Research On The Optimization Of Communication Mechanism For In-Vehicle FlexRay

With the continuous improvement of living standards,the comfort,safety and reliability of the car are expected to be higher.More and more electronic control units are deployed on the car to improve vehicle performance and meet the needs of users.Today,the total amount of vehicle communication is large,the proportion of safety-critical data frames in vehicle communication is increasing;and the voice of X-by-Wire system used on vehicle is getting higher.Above all put forward more stringent requirements for the bandwidth of the In-vehicle network,the real-time of data transmission and the reliability of communication.In this case,the FlexRay,known as"the Next-generation In-vehicle Network",caters to the development demand of automobile industry with its high bandwidth,determinacy,flexibility and reliability.At present,the FlexRay bus has been adopted by the auxiliary network system of some advanced vehicles,it has not been used in the trunk network and X-by-Wire system of the vehicle yet.In addition to the complicated communication protocol,the reason is that FlexRay communication mechanism also needs to be optimized for the further application and some details:1)the existing communication mechanism of the FlexRay adopts a method that refusing to receive the frame when the transmission error occurs,so as to avoid the control failure caused by the transmission error and raise the fault tolerance;this approach is equivalent to a conditional active frame dropping,rather than a restoration of a frame,which will result in loss of information and can not meet the fault tolerance and reliability demands of X-by-Wire;2)the current Flexray mechanism is lack of applicable network management system,according to the network management service framework proposed by AUTOSAR specification,when nodes join the network or leave off the network caused by fault,other nodes in the network will fail to run normally.This thesis mainly optimizes the shortcomings of FlexRay communication mechanism for the further application:1)proposed a Prompt ReTransmission Mechanism based on dynamic segment,to improve the treatment for the wrong static frame and make it retransmit in the shortest possible time;2)combining with the characteristics of FlexRay communication protocol,network management based on the Automotive Open System Architecture is optimized to improve the reliability of the network control system,which improves the treatment scheme of nodes joining the network and disconnected to network due to fault.The above two optimization schemes are verified in the test system,and the optimization effect is more obvious.It will promote the application of FlexRay in the main network and X-by-Wire system.