[Aaron.Graeve]

Drive straight in what portion of the game? It is much easier in autonomous since you know what path the robot will be taking and can plan acordingly. Not so during teleop. Regarding the softaare side, a gyro would be your best bet, as it was designed to measure the heading of the robot. During auto, you can get away with just an encoder on each side of the drivetrain and work towards mathing speeds.

If you do not have any sensors, you can try applying a proportionally different power value to each side (e.g. after you get the final motor values from the joysticks,run the left motors at 80% and the right ones at 100%). You could try to figure out the function that each side of the drivetrain is following (speed of wheels based on motor value) and compensate that way. The function method would be the more complicated form of a simple power scaling factor, but an underlying issue exists.

Since you are trying to compensate for a mechanical problem in software, without a closed loop system (sensor and PID), the robot will only drive straight as long as the drive train does not change (including gear bindings or re-greaseing). You could get it "close enough", but it would be suseptable to the quality of repairs, the weather that day, and the mechanical sub-team. That doesn't sound fun does it.