Research And Realization Of FlexRay-based Network System For Electronic Controllers In Steer-by-Wire Automobile

As an advanced mechatronic system, the SBW (Steer-by-Wire) system has replaced thetraditional mechanic structures of steering system with electrionic controllers and electronicwires. With the trend of the intelligentization and high-speedization of vehicles today, theSBW system can provide an important mean to improve the performance of vehicles. Ifcombined with the FlexRay bus technology characterized with high-speed, high toleranceand high safety, it can bring much more excellent performance and much brighter applicationfuture for vehicles in the future.Based on the project of National Natural Science Foundation “Research on Controlmethods and Key Technology for X-By-Wire Vehicle” and the former research work in ourgroup, the application of FlexRay bus in the SBW system has been successfully fulfilled. Inthis dissertation, schemes of FlexRay-based network architecture of electronic controllers inthe SBW system were discussed and the timing characteristics of the FlexRay network wereanalyzed theoretically in depth. Meanwhile, problems about network parametersconfiguration as well as related optimization methods were proposed. Finally, simulationwork about FlexRay network communication and hardware-in-the-loop PID controlexperiments were carried out. The detailed tasks in this dissertation are as follows:(1) Study the time characteristics of the FlexRay bus, and put forward potentialproblems of the static segment and dynamic segment of FlexRay bus as well as theoptimization methods.The time-and-event-triggered mechanism can ensure the timely delivery of critical data and rational utilization of the FlexRay bus. But unreasonable distribution of messages andconfiguration of the time parameters will result in the deterioratation of bus utilization andresponsiveness. Therefore, it is necessary to discuss about the timing characteristics ofFlexRay bus. When studying the static segment, on the basis of the proposed performancemetric of the static segment and relevant optimization indicators, the impact of theconfiguration of the slot length in the static segment on the cycle length and the timeliness ofmessage responses was discussed first as well as time consumption of sending staticmessages. Then the corresponding optimization methods of message packing and partitionfor the issues were raised. After that, the impact of message’s ID and node’s pLatestTx valueon the arrangement and responsiveness of dynamic messages was proposed. Then based onthe study of the worst-case-response-time of dynamic messages, an integer linearprogramming based configuration was put forward.(2) Realize the communication between controllers and fulfill the controller-in-the-loopcommunication simulation of the designed controller network architecture.With the high flexibility and customization of FlexRay bus, parameters which meet therequirements of real-time system can be customized based on specific performanceindicators of systems, so it has a more complex initialization process as well as datatransmission and reception process. Before the normal activation of FlexRay bus, theFlexRay module need to be initialized, therefore, the specific process of initialization,transmission and reception as well as the protocol parameter configuration methods werefairly detailed. After that, the messages task scheduling table was given, and finally thesimulation using CANoe was fulfilled and the FlexRay network configuration correctnesswas verified.(3) Proposes the distributed dual-motor network architecture of steer-by-wire systembased on the FlexRay bus, and implement the software and hardware design based onMC9S12XF512, and finally, a hardware-in-the-loop experiment is carried out.The network structure of the steer-by-wire system plays a very important role in thesecurity and reliability of system and messages transmission as well as the control efficiency. Based on the proposed dual-motor structure and the former research work in the group, thedistributed FlexRay-based network architecture of electronic controllers in the SBW systemwas proposed and the software and hardware design based on MC9S12XF512wasimplemented. Finally, on the basis of the hardware-in-the-loop experiment platformestablished, the feasibility of proposed controller distributed network architecture andFlexRay bus configuration correctness were verified.FlexRay bus is a new network standard of vehicles and its application in steer-by-wiresystem will bring much more excellent performance and higher security for vehicles. Theresearch of the FlexRay bus and its implementation in the SBW system will lay thefoundation for its application in real vehicles in the future, and provide a significant guidefor its application in other x-by-wire systems.