Society of Robots - Robot Forum
Mechanics and Construction => Mechanics and Construction => Topic started by: Digimas on September 07, 2011, 09:10:30 AM
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I'm trying to design a robot which uses either a segway style (automatic stabilization) or a tricycle design.
Can someone explain the advantage of a segway style robot, and why there seems to be more of them out there.
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Hi,
Can someone explain the advantage of a segway style robot, and why there seems to be more of them out there.
People don't build two wheelers for any advantage (over three wheelers), but for the technical challenge or for street cred.
A three wheeler takes a lot less to build and is statically stable, even if the third wheel is just a caster and a non-driven wheel.
I'd think that there's more three wheelers out there, but the two wheelers get most of the hype.
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Here're someone's thoughts on this -
http://www.geology.smu.edu/~dpa-www/robo/nbot/advantages.html (http://www.geology.smu.edu/~dpa-www/robo/nbot/advantages.html)
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One point that immediately comes to mind is turning in place... you can do that fine with 4 wheels (only in a box config?) and 2 side-by-side wheels, but not with 3-wheels (unless you're talking omni wheels/mechanum drive)
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Hi,
One point that immediately comes to mind is turning in place... you can do that fine with 4 wheels (only in a box config?) and 2 side-by-side wheels, but not with 3-wheels (unless you're talking omni wheels/mechanum drive)
I've never used an omni wheel (or any of their similars), but I've never had problems with turning a 3-wheel, as the single third wheel is on a caster and merely for balance.
Why do you think that a 3-wheel configuration can't turn on the spot?
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I assumed non-caster on the front (The word "tricycle" definitely put an image in my mind.), and then implicitly assumed limited range of motion with that front wheel, which was perhaps dumb (turning ~90° in either direction -> almost turn in place; turning about center of back axle rather than center of bot). I'm used to this sort (http://www.flickr.com/photos/umsolar/5635474840/#in/set-72157626533425198) of 3 wheel vehicle, which has horrible turning radius :D
(Then the definition of turning in place can be bantered about, too)
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I'm trying to design a robot which uses either a segway style (automatic stabilization) or a tricycle design.
Can someone explain the advantage of a segway style robot, and why there seems to be more of them out there.
As You know, segway type bots are dynamically balanced - that is the main advantage. In other terms - no matter type of terrain, it will always try to compensate for temporal instability. If built well it does not matter for Your bot if it goes on nicely leveled terrace, climbs steep hill or goes the same hill down - stability of the bot will always be the same.
Secondly, thing is that such a bot always turns around its geometrical center, hence 0g while turning.
Thirdly, no matter what load You put on Your robot (load that would not crush Your bot, or exceed motor capabilities), or how disbalanced load is, self-balancer will always find perfect balance and execute 0g turns.
Most important thing (for DIYers) is the excitement You get when robot stands straight ;D
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One point that immediately comes to mind is turning in place... you can do that fine with 4 wheels (only in a box config?) and 2 side-by-side wheels, but not with 3-wheels (unless you're talking omni wheels/mechanum drive)
Differential steer robots with 3-wheels turn in place. The 3rd wheel is just a caster
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Hi,
I assumed non-caster on the front (The word "tricycle" definitely put an image in my mind.),
Ah OK. The term "tricycle" is used for several drive configurations and really only tells about the number of wheels.
I'm used to this sort (http://www.flickr.com/photos/umsolar/5635474840/#in/set-72157626533425198) of 3 wheel vehicle, which has horrible turning radius :D
(Then the definition of turning in place can be bantered about, too)
Nice one ;D
Most racers that are build for going fast on a reasonably straight track are usually made with limiting steering abilities for obvious reasons - a drag racer that could turn on the spot would be dangerous for both driver and guilty bystanders.
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Hi,
As You know, segway type bots are dynamically balanced - that is the main advantage.
And their major downfall when they fall down ;)
In other terms - no matter type of terrain, it will always try to compensate for temporal instability. If built well it does not matter for Your bot if it goes on nicely leveled terrace, climbs steep hill or goes the same hill down - stability of the bot will always be the same.
I beg to differ!
On bumpy ice or mud covered roads, even the best algorithms cannot right it if when it slips - and when down, it stays down.
Secondly, thing is that such a bot always turns around its geometrical center, hence 0g while turning.
How does turning in place make a robot float/hover??
Thirdly, no matter what load You put on Your robot (load that would not crush Your bot, or exceed motor capabilities), or how disbalanced load is, self-balancer will always find perfect balance and execute 0g turns.
The more off balance, thestronger (and faster) motors are needed. It's not a magic formula and it spends power just standing still.
And it doesn't hover!
Most important thing (for DIYers) is the excitement You get when robot stands straight ;D
Yes, but don't put too expensive stuff on it - one day is slips or runs out of juice and slams into the pavement (Or go out on a ledge and continues - like it happened to the Segway boss).
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segways are seriously hard to build, although cooler.
if your robot isn't balanced, it whud have to constantly move to stay in the same place.
and i thing py 0g turns, they mean no balancing is needed, not floating. I personally think this is not true, if the robot isnt balanced.
1 idea whud to have 2 wheels higher than the robot, and have the robot hang down, although due to the wheel size you will need some slightly stronger servos. still, its a cool idea.
for other segways, some serious coding, balance, and bills will have to be done/paid.