!!Qing-Long Han - Publications
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__Ten Representative Publications:__ \\
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[[1]  D. Yue, Q.-L. Han, and C. Peng, “State feedback controller design of networked control systems,” IEEE Transactions on Circuits and Systems -II: Express Briefs, vol 51, no. 11, pp. 640-644, November 2004.   \\
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[[2]  D. Yue, Q.-L. Han, and J. Lam, “Network-based robust H∞ control of systems with uncertainty,” Automatica, vol. 41, no. 6, pp. 999-1007, June 2005.  \\
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Significance for Representative Publications [[1] and [[2]:  Networked control is the current trend for industrial automation due to the increasing use of shared communication networks and introducing Industry 4.0. Networked control systems are spatially distributed systems in which the communication between sensors, actuators and controllers occurs through a shared band-limited digital communication network. The use of a multi-purpose shared network to connect spatially distributed elements results in flexible architectures and generally reduces installation and maintenance costs.  Consequently, networked control systems have been finding applications in a broad range of areas such as smart grids, advanced manufacturing systems, automotive and aerospace industries, mobile sensor networks, remote surgery, automated highway systems, and unmanned aerial vehicles. However, the use of the communication network in control systems introduces new challenges due to inherent network-limited bandwidth. Three of the major challenges are the effects of network-induced delays, data packet dropouts, and packet disorders on networked control systems. The two pioneering papers [[1] (Yue, Han,and Peng, 2004) and [[2] (Yue, Han, and Lam, 2005) proposed a new model of networked control systems is provided for the first time by taking time-varying network-induced delays, data packet dropouts and packet disorders into account simultaneously. This model has successfully been employed to investigate the state feedback control and dynamic output control of networked control systems.\\
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Impact Representative Publications [[1] and [[2]:  According to Clarivate Analytics Web of Science Core Collection, as of 26 March 2021, the first pioneering paper [[1] (Yue, Han, and Peng, 2004) received 635 citations which are ranked as No. 1 in 116 articles in IEEE Transactions on Circuits and Systems -II: Express Briefs in 2004. The second pioneering paper [[2] (Yue, Han, and Lam, 2005) received 831 citations which are ranked as No. 2 in 225 articles in Automatica in 2005.  These two pioneering papers were highly cited papers and hot papers in the field of“Engineering”, which were among the top one-tenth of one percent of all papers from 2004 and 2005. \\
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[[3] Q.-L. Han, “Absolute stability of time-delay systems with sector-bounded nonlinearity,” Automatica, vol. 41, no. 12, pp. 2171-2176, December 2005. \\
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Significance:  A time-delay system is also called a system with aftereffect or dead-time. A defining feature of a time-delay system is that its future evolution is related not only to the current state but also to the past state of the system. Time-delay systems are a particular class of infinite dimensional systems, which have complicated dynamic properties compared with delay-free systems. Many practical systems encountered in areas, such as engineering, physics, biology, operation research and economics, can be modelled as time-delay systems. Therefore, time-delay systems have attracted continuous interest of researchers in a wide range of fields in natural and social sciences. Stability of time-delay systems is a fundamental issue from both theoretical and practical points of view. This paper deals with the problem of absolute stability of time-delay systems with sector-bounded nonlinearity. Some new delay-dependent stability criteria are obtained and formulated in the form of linear matrix inequalities (LMIs). Neither model transformation nor bounding technique for cross terms is involved through derivation of the stability criteria. This paper provides a new direction to address stability of time-delay systems. \\
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Impact:  According to Clarivate Analytics Web of Science Core Collection, as of 26 March 2021, this paper received 410 citations which are ranked as No. 9 in 225 articles in Automatica in 2005 and was a highly cited paper in the field of “Engineering”.\\
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[[4] Q.-L. Han, “On designing time-varying delay feedback controllers for master-slave synchronization of Lur’e systems,” IEEE Transactions on Circuits and Systems I: Regular Papers, vol. 54, no. 7, pp. 1573 – 1583, July 2007.  \\
