Re: Do you think NI can fix my PLL?

Mike Monett wrote:
Chris Carlen <crcarleRemoveThis@xxxxxxxxxxxxxxx> wrote:
The requirements are not terribly difficult initially. About +/-0.5 degreees jitter is tolerable. But there is another dimension to the project to explore syncing two wheels together. This will need to be about 0.01 degrees p-p.

The first is OK. The second is going to be a challenge, especially when locking two wheels together.
My problem is that when I did it with a PM motor, it worked very well.
Hardware behaved with a few % of the sim. Moving to brushless is faltering, though the circuit is basically the same.

Different inertia? Loss of damping or friction when the brushes are gone?

Less friction, more inertia now. But also very different motor constants.

Maybe this has nothing to do with it, but whenever I tried cascading two pll's I always got into trouble. When one loop is locked to another, it seems to need a bandwidth 5 to 10 times higher than the first loop. Otherwise it goes crazy trying to follow the first one. It may appear stable at the beginning, but eventually it starts building up an undamped response until it limits. So I'd be wary of considering the problem solved until evey little nit has been uncovered:)

Oh, I wouldn't be attempting to lock one wheel to another, but both to the same reference clock. So that wouldn't encounter the problem you are mentioning.


Anyway, keep posting. Each reply gives more information that might lead someone to the answer.


Thanks for the input.


--
Good day!

________________________________________
Christopher R. Carlen
Principal Laser&Electronics Technologist
Sandia National Laboratories CA USA
crcarleRemoveThis@xxxxxxxxxxxxxxx
NOTE, delete texts: "RemoveThis" and
"BOGUS" from email address to reply.
.

Relevant Pages

  • Re: Possibly unrelated questions
    ... Are wheels going "backwards" and stop/slow ... and aliasing in more than one dimension is not at all trivial ... spectra combine with the time dimension, a unique 2D spectrum ...
    (comp.dsp)
  • Re: Possibly unrelated questions
    ... Are wheels going "backwards" and stop/slow ... and aliasing in more than one dimension is not at all trivial ... spectra combine with the time dimension, a unique 2D spectrum ...
    (comp.dsp)
  • Re: Ballasting of Carriages.
    ... before a Back to back dimension is recommended. ... You'd have to be using pretty ancient track standards for it not to be. ... Try Hornby wheels from a few years ago. ... Any scale track standard and wheel spread sheet ...
    (uk.rec.models.rail)
  • Re: Ballasting of Carriages.
    ... "NSWGR" wrote ... before a Back to back dimension is recommended. ... for common RTR 00 wheels and track. ...
    (uk.rec.models.rail)