Rockwell Automation 1784-PM16SE SoftLogix Motion Card Setup and Configuration Manual - Manual (Page 380)

Publication 1784-UM003A-EN-P – June 2003
372 Motion Object Attributes
Enhancements have been made to the Logix tuning algorithm to address
excessive noise issues by managing quantization noise levels. The product of
the Tune Inertia (% Rated/MCPS) and the Velocity Servo BW (Hertz) can be
calculated to directly determine quantization noise levels. Based on this
product, the tuning algorithm can take action to limit high frequency noise
injection to the motor. These are the actions that have been implemented:
• For motors with a Tune Inertia BW product of 1000 or more, the LP
Filter will be applied with a Filter BW of 5x the Velocity Servo
Bandwidth in Hertz. This will limit the amount of phase lag introduced
by the LP filter to ~12 degrees which is relatively small compared to the
30 to 60 degrees of phase margin that we have for a typical tuned servo
system. With a typical tuned LP filter BW value of 200 Hz, we can
expect the high frequency quantization noise in the 1 KHz range to be
attenuated roughly by a factor of 5.
• When the Tune Inertia BW product reaches 4000 or more, the LP filter
alone is not going to be enough to manage the quantization noise level.
So the tune algorithm will begin to taper the system bandwidth by the
ratio of 4000/(Tune Inertia * Vel Servo BW). This will hold the
quantization noise level at a fixed value, independent of the Tune Inertia
BW product. For example, Dave's 420 motor with a Tune Inertia value
of 213 and a Vel Servo BW of 41 Hz (8733 Inertia BW product) will
tune with a Pos P Gain of 46 and a Vel P Gain of 117 and LP Filter BW
of 93. This he has found to be a good noise free gain set.
Servo Drive Configuration
Attributes The following sections define the behavior of all the various configuration
attributes associated with the Servo Drive data type of the Motion Axis
Object. The attributes, by definition, have read-write access. The Servo Drive
Configuration Attributes are divided into seven categories: Drive
Configuration, Motor and Feedback, Drive Gains, Drive Limits, Drive Offsets,
Drive Power, and Drive Commissioning attributes. These categories
correspond roughly to the organization of the RSLogix 5000 Axis Properties
pages.
Many of the following Drive Configuration attributes are associated with
corresponding attributes contained in the SERCOS Axis Object associated
with the 1784-PM16SE 16-Axis SERCOS interface module. When any of
these attributes are modified by a Set Attribute List service or an SSV
instruction within the user program, the local processor value for the attribute
is immediately changed and a Set Attribute List service to the SERCOS
interface module is initiated to update the working value stored in the drive.
The progress of this update can be monitored, if necessary, within the user
program through the Configuration Update in Process bit of the Axis Status
Bits attribute.