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D PID Control Applications
The following table shows examples of PID control applications using the Inverter.
Application Control contents Sensors used
(example)
Speed control Speeds are matched to target values as speed
information in a mechanical system.
Speed information for another mechanical system is
input as target values, and synchronized control is
executed by feeding back actual speeds.
Tacho-generator
Pressure control Pressure information is returned as feedback for
stable pressure control.
Pressure sensor
Flow control Flow information is returned as feedback for accurate
flow control.
Flow sensor
Temperature control Temperature information is returned as feedback to
control temperature by turning a fan.
Thermocouple
Thermistor
D PID Control Operations
In
order to
distinguish the separate PID control operations (i.e., proportional, integral, and derivative),
the
following diagram shows the changes in the control input (i.e., the output frequency) when the devi
-
ation between the target value and the feedback is held constant.
Deviation
Control
input
D control
Time
PID control
I control
P control
Time
• P Control
A control input proportional to the deviation is output. The deviation cannot be zeroed by P control
alone.
• I Control
A
control input which is an integral of the deviation is output. This is ef
fective for matching the feedback
to the target value. Sudden changes, however, cannot be followed.
• D Control
A control input which is an integral of the deviation is output. Quick response to sudden changes is
possible.
• PID Control
Optimum control is achieved by combining the best features of P, I, and D control.
D Types of PID Control
Two
types of PID control are possible with the 3G3FV
: measured-value derivative PID control and basic
PID control. The type that is normally used is measured-value derivative PID control.
Advanced Operation Chapter
6
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