Can Kflop take encoder axis feedback with closed loop servos?

Hi I'm a newbie to this, but looking to purchase soon and learn as I install. Kflop seems like a good option to me.

I understand kflop can take encoder feedback from a digital scale on the load, as is on my DRO currently, but can this be used successfully in conjunction with servo drives that already have their own feedback?

I understand their might be 'fighting' but could you not just make the scale reading the 'master'?

I am looking to try compensate for backlash in the system beyond what I can remove mechanically.

Thanks.

There is a really good video by Dr Jacob Tal on the Galil Motion site that explains the problem of having a servo encoder together with a scale, particularly where there is slight backlash on the servo axis.
The PID loop has to be divided between the Encoder and scale.
Al.

Hi jdprints

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I understand kflop can take encoder feedback from a digital scale on the load, as is on my DRO currently, but can this be used successfully in conjunction with servo drives that already have their own feedback?

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I assume you are referring to Step/Dir Type of Servo Drives? Yes. See:
Closed Loop Stepper

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I understand their might be 'fighting' but could you not just make the scale reading the 'master'?

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I wouldn't describe it as "fighting" at all. More like "helping". One problem with Linear Scale Feedback is that all the mechanics including backlash is inside the control loop. This is great for accuracy but makes control difficult. For example when the motor is moving through the backlash the scales provide no information at all so the motor can move in an uncontrolled unpredictable manner. The feedback from the motor shaft allows the motor to still move in a controlled manner. So feedback from both nodes is somewhat mandatory.

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I am looking to try compensate for backlash in the system beyond what I can remove mechanically.

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I think Linear Scale Feedback is the best technique for compensating for backlash (short of mechanically reducing it) - but there are limits. If cutting forces or other disturbances cause the axis to move through the backlash there is nothing the control can do to stop it. The controller will attempt to quickly correct the error, but how quickly that can occur will be determined by the dynamics of your system.

Regards

Thanks Tom, I've seen that link, and although I've done Bode plots and PID in my time it was many years ago and I'm having trouble interpreting 90% of that page.

Could you confirm for me Kflop allows encoder feedback on the axis (glass scale) in conjunction with an encoder on the drive (servo or hybrid stepper rotary feedback)? Thanks. THen I can order a Kflop controller. I basically have the next 5 weeks free and would like everything 'here' to study it.

Hi jdprints,

Yes that is absolutely correct.

KFLOP itself only has single ended encoder inputs. If you have differential encoders and want to make use of differential signals you would need to add our Kanalog board or other 3rd party differential receivers.

See:
Dynomotion Motion Control Boards for CNC Manufacturing and Robotics Applications

Regards