XPost: alt.home.repair, alt.sci.physics, uk.d-i-y   
   From: steve@walker-family.me.uk   
      
   On 25/01/2019 09:09, NY wrote:   
   > "Steven"  wrote in message   
   > news:gav2ojFcs0sU1@mid.individual.net...   
   >> "NY"  wrote in message   
   >> news:Odqdnc3cerV429fBnZ2dnUU78UXNnZ2d@brightview.co.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   
      
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