Rockwell Automation 20D PowerFlex 700S with Phase I Control Reference Manual - Manual (Page 86)

86 Rockwell Automation Publication PFLEX-RM002D-EN-E - August 2013
Chapter 1 Detail Drive Configuration and Operation
There are two offsets, parameters 753 [Posit Offset 1] and 754 [Posit Offset 2].
The offset speed must be entered in parameter 755 [Posit Offset Speed] - if this is
left at zero the move will not occur. The position offset must be entered in counts
of feedback because it is added to the position reference after the EGR scaling.
Offsets must be maintained to keep the position (i.e., if you enter a 300 in the
offset the position loop will move 300 counts extra). If you zero the offset
command the motor will return to the previous position. When it is necessary to
zero the offset after a move without returning to the previous position, set
parameter 740 [Position Control] bit 5 “Xoff ReRef ” = 1. Then set the offset
value = 0. Then set [Position Control] bit 5 “Xoff ReRef ” = 0. The system will
not make an offset move when [Position Control] bit 5 “Xoff ReRef ” is on.
Position Loop Output Limits
Parameter 775 [Xreg Spd LoLim] sets the negative speed limit at which the
position regulator will output. The default is set to -10% of the base motor speed.
Parameter 776 [Xreg Spd HiLim] sets the positive speed limit at which the
position regulator will output. The default is set to +10% of the base motor
speed.
In position follower, the position loop only needs to trim the speed a small
amount because the drive is setup to follow the master speed reference.
Therefore, [Xreg Spd LoLim] and [Xreg Spd HiLim] can be left at the defaults.
Tuning Tips
The speed regulator of the drive must be tuned prior to tuning the Position Loop.
See Speed PI Regulator on page
120 for tips on tuning the speed regulator.
Typically parameter 768 [PositReg P Gain] should be set between 1/5th to 1/3rd
of parameter 90 [Spd Reg BW].
Parameter 768 [PositReg P Gain] may be set higher using lead compensation on
the Position Regulator Output. Lead/Lag filtering of the position regulator
output is accomplished via the speed trim 2 filter. Set parameters 25 [Strim2 Filt
Gain] and 26 [SpdTrim2 Filt BW] so that:
For example, with parameter 90 [Spd Reg BW] = 40 rad/sec, set parameter 26
[SpdTrim2 Filt BW] = 200 rad/sec and set parameter 25 [Strim2 Filt Gain] = 5.
The lead/lag filter will effectively cancel the 1/40 second lag. This will allow a
higher [PositReg P Gain] for increased stability.
BW] Reg [Speed
Gain] Filt [Strim2
BW] Filt [SpdTrim2
=