Siemens SINAMICS S120 Function Manual page 586

Function modules
8.12 Moment of inertia estimator
The results of the moment of inertia and load estimator can be taken over by permanently
saving (RAM to ROM) after the system has settled (r1407.26 = 1). If there are no significant
changes to the moments of inertia, the inertia estimator can be deactivated after saving. The
appropriate signal can be read out of SINUMERIK as soon as the moment of inertia
estimator has settled.
Note
Online tuning for servo control
The values determined by the load and moment of inertia estimator are deleted by
deactivating (p5300 = 0) and then subsequently reactivating online tuning (p5300 = 2).
Restrictions
● The moment of inertia estimator only returns the correct total moment of inertia if the load
does not change during the acceleration phases.
● In phases where machining takes place during the speed setpoint change, e.g. thread
cutting, the moment inertia estimator can be frozen using 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. An excessively high
backlash (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.
● For operation without encoder, 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.
Note
Online tuning for servo control
For servo control and active online tuning, the speed controller is automatically adapted
with the estimated moment of inertia.
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Function Manual, 11/2017, 6SL3097-4AB00-0BP5
Drive functions