Research And Implementation Of ROS2-compatible Message Middleware For Internet Of Things

After decades of development,robot technology has been widely used in production and life.In recent years,with the rise of Internet of Things technology,the combination of robot and Internet of Things has become a hot research topic.As the second-generation product of ROS,ROS2(Robot Operating System)adopts the publish/subscribe communication model based on DDS(Data Distribution Service)architecture to achieve complete decentralization.At present,the communication between ROS2 system and the Internet of Things system generally adopts the transplanting scheme and the bridging scheme.The transplanting scheme is to transplant ROS2 system to different embedded software and hardware platforms,but it has a strong dependence on the operating system,and DDS architecture also has certain requirements on hardware performance,so the transplanting scheme cannot meet the requirements of new application scenarios.The bridging scheme uses bridging software to convert ROS2 messages into Internet of Things protocol messages.However,the current bridging scheme has some shortcomings in communication delay,memory and CPU usage,and will destroy the distributed characteristics of DDS architecture.This thesis investigates the mainstream communication schemes between the existing ROS2 system and the Internet of Things system,and analyzes the shortcomings of the communication model of bridging schemes.By integrating client-agent mechanism of XRCE DDS(DDS for eXtremely Resource Constrained Environments)protocol specification and message-oriented middleware technology,a communication model of message-oriented middleware based on multi-agent is proposed.This model can realize bi-directional transparent communication between XRCE client and MQTT node.Aiming at the load balancing of XRCE agent,this thesis designs a load balancing strategy and algorithm suitable for the above communication model.At the same time,this thesis proposes a ROS2 support and extension mode for XRCE DDS protocol,and implements ROS2 node that supports XRCE DDS protocol.Finally,according to the research results of communication model,ROS2compatible message middleware of Internet of Things is designed and implemented.After the actual deployment test,the message middleware designed and implemented in this thesis can support XRCE ROS2 node in upper computer to connect to XRCE agent,and carry out two-way transparent communication with MQTT node in the embedded environment.The stability reaches the expected effect.In terms of communication delay,memory and CPU resource occupation,Compared with the existing double bridging schemes,the optimization results are great.The test results show that the message middleware provides a more excellent communication scheme for ROS2 and the Internet of Things system,which has positive significance for the software ecological development of ROS2 and the combination of ROS2 and the Internet of Things technology.