Re[2]: digitising arm

Terry, Ballendo, list,

About twenty+ years ago, we had "sonic digitizers" (2D) for use in
Radiation Therapy Treatment planning. PHD's would trace tumors an
patient outlines into a compute to compute the treatment plans. It was
made by SAC, Scientific American C.. ???, anyway, they also made 3D
versions, and used a stylus which created a spark that could be heard by
the "linear microphones" along each axis. Not an arm, but might be an
interesting approach.

Alan

"Terry L. Ridder" wrote:

>
> hello;
>
> i am not sure what you mean by multi-axis
> (encoder at the joints) digitizers.
>
> i am going by the 3d digitizers that my daughter
> used while in college studing computer graphics
> and animation. the college had the fancy stl laser
> models. the problem with those was the object to
> be digitize had to be metalize. the ones my daughter
> mainly used where basically an x-y table and
> the lvdt probe was the z-axis. put the object on
> the table and run the digitizing program. the
> lvdt probe tip could be changed to improve detail.
> the tip was basically the tip of a ball-point pen.
> the probe gently "rode" the surface of the object
> to be digitized. depending on the object the may
> have to be repositioned but this was basically
> equivalent to a tool diameter and length offset.
>
> the probes themself could also be changed depending
> on what the requirements were. some where only
> +/- 0.5 inch others where +/- 10.0 inches.
>
> On Wed, 15 Nov 2000, ballendo@... wrote:
>
> > Terry,
> >
> > This makes sense for a cartesian based probe. Does it make sense for
> > the multi-axis (encoders at the joints) digitser? I mentioned earlier
> > that loading "arm" kinematics into EMC should work (using just the
> > feedback portion of the code).
> >
> > Ballendo
> >
> >
> > > it would seem that using a linear variable differential
> > > transformer (lvdt) as the probe would be reasonable
> > > starting point.
> > > Terry L. Ridder
> >
>
> --
> Terry L. Ridder