Analysis And Design Of FlexRay-CAN Gateway Protocol In Automotive

As the development of the innovative and high technologies, an automotive isnever only a travel tool anymore, people are desiring an automotive to be moreeconomic, safe, comfortable and environmental friendly, and the automotiveelectronic system, determining these performances, now is the critical part of a car.The two buses of CAN and FlexRay are the de-factor buses recently and in futurerespectively, what’s more, they will be quite important buses for a car. So thetechnologies of FlexRay-CAN gateway will be the important factors driving thedevelopment of the automotive electronics. Signal mapping is an importantmechanism for an automotive gateway to achieve the function of messagetransferring, and its message packaging methods are not broadly or deeply studied yet.Surrounding FlexRay-CAN gateway, the paper analyzed the current researchstate of the field and simply introduced the relevant automotive bus technologies andthe functions of an automotive gateway at first. Then the paper detailedly discussedthe work flow of the signal mapping mechanism and the relevant problems need tosolve. Finally, the paper promoted two message packaging methods for theFlexRay-CAN gateway and a solution for FlexRay bus optimization to offset theinadequacy of a FlexRay-CAN gateway. The main work of the paper is as follow.Firstly, the paper proposed two message packaging methods: one is foroptimizing the utilization of the bus bandwidth. As the signal value changesrandomly, and if the value of a signal stays the same, then it doesn’t matter if thesignal is not transmitted, and so does for a message if the value of all the signals in itstays the same, as a result the bandwidth for the message may be not used. So we candecrease the total bus bandwidth requirement by making this type of bandwidth asmuch as possible and using it to transmit the best-effort forwarding messages; theother is for improving the utilization of the signal bits in a message, and it will put asignal with smaller period in multiple messages with bigger periods, as a result asignal with smaller period will be avoided being put in a message with bigger period,and the utilization of the signal bits will be improved. Besides, the paper discussedthe value ranges of the message period and the communication cycle of FlexRay.Secondly, the paper analyzed the influence of the messages’ size, the variable ofpLatestTx, the size of FlexRay dynamic segment on the schedulability of FlexRay dynamic segment. Then the paper gave out a solution for improving the schedulabilityof FlexRay dynamic segment, the solution improves the schedulability of the dynamicsegment by moving suitable messages from the dynamic segment to the static segmentand combining the last static slot with the dynamic segment. Besides, the paperdiscussed the worst case response time of a message in the FlexRay static segment,analyzed the influence of the solution on the worst case time of messages, and provedrelevant theories at the same time.Finally, the paper carried out some experiments to validate the efficiency of themessage packaging methods in chapter three and the optimization solution in chapterfour, and presented the analysis of the experiments’ results, it is shown that themethods worked efficiently in the experiments, but they still contain much inadequacyand need further researches.