To satisfy requirements for Gazebo>=1.9 in ROS Groovy:
sudo apt-get install ros-groovy-pcl-conversions
sudo apt-get install ros-groovy-control-msgs
Every session should be started as:
source ~/rosws/setup.bash
source devel/setup.bash
localmaster
or
source ~/rosws/setup.bash
localmaster
Simulator start:
roscore
rosrun gazebo_ros gazebo
roslaunch seekurjr_gazebo spawn_model.xml
roslaunch seekurjr_control steering.launch
rosrun seekurjr_control test_trajectory
roslaunch seekurjr_gazebo rqt_imu.xml
rosrun rqt_graph rqt_graph
rosrun rviz rviz -d src/seekurjr_gazebo/urdf.rviz
roslaunch seekurjr_gazebo xacrodisplay.xml model:=src/seekurjr_gazebo/urdf/seekurjr.xacro.xml
Spawn robot model:
rosrun gazebo_ros spawn_model -file seekurjr.urdf -urdf -z 1 -model seekurjr
rosrun gazebo_ros spawn_model -file src/seekurjr_gazebo/urdf/seekurjr.urdf -urdf -z 1 -model seekurjr
roslaunch seekurjr_gazebo display.xml model:=src/seekurjr_gazebo/urdf/seekurjr.urdf
Execute ROS stereoprocessing core and rqt gui control application:
ROS_NAMESPACE=mobileranger/camera rosrun stereo_image_proc stereo_image_proc
rosrun image_view stereo_view stereo:=/mobileranger/camera image:=image_rect_color
rosrun rqt_gui rqt_gui
Sample session can be seen by following video link below.
roscore
rosrun gazebo_ros gazebo
roslaunch seekurjr_gazebo spawn_model.xml
roslaunch seekurjr_control steering.launch
roslaunch seekurjr_gazebo imu.xml
roslaunch seekurjr_gazebo rqt_imu.xml
rosrun rviz rviz -d src/seekurjr_gazebo/urdf.rviz
roslaunch seekurjr_gazebo robot_pose_ekf.xml
ROS_NAMESPACE=mobileranger/camera rosrun stereo_image_proc stereo_image_proc
rosrun image_view stereo_view stereo:=/mobileranger/camera image:=image_rect_color
With launch files:
roscore
# simulator
rosrun gazebo_ros gazebo
# load model
roslaunch seekurjr_gazebo spawn_model.xml
# manual model control
roslaunch seekurjr_control steering.launch
# imu
roslaunch seekurjr_gazebo imu.xml
# stereo core
roslaunch seekurjr_gazebo stereocore.xml
# laser nodes
roslaunch seekurjr_gazebo laser.xml
roslaunch seekurjr_gazebo pcl_conv.xml
# map server
roslaunch seekurjr_gazebo octomap_server.xml
# visualisation
rosrun rviz rviz -d src/seekurjr_gazebo/urdf.rviz
roslaunch seekurjr_gazebo rqt_imu.xml
rosrun image_view stereo_view stereo:=/mobileranger/camera image:=image_rect_color
Table 1. Main SeekurJr mechanical specification
| Specification | Value |
|---|---|
| DIMENSIONS (LxWxH) | 1050mm x 840mm x 500mm |
| WEIGHT | 77kg (1 battery) |
| GROUND CLEARANCE | 105mm |
| TIRES | 400mm |
| WHEELBASE | 425mm |
Hector team uses simplified inertia tensors:
<?xml version="1.0"?>
<robot xmlns:xacro="http://ros.org/wiki/xacro">
<xacro:macro name="inertial_cuboid" params="mass x_length y_length z_length">
<inertial>
<mass value="${mass}" />
<origin xyz="0 0 0" />
<inertia ixx="${(1/12) * mass* (y_length*y_length+ z_length*z_length)}" ixy="0.0" ixz="0.0"
iyy="${(1/12) * mass* (x_length*x_length+ z_length*z_length)}" iyz="0.0"
izz="${(1/12) * mass* (x_length*x_length+ y_length*y_length)}" />
</inertial>
</xacro:macro>
<xacro:macro name="inertial_sphere" params="mass diameter">
<inertial>
<mass value="${mass}" />
<origin xyz="0 0 0" />
<inertia ixx="${(2/5) * mass* ( (diameter*0.5)) * (diameter*0.5))}" ixy="0.0" ixz="0.0"
iyy="${(2/5) * mass* ( (diameter*0.5)) * (diameter*0.5))}" iyz="0.0"
izz="${(2/5) * mass* ( (diameter*0.5)) * (diameter*0.5))}" />
</inertial>
</xacro:macro>
</robot>
According to Wikipedia, list of moment of inertia tensors:
One can calculate approximate inertai tensor for SeekurJr in Ocatve:
m=77; h=0.5; w=0.84; d=1.05;
ixx = 1/12*m*(h^2+d^2)
iyy = 1/12*m*(w^2+d^2)
izz = 1/12*m*(h^2+d^2)
Results are used in <inertia /> URDF-tag parameters:
<inertia ixx="8.6785" ixy="0" ixz="0" iyy="11.602" iyz="0" izz="8.6785" />
