Why do servos have to be so difficult?

TheRooster

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Jan 2022
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I've only done about a dozen full projects but I can not for the life of me stop getting completely destroyed everytime I try to turn a gd servo motor. Everything else seems to be coming along and servos it's like day one every day. Here's a fun one, Kinetix 5500 connected to an MPL servo I'm trying to set up. Can't get it in stopped mode to do hookup tests because commutation not configured! LOL how am I supposed to set up the commutation with the start inhibited?!? Running logix v35 fyi.

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Thank God for this forum I probably would've quit long ago if not for it.
 
Forgot to add yes I've read the manual that commutation only applies to 3rd party motors, but obviously there's some problem, and here's the exact fault code

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Did you select the motor by catalog? That's all you need to do. That automatically sets up all the feedback parameters.
 
As for the difficulty comment, kinetix aren't too bad. I've done literally 1000s of them. Occasionally run into a bad lot of components which is always no fun. I did an install of 60 kinetix 6500s and all of them had bad gold connectors to the safe off board. Bad lot. Another install of 29 axes, and the shielded case of the rj45 port was manufactured 1mil too long and would short out the cat6 cable unless you tugged on it a little. Doing an install this week of 20 5700s using the 2198 hiperface to DSL converters for feedback. 6 out of 20, bad right out of the box. Fortunately had some universal bus converters from another install, so borrowed those to get it going.
 
Like others have said before, If you haven't configured it by Catalog Number, please choose the correct MPL motor configuration. If you already have, I've experienced a bug before where the commutation config gets lost, and AB confirms this will happen if you try to perform the commutation test on a motor that has commutation set from the factory. In my case, it was a VPC motor, but the procedure below cleared it up for me.

Servo Drive: INIT FLT S04, Commutation Not Configured

If the commutation hookup test was executed on a system having a standard Rockwell Automation permanent magnet motor, this fault will be displayed on the axis. This is because the standard motor’s data file already includes a commutation offset. Doing this type of Hookup test changes this offset value and would result in incorrect operation of the motor.

To clear this fault, follow these steps:
  1. Go offline with the controller
  2. Go to the axis properties in RSLogix/Studio 5000 Logix Designer
  3. Select the Motor category
  4. Click on Change Catalog
  5. Select the motor type of NONE, click OK, and Apply
  6. Click on Change Catalog again
  7. Now select the correct motor from the list, click OK, and Apply
  8. Download the project
  9. The axis state should now go to Stopped

The saved motor configuration for the axis in question may need to be cleared and then re-initialized with the procedure above. Good luck!
 
I've had the same experience. Each new brand/series has a host of quirks to learn. I've had the best luck when we puchased from a vendor with phenomenal app engineers who come out and help/teach. It's still a major time suck.
 
I haven't done many motion projects with servos (more with steppers), but the first one was retrofitting a Kinetix 6500 to a machine with an Anorad linear motor. It was previously controlled with a PLC5 and an IMC servo controller (I think...may have been a Kollmorgan drive). AB provided a motor file for it and had a local engineer stop by to help me with the initial startup and tuning. Once that was done, it was relatively smooth sailing. Thing's been running for a decade with no servo issues whatsoever, so I'm maybe a little proud of it :)
 
Thanks for the replies I was able to fix the issue using an old technote and redoing the motor polarities, not sure how this happened except that I lost STO during my first polarity test so it failed and maybe that's what caused this glitch.


I would say that I have less issues with HMIs, VFDs, PLCs, Valves, Sensors, Motors, Safety Scanners/Light Curtains, Clamps, Hydraulics and Operators combined than I do with servos. So is what it is I guess.
 
Thanks for the replies I was able to fix the issue using an old technote and redoing the motor polarities, not sure how this happened except that I lost STO during my first polarity test so it failed and maybe that's what caused this glitch.


I would say that I have less issues with HMIs, VFDs, PLCs, Valves, Sensors, Motors, Safety Scanners/Light Curtains, Clamps, Hydraulics and Operators combined than I do with servos. So is what it is I guess.
I'm glad you were able to figure it out! Where did you find the old technote? I save technotes whenever I see one just in case I need it. Only problem is remembering that I have it or where I saved it.

I think everyone is in the same boat regarding how much more of a headach servos are compared to everything else. I would guess that the only people who feel fine are the ones who have been lucky enough to work with one main platform their entire career, doing similar move commands, and also having a very knowledgeable vendor. I estimate now and everytime there is a servo that isn't what our team is used to, or isn't going to be applied in a similar manner as what we are used to, I add a chunk of time. It can be difficult justifying it to anyone without the same breadth of experience commissioning and programming servos.
 
I found it searching through the Rockwell site on like the 20th try, don't remember exactly what I searched. And yeah like you said doing anything new like a new type of movement or different gearing/grouping is a whole can of worms almost the same as using a whole different brand's drive.
 
Servos - Check the work of your Mechanical Engineer before purchase.

The ME only looks at Torque/Fore, and buys just enough to cover their clueless math, typically marginal. We often have to remove failed under sized servo motors and replace with larger at day one of testing.

The ME also often does not understand optimal RPM. Although the servo is happy at any RPM does a 8,000 rpm servo operate well at 50 rpm? They never ask what the customers daily operating process is.

All the "hook-up" tests and tuning strategies won't overcome a miss-fit servo.

Launching many well fit servos over the last 10 years, with an AB Servo Motor, coupled to an AB drive, entering the motor catalog number into the axis configuration, has netted us excellent performance, without any effort. I consider myself lucky?

Admittedly, our servos typically only need to execute simple, s-curve absolute position moves, so my experience could be considered limited.

Restated, on a like project, I requested the ME to change his gear box ratio to allow the servo to run at 50 percent of rated RPM. At start-up, the most senior experience customer stated about a joystick operated key process: "That is the smoothest, best, motion response I've experienced"
 

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