User Manual

Rockwell Automation Publication 20B-UM002G-EN-P - July 2014 125
Application Notes Appendix C
• Limits
Many threshold values can affect the performance of the profile/indexer.
To help minimize the possibility of overshooting a position, ensure that
the following parameters are set for the best performance.
Position Loop Tuning
Two parameters are available for tuning the position loop.
• [Pos Reg Filter], parameter 718 is a low pass filter at the input of the
position regulator.
• [Pos Reg Gain], parameter 719 is a single adjustment for increasing or
decreasing the responsiveness of the regulator.
By default these parameters are set at approximately a 6:1 ratio
(filter = 25, gain = 4). It is recommended that a minimum ratio of 4:1 be
maintained.
Profile Command Control Word
The profile/indexer is controlled with [Pos/Spd Prof Cmd], parameter 705. The
bit definitions are as follows:
No. Parameter Description
153 [Regen Power Limit] Default is –50% and will likely require a greater negative value. A brake or
other means of dissipating regenerative energy is recommended.
147 [Current Lmt Sel] By default these parameters are set to provide 150% of drive rating. If
lowered, the performance can be degraded.
148 [Current Lmt Val]
161
162
[Bus Reg Mode A]
[Bus Reg Mode B]
The default setting will adjust frequency to regulate the DC Bus voltage
under regenerative conditions. This will most likely cause a position
overshoot. To resolve this, select “Dynamic Brak” and size the load resistor
for the application.
Bit Name Description
0 Start Step 0 The binary value of these bits determines which step will be the starting step for the profile when
a start command is issued. If the value of these bits are not 1-16 the drive will not run since it does
not have a valid step to start from. Valid Examples: 00011 = step 3, 01100 = step 12
1Start Step 1
2Start Step 2
3Start Step 3
4Start Step 4
5-7 Reserved Reserved for future use
8 Hold Step When set, this command will inhibit the profile from transitioning to the next step when the
condition(s) required are satisfied. When the hold command is released, the profile will transition
to the next step.
9Pos
Redefine
This bit is used to set the present position as home. When this bit is set, [Profile Status] bit At
Home will be set and the [Units Traveled] will be set to zero.
10 Find Home This bit is used to command the find home routine.
11 Vel Override When set, the velocity of the present step will be multiplied by the value in [Vel Override].
12-
31
Reserved Reserved for future use