Dyson V6 Operating Manual page 26

Fixed wheels
are not designed
to turn corners
Wheels
A ball can turn •
on the spot
Ball
All change
Another problem to solve: normal upright vacuum
cleaners have fixed wheels, running on a fixed axle.
They move in straight lines. Like a push mower.
A Dyson Ball™ machine is different. It rides on a
ball, pivoting on a single point, allowing it to go
in any direction.