Rockwell Automation Publication PFLEX-RM003E-EN-E - January 2011 117
Detailed Drive Operation Chapter 1
Process PI Loop
The drive has a process PI loop that can be used to trim speed, torque, or other
functions.
Process PI Reference and Feedback
The process PI reference and feedback signals are the values set in parameters 181
[PI Reference] and 182 [PI Feedback], respectively. [PI Reference] could be a set
value or linked to a variable parameter such as an analog input. Typically [PI
Feedback] is linked to an analog input value received from a process line
transducer.
The process PI reference and feedback values are compared and an error signal is
created. This error signal is sent to a low pass filter. The filter bandwidth is set by
parameter 184 [PI Lpass Filt BW] in radians/second. The output of the filter is
sent to the process PI regulator.
Process PI Regulator
Parameter 185 [PI Preload] presets the process time. When the PI output is
enabled, the integral term of the process regulator will be preset to start
parameter 180 [PI Output] at the value set in [PI Preload].
Parameter 187 [PI Integ Time] is the integral term for the regulator. It is in units
of 1/seconds. For example, when the [PI Integ Time] is 2, the integrator output
equals 1 per unit in 1 second for 1 per unit error. 1 per unit means 100%.
155 1
151 12
&
157 31
OR
153 23
181
182
184
P Gain
kp
186
185
187
188
189
191
192
180
190
LPass
Filter
Limit
0
1
Logic Status
(Running)
Logic Command
(PI Trim En)
Logic Ctrl State
(ProcsTrim En)
Control Options
(PITrim EnOut)
PI Reference
PI Feedback
PI Lpass Filt BW
PI Preload
PI Integ Time
PI Prop Gain
PI Integ HLim
PI Integ LLim
PI Integ Output
PI High Limit
PI Lower Limit
PI Output
0
183 PI Error
+
+
+
-
Logic Command
(PI Trim Hold)
(PI Trim Rst)
151 14
15
I Gain
ki
s
Limit
Typically
Linked to P22
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