Alt-BEAM Archive
Message #05785
To: alt-beam@egroups.com
From: michael.hirtle@ns.sympatico.ca (Michael Hirtle)
Date: Wed, 18 Aug 1999 21:52:59 -0300
Subject: [alt-beam] Re: Overcoming obstacles - an idea
sathe their is all ready a bot called the tumbler and it does the same thing
as u discribed
Sathe Dilip wrote:
> I was thinking on the following lines even before the contest
> (Innovative motion) was announced. Wilf's comments in an article last
> week prompted me to write about it. I hope someone finds it interesting
> enough to build a bot based on it.
>
> I will explain the general idea and leave the details to the builder. I
> do not know if someone has tried this before.
>
> The idea is to build a bot which combines some features of the
> photovore, (the miniball to some extent) and the walkers. I haven't
> built any yet but based on my understanding of how they work, photovores
> seem to have a problem negotiating stepped surfaces. Walkers can get
> around these to some extent.
>
> My idea is to use two motors (one on each side) and spokes in place of
> wheels. 4 wires/rods at 90 degrees each should do. Due to the torque
> needed to move the spokes/legs, we will need geared motors. The
> similarity to miniball comes from the way the motors/circuitry/power
> source is suspended from the legs. Unlike the walkers the legs turn
> full circles (like wheels). However due to the spacing between the end
> points (on circumference) where the legs can come to rest on a surface
> (unlike wheels), they should be able to negotiate the stepped surfaces
> better.
>
> At any given time, two legs on one side (and motor) of the bot will
> remain inactive while the other side pivots over one leg and advances.
> So the movement will be somewhat of a tumbling nature (may be we should
> call this guy TUMBLER?).
>
> A further development can be tried to make the robot more adaptive to
> its environment. The bot starts with a given leg length (shortest -
> just enough to clear its underbelly thus requiring less torque and power
> to move about). If it finds that it can not cross a step, it extends
> its legs (lehthens them - all 8 spokes at the same time for simplicity
> and balance). Then it again tries to cross the obstacle. The
> lengthening of legs could be a one step or multi-step process. It
> should be possible to achieve the lengthening/shortening of legs through
> the use of a third motor or a stepper mechanism (a relay with a dog
> wheel/rachet?) for activation. Actual lengthening can be achieved by
> either a rack & pinion mechanism or with two concentric rings and levers
> (think of the old Compur shutter mechanisms in some cameras- only inside
> out).
>
> I have attached a very bad graphic representation of the tumbler & how
> to implement the leg extension. I hope the 4K gif file is not
> objectionable. The leg shape shown, allows one to choose between a
> rolling and a tumbling gait. The claw shape might help in getting a
> good foot-hold on steps (especially when augmented by ribbed rubber
> boots).
>
> While writing this, I started thinking. May be for a future
> competition, we can collect new ideas. Then base the competition on
> building better bots based (I like the sound of that :-) on one or more
> chosen ideas. We can also have people collaborate so that people (like
> me) who do not find the time to build can work with someone who does or
> those with ideas needing special building skills/facilities can work
> with those who have access to such facilities.
>
> This is getting too long so I will stop. Thanks for reading. Let me
> know what you think.
>
> Dilip
> --
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>
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