Matlab Ros Gazebo Add force to Ball

Hello together,

I'm a beginner with Matlab Gazebo tool, so I'm working with a virtual Machine using the VMWare Workstation with an Gazebo world.

In these World there is the turtle bot, so i was folliwing the tutorial of the https://de.mathworks.com/support/product/robotics/ros2-vm-installation-instructions-v3.html site.

So now i spawned several models to the gazebo (following the https://de.mathworks.com/help/ros/ug/add-build-remove-objects-in-gazebo.html tutorial) world but there are some errors with the ExampleHelperGazeboSpawnedModel function.

If I want to get the state of the model to add some forc to the ball, then i get the error:

Error using ExampleHelperGazeboSpawnedModel/getState (line 104)

Error during service call, cannot get the state of the model

Error in ExampleHelperGazeboSpawnedModel (line 70)

[obj.Position, obj.Orientation, obj.Velocity] = getState(obj);

I was checking the ExampleHelperGazeboSpawnedModel()-function. There at Line 70, the function calls the

msg = call(obj.GetStateClient,serviceMsg);

then the error occorus.

I'm working with Matlab2020b, so the current verison. I found some workaround (https://de.mathworks.com/matlabcentral/answers/423993-spawnmodel-error-in-robotics-system-toolbox) to solve these problem, to change some java files on my host PC, but these java-file witch i did not found on my pc.

So does anybody know some other idea to solve these problem?

Thank you very much in advance.

Regards,

Philipp

Answer 1

[Cam Salzberger]

Hello Philipp,

There is an issue with the specific service definition that is used in that call command. We are working on a resolution for this issue.

A somewhat time-consuming workaround in the meantime would be to regenerate the gazebo_msgs package (using the Melodic version of the package) using rosgenmsg. I believe this should ensure that the service is able to communicate, though I have not tested this personally.

-Cam