+lasterror +preverror
i have a pid routine in c here. i got it from the net as well. hope this helps.
/***************************************************************************\
PID Function
Author : Greg Young, Z-World.
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
}
}