Message Delay Distribution Analysis For Controller Area Network Under Errors

Supported by National Natural Science Foundation of China No.51475422, and based on the accurate cognition about fieldbus protocol, mechanism of fault tolerance, intermittent connections (IC) and the stochastic characteristics of time delay caused by errors, this dissertation proposed a method to estimate the time delay distribution of fieldbus messages under errors.Controller Area Network (CAN) is a widely used fieldbus protocol in various industrial appli-cations. Due to the harsh industrial environments and aging effects of the cables in the networked automation systems, the CAN messages response time (MRT) will be increased in the presence of bus errors, hence the performance and reliability of a CAN network will be affected by the network errors. In order to understand the network behaviors under errors for optimal design of the networked control systems, the delay time of the messages need to be analyzed. At the same time, in order to obtain the information and performance of a network system which has not been set up, the MRT of the network system needed to be predicted and estimated ahead of time. This dissertation presents a novel analysis method to estimate the MRT delay distribution for CAN networks that operating on polling communication mode. Firstly, the MRT distribution of single slave node is analyzed based on given error distribution, then the preliminary analysis result on the multiple nodes scenario is introduced by decomposing complex traffic event sequences into the single node cases. Experiments are conducted to demonstrate the proposed the method, and the results show that the MRT distributions obtained by using proposed method agree well with the actual observations.This dissertation is organized as follows.In Chapter 1, the research background as well as the domestic and overseas state of the art about MRT of CAN messages is described in detail, from this the problem which still requires for further study about MRT and its realistic significance of the research is summarized, and then the research objectives, study contents and overall research methods are explained systematically.In Chapter 2, some delay cases on the bus are briefly introduced, and the kernel message delay problem this dissertation considered which caused by both other messages’blocking time and error interruptions is proposed. On this basis, the delay problem is defined and some assumptions and constraints are put forward. Finally the overall scheme and steps are proposed systematically.In Chapter 3, the single node case is analysed since the delay time in the single node case is only cause by error interruptions. Firstly the stochastic IC faults model is established and then the probability that the error interruption events can be caused by IC faults in different sections of a message is analysed in detail. At last the delay distribution of single node case is obtained considered different number of error interruptions occurred on the bus.In Chapter 4, the delay cases of multiple nodes is analysed, which considered both error interruptions and blocking time by other messages. Three different analysis modes is established on the basis of delay distribution analysis on a few slave nodes. And then the method to analyse multiple nodes’ delay distribution is proposed.In Chapter 5, experiments are conducted to demonstrate the proposed the method, firstly the information of the testbed is introduced in detail, then the experiments of single node case and multiple nodes case are carried on separately and the results show that the MRT distributions obtained by using proposed method agree well with the actual observations. Furthermore, in order to optimize the distribution results, a optimization scheme is proposed and the results show that it can make the probability distribution curve closer to the actual value.In Chapter 6, the research work is summarized as well as its scientific contributions. Future work is also presented.