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ISSN 2095-9184 (print), ISSN 2095-9230 (online)

A rectangle bin packing optimization approach to the signal scheduling problem in the FlexRay static segment

Abstract: As FlexRay communication protocol is extensively used in distributed real-time applications on vehicles, signal scheduling in FlexRay network becomes a critical issue to ensure the safe and efficient operation of time-critical applications. In this study, we propose a rectangle bin packing optimization approach to schedule communication signals with timing constraints into the FlexRay static segment at minimum bandwidth cost. The proposed approach, which is based on integer linear programming (ILP), supports both the slot assignment mechanisms provided by the latest version of the FlexRay specification, namely, the single sender slot multiplexing, and multiple sender slot multiplexing mechanisms. Extensive experiments on a synthetic and an automotive X-by-wire system case study demonstrate that the proposed approach has a well optimized performance.

Key words: FlexRay, Real-time applications, Rectangle bin packing, Schedule optimization, Slot multiplexing

Chinese Summary  <22> 一种解决FlexRay总线静态段信号调度问题的矩形装箱优化方法

目的:为解决大量汽车分布式实时应用的数据信号在FlexRay总线静态段的有效调度问题,提出了一种矩形装箱优化方法。该方法在满足每个通信信号时间限制的前提下,可以实现最小化FlexRay总线静态段带宽消耗。
创新点:提出了一种矩形装箱优化方法将强实时车载通信信号以最小的带宽消耗调度在FlexRay总线静态段。提出的方法具备以下三个显著优势:(1)该方法同时支持最新版FlexRay通信协议中两个时隙分配机制,包括单发送时隙复用机制及多发送时隙复用机制(截至目前该方法是第一个使用多发送时隙复用机制进行FlexRay静态段信号优化调度的研究);(2)该方法创造性地将更小粒度的信号实例作为优化调度的基本单元,允许将不同周期的信号实例调度到相同的时隙上,提高了调度的灵活性,从而大幅度增加了FlexRay静态段带宽的利用率;(3)通过应用特定领域的知识减少了方法的搜索空间,显著提高了该方法的运行效率。
方法:首先,通过举例分析了FlexRay总线单发送时隙复用机制及多发送时隙复用机制对静态段信号优化调度的重要作用(图2和3)。然后,基于整数线性规划方法,将FlexRay总线静态段的信号优化调度问题转换成一个具有诸多特殊限制的矩形装箱问题。提出的方法以最小化静态段使用的时隙的目标,以信号的时间限制、FlexRay协议中相关限制,包括信号打包的限制、单发送时隙复用机制、多发送时隙复用机制等,为约束条件。此外,应用特定领域的知识减少了整数线性规划的搜索空间,大幅度提高了该方法的运行效率。最后,通过大量基于合成信号集及一个真实线控系统信号集的试验,证明了提出的矩形装箱优化方法具有良好的性能。
结论:提出了一种解决FlexRay总线静态段信号调度问题的矩形装箱优化方法。该方法基于整数线性规划,在满足每个信号时间限制的前提下,实现了静态段带宽消耗的最小化。

关键词组:FlexRay;实时应用;矩形装箱;优化调度;时隙复用


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DOI:

10.1631/FITEE.1500232

CLC number:

TP393

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On-line Access:

2016-04-05

Received:

2015-07-21

Revision Accepted:

2015-12-14

Crosschecked:

2016-02-26

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