joint_trajectory_controller::Trajectory Class Reference

Public Member Functions
JOINT_TRAJECTORY_CONTROLLER_PUBLIC	Trajectory (std::shared_ptr< trajectory_msgs::msg::JointTrajectory > joint_trajectory)
JOINT_TRAJECTORY_CONTROLLER_PUBLIC	Trajectory (const rclcpp::Time &current_time, const trajectory_msgs::msg::JointTrajectoryPoint &current_point, std::shared_ptr< trajectory_msgs::msg::JointTrajectory > joint_trajectory)
JOINT_TRAJECTORY_CONTROLLER_PUBLIC void	set_point_before_trajectory_msg (const rclcpp::Time &current_time, const trajectory_msgs::msg::JointTrajectoryPoint &current_point)
JOINT_TRAJECTORY_CONTROLLER_PUBLIC void	update (std::shared_ptr< trajectory_msgs::msg::JointTrajectory > joint_trajectory)
JOINT_TRAJECTORY_CONTROLLER_PUBLIC bool	sample (const rclcpp::Time &sample_time, trajectory_msgs::msg::JointTrajectoryPoint &expected_state, TrajectoryPointConstIter &start_segment_itr, TrajectoryPointConstIter &end_segment_itr)
JOINT_TRAJECTORY_CONTROLLER_PUBLIC void	interpolate_between_points (const rclcpp::Time &time_a, const trajectory_msgs::msg::JointTrajectoryPoint &state_a, const rclcpp::Time &time_b, const trajectory_msgs::msg::JointTrajectoryPoint &state_b, const rclcpp::Time &sample_time, trajectory_msgs::msg::JointTrajectoryPoint &output)
JOINT_TRAJECTORY_CONTROLLER_PUBLIC TrajectoryPointConstIter	begin () const
JOINT_TRAJECTORY_CONTROLLER_PUBLIC TrajectoryPointConstIter	end () const
JOINT_TRAJECTORY_CONTROLLER_PUBLIC rclcpp::Time	time_from_start () const
JOINT_TRAJECTORY_CONTROLLER_PUBLIC bool	has_trajectory_msg () const
JOINT_TRAJECTORY_CONTROLLER_PUBLIC std::shared_ptr< trajectory_msgs::msg::JointTrajectory >	get_trajectory_msg () const
JOINT_TRAJECTORY_CONTROLLER_PUBLIC rclcpp::Time	get_trajectory_start_time () const
JOINT_TRAJECTORY_CONTROLLER_PUBLIC bool	is_sampled_already () const

Member Function Documentation

interpolate_between_points()

void joint_trajectory_controller::Trajectory::interpolate_between_points	(	const rclcpp::Time &	time_a,
		const trajectory_msgs::msg::JointTrajectoryPoint &	state_a,
		const rclcpp::Time &	time_b,
		const trajectory_msgs::msg::JointTrajectoryPoint &	state_b,
		const rclcpp::Time &	sample_time,
		trajectory_msgs::msg::JointTrajectoryPoint &	output
	)

Do interpolation between 2 states given a time in between their respective timestamps

The start and end states need not necessarily be specified all the way to the acceleration level:

• If only positions are specified, linear interpolation will be used.
• If positions and velocities are specified, a cubic spline will be used.
• If positions, velocities and accelerations are specified, a quintic spline will be used.

If start and end states have different specifications (eg. start is position-only, end is position-velocity), the lowest common specification will be used (position-only in the example).

Parameters

[in]	time_a	Time at which the segment state equals state_a.
[in]	state_a	State at time_a.
[in]	time_b	Time at which the segment state equals state_b.
[in]	state_b	State at time time_b.
[in]	sample_time	The time to sample, between time_a and time_b.
[out]	output	The state at sample_time.

sample()

bool joint_trajectory_controller::Trajectory::sample	(	const rclcpp::Time &	sample_time,
		trajectory_msgs::msg::JointTrajectoryPoint &	expected_state,
		TrajectoryPointConstIter &	start_segment_itr,
		TrajectoryPointConstIter &	end_segment_itr
	)

Find the segment (made up of 2 points) and its expected state from the containing trajectory. Specific case returns for start_segment_itr and end_segment_itr:

• Sampling before the trajectory start: start_segment_itr = begin(), end_segment_itr = begin()
• Sampling exactly on a point of the trajectory: start_segment_itr = iterator where point is, end_segment_itr = iterator after start_segment_itr
• Sampling between points: start_segment_itr = iterator before the sampled point, end_segment_itr = iterator after start_segment_itr
• Sampling after entire trajectory: start_segment_itr = –end(), end_segment_itr = end()
• Sampling empty msg or before the time given in set_point_before_trajectory_msg() return false

set_point_before_trajectory_msg()

void joint_trajectory_controller::Trajectory::set_point_before_trajectory_msg	(	const rclcpp::Time &	current_time,
		const trajectory_msgs::msg::JointTrajectoryPoint &	current_point
	)

Set the point before the trajectory message is replaced/appended Example: if we receive a new trajectory message and it's first point is 0.5 seconds from the current one, we call this function to log the current state, then append/replace the current trajectory

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The documentation for this class was generated from the following files:

• ros2_controllers/joint_trajectory_controller/include/joint_trajectory_controller/trajectory.hpp
• ros2_controllers/joint_trajectory_controller/src/trajectory.cpp