Siemens SINAMICS S120 Function Manual page 543

If the load moment of inertia is significantly greater than the motor moment of inertia, then
the transient event can also be improved via parameterization of the load moment of inertia
(p1498).
The results of the moment of inertia and load estimation can be taken over through saving as
non-volatile data (RAM TO ROM) after the transient event (r1407.26). If there are no
significant changes to the moments of inertia, the inertia estimator can be deactivated after
saving.
The values ascertained for load and inertia estimation are deleted by reactivating the online
tuning (p5300 = 2/0 SERVO only).
Restrictions
In phases where machining takes place during the speed setpoint change, e.g. thread
cutting, the inertia estimator can be frozen via a BICO switch (source of p1502 = 1). This
means that a previous moment of inertia that was correctly determined is not modified as a
result of an incorrect estimation. This condition is also violated when, for example, the friction
torque changes significantly with the speed. A backlash that is too large (no frictional
connection) and fast periodic movements that decouple the masses elastomechanically, can
also have a negative effect on the accuracy of the moment of inertia estimation.
The inertia estimator only returns the correct total moment of inertia if the load does not
change during the acceleration phases.
In encoderless operation the moment of inertia must be parameterized to the highest
expected moment of inertia (p0341 x p0342 + p1498), so that the motor does not stall when
accelerating for the first time in the controlled range. As long as the pulses are not deleted,
the actual estimated value of the moment of inertia is always used in the motor model. This
value is stored in r1493. The estimated moment of inertia is reset to the parameterized value
with each pulse inhibit, if p1400.22 = 0 is set. Otherwise, the last determined value is
retained at the pulse inhibit. An automatic adaptation of the speed controller with the
estimated moment of inertia is only performed with active online tuning (SERVO only).
Drive functions
Function Manual, (FH1), 04/2014, 6SL3097-4AB00-0BP4
Function modules
8.12 Inertia estimator
543