User Manual
Appendix D
GFK-1742F
Jan 2020
Tuning Digital and Analog Servo Systems
420
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 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 a Series 90-30 CPU with firmware release 10.0 or later, or a
PACSystems RX3i CPU (version 2.8 or later).
2.
DSM support for Beta M1 and Beta M0.5 motors requires DSM firmware version 3.0
or later.
3.
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.
4.
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 host controller
sweep to re-enable the drive.
5.
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.
6.
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 sweep to clear the error.