Quote:
|
Bob will explain this more elegantly than I can, but:
For the moment, ignore things like friction, wind, rolling resistance, air resistance, etc.
Forget about the windings. It's a question of energy. When the system (you and the Segway) are moving, the system has kinetic energy. To slow down, that energy has to go somewhere.
If you used conventional brakes, the energy would go into heat.
If you brake using a motor, and don't have a big resistor to heat up (or a space heater or whatever), then that energy goes into (charging) the batteries.
Similarly, if you are at the top of a hill, you have "potential energy". Getting you down the hill requires putting that energy into the batteries (converting it to stored energy). Getting you up the next hill reverses that process.
|
Okay. Lets take baby steps so that my limited understanding will not be overwhelmed.
I know that things in motion have a tendency to stay in motion, unless acted upon by another force. (If we continue to somewhat ignore things like friction, wind resistance, rolling resistance and the like, and roll them all toward a title I would call 'natural slow to a stop force'.
So, if you are rolling along and keep neutral, in other words, you do not motivate the segway to drive you forward, you will eventually stop.
However, if you want to stop sooner, you have to apply some energy into stopping...
Now, in a car, we have spoken of binder or friction brakes. But what has not been discussed is the mechanical or physical energy that goes into applying the friction to the brakes. Anyone with power brakes in an older car, who has tried to stop the car when the engine has stalled will know what I am speaking about.
Another example of a friction brake would be the hand brakes on a bicycle. Many of us have ridden, and know that our hand will get tired trying to slow down quickly at the bottom of a large hill. I have spoken in the past of a tandem Mountain bike that I have used in the past, with my wife behind me, a toddler in the trailer off the back, a baby in a bike seat on the handlebars, a large dog on either side on outriggers (dogs ran along either side). You can imagine that rig will roll down a hill and develop quite a bit of kinetic energy. To stop it with those bike brakes did generate some heat. But to keep the brakes on consumed a great deal of physical energy as well.
Now, with electrical brakes that apply force to counter act the kinetic energy that would keep the segway rolling for some distance, some energy must be consumed to enhance the natural forces that would stop the segway.
Again, to have a lot of speed, and stop it quickly, takes a larger opposing force, than to have that same speed and stop it slowly. (or more appropriately stated, the same force applied more quickly)
So, I wind up back at the 'things in motion have a tendency to stay in motion, unless acted upon by another force'. Does that other force not require energy?
I am not saying that the segway will not generate electrical energy as it slows down. What I am saying that to slow down quickly on command also consumes energy.