odometry.cpp

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/*
 * Author: Enrique Fernández
 */

#include <diff_drive_controller/odometry.h>

#include <angles/angles.h>
#include <boost/bind.hpp>

namespace diff_drive_controller
{
  namespace bacc = boost::accumulators;

  Odometry::Odometry(size_t velocity_rolling_window_size)
  : timestamp_(0.0),
    x_(0.0),
    y_(0.0),
    heading_(0.0),
    wheel_separation_(0.0),
    wheel_radius_(0.0),
    left_wheel_old_pos_(0.0),
    right_wheel_old_pos_(0.0),
    linear_acc_(RollingWindow::window_size = velocity_rolling_window_size),
    angular_acc_(RollingWindow::window_size = velocity_rolling_window_size),
    integrate_fun_(boost::bind(&Odometry::integrateExact, this, _1, _2))
  {
  }

  bool Odometry::update(double left_pos, double right_pos, const ros::Time &time)
  {
    const double left_wheel_cur_pos  = left_pos  * wheel_radius_;
    const double right_wheel_cur_pos = right_pos * wheel_radius_;

    const double left_wheel_est_vel  = left_wheel_cur_pos  - left_wheel_old_pos_;
    const double right_wheel_est_vel = right_wheel_cur_pos - right_wheel_old_pos_;

    left_wheel_old_pos_  = left_wheel_cur_pos;
    right_wheel_old_pos_ = right_wheel_cur_pos;

    const double linear  = (right_wheel_est_vel + left_wheel_est_vel) * 0.5 ;
    const double angular = (right_wheel_est_vel - left_wheel_est_vel) / wheel_separation_;

    integrate_fun_(linear, angular);

    const double dt = (time - timestamp_).toSec();
    if(dt < 0.0001)
      return false; // Interval too small to integrate with

    timestamp_ = time;

    linear_acc_(linear/dt);
    angular_acc_(angular/dt);

    return true;
  }

  double Odometry::getLinearEstimated() const
  {
    return bacc::rolling_mean(linear_acc_);
  }

  double Odometry::getAngularEstimated() const
  {
    return bacc::rolling_mean(angular_acc_);
  }

  void Odometry::setWheelParams(double wheel_separation, double wheel_radius)
  {
    wheel_separation_ = wheel_separation;
    wheel_radius_     = wheel_radius;
  }

  void Odometry::integrateRungeKutta2(double linear, double angular)
  {
    double direction = heading_ + angular*0.5;

    x_       += linear * cos(direction);
    y_       += linear * sin(direction);
    heading_ += angular;

    heading_ = angles::normalize_angle(heading_);
  }

  void Odometry::integrateExact(double linear, double angular)
  {
    if(fabs(angular) < 10e-3)
      integrateRungeKutta2(linear, angular);
    else
    {
      const double thetaOld = heading_;
      const double r = linear/angular;
      heading_ += angular;
      x_ +=  r * (sin(heading_) - sin(thetaOld));
      y_ += -r * (cos(heading_) - cos(thetaOld));
    }
  }

} // namespace diff_drive_controller