CAN总线实时性分析

Real-time Analysis of CAN Bus

为了优化CAN通讯协议的实时性,通常有两类方法。第一类是在原有CAN事件触发协议的基础上对总线仲裁方式做一些改进;第二类是采用时间触发的TTCAN协议。本文搭建了实验平台,对不同网络负载和不同类型消息帧下的通讯延迟时间进行了实验,比较了第一类方法中的动态优先级与第二类方法中的TTCAN的网络实时性能。结果表明:负载率较大、较高时,不同类型的消息帧对消息帧的延迟时间影响较大。若采用动态优先级,事件型消息帧的延迟时间基本不变,周期型消息帧的延迟时间显著增加;若如采用TTCAN,事件型消息帧的延迟时间显著增加,周期型消息帧的延迟时间基本不变。

There are generally two methods to optimize the real-time performance of CAN protocol.One is optimizing the mode of network bus arbitrage,another is adopting TTCAN protocol.This paper construct emulational mode in order to evaluate the influences of different load and different message,compare dynamic priority with response time of TTCAN.The results show that for heavy bus load,of message has a strong impact on real time performance of message.In this instance,response time of dynamic priority event messages is approximately,and response time of period message is distinctly increased; response time of TYCAN event messages is increased, and response time of period message is roughly invariable.