Pid Function Block - Honeywell UMC800 Reference Manual

Function Blocks

2.50 PID Function Block

Description
The PID label stands for Proportional, Integral, Derivative (3-mode) control action. This block is part of
the Loops category. It looks like this graphically on the Control Builder.
OTHER INPUTS
Remote Set Point Signal (Eng. unit or %)
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
Back Calculation Input
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 Subsections:
2.50.1 Basic PID Configuration
2.50.2 Duplex Control
2.50.3 Cascade Control
2.50.4 Ratio Control
2.50.5 Cascade Control of Boiler Drum Level
2.50.6 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.
TRV = Output Track value in Percentage (PID Output = TRV Input when TRC = ON.)
TRC = Output Track Command [ON, OFF] (On -Enables TRV.) (Mode = Local Override)
BIAS = Remote Bias value for Ratio PID
138
INPUT - PV
)
(from MDSW block)
(for Cascade control)
CONTROL OUTPUT
Function Block Reference Guide
OTHER OUTPUTS
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
Back Calculation Output
(for Cascade control)
(to MDFL block)
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