Redundance3

Redundance3 (FB)

FUNCTION_BLOCK Redundance3

Short description

Redundant control of 0 - 3 identical devices Influencing factors: requirements, operating hours, operating and fault conditions Typical application: determination of leader and follower devices

Representation

Interfaces

Inputs

Name	Data type	Value range	Initial value	Function
wActiveNumberOfDevices	WORD		0	Number of active devices (0 - 3)
xFb1	BOOL		FALSE	Running - Device 1 (TRUE = running)
xFb2	BOOL		FALSE	Running - Device 2 (TRUE = running)
xFb3	BOOL		FALSE	Running - Device 3 (TRUE = running)
xAlarm1	BOOL		TRUE	Fault - Device 1 (TRUE = fault)
xAlarm2	BOOL		TRUE	Fault - Device 2 (TRUE = fault)
xAlarm3	BOOL		TRUE	Fault - Device 3 (TRUE = fault)
uiOperatingHours1	UDINT		0	Operating hours - Device 1
uiOperatingHours2	UDINT		0	Operating hours - Device 2
uiOperatingHours3	UDINT		0	Operating hours - Device 3
xUpdate	BOOL			Trigger recalculation of the sequence on every rising edge

Outputs

Name	Data type	Value range	Initial value	Function
udiCurrentSequence	UDINT		0	Current device sequence as integer
sCurrentSequence	STRING		‘’	Current device sequence as string
wNumberOfOperationalDevices	WORD		0	Number of operational devices
xCmd1	BOOL		FALSE	Enable - Device 1 (TRUE = enable)
xCmd2	BOOL		FALSE	Enable - Device 2 (TRUE = enable)
xCmd3	BOOL		FALSE	Enable - Device 3 (TRUE = enable)
wPrio1	WORD		0	Current priority of device 1 (0 = none, 1 - 3)
wPrio2	WORD		0	Current priority of device 2 (0 = none, 1 - 3)
wPrio3	WORD		0	Current priority of device 3 (0 = none, 1 - 3)
xErr	BOOL		FALSE	Output - Fault
eOperationalCondition	eRedundance3_OperationalMode			Number / name of the current operating condition

Setpoints / parameters

Name	Data type	Value range	Initial value	Function
xConOperatingHours	BOOL		TRUE	FALSE = follow switching enabled only by input xUpdate, TRUE = follow switching automatically by operating hours
xEnFb	BOOL		TRUE	FALSE = switching by enable (xCmdX), TRUE = switching by running signal (xFbX)
wTolerance	WORD		100	Threshold - operating hours difference for direct follow change in partial load operation

Function description

General

This function block is used for the redundant control of 0 - 3 identical devices depending on the influencing variables Requirements (wActiveNumberOfDevices), operating hours (uiOperatingHours), operating states (xFb) and fault conditions (xAlarm).

Input wActiveNumberOfDevices

This input is used to specify the number of devices that should currently be used. Permissible range: 0 - 3

Input xUpdate

Each rising edge on this input triggers a recalculation of the current device sequence. Boundary conditions: xConOperationHours = FALSE, operating hours difference = 0 hours.

Output udiCurrentSequence

This output always indicates the current device sequence as an integer. The number of the device with the highest priority is always at the beginning, followed by the number of the device with the second-highest priority, and so on.

Example: udiCurrentSequence = 145 means: Device 1 = priority 1, Device 4 = priority 2 and Device 5 = priority 3

Output sCurrentSequence

This output always shows the current device sequence as a string with delimiters. The same applies regarding priorities as for the output udiCurrentSequence.

Example: sdiCurrentSequence = ‘1-4-5’ means: Device 1 = priority 1, Device 4 = priority 2 and Device 5 = priority 3

Output wNumberOfOperationalDevices

This output always indicates the number of operational devices.

Output Fault xErr

This output is active (= TRUE) if at least one of the following conditions is met.

1. wActiveNumberOfDevices > 3

2. wActiveNumberOfDevices > wOperationalNumberofDevices

In all other cases the output xErr not active (= FALSE).

Output eOperationalCondition

This output always represents the current load situation (idle, partial load, full load) depending on the setpoint / parameter xEnFb thereof. xEnFb = FALSE: The enable outputs xCmd of the operational devices are evaluated / considered. xEnFb = TRUE: The operating states xFb of the operational devices are evaluated / considered.

Example: xEnFb = TRUE and xFb1 = TRUE and xFb2 = TRUE: Output = PartLoad_Inputs_Fb

Setpoint / parameters xConOperatingHours

xConOperatingHours = FALSE: Switching of the device sequence is triggered only by a rising edge at input xUpdate . xConOperatingHours = TRUE: Switching of the device sequence is triggered depending on the operating hours, the running signals (when xEnFb = TRUE) and the enables (when xEnFb = FALSE) .

Setpoint / parameters xEnFb

xEnFb = FALSE: The enable outputs ‘xCmd’ of the operational devices are evaluated / considered. xEnFb = TRUE: The running states ‘xFb’ of the operational devices are evaluated / considered.

