Parallel Encoder

[MBHladilek]

Newbie Question.
I would like to drive to different servos from a single encoder.
Is this possible?
With what type of encoder?
Do I need to build a splitter?
Thanks in advance.

 

[GE_Plcs_are_Love]

its not suggested as unless your mechanical connection is that strong you are very likely to get skew and could cause mechanical damage.

It is possible, you'll probably want to use an Open loop system where you feed the encoder data into a PLC and then use a common command signal that you send to both Drives

 

[MBHladilek]

Thanks for fast reply.
The servos are not mechanically or PLC coupled. Sorry for the lack of information.
The encoder is measuring a common running paper web. I guess I could couple two encoders to the same drive wheel.

 

[GE_Plcs_are_Love]

I guess the short answer is yes anything is possible, but is it the best choice.

in my industry we have two encoders per axis and we compare them nonstop to verify nothing runs away or skews. a bit more information would be helpful

I've also ran servos that were directly connected to each other and we did closed loop and set the Servos to master/slave.

the slave does whatever the master is doing and the master is the only one with closed loop feedback

 

[kamenges]

I would use a splitter in this case. Something like this from BEI is what I would go with. You may be able to get by without one of these depending on your drive supply wiring and grounding. But this splitter or somehting like it may keep away alot of headaches.

Keith

 

[MBHladilek]

Thanks again for all the fast informative replies.
I should learn to post complete process descriptions.
The servos perform separate independent functions relative to the paper web encoder information.
I took a look at the encoder signal splitter and it seems that it would perform the task I need, isolating and distributing a common encoder signal. I'll be looking into this product.

Michael

 

[BryanG]

If the splitter given is an earlier reply is cheap then go with it. Otherwise you can do the same job with a couple of opto-couplers like these.

Bryan

 

[Suresoft]

use the servo's in a daisy chain.

Why not feed the first servo with the encoder pulse and take the encoder pulses that the servo itself creates to feed the next servo and so on. This way they will all follow each other and you can scale the pulses between servos if need be for diameter control.

 

[MBHladilek]

Good idea, to daisy chain servos. The actual machine to machine wiring also affects these decisions, where as in this case distribution seems more applicable.

 

[GE_Plcs_are_Love]

Depending on what time of servo your using, some mitsubishi servo drives allow fiberoptic daisy chaining and have space for internal logic and IO.

What kind of servos are you using?

 

[MBHladilek]

SureServo SVA-2040 from Automation Direct.

 

[GE_Plcs_are_Love]

http://www.automationdirect.com/static/manuals/sureservomanual/sureservomanual.pdf
do you plan to use the internal logic?

Looks like theres no clean way of daisy chaining the signal, so a splitter is the obvious method, but it appears you can connect them to transfer data and then send a scaled speed command via rs485 (page 51) or send the direct signal and scale it via potentiometer for fine tuning (p. 149)

 

[MBHladilek]

GE Plcs,
Thanks for digging into it. Way more attention than I expected. I appreciate the helpful suggestions. Other requirements dictate PLC over control of the processes so splitting does seem the first option.
Best Regards,
Michael

 

[MBHladilek]

http://www.beiied.com/electronics.html

UPDATE http://www.beiied.com/electronics.html
Purchased the Broadcaster spec. for my application. The unit performs very well and met my encorder splitter needs.

Thanks for everyone's replies.