Measuring The Function; Apc With Acceleration Feedback - Siemens SINAMICS S120 Function Manual

Function modules
9.14 Advanced Position Control (including Active Vibration Suppression)
● The weighting factor for encoder combination p3702 has, for compatibility reasons to
previous software releases, a default value of "1". For most applications, this value cannot
be activated. This value should be set to "0" before activating the encoder combination.
Negative values for p3702 are permissible. The oscillation is then shifted to lower
frequencies.
● The gain of the differential pressure feedback is set in p3768. This parameter has stiffness
units (Nm/rad). Practical values for this parameter are approximately the stiffness of the axis
itself. This value can differ at a different axes.
Example: The mechanics forms a two-mass oscillating system with an absorber frequency
of 20 Hz. The load moment of inertia is 0.01 kgm
● A highpass filter for the differential position feedback can be parameterized in parameter
p3767. For many applications, the default value is adequate and does not have to be
changed.
● In addition to the highpass filter, resonance damping can be set in p3774, which supports
the ruggedness and stability of the position differential feedback.
9.14.4.2

Measuring the function

Procedure
The following measuring functions can be used to measure encoder combination and position
differential feedback:
● Speed controlled system (only encoder combination visible)
● Speed controller reference frequency response
● Position controller reference frequency response
You can find detailed information on how to perform these measurements in Chapter
"Measuring frequency responses (Page 582)".
9.14.5

APC with acceleration feedback

Function description
For the "APC with acceleration feedback" function, the acceleration signal from a direct
measuring system is used to dampen the oscillations. This function can only be applied to
dampen oscillations which can be measured at the direct measuring system. If this is not the
case, an external acceleration sensor can be attached at an appropriate location within the
machine and used for APC. The function, for example, is ideal for axes for which the vibration
has a limited effect on the motor (e.g. because of a large transmission ratio or a strong gearbox
self-locking).
Frequently, when using a direct measuring system, high-frequency resonance points occur in
the range > 100 Hz in the control loop, which can result in significant problems when setting
APC. In cases such as these, the APC filter must be used in order to ensure control loop
570
. The stiffness is then given by:
2
Function Manual, 06/2019, 6SL3097-5AB00-0BP2
Drive functions