====== Simple PI Controller with Enable Input (v1.2) ======

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

==== Full Name ====

Lib.Mervis.v1_2.SimplePiControllerWithEn

==== Required Project References ====

  * Lib.Mervis

===== Description =====

This auxiliary block is used to implement a simple PI controller with an //Enable// input.

===== Usage in ST =====

<code>
program test
    var
        pi: lib.mervis.v1_2.SimplePiControllerWithEn := (Xp := ..., Ti := ..., Min := ..., Max := ...);
    end_var

    pi(Input := ..., SetPoint := ..., Enable := ..., Output => ...);
end_program
</code>

===== Inputs =====

|Name    |Data Type|Allowed Range|Retain|Required                                               |Meaning|
|Input   |real     |             |No    |Yes     |Actual value                                          |      |
|SetPoint|real     |             |No    |Yes     |Desired value                                         |      |
|Enable  |bool     |             |No    |No      |Function enable, if //false// the output is 0         |      |
|Min     |real     |<= 0         |No    |No      |Minimum output value                                  |      |
|Max     |real     |>= 0         |No    |No      |Maximum output value                                  |      |
|Xp      |real     |> 0          |No    |No      |Proportional gain                                     |      |
|Ti      |real     |> 0          |No    |No      |Integral time constant                                |      |

===== Outputs =====

|Name             |Data Type|Meaning                                                                            |
|Output           |real     |Output                                                                             |      |
|InvalidParameters|bool     |Indicates invalid controller settings (//Xp, Ti, Min, or Max// out of allowed range)|      |

===== Block Methods =====

|Name                                                                          |Meaning|
|[[..:simplepicontrollerwithen_adjust.htm|Adjust]]              |Used to adjust the integral component so the output reaches the maximum value |      |
|[[..:simplepicontrollerwithen_adjusttovalue.htm|AdjustToValue]]|Used to adjust the integral component so the output reaches the desired value|      |
|[[..:simplepicontrollerwithen_restart.htm|Restart]]            |Used to reset internal values and restart the calculation                      |      |

===== Detailed Function Description =====

The functional block implements a PI controller. The following formulas are used for output calculation:

  * Control deviation\\
**e = SetPoint - Input**
  * Integral component (every scan cycle)\\
**IPart = IPart + (Max - Min) / (Xp * Ti) * e * ΔT**
  * Output\\
**Output = (Max - Min) / Xp * e + IPart**

The controller includes algorithms to limit the size of the integral component in case of saturation - **Anti-windup**

==== Usage Notes ====

  * For use in **heating** control, connect the controller as follows
    * SetPoint = Desired value
    * Input = Measured value
  * For use in **cooling** control, connect the controller as follows
    * SetPoint = Measured value
    * Input = Desired value
  * **!** Due to its definition and implementation of anti-windup, the controller **does not support "non-zero" mode**, meaning the range //Min//..//Max// does not include a zero value - this is also indicated by the //InvalidParameters// output

===== Versions =====

{{indexmenu>.005-simplepicontrollerwithen#2}}