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Rockwell Automation Publication 750-AT006D-EN-P - January 2022
Chapter 4 Auto Tuning
Configuration
Autotune bandwidth calculations consist of two things:
1.
The following dynamic limits are calculated based on 10:900 [Motor Inertia], 10:901 [Load Ratio], and motor nameplate parameters.
2. 10:906 [System BW] and 10:1010 [Alt Fb Gain Scale] are calculated, which triggers an automatic calculation of control loop gains.
The following parameters are used to calculate 10:906 [System BW], 10:1010 [Alt Fb Gain Scale], and the control loop gains.
Encoderless Mode: In Encoderless Mode, the drive adjusts the control loop gains based on a conservative 10:906 [System BW] of 2 Hz as
shown in
, independently of 10:902 [Load Coupling] settings.
The drive operates in Encoderless mode when either of the following are true:
•
The primary feedback (10:1000 [Pri Vel Fb Sel]) is set to the Open Loop Virtual Encoder.
•
The alternate feedback (10:1006 [Alt VelFb Sel]) is set to the Open Loop Virtual Encoder, parameter
10:1019 [Fb Loss Action] = Auto Tach SW (2), and a switchover condition happened due to encoder feedback loss fault.
10:2020 [LdObs Mode] – Configures the load observer feature. The following recommended settings are given based on control mode.
•
10:2020 [LdObs Mode] = Disabled (0) for torque mode applications
•
10:2020 [LdObs Mode] = LdObs Only (1) for Velocity mode applications
•
10:2020 [LdObs Mode] = LdObs VelEst (2) for Position mode applications
Parameter No. Parameter Name
Description
10:1392
[Max Speed Fwd]
The forward speed limit that is used by the position PTP planner.
10:1393
[Max Speed Rev]
The reverse speed limit that is used by the position PTP planner.
10:1898
[Vel Limit Pos]
The positive velocity limit that is placed on the velocity reference.
10:1899
[Vel Limit Neg]
The negative velocity limit that is placed on the velocity reference.
10:1965
[Accel Limit Pos] The positive acceleration limit on the velocity regulator output.
10:1966
[Accel Limit Neg]
The negative acceleration limit on the velocity regulator output.
10:2083
[Torque Limit Pos] The positive limit that is placed after the torque reference filters.
10:2084
[Torque Limit Neg] The negative limit that is placed after the torque reference filters.
Parameter No. Parameter Name
Description
10:907
[System Damping]
Sets system damping (Z) which adjusts position, velocity, and torque loop spacing of the calculated control loop gains and
load observer gains. It also adjusts the integrator spacing of the calculated gain parameters to generate the required
responsiveness.
10:902
[Load Coupling]
Reflects the type of mechanical
coupling between the motor and
load. It adjusts calculated control
loop gains during an autotune
bandwidth calculation test.
• 0:902 [Load Coupling] = Rigid (0) is where the load consists of few mechanical
components with direct connection to the motor shaft.
– The components are high performance, have no flex or twist, and misalignment is
not likely to occur.
– This setting is for high-performance machines. A loop spacing of 4Z
2
is sufficient
for rigid loads.
• 10:902 [Load Coupling] = Compliant (1) is a non-rigid load where position
misalignment, backlash, and flexing of couplings, gearboxes, belts, and shafts can
occur which creates an indirect connection of the load to the motor shaft.
– This setting is common for most machines. As a result, all gains reduce by an
additional factor of (R+1) to achieve a conservative stability margin over a large
class of possible systems.
– This setting can lead to a low system bandwidth which can then be manually
increased to achieve higher performance.
