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

[email protected] wrote:
>
> Gentlemen,
>
> From logical point of view, EtherCAT is a ring, but each device has an 
> ability to bypass
> connected physical segment if it is down. 

That's only partly true. If the power supply is broken of the errornous 
module it doesn't bypass anything.
Yes ... if one module is broken there is the possibility to split the 
initial ring into two rings ... but this works just for one broken module.

--Armin

> Physically EtherCAT networks can form any
> kind of topology.
>
> Powerlink follows standard Ethernet physical layer and if other than 
> star topology is
> required, hubs are needed. In practice, "hubs" are actually 
> cut-through type switches.
> Logical operation of Powerlink is based on a managing node requesting 
> controlled
> nodes to transmit point-to-multipoint packets.
>
> Redundant masters are challenging in any technology, even in CAN-based 
> CANopen,
> where change of effective NMT-master expects NMT-reset. However, in 
> CAN-based
> CANopen networks all transmissions can be asynchronous and NMT-master 
> blackout
> does not necessarily introduce any effect on the process signaling.
>
> On the contrary, master-node needs to trigger all transmissions in 
> both EtherCAT and
> Powerlink networks.
>
> Best regards,
>
> -H
>
>
>
>
> *Steinhoff*
>
>
> 	
> 	From: Steinhoff <[email protected]>
> To: 'CANLIST' <[email protected]>
> Cc: Albert Saenz <[email protected]>
> Date: 11.12.2012 11:33
> Subject: Re: [CANLIST] What to use? EtherCAT or Ethernet Powerlink 
> with CANopen protocol
> Sent by: [email protected]
>
>
>
> ------------------------------------------------------------------------
>
>
>
> Albert Saenz wrote:
> > Hi all,
> > My first participation!
> > I know that perhaps it is not the best forum, but in any case I 
> believe many
> > of you have the same problem nowadays.
> > Despite CAN bus is a nice and powerful field bus (I like very much 
> compared
> > with any similar industrial bus), we'd need to improve notably the 
> speed (1
> > Mbit/s is clearly not enough even multiplexing the 8 bytes telegrams at
> > R-PDO and minimizing all T-PDO). Bandwidth for Hard Real Time 
> applications
> > were the Tick should be less than 1 ms and massive I/Os and Motion 
> Drivers
> > should be controlled (typical CNC application) can not be limited by 
> the 1
> > Mb/s (even using multiple channels: 2 or more CAN buses, as our 
> applications
> > is using nowadays. 1 for I/Os and 1 o 2 more for control 4 or 8 axis 
> with a
> > tick of 1 ms). In case we need "multi-channel" (i.e. 2 or more 
> independent
> > CNCs running at the same platform), CAN bus drastically limits and 
> it makes
> > no sense in many application.
> > My question is (requesting opinions):
> > CANopen protocol is supported by EtherCAT (ETG group) and Ehernet 
> Powerlink
> > (EPGS group) and that simplify migration from CAN bus (or we could even
> > share both).
>
> The topology of the fieldbus must fit to your application.
>
> EtherCAT is based on a ring topology ...  EVERY I/O module must transmit
> every single bit throughout the ring.
> That means every I/O module could be a single point of failure ..
> EtherCAT is also bound to the transmission speed of 100Mbit/s.
> Fault tolerant master configurations (hot standby a.s.o) are hard to
> realize .. or nearly impossible.
>
> Ethernet Powerlink has a clean bus topology ... there are also master
> nodes based on co-processor boards which allows to run the bus
> independent from the load of the PC CPU.
> A problem with a single I/O module can't stop the bus. Ethernet
> Powerlink isn't bound to 100Mbit/s.
> Fault tolerant configuration are easy to realize because of the clean
> bus topology.
>
> --Armin
>
>
>
>
> > I would like to know Guru's opinion and those are many of you.
> > Thanks in advance for your contribution,
> >
> > Albert Saenz
> > Sant Cugat del Valles - Barcelona
> >
> > --
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> >
>
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