APR Fault Generation

APR Faults can be generated:
  • During initial axis configuration.
  • During operation
  • When the system fails to recover the absolute position after a power cycle, reset, or a reconnection.
APR faults are detected during these online scenarios.
  • Initial configuration (download)
  • Reconnection of the drive axis
  • Change in any of the axis attributes which impacts the absolute machine position.
When an APR fault occurs, the actual position of the axis is set to the feedback reference position of the axis. The values are read from the absolute encoder. The axis homed status bit clears.
A download, restore from a CompactFlash card, a restore from a Secure Digital Card, or a
ControlFLASH
 firmware update after one of these events causes the APR fault.
  • Axis Configuration
  • Attribute Changes
    • Offline edits of the axis attributes or configuration do not cause an APR fault until after download occurs.
    • Online edits of certain attributes will result in an immediate APR fault. Changing the axis feedback device or feedback polarity without downloading the project will also generate an immediate APR fault.
  • Axis hardware change or malfunction
    • Enabling certain axis features (for example, extended position feedback) via drive firmware update.
  • Axis hardware resource insufficiency
    • Hardware resource insufficiencies are only detected during download or
      ControlFLASH
       firmware update and will result in an APR fault.
During axis configuration, the following checks are made:
  1. Existing Axis?
  2. Scaling Signature matches saved Scaling Signature?
  3. Feedback Signature matches saved Feedback Signature?
If these three checks pass, absolute position is restored.
During operation, the system monitors the following conditions:
  1. Feedback Integrity Status bit cleared?
  2. Scaling Signature dependent attribute values changed by SSV?
Changes to the following attributes do not impact the Scaling Signature or result in the loss of the absolute machine reference and therefore do not generate an APR Fault.
  • Conversion Constant
  • Position Unwind
  • Travel Mode
Care must be taken when changing these values so that the new values are related to the Position Unit of the product and the mechanics of the system. Value changing is typically done as part of a product recipe change.
If the Axis Homed status bit is clear, indicating that position has not been referenced to the machine, the APR function is bypassed and there is no attempt to restore absolute position.
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