User manual

Rockwell Automation Publication MOTION-UM003F-EN-P - March 2015 167
Commission Chapter 7
When configured for Load Observer operation, the Acceleration Estimate signal
represents the error between the actual acceleration as seen by the feedback
device and the acceleration that is estimated by the Load Observer that is based
on an ideal model of the motor and load.
By subtracting the Acceleration Estimate signal from the output of the
Acceleration Limiter, the Load Observer is forcing the actual motor and load to
behave like the ideal model, as seen by the velocity loop. The Acceleration
Estimate signal can be seen in this light as a dynamic measure of how much the
actual motor and load are deviating from the ideal model.
Such deviations from the ideal motor model can be modeled as torque
disturbances. Scaling the Load Observer Acceleration Estimate signal by the
System Inertia results in the Load Observer Torque Estimate signal. This signal
represents an estimate of the motor torque disturbance.
When configured for Acceleration Feedback operation, the Load Observer
Acceleration Estimate represents an acceleration feedback signal. Applying this
signal to the acceleration reference summing junction forms a closed acceleration
loop. Scaling the Load Observer Acceleration Estimate signal by the System
Inertia results in the Load Observer Torque Estimate signal. This signal
represents an estimate of motor torque.
Load Observer Configuration
The Load Observer can be configured in various ways by using the Load
Observer Configuration attribute. Choose ‘Load Observer Only’ when you want
to enable the Standard Load Observer function.
TIP
The Kinetix 350 and the Kinetix 5500 drives do not support all Load
Observer attributes.
Load Observer Only: Kinetix 6500 Drive
Load Observer Only: PowerFlex 755 Drive