I am trying to set up a closed loop control system to synchronize the speed of 2 different sized rollers. The large roller is driven by the Product "web" and would be my master. The smaller roller is driven by an AC motor controlled by a Powerflex 4 VFD. The small roller needs to match the speed of the product (surface speed of the large roll) as it applies a painted pattern on the web. Too fast or too slow and the painted image will smear. I am not a controls engineer so I need a little help. I am wondering if I can get my 0-10VDC analog speed signal for the drive from a tach generator that rides on the master roll and use feedback from a similar tach on the smaller slave roll? I am sure these signals will have to go through a comparator of some sort to make the speed correction. What components are required for this?

Thanks,

 

You can use tacho of master roll as speed command for smaller slave roll. The tacho of slave roll maybe used for slave VFD as speed feedback if it possible.

But you must scale a speed slave signal for move web at the same linear speed.

But if you need higher level of synchronization, Master-Slave with closed servo loops must be evaluated.

 

This is really a master-slave positioning application? You probably won't get good results using analog. If you can feed the master encoder signal into the slave drive and scale speed from that, you might be OK, but to do it properly position mode is best.