改进的非抢优M/G/1CAN总线实时性分析

Analysis on Real-time Performance of CAN Bus with Improved Non-preemptive M/G/1Model

本文以CAN总线应用于牵引设备安全状态监测为例,着重研究消息的实时性。针对目前采用最长响应时间模型分析消息实时性时存在较大误差的问题和总线中消息与其优先级一一对应的特点,提出改进的非抢优M/G/1模型,以此研究总线负载率、排队长度、消息排队时延和响应时间等消息实时性指标。将最长响应时间模型与改进模型的消息实时性分析结果同基于着色Petri网的仿真结果相比,改进模型的分析结果远优于最长响应时间模型的分析结果,且与仿真结果相吻合。从而说明改进模型用于消息实时性分析的可行性和有效性。

Taking the CAN bus applied in monitoring of the traction gear safety state for example, this paper mainly studied real-time performance of messages. In view that the longest response-time analysis currently a- dopted to evaluate the real-time performance of messages generates great errors and each of the messages is of one-to-one correspondence to its priority, the improved non-preemptive M/G/1 model was put forward to study the real-time indexes of messages such as the bus load rate, queueing length, queueing delay and response time. Comparing the longest response-time model and improved non-preemptive M/G/1 model with the simulation re- sults of the Colored Petri Nets （CPN）, the improved model was found to be much superior to the longest model in analyzing the real-time performance of messages, and the analysis results of the improved model agreed well with the simulation results. Therefore, the improved non-preemptive M/G/1 model is proved feasible and ef- fective in analyzing real-time performance of messages.