Youxian Sun,Xinping Guan,Jiming Chen,and Yilin Mo

Guest Editorial for Special Issue on Cyber-Physical Systems

Youxian Sun,Xinping Guan,Jiming Chen,and Yilin Mo

I.INTRODUCTION

CYBER-PHYSICAL system is a system of collaborating computational elements to control physical entities.The coordination and the tight link between computational,virtual and physical resources in cyber-physical system will have a pervasive effect on our everyday life.The development of cyber-physical system will create new opportunities for the introduction of services that will enhance the quality of life of the society as a whole.Research advances in cyber-physical systems promise to transform our world with systems that will far exceed those of today in terms of:effectiveness,adaptability,autonomicity,energy ef fi ciency,precision,reliability, safety,usability,scalability,stability and user-centric applicability.Moreover,recently the sensor web concept came into foreground,aiming at combining distributed sensing with the ubiquitous connectivity and accessibility of the web,therefore facilitating the close interaction of digital world with physical world.

The technical challenges of cyber-physical systems are signi fi cant,and of high research and practical importance,mainly stemming from the fact that traditionally different groups of scientists deal with this setting without much interaction,using disjoint sets of techniques.Towards merging the cyber and physical world,well-de fi ned analytical models,methodologies and experimental validations are required in order to build systems capable of orchestrating heterogeneous components together in a fl exible and ef fi cient way.The control systems community has been consistently engaged in the development of theories,tools,and practices for the analysis and the design of cyber-physical systems.The aim of this special issue is to provide a window into the recent developments of the fundamentals and applications of control of cyber-physical systems.

II.THEISSUE AT AGLANCE

A.Robust Algorithm Design

The uncertainties in cyber-physical systems come in various forms.The parameters of the physical system cannot be measured precisely and are subject to changes.The communication between each component of the system may be unreliable.Finally,the use of open computation and communication platform makes the system vulnerable to malicious cyber attacks.As a result,the decision and control algorithm in cyber-physical systems needs to be robust to uncertainties and provide performance guarantees.This specialissue includes three papers on robust algorithms design.The paper by Liu et al.proposes a robust data set classi fi cation approach based on neighbor searching and kernel fuzzy C-means methods,in order to reduce the impact of parameter uncertainties.To determine the number of the clusters,the proposed methodology employs techniques such as neighbor searching,controlling clustering shape and adaptive distance kernel function.The feasibility and the robustness of the approach is further illustrated by numerical experiments.Wang et al.studies another widely used algorithm,the average consensus algorithm,with an event-triggered communication scheme to reduce the communication burden.The authors further assume that the communication is unreliable,which suffers from delays and packet drops.The system is modeled as a reduced dimension hybrid system and suf fi cient conditions for the average consensus are provided,which illustrates the relationship between the parameters of the event-trigger,the communication uncertainty and the system stability.Finally,Li et al.consider designing cyber-physical system in adversarial environment,where an attacker can launch cyber-attacks on multiple communication channels.Based on frequency domain technique and auxiliary detection tools,the authors propose an algebraic detection approach to generate the residue information and then detect the attack.The authors also provide necessary and suf fi cient conditions for the detectability of the attack.The proposed approach is easy to implement in practice and numerical examples are provided to illustrate its effectiveness and feasibility.

B.Wireless Sensor and Actuator Networks

The advancement of wireless sensor networks(WSN)technology has greatly enhanced the remote and intelligent monitoring of physical systems with a fi ne granularity both in time and space.Recently,the WSN has evolved to wireless sensor and actuator networks(WSAN)in order to close the loop over the networks.Four papers that are selected address the analysis and design of WSAN.The paper by Liu et al. the topology design problem in WSN in order to balance the energy consumption and the utility of network resources.The authors proposed a distributed iterative algorithm to solve the joint optimization problem,whose convergence property is also proved analytically.The dynamic coverage problem of WSAN in underwater environment is considered by Luo et al. The network consists of both static sensor nodes and actuator nodes which can move autonomously.The authors propose a min-weighted rigid graph based topology design to reduce the communication energy consumption.On top of the topology design,a dynamic coverage strategy is developed to further improve the coverage of sensor and actuator nodes.Jin et al. study the real-time performance of the WirelessHART protocol in a network with mixed-criticality communications,where different data fl ows come with different levels of importance. The authors propose an end-to-end delay analysis approach based on fi xed priority scheduling and illustrate the effective-ness of the approach via numerical evaluations.The paper by Xia et al.consider using energy harvesting device to prolong the life time of the WSN monitoring oil pipelines.Three communication strategies,namely worst case energy balance strategy,optimization workload energy balance strategy and optimization fi rst node energy balance strategy,are proposed and a comparison of their effectiveness is studied via experimental results.

C.Power Grid

The power grid is arguably the world’s largest cyberphysical system.It is the motor of the economy and the major driver of progress of the society.Two of the papers deal with the challenges related to the power grids.The paper by Li et al.focuses on the energy optimal operation problem of the microgrids under stochastic environment introduced by the highly random unconventional energy sources.They model the uncertainty with an autoregressive moving average(ARMA) model and propose an energy scheduling optimization strategy with the goal of minimizing the expected operation cost.The effectiveness and the robustness of the proposed strategy is illustrated via simulation results.Chen and Feng present a fully distributed control architecture of the microgrids,which consists of the primary controllers,the secondary controllers and the optimal active power sharing controllers.All these controllers are implemented in each local generators to make the system fully distributed and remove the requirement of a centralized controller.The performance of the proposed distributed control architecture is analyzed and it is proved that optimal active power sharing and fi nite-time convergence are achieved.

