Re: Holonomic and Nonholonomic constraints

> Message: 6
> Date: Mon, 16 Oct 2000 11:43:17 -0700
> From: Anne Ogborn <anniepoo@...>
> Subject: Holonomic and Nonholonomic constraints

> One sort of robot I've done more than mentally fiddle with, and which
> is a good design for placing an effector at a point in a large volume (like
> "somewhere inside this football stadium") is a "slack wire" robot.
>
> Put up 3 poles. Put a pulley on a swivel on the top of each pole. Cut 3 cables.
> Run a cable through each
> pulley and tie one end of each togather (call this the "effector").
> Build 3 winches with steppers or servos. Run the free end of each cable through
> a winch.
>
> Now, by pulling in and out on the 3 winches you can move the effector anywhere in
> a triangular cylinder. In practice, it works best in about the lower half of this
> cylinder and within the central area.
>
> Clearly one doesn't want to use this for CNC

Perhaps not, but if you add three more winches and cables, it would look
roughly like the NIST haxapod that Dave had at NAMES last year. Using
such a setup you have limited six axis of motion. Somewhere on the NIST
site is a rather good description of several of the experiments that were
done using cable connected Stewart platforms. I think that it was called
Reconfig.pdf.

>A car is a nonholonomic system.

Some of the EMC was also tested with a Humvee with binocular vision and
used corrected GPS for posiion feedback. So the machines you think about
are not that far fetched. Nor would they be that difficult to build a
control for.

Ray