pid.cpp

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// Original version: Melonee Wise <mwise@willowgarage.com>

#include "control_toolbox/pid.h"
#include "tinyxml.h"

namespace control_toolbox {

Pid::Pid(double P, double I, double D, double I1, double I2) :
  p_gain_(P), i_gain_(I), d_gain_(D), i_max_(I1), i_min_(I2)
{
  p_error_last_ = 0.0;
  p_error_ = 0.0;
  d_error_ = 0.0;
  i_error_ = 0.0;
  cmd_ = 0.0;
}

Pid::~Pid()
{
}

void Pid::initPid(double P, double I, double D, double I1, double I2)
{
  p_gain_ = P;
  i_gain_ = I;
  d_gain_ = D;
  i_max_ = I1;
  i_min_ = I2;

  reset();
}

void Pid::reset()
{
  p_error_last_ = 0.0;
  p_error_ = 0.0;
  d_error_ = 0.0;
  i_error_ = 0.0;
  cmd_ = 0.0;
}

void Pid::getGains(double &p, double &i, double &d, double &i_max, double &i_min)
{
  p = p_gain_;
  i = i_gain_;
  d = d_gain_;
  i_max = i_max_;
  i_min = i_min_;
}

void Pid::setGains(double P, double I, double D, double I1, double I2)
{
  p_gain_ = P;
  i_gain_ = I;
  d_gain_ = D;
  i_max_ = I1;
  i_min_ = I2;
}

bool Pid::initParam(const std::string& prefix)
{
  ros::NodeHandle node(prefix);

  if (!node.getParam("p", p_gain_)) {
    ROS_ERROR("No p gain specified for pid.  Prefix: %s", prefix.c_str());
    return false;
  }
  node.param("i", i_gain_, 0.0) ;
  node.param("d", d_gain_, 0.0) ;
  node.param("i_clamp", i_max_, 0.0) ;
  i_min_ = -i_max_;

  reset();
  return true;
}

bool Pid::initXml(TiXmlElement *config)
{
  p_gain_ = config->Attribute("p") ? atof(config->Attribute("p")) : 0.0;
  i_gain_ = config->Attribute("i") ? atof(config->Attribute("i")) : 0.0;
  d_gain_ = config->Attribute("d") ? atof(config->Attribute("d")) : 0.0;
  i_max_ = config->Attribute("iClamp") ? atof(config->Attribute("iClamp")) : 0.0;
  i_min_ = -i_max_;

  reset();
  return true;
}

bool Pid::init(const ros::NodeHandle &node)
{
  ros::NodeHandle n(node);
  if (!n.getParam("p", p_gain_)) {
    ROS_ERROR("No p gain specified for pid.  Namespace: %s", n.getNamespace().c_str());
    return false;
  }
  n.param("i", i_gain_, 0.0);
  n.param("d", d_gain_, 0.0);
  n.param("i_clamp", i_max_, 0.0);
  i_min_ = -i_max_;

  reset();
  return true;
}


double Pid::updatePid(double error, ros::Duration dt)
{
  double p_term, d_term, i_term;
  p_error_ = error; //this is pError = pState-pTarget

  if (dt == ros::Duration(0.0) || std::isnan(error) || std::isinf(error))
    return 0.0;

  // Calculate proportional contribution to command
  p_term = p_gain_ * p_error_;

  // Calculate the integral error
  i_error_ = i_error_ + dt.toSec() * p_error_;

  //Calculate integral contribution to command
  i_term = i_gain_ * i_error_;

  // Limit i_term so that the limit is meaningful in the output
  if (i_term > i_max_)
  {
    i_term = i_max_;
    i_error_=i_term/i_gain_;
  }
  else if (i_term < i_min_)
  {
    i_term = i_min_;
    i_error_=i_term/i_gain_;
  }

  // Calculate the derivative error
  if (dt.toSec() != 0)
  {
    d_error_ = (p_error_ - p_error_last_) / dt.toSec();
    p_error_last_ = p_error_;
  }
  // Calculate derivative contribution to command
  d_term = d_gain_ * d_error_;
  cmd_ = -p_term - i_term - d_term;

  return cmd_;
}


double Pid::updatePid(double error, double error_dot, ros::Duration dt)
{
  double p_term, d_term, i_term;
  p_error_ = error; //this is pError = pState-pTarget
  d_error_ = error_dot;

  if (dt == ros::Duration(0.0) || std::isnan(error) || std::isinf(error) || std::isnan(error_dot) || std::isinf(error_dot))
    return 0.0;


  // Calculate proportional contribution to command
  p_term = p_gain_ * p_error_;

  // Calculate the integral error
  i_error_ = i_error_ + dt.toSec() * p_error_;

  //Calculate integral contribution to command
  i_term = i_gain_ * i_error_;

  // Limit i_term so that the limit is meaningful in the output
  if (i_term > i_max_)
  {
    i_term = i_max_;
    i_error_=i_term/i_gain_;
  }
  else if (i_term < i_min_)
  {
    i_term = i_min_;
    i_error_=i_term/i_gain_;
  }

  // Calculate derivative contribution to command
  d_term = d_gain_ * d_error_;
  cmd_ = -p_term - i_term - d_term;

  return cmd_;
}



void Pid::setCurrentCmd(double cmd)
{
  cmd_ = cmd;
}

double Pid::getCurrentCmd()
{
  return cmd_;
}

void Pid::getCurrentPIDErrors(double *pe, double *ie, double *de)
{
  *pe = p_error_;
  *ie = i_error_;
  *de = d_error_;
}

}