ValveAnalog

ValveAnalog (FB)

FUNCTION_BLOCK ValveAnalog

Short description

Control of a continuous valve actuator with anti-blocking function and continuous position feedback Typical application: control valve in a heating circuit

Representation

Interfaces

Inputs

Name	Data type	Value range	Initial value	Function
rY	REAL			Control signal from controller
xForce	BOOL		FALSE	Forced override after manual override
xAlarmIn	BOOL		FALSE	Actuator fault message
rU	REAL		0.0	Position feedback from the control valve
eAO	HVACTYPES.eManNum	HVACTYPES.eManNum.Auto, HVACTYPES.eManNum.Man	HVACTYPES.eManNum.Auto	Feedback - automatic operation
rPoti	REAL			Feedback - control signal from hardware manual level

Outputs

Name	Data type	Value range	Initial value	Function
rHA	REAL			Control signal after manual override
rAA	REAL			Control signal before manual override
xAlarmPos	BOOL			Fault message from position monitoring
dtAbsLastOn	DATE_AND_TIME			Date / time of the last anti-blocking operation
xAlarm	BOOL			General fault indication
xAuto	BOOL			Collective automatic mode message

Setpoints / parameters

Name	Data type	Value range	Initial value	Function
udiControlTime	UDINT	0 … 600s	180s	Duration of the position monitoring
rControlDiff	REAL		7.0%	Monitoring of valve position: Maximum position deviation
xControl	BOOL		TRUE	Enablement of the position monitoring
xForceOption	BOOL		TRUE	State of the output rHA under forced override
rAbsMaxLimit	REAL		100.0	Upper limit for the control signal before manual override
rAbsMinLimit	REAL		0.0	Lower limit for the control signal before manual override
udiAbsTime	UDINT	10s … 600s	180s	Duration of anti-blocking operation in seconds
tAbsStartTime	TOD	00:00:00 - 23:59:59 hrs	08:00:00 hrs	Time of the anti-blocking operation
eAbsDay	eDoW	eDow.Inactive, eDoW.Monday … eDoW.Sunday	eDoW.Monday	Weekday of the anti-blocking operation
rManValue	REAL		0.0	Manual override: manual value
eManModeN	eMANNUM	eMANNUM.Auto, eMANNUM.Man		Manual override: operating mode

Function description

Control signal before manual override rAA

The control signal before manual override rAA is influenced by the anti-blocking module. The anti-blocking module is parameterized by the setpoints / parameters udiAbsTime, tAbsStartTime and eAbsDay as parameters, using the position feedback from the control valve rU as input signal. The minimum change of the valve position required to lock the anti-blocking function is fixed at 10.0%. The control signal before manual override rAA is limited by the two absolute limits rAbsMinLimit and rAbsmaxLimit . The position feedback from the control valve rU may be replaced by the control signal from the controller rY if no position feedback is available.

Control signal after manual override rHA

The control signal after manual override rHA is influenced by the output of the anti-blocking module, the control signal from the controller rY, the manual override and the forced control.

eManModeN	Anti-blocking process	xForce	xForceOption	rHA	Notes
eMANNUM.Auto	FALSE	FALSE	X	rY	Automatic operation with passive anti-blocking process
eMANNUM.Auto	TRUE	FALSE	X	Output of the anti-blocking process	Automatic operation with active anti-blocking process
eMANNUM.Man	X	FALSE	X	rManValue	Manual override
X	X	TRUE	FALSE	0.0	Forced override 0.0%
X	X	TRUE	TRUE	100.0	Forced override 100.0%

Legend: X = don't care

Position monitoring

The position monitoring can be enabled ( xControl = TRUE ) or disabled ( xControl = FALSE ). When position monitoring is enabled, the absolute value of the difference between the control signal after manual override rHA and the position feedback from the control valve rU is determined and compared with the threshold rControlDiff . If this difference permanently exceeds the threshold during an alarm delay udiControlTime an alarm signal is generated, provided at the same time the feedback - automatic operation eAO signals the automatic operation ( eAO = HVACTYPES.eManNum.Auto ). This alarm signal is forwarded to the output xAlarmPos transferred ( xAlarmPos = TRUE ). The alarm signal is deactivated again ( xAlarmPos = FALSE ) as soon as the difference falls below the threshold for the first time.

Position feedback from the control valve rU

The position feedback from the control valve rU may be replaced by the control signal from the controller rY if no position feedback is available.

Anti-blocking module

The anti-blocking module is implemented by the numerical anti-blocking module with adjustable duration (FB: AbsA). The duration udiAbsTime, the time todAbsStartTime and the weekday eAbsDay are adjustable. The minimum runtime to lock the anti-blocking operation is 30 s. The timestamp (date / time) of the last anti-blocking operation dtAbsLastOn is available.

Aggregate fault xAlarm

The aggregate fault xAlarm is activated ( = TRUE ) if xAlarmPos or the input xAlarmIn is active. In all other cases the collective fault xAlarm is not activated ( = FALSE ).

Collective automatic mode message xAuto

The collective automatic mode message xAuto is activated ( = TRUE ) if the input eAO has the value HVACTYPES.eManNum.Auto and the setpoint / parameter eManModeN contains the value eMANNUM.Auto. In all other cases the aggregate message is automatic operation xAuto is not activated ( = FALSE ).

Forced override xForce

The forced override acts directly on the output rHA. With the parameter xForceOption it is defined which state the output rHA assumes at TRUE on the input xForce takes. When xForceOption = FALSE If the input xForce is TRUE, then the output rHA set to 0. At xForceOption = TRUE If the input xForce is TRUE, then the output rHA set to 100.

CODESYS

InOut:

Scope	Name	Type	Initial
Input	rY	REAL
Input	xForce	BOOL	FALSE
Input	xAlarmIn	BOOL	FALSE
Input	rU	REAL	0
Input	eAO	eManNum	eManNum.Auto
Input	rPoti	REAL
Output	rHA	REAL
Output	rAA	REAL
Output	xAlarmPos	BOOL
Output	dtAbsLastOn	DT
Output	xAlarm	BOOL
Output	xAuto	BOOL
Input Const	udiControlTime	UDINT	200
Input Const	rControlDiff	REAL	7
Input Const	xControl	BOOL	TRUE
Input Const	xForceOption	BOOL	TRUE
Input Const	rAbsMaxLimit	REAL	100
Input Const	rAbsMinLimit	REAL	0
Input Const	udiAbsTime	UDINT	180
Input Const	todAbsStartTime	TOD	TIME_OF_DAY#8:0
Input Const	eAbsDay	eDoW	eDow.Monday
Input Const	rManValue	REAL	0
Input Const	eManModeN	eMANNUM	eMANNUM.Auto