Research On Performance Optimization And Evaluation Technology Of Time-Triggered Ethernet For DIMA Application

Avionics system is the brain and nerve center of aircraft,and has experienced the typical development of four generations,which are discrete structure,federal structure,integrated modular avionics(IMA),and the latest distributed integrated modular avionics(DIMA).DIMA design through distributed integrated technology,and further combining the time triggered communication and partition isolation scheduling mechanism,that greatly enhanced the integrated electronic system when performing the task of real-time,reliability,and safety.The future avionics system architecture based on network is gradually evolved into a distributed and integrated,modular universal system platform.Time-Triggered Ethernet(TTE)belongs to the airborne bus based on time-triggered architecture.Compared with the traditional airborne bus,TTE has the advantages of high reliability and safety,good compatibility and deterministic of message transmission.In the new generation integrated avionics system,using TTE as the underlying communication network of the DIMA system(i.e.TT-DIMA)represents the research direction of the future avionics system architecture.In this dissertation,the time-trigger Ethernet performance optimization and evaluation technology for DIMA application is studied.The research results of this paper have been validated in typical application scenarios such as satellite attitude control system,launch vehicle control system and ship distributed control system.It has the characteristics of high time certainty,strong real-time and high reliability.The main research content includes four aspects,including network topology optimization under TT-DIMA application constraint,clock synchronization control for TT-DIMA system,mixed safety critical mission scheduling method,flow model optimization and performance evaluation of TT-DIMA.(1)In order to allocation of network resources reasonably,the optimization technology of TT-DIMA network topology is studied.The purpose of this part is to generate a network topology structure with low architectural cost,load balance and relatively short path,so as to ensure the safety and real-time requirements of network applications.This dissertation analyses the Ethernet system model and proposes a new method of network topology optimization.The topological optimization algorithm fully considered the TTE network communication itself has the time certainty and arbitrariness of network topology.The method can make whole network topology architecture at a lower cost,the entire network of nodes and links on the load distribution more homogeneous,that can make time-triggered traffic arrangement more reasonable,provide high performance and more reliable communication environment for DIMA system.(2)Aiming at the problems of large delay,uncertainty and incompatibility caused by unsynchronization of DIMA system application,this dissertation proposes two synchronization strategies of network-level synchronization and application-level synchronization,studies and implements the clock synchronization method of DIMA system based on TTE,and reduces the end-to-end delay of system application.Firstly,the method of TTE network clock synchronization with high precision is studied in detail,and the standard TTE synchronization algorithm is realized by using FPGA.Then,the clock synchronization technology between the Vx Works653 of the partitioned operating system and the TTE communication network is further proposed to realize the high-precision time slot alignment method of the clock between the partitioned operating system and the TTE network,so that the application traffic of the system can be arranged and scheduled according to the time-triggered mode,and the end-to-end communication delay of the traffic can be effectively reduced.Finally,using the research of TTE switches and TTE node set up a set of TT-DIMA demonstration system.The experimental results show that synchronization precision between TTE nodes is less than 48 ns,synchronization precision between application of inter-partition is less than 70 ns,end-to-end application message transmission delay in the range of [7.18?s,7.22?s],delay jitter amplitude is 40 ns.The experimental results verify the correctness and effectiveness of synchronization algorithm on one hand,on the other hand also provides support for the further development of TT-DIMA products with detail data.(3)For the traffic characteristics of the DIMA system,TTE network needs to support both time trigger and event trigger traffic to improve the timeliness and stability of the system.In order to further improve the utilization of system resources,this dissertation proposes a new static scheduling table generation algorithm for time trigger traffic.The method considers the scheduling problem into a two-dimensional bin packing and optimization problem with constraints.The optimization goal is to make time to trigger the traffic scattered arrangement as far as possible,so as to get maximum number of idle time slot number,provide time resources evenly for subsequent events trigger message.Simulation results show that the proposed optimization algorithm is better than the traditional packing algorithm in scheduling effect,with significant reduction in average delay and delay jitter,and provides a more reliable and stable communication environment for DIMA system.(4)The traditional network calculus model is pessimistic in the analysis of system delay.A new traffic optimization model and performance evaluation method is proposed based on the service characteristics of DIMA system.The service curve and arrival curve of RC traffic are optimized respectively by introducing the time-triggered(TT)traffic shortage period and the rate-constrained(RC)traffic adjustment factor.The model carries out time delay analysis,and the result of time delay analysis is closer to the real network operation,which can make time-triggered traffic arrangement more reasonable and improve the utilization rate of system resources.