35 CPU MODULE BUILT-IN ANALOG FUNCTION
35.6 Function (PID Control Via Parameter)
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■PD control
PD control is a control method that prevents large fluctuation in the measured value (PV) due to such a cause as disturbance
by adding differential control to P control.
When the value for the integral time (TI) is set to 0, PD control is selected.
■PID control
PID control is a control method that adds differential control to PI control so that the state shifts to a stable state in a short
period of time even when a drastic change has occurred.
By setting the derivative time (TD) properly, the control target can be shifted to a stable state in a short period of time.
Proportional gain setting function
The proportional gain (KP) is set separately for heating and for cooling.
By changing the values for the heating proportional gain (KPh) and cooling proportional gain (KPc), different gradients
(heating proportional band (Ph), cooling proportional band (Pc)) can be set.
The reciprocal of the proportional gain is called as the proportional band, and their relation is as follows.
Measured value (PV)
Target value (SV)
PD control
P control
Time
Measured value (PV)
PID control
Target value (SV)
P control
Time
100
= Proportional band (P)
Proportional gain (Kp)
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