nuttx/libs/libdsp/lib_pid.c

/****************************************************************************
 * control/lib_pid.c
 *
 *   Copyright (C) 2018 Gregory Nutt. All rights reserved.
 *   Author: Mateusz Szafoni <raiden00@railab.me>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <string.h>

#include <dsp.h>

/****************************************************************************
 * Pre-processor Definitions
 ****************************************************************************/

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: pid_controller_init
 *
 * Description:
 *   Initialize PID controller. This function does not initialize saturation
 *   limits.
 *
 * Input Parameters:
 *   pid - (out) pointer to the PID controller data
 *   KP  - (in) proportional gain
 *   KI  - (in) integral gain
 *   KD  - (in) derivative gain
 *
 * Returned Value:
 *   None
 *
 ****************************************************************************/

void pid_controller_init(FAR pid_controller_t *pid, float KP, float KI,
                         float KD)
{
  /* Reset controller data */

  memset(pid, 0, sizeof(pid_controller_t));

  /* Copy controller parameters */

  pid->KP = KP;
  pid->KI = KI;
  pid->KD = KD;
}

/****************************************************************************
 * Name: pi_controller_init
 *
 * Description:
 *   Initialize PI controller. This function does not initialize saturation
 *   limits.
 *
 * Input Parameters:
 *   pid - (out) pointer to the PID controller data
 *   KP  - (in) proportional gain
 *   KI  - (in) integral gain
 *
 * Returned Value:
 *   None
 *
 ****************************************************************************/

void pi_controller_init(FAR pid_controller_t *pid, float KP, float KI)
{
  /* Reset controller data */

  memset(pid, 0, sizeof(pid_controller_t));

  /* Copy controller parameters */

  pid->KP = KP;
  pid->KI = KI;
  pid->KD = 0.0;
}

/****************************************************************************
 * Name: pid_saturation_set
 *
 * Description:
 *   Set controller saturation limits. Sometimes we need change saturation
 *   configuration in the run-time, so this function is separate from
 *   pid_controller_init().
 *
 * Input Parameters:
 *   pid - (out) pointer to the PID controller data
 *   min - (in) lower limit
 *   max - (in) upper limit
 *
 * Returned Value:
 *   None
 *
 ****************************************************************************/

void pid_saturation_set(FAR pid_controller_t* pid, float min, float max)
{
  pid->sat.max = max;
  pid->sat.min = min;
}

/****************************************************************************
 * Name: pi_saturation_set
 *
 * Description:
 *
 * Input Parameters:
 *   pid - (out) pointer to the PID controller data
 *   min - (in) lower limit
 *   max - (in) upper limit
 *
 * Returned Value:
 *   None
 *
 ****************************************************************************/

void pi_saturation_set(FAR pid_controller_t* pid, float min, float max)
{
  pid_saturation_set(pid, min, max);
}

/****************************************************************************
 * Name: pi_controller
 *
 * Description:
 *   PI controller with output saturation and windup protection
 *
 * Input Parameters:
 *   pid - (in/out) pointer to the PI controller data
 *   err - (in) current controller error
 *
 * Returned Value:
 *   Return controller output.
 *
 ****************************************************************************/

float pi_controller(FAR pid_controller_t *pid, float err)
{
  /* Store error in controller structure */

  pid->err = err;

  /* Get proportional part */

  pid->part[0] = pid->KP * err;

  /* Get intergral part */

  pid->part[1] += pid->KI * err;

  /* Add proportional, integral */

  pid->out = pid->part[0] + pid->part[1];

  /* Saturate output only if not in PID calculation and if some limits are set */

  if (pid->sat.max != pid->sat.min && pid->KD == 0.0)
    {
      if (pid->out > pid->sat.max)
        {
          /* Limit output to the upper limit */

          pid->out = pid->sat.max;

          /* Integral anti-windup - reset integral part */

          if (err > 0)
            {
              pid->part[1] = 0;
            }
        }
      else if (pid->out < pid->sat.min)
        {
          /* Limit output to the lower limit */

          pid->out = pid->sat.min;

          /* Integral anti-windup - reset integral part */

          if (err < 0)
            {
              pid->part[1] = 0;
            }
        }
    }

  /* Return regulator output */

  return pid->out;
}

/****************************************************************************
 * Name: pid_controller
 *
 * Description:
 *   PID controller with output saturation and windup protection
 *
 * Input Parameters:
 *   pid - (in/out) pointer to the PID controller data
 *   err - (in) current controller error
 *
 * Returned Value:
 *   Return controller output.
 *
 ****************************************************************************/

float pid_controller(FAR pid_controller_t *pid, float err)
{
  /* Get PI output */

  pi_controller(pid, err);

  /* Get derivative part */

  pid->part[2] = pid->KD * (err - pid->err_prev);

  /* Add derivative part to the PI part */

  pid->out +=  pid->part[2];

  /* Store current error */

  pid->err_prev = err;

  /* Saturate output if limits are set */

  if (pid->sat.max != pid->sat.min)
    {
      if (pid->out > pid->sat.max)
        {
          /* Limit output to the upper limit */

          pid->out = pid->sat.max;
        }
      else if (pid->out < pid->sat.min)
        {
          /* Limit output to the lower limit */

          pid->out = pid->sat.min;
        }
    }

  /* Return regulator output */

  return pid->out;
}