Moment Of Inertia Estimator - Siemens SINAMICS S120 Function Manual

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Function modules

9.12 Moment of inertia estimator

Moment of inertia estimator

The "Moment of inertia estimator" function is preferably applied for cases in which a constant

repetition of the rotating motor data identification for determining moment of inertia is either too

complex or is not possible.

Function description

The "Moment of inertia estimator" function is required for cases in which moments of inertia for

the drive change considerably during operation (e.g. when using tools or workpieces with a

different moment of inertia).

Application for linear motors

The "Moment of inertia estimator" function can also be applied for linear motors. The following

must be considered in the event of deviating designations for the relevant parameters:

● Force (linear) ≙ Torque (rotary)

● Mass (linear) ≙ Moment of inertia (rotary)

● Speed (linear) ≙ Speed (rotary)

Control mode

You can apply the "Moment of inertia estimator" function both in servo control mode and vector

control mode. The following applies:

● Servo control type

The "Moment of inertia estimator" is also required for the "Online tuning (Page 114)" function

in the servo control mode.

● Control mode vector

Moment of inertia precontrol (Page 545) can be configured for vector control. This is

especially advantageous for applications, where the moment of inertia cannot be calculated

as a result of a constant motor speed.

Operation with encoder

Operation with encoder is possible in both servo control mode and vector control mode. The

following applies for operation in servo control mode:

● For operation without online tuning activated, the moment of inertia is only effective in the

motor control if the speed pre-control or torque pre-control is activated (p1402.4 = 1).

● For operation with online tuning activated, the relevant controller parameters are set

automatically for speed controller and position controller. The automatic calculation of the

controller parameters also depends on the estimated moment of inertia.

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

Drive functions