RE: What to use? EtherCAT or Ethernet Powerlink with CANopen protocol

I would like to thanks specialy to you Armin. Your participation were some
of the best.
Hope 2013 is not so bad as predicted!!
Cheers, 

Albert

 

-----Mensaje original-----
De: Steinhoff [mailto:[email protected]] 
Enviado el: lunes, 17 de diciembre de 2012 14:45
CC: Albert Saenz; [email protected]
Asunto: Re: [CANLIST] What to use? EtherCAT or Ethernet Powerlink with
CANopen protocol

Albert Saenz wrote:
> Armin wrote:
>> It's sometimes hard to find out what are real fieldbus facts and what 
>> are
> marketing fictions :)
>> Regards
>> --Armin
> Armin, you refer some others that are introducing their products?
> It's sometimes hard to find out who is who and what his expectations 
> are. I don't mind! I'd like share and learn.
> I only want to introduce new alternatives that are appearing in the 
> market and what to decide. The problem until now was that still nobody 
> has told what would be his decision in case to switch to Ethernet 
> (bigger bandwidth in a real Hard Real Time application, don't forget
please).
> As Kees said, perhaps this is the wrong platform for this discussion. 
> Do you know where is the appropriate forum?
>
> Anyhow, let me say something doesn't depends on the bus type:
> in case of to have different latencies in a robot or machine-tool, 
> this has a direct reflection in the velocity's "jerk" (as a little
ripple). E.g.
> imagine one axis is moving at a constant velocity of 60 m/min during a 
> long distance. So V=60 m/min = 60 m/min* 1 min/60,000 ms * 1,000,000 
> um/m = 1,000 um/ms (that is 1 mm per Tick=1ms). Imagine that the 
> system can have 10us ('u' means 'micro') of latency, i.e. sometime 
> SYNC message is processed at
> 1.01 ms or at 0,99 ms. And so, the velocity is 1,000 um/1,01ms or 
> 1,000
> um/0,99 ms (of course that the Servo Drive amplifier will react 
> accordingly to the adjusted PID, but this will be the "jerk" I introduced
before).
> V= 1,000 um/1.01ms =  990.1 um/ms or 59.406 m/min Or V= 1,000 
> um/0.99ms = 1010.1 um/ms or 60.606 m/min Error= 100 * (60.606- 59.406) 
> / 60 = 120/60 % = 2%. Velocity's ripple is 2%.
> (These are the real terms we should talk in a Hard Real-Time 
> environment!) If the SYNC message has a 10us latency (this could seem 
> it is good enough), in applications of 0.5 ms the "jerk" would be of 
> 4% and so on. For High Speed Cutting machines (very dynamic machines) 
> with a Tick=0.1ms, it would be of 20% (!!!). We'd need, then, 1us latency.

I would say that's the case for a processing with FPGAs  -> VARAN bus :) You
are right,  we should stop this thread at this forum ...

All the best and have a nice Xmas time!

--Armin


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