Peter-I have had good success in the past applying somewhat what you are saying to a rewinder but I had a dancer.
This sequence sets the "gear ratio"
Upon pressing the start button the rewind would take up slack in the web until the dancer was 50% full, once 50% full the unwind would start feeding material to the rewind.
Think of it this way, say we have a unwind and rewind that are driven from the same motor at the the exact same gear ratio, both roll diameters are the same and never change. No stretch perfect material. You should be able to use a dancer to take up the slack in the material and provide a specific tension. once the tension is set lock the dancer in place and hit the start the drive/motors. We are able to keep tension without a gear ratio.
OK out of the perfect world and back to my application. Have the Unwind set the web speed and have the rewind respond with speed to hold tension. I think the key to the process is the speed set point that is given to the rewind drive that is controlling tension. Then having the speed trimmed above and below this an equal amount using load cells i.e. +/- 10rpm. If our rewind speed set point is off so will be our actual usable +/- trim.
I am apologize I am not very good at articulating my ideas.
I should be able to make this work by setting the rewind speed setpoint but honestly my biggest worry now is that the rewind will start pulling the unwind and regenerate energy. The unwind needs a brake.
I quick read on tension basics
http://www.tappi.org/content/events/07place/papers/whiteside.pdf
This sequence sets the "gear ratio"
Upon pressing the start button the rewind would take up slack in the web until the dancer was 50% full, once 50% full the unwind would start feeding material to the rewind.
Think of it this way, say we have a unwind and rewind that are driven from the same motor at the the exact same gear ratio, both roll diameters are the same and never change. No stretch perfect material. You should be able to use a dancer to take up the slack in the material and provide a specific tension. once the tension is set lock the dancer in place and hit the start the drive/motors. We are able to keep tension without a gear ratio.
OK out of the perfect world and back to my application. Have the Unwind set the web speed and have the rewind respond with speed to hold tension. I think the key to the process is the speed set point that is given to the rewind drive that is controlling tension. Then having the speed trimmed above and below this an equal amount using load cells i.e. +/- 10rpm. If our rewind speed set point is off so will be our actual usable +/- trim.
I am apologize I am not very good at articulating my ideas.
I should be able to make this work by setting the rewind speed setpoint but honestly my biggest worry now is that the rewind will start pulling the unwind and regenerate energy. The unwind needs a brake.
I quick read on tension basics
http://www.tappi.org/content/events/07place/papers/whiteside.pdf