[CLOSED] Messages on the /husky/odom topic

#1

Good morning,

I am writing to ask for an advice on how I could get a heading direction (yaw) of the husky robot. I have tried subscribing to the /husky/odom and getting the orientation values. As described in the message type, I am expecting a quaternion which I convert to Euler angles. Then I visualized the values and I am a little bit surprised, in the simulation robot rotates by less than PI/ 2.0, however, plotted odometry values indicate several 2.0 * PI rotations. I am aware of the ROS coordinates system, but there might be a bug in my conversion script. However, I am guessing the there is a misunderstanding on what type of message is being published on that particular topic. Could somebody reassure that it is the quaternion that is being published or is there a misunderstanding and a bug?

Best regards
Gabija Bernotaite

#2

To add to that, covariance values seem to be massive, I think 1000000.0 is not a little bit too much.

#3

Hi Gabija

So the type of the odom message is here http://docs.ros.org/en/noetic/api/nav_msgs/html/msg/Odometry.html and the Orientation is of TwistWithCovariance type that is defined here http://docs.ros.org/en/noetic/api/geometry_msgs/html/msg/TwistWithCovariance.html
which is not a Pose message that you expect (read the message type).

You can see what the message type is by doing

rostopic info /husky/odom

and then it will show you the right message type

Type: nav_msgs/OdometryPublishers:

Subscribers: None

Manos

#4

Thank you for your reply. Yes, I have listed the information of the topic. In ROS message types are layered and I was trying to access the orientation information. As per usual, I would expect orientation information to be stored in the pose variable. Twist represents the velocity vector, are you sure I am supposed to use twist message? I am used to using it for the velocity, acceleration estimation etc., but not the robot’s heading direction?

Best regards
Gabija Bernotaite

#5

Dear Gabija,

Actually, your approach is correct. The data is indeed a quaternion, now if it’s not the correct data, I don’t know. You can check in the code as follows if this is what you expect.
The data is published in $HBP/GazeboRosPackages/src/husky_gazebo_plugins/src/husky_plugin.cpp:

tf::Quaternion qt;
qt.setRPY(0,0,odom_pose_[2]);
odom_.pose.pose.orientation.x = qt.getX();
odom_.pose.pose.orientation.y = qt.getY();
odom_.pose.pose.orientation.z = qt.getZ();
odom_.pose.pose.orientation.w = qt.getW();

Best
Axel

#6

Thank you for the reply. Where is odom_pose_[2] coming from? I am suspecting wrong data. Has anyone else tried to extract robot’s heading direction?

#7

Is it from simulated imu?

#8

No it is directly from gazebo.