Abstract: A mobile base for moving on a surface is provided having a driving and steering unit and a plurality of wheel assemblies. The driving and steering unit provides a drive force and a steering force. Each wheel assembly has a wheel assembly axis, and also has a steering column, concentric drive shafts, and two wheels. The concentric drive shafts respond to the drive shaft force, and provide a concentric drive shaft force. The steering column responds to the steering force, and provides a steering column force. The two wheels respond to the steering column force and rotate in the same direction for pivoting the steering column means about the wheel assembly axis. The two wheels respond to the concentric drive shaft force and rotate in the opposite directions to move the mobile base forwards or backwards along the surface.