Ros with Gazebo

[TOC]

Beginners Guide

If you are a total beginner to this, start here!

Prepare your environment, fisrt make sure you have install the following compenents ROS (We use Kinetic distro), Gazebo on Ubuntu 16.04.
Install the extra package for gazebo_ros.
After your environment has prepared, then you can next build up your ros workspace. Please reference to our custom ros packages -> ros-control-driver.

Testing on well installation

Check the below command whether work successfully.

cd ~/catkin_ws/src
roslaunch tm_gazebo testing_tm700.launch

If everything goes no error, the final result will look like this figure.

World : Build up your own world

You can create your own world by generating a .world file in ${your ROS workspace}/src/tm_gazebo/worlds

In a .world file, the architecture of if will be like to gazebo sdf file. You can reference to testing_world.world .

<?xml version="1.0" ?>
<sdf version="1.4" >
  <world name="default">

<!--    Add A New Model -->
<!--    <include>-->
<!--      <uri>model://${MODEL_NAME}</uri>-->
<!--      <name>${MODEL_DISPLAY_NAME}</name>-->
<!--      <pose>${POSE: tx, ty, tz, rx, ry, rz}<pose>-->
<!--    </include>-->

    <include>
      <uri>model://cafe_table</uri>
      <name>cafe_table</name>
      <pose>0 0 0 0 0 0</pose>
    </include>

<!--    Add A New Sensor-->
<!--    This new sensor will be released later...-->
    
    <!-- Camera -->
    <model name="camera">
      <static>true</static>
      <pose>-1 0 2 0 1 0</pose>
      <link name="link">
        <visual name="visual">
          <geometry>
            <box>
              <size>0.1 0.1 0.1</size>
            </box>
          </geometry>
        </visual>
        
        <sensor name="my_camera" type="camera">
          <camera>
            <save enabled="true">
              <path>/tmp/gazebo_camera_images</path>
            </save>
            <image>
              <width>1920</width>
              <height>1080</height>
            </image>
            <clip>
              <near>0.1</near>
              <far>100</far>
            </clip>
          </camera>
<!--	  <plugin name="camera_dump" filename="libcamera_dump.so"/>-->
          <always_on>1</always_on>
          <update_rate>30</update_rate>
        </sensor>
      </link>
    </model>
  </world>
</sdf>

Robot : Control your own robot

Sensor : Camera

Camera

Use a normal camera in gazebo, below, we create a camera as a model with a visuable box and a virtual sensor.

As you want to visualize the camera in gazebo, then you need to add <visual> tag in your model. And make the visuable object to have ability of sensoring the view it has seen, we need <sensor> to construct the configurations for camera.

Other tags like,

In <model> :
- <static> can specified the camera is non-movable or not.
- <pose> can specified the initial pose of the camera.
In <sensor> :
- <camera> can specified some camera features.
  - Its <clip>, is always power on <always_on>
  - The rate of capturing the view <update_rate>

    <model name="camera">
      <static>true</static>
      <pose>-1 0 2 0 1 0</pose>
      <link name="link">
        <visual name="visual">
          <geometry>
            <box>
              <size>0.1 0.1 0.1</size>
            </box>
          </geometry>
        </visual>
        
        <sensor name="my_camera" type="camera">
          <camera>
            <save enabled="true">
              <path>/tmp/gazebo_camera_images</path>
            </save>
            <image>
              <width>1920</width>
              <height>1080</height>
            </image>
            <clip>
              <near>0.1</near>
              <far>100</far>
            </clip>
          </camera>
<!--	  <plugin name="camera_dump" filename="libcamera_dump.so"/>-->
          <always_on>1</always_on>
          <update_rate>30</update_rate>
        </sensor>
      </link>
    </model>

In details, due to this lines, we can dump the images that the camera captures at 30 frames per second and the resolution is 1920 x 1080 specified by the <width> and the <height> in the <image> tag.

    <save enabled="true">
      <path>/tmp/gazebo_camera_images</path>
    </save>
    <image>
      <width>1920</width>
      <height>1080</height>
    </image>

Moreover, the <plugin> tag gives an another way to dump the images by c++ script. You can change the above config on camera like this.

    <model name="camera">
      <static>true</static>
      <pose>-1 0 2 0 1 0</pose>
      <link name="link">
        <visual name="visual">
          <geometry>
            <box>
              <size>0.1 0.1 0.1</size>
            </box>
          </geometry>
        </visual>
        
        <sensor name="my_camera" type="camera">
          <camera>
            <image>
              <width>1920</width>
              <height>1080</height>
            </image>
            <clip>
              <near>0.1</near>
              <far>100</far>
            </clip>
          </camera>
	  <plugin name="camera_dump" filename="libcamera_dump.so"/>
          <always_on>1</always_on>
          <update_rate>30</update_rate>
        </sensor>
      </link>
    </model>

lluma/gazebo_ros_tutorial