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îš‹ Using PID Control
PID control is a method of making the feedback value (detection value) matching the set target value. By com-
bining proportional control (P), integral control (I), and differential control (D), you can even control system
with load fluctuation.
The characteristics of the PID control operations are given below.
îš„PID Control Operation
To understand the differences between the PID control operations P, I, and D, the output share of each opera-
tion is shown in the following diagram when the deviation (i.e., the difference between the target value and
feedback value) is fixed.
Fig 6.80 PID Control Operation
îš„PID Control Applications
The following table shows examples of PID 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.
D element
The output of a D-element is the derivative of the input (deviation). By adding a D-element the
response can be improved rapidly but the system can also become unstable.
Application Control Details
Example of Sensor
Used
Speed Control
• Machinery speed is fed back and adjusted to meet the target value.
• Speed informations from other machinery can be input as the target value and synchronous control using
the actual speed feedback can be performed.
Tachometer generator
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 accuracy. Flow rate sensor
Temperature
Control
Temperature information is fed back and a temperature adjustment control using a fan can be performed.
• Thermocoupler
• Thermistor
Deviation
Output of P-, I-
D control
Time
PID control
I control
P control
Time
and D-element
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