Positioning with a vector drive/motor

[moosetracks555]

Positioning with a vector drive/motor
The application is a log lift to level a log before being cut by a chainsaw. The Powerflex 70 vector drives are being controlled over Ethernet IP to a L43 compact logix. Each lift has 3 HP motor driving a gearbox and a cam. The cam is cut for constant linear velocity. There are 10 of these devices that will all operate at once. Each cam has two adjustable height prox switches that are going to be placed near full up and full down. I am using a vector to bring the drive to a stop to eliminate a mechanical brake. The vector motor does a good job a stopping the cam.

I plan to have an input that triggers the cams to go up to a distance and then hold. The operator will then have the ability to adjust each cam lift independently so they can level the log. I was considering using the prox switches to trigger the decell cycle, or using the encoder with some sort of control loop that tries to stop the drive at a certain number (a range) of counts? I have done this before with limited success, and a lot of lines of programming, but that was with a slc. Are there better instructions in the compact logix to do what I want? I am open to any other suggestions also.

 

[itsmoked]

Could one cam/motor actually do the entire job in some cases?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[controlsdude]

Use the Motions programming of RSLogix5000, very easy to program and there are even a cam simulator that can do profiles. Just integrate the drives in the motions configuration and use the motions commands with the cam logic. Should be pretty straight forward versus a slc.

 

[moosetracks555]

Consoledude,
How do I intergrate the drives into the motions configuration?

itsmoked,
I have to have individual control of each lift to level the log so one motor/cam won't do it.

 

[itsmoked]

I was just thinking that if one cam is incapable of lifting the entire log then I would expect regular motor failures as a human trying to edge up that many different cams would undoubtedly end up having one cam exceed the others and hence take the full load.

It would seem to me that you'd want a button that advances ALL the cams up to some low fixed loading. Then one or two control sticks that tilt everything in a uniform manner or raise/lower everything in a uniform manner. That would be so much faster for an operator, would reduce the controls to a couple of buttons/levers, and would greatly reduce the individual motor/cam loads.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[moosetracks555]

The cams are designed to lift the entire log to help with that issue. The inconsistency of the log shape and length would make attempting to level with one or two levers almost impossible. I do plan to try using the drives torque mode once the system is up and running to see what that does.

I am still looking for suggestions on how to program the compact logix to control the position of the vector drive using the encoder feedback.

 

[controlsdude]

I would recommend since you have the programming tool, drive picked out that is all AB that a local distributor who deal with would be more than happy to help you.

I have had more success with local distributors helping me than getting suggestions off of forum. Do not mean to be blunt but I think your AB distributor has more skin in the game than we do here.

 

[PNachtwey]

I would recommend since you have the programming tool, drive picked out that is all AB that a local distributor who deal with would be more than happy to help you.

Fat chance. This can be complicated. The dimensions must be known if the log is to be cut straight. If the log is in a stressed position when it is cut the result will not be straight. Perhaps you don't care if the cut is straight. Letting the operator adjust each position makes sense because it is simple and people are pretty good computers.

The saw mill OEMs have scanners that can precisely measure the dimensions of the log so the rolls can be moved in or out automatically. The scanner relays the scan data to the positioners over Ethernet or Profibus. I doubt this is in the budget.

 

[controlsdude]

Fat chance

I think the poster is talking about taking an existing slc500 program already written and I am sure is pretty solid for this application. I suggested the poster to contact the local ab distributor. The distributor local ab expert would have the technical know how to get the ball rolling in helping the poster converting his program to an AB RSLogix5000 program with the motions programming that is integrated in the software.

This is probably a few lunch and learns with the AB distributor. If the AB distributor does not have the clients best interest than there not much of a distributor. I have used this route to get up to speed when I went from PLC5 to slc500 to contrologix and also siemens s7 and also used to get a plan together on different projects with different applications.

The question the poster needs to ask his AB guy is: Do I have all the hardware and software tools to do the job that he did with the slc500? If not, how do I get them and when?