gazebo_simulation¶
ROS package to better communicate with Gazebo.
simulation/src/gazebo_simulation
├── launch
│ ├── test
│ │ ├── automatic_drive.test
│ │ ├── car_model_generation.test
│ │ ├── car_state_node.test
│ │ └── model_plugin_link.test
│ ├── automatic_drive.launch
│ ├── car_state_node.launch
│ ├── gazebo_rate_control_node.launch
│ ├── master.launch
│ ├── record_random_drive.launch
│ ├── road_editor.launch
│ ├── spawn_car.launch
│ └── world.launch
├── msg
│ ├── CarState.msg
│ ├── SetModelPose.msg
│ └── SetModelTwist.msg
├── param
│ ├── automatic_drive
│ │ ├── test
│ │ │ └── path.yaml
│ │ ├── default.yaml
│ │ └── path.yaml
│ ├── car_specs
│ │ └── dr_drift
│ │ ├── camera.yaml
│ │ ├── car_specs.yaml
│ │ ├── model.urdf
│ │ └── static_coordinate_systems.yaml
│ ├── car_state
│ │ ├── default.yaml
│ │ └── topics.yaml
│ ├── gazebo_rate_control
│ │ ├── default.yaml
│ │ └── topics.yaml
│ └── model_plugin_link
│ ├── default.yaml
│ └── topics.yaml
├── res
│ ├── KITcar_Logo.svg
│ └── simulation.rviz
├── scripts
│ ├── automatic_drive_node
│ ├── car_state_node
│ ├── car_state_visualization_node
│ ├── gazebo_rate_control_node
│ └── generate_dr_drift
├── src
│ ├── automatic_drive
│ │ ├── __init__.py
│ │ └── node.py
│ ├── car_model
│ │ ├── camera_specs.py
│ │ ├── car_specs.py
│ │ ├── dr_drift.py
│ │ ├── __init__.py
│ │ └── tof_sensors.py
│ ├── car_state
│ │ ├── __init__.py
│ │ ├── node.py
│ │ └── visualization.py
│ ├── gazebo_rate_control
│ │ ├── index.rst
│ │ ├── __init__.py
│ │ └── node.py
│ ├── model_plugin_link
│ │ ├── CMakeLists.txt
│ │ ├── __init__.py
│ │ ├── model_plugin_link.cpp
│ │ └── model_plugin_link.h
│ ├── world_plugin_link
│ │ ├── CMakeLists.txt
│ │ ├── world_plugin_link.cpp
│ │ └── world_plugin_link.h
│ └── __init__.py
├── test
│ ├── test_automatic_drive
│ ├── test_car_model_generation
│ ├── test_car_state_node
│ └── test_model_plugin_link
├── CMakeLists.txt
├── __init__.py
├── package.xml
└── setup.py
21 directories, 64 files
Packages and Modules
master.launch¶
The master.launch master_launch file includes all necessary components to run the simulation locally. Refer to the actual source code for more details on available parameters.
Launch
Start the complete simulation with
roslaunch gazebo_simulation master.launch
See also
Getting Started for more details.
Model of the Car¶
An important part of the simulation is the vehicle it self. It should be a realistic representation of the real car. In our case we do not simulate the actual tire movement and basically move a box around the simulated world. This simplifies the model significantly! Nevertheless, the sensors must be defined and should be as close to their real specifications as possible. Instead of calculating or estimating their position and calibrations, the sensors specifications are extracted from the car_specs ROS package within KITcar_brain.
Gazebo allows to define models using the urdf standard. However, defining a model consisting of multiple parts and sensors is repetitive. So instead of writing the urdf by hand, there’s a Python script that generates it!
Generate Dr. Drift
Generate a new model definition of Dr. Drift and an updated calibration by running:
rosrun gazebo_simulation generate_dr_drift
Behind the scenes, there are multiple things going on:
The car_specs and camera_specs are loaded using
simulation.src.gazebo_simulation.src.car_model.car_specs.CarSpecsandsimulation.src.gazebo_simulation.src.car_model.camera_specs.CameraSpecs.
The model of Dr.Drift is defined as an
simulation.utils.urdf.core.XmlObjectinsimulation.src.gazebo_simulation.src.car_model.dr_drift. Using the urdf package allows to define classes for the individual parts of the vehicle.
The model, the car specs and the camera calibration is saved to
simulation/src/gazebo_simulation/param/car_specs/dr_drift/.
CarStateNode¶
The simulation.src.gazebo_simulation.src.car_state.node.CarStateNode subscribes to Gazebo updates and publishes information about the cars current state
(position + speed + …) in shape of a CarState Message.
