Rockwell Automation Publication 750-AT006D-EN-P - January 2022 71
Chapter 4 Auto Tuning
10:910 [Autotune] = InertiaTotal (5) – Enables the Autotune function to perform the Total Inertia Test. After selecting this value, you must
issue a start command to begin the test. This test initiates momentary rotation of the motor and load to measure total inertia and calculate
10:901 [Load Ratio]. When possible, perform Autotune at the point of lowest mechanical inertia on variable inertia loads, such as winders.
The total inertia test is an effective way to determine load ratio for existing applications where R > 0 is known or manually calculated.
However, a load ratio R = 0 is often all that is required to achieve relatively high performance and this test is often not required. As a result,
it is strongly advised to first run the drive with the recommended default settings before this test is conducted, as it typically produces
desired performance. See Recommended Default Settings
on page 58 for more information. Then run this test if the load requires additional
tuning to further optimize performance.
Gain Calculation
The term out-of-box refers to default control loop gain settings that are pre-configured in a new drive. Because the load is unknown at this
point, the motor is assumed to be unloaded, the load ratio R = 0, and the load coupling is compliant. This value also applies to when the load
is known to be compliant. See Out-of-Box Tuning
on page 55 for more information when R = 0.
However, when the load is known or an autotune total inertia test has been performed to determine the load ratio, the control loop gains are
configured for a load ratio R > 0 and the load coupling is rigid. This chapter pertains to when the load ratio R > 0.
These settings are the primary difference affecting out-of-box and autotune rules. Thus, the term out-of-box implies a compliant load with
R = 0 and the term autotune implies a rigid load with R > 0.
This section includes:
• Modes
on page 71
• Configuration on page 72
Modes
The following Autotune modes perform Bandwidth Calculations. Some modes perform inertia tests before bandwidth calculations because
bandwidth calculations use 10:900 [Motor Inertia] and 10:901 [Load Ratio] in their computation.
10:910 [Autotune] = BW Calc (6) – Enables the Autotune function to perform Bandwidth Calculations, which means that the drive calculates
control loop gains and dynamic limits. When R = 0, the gains are calculated according to Out-of-Box Tuning Gain Calculation
on page 55.
When R > 0, the gains are calculated according to Auto Tuning Gain Calculation
on page 71.
10:910 [Autotune] = JMtr BW Calc (7) – Enables the Autotune function to perform a Motor Inertia Test followed by the Bandwidth Calculations.
After selecting this value, you must issue a start command to begin the test. Perform this test with the load disconnected
from the motor.
Because the Motor Inertia test sets R = 0, the gains are calculated according to Out-of-Box Tuning Gain Calculation on page 55. This test
works well for most applications.
10:910 [Autotune] = JTotalBWCalc (8) – Enables the Autotune function to perform a Total Inertia Test followed by the Bandwidth Calculations.
After selecting this value, you must issue a start command to begin the test. Perform this test with the load connected
to the motor. Because
the Total Inertia Test sets R > 0, the gains are calculated according to Gain Calculation
on page 71. This test works well for high-performance
rigid loads.
After an Autotune bandwidth calculation, adjust 10:2112 [Trq NF Freq LLim] to a value that is at least 2…3 times the value of
10:906 [System BW].
IMPORTANT This test is only an option if motion can be initiated to rotate the load during the test. It must be performed with the
load connected
to the motor to generate accurate results. Otherwise the test measures motor inertia instead of total
inertia and incorrectly uses it to calculate load ratio. Also, the calculation assumes 10:900 [Motor Inertia] is accurate.
If you get an error that results from a negative load ratio, the motor inertia is incorrect and must be reduced.
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