ROS Interface start and stop signals on executing commands

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@binitshah we discussed this when we met a couple of weeks ago.

You mentioned that once I issue a move command via the ROS interface, there is a particular ROS topic that starts sending messages, and once the move command finishes executing, it stops sending messages.
Can you provide the details – which topic is it, etc.?

2

Yes, it’s called the /stretch_controller/follow_joint_trajectory/feedback topic and it’s part of the follow_joint_trajectory action server. This topic will publish feedback messages when any of the robot’s joints are in motion.

The follow_joint_trajectory action server is comprised of 5 topics. To command the robot’s joints into motion, the goal topic is used.

$ rostopic list
[...]
/stretch_controller/follow_joint_trajectory/cancel
/stretch_controller/follow_joint_trajectory/feedback
/stretch_controller/follow_joint_trajectory/goal
/stretch_controller/follow_joint_trajectory/result
/stretch_controller/follow_joint_trajectory/status

The follow_joint_trajectory action server is implemented in this file and is part of the stretch_driver node from Stretch Core. Launching the node will give you access to the 5 topics. Here’s the launch command:

roslaunch stretch_core stretch_driver.launch
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