The Experts below are selected from a list of 147 Experts worldwide ranked by ideXlab platform
Kang G. Shin - One of the best experts on this subject based on the ideXlab platform.
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Development and use of a new task model for cyber-Physical systems: A real-time scheduling perspective
Journal of Systems and Software, 2017Co-Authors: Jinkyu Lee, Kang G. ShinAbstract:Abstract In a typical cyber-Physical system (CPS), the cyber/computation Subsystem controls the Physical Subsystem, and therefore the computer society has recently paid considerable attention to CPS research. To keep such a CPS stable, feedback control with periodic computation tasks has been widely used, and its theoretical guarantee of stability has been made with periodic real-time task models that enforce strict periodic control updates. However, some control update misses are usually allowed (e.g., via system over-design) in certain Physical Subsystem states (PSSes) without causing system instability, and the resources required for strict periodic control updates can thus be reduced or used for other purposes, achieving efficient controls for the entire CPS in terms of the operational cost, such as fuel consumption or tracking accuracy. In this paper, we propose a new periodic, fault-tolerant CPS task model , which not only expresses efficiency and stability of the underlying Physical Subsystem, but also generalizes existing periodic real-time task models, by capturing a tolerable number of control update misses in different PSSes. To demonstrate the utility of this model, we develop a new scheduling mechanism that prioritizes jobs (i.e., periodic invocations) of a set of tasks not only by the nature of each task, but also by the number of consecutive prior job deadline misses. Based on its analysis in terms of stability and efficiency, we also propose a priority-assignment policy that lowers the system operation cost without compromising stability. Our in-depth analysis and simulation results show that the scheduling mechanism and its analysis, as well as the priority-assignment policy under the proposed model not only generalize the existing periodic real-time task models, but also significantly lower the system operation cost without losing stability.
Zhu Jiangfeng - One of the best experts on this subject based on the ideXlab platform.
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A unified power interface modeling method of a digital-Physical hybrid simulation platform
International Journal of Electrical Power & Energy Systems, 2019Co-Authors: Zhang Hao, Li Xingrui, Zhu JiangfengAbstract:Abstract The performances of a digital-Physical hybrid simulation (DPHS) platform are directly related to the modeling method of the power interface unit (PIU). This paper proposes a novel PIU modeling method with the aim of simultaneously improving the stability and the simulation precision of a DPHS system. The current of a so-called virtual impedance is added to the control signal of the controlled current source that represents the PIU burdened with the Physical Subsystem in the digital Subsystem, and all the existing modeling methods are unified by tuning the virtual impedance with different values. The stability of a DPHS platform adopting the unified PIU model is examined, and the feasible value region of the virtual impedance is obtained. The optimal value tuning method of the virtual impedance is proposed by further considering the simulation precision of the DPHS system. Simulations are conducted on DPHS platforms for a simple power system and a MMC-HVDC (modular multilevel converter-high voltage direct current) system; the results show that with the aid of the optimal value tuning method, the proposed unified modeling method can simultaneously improve the stability and precision of a DPHS system.
Xiyuan Peng - One of the best experts on this subject based on the ideXlab platform.
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Cross-Domain Noise Impact Evaluation for Black Box Two-Level Control CPS
ACM Transactions on Cyber-Physical Systems, 2019Co-Authors: Feng Tan, Liansheng Liu, Stefan Winter, Qixin Wang, Neeraj Suri, Yu Peng, Xue Liu, Xiyuan PengAbstract:Control Cyber-Physical Systems (CPSs) constitute a major category of CPS. In control CPSs, in addition to the well-studied noises within the Physical Subsystem, we are interested in evaluating the impact of cross-domain noise: the noise that comes from the Physical Subsystem, propagates through the cyber Subsystem, and goes back to the Physical Subsystem. Impact of cross-domain noise is hard to evaluate when the cyber Subsystem is a black box, which cannot be explicitly modeled. To address this challenge, this article focuses on the two-level control CPS, a widely adopted control CPS architecture, and proposes an emulation based evaluation methodology framework. The framework uses hybrid model reachability to quantify the cross-domain noise impact, and exploits Lyapunov stability theories to reduce the evaluation benchmark size. We validated the effectiveness and efficiency of our proposed framework on a representative control CPS testbed. Particularly, 24.1% of evaluation effort is saved using the proposed benchmark shrinking technology.
