Syncing Two Conveyor Roll Motors

[bodoo23]

I have a project including two parallel conveyors carrying a wide material. There is no mechanical gearing. I have two powerflex 755 controlling the motors. I need to sync conveyor motors. I don't feel like running both motors independently by sending speed setpoint to each one will work. Probably I will need a better syncronization. I also don't know if it helps if I use a virtual axis and send both motors same position setpoint.
Is there anyone who accomplish something like this ? If so, how did you do this with pf 755 or similar vfd ?

 

[JRW]

This help?

https://dtsheet.com/doc/1313817/drive-application-software


Is this a tenter / stenter frame?
Just curious

 

[Phrog30]

I don't feel like running both motors independently by sending speed setpoint to each one will work.

Why do you think this? Have you tried it?

 

[bodoo23]

This help?

https://dtsheet.com/doc/1313817/drive-application-software


Is this a tenter / stenter frame?
Just curious

The document seems very helpful. Thanks, I'll read it.
Btw, I didn't understand question.

Why do you think this? Have you tried it?

No, I will try in a couple of weeks.

 

[JRW]

A tenter frame is two independent endless chain that “grab “ the material on each side and usually take this into an oven
It’s a textile term

 

[bodoo23]

A tenter frame is two independent endless chain that “grab “ the material on each side and usually take this into an oven
It’s a textile term

No, it is actually a regular conveyor.
Btw, I had a look at the document you shared. though pf700 control diagrams are little different than pf 755 , it may help. I also see phase locking control in pf755 manual. Can't it be used in this case ?

 

[DarrylR]

Electronic gearing?

 

[Peter Nachtwey]

I also don't know if it helps if I use a virtual axis and send both motors same position setpoint.

This is the way to do it. Also, the slave/conveyors should be able to use or generate feed forward values from the virtual master's speed and acceleration.

Is there anyone who accomplish something like this ?

Yes, many times.

If so, how did you do this with pf 755 or similar vfd ?

Yes with servo motors or VFDs and hydraulic servos.
The controller that is generating the virtual master will need feed back from the two conveyors.

 

[bodoo23]

This is the way to do it. Also, the slave/conveyors should be able to use or generate feed forward values from the virtual master's speed and acceleration.

Yes, many times.

Yes with servo motors or VFDs and hydraulic servos.
The controller that is generating the virtual master will need feed back from the two conveyors.

Is this ok for you to share with me a sample of code or document that you refer to for powerflex 755 ? Since I am not familiar with motion. I can't imagine how to accomplish it in codes.

 

[widelto]

@Boodo23, Try this:

https://www.rockwellautomation.com/...-8269-4c18-6f3b86f7c4c0;deepLinking=undefined

 

[GaryS]

I have looked at the question and the many answers posted here
I already know I am going to kick up a lot of comments with this but I have been through this before
the application is a “Share a common load” the best way to do this is a torque follower set up.
One vfd is the master and served as the master speed control the second vfd is setup as a torque follower, it’s torque reference is the torque the master is producing. This way both vfd’s will always share the load equally.
Some people like to set the torque vfd speed reference at full speed / 60 hz I prefer to set the speed command for the torque vfd to just above the master that way if the load material is suddenly removed the 2 conveyors will still run as relatively the same speed.
If you try to use speed follower as many have stated. You should while things ware running have a look at the output current / torque and speed of both vfd’s you will see they are fighting each other.
You will see that the current output of both vfd’s will be constantly changing.
There are many examples of how to do this exact control available if you check on the Yaskawa elearning they have an example of this exact application.
I have observed this on many systems, not to long ago I observed it a production line conveyor that was 3 drive system spaced through the length of the conveyor they were setup as speed follower and in all 3 I observed the output speed changing about 5 hz with a very large change in the current of each vfd.
The other advantage with using the torque follower is that the motors do not have to be the same size, but each will contribute the same percentage torque for their size. I have run into that where they just needed a little extra power to handle the load.
Years ago I observed this o a web printing press where they added an addition print unit
All connected on a common shaft. It was a DC drive system the main motor was abut 100hp and the helper was about 25hp this system worked great together

 

[Peter Nachtwey]

Is this ok for you to share with me a sample of code or document that you refer to for powerflex 755 ? Since I am not familiar with motion. I can't imagine how to accomplish it in codes.

I have no examples doing this with a Powerflex 755.