ControlP

ControlP (FB)

FUNCTION_BLOCK ControlP

Short description

Proportional controller (P-controller) The action (inverted / direct) is also adjustable. Typical application: control loops with actuators that have an integrating (storage) character.

Representation

Interfaces

Inputs

Name	Data type	Value range	Initial value	Function
rX	REAL			Analog actual value
rW	REAL			Analog setpoint
xEn	BOOL			Enable of the controller

Outputs

Name	Data type	Value range	Initial value	Function
rY	REAL		0.0	Controller output signal
rDiff	REAL			Control deviation
xLimitActive	BOOL			Status - limit exceedance

Setpoints / Parameters

Name	Data type	Value range	Initial value	Function
rMax	REAL		100.0	Upper absolute limit of the output signal
rMin	REAL		-100.0	Lower absolute limit of the output signal
rKp	REAL	0.0 …	2.0	Gain factor
rOffset	REAL		0.0	Offset
rYDisabled	REAL		0.0	Shutdown value
eAction	eControlMode		eControlMode.Inverted	Controller action (Inverted, Direct)
eManModeN	eManNum		eManNum.Auto	Operating mode for the controller output signal
rManValue	REAL			Output signal in manual mode

Function description

General

This function block contains a proportional acting controller (P-controller). The controller's output signal rY is calculated when the controller is enabled ( xEn = TRUE ) and in the controller's automatic operating mode ( eManModeN = eManNum.Auto ) as follows: &#xNAN;rY = rKp * (( actual value + offset ) - ( setpoint )) Depending on the controller action eAction the actual and set values are defined as follows:\

eAction	Actual value	Setpoint	Formula	Function
eControlMode.Inverted	rW	rX	rY = rKp * (( rW + rOffset ) - ( rX ))	Action - Inverted
eControlMode.Direct	rX	rW	rY = rKp * (( rX + rOffset ) - ( rW ))	Action - Direct

Enable input xEn

If the enable input is not active ( xEn = FALSE ) the shutdown value rYDisabled is transferred to the output rY ( prerequisite: eManModeN = eManNum.Auto ) and limited by the absolute limits. If the enable input is active ( xEn = TRUE ) the output signal is calculated according to the formula above and to the output rY ( prerequisite: eManModeN = eManNum.Auto ) and limited by the absolute limits.\

Control deviation rDiff

The control deviation is calculated according to the following formula and transferred to the output rDiff . &#xNAN;rDiff = actual value - setpoint \

Absolute limits rMin and rMax

The controller's output signal rY is limited downward by the absolute limits rMin and upward rMax . The absolute limit rMin is set to the current value of rMax - 0.1 if it >= the current value of rMax . The only exception is the manual operation for the controller's output signal (eManModeN = eManNum.Man ).\

Status - limit exceedance xLimitActive

The limit exceedance status is activated ( xLimitActive = TRUE ) if a limit exceedance is present. The limit exceedance status is not activated ( xLimitActive = FALSE ) if no limit exceedance is present. A limit exceedance is present if the controller's output signal rY reaches / exceeds the upper limit rMax or reaches / falls below the lower limit rMin . \

Operating mode for the controller output signal eManModeN

The parameter eManModeN allows switching the output signal rY from automatic to manual operation and vice versa. In manual mode the output signal takes over rY the output signal in manual mode rManValue. The setpoint / parameter rManValue is overwritten with the current value of the output signal each time there is a transition to automatic operation. rY \

eManModeN	rY	Function
eManNum.Auto	Signal according to formula / switch-off value	Automatic mode - output signal
eManNum.Man	rManValue	Manual mode - output signal

CODESYS

InOut:

Scope	Name	Type	Initial
Input	rX	REAL
Input	rW	REAL
Input	xEn	BOOL
Input Const	rYMax	REAL	100
Input Const	rYMin	REAL	-100
Input Const	rKp	REAL	2
Input Const	rOffset	REAL	0
Input Const	rYDisabled	REAL	0
Input Const	eAction	eControlMode	eControlMode.Inverted
Input Const	eManModeN	eManNum	eManNum.Auto
Input Const	rManValue	REAL
Output	rY	REAL	0
Output	rDiff	REAL
Output	xLimitAktiv	BOOL