lattapolw ros-track

[ntwong0]

Agenda 10/8

• [ ] experimentation with actionlib

Agenda 10/1

• [x] updating progress on Github
  • [x] how to use markdown
  • [x] how to use Github issues
• [x] actionlib

Agenda 9/24

• [x] how to git
  • (great resource covering much more about git)

Work on navgoal publisher

• [x] load sim world and sim rover, then navigate it with rviz
• [x] publish latlong navgoal as map Cartesian coordinates
• [x] load latlong csv as array
• [x] subscribe to rover odom
• [x] track rover distance to navgoal
• [x] update current navgoal based on rover distance to navgoal
• [ ] Incorporate actionlib
  • [x] move_base_msgs client to issue PoseStamped target_poses to the move_base server
  • [ ] choose different behavior based on state from the move_base server
  • [ ] an actionlib server that accepts lat-long requests and converts them to PoseStamped target_poses
  • [ ] an actionlib client that issues lat-long requests

[ntwong0]

@lattapolw

I wanted to follow up RE: the world.launch file's issue with loading the simulation world. Before roslaunching, cd to the gazebo/ directory, and run

export GAZEBO_RESOURCE_PATH=$(pwd)

Regarding the state estimation node /ekf_localization, the localization.yaml configuration file for the node, the parameters set to true does indeed indicate that the parameter is intended for the Kalman filter's sensor fusion.

The /husky_velocity_controller/odom topic comes from a node of type diff_drive_controller/DiffDriveController, which also publishes the /cmd_vel twist commands. The odometry of this topic are the velocities translated from the twist command, and the fused parameters correspond to the linear x, y, z velocities and angular yaw velocity.

The /imu/data's fused parameters correspond to the angular x, y, z orientations (i.e. compass sensing) and angular x, y, z velocities (i.e. gyroscope sensing).

For a more in depth exploration of robot_localization this video by the package author is a great resource.

Sorry I didn't get in depth with this earlier, I hope this reflection helps.

[lattapolw]

@ntwong0

Thank you for the follow up! I was trying to pass the world.world argument into the world_name in empty_world.launch, but it wasn't working. I think it is able to find the world.world file now, but I ran into new errors saying "Unable to find uri" which I'm not sure what it is. Do you know how to fix this?

[ntwong0]

@lattapolw interesting - this means that the underlying models can't be found.

If you use the the echo $GAZEBO_RESOURCE_PATH command, what do you see?

Also, where are your gazebo/ and capstone_resources/ directories located?

[lattapolw]

@ntwong0

When I use echo command, it returns back /home/ubuntu/catkin_ws/capstone/ros-curriculum/capstone_resources/gazebo. This is only after I already ran the export GAZEBO_RESOURCE_PATH=$(pwd), or else it doesn't show anything.

My gazebo/ directory is the same as the one returned in echo command and the capstone_resources/ is the one above gazebo/.

[ntwong0]

@lattapolw

The export command modifies the environment variables for the terminal window in which it is used. So long as you then run gazebo

(either with rosrun gazebo_ros gazebo world.world or roslaunch ../launch/world.launch)

from that same terminal window/tab, it should be able to load up the resources from gazebo/

---

However, if the terminal window/tab that ran export is DIFFERENT from the one that runs gazebo, then this problem would arise.

I noticed from your screenshot that you have multiple terminals running, so I was wondering if this is the case.

[ntwong0]

Reposting references from our convo for future reference:

• http://docs.ros.org/melodic/api/std_msgs/html/msg/Header.html
• http://wiki.ros.org/rospy/Overview/Time#Sleeping_and_Rates
• https://effbot.org/zone/stupid-exceptions-keyboardinterrupt.htm
• http://wiki.ros.org/rospy/Overview/Initialization%20and%20Shutdown
• http://wiki.ros.org/actionlib

[ntwong0]

Good meeting! Great progress on the move_base client; here's some links to the documentation we went over today:

• Writing a simple action server
• Writing a simple action client
• Sending simple goals to move_base
• Documentation for move_base_msgs

I've updated the todos list for this issue to reflect what you accomplished and what's ahead

For next week:

• Play with client.get_state() and issue different behaviors
• Take a look at how to thread the actionlib client via this tutorial

[ntwong0]

Thanks for today!

I'll share the following with you next week:

• Hands-on tutorial: threaded simple action client example
• Introduce a way to restart and resume more efficiently