Add custom window size and poly order for SG filter (#5489)

* Add custom window size and poly order in SG filter

Signed-off-by: mini-1235 <[email protected]>

* Fix linting and benchmark tool

Signed-off-by: mini-1235 <[email protected]>

* Cmakelist

Signed-off-by: mini-1235 <[email protected]>

* Adding comments

Signed-off-by: mini-1235 <[email protected]>

* Add blog

Signed-off-by: mini-1235 <[email protected]>

---------

Signed-off-by: mini-1235 <[email protected]>

Author: mini-1235

nav2_smoother/CMakeLists.txt

@@ -16,6 +16,7 @@ find_package(rclcpp_lifecycle REQUIRED)
 find_package(tf2 REQUIRED)
 find_package(tf2_ros REQUIRED)
 find_package(nav2_ros_common REQUIRED)
+find_package(Eigen3 REQUIRED)
 
 nav2_package()
 
@@ -42,6 +43,7 @@ target_link_libraries(${library_name} PUBLIC
   rclcpp_lifecycle::rclcpp_lifecycle
   tf2_ros::tf2_ros
   nav2_ros_common::nav2_ros_common
+  Eigen3::Eigen
 )
 target_link_libraries(${library_name} PRIVATE
   rclcpp_components::component
@@ -157,6 +159,7 @@ ament_export_dependencies(
   rclcpp_lifecycle
   tf2
   tf2_ros
+  Eigen3
 )
 ament_export_targets(${library_name})
 ament_package()

nav2_smoother/include/nav2_smoother/savitzky_golay_smoother.hpp

@@ -15,6 +15,7 @@
 #ifndef NAV2_SMOOTHER__SAVITZKY_GOLAY_SMOOTHER_HPP_
 #define NAV2_SMOOTHER__SAVITZKY_GOLAY_SMOOTHER_HPP_
 
+#include <Eigen/Dense>
 #include <cmath>
 #include <vector>
 #include <string>
@@ -85,6 +86,11 @@ class SavitzkyGolaySmoother : public nav2_core::Smoother
     nav_msgs::msg::Path & path,
     const rclcpp::Duration & max_time) override;
 
+  /**
+   * @brief Method to calculate SavitzkyGolay Coefficients
+   */
+  void calculateCoefficients();
+
 protected:
   /**
    * @brief Smoother method - does the smoothing on a segment
@@ -99,7 +105,8 @@ class SavitzkyGolaySmoother : public nav2_core::Smoother
     bool & reversing_segment);
 
   bool do_refinement_, enforce_path_inversion_;
-  int refinement_num_;
+  int refinement_num_, window_size_, half_window_size_, poly_order_;
+  Eigen::VectorXd sg_coeffs_;
   rclcpp::Logger logger_{rclcpp::get_logger("SGSmoother")};
 };
 

nav2_smoother/package.xml

@@ -24,6 +24,8 @@
   <depend>tf2</depend>
   <depend>tf2_ros</depend>
   <depend>nav2_ros_common</depend>
+  <depend>eigen3_cmake_module</depend>
+  <depend>eigen</depend>
 
   <test_depend>ament_cmake_gtest</test_depend>
   <test_depend>ament_index_cpp</test_depend>

nav2_smoother/src/savitzky_golay_smoother.cpp

@@ -40,9 +40,39 @@ void SavitzkyGolaySmoother::configure(
     node, name + ".refinement_num", rclcpp::ParameterValue(2));
   declare_parameter_if_not_declared(
     node, name + ".enforce_path_inversion", rclcpp::ParameterValue(true));
+  declare_parameter_if_not_declared(
+    node, name + ".window_size", rclcpp::ParameterValue(7));
+  declare_parameter_if_not_declared(
+    node, name + ".poly_order", rclcpp::ParameterValue(3));
   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_);
+  node->get_parameter(name + ".window_size", window_size_);
+  node->get_parameter(name + ".poly_order", poly_order_);
+  if (window_size_ % 2 == 0 || window_size_ <= 2) {
+    throw nav2_core::SmootherException(
+      "Savitzky-Golay Smoother requires an odd window size of 3 or greater");
+  }
+  half_window_size_ = (window_size_ - 1) / 2;
+  calculateCoefficients();
+}
+
+// For more details on calculating Savitzky–Golay filter coefficients,
+// see: https://www.colmryan.org/posts/savitsky_golay/
+void SavitzkyGolaySmoother::calculateCoefficients()
+{
+  // We construct the Vandermonde matrix here
+  Eigen::VectorXd v = Eigen::VectorXd::LinSpaced(window_size_, -half_window_size_,
+      half_window_size_);
+  Eigen::MatrixXd x = Eigen::MatrixXd::Ones(window_size_, poly_order_ + 1);
+  for(int i = 1; i <= poly_order_; i++) {
+    x.col(i) = (x.col(i - 1).array() * v.array()).matrix();
+  }
+  // Compute the pseudoinverse of X, (X^T * X)^-1 * X^T
+  Eigen::MatrixXd coeff_mat = (x.transpose() * x).inverse() * x.transpose();
+
+  // Extract the smoothing coefficients
+  sg_coeffs_ = coeff_mat.row(0).transpose();
 }
 
