Using Pi Control - YASKAWA Varispeed E7 Instruction Manual And Parameter Description

Using PI Control

PI control is a method of making the feedback value (detection value) match the set target value. By combin-
ing proportional control (P) and integral control (I), you can even control system with load fluctuation.
The characteristics of the PI control operations are given below.
P element The output of a P-element is proportional to the input (deviation). With using a P-element
alone it is not possible to eliminate the deviation completely.
I element The output of an I-element is the time-integral of the input (deviation). With using a P-ele-
ment and an I-element together the deviation can be eliminated completely.
PID Control Operation
To understand the differences between the PI control operations P and I the output share of each operation is
shown in the following diagram when the deviation (i.e., the difference between the target value and feedback
value) is fixed.
Deviation
Output of P- and
I-element
PI Control Applications
The following table shows examples of PI control applications using the Inverter.
Applica-
tion
Pressure
Pressure information is fed back and constant pressure control is performed.
Control
Flow Rate
Flow rate information is fed back and the flow rate is controled with high accuracy.
Control
Tempera-
Temperature information is fed back and a temperature adjustment control using a
ture Con-
fan can be performed.
trol
Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com
Fig 6.48 PI Control Operation
Control Details
Individual Functions
Time
PI control
I control
P control
Time
Example of Sen-
sor Used
Pressure sensor
Flow rate sensor
• Thermocouple
• Thermistor
83
6-