Alt-BEAM Archive
Message #11531
To: beam@sgiblab.sgi.com
From: "John A. deVries II" zozzles@lanl.gov
Date: Wed, 08 Mar 2000 16:02:34 -0700
Subject: [alt-beam] thrust and lift (was: Turning the walker)
if you took bigger steps with one foot that you did with the other, you'd
turn in circles, too.
a two motor walker generally uses one motor for "lift" and the other for
"thrust". the one motor lifts the robot allowing the thrust leg on that
side to be clear of the surface while that side of thrust leg is moving
forwards (remember, there aren't really two legs, really). of course, the
other "foot" of the thrust leg is on the surface during this time, pushing
the robot forward. wobble, thrust, wobble, thrust, and so forth. (ok, so
it is smoother than that )
to turn, instead of having the driving motor make equal swings (as a result
of equal timing) you make it so that the swing in one direction is longer
than the other. presuming, just for the sake of argument, that the longer
swing occurs when a thrust "foot" is on the surface, the robot will turn on
an axis away from that "foot's" side.
the tough part, really, is getting the swings to be equal so that the robot
walks forwards in a more-or-less straight line. if you can do that, you
use a light-sensitive (or whatever-sensitive) circuit to make the swings
NOT equal & if you've made it so that the longer thrust step is on the side
opposite from the light, the robot will turn towards the
light. conversely, if you've made it so that the longer thrust step is on
the same side as the light then the robot will turn away from the light.
Vehicles : Experiments in Synthetic Psychology by Valentino Braitenberg is
must reading for this topic.
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