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2020-06-09 04:45:22 -0500 received badge  Notable Question (source)
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2020-05-14 08:33:43 -0500 edited question gazebo: symbol lookup error - ignition math / libignition issue after upgrade from 9.0 to 9.13

gazebo: symbol lookup error - ignition math / libignition issue after upgrade from 9.0 to 9.13 Hello, I installed Gaze

2020-05-14 08:00:32 -0500 asked a question gazebo: symbol lookup error - ignition math / libignition issue after upgrade from 9.0 to 9.13

gazebo: symbol lookup error - ignition math / libignition issue after upgrade from 9.0 to 9.13 Hello, I installed Gaze

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2020-03-12 07:53:51 -0500 marked best answer Can Gazebo publish /tf (transform) data?

Hello,

The system is running Ubuntu 16.04, ROS Kinetic, and Gazebo 7.16. The model being used in Gazebo is a modified URDF file.

Can I get /tf data from Gazebo? or, if that's not possible, How do I get the position of all the continuous joints from Gazebo? How do I get the status of every moving joint?

When I fire up RViz, I get a bunch of errors under robotModel because there is no /tf data. Image below shows the robot in RViz after forward motion was executed in Gazebo (using diff_drive plugin).The base_link /tf is OK (relative to /odom) but all other links (the white items) are not ok and are left behind (missing /tf data):

image description

Thanks.

Edit #1

based on my limited skills, readSim() looks like the way to do it (based on http://gazebosim.org/tutorials/?tut=r...).

image description

I looked up the code samples Mr Dave Coleman put up (https://github.com/ros-simulation/gaz...), but there is no example of readSim().

Any advice on how to get the status of joints, is appreciated.

2020-03-12 07:53:42 -0500 answered a question Can Gazebo publish /tf (transform) data?

I got this done using this answer: https://answers.ros.org/question/273947/moving-joints-in-gazebo-simple-example/. By i

2020-03-12 07:33:35 -0500 received badge  Notable Question (source)
2020-03-11 09:13:35 -0500 edited question Can Gazebo publish /tf (transform) data?

Can Gazebo publish /tf (transform) data? Hello, The system is running Ubuntu 16.04, ROS Kinetic, and Gazebo 7.16. The m

2020-03-11 06:17:10 -0500 edited question Can Gazebo publish /tf (transform) data?

Can Gazebo publish /tf (transform) data? Hello, The system is running Ubuntu 16.04, ROS Kinetic, and Gazebo 7.16. The m

2020-03-11 06:14:50 -0500 received badge  Popular Question (source)
2020-03-10 17:45:34 -0500 edited question Can Gazebo publish /tf (transform) data?

Can Gazebo publish /tf (transform) data? Hello, The system is running Ubuntu 16.04, ROS Kinetic, and Gazebo 7.16. The m

2020-03-10 17:44:29 -0500 edited question Can Gazebo publish /tf (transform) data?

Can Gazebo publish /tf (transform) data? Hello, The system is running Ubuntu 16.04, ROS Kinetic, and Gazebo 7.16. The m

2020-03-10 17:43:46 -0500 asked a question Can Gazebo publish /tf (transform) data?

Can Gazebo publish /tf (transform) data? Hello, The system is running ROS 16.04, and Gazebo 7.16. The model being used

2020-02-25 18:56:37 -0500 received badge  Famous Question (source)
2020-02-22 13:34:23 -0500 edited question Caster wheel sample code

Caster wheel sample code Hello, Can you please provide a urdf sample for a correctly working caster wheel setup? I have

2020-02-22 13:30:28 -0500 edited question Caster wheel sample code

Caster wheel sample code Hello, Can you please provide a urdf sample for a correctly working caster wheel setup? I have

2020-02-22 13:29:02 -0500 edited question Caster wheel sample code

Caster wheel sample code Hello, Can you please provide a urdf sample for a correctly working caster wheel setup? I have

2020-02-22 13:18:41 -0500 commented question Caster wheel sample code

@chapulina Could you please see edit #1 in the question? Thanks for your time, and please let me know what other informa

2020-02-22 13:16:46 -0500 edited question Caster wheel sample code

Caster wheel sample code Hello, Can you please provide a urdf sample for a correctly working caster wheel setup? I have

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2020-02-18 10:22:40 -0500 asked a question Caster wheel sample code

Caster wheel sample code Hello, Can you please provide a urdf sample for a correctly working caster wheel setup? I have

2020-02-17 01:42:29 -0500 received badge  Notable Question (source)
2020-02-16 11:38:57 -0500 commented answer model contact with ground issue

As soon as I put these values (for all 4 wheels), the castor wheels stopped moving, and the robot stopped shifting the w

2020-02-15 20:55:28 -0500 commented answer model contact with ground issue

As soon as I put these values (for all 4 wheels), the castor wheels stopped moving, and the robot stopped shifting the w

2020-02-15 20:52:41 -0500 edited answer model contact with ground issue

The issue was the absense of kp and kd tags. Those tags are mentioned here: http://gazebosim.org/tutorials/?tut=ros_urdf

2020-02-15 20:52:13 -0500 received badge  Popular Question (source)
2020-02-15 18:02:32 -0500 edited answer model contact with ground issue

wow, that took some effort. the issue was the absense of kp and kd tags. Those tags are mentioned here: http://gazebos

2020-02-15 18:01:00 -0500 marked best answer model contact with ground issue

Hello,

I am running Gazebo7 ver 7.16 in Ubuntu 16.04 and Ros Kinetic.

