Update sam_bot_description for the new Gazebo #102

Amronos · 2024-12-10T13:19:08Z

Update DiffDrive plugin for the new Gazebo.
Update IMU for the new Gazebo.
Update to use stamped twist messages for /demo/cmd_vel
Make SDF description
Finish and test sensor description and bridges
Make necessary changes to navigation and test it.

SteveMacenski

First of all, a huge, huge thank you for taking this on, it really helps alot to get some support in updating documentation :-)

sam_bot_description/config/bridge_config.yaml

SteveMacenski · 2024-12-10T23:29:42Z

sam_bot_description/config/bridge_config.yaml

+  ros_type_name: "rosgraph_msgs/msg/Clock"
+  gz_type_name: "gz.msgs.Clock"
+  direction: GZ_TO_ROS
+


Do we need TF as well?

I think the ekf node should publish the transforms instead of Gazebo. I have documented this here.

I guess i haven't typically used EKF when using gazebo, I just let the diff drive plugin provide TF as pretty close to ground truth. I'm open to both ways, but just what I've usually done and makes it a little easier for folks to understand on a tutorial level

Also, it might help in the issues you've mentioned by just removing EKF from the situation 😉

I guess having EKF would be a good idea for a real robot, but not really for Gazebo. I can add the bridge and then maybe make launching EKF an argument of the launch file. Then I can edit the tutorials accordingly.

I guess having EKF would be a good idea for a real robot, but not really for Gazebo. I can add the bridge and then maybe make launching EKF an argument of the launch file. Then I can edit the tutorials accordingly.

Done in 7c1ddc8.

sam_bot_description/src/description/sam_bot_description.sdf

sam_bot_description/src/description/sam_bot_description.urdf

SteveMacenski · 2024-12-17T19:29:26Z

Let me know when you want me to take a look again! I don't want to nitpick mid-update unless you want me to :-)

Amronos · 2024-12-18T12:18:40Z

Let me know when you want me to take a look again! I don't want to nitpick mid-update unless you want me to :-)

Go ahead with it, everything should be good to go.

There is just one problem I have been trying to solve for a while now though:
On running:

ros2 run teleop_twist_keyboard teleop_twist_keyboard --ros-args -p stamped:=true --remap cmd_vel:=/demo/cmd_vel

It does not seem like the robot moves with every command (happens more on publishing a value on angular z) even though on running gz topic -et /demo/cmd_vel I can see the messages are getting received by Gazebo. Also, the odom->base_link transform doesn't appear to be changing in the same way in ROS & Gazebo. This occurs with and without the ekf_node (when not using it I bridge the transforms from Gazebo to ROS).

Update nav2_params.yaml Update to use stamped twist messages Add SDF description Signed-off-by: Aarav Gupta <[email protected]>

Signed-off-by: Aarav Gupta <[email protected]>

Amronos · 2024-12-20T17:05:36Z

There is just one problem I have been trying to solve for a while now though: On running:
ros2 run teleop_twist_keyboard teleop_twist_keyboard --ros-args -p stamped:=true --remap cmd_vel:=/demo/cmd_vel
It does not seem like the robot moves with every command (happens more on publishing a value on angular z) even though on running gz topic -et /demo/cmd_vel I can see the messages are getting received by Gazebo. Also, the odom->base_link transform doesn't appear to be changing in the same way in ROS & Gazebo. This occurs with and without the ekf_node (when not using it I bridge the transforms from Gazebo to ROS).

@SteveMacenski this should be fixed with the latest commit. The only problem is that when the imu topic is included for the ekf_node, the robot rotates more on the z-axis than it should. I am not sure if this is a problem of Gazebo or robot_localization.

sam_bot_description/config/bridge_config.yaml

SteveMacenski · 2024-12-20T23:54:30Z

sam_bot_description/config/bridge_config.yaml

+  ros_type_name: "rosgraph_msgs/msg/Clock"
+  gz_type_name: "gz.msgs.Clock"
+  direction: GZ_TO_ROS
+


I guess i haven't typically used EKF when using gazebo, I just let the diff drive plugin provide TF as pretty close to ground truth. I'm open to both ways, but just what I've usually done and makes it a little easier for folks to understand on a tutorial level

Also, it might help in the issues you've mentioned by just removing EKF from the situation 😉

SteveMacenski

I'm a little unclear as to why there are <gazebo> tags and sensor plugin definitions in the URDF. I think the URDF is just the non-GZ things and the SDF contains the gazebo and sensor plugins that attach to frames defined in the URDF. I think things like the IMU gazebo stuff should be removed to the SDF and only the IMU frame is created / linked in the URDF (and similarly for other sensors, diff drive plugin, joint state publisher, etc).

