savitzky_golay_smoother.cpp

// Copyright (c) 2022, Samsung Research America
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License. Reserved.
 
#include <vector>
#include <memory>
#include "nav2_smoother/savitzky_golay_smoother.hpp"
#include "nav2_core/smoother_exceptions.hpp"
 
namespace nav2_smoother
{
 
using namespace smoother_utils;  // NOLINT
using namespace nav2_util::geometry_utils;  // NOLINT
using namespace std::chrono;  // NOLINT
using nav2_util::declare_parameter_if_not_declared;
 
void SavitzkyGolaySmoother::configure(
  const rclcpp_lifecycle::LifecycleNode::WeakPtr & parent,
  std::string name, std::shared_ptr<tf2_ros::Buffer>/*tf*/,
  std::shared_ptr<nav2_costmap_2d::CostmapSubscriber>/*costmap_sub*/,
  std::shared_ptr<nav2_costmap_2d::FootprintSubscriber>/*footprint_sub*/)
{
  auto node = parent.lock();
  logger_ = node->get_logger();
 
  declare_parameter_if_not_declared(
    node, name + ".do_refinement", rclcpp::ParameterValue(true));
  declare_parameter_if_not_declared(
    node, name + ".refinement_num", rclcpp::ParameterValue(2));
  declare_parameter_if_not_declared(
    node, name + ".enforce_path_inversion", rclcpp::ParameterValue(true));
  node->get_parameter(name + ".do_refinement", do_refinement_);
  node->get_parameter(name + ".refinement_num", refinement_num_);
  node->get_parameter(name + ".enforce_path_inversion", enforce_path_inversion_);
}
 
bool SavitzkyGolaySmoother::smooth(
  nav_msgs::msg::Path & path,
  const rclcpp::Duration & max_time)
{
  steady_clock::time_point start = steady_clock::now();
  double time_remaining = max_time.seconds();
 
  bool success = true, reversing_segment;
  nav_msgs::msg::Path curr_path_segment;
  curr_path_segment.header = path.header;
 
  std::vector<PathSegment> path_segments{
    PathSegment{0u, static_cast<unsigned int>(path.poses.size() - 1)}};
  if (enforce_path_inversion_) {
    path_segments = findDirectionalPathSegments(path);
  }
 
  for (unsigned int i = 0; i != path_segments.size(); i++) {
    if (path_segments[i].end - path_segments[i].start > 9) {
      // Populate path segment
      curr_path_segment.poses.clear();
      std::copy(
        path.poses.begin() + path_segments[i].start,
        path.poses.begin() + path_segments[i].end + 1,
        std::back_inserter(curr_path_segment.poses));
 
      // Make sure we're still able to smooth with time remaining
      steady_clock::time_point now = steady_clock::now();
      time_remaining = max_time.seconds() - duration_cast<duration<double>>(now - start).count();
 
      if (time_remaining <= 0.0) {
        RCLCPP_WARN(
          logger_,
          "Smoothing time exceeded allowed duration of %0.2f.", max_time.seconds());
        throw nav2_core::SmootherTimedOut("Smoothing time exceed allowed duration");
      }
 
      // Smooth path segment
      success = success && smoothImpl(curr_path_segment, reversing_segment);
 
      // Assemble the path changes to the main path
      std::copy(
        curr_path_segment.poses.begin(),
        curr_path_segment.poses.end(),
        path.poses.begin() + path_segments[i].start);
    }
  }
 
  return success;
}
 
bool SavitzkyGolaySmoother::smoothImpl(
  nav_msgs::msg::Path & path,
  bool & reversing_segment)
{
  // Must be at least 10 in length to enter function
  const unsigned int & path_size = path.poses.size();
 
  // 7-point SG filter
  const std::array<double, 7> filter = {
    -2.0 / 21.0,
    3.0 / 21.0,
    6.0 / 21.0,
    7.0 / 21.0,
    6.0 / 21.0,
    3.0 / 21.0,
    -2.0 / 21.0};
 
  auto applyFilter = [&](const std::vector<geometry_msgs::msg::Point> & data)
    -> geometry_msgs::msg::Point
    {
      geometry_msgs::msg::Point val;
      for (unsigned int i = 0; i != filter.size(); i++) {
        val.x += filter[i] * data[i].x;
        val.y += filter[i] * data[i].y;
      }
      return val;
    };
 
  auto applyFilterOverAxes =
    [&](std::vector<geometry_msgs::msg::PoseStamped> & plan_pts,
    const std::vector<geometry_msgs::msg::PoseStamped> & init_plan_pts) -> void
    {
      auto pt_m3 = init_plan_pts[0].pose.position;
      auto pt_m2 = init_plan_pts[0].pose.position;
      auto pt_m1 = init_plan_pts[0].pose.position;
      auto pt = init_plan_pts[1].pose.position;
      auto pt_p1 = init_plan_pts[2].pose.position;
      auto pt_p2 = init_plan_pts[3].pose.position;
      auto pt_p3 = init_plan_pts[4].pose.position;
 
      // First point is fixed
      for (unsigned int idx = 1; idx != path_size - 1; idx++) {
        plan_pts[idx].pose.position = applyFilter({pt_m3, pt_m2, pt_m1, pt, pt_p1, pt_p2, pt_p3});
        pt_m3 = pt_m2;
        pt_m2 = pt_m1;
        pt_m1 = pt;
        pt = pt_p1;
        pt_p1 = pt_p2;
        pt_p2 = pt_p3;
 
        if (idx + 4 < path_size - 1) {
          pt_p3 = init_plan_pts[idx + 4].pose.position;
        } else {
          // Return the last point
          pt_p3 = init_plan_pts[path_size - 1].pose.position;
        }
      }
    };
 
  const auto initial_path_poses = path.poses;
  applyFilterOverAxes(path.poses, initial_path_poses);
 
  // Let's do additional refinement, it shouldn't take more than a couple milliseconds
  if (do_refinement_) {
    for (int i = 0; i < refinement_num_; i++) {
      const auto reined_initial_path_poses = path.poses;
      applyFilterOverAxes(path.poses, reined_initial_path_poses);
    }
  }
 
  updateApproximatePathOrientations(path, reversing_segment);
  return true;
}
 
}  // namespace nav2_smoother
 
#include "pluginlib/class_list_macros.hpp"
PLUGINLIB_EXPORT_CLASS(nav2_smoother::SavitzkyGolaySmoother, nav2_core::Smoother)