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Two, three or four with that sir?
Posted by Chris
on
Tuesday, March 31, 2009
It might sound like a stupid question, but in designing my first robot I've fallen at the first hurdle. I loved the look of the hexapod/spiderbot robots but thought this a little ambitious for my first effort, so decided to stick to a wheeled/tracked 'bot.
Wheels or tracks? Well, I've no plans on going off-roading, so tracks seem to add an unnecessary layer of complexity, so wheels it is. But how many?
Two is obviously simple, with a third, non-powered castor for stability. But more and more I like the look of the three wheeled omnibot.
Just think about that for a minute. Three wheels - arranged in a triangle.
At first, it seems like a stupid idea because two driven wheels will always be dragging the third wheel. And dragging equals resistance which equals extra (unnecessary) load on the motors which means shorter battery life. That is until you've seen how a transwheel works.
These clever little wheel has a series of rollers running perpendicular to the axle around the outside, allowing it to be moved in any direction as well as to provide drive like a "normal" wheel.
So you can have three wheels all at 60 degrees to each other and by changing the speed of rotation on each wheel, have a robot move in any direction without turning to face that direction. Some of the cool kids call it "strafing".
So should I have a simple two-wheeled robot, which is easy to understand and drive? Or a three-wheeled robot which would be incredibly cool but quite tricky to get working from a single microchip controller? The obvious answer is to go with a four-wheeled 'bot using the transwheels (also called omniwheels on some sites).
This would give the simple controlability of a two-wheeled 'bot and the super-cool factor of an omin-directional (three-wheeled) 'bot.
As ever it comes down to cost and complexity. Three driven wheels are obviously cheaper to implement than four, but the level of complexity increases.
A bit more research is needed, and will be posted here as and when time allows....
Wheels or tracks? Well, I've no plans on going off-roading, so tracks seem to add an unnecessary layer of complexity, so wheels it is. But how many?
Two is obviously simple, with a third, non-powered castor for stability. But more and more I like the look of the three wheeled omnibot.
Just think about that for a minute. Three wheels - arranged in a triangle.
At first, it seems like a stupid idea because two driven wheels will always be dragging the third wheel. And dragging equals resistance which equals extra (unnecessary) load on the motors which means shorter battery life. That is until you've seen how a transwheel works.
These clever little wheel has a series of rollers running perpendicular to the axle around the outside, allowing it to be moved in any direction as well as to provide drive like a "normal" wheel.
So you can have three wheels all at 60 degrees to each other and by changing the speed of rotation on each wheel, have a robot move in any direction without turning to face that direction. Some of the cool kids call it "strafing".
So should I have a simple two-wheeled robot, which is easy to understand and drive? Or a three-wheeled robot which would be incredibly cool but quite tricky to get working from a single microchip controller? The obvious answer is to go with a four-wheeled 'bot using the transwheels (also called omniwheels on some sites).
This would give the simple controlability of a two-wheeled 'bot and the super-cool factor of an omin-directional (three-wheeled) 'bot.
As ever it comes down to cost and complexity. Three driven wheels are obviously cheaper to implement than four, but the level of complexity increases.
A bit more research is needed, and will be posted here as and when time allows....
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