Protocol Design And Node Development Of TTCAN-Based Control Network For Vehicles

As one of the most important developing tendencies of vehicle control system, the vehicle control system should have excellent abilities of real-time and fault-tolerance. Based on the synthetic analysis of the research actuality and development trends of vehicles control network, in this paper, a new vehicle network communication protocol based on time-triggered CAN (TTCAN) is studied in order to improve the real-time performance of CAN bus. The clock synchronization structure and the optimal method of schedule on TTCAN are studied in details, and the TTCAN-based vehicle network node is also studied.First of all, this paper introduces the actuality and standard of vehicle control network and the development of the CAN bus, analyses the disadvantage of the CAN bus and brings forward the reason of the study on TTCAN and its actuality.Due to the event triggered feature of CAN bus protocol, the message is hard to be transmitted on time when the bus load comes up to a certain degree. The TTCAN protocol studied in this paper is time triggered, and is a scheduling structure based on static schedule table. In this way, the real-time transmission of the messages under a high bus load is guaranteed. Based on the analysis of the TTCAN protocol, this paper present a combinational method of hardware and software to achieve the synchronization of TTCAN nodes.In this paper, another important research issue is the design of the total structure of the system matrix of TTCAN. By using the system matrix, messages can be transmitted in the time slots correctly. In the vehicle control network system, message transmission jitter happens because of the difference of transmission cycles between periodic messages and the uncertain transmission time of the acylic messages. Genetic Simulated Annealing Algorithm is adopted to optimize the system matrix which is in order to make the message transmission jitter minimum.Finally, in the paper, the design and research of the TTCAN-based vehicle network nodes are introduced. A implementation of a general TTCAN node is introduced. And then a monitor and display node of the vehicle control system is designed based on the Windows CE embedded OS. This display node uses the conventional CAN bus for communicating in the lower level, and resorts to software of PC, which is abundant in software resource, to realize the TTCAN protocol in the high level. The display system has a good human-machine interface as well as real-time performance.