\\Significance:  Chaotic synchronization has received considerable attention due to its practical applications such as secure communications in which an information bearing signal is hidden on a chaotic carrier signal. As is well known, there are some nonlinear systems, such as Chua’s circuit, n-scroll attractors and hyperchaotic attractors, which can be represented as Lur'e systems. Therefore, master–slave synchronization for Lur’e systems has well studied in the last decade. Due to the propagation delay frequently encountered in remote master–slave synchronization schemes, it is of great significance to investigate the delay effect on master–slave synchronization. This paper is concerned with the problem of designing time-varying delay feedback controllers for master-slave synchronization of Lur'e systems. Two cases of time-varying delays are fully considered; one is the time-varying delay being continuous uniformly bounded while the other is the time-varying delay being differentiable uniformly bounded with the derivative of the delay bounded by a constant. Based on Lyapunov-Krasovskii functional approach, some delay-dependent synchronization criteria are first obtained and formulated in the form of linear matrix inequalities (LMIs). The relationship between synchronization criteria for the two cases of time-varying delays is built. Then, sufficient conditions on the existence of a time-varying delay feedback controller are derived by employing these newly obtained synchronization criteria. The controller gains can be achieved by solving a set of LMIs. Finally, Chua's circuit is used to illustrate the effectiveness of the design method. \\
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Impact:  According to Clarivate Analytics Web of Science Core Collection, as of 26 March 2021, this paper receives 131 citations which are ranked as No. 9 in 256 articles published in IEEE Transactions on Circuits and Systems I: Regular Papers in 2007. This paper was a highly cited paper in the field of "Engineering”.\\
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[[5] D. Yue, E. Tian, and Q.-L. Han, “A delay system method for designing event-triggered controllers of networked control systems,” IEEE Transactions on Automatic Control, vol. 58, no. 2, pp. 475-481, February 2013.  \\
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Significance:  In advanced control applications, control implementation is largely based on a digital platform, where control components (physical plant, sampler, controller and actuator) are connected through a communication network. In such implementation, a control task consists of sampling physical signals, computing control signals and implementing actuator signals. Traditionally, control tasks are executed in a periodic way, which leads to so-called time-triggered control. Time-triggered control paves an easy way for us to design suitable controllers using fruitful sampled-data system theory. However, in some cases where the system reaches its steady state and no disturbance is imposed on the system, executing those control tasks periodically wastes both computation and energy resources of battery-based devices. Moreover, if a sampling period is approaching zero, many redundant sampled signals will be released to a shared communication network with limited bandwidth, which inevitably causes a congested network traffic. Thus, in these cases, time-triggered control should give way to event-triggered control. This paper proposed a novel event-triggered communication scheme for control of networked systems. Applying this scheme, communication resources can be significantly saved while preserving the desired system’s performance. This paper established a novel threshold-error-dependent model for analysis and synthesis. This paper developed a new methodology for the co-design of the event-triggered communication scheme and the controller in a unified framework.\\
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Impact:  According to Clarivate Analytics Web of Science Core Collection, as of 26 March 2021, this paper received 795 citations which are ranked as No. 2 in 365 articles in IEEE Transactions on Automatic Control in 2013 and is a highly cited paper in the field of "Engineering”. \\
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[[6] G. Guo, L. Ding, and Q.-L. Han, “A distributed event-triggered transmission strategy for sampled-data consensus of multi-agent systems,” Automatica, vol. 50, no. 5, pp. 1489 – 1496, May 2014.   \\
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Significance:  Multi-agent systems (MASs), in which distributed sensing, communication, computing, and control are integrated, are usually employed to achieve coordinated tasks by letting a group of agents work cooperatively with each other. As a fundamental problem of cooperative control of MASs, consensus has attracted considerable attention due to its widespread applications in various areas, such as attitude alignment of satellites, formation of multiple robots, estimation over sensor networks, power management in power networks, distributed optimization, and so on. In this paper, a novel distributed event-triggered sampled-data transmission strategy is proposed, which allows the event-triggering condition to be intermittently examined at constant sampling instants. Based on this novel strategy, a sampled-data consensus control protocol is presented, with which the consensus of distributed multi-agent systems can be transformed into the stability of a system with a time-varying delay. Then, a sufficient condition on the consensus of the multi-agent system is derived. Correspondingly, a co-design algorithm for obtaining both the parameters of the distributed event-triggered transmission strategy and the consensus controller gain is proposed. \\