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ICCPS - WiP Abstract: A Framework on Profiling Cross-Domain Noise Propagation in Control CPS
2014 ACM IEEE International Conference on Cyber-Physical Systems (ICCPS), 2014Co-Authors: Feng Tan, Liansheng Liu, Stefan Winter, Qixin Wang, Neeraj Suri, Yu Peng, Xue Liu, Xiyuan PengAbstract:Control Cyber-Physical Systems (CPS) is a major category of CPS. In control CPS, besides the well-studied noises within the Physical control Subsystem, we are particularly interested in better understanding cross-domain noises: those come from the “Physical” control Subsystem, propagate through the “cyber” computing Subsystem, and go back to the Physical Subsystem. The focus of this paper is to propose a framework to profile the propagation of cross-domain noises.
Jinkyu Lee - One of the best experts on this subject based on the ideXlab platform.
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Development and use of a new task model for cyber-Physical systems: A real-time scheduling perspective
Journal of Systems and Software, 2017Co-Authors: Jinkyu Lee, Kang G. ShinAbstract:Abstract In a typical cyber-Physical system (CPS), the cyber/computation Subsystem controls the Physical Subsystem, and therefore the computer society has recently paid considerable attention to CPS research. To keep such a CPS stable, feedback control with periodic computation tasks has been widely used, and its theoretical guarantee of stability has been made with periodic real-time task models that enforce strict periodic control updates. However, some control update misses are usually allowed (e.g., via system over-design) in certain Physical Subsystem states (PSSes) without causing system instability, and the resources required for strict periodic control updates can thus be reduced or used for other purposes, achieving efficient controls for the entire CPS in terms of the operational cost, such as fuel consumption or tracking accuracy. In this paper, we propose a new periodic, fault-tolerant CPS task model , which not only expresses efficiency and stability of the underlying Physical Subsystem, but also generalizes existing periodic real-time task models, by capturing a tolerable number of control update misses in different PSSes. To demonstrate the utility of this model, we develop a new scheduling mechanism that prioritizes jobs (i.e., periodic invocations) of a set of tasks not only by the nature of each task, but also by the number of consecutive prior job deadline misses. Based on its analysis in terms of stability and efficiency, we also propose a priority-assignment policy that lowers the system operation cost without compromising stability. Our in-depth analysis and simulation results show that the scheduling mechanism and its analysis, as well as the priority-assignment policy under the proposed model not only generalize the existing periodic real-time task models, but also significantly lower the system operation cost without losing stability.
Fan Yuanzhe - One of the best experts on this subject based on the ideXlab platform.
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Real-Time Interface Model Investigation for MCFC-MGT HILS Hybrid Power System
Energies, 2019Co-Authors: Chen Yang, Kangjie Deng, Yao Kai, Fan YuanzheAbstract:The research on the control strategy and dynamic characteristics of the Molten Carbonate Fuel Cell-Micro Gas Turbine (MCFC-MGT) hybrid power system has received much attention. The use of the Hardware-In-the-Loop Simulation (HILS) method to study the MCFC-MGT hybrid power system, where the MCFC is the model Subsystem and the MGT is the Physical Subsystem, is an effective means to save development cost and time. The difficulty with developing the MCFC-MGT HILS system is the transfer of the mass, energy, and momentum between the Physical Subsystem and the model Subsystem. Hence, a new Simulation–Stimulation (Sim–Stim) interface model of the MCFC-MGT HILS hybrid power system to achieve a consistent mass, energy, and momentum with the prototype system of the MCFC-MGT hybrid power system is proposed. In order to validate the Sim–Stim interface model before application in an actual system, both a real-time model of the MCFC-MGT hybrid power system and the MCFC-MGT HILS hybrid power system based on the Sim–Stim interface model were developed in the Advanced PROcess Simulation (APROS) platform. The step-up and step-down of the current density, which were strict for the Sim–Stim interface model, were studied in these two models. The results demonstrated that the Sim–Stim interface model developed for the MCFC-MGT HILS hybrid power system is rapid and reasonable.