FB_CTRL_PI_PID

FB_CTRL_PI_PID 1:

The function block provides a cascaded PI-PID controller in the functional diagram. Internally, this function block uses the FB_CTRL_PI, FB_CTRL_LIMITER and FB_CTRL_PID transfer elements.

Transfer function of the PI element

Transfer function of the PID-element

Functional diagram for the cascaded transfer element

FB_CTRL_PI_PID 4:

Inputs

VAR_INPUT
    fSetpointValue           : FLOAT;
    fActualValueOuterLoop    : FLOAT;
    fActualValueInnerLoop    : FLOAT;
    fPreControl              : FLOAT;
    fManSyncValueInnerLoop   : FLOAT;
    bSyncInnerLoop           : BOOL; 
    eModeInnerLoop           : E_CTRL_MODE;
    bHoldInnerLoop           : BOOL;
    fManSyncValueOuterLoop   : FLOAT;
    bSyncOuterLoop           : BOOL;
    eModeOuterLoop           : E_CTRL_MODE; 
    bHoldOuterLoop           : BOOL; 
END_VAR

Name	Type	Description
fSetpointValue	FLOAT	Setpoint of the controlled variable
fActualValueOuterLoop	FLOAT	The actual value of the controlled variable that is fed back to the PI controller of the outer control loop.
fActualValueInnerLoop	FLOAT	The actual value of the controlled variable that is fed back to the PID controller of the inner control loop.
fPreControl	FLOAT	Pre-control that is connected behind the PI controller.
fManSyncValueInnerLoop	FLOAT	Input, to whose value it is possible to set the internal state of the PID-element (the inner control loop).
bSyncInnerLoop	BOOL	A rising edge at this input sets the PID-element (the inner control loop) to the value "fManSyncValueInnerLoop".
eModeInnerLoop	E_CTRL_MODE	Input that specifies the operation mode of the PID-element (the inner control loop).
bHoldInnerLoop	BOOL	A TRUE at this input holds the internal state of the PID-element (the inner control loop) constant at the current value.
fManSyncValueOuterLoop	FLOAT	Input, to whose value it is possible to set the internal state of the PI element (the outer control loop).
bSyncOuterLoop	BOOL	A rising edge at this input sets the PI element (the outer control loop) to the value "fManSyncValueOuterLoop".
eModeOuterLoop	E_CTRL_MODE	Input that specifies the operation mode of the PI element (the outer control loop).
bHoldOuterLoop	BOOL	A TRUE at this input holds the internal state of the PI element (the outer control loop) constant at the current value.

Outputs

VAR_OUTPUT
    fOut                   : FLOAT;
    eStateInnerLoop        : E_CTRL_STATE;
    bARWactiveInnerLoop    : BOOL;
    eErrorIdInnerLoop      : E_CTRL_ERRORCODES;
    bErrorInnerLoop        : BOOL;
    eStateOuterLoop        : E_CTRL_STATE;
    bARWactiveOuterLoop    : BOOL;
    eErrorIdOuterLoop      : E_CTRL_ERRORCODES;
    bErrorOuterLoop        : BOOL;
END_VAR

Name	Type	Description
fOut	FLOAT	Output of the PI-PID-element
eStateInnerLoop	E_CTRL_STATE	State of the internal PID-element (inner control loop)
bARWactive InnerLoop	BOOL	A TRUE at this output indicates that the output of the PID-element (the inner control loop) is being restricted.
eErrorIdInnerLoop	E_CTRL_ERROR CODES	Returns the error number of the PID-element (the inner control loop) when the `bError` output is set.
bErrorInnerLoop	BOOL	Is set to TRUE as soon as an error occurs in the PID-element (the inner control loop).
eStateOuterLoop	E_CTRL_STATE	State of the internal PI element (outer control loop)
bARWactiveOuterLoop	BOOL	A TRUE at this output indicates that the PI element's (the outer control loop) output is being restricted.
eErrorIdOuterLoop	E_CTRL_ERRORCODES	Returns the error number of the PI element (the outer control loop) when the `bError` output is set.
bErrorOuterLoop	BOOL	Is set to TRUE as soon as an error occurs in the PI element (the outer control loop).

Inputs/ outputs

VAR_IN_OUT
    stParams        : ST_CTRL_PI_PID_PARAMS;
END_VAR

Name	Type	Description
stParams	ST_CTRL_PI_PID_PARAMS	Parameter structure of the PI-PID-element

stParams consists of the following elements:

TYPE
ST_CTRL_PI_PID_PARAMS :
STRUCT
    tCtrlCycleTime         : TIME := T#0ms;
    tTaskCycleTime         : TIME := T#0ms;
    fKp_OuterLoop          : FLOAT := 0;
    tTn_OuterLoop          : TIME := T#0s;
    fMaxLimit_OuterLoop    : FLOAT := 1E38;
    fMinLimit_OuterLoop    : FLOAT := -1E38;
    fKp_InnerLoop          : FLOAT := 0;
    tTn_InnerLoop          : TIME := T#0ms; 
    tTv_InnerLoop          : TIME := T#0ms; 
    tTd_InnerLoop          : TIME := T#0ms; 
    fMaxLimit_InnerLoop    : FLOAT := 1E38;
    fMinLimit_InnerLoop    : FLOAT := -1E38;
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.
fKp_OuterLoop	FLOAT	Controller amplification / controller coefficient of the PI element (outer control loop)
tTn_OuterLoop	TIME	Integral action time of the internal PI element (outer control loop). The I-component is deactivated if this is parameterized as T#0s.
fMaxLimit_OuterLoop	FLOAT	Upper limit at which integration in the PID-element is halted and to which the output is limited (ARW measure). Reaching this limit is indicated by a TRUE at the `bARWactiveOuterLoop` output.
fMinLimit_OuterLoop	FLOAT	Lower limit at which integration in the PID-element is halted and to which the output is limited (ARW measure). Reaching this limit is indicated by a TRUE at the `bARWactiveOuterLoop` output.
fKp_InnerLoop	FLOAT	Controller amplification / controller coefficient of the PID element (inner control loop)
tTn_InnerLoop	TIME	Integral action time of the PID-element (inner control loop). The I-component is deactivated if this is parameterized as T#0s.
tTv_InnerLoop	TIME	Derivative action time of the PID-element (inner control loop). The D-component is deactivated if this is parameterized as T#0s.
tTd_InnerLoop	TIME	Damping time of the PID-element (inner control loop)
fMaxLimit_InnerLoop	FLOAT	Upper limit at which integration in the PID-element is halted and to which the output is limited (ARW measure). Reaching this limit is indicated by a TRUE at the `bARWactiveInnerLoop` output.
fMinLimit_InnerLoop	FLOAT	Lower limit at which integration in the PID-element is halted and to which the output is limited (ARW measure). Reaching this limit is indicated by a TRUE at the `bARWactiveInnerLoop` output.