基于CAN的网络控制系统消息等待时间研究

Research on Message Waiting Time of CAN-Based Networked Control Systems

网络时延的不确定性是网络控制系统(NCS)分析与设计面临的首要问题,目前多采用试验统计法进行研究,但该方法无法用于NCS早期设计。文中借鉴实时系统任务调度理论,针对基于CAN的NCS,采用理论分析法,对网络时延动态变化的主体-消息等待时间进行研究。首先,明确了基于CAN的NCS消息等待时间研究是一种固定优先级的非抢占式调度问题,并给出相应的模型描述;接着,对NCS关注的消息最差情况等待时间,分别确定了连续调度和离散调度两类计算公式;最后,通过具体算例,分析和对比了两类公式的优缺点。研究表明,理论分析法简单、可行,可用于NCS早期设计,为后续设计提供有益指导。

The uncertainty of time delay is the first problem in analysis and design of Networked Control Systems （ NCS）, now the test statistic method is usually used to study it, but the method can not be applied to the earlier design of NCS. In this thesis, according to the theory of real time system task scheduling, aimed at CAN - based NCS, a theoretical method is used to study the main part of the dynamic change of network time delay - message waiting time. Firstly, it is claimed that research on message waiting time of CAN - based NCS is a kind of fixed - priority non -preemptive scheduling, and the scheduling model is described. Secondly, the formulae of continuous scheduling and discrete scheduling for the worst - case message waiting time of CAN - based NCS are given. Finally, advantages and disadvantages of both formulae are analyzed and compared. The simulation result shows the theoretical method is simple and feasible and can be applied to the earlier design of NCS and it can supply the instruction for the later design.