time_optimal_trajectory_generation.hpp

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/*
 * Copyright (c) 2011-2012, Georgia Tech Research Corporation
 * All rights reserved.
 *
 * Author: Tobias Kunz <tobias@gatech.edu>
 * Date: 05/2012
 *
 * Humanoid Robotics Lab      Georgia Institute of Technology
 * Director: Mike Stilman     http://www.golems.org
 *
 * Algorithm details and publications:
 * http://www.golems.org/node/1570
 *
 * This file is provided under the following "BSD-style" License:
 *   Redistribution and use in source and binary forms, with or
 *   without modification, are permitted provided that the following
 *   conditions are met:
 *   * Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *   * Redistributions in binary form must reproduce the above
 *     copyright notice, this list of conditions and the following
 *     disclaimer in the documentation and/or other materials provided
 *     with the distribution.
 *   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
 *   CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
 *   INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 *   MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 *   DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
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 *   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 *   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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 */
 
#pragma once
 
#include <Eigen/Core>
#include <list>
#include <moveit/robot_trajectory/robot_trajectory.hpp>
#include <moveit/trajectory_processing/time_parameterization.hpp>
 
namespace trajectory_processing
{
 
// The intermediate waypoints of the input path need to be blended so that the entire path is diffentiable.
// This constant defines the maximum deviation allowed at those intermediate waypoints, in radians for revolute joints,
// or meters for prismatic joints.
constexpr double DEFAULT_PATH_TOLERANCE = 0.1;
 
enum LimitType
{
  VELOCITY,
  ACCELERATION
};
 
const std::unordered_map<LimitType, std::string> LIMIT_TYPES = { { VELOCITY, "velocity" },
                                                                 { ACCELERATION, "acceleration" } };
class PathSegment
{
public:
  PathSegment(double length = 0.0) : length_(length)
  {
  }
  virtual ~PathSegment()  // is required for destructing derived classes
  {
  }
  double getLength() const
  {
    return length_;
  }
  virtual Eigen::VectorXd getConfig(double s) const = 0;
  virtual Eigen::VectorXd getTangent(double s) const = 0;
  virtual Eigen::VectorXd getCurvature(double s) const = 0;
  virtual std::list<double> getSwitchingPoints() const = 0;
  virtual PathSegment* clone() const = 0;
 
  double position_;
 
protected:
  double length_;
};
 
class Path
{
public:
  // Create a Path from a vector of waypoints and a maximum deviation to tolerate at the intermediate waypoints.
  // The algorithm needs max_deviation to be greater than zero so that the path is differentiable.
  static std::optional<Path> create(const std::vector<Eigen::VectorXd>& waypoint,
                                    double max_deviation = DEFAULT_PATH_TOLERANCE);
 
  // Copy constructor.
  Path(const Path& path);
 
  double getLength() const;
  Eigen::VectorXd getConfig(double s) const;
  Eigen::VectorXd getTangent(double s) const;
  Eigen::VectorXd getCurvature(double s) const;
 
  double getNextSwitchingPoint(double s, bool& discontinuity) const;
 
  std::list<std::pair<double, bool>> getSwitchingPoints() const;
 
private:
  // Default constructor private to prevent misuse. Use `create` instead to create a Path object.
  Path() = default;
 
  PathSegment* getPathSegment(double& s) const;
 
  double length_ = 0.0;
  std::list<std::pair<double, bool>> switching_points_;
  std::list<std::unique_ptr<PathSegment>> path_segments_;
};
 
class Trajectory
{
public:
  static std::optional<Trajectory> create(const Path& path, const Eigen::VectorXd& max_velocity,
                                          const Eigen::VectorXd& max_acceleration, double time_step = 0.001);
 
  double getDuration() const;
 
