Home Position Drift

[Switchcraft]

Whenever I make repeated 2-axis straight line (or vector-space) movements, my home positions drift. My home positions are at a specific offset from my reverse stop sensors. I never noticed the home positions drifting when I did single axis straight-line movements, but now I am seeing significant drift (.5 in) after making 10 2-axis movements to a position (3 in.) and back again. Any thoughts?

[Jochen]

Could you please provide information about your system (motion controller, drive, motor, closed or open loop operation, mechanical setup, move parameters,...)?

Thanks,

Jochen Klier

National Instruments

[Switchcraft]

Nook actuators, Lin Engineering 5718L-01S 1.4A motors, RMS Technologies R325 motor drivers, NI-PXI-7330 motion controller, NI-PXI-7774 motion controller interface.

I confirmed last night that I do not have the same problem making the same movements with each axis individually. I cycled the system on both axes over 100 times without a smidgen of drift. However, when I make just a few movements as a 2D vector move (or as two simultaneous 1D moves), I get lots of drift. Encoder is enabled and active. Both the 1D moves and the 2D moves were constructed using the NI motion examples.

[Jochen]

Thank you for the additional information. You have said, that the encoders are active but not if you are running the axes in closed loop mode or open loop mode. Could you please clarify this? When the drift occurrs, do you see a following error (only valid for closed loop)? What happens when the drift occurrs in terms of differences between steps generated and encoder steps measured?

It's quite hard to understand what's going on, but I only can see two options: Either the step signal gets disturbed or the encoder signals. Something like that could happen because of problems with very high noise levels or because of wiring issues. Could you provide a wiring diagram?

Jochen