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, const std::vector< bool > &joints_angle_wraparound=std::vector< bool >())
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, const interpolation_methods::InterpolationMethod interpolation_method, trajectory_msgs::msg::JointTrajectoryPoint &output_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 bool	has_nontrivial_msg () const
JOINT_TRAJECTORY_CONTROLLER_PUBLIC std::shared_ptr< trajectory_msgs::msg::JointTrajectory >	get_trajectory_msg () 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,
		const interpolation_methods::InterpolationMethod	interpolation_method,
		trajectory_msgs::msg::JointTrajectoryPoint &	output_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. Sampling trajectory at given sample_time. If position in the end_segment_itr is missing it will be deduced from provided velocity, or acceleration respectively. Deduction assumes that the provided velocity or acceleration have to be reached at the time defined in the segment.

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

Parameters

[in]	sample_time	Time at which trajectory will be sampled.
[in]	interpolation_method	Specify whether splines, another method, or no interpolation at all.
[out]	expected_state	Calculated new at sample_time.
[out]	start_segment_itr	Iterator to the start segment for given sample_time. See description above.
[out]	end_segment_itr	Iterator to the end segment for given sample_time. See description above.

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,
		const std::vector< bool > &	joints_angle_wraparound = std::vector<bool>()
	)

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

Parameters

joints_angle_wraparound

Vector of boolean where true value corresponds to a joint that wrap around (ie. is continuous).

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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