fieldbus control

[thekman]

Can anyone point me to a succinct explanation of where to begin in choosing a means of commanding a servo drive via fieldbus (with no fieldbus experience), from a PLC or similar?
I understand there is a command protocol used by the drive that may be communicated via fieldbus, which I should be able to construct in a suitable PLC package(?).
The google searches have been unproductive and exhausting. I really just need a good starting point.
Thanks

 

[danw2]

I'm not a drive guy, but I see lots of threads on Modbus or Profibus/Profinet as digital protocols used to communicate to drives on the PLCs.net forum.

Click on the Live PLC Questions and Answers link.

It's debateable whether Modbus qualifies as a real Fieldbus. I'm more comfortable calling it a digital protocol.

Profibus or Profinet are both engineered fieldbuses.

 

[John2025]

I'm not an expert either, but I like EtherCAT a lot better than modbusTCP (I like your digital protocol description). It probably depends on what you're really trying to send between the PLC and the drive. Are you sending the drive a command to execute a canned motion in the drive or control the drive in real time like you might do with an analog +/-10VDC signal?

 

[thekman]

As I understand it, the servo may be controlled by the drive - (forward, backwards, stop), read/write parameters and get fault status and position, via "fieldbus" between the drive and a controller. Finding the right controller to accomplish this, then how to accomplish this, is where I am. I envision a PLC with a programmable serial interface (fieldbus?) where I can set up the drive mfr. protocol.

Once a profile is set up, I will not need "real time" control, other than run, stop, reverse, run fast. I hope that makes sense. I'll need the controller (PLC?) to monitor external control signals and instruct the servo accordingly, as well as to turn on/off some other outputs.

I generally use discrete PLC outputs (w/o a servo), but with the drive I'm looking at, and from what I can tell, most drives, the discrete IO control/status is very limited with a ridiculously small budget

 

[John2025]

It sounds like you could use whatever is common to both the drive and the PLC. ModbusTCP is probably the most universal. Don't forget your HMI if you're going to have one.

 

[controlsdude]

I would look for a servo drive that can communicate over ethernet. This is becoming the defacto way to control drives with a plc.