Individual Functions
6-87
îš‹ Using PI Control
PI control is a method of making the feedback value (detection value) match the set target value.
The characteristics of the PI control operations are given below.
îš„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 jumps to a certain value (step response).
Fig 6.56 PI Control Operation
îš„PI Control Applications
The following table shows examples of PI control applications using the Inverter.
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-element and an
I-element together the deviation can be eliminated completely.
Application Control Details
Example of Sensor
Used
Pressure Con-
trol
Pressure information is fed back and constant pressure control is performed. Pressure sensor
Flow Rate
Control
Flow rate information is fed back and the flow rate is controlled with high accu-
racy.
Flow rate sensor
Temperature
Control
Temperature information is fed back and a temperature adjustment control
using a fan can be performed.
• Thermocouple
• Thermistor
Deviation
Output of P- and
Time
PI control
I control
P control
Time
I-element
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