Ordinary bikes and scooters are easy to keep balanced at
moderate and high forward speeds, but to stay upright at a
stoplight, or to move in reverse, the rider's feet must be
applied to the pavement.
The Mecanum Motorcycle (MM) is a self balancing vehicle
which is capable of moving both at
high speeds, very much
like a motorcycle or powered scooter, and at low speeds,
vaguely like a segway or hoverboard.
This is accomplished as follows: the rear wheel of the MM
is actually a pair of closely set, independently suspended,
mecanum wheels.
Each mecanum wheel has a separate motor.
The user's throttle controls overall forward (or rearward!)
acceleration of both motors.
A gyroscope, inclinometer, kalman filter, and pid controller
automatically control the difference in torque produced by
the two motors, in order to automatically balance the
vehicle around its roll axis. Note that this is in DIFFERENT
from other self-balancing vehicles, which balance around
their pitch axis.
If the bike is stationary, and the rider leans to the right,
the balancing system will automatically spin one of the
mecanum wheels forwards, and the other backwards, in
order to move the points of ground contact rightwards, to
keep the vehicle under the rider. As a side effect, this will
result in the vehicle yawing around the point where the
front wheel touches the ground.
Advantages:
Self balancing vehicles look cool.
The transition to feet down to feet up feels awkward,
imho, and this obviously eliminates that.
Not having to put your on the ground down means not
getting them wet/muddy/snowy in inclement weather.
Being able to steer by leaning, while not moving forwards
or backwards, makes it easier to back into a narrow
parking space (such as between other bikes).
Being able to motor backwards makes the above task
trivial.
Since the rider's feet never need to touch the ground until
he wants to get off, the entire bike could be bigger (taller)
than the typical limit of a motorcycle.
Disadvantages:
Mecanum wheels are expensive, have high unsprung
weight, and I haven't heard of any being built with
pneumatic tires. So, vibration.
Also, I'd worry about small objects getting caught in the
wheels.