Alt-BEAM Archive
Message #04753
To: beam@sgiblab.sgi.com
From: Bob Shannon bshannon@tiac.net
Date: Mon, 21 Jun 1999 19:47:35 -0400
Subject: [alt-beam] Re: Feedback explained?
Ian Bernstein wrote:
> I know this is probably old news for some of you but I was just writing
> an e-mail to someone and suddenly started to understand motor feedback
> and how the walker can adapt....
Actually, this is a somewhat controversial topic! Feedback and adaptation
are not equal things.
> What happens if the motor encounters resistance is the voltage drops (?)
> and the .22 caps charge differently. On a CPU bot you say to the motor,
> "go to this point".
Thats a gross oversimplification, and generally wrong. Your actually
describing
a servo motor controller rather than anything relating to CPU's here.
A CPU based robot does not mean that the motors are all servo controlled at
all.
There is nothing that makes the motors on CPU based robots work any
differently
than on a BEAM design.
> On a BEAM walker you say turn this way for x amount
> of time (x also changes depending on the resistance of the motor - leg
> gets stuck, at angle, rock....) so the whole thing is constantly changing
> depending on the environment and terrain.Well I wonder if there's a was to
> 'amplify' the motor feedback so if a
> leg gets stuck it will drastically change the circuit?
Some people place low value resistors across the H bridge to increase the
feedback.
But what remains unclear is this simply feedback, or real adaptation? Also,
is it really benificial to the robot?
I think we all have a long way to go to understand feedback in a BEAM design.
Real adaptation should envolve a fundemental change in a walkers gait, just
like
in biological walkers. This is not what happens with the microcore based 2
motor
walker at all.
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