FB_BasicPID

Transfer function:

Action diagram:

VAR_INPUT

VAR_INPUT
    fSetpointValue  : LREAL; (* setpoint value *)
    fActualValue    : LREAL; (* actual value *)
    bReset          : BOOL;
    fCtrlCycleTime  : LREAL; (* controller cycle time in seconds [s] *)
    fKp             : LREAL; (* proportional gain Kp (P) *)
    fTn             : LREAL; (* integral gain Tn (I) [s] *)
    fTv             : LREAL; (* derivative gain Tv (D-T1) [s] *)
    fTd             : LREAL; (* derivative damping time Td (D-T1) [s] *)
END_VAR

fSetpointValue                  : Setpoint value of the controlled variable.

fActualValue                     : Actual value of the controlled variable.

bReset                                : TRUE at this input resets the internal state variables as well as the output of the controller.

fCtrlCycleTime                  : Controller cycle time for discrete-time implementation [s].

                                                       It is required to set this value equal to the task cycle time of the PLC task, if the function block is called every PLC cycle.

                                                       Otherwise the appropriate multiple of the PLC task cycle time has to be used.

fKp                                       : Proportional amplification 

fTn                                       : Integral-action time [s]

fTv                                       : Derivative action time [s]

fTd                                       : Damping time [s]

VAR_OUTPUT

VAR_OUTPUT
    fCtrlOutput     : LREAL;
    nErrorStatus    : UINT
END_VAR

fCtrlOutput         : output of thePID element.

nErrorStatus     : Provides the error number, if an error exists (nErrorStatus <> 0).

0 = nERR_NOERROR                           : no error.
1 = nERR_INVALIDPARAM                 : invalid parameter
2 = nERR_INVALIDCYCLETIME          : Invalid cycle time

Requirements