FB_HeatingControl - General Information

Overview

Type:	Function block
Available as of:	V1.0.1.0

Task

The function block FB_HeatingControl monitors and controls heating systems.

This function block is the successor of the TemperatureControl_Easy function block which was available in the Packaging Library of SoMachine.

Description

The function block FB_HeatingControl is designed to monitor and control heating systems. This means that the output q_rAnalogOutput can only have values greater than or equal to zero.

The auto-tuning algorithm is based on the so-called relay method. With this method, the process is induced by oscillations. After the completion of three oscillations, the auto-tuning calculates a set of PID parameters.

NOTE: The function block is working independent from the user-defined units, for example, ° C, ° F, Kelvin, mA, or mV. The application must use the same definition and resolution for the set point (i_rSetPoint) and the process value (i_rProcessValue).

Also refer to chapter Auto-Tuning (Heating).

It is important to ensure that the parameters are rational. There is no plausibility verification done by the function block.

WARNING
	UNINTENDED EQUIPMENT OPERATION Verify the validity of the process values. Failure to follow these instructions can result in death, serious injury, or equipment damage.

Set the input i_xEnable to FALSE if an invalid process value is detected (for example if a temperature sensor is no longer connected).

Process temperatures must also be validated.

WARNING
	UNINTENDED EQUIPMENT OPERATION Verify that the maximum allowed process temperature is not exceeded through a second independent temperature monitoring. Failure to follow these instructions can result in death, serious injury, or equipment damage.

The process temperature is not taken into account in open loop operation. This is the case with i_xHold = TRUE or i_xManualMode = TRUE, and i_lrManualValue > 0.

Set the input i_xEnable to FALSE if an over-temperature is detected (for example, by setting an excessive value for i_lrManualValue during manual mode is active).

Interface

Input	Data type	Description
i_xEnable	BOOL	TRUE: Enables function block and parameters are validated. FALSE: Disables function block and all outputs are set to 0 or FALSE. Active in all modes.
i_rSetPoint	REAL	Temperature (in user-defined units) to be maintained by the system. Active in auto and auto-tuning mode. Range: i_stTemperatureControl.rSetPointLowLimit ≤ i_rSetPoint ≤ i_stTemperatureControl.rSetPointHighLimit Default value: 0 [user-defined temperature unit]
i_rProcessValue	REAL	Process temperature value [user-defined temperature unit.] The process temperature value must be scaled outside the function block (for example, with the FB_Scaling of the Toolbox library). Active in auto and auto-tuning mode.
i_xManualMode	BOOL	TRUE: Enables manual mode FALSE: Disables manual mode Active in manual mode. Only takes effect if q_etStatusAutoTune = ET_StatusAutoTune.Inactive.
i_rManualValue	REAL	Manual mode PID output Active in manual mode. Range: i_stTemperatureControlr.PidLowLimit ≤ i_rManualValue ≤ i_stTemperatureControl.rPidHighLimit Default value: 0
i_xAutoTune	BOOL	Enables auto-tuning with a rising edge from FALSE to TRUE. A falling edge does not stop auto-tuning. Active in auto-tuning mode. Default value: FALSE
i_xHold	BOOL	TRUE: Stops the internal PID calculation and holds the output q_rAnalogOutput at the present value. FALSE: Resumes the internal PID calculation. Default value: FALSE Only takes effect if q_etStatusAutoTune = ET_StatusAutoTune.Inactive AND i_xManualMode = FALSE.
i_xReset	BOOL	Certain diagnostic messages can be reset using the input i_xReset. If a diagnostic message cannot be reset by a rising edge of i_xReset, verify and modify the parameter which causes the issue. Active in all modes.
i_stTemperatureControl	ST_TemperatureControl	Includes various parameters needed for temperature control.

NOTE: Executing a reset (rising edge of i_xReset) in case of a PID parameter issue resets the selected PID parameter set to ET_ParameterSetPID.Default (also refer to iq_etSelectParameterSetPID). This means that the PID default parameter set is used.

