Redundant2 (FB)¶

FUNCTION_BLOCK Redundant2

Short Descritpion¶

Redundant control of two devices similar in type

Influencing factors: requirements, operating hours, operating and fault states

Typical application: Definition of the lead and follower pump

Portrayal¶

Interfaces¶

Inputs¶

Name
Datatype

Range

Init-Value

Function

xEnOne BOOL
Requirement - lead device

xEnTwo BOOL
Requirement - Lead and follower device

xFb1 BOOL
Operation - Device 1

xFb2 BOOL
Operation - Device 2

xAlarm1 BOOL
Fault - Device 1

xAlarm2 BOOL
Fault - Device 2

uiOperatingHours1 UDINT
Operating hours - Device 1

uiOperatingHours2 UDINT
Operating hours - Device 2

xUpdate BOOL
Enable - sequence control after operating hours

Outputs¶

Name
Datatype

Range

Init-Value

Function

iCurrentSequence INT
Current device sequence

xCmd1 BOOL
Enable - Device 1

xCmd2 BOOL
Enable - Device 2

xErr BOOL
Fault output

Setpoints / Parameters¶

Name
Datatype

Range

Init-Value

Function

xConOperatingHours BOOL TRUE
Enable - Follower device after Operation hours

xEnFb BOOL TRUE
Enable - Use of the operation messages

wTolerance WORD 100
Limit value - Operating hours difference

Functional Description¶

General¶

This function block is used for the redundant control of two devices similar in type depending on the influencing variables
Requirements (xEnOne and xEnTwo), operating hours (uiOperatingHours1 and uiOperatingHours2), operating states (xFb1 and xFb2)
and fault states (xAlarm1 and xAlarm2). The release of the lead and, if necessary, the follower device is defined internally and under
consideration of the iCurrentSequence current sequence transferred to the xCmd1 or xCmd2 device outputs.

xEnOne and xEnTwo requirements¶

They are used to define whether only the lead device or the lead and the follower device should be requested.

xEnOne xEnTwo
Lead device

Follower device

Notes

FALSE FALSE FALSE FALSE
No requirement

TRUE FALSE TRUE FALSE
Requirement - lead device

X TRUE TRUE TRUE
Requirement - Lead and follower device

Legend: X = Undefined

Fault output xErr¶

It indicates a discrepancy between the requirements and the fault states of the devices.
The constellations are described in the function table that activate the xErr output (= TRUE), that is, indicate a fault.
In all other cases, the xErr output is not active (= FALSE).

xEnOne xEnTwo xAlarm1 xAlarm2 xErr
Notes

TRUE X TRUE TRUE TRUE
Requirement - Lead device and both devices are faulty

X TRUE TRUE X TRUE
Requirement - Lead device and follower device and at least one device is faulty

X TRUE X TRUE TRUE
Requirement - Lead device and follower device and at least one device is faulty

Legend: X = Undefined

Output iCurrentSequence¶

It always displays the current sequence of the two devices.
The first digit always indicates the device number of the lead device (example: iCurrentSequence = 1X ... Lead device = Device 1)
The second digit always indicates the device number of the follower device. (Example: iCurrentSequence = X2 ... Follower = Device 2)

Setpoint / Parameter xConOperatingHours¶

In the TRUE state, the sequential switching is triggered for each execution of the function block in dependency on the operating hours and operating messages
(at xEnFb = TRUE) of Devices 1 and 2. In the FALSE state, the sequential switching can only be triggered by a rising edge at the
xUpdate input.

Setpoint / Parameter xEnFb¶

In the TRUE state, the operating states of the Devices 1 and 2 are evaluated and taken into account in the sequential switching.

In the FALSE state, the device outputs of Devices 1 and 2 are evaluated and taken into account in the sequential switching.

Setpoint / Parameter wTolerance¶

This setpoint determines the maximum operating hours difference before a switching over of the lead and follower device on the basis of the operating hours.

Determination of the lead and follower device¶

High priority switching over depending on the fault status of devices 1 and 2

xAlarm1 xAlarm2
Lead device

Follower device

Notes

FALSE FALSE
not influenced

not influenced

Both devices without fault

TRUE FALSE
Device 2

Device 1

Device 1 faulty

X TRUE
Device 1

Device 2

Device 2 faulty

Legend: X = Undefined

Low priority switching over depending on the operating hours, operating messages (xEnFb = TRUE)

A re-evaluation and definition with low priority can be triggered in each case as follows:

xConOperatingHours = TRUE and / or rising edge at the xUpdate input

xConOperatingHours xUpdate
Conditions

Lead device

FALSE FALSE, TRUE, H/L
No re-evaluation

TRUE FALSE, TRUE, H/L
Identical operating messages (xEnFb = TRUE) or identical enable outputs (xEnFb = FALSE) of the devices

Device with fewer operating hours

TRUE FALSE, TRUE, H/L
One device in operation (xEnFb = TRUE) or one device enabled (xEnFb = FALSE)

Change to the device with a lower number of operating hours, if the difference in operating hours > wTolerance.

FALSE L/H
uiOperatingHours1 = uiOperatingHours2 = 0 (No operating hours available)

Change of the lead device with the follower device

FALSE L/H
uiOperatingHours1 or uiOperatingHours2 > 0

Device with fewer operating hours

Legend: L/H ... Rising edge, H/L ... falling edge

Device outputs xCmd1 and xCmd2¶

The device outputs are finally defined as follows:

Lead device = Device 1

xCmd1 = TRUE: The lead device is requested and at least one device is requested and device 1 is not disturbed

xCmd2 = TRUE: The lead device is requested and at least one device is requested and device 2 is not disturbed

Lead device = Device 2

xCmd1 = TRUE: The follower device is requested and at least one device is requested and device 1 is not disturbed

xCmd1 = TRUE: The lead device is requested and at least one device is requested and device 2 is not disturbed

Visualization¶

Information¶

Element
Authors

Date
Version
Notes

Function
Adam Bartod 09.2016 1.0
Initial version

Programming
Adam Bartod 09.2016 1.0
Initial version

Test Jochen Reu 10.2017 1.0
Initial version

Documentation
Jochen Reu 10.2017 1.0
Initial version

Codesys¶

InOut:

Scope	Name	Type	Initial	Comment
Input	xEnOne	BOOL		Requirement - lead device
	xEnTwo	BOOL		Requirement - Lead/follower device
	xFb1	BOOL		Operation - Device 1
	xFb2	BOOL		Operation - Device 2
	xAlarm1	BOOL		Fault - Device 1
	xAlarm2	BOOL		Fault - Device 2
	uiOperatingHours1	UDINT		Operating hours - Device 1
	uiOperatingHours2	UDINT		Operating hours - Device 2
	xUpdate	BOOL		Comparison of operating hours at edge
	xConOperatingHours	BOOL	TRUE	Enable - continuous comparison of operating hours
	xEnFb	BOOL	TRUE	Use of FALSE = Enable; TRUE = Operating message
	wTolerance	WORD	100	Limit value - operating hours difference for direct sequence change when only one device is in operation
Output	iCurrentSequence	INT		Current device sequence
	xCmd1	BOOL		Enable - Device 1
	xCmd2	BOOL		Enable - Device 2
	xErr	BOOL		Fault output