User`s manual
Startup and Tuning
GFK-1742A Appendix D Tuning GE Fanuc Digital and Analog Servo Systems D-3
D
11. Monitor servo performance and use the
Jog Plus
and
Jog Minus
%Q bits to move the
servomotor in each direction. Placing the correct command code in the % AQ table can
temporarily modify the
Position Loop Time Constant
. For most systems the
Position Loop
Time Constant
can be reduced until some servo instability is noted, then increased to a value
approximately 50% higher. Once the correct time constant is determined, the DSM314
configuration should be updated using the configuration software.
Velocity Feedforward
can
also be set to a non-zero value (typically 90 – 100 %) for optimum servo response. Refer to
Tuning a GE Fanuc Digital Servo
for information on setting the
digital servo
Velocity Loop
Gain
.
12. If Follower mode is used with an Incremental Quadrature Encoder, confirm that
Actual
Position
(Aux Axis 3) represents the encoder position.
Make sure the desired Follower axis
slave : master ratio has been programmed as the A:B ratio using the configuration
software
.
Digital Servo System Startup Troubleshooting Hints
1. The DSM314 requires PLC firmware release 10.0 or greater and VersaPro software release
1.10 or greater.
2. The default DSM314 configuration for the
Overtravel Limit Switch
inputs is ENABLED.
Therefore, 24 vdc must be applied to the Overtravel inputs or the DSM314 will not operate.
If Overtravel inputs are not used, the DSM314 configuration should be set to
Overtravel
Limit Switch
inputs DISABLED.
If the
Axis Enabled
%I bit is OFF, the axis will not respond to any %Q bits or %AQ
commands.
When a servomotor is not used with a Servo Axis, the
Motor Type
must be set to
0 or
Axis Enabled
will stay OFF. A
Motor Type
of 0 disables the axis servo loop processing
and sets
Axis Enabled ON
, allowing the axis to accept commands such as
Load Parameter
Immediate
and
Set Analog Output Mode
.
3.
The
Enable Drive
%Q control bit must be set continuously to ON or no motion other
than Jogs will be allowed.
If no STOP errors have occurred, the
Drive Enabled
%I status bit
will mirror the state of the
Enable Drive
%Q bit. A STOP error will turn off
Drive Enabled
even though
Enable Drive
is still ON. The error condition must be corrected and the
Clear
Error
%Q control bit turned ON for one PLC sweep to re-enable the drive.
4. If the
Module Error Present
%I status bit is ON and the
Axis Enabled
and
Drive Enabled
%I
status bits are OFF, then a STOP error has occurred (Status LED flashing fast).
In this state,
the Servo Axis will not respond to any %Q bits or %AQ commands other than the
Clear
Error
%Q bit.
5. The
Clear Error
%Q control bit uses one-shot action. Each time an error is generated, the bit
must be set OFF then ON for at least one PLC sweep to clear the error.
6. The CFG OK LED must be ON or the DSM314 will not respond to PLC commands. If the
LED is OFF then a valid DSM314 configuration has not been received from the PLC, or there
may be a recognized configuration error. Check the %AI error code words for Dxxx errors,
which are documented in the “System Error Codes” section of Appendix A. Also check the
PLC fault tables for reported configuration errors.