Can a kinetix servo motor 'drift' without a fault

[idresu]

we have a machine that has been running approximately 6 months. it has 4 servo axis and one seems to be going out of position but without showing an error. The axis in question seems to always be advancing the other axis. we have changed both the motor and cables. Conceptually, does anyone know is it possible for the drive to be 'loosing' encoder counts which would in turn make the physical axis advance its commanded position?

 

[StephenSDH]

Does the axis always travel in one direction? If the axis isn't scaled correctly you can accumulate error over time. Is it a Resolver or TTL encoder?

 

[itsmoked]

Certainly lost encoder pulses will cause your stated issue.

If you can use an oscilloscope on the encoder outputs you may see it's very noisy or there is too much capacitance on the leads causing distorted waveforms, etc.

Could be your hardware or software too. You may be driving too fast and some part of the system is just not up to the task.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[rdub]

If the scaling is correct and electrically, things seem sound, I would take a wrench to the motor couplings to make sure things are not slipping. Also, if the moves are pretty aggressive, belt slippage (timing belt jumping a cog) is a distinct possibility.

 

[idresu]

Thanks for the input.
The problem was very misleading but it did end up being mechanical slippage but on a different axis from the one that appeared to be going out of time.
During fault finding all mechanical components were checked (on the axis we thought had the problem) thus leaving only the electrical servo components to be in question. this is where the question 'is it possible for an AB kinetic drive to loose encoder pulses and not fault out'

 

[rdub]

To specifically answer your question, yes, encoder pulses can be lost and not result in an axis fault. If the "Motor Feedback Noise" fault action is set to "Status only", rather than "Disable Drive", and noise is present with your encoder signals, pulses could be lost resulting in positional drift while the servo remains fault free.