Stability Of The Speed Control Loop; Lower And Upper Limit Frequencies - Siemens SINAMICS S120 Function Manual

Servo control
5.9 Autotuning
Start value of the adaptation
The frequency with which the adaptation starts at the pulse enable is always the current
blocking frequency of the filter. It can be read in parameter r5285 and in the frequency
parameters of the filter. After a pulse inhibit and renewed pulse enable, this start value is always
the blocking frequency last determined before the pulses were inhibited. After switching the
drive off and on, the adaptation starts with the frequency stored in the frequency parameters of
the adapted filter.
You have the following options in order to find a suitable start value for the frequency of the
adaptation:
● Use the current position of the resonant frequency as start value:
– To do this, read the current resonant frequency from the frequency response
– Determine the current resonant frequency from one cycle of the "One Button Tuning".
OR
● Use 500 Hz as start value.
The start value may be above or below the sought resonant frequency. This value should be set
as blocking frequency of the respective band-stop filter before the adaptation is activated and
the pulse enable set.
5.9.3.1

Stability of the speed control loop

Moving the band-stop filter changes the phase and amplitude frequency response of the speed
control loop. The stability of the speed control loop is not checked by the current setpoint filter
adaptation. If the current setpoint filter adaptation is operated with activated online tuning
(p5300 = 2), the parameter settings that guarantee the stability are made automatically.
If autotuning is not activated, the settings that prevent instability must be made by the user. You
must also ensure a sufficiently large phase reserve. The phase or amplitude frequency
response of the adapted filter and the lower limit frequency of the adaptation (p5282) must be
taken into consideration during this.
A resonant frequency can be moved by the active control. An instability of the controller can be
caused by too high a controller gain that has a higher amplitude than the mechanical resonant
frequency and therefore influences the adaptation.
5.9.3.2

Lower and upper limit frequencies

Parameter p5283 for the upper limit frequency has an internal upper limit that is only effective
with active adaptation and depends on the settings for the adapted current setpoint filter. The
following applies:
● If the adaptation is active, p5283 is limited immediately to this internal value when written.
● If the adaptation is not active, p5283 is automatically limited to the internal value when the
adaptation is activated.
124
measurement.
OR
Function Manual, 06/2019, 6SL3097-5AB00-0BP2
Drive functions