I don't think there needs to be / should be duplication. I'm not familiar with that much duplication in SDF and URDF

sam_bot_description/launch/display.launch.py

SteveMacenski · 2024-12-20T23:59:43Z

sam_bot_description/launch/display.launch.py

+        DeclareLaunchArgument(name='model', default_value=default_model_path, description='Absolute path to robot urdf file'),
+        DeclareLaunchArgument(name='rvizconfig', default_value=default_rviz_config_path, description='Absolute path to rviz config file'),
+        DeclareLaunchArgument(name='use_sim_time', default_value='True', description='Flag to enable use_sim_time'),
+        ExecuteProcess(cmd=['gz', 'sim', '-g'], output='screen'),


There's a ros_gz launch file for this which includes some other useful things we should use instead

Edit: how does this play with the GZServer() you already created?

Have a look at this: https://gazebosim.org/docs/harmonic/ros2_overview/#composition
Also, I think the launch file you are mentioning is this. This launch file doesn't let you use composition and that's why I implemented what's done in this launch file.
The ExecuteProcess(cmd=['gz', 'sim', '-g'], output='screen'), simply lets you start a Gazebo GUI, without the server which we are already launching before.

mikeferguson · 2024-12-21T00:10:05Z

I'm a little unclear as to why there are <gazebo> tags and sensor plugin definitions in the URDF

I haven't looked at this PR at all - but I will note that for a long time there have been gazebo tags in many URDFs - the URDF parser silently ignores them. The SDF has usually been more the description of the scene, not the robot. I'm not sure what the "best" practices are for new gazebo.

SteveMacenski · 2024-12-21T00:23:28Z

For example, in nav2_minimal_turtlebot_simulation contributors at OSRF put together a URDF that has no gazebo / sim things in it and a separate SDF that contains the Gazebo bits to decouple them

I think this model can/should be followed. I think this was always the 'best practice' even in ROS 1, but confusion / convenience / hacking led to them kind of bleeding together since the gazebo tags don't hurt anything for non-gazebo use as you mention

If we're going to bleed them together, then I think its probably better to just use a singular file then and save the duplication maintenance work. You can actually see that we did that for the TB4 portions of that repository that were modified and pared down from the iRobot / Clearpath stacks. But I think its possible / reasonably easy, especially using those TB3 files as a baseline :-)

mikeferguson · 2024-12-21T00:33:21Z

In the turtlebot example, isn't the SRDF got a lot of duplicated things from the URDF (for instance, just the base_link definition is basically fully duplicated - if one gets updated but not the other, things get out of date)? The workflow I've seen in the past (again, ROS 1) was to create your base URDF, with no gazebo tags and then use xacro to include that and add the gazebo stuff in a more gazebo-specific urdf.

I guess I'm assuming here that ROS 2 / new gazebo still has the tools to load a URDF/xacro directly (basically, it creates the SDF under the hood) - if that's gone, it's a moot point and users have to maintain separate SDF & URDF files.

SteveMacenski · 2024-12-21T00:38:34Z

I think the intention is to long-term stop allowing or promoting users to use URDFs in this way due to the limiting nature of the URDF format w.r.t. SDF. With this said, I forget entirely where I heard that so I could just be making that up 😆

mikeferguson · 2024-12-21T00:44:14Z

I think the intention is to long-term stop allowing or promoting users to use URDFs in this way due to the limiting nature of the URDF format w.r.t. SDF. With this said, I forget entirely where I heard that so I could just be making that up 😆

I mean, this is the team that built their own ROS-alternative for Gazebo internal comms, so... I feel like Gazebo keeps getting harder and harder to use, at the same time so many alternatives keep coming on the market. /rant

Signed-off-by: Aarav Gupta <[email protected]>

SteveMacenski reviewed Dec 10, 2024

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Amronos requested a review from SteveMacenski December 14, 2024 13:16

Amronos added 6 commits December 20, 2024 22:29

Update DiffDrive, and IMU for new Gazebo

c1ee3d7

Update nav2_params.yaml Update to use stamped twist messages Add SDF description Signed-off-by: Aarav Gupta <[email protected]>

Add plugins to world file

12cda30

Signed-off-by: Aarav Gupta <[email protected]>

Fix/Update sensors and add them to SDF also

c09b40d

Signed-off-by: Aarav Gupta <[email protected]>

Update robot footprint

4b11d16

Signed-off-by: Aarav Gupta <[email protected]>

Update imu_sensor frame_id

09fcd5e

Signed-off-by: Aarav Gupta <[email protected]>

Make caster close to frictionless

8afa689

Signed-off-by: Aarav Gupta <[email protected]>

Amronos force-pushed the update-new-gazebo branch from fe3a78b to 8afa689 Compare December 20, 2024 17:00

Amronos marked this pull request as ready for review December 20, 2024 17:08

SteveMacenski reviewed Dec 20, 2024

View reviewed changes

SteveMacenski reviewed Dec 21, 2024

View reviewed changes

Amronos added 3 commits December 21, 2024 11:05

Implement review comments

29276cb

Signed-off-by: Aarav Gupta <[email protected]>

Add argument for using ekf

7c1ddc8

Signed-off-by: Aarav Gupta <[email protected]>

Some fixes

ca69a5f

Signed-off-by: Aarav Gupta <[email protected]>

Amronos requested a review from SteveMacenski December 21, 2024 06:34

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Update sam_bot_description for the new Gazebo #102

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Update sam_bot_description for the new Gazebo #102

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