Pluto uses a configuration of three individually driven and steered wheels to provide omnidirectional motion. We found for uneven floors however, that the combination did not work well. One of the wheels on each of the three pairs was removed and the side where the wheel was removed was grounded to the housing structure.
Pluto, after a short, but promising, career ended up in the Computer Musuem in Boston. At that time there was tremendous difficulty in controlling the six degrees of freedom in the wheel steer and drives with the 6805-based processors we designed at the time. Additionally, the onboard motor controllers were built and designed directly into the motors in the wheel housing. This was a complex undertaking and, again, proved problematic for operation, debugging and maintenance.