Driving Straight Error

Quote:
Originally Posted by EricH View Post
I doubt it, but if you got something in there that was jostling just right, maybe.


I wonder... Check your speed controller output values in code. I'm thinking that maybe one of the motors might be getting an abnormally low value at full throttle, which would cause a draggy motor on that side. That would put the remaining motor working hard to overcome both the motor and the system...


Or maybe your joysticks need calibration.
Quote:
Originally Posted by orangemoore View Post
What if you write a simple autonomous program that has the robot drive straight forward. If it drives straight it is likely a controller problem, but if its pulling its likely the robot itself.
Just double checked, and in the videos posted, we were using a program that drove the motors at a set speed. This speed is read from the SmartDashboard.

Quote:
Originally Posted by Greg McKaskle View Post
Since you have encoders, can you plot them over time? I'd be curious how much difference there is under different conditions. In particular, how much difference is there when the robot is up on blocks? Does the half joystick and full joystick bias persist or does the behavior change?

Looking at the videos, in the half-speed one, the robot's acceleration is minor and the robot stays level. In the full-speed one, the robot accelerates hard. The weight rocks the robot on its back wheels, and that seems to be when it veers right. It doesn't look like a constant arc.

So another test would be to ramp the motor values more slowly. See if that sheds some light.

Greg McKaskle
We also did some more tests with the robot on the block. Using the same program, we ran the robot for ten seconds. After ten seconds, here are the encoder values:
Code:
Speed:  .5    Left encoder:  7282     Right Encoder:  7591
Speed:  .6    Left encoder: 11546     Right Encoder: 11435
Speed:  .7    Left encoder: 16531     Right Encoder: 17083
Speed:  .8    Left encoder: 20538     Right Encoder: 21263
Speed:  .9    Left encoder: 25814     Right Encoder: 26199
Speed: 1.0    Left encoder: 32812     Right Encoder: 33366