01-12-2014, 11:53 AM | #21 |
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Bob,
I am sure you are right, but in an effort to understand, I will impose upon your imposing intellect to ask a question... I was under the impression that the segway motors had several sets of windings, therefore making them essentially several different motors in one housing. I was further under the impression that the different windings could do different things at the same time, and this is how, by having some inputs slightly out of phase with each other, the motor could both speed up the forward speed of the base, and also push back on the lean steer assembly. In essence, these motors can go forward and reverse at the same time. (or one motor in the housing is going forward, and another motor in the housing going in reverse at essentially the same time, in the same housing) I have a teen aged son, so I am surely familiar with conflicting signals from one entity. My thought was that the windings that were consuming power to slow down, were consuming more than the windings that were generating power by the slow down... So, Bob, please tell me all the mistakes in my scenario.
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Karl Ian Sagal To view links or images in signatures your post count must be 5 or greater. You currently have 0 posts. "Well done is better than well said." (Ben Franklin) Bene factum melior bene dictum Proud past President of SEG America and member of the First Premier Segway Enthusiasts Group and subsequent ones as well. |
01-12-2014, 12:25 PM | #22 | |
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Each motor does have two separate windings, and each winding is connected to one of the two control boards. From that standpoint you could say that there are two motors in one housing. Of course each motor has only one armature, but it can be turned by either or (normally) both controller boards.
If I understood Doug Field's description correctly, when the Segway forces you to slow down by leaning you backward, it's speeding up the motors to put the base out in front of your COG, but not so much that it can't recover as you lean back to comply. Quote:
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01-12-2014, 12:55 PM | #23 | |
Glides a lot, talks more...
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Quote:
I had also thought there were more windings more like a stepper motor. Two sets, but far more than 2 windings. Of course, it could be more easily explained by momentary increases in speed, to give the feel of push back at the handlebar, but then a reduction in speed of the overall unit... Kind of the same, but in this scenario, the yang comes before the ying. Of course, I may easily have the whole concept wrong...
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Karl Ian Sagal To view links or images in signatures your post count must be 5 or greater. You currently have 0 posts. "Well done is better than well said." (Ben Franklin) Bene factum melior bene dictum Proud past President of SEG America and member of the First Premier Segway Enthusiasts Group and subsequent ones as well. Last edited by KSagal; 01-12-2014 at 01:09 PM.. |
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01-12-2014, 01:43 PM | #24 |
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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. |
01-12-2014, 03:22 PM | #25 | |
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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.
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Karl Ian Sagal To view links or images in signatures your post count must be 5 or greater. You currently have 0 posts. "Well done is better than well said." (Ben Franklin) Bene factum melior bene dictum Proud past President of SEG America and member of the First Premier Segway Enthusiasts Group and subsequent ones as well. Last edited by KSagal; 01-12-2014 at 03:33 PM.. |
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01-12-2014, 04:15 PM | #26 | |
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Quote:
The answer is "no, force does not require any specific amount of energy. Consider the energy required to drop in a pin in a slot to lock the wheels. It can be trivial." Your experience confuses force and energy, and is based on how old brakes were designed (not very well), and not any real physical requirement. It takes no energy to just apply a force. Energy is force TIMES DISTANCE. That is, you keep applying that force as you move something (or you are moved) through a distance. But to apply a force over zero distance consumes (and produces) zero energy. Our muscles are inefficient, they tell us otherwise because they waste energy when generating a force. I'll come back to that when I get a chance to explain the overall picture more.
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Bob Kerns: To view links or images in signatures your post count must be 5 or greater. You currently have 0 posts. , To view links or images in signatures your post count must be 5 or greater. You currently have 0 posts. Obviously, we can't have infinite voltage, or the universe would tear itself to shreds, and we wouldn't be discussing Segways. |
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01-16-2014, 06:52 AM | #27 | |
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I'd like to draw a few pictures to make the physics a bit more clear. It all ties together in a tidy bundle of interrelated but consistent pieces.
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Bob Kerns: To view links or images in signatures your post count must be 5 or greater. You currently have 0 posts. , To view links or images in signatures your post count must be 5 or greater. You currently have 0 posts. Obviously, we can't have infinite voltage, or the universe would tear itself to shreds, and we wouldn't be discussing Segways. |
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01-22-2014, 03:35 PM | #28 |
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Sorry I didn't reply sooner but I could not get this forum software to let me sign in again despite multiple password resets, so this is the same person who posted the original message but on a different account... Thank you everyone for your responses.
I did figure out what this problem is - with help from my local (Oakland, CA) Segway dealer, who relayed advice to me from none other than Steve Wozniak of Apple fame, who apparently glides down a big hill in Los Gatos regularly and has a similar issue. Apparently, if you go down a big (as in 700 feet high) hill with a full battery charge, the regenerative breaking will eventually cause the battery to overheat. So Mr. Segway tries to slow you down, more and more, and basically tries to stop you from going down hill. Not realizing why this was happening, I kept urging Mr. Segway forward, and Mr. Segway said backwards only. So I turned around, started going up hill for about 10 feet, then turned around and started going down hill. That's when Mr. Segway actively pitched me forward downhill with a frowny face. The work around: Drain your battery a bit before going down hill. Or, periodically stop going down hill, and turn around and go up hill to burn off some charge. Since I started doing this, I've had no problems. I can reproduce the original problem by going down the big hill with a full charge. I think this is somewhat of a design flaw, in my humble opinion. I want to point out that I believe I have excellent Segway balance skills, routinely go up and down very steep hills, over modest bumps, turn around on steep grades, and so on and have never had a balance problem. So I don't think it's my inability to balance the Segway. |
01-22-2014, 05:35 PM | #29 |
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I have this same problem my house is on the top of a very high hill. Like you I have found the only way to safely get down the hill is to go even higher first. I don't think it's a design flaw, the energy has to go somewhere and since the batteries are full I prefer the stick-shake and shut down to the unit catching on fire
Have fun gliding! jeff
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01-22-2014, 05:43 PM | #30 |
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I find this interesting. Apparently segway owners who live in a small valley have an advantage to those who live on hill tops.
From full charge to glide out of the valley, there is no problem, and coming home, you are charging more, and consuming less, so you always get home. From a full charge to glide off your hill, you have to waste some energy before gliding down off the hill, but you consume greater amounts of power to get home, and potentially need the power you wasted. Top this all off with the fact that Dean Kamen lives on top of a hill! How weird is that? I believe he lives on the tallest point between Manchester NH and Boston, and has line of site to each. I wonder if he has a secret trip for gliding off his hill from home... By the way, I keep my segway in the cellar, but I access it thru my garage, which is under my house. So, within 50 feet of unplugging my ride, I have to glide up my driveway, and I live on a cul de sak, but the road it is on has a small hill, UP to get to the main road. So, I guess I do live in a small valley. Yeah me!
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