A Lease Based Hybrid Design Pattern for Proper-Temporal-Embedding of Wireless CPS Interlocking

Abstract

Cyber-Physical Systems (CPS) integrate discrete-time computing and continuous-time physical-world entities, which are often wirelessly interlinked. The use of wireless safety-critical CPS requires safety guarantees despite communication faults. This paper focuses on one important set of such safety rules: Proper-Temporal-Embedding (PTE), where distributed CPS entities must enter/leave risky states according to properly nested temporal pattern and certain duration spacing. Our solution introduces hybrid automata to formally describe and analyze CPS design patterns. We propose a novel leasing based design pattern, along with closed-form configuration constraints, to guarantee PTE safety rules under arbitrary wireless communication faults. We propose a formal procedure to transform the design pattern hybrid automata into specific wireless CPS designs. This procedure can effectively isolate physical world parameters from affecting the PTE safety of the resultant specific designs. We conduct two wireless CPS case studies, one on medicine and the other on control, to show that the resulted system is safe against communication failures. We also compare our approach with a polling based approach. Both approaches support PTE under arbitrary communication failures. The polling approach performs better under severely adverse wireless medium conditions; while ours performs better under benign or moderately adverse wireless medium conditions.

Fault diagnosis of a computer interlocking system for railway signal control

“…In this paper, in order to improve the accuracy of the algorithm, the PSO algorithm [14] is introduced to adjust the weight parameters. The PSO algorithm is an optimization algorithm inspired by collective behaviors observed in nature, such as bird flocks or fish schools.…”

Verification Templates for the Analysis of User Interface Software Design

“…Although, superficially, this property appears to be use-related the aim of their patterns is to facilitate the introduction of a model checker in the actual implementation of the safety interlock, rather than defining property templates for the analysis of use-related aspects of the safety interlock. Other similar work, e.g., [47]- [49], also introduce mechanisms similar to templates for the verification of safety interlocks, but the focus of them is again on translating verified design models into a concrete implementation -in [47], for example, the automatic translation of hybrid automata models of a safety interlock into a concrete implementation.…”

Verification of User Interface Software: The Example of Use-Related Safety Requirements and Programmable Medical Devices

“…Although they use the patterns to analyze use-related properties such as "When the laser scalpel emits laser, the patient's trachea oxygen level must not exceed a threshold Θ O 2 " the aim is the integration of a model checker in the actual implementation of the safety interlock as a runtime fault prevention mechanism, rather than the analysis of userelated aspects of the safety interlock. This and other similar research activities, e.g., [18]- [20], are not concerned with the analysis of use-related requirements. Proving requirements with similar characteristics to those described in this paper (though not explicitly use-related) has been the focus of a mature set of tools developed by Heitmeyer's team using SCR [21].…”