In-/Output	Data type	Description
iq_etSelectParameterSetPID	ET_ParameterSetPID	It is possible to select one of the 5 PID parameter sets to influence the PID controller behavior. Each set includes different values for the PID parameters (rKp, rTn, rTv, rTd).
iq_stParameterSetsPID	ST_ParameterSetsPID	Structure providing 5 different PID parameter sets.

In-/Output

Data type

Description

iq_etSelectParameterSetPID

ET_ParameterSetPID

It is possible to select one of the 5 PID parameter sets to influence the PID controller behavior.

Each set includes different values for the PID parameters (rKp, rTn, rTv, rTd).

iq_stParameterSetsPID

ST_ParameterSetsPID

Structure providing 5 different PID parameter sets.

NOTE: After auto-tuning is executed successfully, the calculated parameters are available and iq_etSelectParameterSetPID is automatically set to ET_ParameterSetPID.Medium.

Output	Data type	Description
q_xActive	BOOL	Indicates with TRUE that the program code is executing and that it must be executed in each cycle.
q_xReady	BOOL	Indicates with TRUE that the POU is ready and can be controlled via its inputs according to its functionality. After the function block has been activated via a rising edge of i_xEnable, the output q_xReady is only set to TRUE if the function block can process instructions from the inputs.
q_xError	BOOL	Indicates with TRUE that an error has been detected. For details, refer to q_etResult and q_etResultMsg.
q_etResult	ET_Result	Provides diagnostic and status information as an enumeration value.
q_sResultMsg	STRING [80]	Provides additional diagnostic and status information as a text message.
q_rAnalogOutput	REAL	Analog form (signal) of output or manual value (in manual mode). Range: i_stTemperatureControl.rPidLowLimit ≤ q_rAnalogOutput ≤ i_stTemperatureControl.rPidHighLimit
q_xPwmOutput	BOOL	PWM signal according to the output q_rAnalogOutput. TRUE: Heating on FALSE: Heating off
q_xAutoTuneActive	BOOL	TRUE: Auto-tuning active FALSE: Auto-tuning inactive
q_etStatusAutoTune	ET_StatusAutoTune	Current status of auto-tuning as an enumeration value. Default value: ET_StatusAutoTune.Inactive

Diagnostic Messages

The following elements of ET_Result are used for q_etResult.

Name	Data type	Value	Description
Ok	UDINT	0	Operation completed successfully.
SetPointOutOfRange	UDINT	300	i_rSetPoint < rSetPointLowLimit or i_rSetPoint > rSetPointHighLimit
SetPointLowLimitOutOfRange	UDINT	301	rSetPointLowLimit < -100000 or rSetPointLowLimit > rSetPointHighLimit
SetPointHighLimitOutOfRange	UDINT	302	rSetPointHighLimit > 100000 or rSetPointHighLimit < rSetPointLowLimit
ControlModeOutOfRange	UDINT	303	Accepted control mode range: Refer to ET_ParameterSetPID.
ManualValueInvalid	UDINT	304	i_rManualValue < rPidLowLimit or i_rManualValue > rPidHighLimit
CycleTimeInvalid	UDINT	305	Calculated task cycle time must be greater than 0 and less than or equal to 10000 [ms].
DeadBandInvalid	UDINT	306	rDeadBand < 0 or rDeadBand > 100
PidParametersOutOfRange	UDINT	307	One or more PID parameters are out of range
PidControllerIssue	UDINT	308	General issue from the internal PID controller
PwmTimePeriodOutOfRange	UDINT	309	Value rPwmTimePeriod out of range or the value is less than the determined task cycle time.
PidLowLimitOutOfRange	UDINT	310	rPidLowLimit < 0 or rPidLowLimit ≥rPidHighLimit
PidHighLimitOutOfRange	UDINT	311	rPidHighLimit > 100 or rPidHighLimit ≤rPidLowLimit
FilterTimeInvalid	UDINT	312	Invalid value for rDigitalFilterTime
AutoTuneHysteresisInvalid	UDINT	313	Invalid value for rAutoTuneHysteresis