FB_CTRL_2POINT_PWM_ADAPTIVE

FB_CTRL_2POINT_PWM_ADAPTIVE 1:

The function block provides an adaptive two-position controller. It is particularly suitable for single-area controllers in which high inlet temperatures are present and which make use of a thermal actuator.

Behavior of the output

FB_CTRL_2POINT_PWM_ADAPTIVE 2:

Description of the function

Internally, the controller uses a PWM function block that is used to control the thermal actuator. The mark-to-space ratio of the PWM function block is adaptively adjusted to the behavior of the controlled system. The PWM output is switched on when the control deviation "fE = setpoint – actual value" is greater than "0" and switched off when the control deviation is less than "0". The mark-to-space ratio is not changed as long as the control deviation remains within the range "[-fOkRange ... fOkRange]". If "fE > fOkRange", the mark-to-space ratio is increased by "fStepSize". After such an increase, time tWaitTime must elapse before the mark-to-space ratio can be changed again. If fE falls below "-fOkRange", the mark-to-space ratio is reduced by "fStepSize". The mark-to-space ratio is only modified over the range "[fMinLimit ... fMaxLimit]". The period of the PWM signal is specified by the parameter tPWMPeriod.

VAR_INPUT

VAR_INPUT
    fSetpointValue    : FLOAT;
    fActualValue      : FLOAT;
    fManSyncValue     : FLOAT;
    bSync             : BOOL;
    eMode             : E_CTRL_MODE;
END_VAR

Name	Type	Description
fSetpointValue	FLOAT	Setpoint of the controlled variable
fActualValue	FLOAT	Actual value of the controlled variable
fManSync Value	FLOAT	Input to which the controller's mark-to-space ratio can be set, or with which the output can be set in Manual Mode. The output is set in Manual Mode if "fManSyncValue > 0.0".
bSync	BOOL	A rising edge at this input will set the mark-to-space ratio of the internal PWM function block to the value "fManSyncValue".
eMode	E_CTRL_MODE	Input that specifies the operation mode of the function block.

VAR_OUTPUT

VAR_OUTPUT
    bOut           : BOOL;
    fPWMDutyCycle  : FLOAT; 
    eState         : E_CTRL_STATE;
    eErrorId       : E_CTRL_ERRORCODES;
    bError         : BOOL;
END_VAR

Name	Type	Description
bOut	BOOL	Controller output
fPWMDutyCycle	FLOAT	Current mark-to-space ratio of the internal PWM function block
eState	E_CTRL_STATE	State of the function block
eErrorId	E_CTRL_ERROR CODES	Supplies the error number when the output `bError` is set.
bError	BOOL	Becomes TRUE, as soon as an error occurs.

VAR_IN_OUT

VAR_IN_OUT
    stParams    : ST_CTRL_2POINT_PWM_ADAPTIVE_PARAMS;
END_VAR

Name	Type	Description
stParams	ST_CTRL_2POINT_PWM_ ADAPTIVE_ PARAMS	Parameter structure of the 2-point element

stParams consists of the following elements:

TYPE
ST_CTRL_2POINT_PWM_ADAPTIVE_PARAMS:
STRUCT
    tCtrlCycleTime    : TIME := T#0ms; 
    tTaskCycleTime    : TIME := T#0ms; 
    tPWMPeriod        : TIME;
    fOkRange          : FLOAT;
    fForceRange       : FLOAT;
    fStepSize         : FLOAT;
    fMinLimit         : FLOAT;
    fMaxLimit         : FLOAT;
    tWaitTime         : TIME;
END_STRUCT
END_TYPE

Name	Type	Description
tCtrlCycleTime	TIME	Cycle time with which the control loop is processed. This must be greater than or equal to the TaskCycleTime. The function block uses this input value to calculate internally whether the state and the output values have to be updated in the current cycle.
tTaskCycleTime	TIME	Cycle time with which the function block is called. If the function block is called in every cycle this corresponds to the task cycle time of the calling task.
tPWMPeriod	TIME	Period of the PWM signal
fOkRange	FLOAT	The range of "fE" over which the mark-to-space ratio will not be modified.
fForceRange	FLOAT	If "fE" exceeds this range, the output is permanently set to TRUE.
fStepSize	FLOAT	Value by which the mark-to-space ratio is varied each time it is adapted. [0% ... 100%]
fMinLimit	FLOAT	Maximum mark-to-space ratio in percent [0% ... 100%]
fMaxLimit	FLOAT	Minimum mark-to-space ratio in percent [0% ... 100%]
tWaitTime	TIME	Waiting time between individual modifications of the mark-to-space ratio