 bool SavitzkyGolaySmoother::smooth(
@@ -62,8 +92,10 @@ bool SavitzkyGolaySmoother::smooth(
     path_segments = findDirectionalPathSegments(path);
   }
 
+  // Minimum point size to smooth is SG filter size + start + end
+  unsigned int minimum_points = window_size_ + 2;
   for (unsigned int i = 0; i != path_segments.size(); i++) {
-    if (path_segments[i].end - path_segments[i].start > 9) {
+    if (path_segments[i].end - path_segments[i].start > minimum_points) {
       // Populate path segment
       curr_path_segment.poses.clear();
       std::copy(
@@ -100,68 +132,41 @@ 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;
+  // Convert PoseStamped to Eigen
+  auto toEigenVec = [](const geometry_msgs::msg::PoseStamped & pose) -> Eigen::Vector2d {
+      return {pose.pose.position.x, pose.pose.position.y};
     };
 
   auto applyFilterOverAxes =
     [&](std::vector<geometry_msgs::msg::PoseStamped> & plan_pts,
-    const std::vector<geometry_msgs::msg::PoseStamped> & init_plan_pts) -> void
+    const std::vector<Eigen::Vector2d> & 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;
+        Eigen::Vector2d accum(0.0, 0.0);
+
+        for(int j = -half_window_size_; j <= half_window_size_; j++) {
+          int path_idx = std::clamp<int>(idx + j, 0, path_size - 1);
+          accum += sg_coeffs_(j + half_window_size_) * init_plan_pts[path_idx];
         }
+        plan_pts[idx].pose.position.x = accum.x();
+        plan_pts[idx].pose.position.y = accum.y();
       }
     };
 
-  const auto initial_path_poses = path.poses;
+  std::vector<Eigen::Vector2d> initial_path_poses(path.poses.size());
+  std::transform(path.poses.begin(), path.poses.end(),
+               initial_path_poses.begin(), toEigenVec);
   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;
+      std::vector<Eigen::Vector2d> reined_initial_path_poses(path.poses.size());
+      std::transform(path.poses.begin(), path.poses.end(),
+                       reined_initial_path_poses.begin(), toEigenVec);
       applyFilterOverAxes(path.poses, reined_initial_path_poses);
     }
   }

tools/smoother_benchmarking/smoother_benchmark_bringup.py

@@ -19,6 +19,7 @@
 from launch.actions import ExecuteProcess, IncludeLaunchDescription
 from launch.launch_description_sources import PythonLaunchDescriptionSource
 from launch_ros.actions import Node
+from nav2_common.launch import RewrittenYaml
 
 
 def generate_launch_description() -> LaunchDescription:
@@ -30,6 +31,14 @@ def generate_launch_description() -> LaunchDescription:
     )
     map_file = os.path.join(benchmark_dir, 'maps', 'smoothers_world.yaml')
     lifecycle_nodes = ['map_server', 'planner_server', 'smoother_server']
+    config = RewrittenYaml(
+        source_file=config, root_key='', param_rewrites={},
+        value_rewrites={
+            'KEEPOUT_ZONE_ENABLED': 'False',
+            'SPEED_ZONE_ENABLED': 'False',
+        },
+        convert_types=True
+    )
 
     static_transform_one = Node(
         package='tf2_ros',