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Unlike standalone embedded devices, behaviors of a cyber-physical system (CPS) are highly dynamic. Many parameter values (e.g., those related to nature environment and third party black box functions) are unknown offline. Furthermore, distributed sub-CPSs may exchange data online. In this article, we first propose the concept of parametric hybrid automata (PHA) to describe such complex CPSs. As some PHA parameter values are unknown until runtime, conventional offline model checking is infeasible. Instead, we propose to carry out PHA model checking online, as a fault prediction mechanism. However, this usage is challenged by the high time cost of state reachability verification, which is the conventional focus of model checking. To address this challenge, we propose that the model checking shall focus on online scenario reachability validation instead. Furthermore, we propose a mechanism to compose/decompose scenarios. Our scenario reachability validation can exploit linear programming to achieve polynomial time cost. Evaluations on a state-of-the-art train control system show that our approach can cut online model checking time cost from over 1 h to within 200 ms. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Hybrid systems model checking is a great success in guaranteeing the safety of computerized control cyber-physical systems (CPS). However, when applying hybrid systems model checking to Medical Device Plug-and-Play (MDPnP) CPS, we encounter two challenges due to the complexity of human body: 1) there are no good offline differential equation-based models for many human body parameters; 2) the complexity of human body can result in many variables, complicating the system model. In an attempt to address the challenges, we propose to alter the traditional approach of offline hybrid systems model checking of time-unbounded (i.e., infinite horizon, a.k.a., long run) future behavior to online hybrid systems model checking of time-bounded (i.e., finite horizon, a.k.a., short run) future behavior. According to this proposal, online model checking runs as a real-time task to prevent faults. To meet the real-time requirements, certain design patterns must be followed, which brings up the codesign issue. We propose two sets of system codesign patterns for hard real time and soft real time, respectively. To evaluate our proposals, a case study on laser tracheotomy MDPnP is carried out. The study shows the necessity of online model checking. Furthermore, test results based on real-world human subject trace show the feasibility and effectiveness of our proposed codesign. [ABSTRACT FROM AUTHOR]