Event-based safety and reliability analysis integration in model-based space mission design

Abstraction

Model-based safety and reliability (S&R) analysis, which improves analysis accuracy and reduces cost and development time is applied in various industries. With the developments in model-based systems engineering (MBSE) and the use of systems modelling language (SysML), S&R analysis based on SysML models is gaining more attention. However, the emerging methods are inadequate for complex space missions. Thus, the main objective of this study involves integrating S&R analysis in SysML-based space mission design. First, a framework for integrating S&R analysis in model-based space mission design is presented. Based on the characteristics of the development of complex space missions and the MBSE process, a multisystem collaborative failure analysis method is proposed to comprehensively identify the failure modes (FMs) of the entire system. Subsequently, an event-based analysis method integrating the process of functional architecture definition is proposed, which fills the identified gaps in model-based S&R analysis for mission-level systems. Based on the identified FMs and proposed criterion, the event tree can be mapped from the SysML activity diagram. Finally, the proposed methodology is applied to a case study of a complex space mission in the near future: the manned mission to the Moon.

Introduction

介绍部分和相关工作混在一起讲的，提到了一些过去的基于SysML的安全分析工作。本文的三个贡献：

  • A multisystem collaborative failure analysis method is proposed based on the characteristics of the development of complex space missions and the process of SysML-based system design. The failures or FMs of the system defined by RAAML can be identified while the functions or structures of the system are designed, and thus, the failure analysis of the entire system can be completed through iterations and interactions of the models among systems.
  • We integrate the event-based analysis method into the functional architecture definition of the system to complete the S&R analysis of the mission-level system. Utilising the proposed mapping method, the event tree established in the parametric diagram can be extracted and transformed from the AD. Each FM in the event tree is also a top-level FM for the FTA of the underlying system, such as the component-level system.
  • We employ one of the most complex space missions—manned missions to the moon—as an example to showcase the application of the proposed model-based S&R analysis method.

Methodology and modelling language overview

七步法

分两部分介绍方法和语言。方法参考了[SafeSysE: a safety analysis integration in systems engineering approach.]这篇文章，分为七个步骤，其中第六步是第三节中提到的多系统故障分析方法，第七步根据故障识别期间构建的故障传播关系的安全性和可靠性分析，采用基于事件的分析方法在第四节中介绍。建模语言使用的是扩展自UML和SysML的RAAML，还针对空间任务缓解措施增加了一个measure的模块和SucessRate的值，描述缓解措施的成功率。

Multi-system collaborative failure analysis method

This section proposes a failure analysis method that relies on the processes of SysML-based systems engineering and RAAML.

多系统故障分析过程

如图所示，高层的基本故障和底层的故障效果是对应的，一个故障事件的发生会在总体和自己系统之间通过这个树结构传递。对于整个流程来说：

  • 1、首先进行系统设计，确定空间任务的各个阶段和系统；
  • 2、在整个系统和所有子系统中进行FTA并为已经识别的FMs进行建模；
  • 3、从整体系统和每个子系统的基础层中识别FM，对每个FM建立一个FMEA项目；
  • 4、针对单个系统进行故障分析的迭代，每次得到新的FM就进行一圈分析传播；
  • 5、对所有系统的故障分析迭代，确保一致性；
  • 6、将缓解措施整合到FMEA项目中。

Event-based safety and reliability analysis using SysML

三种故障-事件模式

将FTA集成到系统工程的方法不适合对任务级的S&R分析。空间任务通常在连续多个阶段完成，功能分解也应该依次完成。故障事件的传播分为三个基本类型，如图所示。通过建立一个“故障-事件”图，可以根据故障概率计算对应事件的发生概率。

事件树与SysML实现

Cases study

对载人登月的18个环节进行流程建模画活动图，进行故障识别和迭代分析（建立FTA和FMEA）画架构图，然后进行S&R分析画事件树进行计算，每个环节都是一个1x7的向量（概率之和为1）。最后对案例进行了有效性讨论。

个人总结：501的论文，第一个顶刊用RAAML的，论文整体使用的是MagicDraw的SysML建模，流程比较规范，RAAML的涉及略浅，多系统的故障模型建模值得参考，实验案例介绍得比较潦草，只给了一个结果，讨论也不清楚。整体上偏工程的一篇论文，技术创新不多，能中更多也是因为背景够硬吧，是值得读的。