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Unread November 18th, 2019, 06:50 PM   #1
alexbeatle
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AB PF525\ + Ethernet Encoder

Hello,

I'm looking to setup PF with an Encoder position feedback. PF525 is easy, PF527 needs motion setup. My motion is a lift (up/down). Is Ethernet quick enough to give feedback from encoder via PLC to feedback control the PF525? Looking at this encoder AFM60A-S4IB018x12.

Last edited by alexbeatle; November 18th, 2019 at 06:52 PM.
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Unread November 18th, 2019, 07:21 PM   #2
Ken Roach
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Quote:
My motion is a lift (up/down).
Does it move people ? Does it qualify as a crane ? If so, take a step back and consider the application and the various codes, laws, and regulations that might apply.

That being said: describe the configuration of the system and what the separate encoder is doing.

You always need an encoder attached directly to the motor shaft and connected to the VFD directly to run in vector mode well enough to handle a vertical load. My understanding is the PowerFlex 520 series drives support only quadrature pulse type encoders, with the 25-ENC-1 option module for the PowerFlex 525, and the 25-ENC-2 for the PowerFlex 527.

Are you talking about a follower application, where the lift mechanism follows some other mechanism with the encoder on it ?

The SICK AFM60A encoders, like the PowerFlex 525, are treated like cyclic I/O devices. Creating a follower application with I/O devices means writing your own position or gearing logic.


To make use of CIP Motion to do velocity gearing or position follower applications, you need a CIP Motion drive (the PowerFlex 527) and a CIP Motion encoder like the A-B 842E-CM. You also need a ControlLogix with an Ethernet module that supports CIP Motion (like 1756-EN2T) or a CompactLogix that has the "-ERM" suffix.

To my knowledge, A-B 842E and SICK AFM60A are very similar, but SICK doesn't directly sell an equivalent to the 842E-CM, which supports CIP Motion.

Last edited by Ken Roach; November 18th, 2019 at 07:27 PM.
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Unread November 18th, 2019, 07:46 PM   #3
alexbeatle
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Quote:
Originally Posted by Ken Roach View Post
Does it move people ? Does it qualify as a crane ? If so, take a step back and consider the application and the various codes, laws, and regulations that might apply.

That being said: describe the configuration of the system and what the separate encoder is doing.

You always need an encoder attached directly to the motor shaft and connected to the VFD directly to run in vector mode well enough to handle a vertical load. My understanding is the PowerFlex 520 series drives support only quadrature pulse type encoders, with the 25-ENC-1 option module for the PowerFlex 525, and the 25-ENC-2 for the PowerFlex 527.

Are you talking about a follower application, where the lift mechanism follows some other mechanism with the encoder on it ?

The SICK AFM60A encoders, like the PowerFlex 525, are treated like cyclic I/O devices. Creating a follower application with I/O devices means writing your own position or gearing logic.


To make use of CIP Motion to do velocity gearing or position follower applications, you need a CIP Motion drive (the PowerFlex 527) and a CIP Motion encoder like the A-B 842E-CM. You also need a ControlLogix with an Ethernet module that supports CIP Motion (like 1756-EN2T) or a CompactLogix that has the "-ERM" suffix.

To my knowledge, A-B 842E and SICK AFM60A are very similar, but SICK doesn't directly sell an equivalent to the 842E-CM, which supports CIP Motion.
It moves (stacks) objects, not people.
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Unread November 18th, 2019, 07:53 PM   #4
Ken Roach
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OK, that's good. How about the functional aspects of it ?

In general, if you need a position follower or multi-axis coordination, you need to use the ControlLogix motion subsystem, which means (at least) the PowerFlex 527 and a 842E-CM encoder.

If you just need to read the position of a dancer or probe or lift or pallet, then you might be able to use a simpler position measurement and position control product.

Last edited by Ken Roach; November 18th, 2019 at 08:08 PM.
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Unread November 19th, 2019, 12:46 PM   #5
alexbeatle
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Quote:
Originally Posted by Ken Roach View Post
OK, that's good. How about the functional aspects of it ?

In general, if you need a position follower or multi-axis coordination, you need to use the ControlLogix motion subsystem, which means (at least) the PowerFlex 527 and a 842E-CM encoder.

If you just need to read the position of a dancer or probe or lift or pallet, then you might be able to use a simpler position measurement and position control product.
It's a lifter\stacker that stacks objects. The objects vary in height and due to different possible permutations I'd need numerous sensors to detect how to stack based on already existing stack.

I have a DB of heights based on the QR-code of the objects. My concept is to stack based on the encoder value.
Ex. obj1=4cm, obj2=7cm, obj3=15cm. Translate height to encoder value and drive lifter\stacker until the value is met. There's room for tolerance since the objects have wide grooves for pickup.

The question is whether I need something complicated like PF527 with CIP Motion or I can write logic to read encoder values and start\creep\stop the PF525 instead.
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Unread November 19th, 2019, 01:48 PM   #6
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Yes the Ethernet encoder is plenty fast enough. What is of concern here is the tolerance you need for positioning. If you have a tight stop tolerance say better then +\- 10mm you need to use the pf755 with torque proving so you can provide full torque at zero speed.
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Unread November 19th, 2019, 02:03 PM   #7
alexbeatle
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Originally Posted by _Dock_ View Post
Yes the Ethernet encoder is plenty fast enough. What is of concern here is the tolerance you need for positioning. If you have a tight stop tolerance say better then +\- 10mm you need to use the pf755 with torque proving so you can provide full torque at zero speed.
I think PF525 will suffice. Thanks for the advice.
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Unread November 19th, 2019, 02:12 PM   #8
Ken Roach
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I'm still trying to understand the role of an Ethernet encoder in this application.

If you want a positioner, buy a positioner. The effort involved in creating a positioner out of a non-positioner is going to exceed the differential cost, especially if it's just for one machine.
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Unread November 19th, 2019, 05:16 PM   #9
alexbeatle
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Quote:
Originally Posted by Ken Roach View Post
I'm still trying to understand the role of an Ethernet encoder in this application.

If you want a positioner, buy a positioner. The effort involved in creating a positioner out of a non-positioner is going to exceed the differential cost, especially if it's just for one machine.
Please give example of a positioner.
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Unread November 19th, 2019, 06:04 PM   #10
Ken Roach
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I'm trying to understand your application, including what the external Ethernet-connected encoder is doing. It would be great if you also described the mechanism of the hoist, to get an idea of whether torque proving is necessary to hold and move the vertical axis. A rope drum, a ballscrew, an Acme screw, a rack-and-pinion, or a scissor lift would be different ways to hoist a platform.


By "positioner", I mean a motor control device with a position control feature.

Most servo controllers are position controllers, and some high-performance VFDs have the ability to control position as well.

Some of them are simple "indexers" that move from setpoint to setpoint, and some have dynamic position control that allows them to coordinate with other axes or follow position cams or "gear" to another encoder or motor axis.

The PowerFlex 525 has a very simple positioning mode, including up to eight "Step Logic" positions it can go to.

The PowerFlex 527 has a more powerful positioning mode, allowing it to act as a Motion Axis with ControlLogix or CompactLogix controllers. It doesn't have the precise control of a Kinetix servo drive, but it's less expensive.

Remember that the Kinetix 5500 can also run ordinary induction motors with encoders attached to them.

Have you already selected the controller for this application ? Do you have a motor picked out to run the vertical axis ?

In my opinion you should spend a little more money on Prototype #1 hardware so that it's easier to learn the parameters of what your control system can do. If it turns out to be overkill, you can experiment on subsequent machines with the option to return to your original design.
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