Research On Worst-Case Response Time Analysis For Messages In Gateway-Interconnected Controller Area Network (CAN)

Recently,with the rapid development of industrial,scientific and economic fields,cars play an increasingly important role in everyday life as a means of transport,and people proposed higher demands about automotive electronic systems in safety,comfort and driving performance,so it resulted in the increase of complexity of the system.In order to reduce the complexity and the cost of design,a plurality of functions are integrated into an electronic control unit(ECU),and many tasks included in the same function required many ECUs to complete,which led to the dependence between different subsystems increases.And communications between different subsystems needs a gateway to be implemented.As the existing schedulability analysis for CAN messages largely confined to a single CAN network,so the introduction of the gateway brings a new challenge to the schedulability analysis for messages in gateway-interconnected CAN.In this paper,we put forward algorithms to analyze and optimize the worst-case response time of messages in gateway-interconnected CAN from the problem of worst-case response time of messages,and ensure the security and the efficient use of resources in automotive electronic system.To solve these problems,the main work is as follows:Firstly,it is analyzed that the worst-case response time of non-gateway messages whose transmission path is just its source CAN.We first analyze CAN network system model and discover that existing analysis algorithms ingored the interference of higher priority message between gateway messages which arrive at the gateway adjacently for simplifying calculation,which makes the results more pessimistic;in addition,since the need to analyze the influence of different sequence of gateway message reaching the gateway,the time complexity of adopted exhaustive algorithm is very high.To solve this problem,this paper takes the interference of the ignored higher priority messages into consideration,calculates the maximum interference caused by gateway messages in the busy period.It not only reduces data dependency between messages,but also decreases the pessimism of the results and the time complexity of algorithms because of no need to analyze the queue order of gateway messages.Secondly,a method named "divide and conquer" is adopted to analyze the worst-case response time of gateway messages whose transmission path including the source CAN,a gateway and the destination CAN,and convert the analysis of gateway messages in its destination CAN to the same situation of the analysis of non-gateway messages.Then on the basis of above,the worst-case response time analysis of gateway messages is optimized furtherly.When a gateway message is released in its destination CAN,some gateway messages which being released earlier and transmitted already would not cause interference.So the pessimism of results can be decreased by excluding this part of gateway messages which being transmitted already in the target message's destination CAN.Finally,on the basis of the simulation data and the real data provided by car manufactures,some experiments are made to compare the algorithm s proposed in this paper and the existing algorithms,and the method proposed in this paper and the optimized method are also compared at the end of the experiments.Through experiments the effectiveness of the proposed methods and higher application value are verified in this paper.