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2017-04-09 07:22:51 -0600 asked a question relations of gz topic & rostopic, and how to check the information of a gz topic message type(like: mav_msgs::msgs::CommandMotorSpeed)?

I have learned that gz topics use almost the same subscribe and publish mechanism with ros topics, but what confuses me is, one name(gazebo/command/motor_speed) of two topics appears in a project. One is a ros topic and the other is a gz topic.

I checked the information of the two topics.

The first one has message type of : mav_msgs/Actuators. The latter one has message type of : mav_msgs::msgs::CommandMotorSpeed.

-1. I want to know the difference between gz topics and ros topics, which matters a lot as for things I am learning now.

-2. How can I check the content of the message type mav_msgs::msgs::CommandMotorSpeed(or any other gz topic message types)?

I would be really grateful if one can help.

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2016-05-27 11:11:16 -0600 commented answer Add color materials to my urdf models (including Collada meshes).

I get it. Thanks so much for the help.

2016-05-27 11:02:25 -0600 commented answer Add color materials to my urdf models (including Collada meshes).

About adding texture to a collada mesh, do you mean in URDF ? If so, could you please further explain the usage for me? I have worked with sdf to create my model successfully before, and are quite familiar with the methods of using materials and meshes in it. But lately I turned to urdf, I did not find tutorials teaching this part, or some ambiguous.

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2016-05-27 02:31:03 -0600 asked a question Add color materials to my urdf models (including Collada meshes).

How to add color to Collada meshes ? Since in urdf files, the color I set in SketchUp dose not work at all, I want to use the same way of adding color to a box in .gazebo (xacro) file to the dae mesh: <gazebo reference="link_name"> <material>Gazebo/Red</material> </gazebo> where the link_name refers to the link I uses meshes, but I failed.

Could anyone please tell how to import the color from SketchUp to urdf ? Or how to rewrite the color again successfully ? Is there something wrong with my file ?

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2016-05-26 17:51:40 -0600 commented answer How to use urdf_to_graphiz command to see the link relationships of my xacro models?

Thanks for your kind reminding.

2016-05-26 17:50:25 -0600 answered a question How to use urdf_to_graphiz command to see the link relationships of my xacro models?

Thanks for your kind reminding.

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2016-05-25 22:20:05 -0600 asked a question How to use urdf_to_graphiz command to see the link relationships of my xacro models?

I have run the command :rosrun xacro xacro.py model.urdf.xacro -o model.urdf

But the generated urdf file has nothing in it. I have other xacro files included by model.urdf.xacro. Dose this lead to the failure? Or is there anything else I missed?

Any one who has idea of the problem, please give me some help. I would be really grateful.

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2016-05-25 08:23:06 -0600 commented question About using ros_control in gazebo, I failed to commit the control command on my robot.

But actually I tried before adding comment on that part but also failed. I commented that part because I have already have a call for libgazebo_ros_control.so in ugvc_gazebo/urdf/description.gazebo.xacro,and for the type of the controller, ther is also parameters defined in control.yaml in ugvc_control/config/control.yaml? I thought the combination of <transmission> in ugvc_crawler_robot.urdf.xacro and the call for libgazebo_ros_control.so has the same function of the part you mentioned.

2016-05-25 07:12:00 -0600 commented question About using ros_control in gazebo, I failed to commit the control command on my robot.

Yes. I have used the plugin. I have my packages here(git@github.com:YajingWang1994/ugvc_simulation.git). Could you lease check it and give a little more help? Thanks very much.

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2016-05-25 04:49:19 -0600 asked a question About using ros_control in gazebo, I failed to commit the control command on my robot.

I can get cmd_vel news form my velocity controller, but the robot in the simulator just do not respond. I tried both controlling by joystick and keyboard. The whole process of command transmission from the source to the controller worked successfully, and there were no errors reported.

So I find difficult to find out the reason of the result. There must be something I missed. Could any one please give me some instructions? I would be very grateful.

2016-05-21 10:33:02 -0600 commented answer Why ground_plane has mu 100 mu2 50 if documentation says it's in range [0..1]

After learning discussion above, I want to make it clear, whether it would be effective if I set the 'mu' value of my robot wheels to 0.7 and that of the ground to a large value, then it would be meaningful for me to simulating the real situation, where the wheels and the ground have a friction coefficient of around 0.7.

2016-05-21 10:32:58 -0600 asked a question How to Use plugins in SDF or convert SDF to URDF?
  1. I have already written my SDF model, and are going to control it in my simulation. But I find that, it seems that plugins can only be use in URDF files, at lease those simulations I have known about are all using URDF. So I wonder if the usage of plugins are still limited to URDF? If so, is there any way to transform SDF to URDF?

    I got help from Louise Poubel: If you're trying to use Gazebo plugins, they work within both SDF and URDF. For converting SDF to URDF, see this issue.

  2. Considering I only have my SDF model and world now, I want to further ask one more question:

    Actually what I want to do is to use gazebo_ros_control package and gazebo plugins to control my robot (which are both SDF files ) in simulation, but I find it difficult for me to figure out the relations of steps in the whole process without reference to other existing simulating project. I hope , if it is possible, could any one please give me some information about such kind of resource?