I have a four wheeled robot that I am trying to simulate in Gazebo:

image description

The two front castor wheels are behaving "strange". I believe there are two issues and they are related:

Issue #1 - Dancing / moving / rotating I took pictures of the model in with no commands being given to it, and if you look at the two images below you will see the two front castor wheels are in slightly different positions (they have moved). The two wheels keep doing this motion where they turn inwards, and then outwards. this motion is done by both wheels and it takes about a second to do (inward to outward about a sec, and outward to inward about a sec). This motion never stops. I am hoping to eliminate this motion:

image description

image description

Here is a close up of the right wheel showing this motion (right wheel relative to robot):

image description

image description

Issue #2 - Contact with ground - I selected "contacts" from the "view" menu and the part of the wheel that makes contact with the ground changes many, many times a second. To show you what I mean I paused the simulation and took images as I pressed the "step" button on the bottom toolbar:

image description

image description

image description

image description

image description

image description

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Any suggestion on how my urdf has to change? what tags do I need to add to make the robot more stable?

My urdf is just shy of 800 lines, so I only included the items relevent to the right wheel (as the left wheel is identical).

reference image:

image description

URDF:

  <link name="right_castor_mount_link">
    <collision>
      <geometry>
        <box size="0.1145 0.1 0.0057"/>
      </geometry>
      <origin rpy="0 0 0" xyz="0 0 0"/>
    </collision>
    <visual>
      <geometry>
        <box size="0.1145 0.1 0.0057"/>
      </geometry>
      <origin rpy="0 0 0" xyz="0 0 0"/>
      <material name="black"/>
    </visual>
    <inertial>
      <origin rpy="0 0 0" xyz="0 0 0"/>
      <mass value="0.25"/>
      <inertia ixx="0.000209010208333" ixy="0" ixz="0" iyy="0.000273807083333" iyz="0" izz="0.000273807083333"/>
    </inertial>
  </link>

  <joint name="base_to_right_castor_mount_joint" type="fixed">
    <parent link="base_link"/>
    <child link="right_castor_mount_link"/>
    <origin xyz="-0.09445 -0.344 -0.03265"/>
  </joint>


  <link name="right_castor_dummy_link">
    <collision>
      <geometry>
        <box size="0.02 0.02 0.02"/>
      </geometry>
      <origin rpy="0 0 0" xyz="0 0 0"/>
    </collision>
    <visual>
      <geometry>
        <box size="0.02 0.02 0.02"/>
      </geometry>
      <origin rpy="0 0 0" xyz="0 0 0"/>
      <material name="orange"/>
    </visual>
    <inertial>
      <origin rpy="0 0 0" xyz="0 0 0"/>
      <mass value="0.25"/>
      <inertia ixx="1.66666666667e-05" ixy="0" ixz="0" iyy="1.66666666667e-05" iyz="0" izz="1.66666666667e-05"/>
    </inertial>
  </link>


  <joint name="right_castor_mount_to_right_castor_dummy_joint" type="continuous">
    <axis rpy="0 0 0" xyz="0 0 1"/>
    <parent link="right_castor_mount_link"/>
    <child link="right_castor_dummy_link"/>
    <origin xyz="0.0 0.0  -0.01"/>
    <dynamics damping="0.0" friction="1.0"/>
  </joint>


  <link name="right_castor_wheel_link">
    <collision>
      <geometry>
        <cylinder length="0.049" radius="0.07925"/>
      </geometry>
      <origin rpy="1.57079632679 0 0" xyz ...
(more)
2020-02-15 18:00:48 -0500 answered a question model contact with ground issue

wow, that took some effort. the issue was the absense of kp and kd tags. Those tags are mentioned here: http://gazebos

2020-02-15 14:20:33 -0500 edited question model contact with ground issue

model contact with ground issue Hello, I am running Gazebo7 ver 7.16 in Ubuntu 16.04 and Ros Kinetic. I have a four wh

2020-02-15 14:11:40 -0500 edited question model contact with ground issue

model contact with ground issue Hello, I am running Gazebo7 ver 7.16 in Ubuntu 16.04 and Ros Kinetic. I have a four wh

2020-02-15 14:09:49 -0500 edited question model contact with ground issue

model contact with ground issue Hello, I am running Gazebo7 ver 7.16 in Ubuntu 16.04 and Ros Kinetic. I have a four wh

2020-02-15 14:09:07 -0500 edited question model contact with ground issue

model contact with ground issue Hello, I am running Gazebo7 ver 7.16 in Ubuntu 16.04 and Ros Kinetic. I have a four wh