Launch
roslaunch gazebo_simulation car_state_node.launch
By default the parameter rviz is true and simulation.src.gazebo_simulation.src.car_state.visualization.CarStateVisualizationNode is launched as well.
Enabling to display the car’s frame and field of view in RVIZ.
GazeboRateControlNode¶
The simulation.src.gazebo_simulation.src.gazebo_rate_control.node.GazeboRateControlNode can control Gazebo’s maximum update rate to ensure that a specified topic publishes with a large enough rate.
It is primarily necessary because Gazebo does not ensure a sensor update rate in Docker containers.
This node is not started in the master.launch file by default. It can be manually started by passing the parameter control_sim_rate:=true or running:
Launch
roslaunch gazebo_simulation gazebo_rate_control_node.launch
ModelPluginLinkNode¶
The ModelPluginLinkNode is a Gazebo model plugin that allows to interact with models in Gazebo easily.
It can be attached to Gazebo models by adding
<plugin filename="libmodel_plugin_link.so" name="model_plugin_link"/>
to the model.sdf.
When Gazebo loads a model with the model_plugin_link, a new instance of the model plugin link node is created. The model plugin link node creates two publisher’s:
/simulation/gazebo/model/MODEL_NAME/pose (geometry_msgs/Pose.msg): Publish the model’s pose.
/simulation/gazebo/model/MODEL_NAME/twist (geometry_msgs/Twist.msg): Publish the model’s twist.
And two subscribers:
/simulation/gazebo/model/MODEL_NAME/set_pose (SetModelPose Message): Receive new model pose.
/simulation/gazebo/model/MODEL_NAME/set_twist (SetModelTwist Message): Receive new model twist.
![digraph ModelPluginLink {
node [style=dotted, shape=box]; model [label="Gazebo model"];
node [style=solid, shape=ellipse]; model_plugin_link_node [label="model_plugin_link"];
node [shape=box]; pose_topic [label="pose"]; twist_topic [label="twist"];set_pose_topic [label="set_pose"]; set_twist_topic[label="set_twist"];
node [style=solid, shape=ellipse]; other_nodes;
model -> model_plugin_link_node [style=dotted, dir=both];
model_plugin_link_node -> pose_topic;
model_plugin_link_node -> twist_topic;
set_twist_topic -> model_plugin_link_node;
set_pose_topic -> model_plugin_link_node;
twist_topic -> other_nodes;
pose_topic -> other_nodes;
other_nodes -> set_pose_topic;
other_nodes -> set_twist_topic;
subgraph topics {
rank="same"
pose_topic
set_pose_topic
twist_topic
set_twist_topic
}
subgraph gazebo {
rank="same"
label="Gazebo"
model
}
}](../_images/graphviz-1c9d55521931da044ae456b2119ec57a8e746d1f.png)
Schema of the Model Plugin Link¶
WorldPluginLinkNode¶
The WorldPluginLinkNode is a Gazebo world plugin that allows to interact with worlds in Gazebo easily. In particular, it allows to spawn and remove models from the world.
It can be attached to Gazebo worlds by adding
<plugin filename="libworld_plugin_link.so" name="world_plugin_link" />
to the model.sdf.
When Gazebo loads a world with the world_plugin_link, a new instance of the world plugin link node is created. The model plugin link node creates two subscribers:
/simulation/gazebo/world/spawn_sdf_model (string): Receive sdf model definition.
/simulation/gazebo/world/remove_model (string): Receive name of the model to be removed.
![digraph WorldPluginLink {
node [style=dotted, shape=box]; world [label="Gazebo world"];
node [style=solid, shape=ellipse]; world_plugin_link_node [label="world_plugin_link"];
node [shape=box]; spawn_sdf [label="spawn_sdf_model"]; remove_model [label="remove_model"];
node [style=solid, shape=ellipse]; other_nodes;
world -> world_plugin_link_node [style=dotted, dir=both];
world_plugin_link_node -> spawn_sdf[dir="back"];
world_plugin_link_node -> remove_model[dir="back"];
spawn_sdf -> other_nodes[dir="back"];
remove_model -> other_nodes[dir="back"];
subgraph gazebo {
rank="same"
label="Gazebo"
world
}
subgraph topics {
rank="same"
spawn_sdf
remove_model
}
}](../_images/graphviz-f4b64ade34ec04f3c7407842b07372c3b6bc4f29.png)
Schema of the World Plugin Link¶
AutomaticDriveNode¶
The simulation.src.gazebo_simulation.src.automatic_drive.node.AutomaticDriveNode
moves the car on the right side of the road.
It can be used instead of KITcar_brain.
Launch
roslaunch gazebo_simulation automatic_drive.launch
The speed of the car can be modified by passing speed:=… as a launch parameter. (Or by modifying the parameter with rosparam at run-time.)