What does unwind mean?

[yang1216]

Hi all, I am a new hand of AB servo. When I read the manual, there is a term that I don't understand.
Could anyone explain it to me, what does the term 'unwind' mean? And unwind value, unwind cycle.
Thanks very much.

 

[iant]

usually I would say unwind means go and have a drink.
But
servos have absolute encoders fitted these can be single turn or multi turn.
the term unwind means return to the 'Home' position

 

[Peter Nachtwey]

It could mean to unwind the integrator.

 

[iant]

like that one
oops
and around we go again
HOW DO WE STOP THIS

 

[kekrahulik]

I believe you only see "unwind" when you setup the axis to be "Rotary" Positioning. This means that after moving for x units, the position is back to the starting point. For example, a servo is turning a wheel on a car. After traveling 360 degrees, it is back to where it started. Depending on how you are setting things up, it may be 360 degrees or the tire circumference inches or whatever units you're working with.

If you set your positioning to "linear" I don't think you will see anything related to "Unwind"

 

[JordanCClark]

From some manual:

If the axis is configured as a rotary Axis in the application setup menu,a value for the Unwind constant is requested. This is the value used to perform electronic unwind of rotary axes. Electronic unwind allows infinite position range for rotary axes by subtracting the unwind value from both the actual and command position every time the axis makes a complete revolution.

 

[Mark Buskell]

On a rotary it also depends on it you are going through a gear box. My drive resolution might be 200,000 but it I had a 4:1 gear box the unwind would be 800,000.
Another example is my servo drive gives me 2000 counts per 1 degree.
2000 * 360 = 720,000 counts. I have no gear box so my unwind and drive resolution are sat the same.

 

[yang1216]

Thanks very much.