Construction And Performance Analysis For In-Vehicle FlexRay Backbone Network

FlexRay is the development direction for next generation in-vehicle network system, the research of that has an important aspect in high speed in-vehicle network construction, design and development of x-by-wire unit and corresponding research on such control unit.FlexRay protocol has now updated to version 2.1, it has a great number of supporters from vehicle manufactures and parts providers; Network based on Flexray has been successfully used in X5 serier cars of BMW. Referring to the mature design method, a kind of FlexRay backbone network with Freescale's MCU and NXP's transceiver was built up, also the time transmition characteristic of dynamic segment and scheduling algorithm for static segment are represented, which provide powerful theoretical basis for FlexRay network design.To make this paper's structure clear and ease the analysis and discussion, the basic characteristic of FlexRay is represented in the second chapter. The protocol operation control (including frame format, media access control, clock synchronization etc) is introduced in detail, the topology of FlexRay network and its characteristic are also analysed, thus make necessary preparation for network performance analysis.The design method of backbone network is represented in the third chapter. Freescale's MC9S12XF512 is adopted as primary processing unit, and TJA1080 as FlexRay transceiver unit. In order to make compatible with other networks such as CAN, LIN, a kind of design method for CAN, LIN is also given. There is also detailed description on hardware design and software architecture. At last the feasibility was proved through experimental results.Time delay characteristic of dynamic segment is an important index for FlexRay network, how to make effective estimation for the delay and analyze factors which lead to this delay is a major problem needed to be solved. After undertaking the content of FlexRay protocol, the major factors of delay were extracted. In order to make cacaultation simple, with comparation with factors that lead to delay, a simplified model was gained. In accordance with objective function and constraint conditions, time delay estimation is transformed into a kind of integer linear programming problem. When network parameters are assigned, the comparition between estimation value and actual value shows that the estimation algorithm is feasible. The statistical characteristics (mathematical expectation and mean square deviation) of delay data are also analysied, and the conclusion that communication cycle makes great aspect in delay time is concluded.Scheduling design is significant for FlexRay static segment, which directly effect system's bandwidth. After analyzing the basic content of scheduling, transform scheduling problem into the construction of system matrix, also the work of system matrix optimization is done, by comparing with the performance index, the efficiency of this algorithm is proved.