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

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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