2020-02-15 14:02:24 -0500 edited question model contact with ground issue

model contact with ground issue Hello, I am running Gazebo7 ver 7.16 in Ubuntu 16.04 and Ros Kinetic. I have a four wh

2020-02-15 14:00:07 -0500 asked a question model contact with ground issue

model contact with ground issue Hello, I am running Gazebo7 ver 7.16 in Ubuntu 16.04 and Ros Kinetic. I have a four wh

2020-02-11 01:41:12 -0500 received badge  Notable Question (source)
2020-02-10 16:55:15 -0500 commented answer Issues installing gazebo7

When I installed Kinetic, the version that came with it was 7.0, and I jumped through hoops to get 7.16 working (which i

2020-02-10 16:53:42 -0500 marked best answer Issues installing gazebo7

I am running ROS Kinetic on Ubuntu 16.04. As per http://gazebosim.org/tutorials?tut=ro... I need Gazebo7. I want to install the latest LTS version (which I believe is 7.16.0-1).

The link to the instructions for installing Gazebo on Ubuntu does not work. Try it: http://gazebosim.org/tutorials?cat=in...

The installer download link also doesn't work. Go to http://gazebosim.org/tutorials?cat=gu... scroll to "installation for Ubuntu" and click on "link to the installer". didn't work for me.

No worries. I'll just download the software and off I go, right? I wish. On this page (http://gazebosim.org/distributions/ga...) there are 7 files that are "Gazebo7 ... 7.16.0-1 (docs, dbg, plugin-base, libgazebo7, common, and gazebo7), and every one depends on the other. I tried installing each one over and over in different orders, but I keep getting unmet dependencies.

Installing Gazebo from source makes my head spin (I'm not a programmer, and this is too much for me: http://gazebosim.org/tutorials?tut=in...)

Gazebo is so cool, and I need the latest Gazebo7 version. What do I need to do to install Gazebo7? Thanks for your time.

2020-02-10 16:48:30 -0500 commented answer How to specify URDF link which attaches to world ground?

@nlamprian thanks for your help... Much appreciated! I looked at the collisions as you suggested and it was cool to lear

2020-02-10 16:46:32 -0500 marked best answer How to specify URDF link which attaches to world ground?

Hello. The system is Gazebo7 (ver 7.16), running ROS Kinetic, in Ubuntu 16.04. The model I am working with looks like so:

image description

The problem is that when I start the simulation my robot jumps up like crazy (13 meters or so) and lands painfully. I was able to figure out that the jump occurs due to the fact that the simulation starts with the robot partially "inside" the ground:

image description

I now understand that the reason for this is that my base_link (the largest box in the center of the robot) which is the coordinate system origin of my model is snapped to the ground of the simulation (figured this out using: https://answers.ros.org/question/2251...). The problem is that the base_link is not the lowest part of the model.

I tried moving the Z axis of the <origin> tag of the base_link in the URDF file, but it didn't have the desired effect:

image description

Is there a tag I can integrate into my URDF that dictates which link snaps to the ground? or is there a mod I can do in the .world file? I am hoping the simulation can be started with the wheels on the ground rather than inside the ground.

Last piece of information: I saved the world with the robot on all four wheels, and when I launch the simulation all is well; however as soon as I select "Reset world" from the "Edit" menu, the robot jumps super high.

I have attached the URDF for the base_link for reference:

<link name="base_link">
    <!--If you do not explicitly specify a <collision> element. Gazebo will 
  treat your link as "invisible" to laser scanners and collision checking-->
<collision>
  <geometry>
    <box size="0.65 0.381 0.132"/>
  </geometry>
  <!-- line below allows us to insert:<origin rpy="${rpy}" xyz="${xyz}"/>-->
  <origin rpy="0 0 0" xyz="-0.325 -0.1905 0.066"/>
</collision>
<visual>
  <geometry>
    <!--box dimensions is Meters. L X W X H where the L X H is a ractange, 
          and the H extrudes it upwards -->
    <box size="0.65 0.381 0.132"/>
  </geometry>
  <!-- line below allows us to insert:<origin rpy="${rpy}" xyz="${xyz}"/>-->
  <origin rpy="0 0 0" xyz="-0.325 -0.1905 0.066"/>
  <material name="white"/>
</visual>
<inertial>
  <!-- line below allows us to insert:<origin rpy="${rpy}" xyz="${xyz}"/>-->
  <origin rpy="0 0 0" xyz="-0.325 -0.1905 0.066"/>
  <!--all blocks now need a 'mass' argument-->
  <mass value="25"/>
  <!--This is the 3x3 inertial matrix. See: https://wiki.ros.org/urdf/XML/link -->
  <!--where x=length; y=width; z=height. these lines of code came from 
    Emiliano Borghi's project-->
  <inertia ixx="0.33871875" ixy="0" ixz="0" iyy="0.916508333333" iyz="0" izz="0.916508333333"/>
</inertial>
</link>

Thanks in advance.