Hello 

I have an iron blade that is driven by 20 motors along the way .

I have 2 question

1.How can i synchronize 20 motor and have constant speed along the way?

2.which drive is good for this project?  Sinamic V20 or G120c ? or ...?

Thank you for your support 

According to this article it's possible to drive upto 50 motors on one Sinamics G drive, if that's what you need:

https://support.industry.siemens.com/cs/ww/de/view/84049346/en 

What I understood from your description is that you have one piece of something like a band or a belt and you want to drive it with many motors.

In this case you may rather want to have load sharing than speed synchronicity. And to achieve this drives should support an isochronous network.