FB_BA_SeqCtrl

Functional description

The functionalities of this controller are identical to FB_BA_PIDCtrl.

udiOpMode = 0 (upstream proportional component)

udiOpMode = 1 (parallel structure)

In addition the controller, if enabled by bEn = TRUE, is controlled via a higher level control function block FB_BA_SeqLink.

The data exchange between the control function block FB_BA_SeqLink and the sequence controllers FB_BA_SeqCtrl takes place via the structure variable stSeqLink.

Heating-cooling sequence

The controller sequence should be configured such that the sequence controller with lower ordinal number are used for heating and the ones with the higher number for cooling. Only one change is permitted:

• Sequence controller n (udiMyNum=n, bActn=TRUE)
• Sequence controller n+1 (udiMyNum = n+1, bActn = FALSE)

Exclusive programming of cooling and heating controllers is also possible.

Any parameterization that contradicts this convention is detected and indicated as an error at control function block FB_BA_SeqLink.

Controller output

The control function block FB_BA_SeqLink specifies which sequence controller is active. What is output at the respective control output rY is determined inside the individual sequence controllers. Each controller receives the information about the states of the other controllers via the in-out variable stSeqLink and evaluates four cases internally.

1. None of the sequence controllers is enabled, whether due to a missing enable signal (bEn) at the input or due to an error detected on the control function block FB_BA_SeqLink
   -> The internal PID controllers are inactive and output 0.0 at the control output rY.
2. The sequence controller is enabled and has been set to active by the control function block FB_BA_SeqLink.
   -> The internal PID controller is active. Its output signal is output at the control output rY.
3. The sequence controller is enabled, but a sequence controller with a higher ordinal number has been set to active by the control function block FB_BA_SeqLink
   -> The internal PID controller is inactive. If the sequence controller is in heating mode (bActn=FALSE), it will output its minimum value rYMin at the control output rY. Conversely, if it is in cooling mode (bActn = TRUE), then it outputs the maximum value rYMax at the control output rY.
4. The sequence controller is enabled, but a sequence controller with a lower ordinal number has been set to active by the control function block FB_BA_SeqLink
   -> The internal PID controller is inactive. If the sequence controller is in heating mode (bActn=FALSE), it will output its maximum value rYMax at the control output rY. If it is in cooling mode (bActn=TRUE), it will output its minimum value rYMin at the control output rY.

Synchronization

If a sequence controller is activated by the higher-level controller, this always results in synchronization, i.e. the controller starts with a fixed value at the output rY. 3 cases are distinguished:

1. The entire sequence control was switched on via the input bEn of the higher-level controller FB_BA_SeqLink. The controller with the ordinal number udiSttCtrl at the input of FB_BA_SeqLink is the start controller.
   -> The sequence controller is synchronized with the value, which is entered at its input rYSeqInit.
2. The sequence controller, which has just has been activated, had a higher ordinal number than the "previous" one
   -> If the sequence controller is in heating mode (bActn = FALSE), then it is synchronized with its minimum value rYMin. If it is in cooling mode (bActn=TRUE), the synchronization value is its maximum value rYMax.
3. The sequence controller, which has just has been activated, had a lower ordinal number than the "previous" one
   -> If the sequence controller is in heating mode (bActn = FALSE), then it is synchronized with its maximum value rYMax. If it is in cooling mode (bActn=TRUE), the synchronization value is its minimum value rYMin.

Each sequence controller can also be synchronized by specifying a value rSync and activating bSync, if it has just been activated by the higher-level controller. A constant TRUE signal at the input bSync (e.g. accidental) is internally intercepted through edge formation, so that obstruction of the synchronization described above on activation is avoided.

Start-up behavior

In order to enable "sensible" adjustment of the entire control sequence, the start controller is maintained in active state as a minimum for the time udiIniSwiOvrDly_sec [s], which is entered at the function block FB_BA_SeqLink. During this time, no switching takes place to another controller of this sequence.
The output rY of the start controller is synchronized once to its value rYSeqInit.

VAR_INPUT

bEn            : BOOL;
rW             : REAL;
rX             : REAL;
udiOpMode      : UDINT;
bActn          : BOOL;
rKp            : REAL;
udiTn_ms       : UDINT;
udiTv_ms       : UDINT;
udiTd_ms       : UDINT;
rYMax          : REAL;
rYMin          : REAL;
rNZ            : REAL;
udiCycCl       : UDINT;
bSync          : BOOL;
rSync          : REAL;
rYSeqInit      : REAL;
udiMyNum       : UDINT;

bEn: Activation of the sequence controller

rW: Set value

rX: Actual value

udiOpMode: udiOpMode=0: Controller with upstream proportional component, udiOpMode = 1: Controller in parallel structure. The values are limited internally to 0 and 1.

bActn: Direction of action reversal of the controller. For heating/cooling operation: bActn=FALSE corresponds to heating mode, bActn=TRUE corresponds to cooling mode.

rKp: Controller gain. Only affects the proportional component. Internally limited to a minimum value of 0.

udiTn_ms: Integral action time of the I component [ms]. A zero value at this parameter disables the I component. Internally limited to a minimum value of 0.

udiTv_ms: Rate time of the D component [ms]. A zero value at this parameter disables the D component. Internally limited to a minimum value of 0.

udiTd_ms: Damping time of the D component [s]. Internally limited to a minimum value of 0.

rYMax: Upper controller output limit [%]. Selectable range: 0..100%.

rYMin: Lower controller output limit [%]. Selectable range: 0..100%. The value lrMin is upwardly limited by lrYMax.

rNZ: neutral zone (see Deadband diagram). Internally limited to a minimum value of 0. Mode of action is same as FB_BA_PID_Ctrl.

udiCycCl: Call cycle of the function block as a multiple of the cycle time. Internally limited to a minimum value of 1.
Example: tTaskCycleTime = 20 ms, udiCycCl = 10 -> the control algorithm is called every 200 ms. Thus the outputs are also updated only every 200 ms.

bSync / rSync: Synchronization command: Set output value rY to rSync. The value rSync is limited internally to values ranging from rYMin to rYMax.

rYSeqInit: Starting value of the controller after restart of the whole control sequence.

udiMyNum: Ordinal number of the sequence controller. Internally limited to values ranging from 0 to gBA_cMaxSeqCtrl.

VAR_OUTPUT

rY        : REAL;
rE        : REAL;
bErr      : BOOL;
sErrDescr : T_MAXSTRING;

rY: Control value. Section: 0..100%, unless limited further by rYMin and rYMax.

rE: Control deviation (The calculation depends on the direction of action).

bErr: This output is switched to TRUE if the parameters entered are erroneous.

sErrDescr: Contains the error description.

VAR_IN_OUT

stSeqLink : ST_BA_SeqLink;

stSeqLink: Data and command structure (see ST_BA_SeqLink / ST_BA_SeqLinkData) between the individual sequence controllers and the control function block FB_BA_SeqLink.

If several sequence controllers have the same number (diMyNum), this is detected and output as an error at the sequence controller and at the control function block FB_BA_SeqLink.

Requirements