Kinetix 5500, VPL, and AutoTune.

Jeev

Member
Join Date
May 2008
Location
Brisbane
Posts
733
Ahoy hoy.

I have used a number of K5500/VPL systems over the last couple of years, but this is starting to really annoy me. I have had to manually tweak some of my axis, because all I ever get from the AutoTune tab is a small "click" or "clunk" on the mechanism, and then it says it's complete and suggests some parameters. No matter what numbers/parameters I put in, what type of drive/servo, or mechanism. At times it may fault on position or velocity error, but it will still say complete and suggest parameters. These are all axis that otherwise work fine under motion commands with the same parameters!

Can anyone shed light on what's going on? I have a number of linear and rotary axis to play with at the moment and see what I'm doing wrong. Does anyone else have issues with AutoTune and/or does anyone actually use it?
 
I have had little luck with AutoTune. I just did a startup with a 33 axis machine using Kinetix 6500 drives. Auto tune worked fine with a rigidly coupled axis, but fail miserably with compliant coupled axis. Autotune would introduce resonance in the axis and they would overshoot badly. I had better results turning on the Load Observer and doing a little manual tuning. Rockwell has a good manual on servo axis tuning on their website. It is Publication MOTION-AT005C-EN-P. It describes proper tuning techniques
 
I have had little luck with AutoTune. I just did a startup with a 33 axis machine using Kinetix 6500 drives. Auto tune worked fine with a rigidly coupled axis, but fail miserably with compliant coupled axis.
Yep, most auto tuning system only exist so the marketing guys can say they have auto tuning even though it doesn't work in many cases. They use a square wave to excite the motor and take only 3 data points. This is not enough for accurate auto tuning even if the auto tuner supports the right models.

Hydraulic systems are compliant and we auto tune those easily as long as they are linear. A hydraulic system can be modeled as a mass between to springs.

There is also the problem of using the right algorithms as well as support multiple models a system may need to tune.

I have been very busy lately so I haven't had time to start an Advance Control topic on auto tuning. However, if you want to get an idea of how I do it go to
https://youtu.be/qzr6eL90Aok
There is a follow up video that covers a more complex system.
https://youtu.be/lermULNDz3M

BTW, most college professors are clueless when it comes to this topic.
But, I admit I did get some help from the control station ( controlguru ) guys.
I think they decided to help me because I am not a competitor and I was so close to getting it right.
 

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