Another possible way to calculate inertia tensor for complicated objects is to use dedicated software. For example one can load solid mechanical model in Meshlab and calculate inertia in two steps:
- View > Show Layer Dialog
- Filter > Quality Measure and computations > Compute Geometric measures
Opened mesh /home/kp/rosws/catkin/src/seekurjr_gazebo/meshes/seekurjr_body_new_low.stl in 15 msec
All files opened in 1902 msec
Mesh Bounding Box Size 0.627341 0.394017 1.197709
Mesh Bounding Box Diag 1.408301
Mesh Volume is 0.155966
Mesh Surface is 4.018419
Thin shell barycenter 0.008623 0.248038 -0.001686
Center of Mass is 0.006557 0.130922 -0.038411
Inertia Tensor is :
| 0.011083 -0.000132 -0.000303 |
| -0.000132 0.011182 -0.000597 |
| -0.000303 -0.000597 0.005307 |
Principal axes are :
| 0.885792 -0.460959 0.053744 |
| 0.454450 0.885044 0.100860 |
| -0.094058 -0.064917 0.993448 |
axis momenta are :
| 0.011047 0.011294 0.005230 |
Applied filter Compute Geometric Measures in 12 msec
Resulting <inertia /> tag wolud be:
<inertia ixx="0.011083" ixy="-0.000132" ixz="-0.000303" iyy="0.011182" iyz="-0.000597" izz="0.005307" />
Useful links:
http://answers.ros.org/question/30539/choosing-the-right-coefficients-for-gazebo-simulation/
http://wiki.ros.org/urdf/Tutorials/Adding%20Physical%20and%20Collision%20Properties%20to%20a%20URDF%20Model
http://answers.gazebosim.org/question/4372/the-inertia-matrix-explained/
Example for SeekurJr robot can be found in seekurjr_gazebo/urdf/base.urdf.xml.
As for mu, mu2, slip1, slip2 they are explained here, notice that the values are between [0..1]. For more information check out this ODE page and just search for mu, mu2, slip1, slip2 it will be more deeply explained.
http://answers.gazebosim.org/question/1505/how-do-i-set-up-mu-and-slip-for-a-skid-steer-robot/
http://www.ode.org/ode-latest-userguide.html
For skid-steering model simulation <plugin name="skid_steer_drive_controller" filename="libgazebo_ros_skid_steer_drive.so"> is used.
Example for SeekurJr robot can be found in seekurjr_gazebo/urdf/base.urdf.xml
and seekurjr_gazebo/urdf/base.gazebo.xml.
For collision checking using the ROS motion planning packages, as few faces per link as possible are recommended for the collision meshes that you put into the URDF (ideally less than 1000). If possible, approximating the meshes with other primitives is encouraged.
Similary to other sensors, for IMU simulation we need to define corresponding link, joint, and gazebo parameters.
Example for SeekurJr robot can be found in seekurjr_gazebo/urdf/imu.urdf.xml
and seekurjr_gazebo/urdf/imu.gazebo.xml.
Similary to other sensors, bumper requires to define corresponding link, joint, and gazebo parameters.
<!-- BAMPER -->
<!--
<gazebo>
<plugin name="${name}_gazebo_ros_bumper_controller" filename="libgazebo_ros_bumper.so">
<alwaysOn>true</alwaysOn>
<updateRate>${update_rate}</updateRate>
<bumperTopicName>${name}_bumper</bumperTopicName>
<frameName>world</frameName>
</plugin>
</gazebo>
-->
http://answers.gazebosim.org/question/3877/contact-sensor-no-data-output/
http://answers.gazebosim.org/question/5355/adding-ros-integrated-contact-sensors/
http://answers.ros.org/question/29158/how-do-i-use-force-sensor-bumper-sensor-in-gazebo/
Example for SeekurJr robot can be found in seekurjr_gazebo/urdf/bumpers.urdf.xml
and seekurjr_gazebo/urdf/bumpers.gazebo.xml.
Similary to other sensors, laser rangefinder requires to define corresponding link, joint, and gazebo parameters.
General examples can be found on Gazebo wiki.
Example for SeekurJr robot can be found in seekurjr_gazebo/urdf/lms1xx.urdf.xml
and seekurjr_gazebo/urdf/lms1xx.gazebo.xml.
Similary to other sensors, laser rangefinder requires to define corresponding link, joint, and gazebo parameters.
Example for SeekurJr robot can be found in seekurjr_gazebo/urdf/stereocamera.urdf.xml
and seekurjr_gazebo/urdf/stereocamera.gazebo.xml.