Scheduling Algorithm For FlexRay And Application Research Of Flexray In The Brake-by-wire System

With the development of automotive technology,the future automobile will develop for the X-by-wire system.The traditional mechanical system will be replaced by a electrical system.The electrical system will improve automobile comfort and safety.The X-by-wire system needs high bandwidth?high real-time?high transmission rate bus.The traditional CAN bus can't satisfy the communication requirement of the system.The FlexRay is developed for the X-by-wire system.It is the time triggered bus,which has broad prospects.So,this paper main research the scheduling and the using methods of the FlexRay in the brake-by-wire system.The research will be conducted as following:Firstly,the FlexRay protocol specification is analyzed in this paper.A formula is sumed up to calculate the length of static and dynamic slot.On the base of that,with the target of improving the bandwidth utilization rate in static segment,the signal packing algorithm of the static segment is put forward.This method can solve the signal packing model fastly.Then,the reliability of the message is analyzed,and a message retransmission modle based on the message priority is designed.Finnal,in this paper the time feature of the dynamic is analyzed and a scheduling modle of the dynamic segment based on the worst response time is proposed.Secondly,the principle and function of the Break-by-wire(BBW)system is analyzed in this paper.The hardware framework of the system,the task of all ECU and the bus signal are designed.Then,use the method in this paper to optimize the static and dynamic segment parameters of the Break-by-wire system.The message reliability of the static segment is analyzed and the message retransmission is usesd to achieve the system reliability requirement.Finnal,on the base of optimization parameters,the communction parameters of the Break-by-wire system are designed.Thirdly,the hardware and software modules of the BBW system are designed in this paper.The function of each hardware modules and the software architecture are analyzed.Then,the designed software for the FlexRay node is introduced,including calculating the CRC,designing the software initialization process and message receive and send process,which ensure the messages could be sent and received correctly.Finally,the communication testing platform of BBW system based on CANoe software is built.Simulat and test the BBW system using virtual and real system.Trace and analyze the bus signal using the CANoe software.Test result show that the message of BBW system is sended and received in accordance with the specified time.There are not any error frames and missing frames during the specified time.So,this designed system satifies the high reliability and real-time requirement of the BBW system under laboratory conditions.