Research On Multi-node Communication Technology Of Servo Elastic Test System Based On DDS

Servo elastic experiment must be done before flight test of aircraft.The necessity of simulation experiment is analyzed based on the principle of servo elastic experiment.In the process of building the distributed servo elastic experiment simulation system,the problem of network communication between distributed nodes is solved.The main research contents are as follows:The experimental principle of servo elastic experiment is studied.The structure of distributed experiment system is built according to the experimental principle.The nodes of the simulation experiment system are analyzed.Compared with several common network communication models,Data Distribution Service(DDS)based on publishsubscribe model is used to provide a publish-subscribe communication relationship to the application layer.It can reduce the coupling between communication nodes and improve the scalability of the system.The distributed system publish-subscribe network communication is studied.The theory of Data Distribution Service is studied,including transmission layer mechanism and communication reliability.The virtual bus module of simulation test system is designed to provide unified data interface for application layer nodes.In order to monitor and analyze each data flow,the timestamp is made in the virtual bus packet.Analyzing the receiving and processing methods of multi-source data,and introducing the weight and partition processing methods.Used the intra-domain partition method to realize the partition publish and subscribe under the same data topic,which makes the system structure stably and simply from closed-loop simulation to open-loop experiment,and finally switch to closed-loop.According to the different data processing mechanism of the system nodes,the sending timing sequence of each node and the monitoring module of data timing flow are designed.The insufficiency of Data Distribution Service application is analyzed.Clock synchronization among distributed system nodes is studied.The synchronous message mechanism used is introduced.In order to avoid the frequent modification of the local clock of the node during clock calibration,a virtual clock model with the timing mechanism of propulsion is adopted.PTP clock synchronization model is improved and implemented without hardware clock.The synchronization process is divided into zero pair time and periodic time.The synchronization accuracy is guaranteed and the consumption of synchronization is reduced.Simulation tool OMNET++ is used to build the simulation environment.The algorithm is simulated to compare the synchronization performance.The clock model is deployed in a multi-node physical environment to test the accuracy of synchronization.In the process of building the distributed simulation system of servo elasticity test,the network communication problem of the distributed system is studied.According to the specific requirements of the test system,the engineering application design is carried out to improve the flexibility of the system network communication.The clock synchronization mechanism of distributed system is designed to meet the requirement of synchronization accuracy of test system.