Design And Research Of Multi-channel Flexible Data-Rate Controllable Local Area Network Practical Vehicle Gateway

The on-vehicle gateway of the traditional control area network(CAN,Controller Area Network)structure is enough to simultaneously transmit more than a dozen nodes at the same time.With the addition of entertainment systems and intelligent interactive systems,the shortcomings of CAN in large data and high rate transmission are too high,and the shortcomings of insufficient bandwidth are gradually enlarged.For high-speed transmission,a variable rate control local area network(CAN-FD,CAN with Flexible Data-Rate)came into being.The variable transmission rate can be compatible with both low-speed CAN networks and higher-speed CAN expansion networks.By comparing and researching the current traditional CAN gateways,this paper designs a vehicle-mounted gateway that can support up to eight CAN-FD data transmissions,and analyzes the design principles and performance of the gateway.Firstly,this article introduces some basic principles of the onboard gateway and the working structure of the entire onboard gateway.Taking NXP 's MCU(Microcontroller Unit)MPC5744C as the core,a hardware platform is built to design a CAN-FD data transmission support.The car gateway hardware system is different from the traditional car gateway that supports up to six channels.The transmission rate is 125kbit/s?500kbit/s The data transmission rate of each channel of the multi-channel CAN-FD gateway can reach 500kbit/s?2Mbit/s,and one The maximum effective data that the frame data can carry is increased from 8 bytes to 64 bytes,which can make up for the gap in the domestic vehicle gateway.Secondly,this article conducted in-depth research and analysis on three difficulties in the software design of the entire vehicle gateway system:network management,diagnostic design,and routing delay.Among them,for the design difficulties of network management,because the existing indirect network management cannot control a specific node to sleep alone,the power consumption is large,and it is not suitable for eight-way data transmission.Therefore,this article is based on the automotive open system architecture(AUTOSAR)Network management protocol,designed a network management mode that can reduce power consumption for eight-way node management.In the normal operation mode of the gateway system with 10 modules connected,it can reduce power consumption by about 27%.For the diagnostic protocol,this paper summarizes the data transmission process of each diagnostic service and implements the functions of three main diagnostic services:secure access service,fault code service and read data service.Aiming at routing delay processing,this paper is different from the traditional CAN gateway polling routing with long delay and few processing nodes.It proposes a large data processing method that can be used for more than 90 nodes.This method first uses the dichotomy method to quickly locate Forward the message,and then prioritize each channel of data,and then establish a priority and double priority in the buffer of each channel of data.Focus on the method of querying the main node to route the message.Compared with the traditional method,in the transmission of CAN-FD data,the new method can effectively reduce the delay by at least 0.7ms,and in the transmission of CAN data,the new method can reduce the delay by at least 0.4ms,the longer the message period,the more the delay decreases.Finally,this paper studies and analyzes the performance test data of the entire vehicle gateway system.The network management is verified by taking the actual gateway work message,and the results show that the module can be accurately controlled to work normally and sleep normally,and the system power consumption is reduced;the use of a control area network open environment(CANoe,CAN open environment)test platform for diagnosis The main sub-services were verified,and the results showed that the diagnosis function was normal;a combination of piling test and message forwarding test was used to measure forwarding performance indicators:message delay and transmission efficiency.The test results show that compared with the traditional CAN gateway,the designed CAN-FD/CAN gateway node has been upgraded from more than ten nodes to more than ninety nodes.Even if the number of transmission nodes increases,the transmission efficiency is still improved by about 1%,and CAN transmits data The minimum message forwarding delay time is improved from 6?7ms to 0.9?1.2ms,and the CAN-FD message transmission delay is only 0.2?0.3ms.