Function Blocks
PID Function Block
Revision 11 HC900 Hybrid Control Designer Function Block Reference Guide 269
2/07
PID Function Block
Description
The PID label stands for Proportional, Integral, Derivative (3-mode) control action.
INPUT - PV
Remote Set Point Signal (Eng. unit or %)
OTHER INPUTS
CONTROL OUTPUT
Feed Forward value in %
Output Track value in %
Output Track Command (ON/OFF)
Remote Bias Value for Ratio PID
Switch Inputs
(from SWO on LPSW function block
)
External Mode request
(from MDSW block)
Back Calculation Input
(for Cascade control)
Working Set Point in EU
Alarm 1 Digital Signal
Alarm 2 Digital Signal
Autotune Indicator (ON = Autotune in progress)
A/M Output & Setpoint Mode indication
(to MDFL block)
Back Calculation Output
(for Cascade control)
OTHER OUTPUTS
Direct/Reverse Indication
This block is part of the
Loops category.
Function
Provides Proportional (P), Integral (I) and Derivative (D), (3-mode) control action based on the deviation or
error signal created by the difference between the setpoint (SP) and the Process variable analog input value
(PV).
It provides two digital output signals for alarms based on configured parameters.
The PID function block provides for Feedforward, Cascade, and Ratio control.
Automatic tuning with Fuzzy Logic Overshoot Suppression can be configured.
Digital inputs may be used to set control mode, select the setpoint source, change control action plus other
discrete actions.
For examples of PID Control, refer to:
Basic PID Configuration
Duplex Control
Cascade Control
Ratio Control
Cascade Control of Boiler Drum Level
Cascade Control of a Boiler Drum Level - 3 Element Feedwater Control
Inputs
PV
= Process Variable Analog Input value in Engineering Units to be controlled
RSP = Remote Setpoint Analog Input value in Engineering Units or Percent to provide external setpoint
FFV = Feedforward value in percent. The Feedforward value is multiplied by the Feedforward Gain, then
directly summed into the output of the PID block.
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