Inertia Estimator - Siemens SINAMICS S120 Function Manual

Function modules

8.12 Inertia estimator

8.12 Inertia estimator
Features
Note
The "Inertia estimator" function is activated exclusively for servo control via the "Inertia
estimator" function module.
The description is also valid for linear motion (torque -> force, moment of inertia, inertia ->
mass, speed -> velocity)
The "Inertia estimator" function is required when the moments of inertia of the drive change
considerably during operation (e.g. when using tools or workpieces with different moments of
inertia). For this situation, continuously repeating the rotating motor data identification to
determine the moment of inertia would be too complex, or impossible on a machine. The
inertia estimator is also required for the "Online tuning" function.
For encoderless operation, the total moment of inertia of the motor and driven machine must
be known. In controlled operation without encoder (for speeds less than p1755) in the
acceleration phase, it is not permissible that the motor stalls because of moment or inertia
that has been parameterized too small. In controlled operation without encoder (for speeds
above p1755), the speed/torque precontrol requires the precise moment of inertia in order to
achieve the optimal speed controller dynamic response. An incorrect moment of inertia at the
end of the acceleration phase, results in an undesirable overshoot or undershoot.
You can also activate the inertia estimator during operation with or without an encoder
(p1400.18, p1400.22). For operation with encoder (without online tuning), the moment of
inertia is only included in the motor control when the speed/torque precontrol has been
activated (p1402.4 = 1).
For operation with encoder (with online tuning), the relevant controller parameters for the
speed and position controller are set automatically. The automatic calculation of the
controller parameters also depends on the estimated moment of inertia.
Description
The load torque must first be determined to determine the moment of inertia.
Phases with constant speed not equal to zero are required to determine the load torque (e.g.
friction force). After determining the load torque, the moment of inertia can be determined in
the acceleration phases. For this the acceleration torque must be greater than
p1560 x p0333 and greater than 80% of the friction torque (0.4 x (p1563 - p1564)) and in
encoderless operation the speed value must also be greater than p1755 (controlled
operation). If the source of p1502 has a 1 signal, the moment of inertia is not estimated.
The accuracy of the moment of inertia estimation increases with the acceleration. The start
value of the moment of inertia estimator is the parameterized moment of inertia (p0341 x
p0342 + p1498).
If the load estimation has taken place and the moment of inertia does not settle
(r1407.24/26 = 0), then increasing the acceleration (p2572/p2573) is recommended.
542
Function Manual, (FH1), 04/2014, 6SL3097-4AB00-0BP4
Drive functions