Alt-BEAM Archive
Message #03213
To: beam@corp.sgi.com
From: Wouter Brok w.j.m.brok@stud.tue.nl
Date: Wed, 12 May 1999 07:54:14 +0200
Subject: [alt-beam] Re: Inertial Rotation
Hello Dennison,
>Well, I was a little skeptical about how well this device could actually
>point twards light, but after building a prototype, I'll admit I am
>surprised how well the device works. It does point itself twards the light.
Very nice; good to hear!!
>Your right about tuning also. Because overcompensation is really noticiable.
True, if you tune it you should be a able to distinguish various 'modes':
1) an amplified (to a certain extend) oscillatory mode, in which the thing
oscillates around the direction to which it should point
2) a damped mode: ofter a couple of times oscillating back an forth it
should converge to the direction to which it should point.
3) a critically damped mode (think that's the name for it) in which the
object immediately turns to the direction in which it should point and
holds still there (it doesn't oscillate around it).
4) a mode in which it never gets to point in the direction to which it
should point (I suppose you can say because the reaction to a divergion
from that wanted direction is too weak).
You should be able to find all those modes back when you tune the thing,
but I can imagine mode (3) is maybe very hard to find if it can be found at
all. Of course this depends a lot on the wheights you use and like Bruce
mentioned, on the distance from the weight to the axis of the system. (this
is an important design-consideration, especially if 'inertial rotation' is
used for more axes (is this actually the plural of axis; couldn't find it
in my dictionary) since then it gets more difficult to get all the masses
in the robot niceley distributed).
>One of the coolest aspects to the bot is you can spin the robot by hand and
>it reasonably quickly compensates for the spin. One of the more important
>things to look at is the weight of the robot and box, and the weight of your
>weight. Which ever is the lighter object will spin first. And eventually
Logical, that's why it is called inertia: the heaviest object is most inert
and thus will react on a force with a smaller velocity or rotation as a
lighter object.
>both objects will catch up to one another. Also, if you spin them too fast,
>then you won't acomplish anything, but if you spin it too slow, then the
>effects may be negated. Otherwise, neat bot. And your right, I looked it up,
>and this is essentially the way they direct missles and control satelites,
>although these are more gyroscopes then anything else I suppose.
Thank you Dennison, for the conformation by experiment !
Regards,
Wouter Brok.
__________________________________________________________________________
The concept of 'inertial rotation' is: by means of a motor, with a weight
fixed to its axis, the object to which the motor is attached can be made to
rotate around the line set by the axis of the motor. Not only can the
object be made to rotate, it also can be stopped rotating around this
rotational axis by the same motor and in this way the object can be
positioned pointing with one side in a particular direction.
__________________________________________________________________________
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