Setpoint / parameters wTolerance

This setpoint determines the maximum operating hours difference before switching the device sequence due to operating hours.

Determination of the device sequence

A switch of the device sequence can generally only take place if at least one of the following conditions is met:

1. The fault state of at least one device has changed (high priority)

2. The operating hours of at least one operational device have changed (low priority)

Definition - idle:

xEnFb = FALSE: The enable outputs ‘xCmd’ of all operational devices are inactive (= FALSE) xEnFb = TRUE: The operating feedbacks ‘xFb’ of all operational devices are inactive (= FALSE)

Definition - full load:

xEnFb = FALSE: The enable outputs ‘xCmd’ of all operational devices are active (= TRUE) xEnFb = TRUE: The operating feedbacks ‘xFb’ of all operational devices are active (= TRUE)

Definition - partial load:

xEnFb = FALSE: The number of enable outputs 'xCmd' of all operational devices in the active state (= TRUE) is greater than or equal to 1 and less than the number of all operational devices. xEnFb = FALSE: The number of running signals 'xFb' of all operational devices in the active state (= TRUE) is greater than or equal to 1 and less than the number of all operational devices. Switching with high priority (= immediate) depending on the fault conditions (inputs xAlarm) The fault condition of each device in the range 1 - 3 is recorded cyclically and evaluated for changes. Any faulty device in the range 1 - 3 (input xAlarm = TRUE) is no longer operational. Any change in the fault condition of at least one device in the range 1 - 3 triggers an immediate recalculation of the device order. Switching with low priority depending on the operating hours (inputs udiOperationHours), operating states (inputs xFb) and enable outputs (outputs xCmd) of devices 1 - 3. The operating hours of each operational device in the range 1 - 3 are recorded cyclically and evaluated for changes. The operating states and enable outputs of each operational device in the range 1 - 3 are recorded cyclically.

The recalculation of the device order takes place as soon as one of the situations described below is given: Situation 1 (xConOperationHours = FALSE, rising edge at input xUpdate) A recalculation of the device order is performed with an operating hours difference of 0 hours, i.e. the non-faulty device with the lowest number of operating hours has the highest priority (in case of equal operating hours the device with the lower number has the higher priority). Situation 2 (xConOperationHours = TRUE, idle or full load) In idle or under full load a recalculation of the device order is performed with an operating hours difference of 0 hours, i.e. the non-faulty device with the lowest number of operating hours has the highest priority (in case of equal operating hours the device with the lower number has the higher priority).

The recalculation of the device order is triggered if the operating hours of at least one operational device have changed. Situation 3 (xConOperationHours = TRUE, partial load) On the first transition into partial load operation a recalculation of the device order is performed with an operating hours difference of 0 hours, i.e. the non-faulty device with the lowest number of operating hours has the highest priority (in case of equal operating hours the device with the lower number has the higher priority). In regular partial load operation a recalculation of the device order is performed with an operating hours difference of wTolerance hours.

The recalculation of the device order is triggered if the operating hours of at least one operational device have changed.

Enable outputs xCmd

The states of the outputs of the devices in the range 1 - 3 are finally determined as follows: The enable outputs of the operational devices in the range 1 - 3 are activated if their current priority <= the number of requested devices (input wActiveNumberOfDevices).

The enable outputs of the operational devices in the range 1 - 3 are deactivated if their current priority > the number of requested devices (input wActiveNumberOfDevices).

Priority outputs wPrio

The priority outputs of each device always contain the current priority in the range 0 - 3. Priority = 0: The device has no or an invalid priority Priority = 1: The device has the highest priority Priority = 2: The device has the second highest priority Priority = 3: The device has the third highest priority

CODESYS

InOut:

Scope	Name	Type	Initial
Input	wActiveNumberOfDevices	WORD	0
Input	xFb1	BOOL	FALSE
Input	xFb2	BOOL	FALSE
Input	xFb3	BOOL	FALSE
Input	xAlarm1	BOOL	TRUE
Input	xAlarm2	BOOL	TRUE
Input	xAlarm3	BOOL	TRUE
Input	udiOperatingHours1	UDINT	0
Input	udiOperatingHours2	UDINT	0
Input	udiOperatingHours3	UDINT	0
Input	xUpdate	BOOL
Input Const	xConOperatingHours	BOOL	TRUE
Input Const	xEnFb	BOOL	TRUE
Input Const	wTolerance	WORD	100
Output	udiCurrentSequence	UDINT	0
Output	sCurrentSequence	STRING	‘’
Output	wNumberOfOperationalDevices	WORD	0
Output	xCmd1	BOOL	FALSE
Output	xCmd2	BOOL	FALSE
Output	xCmd3	BOOL	FALSE
Output	wPrio1	WORD	0
Output	wPrio2	WORD	0
Output	wPrio3	WORD	0
Output	xErr	BOOL	FALSE
Output	eOperationalCondition	eRedundance3_OperationalMode