Alt-BEAM Archive
Message #00697
To: beam@corp.sgi.com
From: Steven Bolt sbolt@xs4all.nl
Date: Sat, 20 Feb 1999 21:10:42 +0100 (CET)
Subject: [alt-beam] Re: hmmm...i wonder which subject
On Sat, 20 Feb 1999, Terry Newton wrote:
> >It seems to me that a little uC can perform all relevant functions
> >of the microcore above - but why bother, and yes, it would be less
> >cool :)
>
> Oh, I'll bother, I do plan to make a uP walker but only for
> convenience, so I can try all sorts of different timings without
> building a bunch of stuff. I want to try coupled bicores and the
> Stills/Tilden arrangement where the microcore is saturated.
> Just to try, not to be cool, not to make it smart...
Will that be a 5-motor walker?
> I'm pretty sure your Spider a linear-drive robot, just not using
> wheels. Being linear, it should match very well with machine learning.
It's linear. `Gait' depends on left/right phase difference, is very
smooth with the legs geared as shown - each leg having a 180 degree
difference with its same-side neigbours - and a 90 degree
left/right difference. Turns can be on the spot or anyway you like,
but of course you can't maintain smooth phase while turning.
> How is the spider on rough terrain?
Rather good. It happily crosses my keyboard, despite the fact that
the too slender feet go deep between the keys. The usual desk
clutter is no trouble. In tall grass, it sort of `swims', still
making progress. But for/aft tilt should not exceed 15 degrees, or it
may flip on its back.
Do you offer the spider chassis in a kit? I'd love to get one.
I'm contemplating a kit including electronics, but that may not
make it; for best result, the all-up weight has to remain low,
indicating a thin pcb and SMT. The trouble with just a chassis
would be the small market and the need to offer the pcb material
parts cut out. Unless you're willing to have a go with a
fret-saw...
> >Hey! My three photovores all back up nice and dandy, and they
> >don't even have reversable motors.
>
> no offense... I meant an updated circuit for the classic-shaped
> photopopper with shaft-table drive pager motors. Something that
> looks like a little car... you know! robot-looking.
Looks are a matter of taste - I find my `Son of Photovore' rather
cute :)
> > Easier than you think, actually. No h-bridges required:
> >
> > Linkname: Photovore - search the light, avoid obstacles
Oops: http://www.xs4all.nl/~sbolt/e-fotovoor_beweging.html
(I have a mirror on my Linux-box, called Arlene)
---8<---
> I want to see a real reversible photopopper that can maneuver
> through tight spots and not get stuck. Like my picbot can, but in
> analog.
> I'm thinking glue a couple zetex smd h-bridge chips to the back of
> a stock photopopper along with a bit of logic powered by its own
> diode/cap so it'll stay hot through the complete discharge.
74HC logic does have the advantage of retaining state down to 0.5V
or even less. Using a SunEater_II kind of SE whith a sufficiently
high switch-off level, no extra cap is needed. I designed
SunEater_II with exactly this kind of `brain activity' in mind.
> Behavior would be if both feelers touch, or either feeler touches
> for too long (very simple learning?), switch the 1381 outs to the
> opposite motor reversing inputs with a 4053 or similar. Going the
> mod route it would have to be really small and efficient, smd all
> the way.
I'd be inclined to use my old `Willie' method:
(http://arlene.xs4all.nl/WWW/e-andere_robots.html#willie)
Hit on feeler, back up a little, turn 45 degrees towards the other
feeler, forward. A photovore could think in `steps' (charge / motor
burst cycles). X steps back, Y steps left or right only, forward.
Basically needs a counter and a little logic.
> Maybe even with a hardwired associative memory? Noam Rudnick's
> post was interesting, now I'm thinking about crossed inverters
> and stable states...
Have a go :)
Steve
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# sbolt@xs4all.nl # Steven Bolt # popular science monthly KIJK #
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