Subject:
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Re: Rack and Pinion Steering
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Newsgroups:
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lugnet.robotics
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Date:
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Wed, 3 Nov 1999 20:40:44 GMT
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Viewed:
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620 times
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In lugnet.robotics, lego-robotics@crynwr.com (The WordMeister) writes:
> [...] I'm working on a wheel-based 'bot that has rack-and-pinion steering,
> and I've run into a snag. [...]
>
> The goal is to [have] the steering assembly automatically recenter
> (or recenter with a small push in the opposite direction from the
> motor) when the turn is finished. [...]
>
> I'm having some problems [...] if the pulleys are strong enough to
> [steer] [...], they are too strong to allow the recentering to work
> well [and vice versa] [...]
I think you should look at a design in which each steering wheel's pivot axis
is NOT in the same plane as the steering wheel's axle. Specifically, each
wheel's axle should be behind its pivot axis, where "behind" is referenced in
terms of the intended direction of motion.
A caster is a good example of such a wheel design -- it requires no special
effort to make it "point" straight ahead. As long as the thing to which the
caster is attached is being pushed forwards, the caster automatically swivels
into alignment.
Automobiles and bicycles also implement a type of "passive centering" in which,
when you let go of the steering wheel, the forward motion of the car pushes the
wheels towards center. The bicycle's design relies entirely on weight (downward
force) and is notable because the pivot axis is not vertical. Automobile
designs are much more complicated (particularly when the steering wheels are
also drive wheels) and are probably not worth the effort.
- Robert Munafo
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Message has 1 Reply:
 | | RE: Rack and Pinion Steering
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| (...) <plant tongue in cheek> Bicycles also implement an "active buck" mode of Darwinian selection. If you ride your bicycle in hands-off mode and tilt the bicycle slightly by shifting your centre of gravity, the wheel will turn. Outside of the (...) (25 years ago, 3-Nov-99, to lugnet.robotics)
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Message is in Reply To:
| | Rack and Pinion Steering
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| Here's where I really miss not having a digital camera. I'm working on a wheel-based 'bot that has rack-and-pinion steering, and I've run into a snag. (I realize that dual-motor steering and a caster-type rear wheel makes more sense, but I wanted a (...) (25 years ago, 3-Nov-99, to lugnet.robotics)
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