ROS 2 is newer version of ROS with different architecture. Both the networks are separate and there is no direct communication between the nodes in ROS and ROS 2. The
ros1_bridge package provides a network bridge which enables the exchange of messages between ROS and ROS 2. The bridge manages all the conversion required and sends messages across both the networks. For more information, see
ros1_bridge. This example uses a virtual machine which may be downloaded by following the instructions in Get Started with Gazebo and a Simulated TurtleBot. The
ros1_bridge package is installed on this virtual machine.
This example shows how to control the TurtleBot3 in Gazebo using keyboard commands from the MATLAB®. The Gazebo Simulator is available in ROS 1 networks only. You can use
ros1_bridge to exchange the Gazebo topics such as
'/cmd_vel' to ROS 2.
The below diagram depicts the message exchange between ROS 1 and ROS 2 networks using
'/odom' topic contains
nav_msgs/Odometry messages sent from the ROS 1 network with Gazebo. The ROS 2 node subscribes to the
/odom topic that has been bridged from ROS 1 and publishes a
'/cmd_vel' message based on the robot pose. The bridge then takes the
'/cmd_vel' message and publishes it on the ROS 1 network.
You may need to create an XML file on the VM named DEFAULT_FASTRTPS_PROFILE.xml to configure IP addresses to communicate under different subnets (see Communicate Outside Subnet section in Connect to a ROS 2 Network). In the example XML file replace <address> entries with host and VM IP addresses and replace <domainId> entry with your specified domain. Create the same file, with the same contents, on your host computer in the MATLAB current working directory.
<?xml version="1.0" encoding="UTF-8"?> <profiles> <participant profile_name="participant_win" is_default_profile="true"> <rtps> <builtin> <metatrafficUnicastLocatorList> <locator/> </metatrafficUnicastLocatorList> <domainId>25</domainId> <initialPeersList> <locator> <udpv4> <address>192.168.2.147</address> </udpv4> </locator> <locator> <udpv4> <address>192.168.2.1</address> </udpv4> </locator> </initialPeersList> </builtin> </rtps> </participant> </profiles>
On the VM desktop, click Gazebo Empty. This Gazebo world contains a Turtlebot robot, which publishes and subscribes to messages on a ROS 1 network.
Click the ROS Bridge shortcut. This bridge setups publishers and subscribers for all the ROS 1 topics on a ROS 2 network.
In the Terminal window, notice that the bridge is up and running.
Open one more terminal and enter the following commands
export ROS_DOMAIN_ID=25 source /opt/ros/dashing/setup.bash
Now check that Gazebo topics are present in ROS 2.
ros2 topic list
/odom topic to see messages being published.
ros2 topic echo /odom
In MATLAB on your host machine, set the proper domain ID for the ROS 2 network using the
'ROS_DOMAIN_ID' environment variable. The ID must be a character vector.
Create a ROS 2 node. Subscribe to the odometry topic that is bridged from ROS 1.
ros2Node = ros2node("/example_node"); handles.odomSub = ros2subscriber(ros2Node,"/odom","nav_msgs/Odometry")
handles = struct with fields: odomSub: [1×1 ros2subscriber]
Receive the odometry messages from the bridge and use the
exampleHelperGet2DPose function to unpack the message into a 2D pose. Get the start position of the robot.
odomMsg = receive(handles.odomSub); poseStart = exampleHelperGet2DPose(odomMsg)
poseStart = 1×3 0.2038 0.0140 -0.8517
handles.poses = poseStart;
Create a publisher for controlling the robot velocity. The bridge takes these messages and sends them on the ROS 1 network.
handles.velPub = ros2publisher(ros2Node,'/cmd_vel','geometry_msgs/Twist')
handles = struct with fields: odomSub: [1×1 ros2subscriber] poses: [0.2038 0.0140 -0.8517] velPub: [1×1 ros2publisher]
Run the e
xampleHelperROS2TurtleBotKeyboardControl function, which allows you to control the TurtleBot3 with the keyboard. The
handles input contains the ROS 2 subscriber, ROS 2 publisher, and poses as a structure. The function sends control commands on the ROS 2 network based on the keyboard inputs. The bridge transfers those messages to the ROS 1 network for the Gazebo simulator.
poses = exampleHelperROS2TurtleBotKeyboardControl(handles);
The figure that opens listens to keyboard inputs for controlling the robot in Gazebo. Hit the keys and watch the robot move. Press Q to exit.
Plot the results to show how TurtleBot3 moved in Gazebo. The
poses variable has stored all the updated
/odom messages that were received from the ROS 1 network.
odomMsg = receive(handles.odomSub); poseEnd = exampleHelperGet2DPose(odomMsg)
poseEnd = 1×3 0.8522 0.1618 -1.6255
poses = [poses;poseEnd]; figure plot(poses(:,1),poses(:,2),'b-', ... poseStart(1),poseStart(2),'go', ... poseEnd(1),poseEnd(2),'ro'); xlabel('X [m]'); ylabel('Y [m]'); legend('Trajectory','Start','End');
Clear the publishers and subscribers on the host.