Rockwell Automation 1398-PDM-xxx IQ Master Version 3.2.4 for IA-2000 and IQ-5000 Positioning Drive Modules, IQ-55 - Manual (Page 81)

Run Menu • Tune 59
Publication 1398-PM601A-EN-P — October 2000
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high gain settings. This could cause instability when returned to the closed loop mode of operation. The
conditions are:
Max Distance or Max Velocity set too low. Either of these conditions can cause very rapid reversal of
the servo motor and audible vibration. Increase Max Distance or Max Velocity.
Step current set too low. This is shown by the lack of servo motor motion. Increase Step Current.
If the gains are set to the maximum value, repeat the Auto Tune process with higher values for Step Cur-
rent, Max Distance, and Max Velocity.
After the Auto Tune process is complete, if further fine tuning of the gains is required, choose the Man-
ual Tune button to run Manual Tune. If you are satisfied with the new gain settings, choose the OK but-
ton to save the settings and exit. If not, choose the Reset Gains button to restore the gains to the previous
settings. The previous settings can be restored only if you have NOT chosen the OK button. The Cancel
button is similar to the Reset Gains button except that it will exit Auto Tune.
Manual Tune
The Manual Tune mode provides a means of tuning the velocity and position control loops indepen-
dently. The inner velocity loop must be tuned first, as this tuning will affect the position loop response.
This procedure assumes that the system, including the machine the motor is connected to, can tolerate
small-signal step velocity changes.
The tuning of the velocity regulator is accomplished by changing the parameters PGAIN, IGAIN, and
FILTER. PGAIN is the proportional gain of the velocity regulator. Increasing PGAIN reduces the time
required to reach the commanded velocity. IGAIN is the integral gain of the velocity regulator. Integra-
tion in the velocity regulator forces the motor velocity to precisely follow the commanded velocity with
no error under steady state conditions (no changes in velocity command or load). Increasing IGAIN
increases the stiffness, or the ability to reject load disturbances. Increasing IGAIN also, however,
increases the amount of velocity overshoot when responding to a step change in velocity. Too much
IGAIN can cause the system to go unstable. To reduce stress on the mechanical parts of the machine,
PGAIN and IGAIN should be set as low as possible while still maintaining the desired performance.
To Tune the Velocity Loop using Manual Tune
1. Follow the Auto Tune procedure to provide a nearly optimal starting point for tuning.
2. Disable the ULTRA Plus or IQ.
3. From the Monitor menu, set the Programmable Monitor output to VEL1, the default setting.
4. Connect an oscilloscope to the Programmable Monitor output (P3-7) and to analog common (P3-4).
5. Select Tune from the Run menu, then choose the Manual Tune button if in Auto Tune.
6. Select Velocity Step as the Command Type. The Command Type can be either Velocity Step to tune
the velocity loop or Position Step to tune the position loop. The velocity loop should ALWAYS be
tuned first before tuning the position loop as the velocity tuning affects the position loop response.
7. Set the Direction radio button to Bidirectional, Positive, or Negative. The Direction setting deter-
mines the direction of motion during the Manual Tune process. The positive direction is defined as
clockwise rotation of the motor shaft when facing the motor shaft end.
8. Set the Step Velocity to the desired step velocity of the internal square wave generator. (A good
value is between 100 and 500 RPM.) An excessive Step Velocity or a low ILIMIT setting can cause
the servo amplifier to enter current limit which should be avoided while tuning the ULTRA Plus or
IQ. If the ULTRA Plus or IQ reaches current limit, “In Peak Current” is displayed.
9. Set the Cycle Period value. Do not set the Cycle Period to a high value (one that would allow the
system to reach the end of travel) or to a value less than 0.02 seconds. The Cycle Period is the time
in seconds to complete one cycle of the command. If the Direction is set to Bidirectional, one cycle
is a move forward and back. If the Direction is either Positive or Negative, one cycle is the move in
one direction only.
10. Set the ILIMIT value. ILIMIT is the current limit used during Manual Tune. It is set equal to the
ILIMIT parameter when Manual Tune mode is first entered. ILIMIT can be changed here without
changing the ILIMIT parameter.