Developing Mixed-Criticality Real-Time Systems: Analysis Methods and Tools

实时嵌入式计算系统监视并经常控制与物理世界交互的工件或其他系统。此类系统的例子包括航空电子系统、汽车系统和医疗机器人。这种实时嵌入式系统对安全至关重要；它们的失效可能会对人类或环境造成危害。******我提出的方案的首要主题是避免或限制实时嵌入式计算系统的故障。失败可能是以下原因造成的：****设计和实现失败（在硬件和软件层）；****操作硬件/组件故障；****资源分配问题，当系统无法在时间限制或截止日期内响应时，表现为时间错误。******我特别打算在调度和时间相关问题以及硬件组件故障的检测、诊断和恢复方面推进最先进的技术。我还将在近似计算的基础上进行工作，以便在满足时间限制更为关键的情况下权衡输出质量。******我的工作考虑了影响实时嵌入式系统开发的一些不同压力，例如计算平台对减小尺寸、重量和功耗（有时称为SWaP约束）的需求。这些压力导致在同一硬件平台上托管不同关键的计算活动（例如，在无人机上，拍摄照片的任务不如负责飞机稳定性的任务重要）。这样的设计导致混合临界系统。然而，安全关键系统需要满足IEEE 26262等安全标准中强调的要求。这些标准支持安全认证，并指出在不同临界级别上任务的可接受故障率。******最近在混合临界实时调度领域的大部分工作都集中在双临界系统上。任务要么是高临界任务，要么是低临界任务，大多数现有工作都将低临界任务视为尽力而为的任务。换句话说，在之前的工作中，研究人员已经确保高关键任务在截止日期前完成，而低关键任务即使在没有必要的情况下也会被放弃。先前工作中采用的方法也不符合安全标准，该标准指示每个临界级别的失效概率或故障率（因此，高临界任务有可能失败，但与低临界任务的失败率不同）。******通过这笔拨款，我打算开发易于处理的概率分析方法以及实时混合临界系统的运行时支持。在容错领域，已经有了一些检查混合临界系统的工作，但在平台和分析方法方面需要做更多的工作，以确保符合安全标准和认证流程。

Real-time embedded computing systems monitor and, often, control artifacts or other systems that interact with the physical world. Examples of such systems include avionics systems, automotive systems and medical robotics. Such real-time embedded systems are safety critical; their failure may result in harm to people or their environment. ******The overarching theme of my proposed program is to avoid, or limit, failures of real-time embedded computing systems. Failures may be a result of:**** design and implementation failures (at both the hardware and software layers);**** operational hardware/component failures;**** resource allocation problems that manifest as timing errors when the system is not able to respond within timing bounds or deadlines.******I specifically intend to advance the state of the art in scheduling and timing-related problems as well as with detection, diagnosis and recovery from hardware component failures. I will also build upon work in approximate computing to make output quality tradeoffs when it is more critical to meet timing constraints.******My effort takes into consideration some of the different pressures that influence the development of real-time embedded systems such as the need for reduced size, weight and power consumption (sometimes called SWaP constraints) of the computing platforms. These pressures result in the colocation of computing activities of different criticalities on the same hardware platform (e.g., on a UAV, a task that takes photographs is less critical than the task that is responsible for aircraft stability). Such designs result in mixed-criticality systems. Nevertheless, safety critical systems need to meet the requirements highlighted in safety standards such as IEEE 26262. These standards enable safety certification, and they indicate the acceptable failure rates for tasks at different criticality levels.******Much of the recent work in the area of mixed-criticality real-time scheduling has focused on dual criticality systems. Tasks are either high or low criticality, and most existing work treats low criticality tasks as best-effort tasks. In other words, in prior work, researchers have ensured that high-criticality tasks meet their deadlines and low-criticality tasks are dropped even when this is not necessary. The approach taken in prior work does not also match with safety standards which indicate a failure probability or failure rate for each criticality level (so it is possible for a high-criticality task to fail, but not at the same rate as a low-criticality task). ******Via this grant, I intend to develop tractable probabilistic analysis methods as well runtime support for real-time mixed-criticality systems. In the area of fault tolerance, there has been some work that examines mixed criticality systems, but more work is needed in terms of platforms and analysis methods to ensure compliance with safety standards and certification processes.