standard_traj_generator.cpp

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#include <dwb_plugins/standard_traj_generator.h>
#include <dwb_plugins/xy_theta_iterator.h>
#include <nav_2d_utils/parameters.h>
#include <pluginlib/class_list_macros.h>
#include <nav_core2/exceptions.h>
#include <algorithm>
#include <memory>
#include <string>
#include <vector>
 
using nav_2d_utils::loadParameterWithDeprecation;
 
namespace dwb_plugins
{
 
void StandardTrajectoryGenerator::initialize(ros::NodeHandle& nh)
{
  kinematics_ = std::make_shared<KinematicParameters>();
  kinematics_->initialize(nh);
  initializeIterator(nh);
 
  nh.param("sim_time", sim_time_, 1.7);
  checkUseDwaParam(nh);
 
  nh.param("include_last_point", include_last_point_, true);
 
  /*
   * If discretize_by_time, then sim_granularity represents the amount of time that should be between
   *  two successive points on the trajectory.
   *
   * If discretize_by_time is false, then sim_granularity is the maximum amount of distance between
   *  two successive points on the trajectory, and angular_sim_granularity is the maximum amount of
   *  angular distance between two successive points.
   */
  nh.param("discretize_by_time", discretize_by_time_, false);
  if (discretize_by_time_)
  {
    time_granularity_ = loadParameterWithDeprecation(nh, "time_granularity", "sim_granularity", 0.025);
  }
  else
  {
    linear_granularity_ = loadParameterWithDeprecation(nh, "linear_granularity", "sim_granularity", 0.025);
    angular_granularity_ = loadParameterWithDeprecation(nh, "angular_granularity", "angular_sim_granularity", 0.1);
  }
}
 
void StandardTrajectoryGenerator::initializeIterator(ros::NodeHandle& nh)
{
  velocity_iterator_ = std::make_shared<XYThetaIterator>();
  velocity_iterator_->initialize(nh, kinematics_);
}
 
void StandardTrajectoryGenerator::checkUseDwaParam(const ros::NodeHandle& nh)
{
  bool use_dwa;
  nh.param("use_dwa", use_dwa, false);
  if (use_dwa)
  {
    throw nav_core2::PlannerException("Deprecated parameter use_dwa set to true. "
                                      "Please use LimitedAccelGenerator for that functionality.");
  }
}
 
void StandardTrajectoryGenerator::startNewIteration(const nav_2d_msgs::Twist2D& current_velocity)
{
  velocity_iterator_->startNewIteration(current_velocity, sim_time_);
}
 
bool StandardTrajectoryGenerator::hasMoreTwists()
{
  return velocity_iterator_->hasMoreTwists();
}
 
nav_2d_msgs::Twist2D StandardTrajectoryGenerator::nextTwist()
{
  return velocity_iterator_->nextTwist();
}
 
std::vector<double> StandardTrajectoryGenerator::getTimeSteps(const nav_2d_msgs::Twist2D& cmd_vel)
{
  std::vector<double> steps;
  if (discretize_by_time_)
  {
    steps.resize(ceil(sim_time_ / time_granularity_));
  }
  else  // discretize by distance
  {
    double vmag = hypot(cmd_vel.x, cmd_vel.y);
 
    // the distance the robot would travel in sim_time if it did not change velocity
    double projected_linear_distance = vmag * sim_time_;
 
    // the angle the robot would rotate in sim_time
    double projected_angular_distance = fabs(cmd_vel.theta) * sim_time_;
 
    // Pick the maximum of the two
    int num_steps = ceil(std::max(projected_linear_distance / linear_granularity_,
                                  projected_angular_distance / angular_granularity_));
    steps.resize(num_steps);
  }
  if (steps.size() == 0)
  {
    steps.resize(1);
  }
  std::fill(steps.begin(), steps.end(), sim_time_ / steps.size());
  return steps;
}
 
dwb_msgs::Trajectory2D StandardTrajectoryGenerator::generateTrajectory(const geometry_msgs::Pose2D& start_pose,
    const nav_2d_msgs::Twist2D& start_vel,
    const nav_2d_msgs::Twist2D& cmd_vel)
{
  dwb_msgs::Trajectory2D traj;
  traj.velocity = cmd_vel;
 
  //  simulate the trajectory
  geometry_msgs::Pose2D pose = start_pose;
  nav_2d_msgs::Twist2D vel = start_vel;
  double running_time = 0.0;
  std::vector<double> steps = getTimeSteps(cmd_vel);
  for (double dt : steps)
  {
    traj.poses.push_back(pose);
    traj.time_offsets.push_back(ros::Duration(running_time));
    //  calculate velocities
    vel = computeNewVelocity(cmd_vel, vel, dt);
 
    //  update the position of the robot using the velocities passed in
    pose = computeNewPosition(pose, vel, dt);
    running_time += dt;
  }  //  end for simulation steps
 
  if (include_last_point_)
  {
    traj.poses.push_back(pose);
    traj.time_offsets.push_back(ros::Duration(running_time));
  }
 
  return traj;
}
 
nav_2d_msgs::Twist2D StandardTrajectoryGenerator::computeNewVelocity(const nav_2d_msgs::Twist2D& cmd_vel,
    const nav_2d_msgs::Twist2D& start_vel, const double dt)
{
  nav_2d_msgs::Twist2D new_vel;
  new_vel.x = projectVelocity(start_vel.x, kinematics_->getAccX(), kinematics_->getDecelX(), dt, cmd_vel.x);
  new_vel.y = projectVelocity(start_vel.y, kinematics_->getAccY(), kinematics_->getDecelY(), dt, cmd_vel.y);
  new_vel.theta = projectVelocity(start_vel.theta, kinematics_->getAccTheta(), kinematics_->getDecelTheta(),
                                  dt, cmd_vel.theta);
  return new_vel;
}
 
geometry_msgs::Pose2D StandardTrajectoryGenerator::computeNewPosition(const geometry_msgs::Pose2D start_pose,
                                                                      const nav_2d_msgs::Twist2D& vel, const double dt)
{
  geometry_msgs::Pose2D new_pose;
  new_pose.x = start_pose.x + (vel.x * cos(start_pose.theta) + vel.y * cos(M_PI_2 + start_pose.theta)) * dt;
  new_pose.y = start_pose.y + (vel.x * sin(start_pose.theta) + vel.y * sin(M_PI_2 + start_pose.theta)) * dt;
  new_pose.theta = start_pose.theta + vel.theta * dt;
  return new_pose;
}
 
}  // namespace dwb_plugins
 
PLUGINLIB_EXPORT_CLASS(dwb_plugins::StandardTrajectoryGenerator, dwb_local_planner::TrajectoryGenerator)