Commissioning The Function - Siemens SINAMICS S120 Function Manual

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Function modules

9.12 Moment of inertia estimator

Saving the results permanently

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.

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 following restrictions apply for the "Moment of inertia estimator" function:

● The moment of inertia estimator only provides the correct total moment of inertia if the load

does not change during the acceleration or deceleration 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.

The following remedial measures are also to be observed in this regard:

Commissioning the function

In the servo control mode, the Online tuning (Page 114) function activates the "Moment of

inertia estimator" function automatically.

If the friction torque changes considerably with

the speed, ...

you can accept and activate the "Friction char‐

acteristic" function with the parameters p3820ff,

p3842 and p3845. This will allow speed depend‐

ency for the friction to be taken into account in

accordance with the friction characteristic.

Function Manual, 06/2019, 6SL3097-5AB00-0BP2

Drive functions