Sphenix-tpc-l mailing list

[Dan Cacace <dannycacace AT gmail.com>]

Hi Tom and Bob,

Agreed, we will definitely learn a lot when we play with the motors. I also don't like the idea of relying on slamming the motor up against a mechanical stop, but the alternatives seem relatively complicated and problematic (more work is definitely needed here). I wasn't aware of the variability in step size, though for the short term it may average out, because we will be moving the motor back and forth, as opposed to continuously in one direction.

-Dan

On Mon, May 11, 2020 at 10:44 AM Thomas K Hemmick <tkhemmick AT gmail.com> wrote:

OK, thanks.  We'll need to keep on top of this.  As the web site says that slamming the motor up against a mechanical stop will not harm the motor, we can imagine that as the simplest "homing" procedure, but it just feels wrong.  Possibly we can get a cute setup going soon for which we use a laser to measure wander of repeated motions over time.

Tom

On Mon, May 11, 2020 at 9:33 AM Bob Azmoun <azmoun AT bnl.gov> wrote:

Hi Tom,

I was looking over my email exchange with the PiezoMotor rep. from last year and indeed he mentions that the number of motor steps per number of um’s of linear travel will drift over time. However, the good news is (from what I can tell) the drift isn’t so large that a continuous correction is absolutely required using a closed loop setup with an encoder (which is hard to get for the smaller motor). An open loop setup is also possible using a homing procedure (that uses a limit switch or whatever), which will still provide very good precision, but we need to get a number for this. In other words, it would be good to know how much the steps/um constant drifts over time or over some number of start/stop cycles. This way we’ll know how often we have to do a calibration to maintain a certain level of precision. I’ll email the same rep. who seemed pretty helpful last time. Maybe Dan has some info too.

Cheers,

Bob 

On Fri, May 8, 2020 at 3:22 PM Thomas K Hemmick <tkhemmick AT gmail.com> wrote:

This link also says that you cannot know the position by counting the steps since the step sizes vary by 5-10%. We need to learn more about how to operate them with the required precision. 

Tom

On Fri, May 8, 2020 at 3:03 PM Bob Azmoun <azmoun AT bnl.gov> wrote:

Interesting, very good to know (these things are really amazing!). Even though the motor can stop at the 1nm level, I wonder what the repeatability is if the arm crashes to a stop instead. That is, if we are considering to use a mechanical stop as a reference.

On Fri, May 8, 2020 at 2:17 PM Dan Cacace <dannycacace AT gmail.com> wrote:

Hi Bob and Tom,

Just doing a little googling and found FAQ about Piezo LEGS®, but I imagine it applies to the technology in general. Among other things, it says that "The motor will not be damaged if it is run to a hard stop."

https://www.micromo.com/technical-library/piezo-motor-tutorials/piezo-motors-faqs

-Dan

On Thu, May 7, 2020 at 9:40 PM Bob Azmoun <azmoun AT bnl.gov> wrote:

Dear All,

It was decided to meet again this week, so we will have a meeting tomorrow at 9am. 

A link to the Indico page is here: https://indico.bnl.gov/event/8493/

and the bluejeans link is here: https://bluejeans.com/881710315

I put together a tentative agenda, but please feel free to modify it and upload any material you wish to present. 

Talk to you tomorrow!

Cheers,

Bob

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-----------------------------------------------
B. Azmoun
Brookhaven National Laboratory
Physics Dept. Bldg. 510 C
Upton, NY 11973
P: (631) 344-4082
F: (631) 344-3253
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--

-----------------------------------------------
B. Azmoun
Brookhaven National Laboratory
Physics Dept. Bldg. 510 C
Upton, NY 11973
P: (631) 344-4082
F: (631) 344-3253
-----------------------------------------------

--

-----------------------------------------------
B. Azmoun
Brookhaven National Laboratory
Physics Dept. Bldg. 510 C
Upton, NY 11973
P: (631) 344-4082
F: (631) 344-3253
-----------------------------------------------