Our robots can never keep moving in straight line and always ends up going off course. When placed on the table, it would start off going straight then would veer off a bit causing it to hit the wall. We would use our hands to keep it in a straight path as it moves but, of course, we know it is not allowed in the competitions. We first thought the problem was the pivot wheels and tried 4 wheel robots but it still ends up going off course. Can anyone provide suggestions on how to keep the robot moving in a straight line?