Ros2 topic (03): the difference between ros1 and ros2 [02]

7 summary

        Continued above ：ROS2 project （03）：ROS1 and ROS2 The difference between 【01】_

       

8 ros1 and ros2 Communication mode of

        ros2 The abolition of the ros Of Ros-master Server mode , use DDS Distributed communication of Protocol ; The following figure illustrates the differences between their communication modes .

9 Parameter service and management

9.1 ros1 Parameter server  

ros1 All parameters of are submitted to ROS-master Inside , Store globally , All nodes are accessible ; Here's the picture ：

9.2 ros2 Parameter service of  

        ros2 The parameters of are stored in a special node , Nodes requiring parameters , Can pass Topic Receive parameter information ; This means that the parameter information can be changed in real time , For example, camera hot plug ; contrary , stay Ros1 Replace camera in , Parameters need to be changed ; Therefore, it has to be stipulated “ The camera hardware of this system must be a certain model ”

 

10 Service mode

ros1 Our service is synchronous ,ros2 Services are asynchronous ; This prevents communication congestion . More flexible is , If ROS2 Also want to achieve synchronous mode , Just choose a parameter .

11action signal communication

        Action Communication is not about where to send information , It's about controlling certain actions , Like a switch 、 Opening and closing of buttons .ROS1 It is a double grip mobile phone system , and ros2 Change to 3 handshake mechanisms . As follows ：

11.1 ros1 Of action

stay ros1 in ,action Service pass Topic Realization .

11.2 ROS2 Of action service

12 Custom message

ros2 The custom message of needs to add a namespace .

  For example, compare ROS1 and ROS2 The customized message of is as follows ：

  It can be seen that , After compiling , The name of the custom message is slightly different .

13 workspace Compile path

13.1 The compilation places are workspace Underside （src On top of ）; But the compilation tools are different ：

13.2  ros-tools Different

 13.3 ros2 New functions