ROS技术点滴 —— gazebo中的常用插件
A plugin is a chunk of code that is compiled as a shared library and inserted into the simulation. Previous versions of Gazebo utilized controllers.
These behaved in much the same way as plugins, but were statically compiled into Gazebo.
Plugins are more flexible, and allow users to pick and choose what functionality to include in their simulations. Each plugin type is managed by a different component of Gazebo. For example, a Model plugin is attached to and controls a specific model in Gazebo.
Similarly, a World plugin is attached to a world, and a Sensor plugin to a specific sensor. The System plugin is specified on the command line, and loads first during a Gazebo startup. This plugin gives the user control over the startup process. A plugin type should be chosen based on the desired functionality. Use a World plugin to control world properties, such as the physics engine, ambient lighting, etc. Use a Model plugin to control joints, and state of a model.
Use a Sensor plugin to acquire sensor information and control sensor properties. Plugins are designed to be simple. A bare bones world plugin contains a class with a few member functions. First, if you installed Gazebo from debians, make sure you've installed the Gazebo development files. If you installed Gazebo from source, you can ignore this step.8 Adding LiDAR sensor to our simple Robot - gazebo plugin
If you have a release other than gazebo6, replace 6 with whatever version number you have. All plugins must be in the gazebo namespace. Each plugin must inherit from a plugin type, which in this case is the WorldPlugin class. The only other mandatory function is Load which receives an SDF element that contains the elements and attributes specified in loaded SDF file.
The only parameter to this macro is the name of the plugin class.
Please make sure that gazebo has been properly installed. This is done with the following line:. Note : This changes the path only for the current shell. Once you have a plugin compiled as a shared library see aboveyou can attach it to a world or model in an SDF file see SDF documentation for more info. On startup, Gazebo parses the SDF file, locates the plugin, and loads the code.
It is important that Gazebo is capable of finding the plugin. Create a world file and copy the code below into it. Gazebo is open-source licensed under Apache 2. Toggle navigation. Tutorials Download Blog Media Projects.
Plugins Edit Version: 1.In the previous chapter, we have seen how to publish directed navigation goals to the differential drive robot. The takeaways from this chapter will get us closer to the objective of enabling the robot drive autonomously to a goal in given map. We will see how to:. All the source code changes for this chapter to be done in a new directory. Lidar is a scanning method that uses lasers to measure distances of objects in the device surroundings. Such a map, in turn, helps robot navigate smoothly by choosing the best path and avoiding obstacles.
Laser scan data is one of the main sources of odometry in modern robots. The plugin used in this section is a Hokuyo Lidar model that can be customized based on your Lidar device specification.
Optionally, for better visualization, a mesh file can be used instead of a box for the visual geometry of the laser scanner. For that, download the mesh file hokuyo. Then replace visual geometry description of laser scanner in kbot. In Gazebo, you should see laser scan rays all around the robot degree scanner. From Gazebo model library, place any random object e. Cube 20k near the robot. Increase the size to 0. The robot see only the front side of the object, hence visualiazation sometimes is just a line.
In this section we will use Gazebo building editor to create a simple closed room model, insert that model into the empty world and save it save it as a new world map.
Eventually, KBot will use this map for navigation. Close the building editor to return to Gazebo main GUI. To enable autonomous navigation of robot within the map, the same map as the one in Gazebo needs to recreated in rviz.
The robot uses laser sensor data to create a map of its surrounding using a technique called SLAM — Simultaneous Localization and Mapping. The package also subscribes to laser scan topic to create the map.
Needless to say, it publishes the created map to a topic called map which can be visualized in rviz. Add Map and LaserScan visualizations to rviz. Now, looking into Gazebo map and using teleop keyboard controls, drive the robot around to map all the walls of closed room. Map created in rviz should look identical to the one in Gazebo.
Above command dumps the rviz map information to two files —. And, start the map server to visualize the map in rviz. Your custom map appears automatically on Gazebo simulator.
These issues will be fixed in the next chapter.Gazebo plugins give your URDF models greater functionality and can tie in ROS messages and service calls for sensor output and motor input. In this tutorial we explain both how to setup preexisting plugins and how to create your own custom plugins that can work with ROS.
Gazebo supports several plugin typesand all of them can be connected to ROS, but only a few types can be referenced through a URDF file:. For example:.
Also, it will be give a reference to the SDF element of itself, in order to read the plugin parameters passed to it. Specifying sensor plugins is slightly different. We suggest you review them in order because more detail is covered in the first couple of plugins and you can learn some of the concepts from the various plugins' documentation. The names of each section is derived from the plugin class name.
