On 25/01/2019 09:09, NY wrote:
"Steven" wrote in message
...
"NY" wrote in message
o.uk...
Let's say you're stood stationary and upright on it, not moving.
Now, you lose your balance a little and begin to fall over
backwards.* Your feet tilt backwards, the device senses this, and
moves backwards. You're now still over the device

Yes, but it can't move under the center of gravity while your feet
are still on it.

You've forgotten Newton 3: "for every action, there is an equal and
opposite reaction".

Nope.

It moves the wheels by the motor exerting a torque on them. This
causes an equal and opposite torque on the scooter-and-human,

Yes.

thus moving the person's C of G relative to the axle

Nope, because the tilt of the human doesn't change much.

Doesn't it? I've never really watched one in operation that closely.

until the C of G is once again directly over the axle.

Fraid not.

This is how it corrects for the person leaning too far forwards or
backwards.

No, it applies force, it doesn't shift the CoG.

If the person leans back, the sensors detect that the scooter is
tipping backwards, and rotates the wheels backwards, thus tipping the
person forwards.

By force, not by moving the CoG

You may well be right: by exerting a forward-twisting force it may
counteract the tendency of the person (whose C of G is still behind the
axle) to twist the platform backwards. I suppose the fact that it does
this allows the person then to move to adjust their own C of G once the
platform is stable again.

It simply moves the platform and the rider's feet back to below the CoG.
Hence rebalancing.

SteveW