A Study On The Cooperative Scheduling Of Static And Dynamic Segments Of FlexRay

With the increasing level of national economy,requirements on automobile safety and comfort have been promoted more and more,which urges automakers to develop all kinds of new functions to meet the needs.New technologies and functions propose more requirements considering the real characteristics of automobile network.Existing vehicle network protocols,such as Local Interconnect Network(LIN)and the Controller Area Network(CAN),cannot well meet the requirements.While the new devise FlexRay,for its high excellent performance of bandwidth,timing and fault-tolerance,can meet the requirements by the new generation of vehicle network,which has become the focus in academic circles.In terms of how to more effectively use FlexRay bus,the core is message scheduling and coordination.The existing scheduling strategy for both static and dynamic segment of FlexRay is scheduled in isolation,it will lead to two questions:1,FlexRay static period using time-division multiplex mechanisms to ensure that the feature of periodic real-time message transmission can lead to static idle time slot abound,it reduces the bandwidth utilization of the system.2,the dynamic segment is dynamically allocated time slot length,which may lead to low priority message cannot get all the time because the system resource and discarded,thus reducing the real-time and stability of the system.In order to solve the above problems,disadvantages of isolated scheduling in both static and dynamic segment of FlexRay were analyzed in detail in this paper,by which,collaborative scheduling strategy of static and dynamic segments is proposed.On the basis of FlexRay parameter optimization,message which cannot be transmitted in dynamic segment can be rescheduled in the static segment of idle time.And then a simulation system is designed by programming.Collaborative scheduling strategy of static and dynamic segments,based on the SAE message set and extension set,would be put forward and checked for its effectiveness in this paper.Experiments show that,compared with two existing message scheduling strategies,Collaborative scheduling strategy of static and dynamic segments in FlexRay can further enhance bandwidth utilization and decline message transmission delay.