PID Control C51 Program (2)

This is a typical PID processing program found on the Internet. When using a single-chip microcomputer as a control CPU, please simplify it a little. The specific PID parameters must be determined by the specific object through experiments. Due to the processing speed and RAM resource limitations of the single-chip microcomputer, floating-point operations are generally not used. Instead, all parameters are integers, and the calculation is divided by a 2-N-th power data (equivalent to shift) at the end, and similar fixed-point operations are performed, which can greatly improve the calculation speed. According to the different requirements of control accuracy, when the accuracy requirement is very high, pay attention to retaining the "remainder" caused by the shift and make good remainder compensation. This program is just the basic framework of the commonly used PID algorithm, and does not include the input and output processing part.
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#i nclude
#i nclude
/*====================================================================== ==========
     PID Function
    
     The PID (proportional, integral, differential) 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; // Set target Desired Value

         double Proportion; // Proportional Cons t
         double Integral; // Integral constant Integral Const
         double Derivative; // Derivative constant Derivative Const

         double LastError; // Error[-1]
         double PrevError; // Error[-2]
         double SumError; // Sums of Errors

} PID;

/*============================================================================================================
   PID calculation part
=============================================================== )

{
double
     dError,
             Error;

         Error = pp->SetPoint - NextPoint; // Deviation
         pp->SumError += Error; // Integral
         dError = pp->LastError - pp->PrevError; // Current differential
         pp->PrevError = pp->LastError;
         pp->LastError = Error;
         return (pp->Proportion * Error // Proportional term
             + pp->Integral * pp->SumError // Integral term
             + pp->Derivative * dError // Derivative term
         );
}

/*=
   ...
===================================================================================================*/

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
     }
}

Expanded critical proportion method to determine PID coefficients??
Use proportional control to form a closed-loop system, and gradually increase the proportional coefficient from small to large, so that the closed-loop system is in a critical oscillation state (stable boundary). The critical oscillation state waveform is shown in Figure 2. The oscillation period in this state is Tc = 0.0396 s.
According to the empirical formula to determine the range, the characteristics of the Zhoushan DC transmission system composed of a single-bridge converter determine that the system is only controlled when the pulse triggers the valve to commutate, that is, once every 3.3 ms, that is, Ts = 3.3 ms, that is, Ts = 0.083 Tc. According to the empirical formula provided in Table 1, the above situation is close to Ts = 0.09 Tc, and the approximate range of the PID coefficient is Kp = 1 800, Ki = 370, and Kd = 4 000.
Table 1 The range of PID controller parameters of the extended critical proportion method
Ts Kp Ti Td
0.014Tc 0.63Kpc 0.49Tc 0.14Tc
0.043Tc 0.47Kpc 0.47Tc 0.16Tc 0.090Tc 0.34Kpc
0.43Tc 0.20Tc 0.160Tc
0.27Kpc 0.40Tc 0.22Tc