Research And Implementation Of Precise Clock Synchronization In Automotive CAN Network System

With people’s increasing demands for cars, more and more electroniccontrol systems are being applied to the vehicle, networking has become aninevitable trend of automotive electronics development. As CAN bus has thecharacteristics of high speed, good real-time performance, high reliability etc,it is widely used in automotive network. Meanwhile, as the automotiveelectronics is a typical safety critical real-time system, the precise clockreference is one of the key factors of automotive network system’s highreliability running. Clock synchronization plays an important role in thedistributed system, it could ensure the real-time and reliability of CANnetwork communication, so, study the precise clock synchronizationmechanism of automotive CAN network system has an important implication.This subject is supported by National Natural Science Foundation, it studiesthe design and implementation of precise clock synchronization of automotiveCAN network system. Firstly, for the synchronization in distributedautomotive network, introduce four special message frames, studies thenetwork delay of synchronization frame transmission quantitatively, themeasure method of instant deviation and network delay is given; on this basis,combine with the master clock consultation selection method based on theminimum relative instant deviation sum, a precise clock synchronizationmechanism supporting master clock selection is established. Then, study anddesign the software implementation of precise clock synchronizationmechanism based on Freescale microcontroller MC9S12XS128, includingmessage design, software architecture design and appropriate compositionmodule design. Finally, design the physical nodes and virtual nodes, constructa semi-physical simulation platform of automotive CAN network system basedon CANoe, taking the verification test. The experiment results show that thismechanism achieves a high synchronization precision and reliability, andreduces the synchronization network overhead effectively, it can meet the highreal-time requirements of today’s cars.