Well there has been a lot of interest lately with crab/synchro/swerve drives as of late which has inspired me to create one of my own.
This robot is able to drive in any direction while facing in any direction by both rotating and driving all four wheels.
For my version I decided to place the driving motors on the wheel modules. The disadvantage of this is that the wheel modules become very large making the overall robot large. But overall the advantages outweigh the disadvantage of size. Having the motors on the wheel modules greatly simplifies the gearing needed the power the wheels. With less gears needed the amount of backlash that is common in most LEGO inventions is negligible. Also by having the motors on the wheel modules leaves more room for the steering mechanism.
This picture shows a close up of two of the wheel modules:
There are two types of wheel modules used on the robot. There are two powered and two non-powered wheels modules.
Steering is acomplished by two motors located centrally on the robot. These two motors are geared together to power the steering for both the front and back wheel modules.
The following two pictures show the steering mechanism:
(Pictures were taken before the wheels were properly synchronized)
A video of this robot in action will be posted as soon as possible.
Please feel free to post any questions and comments.