The Simplex Reference Model: Limiting Fault-Propagation Due to Unreliable Components in Cyber-Physical System Architectures

Ji, Weixing; Shi, Feng; Qiao, Baojun; Zuo, Qi; Liu, Caixia

doi:10.1109/rtss.2007.34

Cited by 56 publications

(34 citation statements)

References 10 publications

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“…This is also consistent with current trends in cyber-physical systems to utilize stock Ethernet networks with TCP/IP enhanced by soft real-time models for different QoS notions, such as the simplex model [4], [1]. The purely periodic model is subject to future work as it requires special hardware and protocols, such as static routing and TDMA to avoid congestion, to guarantee constant network delay.…”

Section: B the Pattern Of Requests And Jobssupporting

confidence: 73%

“…As a result, the total response time of job J is the time to wait for the next receiving job at ν p+1 , which puts J into the aperiodic queue, and the time to execute aperiodic the job workload LW (ν p ) + E(t − ν p ) + C m , which is W (p+1, HLW +E(t)−A p +C m ), after the (p+1) th receiving job. The response time of J is expressed in Equation 4.…”

Section: A Job Response Time On a Single Nodementioning

confidence: 99%

“…Stochastic approaches may break with traditional views of realtime systems. However, cyber-physical systems rely on stock Ethernet networks with enhanced TCP/IP so that soft real-time models for different QoS notions, such as simplex models [4], [1], are warranted.…”

Section: Introductionmentioning

confidence: 99%

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A real-time distributed hash table

Qian

Mueller

Xin

2014

2014 IEEE 20th International Conference on Embedded and Real-Time Computing Systems and Applications

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Abstract-Currently, the North American power grid uses a centralized system to monitor and control wide-area power grid states. This centralized architecture is becoming a bottleneck as large numbers of wind and photo-voltaic (PV) generation sources require real-time monitoring and actuation to ensure sustained reliability. We have designed and implemented a distributed storage system, a real-time distributed hash table (DHT), to store and retrieve this monitoring data as a real-time service to an upper layer decentralized control system. Our real-time DHT utilizes the DHT algorithm Chord in a cyclic executive to schedule data-lookup jobs on distributed storage nodes. We formally define the pattern of the workload on our real-time DHT and use queuing theory to stochastically derive the time bound for response times of these lookup requests. We also define the quality of service (QoS) metrics of our real-time DHT as the probability that deadlines of requests can be met. We use the stochastic model to derive the QoS. An experimental evaluation on distributed nodes shows that our model is well suited to provide time bounds for requests following typical workload patterns and that a prioritized extension can increase the probability of meeting deadlines for subsequent requests.

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Section: B the Pattern Of Requests And Jobssupporting

confidence: 73%

Section: A Job Response Time On a Single Nodementioning

confidence: 99%

See 1 more Smart Citation

A real-time distributed hash table

Qian

Mueller

Xin

2014

2014 IEEE 20th International Conference on Embedded and Real-Time Computing Systems and Applications

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“…One way to deal with complex systems in a safety-critical environment is through the Simplex Architecture [1]- [4]. This architecture provides an application-level safety guarantee by "using simplicity to control complexity".…”

Section: Introductionmentioning

confidence: 99%

“…A decision module then uses the high-performance complex controller whenever possible, but will switch to the safety controller when system liveliness is jeopardized. This design has been applied to improve the safety of a diving controller [5], a fleet of remote-controlled cars [4], and a set of advanced aircraft maneuvers [6].…”

Section: Introductionmentioning

confidence: 99%

The System-Level Simplex Architecture for Improved Real-Time Embedded System Safety

Bak

Chivukula

Adekunle

et al. 2009

2009 15th IEEE Real-Time and Embedded Technology and Applications Symposium

Self Cite

111

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Embedded systems in safety-critical environments demand safety guarantees while providing many useful services that are too complex to formally verify or fully test. Existing application-level fault-tolerance methods, even if formally verified, leave the system vulnerable to errors in the realtime operating system (RTOS), middleware, and microprocessor. We introduce the System-Level Simplex Architecture, which uses hardware/software co-design to provide failoperational guarantees for both logical application-level faults, as well as faults in previously dependent layers including the RTOS and microprocessor. We also provide an end-to-end design process for the System-Level Simplex Architecture where the AADL architecture description is automatically constructed and checked and the VHDL hardware code is generated.To show the efficacy of System-Level Simplex design, we apply the approach to both a classic inverted pendulum and a cardiac pacemaker. We perform fault-injection tests on the inverted pendulum design which demonstrate robustness in spite of software controller and operating system faults. For the pacemaker, we contrast the provided safety guarantees with those of a previous-generation pacemaker.

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Sandboxing Controllers for Stochastic Cyber-Physical Systems

Zhong¹,

Caccamo²

2019

Lecture Notes in Computer Science

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Current cyber-physical systems (CPS) are expected to accomplish complex tasks. To achieve this goal, high performance, but unverified controllers (e.g. deep neural network, black-box controllers from third parties) are applied, which makes it very challenging to keep the overall CPS safe. By sandboxing these controllers, we are not only able to use them but also to enforce safety properties over the controlled physical systems at the same time. However, current available solutions for sandboxing controllers are just applicable to deterministic (a.k.a. non-stochastic) systems, possibly affected by bounded disturbances. In this paper, for the first time we propose a novel solution for sandboxing unverified complex controllers for CPS operating in noisy environments (a.k.a. stochastic CPS). Moreover, we also provide probabilistic guarantees on their safety. Here, the unverified control input is observed at each time instant and checked whether it violates the maximal tolerable probability of reaching the unsafe set. If this probability exceeds a given threshold, the unverified control input will be rejected, and the advisory input provided by the optimal safety controller will be used to maintain the probabilistic safety guarantee. The proposed approach is illustrated empirically and the results indicate that the expected safety probability is guaranteed.

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The Simplex Reference Model: Limiting Fault-Propagation Due to Unreliable Components in Cyber-Physical System Architectures

Cited by 56 publications

References 10 publications

A real-time distributed hash table

A real-time distributed hash table

The System-Level Simplex Architecture for Improved Real-Time Embedded System Safety

Sandboxing Controllers for Stochastic Cyber-Physical Systems

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