Subject:
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Re: robotic rovers
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Newsgroups:
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lugnet.robotics
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Date:
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Tue, 31 Aug 1999 00:13:29 GMT
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Original-From:
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alex wetmore <ALEX@PHRED.ORGspamless>
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Viewed:
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1932 times
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It sounds like you guys are trying to re-invent the adder/subtractor system.
Check out http://www.phred.org/~alex/lego for some designs using this.
In an adder/subtractor you have two motors, A and B. The wheels are then
run through a mechanical linkage such that one wheel has A+B, and the other
wheel has A-B. Then to go forward you turn on motor +A, with reverse
being -A. To spin left you turn on -B, and +B to go right.
The disadvantages compared to having direct motor control of your wheels is
that with direct control you get more power. The adder/subtractor looses
some power through the mechanical linkage, and starts with half the power
anyway because only one motor is used for forward motion (instead on a
direct drive system).
alex
----- Original Message -----
From: "David Chen" <nospam-dcchen@pacbell.net-nospam>
To: <lego-robotics@crynwr.com>
Sent: Monday, August 30, 1999 4:49 PM
Subject: Re: robotic rovers
> I wrote:
> > > I have also figured that if you connect the two motors to each other • (as
> > > well as to their respective outputs), you should lock in their • movements
> > > together. Perhaps you could run this thru a interrupter switch to shut
> > > off this connection while turning. • To which you wrote:
> > Well, I was with you up to this point... I don't understand exactly • what
> > you're suggesting here. • Then he wrote: (much more concisely)
> > I think what David meant with the phrase "lock in their movements • together" is
> > the incorporation of an electronic or mechanical device that will • connect the
> > respective wheel outputs so that the robot travels in an absolutely • straight
> > line...<snip>
>
> It could work in theory, but I just tested it again with 2 motors that
> were grossly mismatched. Having both motors interconnected
> (electrically) did NOT cause their respective torques to match up as I
> had hoped. I think the key would be in a mechanical lockup between the
> two axles.
>
> I had thought of one that could work, but haven't applied it yet. It
> goes like this:
>
> Given an AB steering system (ie. each side controlled by a separate
> motor).
>
> Wheel A <---- Motor A ----> Differential <(inverted)- Motor B ---->
> Wheel B
> ^
> Clutch (that can lock up this Differential)
> +-----Motor C
>
> 1) When going straight, the clutch is locked to the differential case
> preventing it from rotating and effectively locking A in step with B.
> 2) Before turning, dis-engage the Clutch with Motor C, now A and B turn
> independently.
> 3) Do your turn.
> 4) Re-engage the clutch before going straight.
> 5) Go straight.
>
> Sure it ties up an extra output, but you now have synched outputs at
> will.
>
> Eh?
> Dave
> --
> Did you check the web site first?: http://www.crynwr.com/lego-robotics
--
Did you check the web site first?: http://www.crynwr.com/lego-robotics
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Message has 2 Replies:
 | | Re: mechanical clutches
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| I agree that the adder/subtractor is the way to go (at least for now) if you want any semblance of accuracy in your robots - I even started the thread on what was the best design for the a/s (remember LDraw?) from which this branched out. (I hope (...) (27 years ago, 31-Aug-99, to lugnet.robotics)
| | | Re: robotic rovers
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| I had written: (...) Yeah, I suppose you are right. I think the only advantage to this scheme is that you can use a micro motor to power the clutch mechanism to that you don't tie up a full size motor. Also if you are running out of motor outputs, (...) (27 years ago, 2-Sep-99, to lugnet.robotics)
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Message is in Reply To:
| | Re: robotic rovers
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| (...) To which you wrote: (...) Then he wrote: (much more concisely) (...) It could work in theory, but I just tested it again with 2 motors that were grossly mismatched. Having both motors interconnected (electrically) did NOT cause their (...) (27 years ago, 30-Aug-99, to lugnet.robotics)
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