[etherlab-users] Beckhoff AX5000 update rate

Tom Wong-Cornall tom at wongcornall.com
Tue Jan 28 21:28:41 CET 2020


On Wed, Jan 29 '20 at 04.56 NZDT, Hugh Sparks <hugh at csparks.com> wrote:
> At first, I thought this meant that the drive needed a sample period 
> of 250uSec.
> But CycleTimeSync1/@Factor=-1 implies that the sync1 shift time should be 750uSec.
> 
> So if "Sync0 + Sync1 timer values *must* add up to your cycle time", is
> OpMode "DcSync250" the correct choice for a 1kHz update rate?

I have no experience with the terminology used in the ESI files, I'm 
sure somebody more knowledgeable can chip in. But timer values of 
Sync0=250/Sync1=750, with no shift at all is correct for 1kHz. Some 
Sync0 shift can be applied if necessary to get the sample point in a 
more convenient place, but it's not necessary if your application time 
is in phase with Sync0.

Luckily you get some useful diagnostic codes (that are even displayed on 
the LCD) around the sync and cycle time settings, that can be queried in 
Beckhoff's Infosys webpage. See 0xf409 through 0xf415.

> Since I'll be fighting with SERCOS to get the drive started, I want to 
> make sure the basics are right.

I know the feeling :) Luckily the AX8000s are CoE, and look like they're 
starting to get useful (40A axis modules "2nd quarter 2020").  
Documentation is still very thin though.


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