DDS-YYDS

Hello everyone , I'm little fish , I haven't written for a long time , I've been busy with my work recently ( At the same time, both chassis and manipulator development ), Every time I get home, I want to sleep , Just lazy and didn't write an article , As a result, I was warned by the screenshot of the fairy early in the morning , I dare not be lazy this week .

This morning, I talked with the person in charge of the company's navigation development Z I talked about the current navigation and communication architecture ,Z The current self-developed navigation architecture cannot be said to be a system , Because there is no communication middleware to support , Some time ago, Xiaoyu made ROS2, Also contacted ROS2 Of DDS middleware , So let's analyze that .

1.DDS What is it? ？

DDS, Full name Data Distribution Service ( Data distribution services ). It's the object management group (OMG) On 2003 Published in and on 2007 Distributed system standard revised in .

Through similar ROS In the form of topic publishing and subscription , At the same time, it provides rich service quality management to ensure reliability 、 persistence 、 Transmission settings, etc .

2.DDS Communication model

DDS The model is very easy to understand , We can define the data structure of the topic （ Be similar to ROS2 Interface types in ）. The example in the following figure :

• Pos： A number id Location of the car x,y

DDS Participants (Participant) Communicate by publishing and subscribing to subject data .

DDS The application layer of DDS Subscribe and publish data ,DDS Send and receive data through the transmission layer .

DDS advantage

• Release / Subscription model ： Simple decoupling , It can easily realize system decoupling

• performance ： In the release / In subscription mode , With the request / Compared with the reply mode , Less delay , Higher throughput .

• Automatic discovery of remote participants ： This mechanism is DDS One of the main functions of . The communication is anonymous 、 Decoupled , Developers don't have to worry about localization of remote participants .

• rich Qos Parameter set , Allow to adjust all aspects of communication ： reliability 、 persistence 、 redundancy 、 life 、 Transmission settings 、 resources ......

• Real time publish subscribe protocol ( RTPS )： The protocol can be implemented through almost any transmission , Allow in UDP、TCP、 Used in shared memory and user transfer DDS, And realize different DDS Achieve true interoperability between .

3.FastDDS

eProsima Fast DDS yes DDS（ Data distribution services ） canonical C++ Realization . The feature is open source .

Tomorrow Xiaoyu will take you to install and experience DDS

Reference material ：

• white paper :https://www.eprosima.com/index.php/resources-all/whitepapers/dds

• DDS-Docker:https://www.eprosima.com/index.php/component/ars/repository/eprosima-dds-suite/eprosima-dds-suite-1-0-0/ubuntu-eprosima-dds-suite-v1-0-0-tar