Lenze PositionServo 940, User Manual

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S94P01B
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9. Continue to increase the P-gain until the position error stop decreasing.
You will need to increase the D-gain again while increasing the P-gain to
suppress the oscillations.
10. Stop the program.
11. The above method is suggested as a general guideline for position tuning.
You will have to experiment with the gains to achieve the performance and
stability needed for your individual application.
12. The general goal of tuning is to achieve the minimum acceptable position
error while still maintaining stability. By increasing the P-gain you increase
the response to position change and reduce the position error. At the same
time a large P-gain can lead to instability, oscillation. By increasing the
D-gain you improve the stability of the system. Generally, both P-gain and
D-gain should be increased together.
13. While the program is stopped, edit the “TuneP” User Program and set the
Accel and Decel variables to the maximum values your system can accept.
Compile and load the program to the drive.
14. Set oscilloscope channel 1 to “Iq current”. Set the scale to the appropriate
value to see a full current pulse.
15. Observe that current, Iq, waveform. Check to make sure that there isn’t any
significant oscillation at the flat portion of the waveform. If so then decrease
the P-gain to a level where the oscillation either disappears or is very small.
(See pictures in section 9.2).
16. Trying to minimize the position error during the steady state of the move is
where the I-gain comes into play. The same is true for holding the position
accuracy. Increasing the I-gain will increase the drive’s reaction time while
the I-Limit will set the maximum influence that the I-Gain will have on to
the loop. When adjusting the I-gain start with a very small value for both
the I-gain and the I-Limit then increase the I-gain until stand-still reaction is
compensated. Remember that large values of Position I-limit can cause large
instability and unsettled oscillation of the mechanism.
Note
Remember that these are only initial settings for your system. Your ap-
plication will likely require fine-tuning. To optimize settings you will need
to experiment with combinations of all gains P, I and D and the I-limit.