  Eigen::VectorXd getPosition(double time) const;
  Eigen::VectorXd getVelocity(double time) const;
  Eigen::VectorXd getAcceleration(double time) const;
 
private:
  Trajectory(const Path& path, const Eigen::VectorXd& max_velocity, const Eigen::VectorXd& max_acceleration,
             double time_step);
 
  struct TrajectoryStep
  {
    TrajectoryStep()
    {
    }
    TrajectoryStep(double path_pos, double path_vel) : path_pos_(path_pos), path_vel_(path_vel)
    {
    }
    double path_pos_;
    double path_vel_;
    double time_;
  };
 
  bool getNextSwitchingPoint(double path_pos, TrajectoryStep& next_switching_point, double& before_acceleration,
                             double& after_acceleration) const;
  bool getNextAccelerationSwitchingPoint(double path_pos, TrajectoryStep& next_switching_point,
                                         double& before_acceleration, double& after_acceleration) const;
  bool getNextVelocitySwitchingPoint(double path_pos, TrajectoryStep& next_switching_point, double& before_acceleration,
                                     double& after_acceleration) const;
  bool integrateForward(std::list<TrajectoryStep>& trajectory, double acceleration);
  void integrateBackward(std::list<TrajectoryStep>& start_trajectory, double path_pos, double path_vel,
                         double acceleration);
  double getMinMaxPathAcceleration(double path_position, double path_velocity, bool max) const;
  double getMinMaxPhaseSlope(double path_position, double path_velocity, bool max) const;
  double getAccelerationMaxPathVelocity(double path_pos) const;
  double getVelocityMaxPathVelocity(double path_pos) const;
  double getAccelerationMaxPathVelocityDeriv(double path_pos) const;
  double getVelocityMaxPathVelocityDeriv(double path_pos) const;
 
  std::list<TrajectoryStep>::const_iterator getTrajectorySegment(double time) const;
 
  Path path_;
  Eigen::VectorXd max_velocity_;
  Eigen::VectorXd max_acceleration_;
  unsigned int joint_num_ = 0.0;
  bool valid_ = true;
  std::list<TrajectoryStep> trajectory_;
  std::list<TrajectoryStep> end_trajectory_;  // non-empty only if the trajectory generation failed.
 
  double time_step_ = 0.0;
 
  mutable double cached_time_ = std::numeric_limits<double>::max();
  mutable std::list<TrajectoryStep>::const_iterator cached_trajectory_segment_;
};
 
MOVEIT_CLASS_FORWARD(TimeOptimalTrajectoryGeneration);
class TimeOptimalTrajectoryGeneration : public TimeParameterization
{
public:
  TimeOptimalTrajectoryGeneration(const double path_tolerance = DEFAULT_PATH_TOLERANCE, const double resample_dt = 0.1,
                                  const double min_angle_change = 0.001);
 
  // clang-format off
  // clang-format on
  bool computeTimeStamps(robot_trajectory::RobotTrajectory& trajectory, const double max_velocity_scaling_factor = 1.0,
                         const double max_acceleration_scaling_factor = 1.0) const override;
 
  // clang-format off
  // clang-format on
  bool computeTimeStamps(robot_trajectory::RobotTrajectory& trajectory,
                         const std::unordered_map<std::string, double>& velocity_limits,
                         const std::unordered_map<std::string, double>& acceleration_limits,
                         const double max_velocity_scaling_factor = 1.0,
                         const double max_acceleration_scaling_factor = 1.0) const override;
 
  // clang-format off
  // clang-format on
  bool computeTimeStamps(robot_trajectory::RobotTrajectory& trajectory,
                         const std::vector<moveit_msgs::msg::JointLimits>& joint_limits,
                         const double max_velocity_scaling_factor = 1.0,
                         const double max_acceleration_scaling_factor = 1.0) const override;
 
private:
  bool doTimeParameterizationCalculations(robot_trajectory::RobotTrajectory& trajectory,
                                          const Eigen::VectorXd& max_velocity,
                                          const Eigen::VectorXd& max_acceleration) const;
 
  bool hasMixedJointTypes(const moveit::core::JointModelGroup* group) const;
 
  double verifyScalingFactor(const double requested_scaling_factor, const LimitType limit_type) const;
 
  const double path_tolerance_;
  const double resample_dt_;
  const double min_angle_change_;
};
 
// clang-format off
// clang-format on
bool totgComputeTimeStamps(const size_t num_waypoints, robot_trajectory::RobotTrajectory& trajectory,
                           const double max_velocity_scaling_factor = 1.0,
                           const double max_acceleration_scaling_factor = 1.0);
}  // namespace trajectory_processing