Synching motor drives help please

[Sidewinder]

I would use a high resolution encoder on C and gear B AND A to C. The master should always have a high resolution encoder. Using analog for velocity reference is lame if position need to be synchronized. Gearing should be done using positions. To do it any other way is less than optimal unless there are times when A and B can move independently.
Gearing A to B and B to C is poor technique. I can explain why but take my word for it.

Absolutely Peter, I could not agree more, I gave the suggestions I did, because the existing solution worked OK, and the OP was asking for an add-on rather than a complete re-engineer of the system.

OP please take note, if you REALLY need synchronisation, then this is a much better way, use a hi-res encoder on the master machine, then synchronise the slaves to this single master.
We used to call it ELS for Electronic Line Shaft at my previous employer.
The master encoder was however, in software & all the axes were slaves.

 

[Peter Nachtwey]

The master encoder was however, in software & all the axes were slaves.

This is the best way. This is the way I would do it because now the master position, velocity and acceleration are perfect and not quantized or suffer from sample jitter.

 

[Sidewinder]

It is good Pete, the company used to control whole printing presses with all axes synchronised from the master encoder down SERCOS II interfaces.

 

[mrt19]

Thanks to everyone for their ideas and comments. I was able to contact one our former engineering and got info on the controller I was mentioning. If that does not get it close enough I will go the encoder route.
Thanks again,
MRT19