Research And Implementation About The Message Forwarding Mechanism Of FlexRay-CAN Gateway

Automotive control field has changed seriously as the fast development of automotive electronic technology. It is moving in the direction of vehicle bus. CAN bus is the mainstream protocol of automotive network which is widely used in auto industry right now. And FlexRay bus as the second generation fieldbus will guide the direction of the entire automotive electronics control structures for many years in the future. At present, due to the high cost of the FlexRay bus and there is no need to use such high-performance vehicle bus in all units of the car system, FlexRay bus will not completely replace CAN bus within a certain period. With the purpose of improving the performance requirements such as safety, economy and comfort and meeting up with the cost constraint, this topic analyses and studies deeply of the problem about the message interaction of FlexRay-CAN gateway. This will shorten the gap of automotive electronic technology between our country and foreign countries and improve our core competitiveness.In this paper we describe the background, the significance and the research situation of FlexRay-CAN gateway. A large number of the design and implementation techniques of domestic and international gateway are collected and researched to solve the message forwarding mechanism of FlexRay-CAN gateway. With studying of the differences about data frame and the characteristics of the network between FlexRay bus and CAN bus, a method about using ISO 15765 in FlexRay networks is proposed based on the feature of TDMA (Time Division Multiple Access) and FTDMA (Flexible Time Division Multiple Access) of FlexRay. A simulation platform has been designed to verify the correctness of the method. A segmentation strategy of the diagnostic message and delay requirement that should be met in data frame transmission are obtained by analyzing the effective load and the transmission time of the data frame in static segment and dynamic segment. For the case that the FlexRay data frame does not contain the destination address, mapping the diagnostic messages to FlexRay data frames is realized by adding the address field in the effective load of the frame. In order to solve the security problems during data transmission of CAN and FlexRay with the differences about the frame format and the handling mechanism of the message, different situations are given according to the transmit/receive buffer of gateway and frame size of the data. Corresponding message handling mechanisms are given to solve the message forwarding mechanism about FlexRay-CAN gateway. Finally, the feasibility of the method is proved by Simulation Platform.Research on this topic effectively implements the hybrid transmission between FlexRay and CAN, which can increase the network bandwidth utilization more effectively and reduce the transmission delay.