[Al Skierkiewicz]

robiticxs,
What you describe is classic for four wheel drive systems as described above. What you don't see is the current drawn in this configuration. Current skyrockets as the drive motors consume near stall currents turning. Often the jerking occurs when the wheels finally break free of the carpet for a moment and then grab again. Omni wheels do correct this when added to the front or the back, not both, please. There are other solutions. Teams have put down a turning wheel that is at right angles to the drive wheels. When they want to turn, the additional wheel descends using pneumatics or some other power and lifts two of the wheels off the ground. A simple pneumatic cylinder with a caster wheel or nylon tip works almost as well.