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# ControlPIext
## `ControlPIext` (FB)
FUNCTION\_BLOCK ControlPIext
### Short description
> Proportional-integral acting controller (PI controller), parameters as inputs.\
> The direction of action (inverted / direct) is also adjustable.\
> Typical application: control loops with actuators that have no storing character.
### Representation
### Interfaces
#### Inputs
| Name | Data type | Value range | Initial value | Function |
| -------------- | --------- | ----------- | ------------- | ------------------------------------------ |
| *rX* | REAL | | | Analog measured value |
| *rW* | REAL | | | Analog setpoint |
| *xEn* | BOOL | | | Enable of the controller |
| **rYDisabled** | REAL | | 0.0 | Disabled value |
| **rInitValue** | REAL | | 0.0 | Initialization value for the output signal |
| **rKp** | REAL | 0.0 … | 2.0 | Gain factor |
| **rTn** | REAL | 0.0 … | 200.0 | Reset time in seconds |
| **rMin** | REAL | | 0.0 | Lower absolute limit of the output signal |
| **rMax** | REAL | | 100.0 | Upper absolute limit of the output signal |
#### Outputs
| Name | Data type | Value range | Initial value | Function |
| -------------- | --------- | ----------- | ------------- | -------------------------------------- |
| *rY* | REAL | | 0.0 | Controller output signal |
| *rDiff* | REAL | | | Control deviation |
| *rPartP* | REAL | | | Proportional part of the output signal |
| *rPartI* | REAL | | | Integral part of the output signal |
| *xLimitActive* | BOOL | | | Status - limit exceeded |
#### Setpoints / parameters
| Name | Data type | Value range | Initial value | Function |
| ------------- | ------------ | ----------- | --------------------- | -------------------------------------------------------- |
| **rOffset** | REAL | | 0.0 | Offset |
| **eAction** | eControlMode | | eControlMode.Inverted | Direction of action of the controller (Inverted, Direct) |
| **eManModeN** | eManNum | | eManNum.Auto | Operating mode for the controller output signal |
| **rManValue** | REAL | | | Output signal in manual mode |
### Function description
#### General
This function block contains a proportional-integral acting controller (PI controller).\
Some parameters are defined as inputs and thus not persistent. This allows the values to be changed continuously by the program.\
The controller's output signal *rY* is calculated when the controller is enabled (*xEn* = TRUE) and in the controller's automatic operating mode (**eManModeN** = eManNum.Auto) as follows:\
\
\
Output signal: *rY* = Proportional part + Integral part\
\
\
Proportional part: Proportional part = **rKp** \* control deviation\
\
Control deviation: Control deviation = *rW* - (*rx* + **rOffset**) \[Direction of action - Inverted: **eAction** = eControlMode.Inverted]\
\
Control deviation = *rX* - (*rW* + **rOffset**) \[Direction of action - Direct: **eAction** = eControlMode.Direct]\
\
Integral part: Integral part = (Proportional part \* (sampling time / reset time)) + Integral part (t-sampling time)\
\
\
Legend: t-sampling time … time point that was one sampling time before the current time t\
Sampling time … time interval between two calls of the function block\
t … current time
> **Control / Properties - reset time rTn**
>
> It may only take values > 0.\
> **rTn** >>> Sampling time: The integral part remains constant\
> Control deviation = 0: The integral part remains constant\
> Depending on the controller's direction of action **eAction** the measured and set values are determined as follows:
>
> \
> \| \*\*eAction\*\* | Control deviation | Function | |-------------------------|-------------------------------|-----------------------| | eControlMode.Inverted | \*rW\* - ( \*rx\* + \*\*rOffset\*\* ) | Direction of action - Inverted | | eControlMode.Direct | \*rX\* - ( \*rW\* + \*\*rOffset\*\* ) | Direction of action - Direct |
#### Integral part
The integral part is limited both upwards and downwards by the following absolute limits:\
Upper limit = **rMax** - Proportional part\
Lower limit = **rMin** - Proportional part
#### Enable input *xEn*
If the enable input is not active (*xEn* = FALSE) the disabled value **rYDisabled** is transferred to the output *rY* (precondition: **eManModeN** = eManNum.Auto) and limited by the absolute limits. The integral part is set to 0.0.\
\
If the enable input is active (*xEn* = TRUE) the output signal is calculated according to the formula above and passed to the output *rY* (precondition: **eManModeN** = eManNum.Auto) and limited by the absolute limits.\
\
On each rising edge of the enable input *xEn* the control process is restarted.
#### Restart of the controller
On each rising edge of the enable input *xEn* the control process is restarted. (Preconditions: **eManModeN** = eManNum.Auto and *xEn* = TRUE)\
The integral part is set to the difference between **rInitValue** and the proportional part.
#### Control deviation *rDiff*
The control deviation corresponds to the value of the control deviation according to the above formula.
#### Proportional part of the output signal *rPartP*
This output always provides the proportional part of the output signal, see description above.
#### Integral part of the output signal *rPartI*
This output always provides the integral part of the output signal, see description above.
#### Absolute limits **rMin** and **rMax**
The controller's output signal *rY* is limited downwards by the absolute limit **rMin** and upwards by **rMax** .\
The absolute limit **rMin** is set to the current value of **rMax** - 0.1 if it is >= the current value of **rMax** .\
The only exception is manual operation for the controller output signal (**eManModeN** = eManNum.Man).
#### Status - limit exceeded *xLimitActive*
The limit-exceeded status is activated (*xLimitActive* = TRUE) if a limit is exceeded upwards or downwards (*xEn* = TRUE).\
The limit-exceeded status is not activated (*xLimitActive* = FALSE) if no limit is exceeded or the enable signal is deactivated (*xEn* = FALSE).\
\
A limit is considered exceeded if the controller's output signal *rY* reaches / exceeds the upper limit **rMax** or reaches / falls below the lower limit **rMin** .
#### Operating mode for the controller output signal **eManModeN**
The parameter **eManModeN** allows switching the output signal *rY* from automatic to manual mode and vice versa.\
In manual mode the output signal *rY* takes over the output signal in manual mode **rManValue**. The integral part is set to the difference between **rInitValue** and the proportional part.
| **eManModeN** | *rY* | Function |
| ------------- | -------------------------------------------- | ------------------------------ |
| eManNum.Auto | signal according to formula / disabled value | Automatic mode - output signal |
| eManNum.Man | **rManValue** | Manual mode - output signal |
### Codesys
InOut:
| Scope | Name | Type | Initial |
| ----------- | ------------- | ------------ | --------------------- |
| Input | `rX` | `REAL` | |
| Input | `rW` | `REAL` | |
| Input | `xEn` | `BOOL` | |
| Input | `rYDisabled` | `REAL` | 0 |
| Input | `rInitValue` | `REAL` | 0 |
| Input | `rKp` | `REAL` | 2 |
| Input | `rTn` | `REAL` | 200 |
| Input | `rYMin` | `REAL` | 0 |
| Input | `rYMax` | `REAL` | 100 |
| Input Const | `rOffset` | `REAL` | 0 |
| Input Const | `eAction` | eControlMode | eControlMode.Inverted |
| Input Const | `eManModeN` | eManNum | eManNum.Auto |
| Input Const | `rManValue` | `REAL` | |
| Output | `rY` | `REAL` | 0 |
| Output | `rDiff` | `REAL` | |
| Output | `rPartP` | `REAL` | |
| Output | `rPartI` | `REAL` | |
| Output | `xLimitAktiv` | `BOOL` | |
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