pid.h File Reference

PID controller header file. More...

#include "stdint.h"

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Classes
struct	pidData
	PID Status. More...

Macros
#define	SCALING_FACTOR   256
	Scaling division factor for PID controller.
#define	SCALING_FACTOR_ENABLED   FALSE
	Flag indicating whether scaling factor is enabled for PID controller.
#define	MAX_INT   32767
	Maximum value of integers.
#define	MAX_LONG   2147483647L
	Maximum value of long integers.
#define	MAX_I_TERM   (MAX_LONG - (2 * (int32_t)MAX_INT))
	Maximum value of the I-term.
#define	FALSE   0
	FALSE constant.
#define	TRUE   (!FALSE)
	TRUE constant.

Typedefs
typedef struct pidData	pidData_t
	PID Status.

Functions
void	PIDInit (int16_t p_factor, int16_t i_factor, int16_t d_factor, pidData_t *pid)
	Initialisation of PID controller parameters.
uint16_t	PIDController (int16_t setPoint, int16_t processValue, pidData_t *pid_st)
	PID control algorithm.
void	PIDResetIntegrator (pidData_t *pid_st)
	Resets the integrator in the PID regulator.

Detailed Description

PID controller header file.

This file contains defines, typedefs and prototypes for the PID controller.

Author

Nexperia: http://www.nexperia.com

Support Page

For additional support, visit: https://www.nexperia.com/support

Author

Aanas Sayed

Date

2024/03/08

Definition in file pid.h.

Macro Definition Documentation

FALSE

#define FALSE   0

FALSE constant.

Definition at line 90 of file pid.h.

MAX_I_TERM

#define MAX_I_TERM   (MAX_LONG - (2 * (int32_t)MAX_INT))

Maximum value of the I-term.

This limits the maximum positive or negative value of the I-term. Changing this value leads to a different integral anti-windup limit. Do not increase this value from its default, as it is already at the limit of the underlying data types.

Definition at line 86 of file pid.h.

MAX_INT

#define MAX_INT   32767

Maximum value of integers.

Definition at line 74 of file pid.h.

MAX_LONG

#define MAX_LONG   2147483647L

Maximum value of long integers.

Definition at line 77 of file pid.h.

SCALING_FACTOR

#define SCALING_FACTOR   256

Scaling division factor for PID controller.

Scaling division factor for the PID controller. The P, I and D gains will be divided by this number.

Definition at line 33 of file pid.h.

SCALING_FACTOR_ENABLED

#define SCALING_FACTOR_ENABLED   FALSE

Flag indicating whether scaling factor is enabled for PID controller.

The scaling factor can be adjusted by modifying the value of SCALING_FACTOR.

Definition at line 40 of file pid.h.

TRUE

#define TRUE   (!FALSE)

TRUE constant.

Definition at line 93 of file pid.h.

Typedef Documentation

pidData_t

typedef struct pidData pidData_t

PID Status.

Set points and data used by the PID control algorithm

Function Documentation

PIDController()

uint16_t PIDController	(	int16_t	setPoint,
		int16_t	processValue,
		pidData_t *	pid_st )

PID control algorithm.

Calculates output from set point, process value, and PID status.

Parameters

setPoint	Desired value.
processValue	Measured value.
pid_st	PID status struct.

Returns

Calculated control output as a 16-bit unsigned integer.

Definition at line 54 of file pid.cpp.

{
  int32_t ret;
  int32_t temp;
  int16_t error;
 
  error = setPoint - processValue;
 
  // Calculate "P" term and limit error overflow
  if (error > pid_st->maxError)
  {
    pid_st->p_term = MAX_INT;
  }
  else if (error < -pid_st->maxError)
  {
    pid_st->p_term = -MAX_INT;
  }
  else
  {
    pid_st->p_term = pid_st->P_Factor * error / 1000;
  }
 
  // Calculate "I" term and limit integral runaway
  temp = pid_st->sumError + error;
  if (temp > pid_st->maxSumError)
  {
    pid_st->i_term = MAX_I_TERM;
    pid_st->sumError = pid_st->maxSumError;
  }
  else if (temp < -pid_st->maxSumError)
  {
    pid_st->i_term = -MAX_I_TERM;
    pid_st->sumError = -pid_st->maxSumError;
  }
  else
  {
    pid_st->sumError = temp;
    pid_st->i_term = pid_st->I_Factor * pid_st->sumError / 1000;
  }
 
#if (PID_K_D_ENABLE == TRUE)
  // Calculate "D" term
  pid_st->d_term = pid_st->D_Factor * (pid_st->lastProcessValue - processValue) / 1000;
#endif
 
  pid_st->lastProcessValue = processValue;
 
#if (PID_K_D_ENABLE == TRUE)
  ret = (pid_st->p_term + pid_st->i_term + pid_st->d_term);
#else
  ret = (pid_st->p_term + pid_st->i_term);
#endif
 
#if (SCALING_FACTOR_ENABLED == TRUE)
  ret = ret / SCALING_FACTOR;
#endif
  if (ret > MAX_INT)
  {
    ret = MAX_INT;
  }
  // Since the return type is uint16_t
  else if (ret < 0)
  {
    ret = 0;
  }
 
  return ((uint16_t)ret);
}

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PIDInit()

void PIDInit	(	int16_t	p_factor,
		int16_t	i_factor,
		int16_t	d_factor,
		pidData_t *	pid )

Initialisation of PID controller parameters.

Initialise the variables used by the PID algorithm.

Parameters

p_factor	Proportional term.
i_factor	Integral term.
d_factor	Derivate term.
pid	Struct with PID status.

Definition at line 31 of file pid.cpp.

{
  // Start values for PID controller
  pid->sumError = 0;
  pid->lastProcessValue = 0;
  // Tuning constants for PID loop
  pid->P_Factor = p_factor;
  pid->I_Factor = i_factor;
  pid->D_Factor = d_factor;
  // Limits to avoid overflow
  pid->maxError = MAX_INT / pid->P_Factor;
  pid->maxSumError = MAX_I_TERM / pid->I_Factor;
}

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PIDResetIntegrator()

void PIDResetIntegrator

(

pidData_t *

pid_st

)

Resets the integrator in the PID regulator.

Calling this function will reset the integrator in the PID regulator.

Parameters

pid_st

Pointer to the PID status struct for which the integrator will be reset.

Definition at line 130 of file pid.cpp.

{
  pid_st->sumError = 0;
  pid_st->p_term = 0;
  pid_st->i_term = 0;
#if (PID_K_D_ENABLE == TRUE)
  pid_st->d_term = 0;
#endif
}