Research On Real-time Performance Of CAN

CAN, designed as a kind of multi-line network communication system, itsapplication range is no longer limited to automotive electronics.Because of its cost-effective performance design and good reliability，it hasobvious advantage in the connection of electronic monitoring equipment used inindustry scene. Coupled with its excellent flexibility and real-time performance, CANhad been widely used in ships, industrial automation, medical equipment, electricpower system,etc.Along with the increasingly complex system control algorithm and highreal-time requirements of control network, under the heavy network load conditions,traditional fixed priority algorithm of CANbus has not been able to meet the real-timerequirements.In order to make the messages transmit effectively and accurately inCAN network, the developer should make a reasonable allocation and dispatchingstrategies to make sure the message reaches the target node in the deadline. So theresearch of real-time performance of CAN message and its scheduling algorithm notonly has profound theoretical significance, but also has extensive application value.This paper provides a probabilistic analysis of worst case response time(WCRT)of message with faults in CAN network.The response time mainly contains such a fewparts:release jitter, the worst blocking time, the worst transmission delay, theinterference caused by the messages who have higher priority.Studying about severalkinds of mainstream static scheduling algorithms and dynamic scheduling algorithm,By studying and analyzing static scheduling algorithm Deadline MonotonousScheduling(DMS) which assigns the priority fixedly to each message based on itsdeadline before starting the system and dynamic scheduling algorithm EarliestDeadline First(EDF) which assigns the priority dynamically based on its remainingdeadline in the running time of system, combining the cheap CPU cost of DMS andhigh network utilization of EDF and using the layered structure, we presented ahybrid scheduling algorithm with considering critical level of messages. Based on thework mentioned above, the simulation platform of CANbus is developed withMATLAB/SimEvents tool box. The platform was used to real-time analysis for thescheduling algorithms mentioned before, the simulation results showed that the hybridscheduling algorithm could not only improve the real-time performance of system, butalso reduce the cost of processor.Then we transplant the MicroCANopen protocol stack in μC/OS-II operatingsystem,moreover,the three kinds of real-time scheduling algorithm is implemented onStm32f107VC processor.It has turned out clearly that the performance of CANnetwork is improved after introducing the hybrid scheduling algorithm.