====== Three-point P controller  ======

{{:en:mervis-ide:35-help:t8.png}}

===== Block name =====

T8_THREE_POINT_CONTROLLER

===== ST call =====

<code st-iec>
PROGRAM TEST_T8
    VAR 
        REAL1,REAL2,REAL3,REAL4,REAL5,REAL6: REAL;
      TIME1,TIME2,TIME3,TIME4,TIME5,TIME6   :TIME;
        BOOL1,BOOL2,BOOL3,BOOL4,BOOL5,BOOL6:BOOL;
       FB: LIB.HVAC.V1_0.T8_THREE_POINT_CONTROLLER;
    END_VAR
 FB(X:= REAL1, W:= REAL2, BCRASH:= BOOL1, BR:= BOOL2, ENABLED:= BOOL3, BSP:= BOOL4, TOLMIN:= REAL3, TOLMAX:= REAL4, TROPEN:= TIME1, TRCLOSE:= TIME2, T0:= TIME3, TIMPMIN:= TIME4, TIMPMAX:= TIME5, CLOSE=>BOOL5, OPEN=>BOOL6, OUT=>REAL5, TIMEPERIOD=>TIME6);
END_PROGRAM
</code>

===== Library =====

LIB\HVAC

===== Version =====

V1.0

===== Description =====

The block is a P-controller with a three-point output.

===== Inputs =====

|Input  |Typ |Description                                                                                                                                                                                       |Default value|
|X      |REAL|Real (measured) value                                                                                                                                                                             |0            |
|W      |REAL|Setpoint value                                                                                                                                                                                    |0            |
|BCRASH |BOOL|Signal for fast travel to a safe position, when activated, the safe position output is active permanently                                                                                         |False        |
|BR     |BOOL|Reset (sync) input to travel to a safe position and reset the internal position counter                                                                                                           |False        |
|ENABLED|BOOL|Synchronisation enabled                                                                                                                                                                           |False        |
|T0     |TIME|Length of gap (pause) between the pulses                                                                                                                                                          |4s           |
|TIMPMAX|TIME|Max. length of output pulse                                                                                                                                                                       |2,5s         |
|TIMPMIN|TIME|Min. length of output puls                                                                                                                                                                        |1,5s         |
|TOLMAX |real|Upper tolerance limit\\ \\ * |X-W|>//TOLMAX// – the control pulse length is //TIMPMAX//,\\ * //TOLMIN//<=|X-W|<=//TOLMAX// – the control pulse length changes between //TIMPMIN// and //TIMPMAX//.|2            |
|TOLMIN |REAL|Lower tolerance limit - at |X-W|<//TOLMIN// the outputs are inactive                                                                                                                              |1            |
|TRCLOSE|TIME|Travel time 100 % to 0 %                                                                                                                                                                          |65s          |
|TROPEN |TIME|Travel time 0 % to 100 %                                                                                                                                                                          |65s          |

===== Outputs =====

|Output    |Typ |Description                                                    |
|CLOSE     |BOOL|Command to open                                                |
|OPEN      |BOOL|Command to close                                               |
|OUT       |REAL|Expected (calculated) position (0%...100%)                     |
|TIMEPERIOD|TIME|Auxiliary value - calculated length of the control pulse period|

===== Function =====

The block is used where a 3-point actuator has to be controlled using a P algorithm. The output pulse length is proportional to the difference between real and setpoint values. Parameters //T0//, //TIMPMAX,// and //TIMPMIN// are set instead of the bandwidth or gain.

{{:en:mervis-ide:35-help:t8_1.png}}\\
{{:en:mervis-ide:35-help:t8_2.png}}

===== Application example =====

Similar to T2, however, the P controller is part of the three-point control block, and not a separate function block.

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