Diagnostic variables

The following diagnostic variables are available via the user interface:

  • Error/warning (xError, xWarning)
  • If the distance between the motor encoder and external encoder exceeds an error/warning window, xError/xWarning is triggered.
  • Current coupling error (lrErrorDistance, lrWarningDistance)
  • The current coupling error represents the current difference between motor encoder information and external encoder information after the last reset, e.g. by starting up the MOVI-C® CONTROLLER or xDeleteDistance.
  • Current monitoring window (lrActErrorWindow, lrActWarningWindow)
  • The monitoring windows show the currently permitted distance between the motor encoder and the external encoder. This distance is the sum of the absolute error/warning window and the relative error/warning window. See Positive encoder coupling and Frictional encoder coupling.
  • Maximum available distance (lrMaxMagnitudeDistance)
  • The maximum deflection of the coupling error is continuously stored (lrMaxMagnitudeDistance) and can be read out to see whether anything has changed in the encoder coupling behavior over time. This value is deleted after an error reset, after xDeleteDistance or after the PLC is restarted.
  • Current slip (lrActSlip)
  • The current slip can be measured with lrActSlip. It is important that the lrSlipRelationErrorWindow is selected to be greater than the slip to be measured. If the lrSlipRelationErrorWindow is selected smaller, the coupling error is not attributed entirely to the slip, but is added up as an absolute coupling error until the lrAbsoluteDistanceWindow is exceeded. The following definition applies to drive slip:
  • (ω = speed of motor encoder, ω0 = speed of external encoder)
  • Positive/negative constant velocity in the plane (classic friction)
  • At constant speed in the plane, friction always results in a positive slip, as the motor always turns slightly faster regardless of the direction.
  • Constant uphill/downhill travel or acceleration/braking
  • Traveling uphill or accelerating typically generates positive slip. Traveling downhill or braking typically generates negative slip. The calculation of the current slip (lrActSlip) is unreliable at low speeds. To obtain a reliable value after speed standstill or reversal of direction of rotation, you should wait until the slip period (lrSlipDistancePeriod) has elapsed at least once.
  • Slip period completed (xSlipDistanceDeleted)
  • When a slip period is completed, xSlipDeleted is set to "TRUE" for one controller cycle and the current slip distance is reset.