Attention: Answers.ros.org is deprecated as of August the 11th, 2023. Please visit robotics.stackexchange.com to ask a new question. This site will remain online in read-only mode during the transition and into the foreseeable future. Selected questions and answers have been migrated, and redirects have been put in place to direct users to the corresponding questions on Robotics Stack Exchange. Additional details are available here.

why need a dummy trajectory in joint_trajectory_action_controller.cpp

asked 2013-06-03 08:37:39 -0600

AdrianPeng
441 ●50 ●57 ●66

updated 2013-11-18 16:55:30 -0600

tfoote

58457 ●128 ●550 ●526 http://www.ros.org/

Hi,

in joint_trajectory_action_controller.cpp (robot_mechanism_controllers package)

// Creates a dummy trajectory
boost::shared_ptr<SpecifiedTrajectory> traj_ptr(new SpecifiedTrajectory(1));
SpecifiedTrajectory &traj = *traj_ptr;
traj[0].start_time = robot_->getTime().toSec();
traj[0].duration = 0.0;
traj[0].splines.resize(joints_.size());
for (size_t j = 0; j < joints_.size(); ++j)
  traj[0].splines[j].coef[0] = 0.0;
current_trajectory_box_.set(traj_ptr);

Why need to create a dummy trajectory?

Thanks for any help in advance!

edit retag flag offensive close merge delete

add a comment

1 Answer

Sort by » oldest newest most voted

answered 2013-06-03 21:23:32 -0600

Adolfo Rodriguez T

3907 ●28 ●45 ●71

This is a hold position trajectory: A single-waypoint at the current time set to maintain the current joint positions.

When the JointTrajectoryActionController starts, it defaults to holding the current position while it awaits for the first command to arrive.

Note: The code snippet you reference is from the init() method. Something similar also happens in starting(), so it seems that the snippet in init() is unnecessary and IMO could be removed.

Since you are asking many questions about this controller, are you planning on reimplementing it for a custom non-PR2 robot, or are you simply studying its internals?. FYI, a robot-agnostic implementation of this controller should land in the ros_control project sometime in the next 3 months.

edit flag offensive delete link

Comments

Right now, I am just studying its internals. I might write other package to interface with it later.

AdrianPeng ( 2013-06-04 07:53:55 -0600 )edit

add a comment

Question Tools

Stats

Asked: 2013-06-03 08:37:39 -0600

Seen: 1,198 times

Last updated: Jun 03 '13

why need a dummy trajectory in joint_trajectory_action_controller.cpp edit

1 Answer

Comments

Question Tools

Stats

Related questions

why need a dummy trajectory in joint_trajectory_action_controller.cpp