Subject:
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Re: Machina Speculatrix Reproduction
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Newsgroups:
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lugnet.robotics
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Date:
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Tue, 2 Mar 1999 13:42:55 GMT
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Viewed:
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1121 times
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That's pretty interesting.
Actually I think the builder missed a genuine opportunity at an advancement. A
tri-cycle driving front end approach with 360 degree turn swivel allows the
entire robot roving control to be done with ONE motor. Use a large turntable,
like the ones used on Technic cranes and such, for stability and then run a
shaft through the opening in the center down to drive the rotated wheel.
With this approach you have 2 shafts, each one may be turned in one direction
only to accomplish full roving capabilities. This also solves the problem of
mounting a motor down on the fork and having to deal with reverse travel to keep
the electrical cable from getting caught up or pulled loose. Using any of the
direction splitter techniques we have seen around here you can use one drive
shaft to rotate the turntable 360 degrees or more, but always in the same
direction. Use the other drive shaft to always make the driver wheel go
"forward". Note that when the fork is turned 180 degrees this would cause
reverse travel for the robot.
Using one motor for propulsion and turning has the added limitation that you
cannot turn and roll at the same time. However, I suspect that most software is
written with these two activities handled in a sequential fashion anyhow. For
the turtle robot this would also free up the touch sensor dedicated to detecting
rotation over travel. I do recommend that a rotation sensor be used for the
steering feedback, although you could work something out clever there as well
but just not as accurate.
Dedicating one motor to propulsion allows the other motor in the basic
Mindstorms kit to be used for interesting arms and such. A tri-cycle based
single motor driven platform would make it easier to use additional outputs (1
or more other motors) for the can retrieving contest too. However, you could
lose some speed if you find yourself waiting for the front wheel to rotate 270
degrees to turn left 90, for instance.
Just an idea,
- Steve
Nick Taylor wrote:
> Great post! Thanks.
> - - - Nick - - -
>
> Michael Gasperi wrote:
> <snip>
> > Over fifty years ago W. Grey Walter started building three wheeled, turtle
> > like, mobile robotic vehicles.
> >
> > For more details please go to:
> > http://ourworld.compuserve.com/homepages/Michael_Gasperi/walter.htm
> --
> Did you check the web site first?: http://www.crynwr.com/lego-robotics
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Message has 1 Reply:
 | | Re: Machina Speculatrix Reproduction
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| From: Stephan B. Wessels <stephan.wessels@sdrc.com> (...) you (...) software is (...) For (...) detecting (...) the (...) well (...) If you read the article about this robot you can see that it did use forward and turning motion at the same time. (...) (26 years ago, 2-Mar-99, to lugnet.robotics)
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