User Manual V 1-4.XX User guide

Understanding the Auto-tuning Procedure 13-13
Important: When you change either Kp Speed Loop or Ki Speed
Loop, the 1336 IMPACT drive places the bandwidth value at zero.
This turns off the automatic calculation of gains based on the setting
of Spd Desired BW (parameter 161). The regulator then uses the
custom Ki and Kp gain values that you entered. To return to automatic
tuning of Ki and Kp, enter a non-zero bandwidth in Spd Desired BW.
If possible, you should use automatic tuning.
Adjusting the Kf Gain
In addition to the Ki and Kp regulator gains, a third gain term has
been included. This gain is represented by Kf Speed Loop
(parameter 160). The Kf gain affects speed overshoot in response to a
step change in speed reference. You can adjust the Kf gain parameter
at any time, independent from the proportional and integral gains. The
drive chooses the default setting of Kf based on Fdbk Device Type
(parameter 64) when the inertia test is performed. A Kf setting of 1.0
makes the control act like a conventional proportional-integral type
regulator. You can set the Kf gain manually, based on overshoot:
Checking the Auto-tune Status You can use Autotune Status (parameter 156) to view various
conditions related to the auto-tune feature.
Autotune Status is defined as follows.
file:
Control
group:
Speed Regulator
When Kf is: Then:
1.0
The speed loop acts like a normal PI loop with the overshoot equaling approximately 13%. This is the default setting for
encoder-based systems.
0.7
The overshoot is typically less than 1%. 0.7 is the recommended operating point. This is the default setting for
encoderless systems.
0.5 The response becomes underdamped with no overshoot. 0.5 is the lowest recommended value.
file:
Autotune
group:
Autotune Status
If this bit is set: Then:
0
Executing
A test is currently executing.
1
Complete
The test has finished executing.
2
Fail
The test failed.
3
Abort
A stop command was issued before the test completed.
4
Flux active
The drive must not be running when auto-tune is requested.
5
Not Ready
The ready input is not present.
6
Not Zero Spd
Generally, this bit is set in two cases:
• If the motor rotates during this test, an improper result is likely. Make sure the motor (decoupled from load or process)
is not rotating just before or during the test.
• If the motor is not rotating during this test, then investigate electrical noise creating encoder transitions. Improper
encoder grounding or a noisy encoder power supply could cause noise.
If your motor does rotate during this test, consult the factory.