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126 Unidrive M702 User Guide
Issue Number: 3
Speed loop gains (cont)
(Pr 00.007 {03.010}, Pr 00.008 {03.011}, Pr 00.009 {03.012})
There are three methods of tuning the speed loop gains dependant on
the setting of Pr 03.017:
1. Pr 03.017 = 0, User set-up.
This involves the connecting of an oscilloscope to analog output 1 to
monitor the speed feedback.
Give the drive a step change in speed reference and monitor the
response of the drive on the oscilloscope.
The proportional gain (Kp) should be set up initially. The value
should be increased up to the point where the speed overshoots and
then reduced slightly.
The integral gain (Ki) should then be increased up to the point where
the speed becomes unstable and then reduced slightly.
It may now be possible to increase the proportional gain to a higher
value and the process should be repeated until the system response
matches the ideal response as shown.
The diagram shows the effect of incorrect P and I gain settings as
well as the ideal response.
2. Pr 03.017 = 1, Bandwidth set-up
If bandwidth based set-up is required, the drive can calculate Kp and
Ki if the following parameters are set up correctly:
Pr 03.020 - Required bandwidth,
Pr 03.021 - Required damping factor,
Pr 03.018 - Motor and load inertia.
The drive can be made to measure the motor and load inertia by
performing an inertia measurement autotune (see Autotune
Pr 00.040, earlier in this table).
3. Pr 03.017 = 2, Compliance angle set-up
If compliance angle based set-up is required, the drive can calculate
Kp and Ki if the following parameters are set up correctly:
Pr 03.019 - Required compliance angle,
Pr 03.021 - Required damping factor,
Pr 03.018 - Motor and load inertia.The drive can be made to
measure the motor and load inertia by performing an inertia
measurement autotune (see Autotune Pr 00.040, earlier in this
table).
4. Pr 03.017 = 3, Kp gains times 16
If Speed Controller Set-up Method (03.017) = 3 the selected
proportional gain used by the drive is multiplied by 16.
Speed demand
Insufficient proportional
gain
[]00.007
Excessive proportional
gain [00.007]
Excessive integral gain
[00.008]
Ideal response
5. Pr 03.017 = 4 - 6
If Speed Controller Set-up Method (03.017) is set to a value from 4 to
6 the Speed Controller Proportional Gain Kp1 (03.010) and Speed
Controller Integral Gain Ki1 (03.011) are automatically set up to give
the bandwidths given in the table below and a damping factor of unity.
These settings give low, standard or high performance.
Speed Controller
Set-up Method
(03.017)
Performance Bandwidth
4 Low 5 Hz
5 Standard 25 Hz
6 High 100 Hz
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