ego_polar_coords.hpp

// Copyright (c) 2023 Alberto J. Tudela Roldán
//
// 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.
 
#ifndef NAV2_GRACEFUL_CONTROLLER__EGO_POLAR_COORDS_HPP_
#define NAV2_GRACEFUL_CONTROLLER__EGO_POLAR_COORDS_HPP_
 
#include <math.h>
 
#include "angles/angles.h"
#include "geometry_msgs/msg/pose.hpp"
#include "tf2/utils.h"
#include "tf2/transform_datatypes.h"
#include "tf2_geometry_msgs/tf2_geometry_msgs.hpp"
 
namespace nav2_graceful_controller
{
 
struct EgocentricPolarCoordinates
{
  float r;       // Radial distance between the robot pose and the target pose.
  float phi;     // Orientation of target with respect to the line of sight
                 // from the robot to the target.
  float delta;   // Steering angle of the robot with respect to the line of sight.
 
  EgocentricPolarCoordinates(
    const float & r_in = 0.0,
    const float & phi_in = 0.0,
    const float & delta_in = 0.0)
  : r(r_in), phi(phi_in), delta(delta_in) {}
 
  explicit EgocentricPolarCoordinates(
    const geometry_msgs::msg::Pose & target,
    const geometry_msgs::msg::Pose & current = geometry_msgs::msg::Pose(), bool backward = false)
  {
    // Compute the difference between the target and the current pose
    float dX = target.position.x - current.position.x;
    float dY = target.position.y - current.position.y;
    // Compute the line of sight from the robot to the target
    // Flip it if the robot is moving backwards
    float line_of_sight = backward ? (std::atan2(-dY, dX) + M_PI) : std::atan2(-dY, dX);
    // Compute the ego polar coordinates
    r = sqrt(dX * dX + dY * dY);
    phi = angles::normalize_angle(tf2::getYaw(target.orientation) + line_of_sight);
    delta = angles::normalize_angle(tf2::getYaw(current.orientation) + line_of_sight);
  }
};
 
}  // namespace nav2_graceful_controller
 
#endif  // NAV2_GRACEFUL_CONTROLLER__EGO_POLAR_COORDS_HPP_