Parker ACR9000, Installation Manual

Page: 103 / 198

Parker Hannifin
Feedback Device Problems
Several controller parameters may need additional configuration to work with
different types of feedback devices. The
MULT
command affects feedback
polarity; the
ENC SRC
command selects the interpretation of encoder inputs.
If the feedback position does not change correctly, check the following:
•
Confirm that the feedback cables are wired correctly.
•
If the ACR9000 (or ACR9030) +5 VDC powers the feedback device,
verify that the device is designed to be powered from +5 VDC and
meets the current rating in Table 12 Axis Power Electrical
Characteristics, on page 37.
•
If the ACR9000 (or ACR9030) +5 VDC powers the feedback device
and/or drive I/O, verify that a short circuit in the feedback device
and/or cabling has not tripped the internal protection circuit. When the
short-circuit event is removed, the internal protection circuit will
automatically reset and apply power.
• The ACR9000 (or ACR9030) directly supports feedback devices with
differential signaling (RS-422/RS-485). Single-ended feedback devices
require external circuitry to be compatible with the ACR9000 (or
ACR9030). For more information, see “Differential and Single-Ended
Encoders” on page 86.
• Noise in the system can cause missed and/or false position values.
Try to isolate the cause by removing one component at a time.
•
Exceeding the maximum feedback frequency can cause wrong
position values at high speeds. Peak frequency must account for
velocity ripple. For more information, see Table 20 Encoder
Electrical/Timing Characteristics on page 45.
•
SSI feedback—confirm that the servo period is correctly configured to
accommodate SSI setup and transfer time. For specifics, see Table 64
SSI Transfer-Cycle Timing Data, on page 111.
•
For a stepper axis with feedback, you must set the Stepper Feedback
flag in the Secondary Axis flags. For more information, refer to the
ACR Command Language Reference (Online Help System in the
ACR-View software).
•
The feedback device is counting backwards. Use either:
AcroBASIC remedy: Change the
MULT
command setting to 4
or –4 to reverse feedback polarity (not applicable for SSI feedback
devices).
Hardware remedy: Depending on the feedback device used, take one
of the following actions.
If your application can change how the feedback device is
mounted, you may be able to affect the count direction with it.
For Quadrature feedback, switch Encoder CHB+ and Encoder
CHB − between the controller and the feedback device.
For Step and Direction feedback, switch Encoder CHB+ and
Encoder CHB
−
between the controller and the feedback
device.
Chapter 4 Troubleshooting 103
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