FB_CTRL_STEP_PID

The function block controls a digitally manipulated variable for the integration of actuators. It is based on a standard PID controller with an additional binary output signal in conjunction with the analog output and works without a precise position feedback signal.

The position feedback signal required to calculate the controller output is estimated using the limiting values and the time required to reach these limits. The function block then generates pulses that are required to drive the actuator as a servomotor.

VAR_INPUT

VAR_INPUT
    fSetpointValue        : LREAL;
    fActualValue          : LREAL;
    bLimitSwitchPos       : BOOL;
    bLimitSwitchNeg       : BOOL;
    bAutoReset            : BOOL;
    nSensorType           : E_CTRL_STEP_SENSORTYPES;
    fDisturbanceValue     : REAL;
    bManualDigitalPos     : BOOL;
    bManualDigitalNeg     : BOOL;
    eMode                 : E_CTRL_MODE;
END_VAR

Name	Type	Description
fSetpointValue	LREAL	Setpoint of the controlled variable
fActualValue	LREAL	Actual value of the control value
bLimitSwitchPos	BOOL	Limit switch, becomes TRUE when the upper stop is reached.
bLimitSwitchNeg	BOOL	Limit switch, becomes TRUE when the lower stop is reached.
bAutoReset	BOOL	If the variable is TRUE, it resets the controller to initial conditions.
nSensorType	E_CTRL_STEP_ SENSORTYPES	Enables the selection of the correct thermocouple type.
fDisturbance Value	REAL	Actual value of the disturbance variable
bManualDigital Pos	BOOL	If the variable is TRUE, the motor is manually set to the positive direction
bManualDigital Neg	BOOL	If TRUE, the motor is manually set to the negative direction
eMode	E_CTRL_MODE	Input specifying the operation mode of the controller

VAR_OUTPUT

VAR_OUTPUT
    bCtrlDigitalPos   : BOOL;
    bCtrlDigitalNeg   : BOOL;
    fCtrlAnalog       : LREAL;
    eState            : E_CTRL_STATE;
    eErrorId          : E_CTRL_ERRORCODES;
    bError            : BOOL;
    bBusy             : BOOL;
    bMinLimitNeg      : BOOL;
    bMinLimitPos      : BOOL;
    bARWActive        : BOOL;
END_VAR

Name	Type	Description
bCtrlDigitalPos	BOOL	Output required to run the motor in a positive direction.
bCtrlDigitalNeg	BOOL	Output required to run the motor in a negative direction.
fCtrlAnalog	LREAL	Analog output of the controller
eState	E_CTRL_STATE	Actual state of the controller
eErrorId	E_CTRL_ERRORCODES	Returns the error number if `bError` is TRUE.
bError	BOOL	TRUE if an error occurs in the function block.
bBusy	BOOL	TRUE when the function block is active.
bMinLimitNeg	BOOL	TRUE at this output indicates that the controller has reached its minimum limit value.
bMinLimitPos	BOOL	TRUE at this output indicates that the controller has reached its maximum limit value.
bARWActive	BOOL	TRUE at this output indicates that the controller is currently restricted.

VAR_IN_OUT

VAR_IN_OUT
    stCtrlParams    : ST_CTRL_STEP_PID_PARAMS;
END_VAR

Name	Type	Description
stCtrlParams	ST_CTRL_STEP_PID_PARAMS	Parameter structure of the controller.

stCtrlParams consists of the following elements:

TYPE ST_CTRL_STEP_PID_PARAMS:
STRUCT
    tCtrlCycleTime     : TIME;
    tTaskCycleTime     : TIME;
    fKp                : REAL;
    fTn                : REAL;
    fTv                : REAL;
    fTd                : REAL;
    fTM                : REAL;
    fDeadBandWidth     : REAL;
    tMinimumPulseTime  : TIME;
    tFilterTime        : TIME;
    fWmax              : REAL;
    fWmin              : REAL;
    fYMax              : REAL;
    fYMin              : REAL;
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 for internal calculation to determine whether the state and output values have been 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.
fKp	REAL	Controller gain or proportional gain
fTn	REAL	Integral action time: The I component is disabled if this parameter is zero.
fTv	REAL	Derivative action time; the D component is disabled if this parameter is zero.
fTd	REAL	Damping time
fTM	REAL	Digital valve actuation time in seconds
fDeadBandWidth	REAL	Permissible width of the controller deviation
tMinimumPulse Time	TIME	Minimum pulse time for pulse generator
tFilterTime	TIME	Filter time for actual value filter
fWmax	REAL	Maximum setpoint in °C
fWmin	REAL	Minimum setpoint in °C
fYMax	REAL	Maximum value of the controller output
fYMin	REAL	Minimum value of controller output