Alt-BEAM Archive
Message #03021
To: beam beam@corp.sgi.com
From: Richard Piotter richfile@rconnect.com
Date: Wed, 05 May 1999 23:38:07 -0500
Subject: [alt-beam] Re: Bicore head targeting?
Why necisarily have the head, wouldn't the influenced body act like a
walking head?
Wilf Rigter wrote:
>
> As discussed at the chat today here is a (new?) idea.
>
> With a phototropic BiCore head mounted on a uCore walker, the head should be
> free to turn towards a light target and send an error signal to influence
> the walker uCore to start turning toward the target. From some
> experimenting, I found that integrating both BiCore phase signals produces
> two average Vdc error signals proportional to each phase duty cycle. Since
> the duty cycle of each phase is complementary to the other phase, this
> produces two complementary error signals which can be applied to the two
> corresponding uCore bias points to lengthen the process in one Nv and
> shorten it in the other Nv, in effect causing the walker to turn. (ie <
> 50% = turn left, 50%= straight ahead, >50%=turn right) Given a relatively
> high oscillation frequency for the Head BiCore, it is simply a matter of
> connecting both BiCore outputs through 2 suitable resistors to the uCore
> bias points using the uCore caps themselves to integrate the average DC
> component of the BiCore outputs.
>
> The problem is that the head circuit stops sending out an error signal (50%
> duty cycle) when fully turned and locked on the light source. So once the
> head is turned into position: no more error signal and no more influence.
>
> Solution ? add a centering spring(s) between the head and the walker,
> tensioning the head to face to the front of the walker. Now when the head
> turns, the BiCore has to "work" to keep it turned towards the light and
> therefore keeps sending an error signal to the uCore until the head and
> walker both face straight towards the light. 8^)
>
> What do you think?
>
> <>
>
> Wilf Rigter mailto:wilf.rigter@powertech.bc.ca
> tel: (604)590-7493
> fax: (604)590-3411
>
> > -----Original Message-----
> > From: Dennison [SMTP:dennlill@buffnet.net]
> > Sent: Tuesday, April 27, 1999 12:01 PM
> > To: John A. deVries II; Sean Rigter; Wilf Rigter; van Zoelen, Bram
> > SSI-TSEA-352; Chiu-Yuan Fang; Dave Hrynkiw; Beam List (E-mail)
> > Subject: Bicore head targeting?
> >
> > I found out from dave that the controll system for his and Mark T's Heads
> > are not Bicores. They use some other "poppernets" or something like that
> > to control things. So that brings me back to bicores, how does one tell if
> > the bicore has 'targeted' something? You should be able to compare pulse
> > durrations, when the pulse durrations are equal in length you know that
> > the head has 'locked on' and is no longer in motion. But how to compare
> > these pulse's is the question. My first Idea was to connect both outputs
> > in some fashion to the +v or gnd side of a sizable cap. The idea goes
> > that, while one output charges the cap, the other output discarges. When
> > the pulse durations are equal, then in theory the average net change in
> > voltage across the cap should be zero. That would mean that at any other
> > point, when the avereage net change was a positive value, the head was
> > still in motion. I know it's confusing, but think about what would happen
> > if the cap was being charged and discharged.
> >
> > Dennison
>
> ------------------------------------------------------------------------
> Name: HEADWALKER.gif
> HEADWALKER.gif Type: GIF Image (image/gif)
> Encoding: base64
--
Richard Piotter
richfile@rconnect.com
The Richfiles Robotics & TI web page:
http://richfiles.calc.org
For the BEAM Robotics list:
BEAM Robotics Tek FAQ
http://people.ne.mediaone.net/bushbo/beam/FAQ.html
------------------------------------------------------------------------
eGroup home: http://www.eGroups.com/group/alt-beam
http://www.eGroups.com
- Simplifying group communications
Home