D.Other Applications

There are many emerging applications of cyber-physical systems besides WSAN and power grids.Three papers are selected to illustrate the usage of cyber-physical systems in the area of water supply network,intelligent transportation system and pedestrian monitoring and control.Wei and Li model the water supply network as an undirected and unweighted complex network to analyze its structural properties.A community detection algorithm based on the spectral analysis of the Laplacian matrix is proposed.The authors further study the structural controllability of the network.The paper by Xiong et al.extends the cyber-physical systems framework to cyber-physical-social systems to incorporate humans in the loop.The authors introduce the cyber systems,computational experiments and parallel execution methodology for the designing,validation and realization of the systems.The intelligent transportation system is discussed as a case study for the cyber-physical-social system.Cao et al.provide a survey on the recent advancements in pedestrians modeling and control. The usage of factional calculus in pedestrians modeling has been reviewed and discussed from various perspectives.The authors further propose a cyber-physical system framework for the control of pedestrians by means of networked Segways with onboard personnels.

ACKNOWLEDGMENT

The guest editors wish to thank all the authors,for their submissions,and the large number of reviewers,who carefully and timely scrutinized and evaluated the many papers submitted.

Youxian Sun received the diploma from the Department of Chemical Engineering,Zhejiang University, Hangzhou,China,in 1964.He joined the Department of Chemical Engineering,Zhejiang University, in 1964.From 1984 to 1987,he was an Alexander Von Humboldt Research Fellow and Visiting Associate Professor at the University of Stuttgart, Stuttgart,Germany.He has been a Full Professor at Zhejiang University since 1988.In 1995,he was elevated to an Academician of the Chinese Academy of Engineering.He is currently the Director of the Institute of Industrial Process Control and the National Engineering Research Center of Industrial Automation,Zhejiang University.He is author/co-author of 450 journal and conference papers. His current research interests include modeling,control,and optimization of complex systems,and robust control design and its application.Prof.Sun is the former President of the Chinese Association of Automation.He has also served as Vice Chairman of the IFAC Pulp and Paper Committee and Vice-President of China Instrument and Control Society.He is a Fellow of IFAC.

Xinping Guan received the Ph.D.degree in control and systems from Harbin Institute of Technology, Harbin,China in 1999.In 2007,he joined the Department of Automation,Shanghai Jiao Tong University,Shanghai,China,where he is currently a Distinguished University Professor,the Deputy Director of University Research Management Of fi ce,and the Director of the Key Laboratory of Systems Control and Information Processing,Ministry of Education of China.Before that,he was the Professor and Dean of Electrical Engineering,Yanshan University, China.

Dr.Guan’s current research interests include cyber-physical systems,multiagent systems,wireless networking and applications in smart city and smart factory,and underwater sensor networks.He has authored and/or coauthored 4 research monographs,more than 160 papers in IEEE Transactions and other peer-reviewed journals,and numerous conference papers.As a Principal Investigator,he has fi nished/been working on many national key projects.He is the leader of the prestigious Innovative Research Team of the National Natural Science Foundation of China(NSFC).Dr.Guan is an Executive Committee Member of Chinese Automation Association Council and the Chinese Arti fi cial Intelligence Association Council.He received the First Prize of Natural Science Award from the Ministry of Education of China in 2006 and the Second Prize of the National Natural Science Award of China in 2008. He was a recipient of the“IEEE Transactions on Fuzzy Systems Outstanding Paper Award”in 2008.He is a“National Outstanding Youth”honored by NSF of China,“Changjiang Scholar”by the Ministry of Education of China and“State-level Scholar”of“New Century Bai Qianwan Talent Program”of China.

Jiming Chen(IEEE M’08-SM’11)received the B.Sc degree and Ph.D degree both in Control Science and Engineering from Zhejiang University in 2000 and 2005,respectively.He was a visiting researcher at INRIA in 2006,National University of Singapore in 2007,and University of Waterloo from 2008 to 2010.Currently,he is a full professor with Department of Control Science and Engineering,and the coordinator of group of Networked Sensing and Control in the State Key laboratory of Industrial Control Technology,Vice Director of Institute of Industrial Process Control at Zhejiang University, China.He currently serves associate editors for several international Journals including IEEE Transactions on Parallel and Distributed System,IEEE Network,IEEE Transactions on Control of Network Systems,etc.He was a guest editor of IEEE Transactions on Automatic Control,etc.His research interests include sensor networks,networked control.

Yilin Mo Assistant Professor in the School of Electrical and Electronic Engineering at Nanyang Technological University.He received his Ph.D.in electrical and computer engineering from Carnegie Mellon University in 2012 and his Bachelor of Engineering degree from Department of Automation, Tsinghua University in 2007.Prior to his current position,he was a postdoctoral scholar at Carnegie Mellon University in 2013 and California Institute of Technology from 2013 to 2015.His research interests include secure control systems and networked control systems,with applications in sensor networks and power grids.

for papers was very well

and 39 papers were submitted to the special issue.After a rigorous review process,12 papers were selected for the special issue.In this brief summary,we have clustered the papers into four areas.

:Youxian Sun,Xinping Guan,Jiming Chen,Yilin Mo.Guest Editorial for special issue on cyber-physical systems.IEEE/CAA Journal of Automatica Sinica,2015,2(3):233-234