***************************************************************************\    PID FunctionThis program has been written by the Technical Support Staff at Z-World inresponse to several customer requests.  As such, it has NOT had the testing andvalidation procedures which our "standard" software products have.  It is beingmade available as a sample.  There is no warranty, implied or otherwise.    The PID (Proportional Integral Derivative) function is used in mainly    control applications. PIDCalc performs one iteration of the PID    algorithm.    While the PID function works, main is just a dummy program showing    a typical usage.\***************************************************************************/typedef struct PID{    double    SetPoint;        // Desired Value    double    Proportion;        // Proportional Const    double    Integral;        // Integral Const    double    Derivative;        // Derivative Const    double    LastError;        // Error[-1]    double    PrevError;        // Error[-2]    double    SumError;        // Sums of Errors}  PID;/*=========================================================================*\    Perform One PID Iteration\*=========================================================================*/double PIDCalc ( PID    *pp,   double NextPoint ){  double    dError, Error;    pp->SumError += (Error = pp->SetPoint - NextPoint);    dError = pp->LastError - pp->PrevError;    pp->PrevError = pp->LastError;    pp->LastError = Error;    return    (  pp->Proportion * Error                    +  pp->Integral * pp->SumError                    +  pp->Derivative * dError                );}/*=========================================================================*\    Initialize PID Structure\*=========================================================================*/void PIDInit  ( PID *pp ){      memset ( pp,0,sizeof(PID) );}/***************************************************************************\    Main Program\***************************************************************************/double sensor ( void )                        // Dummy Sensor Function{      return 100.0;}void actuator ( double rDelta )            // Dummy Actuator Function{}void main ( void ){    PID            sPID;                             // PID Control Structure    double        rOut;                             // PID Response (Output)    double        rIn;                             // PID Feedback (Input)    PIDInit ( &sPID );                        // Initialize Structure    sPID.Proportion    = 0.5;                // Set PID Coefficients    sPID.Integral      = 0.5;    sPID.Derivative    = 0.0;    sPID.SetPoint      = 100.0;                // Set PID Setpoint    for (;;)                                        // Mock Up of PID Processing    {    rIn = sensor ();                        // Read Input        rOut = PIDCalc ( &sPID,rIn );        // Perform PID Interation        actuator ( rOut );                    // Effect Needed Changes    }}這個PID的算法只能滿足一般控制的場合，如果您要用于實際工程的話，還需要根據實際需求進行修改。