If there are some sections blank, it means that this author got tired of documenting every plugin and you should fill in the area with your experience should you have knowledge and examples of how to use the particular plugin. You can look inside rrbot. The first elements of this block are an extra link and joint added to the URDF file that represents the camera. We are just using a simple red box to represent the camera, though typically you could use a mesh file for a better representation.
Next we will review the Gazebo plugin that gives us the camera functionality and publishes the image to a ROS message. In the RRBot we have been following the convention of putting Gazebo elements in the rrbot.
The sensor name "camera1" must be unique from all other sensor names. The name is not used many places except for within Gazebo plugins you can access.
Number of times per second a new camera image is taken within Gazebo. This is the maximum update rate the sensor will attempt during simulation but it could fall behind this target rate if the physics simulation runs faster than the sensor generation can keep up.
Fill in these values to match the manufacturer's specs on your physical camera hardware. One thing to note is that the pixels are assumed to be square. Additionally, the near and far clips are simulation-specific parameters that give an upper and lower bound to the distance in which the cameras can see objects in the simulation. This is specified in the camera's optometry frame.
Here we define the rostopic the camera will be publishing to, for both the image topic and the camera info topic. For RRBot, you should subscribe to:.Prerequisites: Attach a Mesh as Visual. Adding a laser to a robot, or any model, is simply a matter of including the sensor in the model. In this case we place the hokuyo laser forward and above the robot.
The joint is fixed to prevent it from moving. When the hokuyo model is inserted, the hokuyo's links are namespaced with their model name. In this case the model name is hokuyoso each link in the hokuyo model is prefaced with hokuyo Now start gazebo, and add the robot to the simulation using the Insert tab on the GUI.
If the hokuyo model does not exist locally, Gazebo will pull the model from the Model Database. Alternatively, manually download the model files to your local cache:. Optional Try adding a camera to the robot.
For reference, the SDF documentation can be found here. Gazebo is open-source licensed under Apache 2. Toggle navigation. Tutorials Download Blog Media Projects. Add a Sensor to a Robot. Edit Version: 1. Table of Contents. Adding a Laser Adding a laser to a robot, or any model, is simply a matter of including the sensor in the model.
Gazebo plugins in ROS
Next Next: Make a Simple Gripper.For a first test I want to use the gazebo plugin for the Hokuyo node, I later want to attach it to a Huskywhen I run.
The plugin starts and in the terminal appears "starting to spin" but there is no model in gazebo and moreover there are no scan messages published which I need for rviz etc. Please start posting anonymously - your entry will be published after you log in or create a new account. Asked: Unable to locate package ros-fuerte-laser-drivers. Possible to declare static object in urdf file? Is there a book that is best for learning gazebo? First time here? Check out the FAQ! Hi there! Please sign in help.
How can I use the plugin so I can get scan messages? Add Answer. Question Tools Follow. Related questions How to use a gazebo plugin gazebo collision detection Rviz xyz plane view Unable to locate package ros-fuerte-laser-drivers problems with a simple realtime joint controller in Gazebo Possible to declare static object in urdf file? Velocities in gazebo Gazebo shutdown BadDrawable Is there a book that is best for learning gazebo? Powered by Askbot version 0.
We also assume that you are an expert tutorial reader read everything carefully, and completely. Each of the above topics will be covered in separate tutorials. The rest of this tutorial will focus on the creation of the Velodyne SDF model. The fist step when creating a new model is to collect information about the model.
If detailed information about a model is not available, then you can measure a physical version, ask the manufacturer for specifications, or in the worst case guess.
We will Use the Velodyne sensor dimensions to construct a base cylinder and a top cylinder. Below is an screenshot of the Velodyne 2D drawing.
When building a new model, it is a good idea to periodically try out small changes. Start Gazebo paused so that you can view the model without the physics engine altering the model's pose.
There are also a few other graphical tools that can assist the development process, which we will cover over the course of this tutorial.
Try this now, and you should see two orange cylinders that look like a single cylinder due to their proximity. At this point, we have a Velodyne model that lacks dynamic properties such as moments of inertia. The physics engine uses inertia information to calculate how a model will behave when forces act upon it. A model with incorrect, or no, inertia values will behave in a strange manner.
Start by visualizing the current inertia values. This will causes two purple boxes to appear. Generally, each purple box should roughly match the size of the link it is associated with.GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together.
Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community. Already on GitHub? Sign in to your account. In my simulated robot, a laser scanner is mounted in front of the base and is called with the code. Unfortunately this cause problems with other packages that expect to see the full resolved name. Partly solved. While this is not a bug, I guess it would be wonderful to have some kind to standard AND to describe this behavior in the documentation.
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