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Impact:  According to Clarivate Analytics Web of Science Core Collection, as of 26 March 2021, this paper received 401 citations which are ranked as No. 5 in 391 articles in Automatica in 2014 and is a highly cited paper in the field of “Engineering”. \\
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[[7] X. Ge and Q.-L. Han, “Distributed formation control of networked multi-agent systems using a dynamic event-triggered communication mechanism,” IEEE Transactions on Industrial Electronics, vol. 64, no. 10, pp. 8118-8127, October 2017.  \\
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Significance:  Formation control of multi-agent systems has been one of the most actively studied topics in robotic and control communities, and widely applied in real life, such as target localization, oceanic search and rescue, undersea oil pipeline maintenance and forest monitoring.  The aim of formation control is to drive a group of autonomous agents to achieve and to maintain a desired geometric pattern on their states/outputs. A defining feature of a formation control problem is that multiple agents work together to accomplish a collaborative formation task. In this regard, inter-agent communication plays a crucial role in formation control.  In this paper, a new dynamic event-triggered communication mechanism is firstly proposed for networked MASs subject to limited communication resources such that a team of networked collaborative agents effectively and efficiently achieve an anticipated formation structure.  \\
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Impact:  According to Clarivate Analytics Web of Science Core Collection, as of 26 March 2021, this paper received 191 citations which are ranked as No. 8 in 1,000 articles in IEEE Transactions on Industrial Electronics in 2017 and is a highly cited paper in the field of Engineering.  \\
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[[8]  D. Ding, Z. Wang, Q.-L. Han, and G. Wei, “Security control for discrete-time stochastic nonlinear systems subject to deception attacks,” IEEE Transactions on Systems, Man and Cybernetics-Systems, vol. 48, no. 5, pp. 779-789, May 2018.   \\
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Significance:  This paper provides a systematic framework of security control in probability for general nonlinear stochastic systems under deception attacks. The security performance is originally proposed with the conception of input-to-state stability in probability.  Sufficient conditions are then developed to achieve the prescribed security in probability while obtaining an upper bound of the LQG-like quadratic cost criterion. These developed conditions profoundly disclose the effect on security from deception attacks. Furthermore, an original easy-solution scheme of desired controller gain is proposed in order to convenient engineering applications via the matrix inverse lemma. \\
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Impact:  This paper received The 2020 IEEE Systems, Man, and Cybernetics (SMC) Society Andrew P. Sage Best Transactions Paper Award. \\
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According to Clarivate Analytics Web of Science Core Collection, as of 26 March 2021, this paper received 152 citations which are ranked as No. 1 in 208 articles published in IEEE Transactions on Systems, Man and Cybernetics-Systems in 2018. This paper is a highly cited paper in the field of “Engineering”. \\
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[[9]  L. Ding, Q.-L. Han, L.Y. Wang, and E. Sindi, “Distributed cooperative optimal control of DC microgrids with communication delays,” IEEE Transactions on Industrial Informatics, vol. 14, no. 9, pp. 3924-3935, September 2018. \\
\\Significance:  A smart grid is an electrical grid which includes a variety of operation and energy measures including smart meters, smart appliances, renewable energy resources, and energy efficient resources. Electronic power conditioning and control of the production and distribution of electricity are important aspects of the smart grid. In this paper, a new methodology is developed to achieve integrated control and management of direct current (DC) microgrids subject to communication delays. New distributed optimization algorithms are proposed to ensure a suitable tradeoff between load sharing and voltage regulation in DC microgrids.  By the simulation case study on Beijing Dual-Source Trolleybus System, the algorithms demonstrated remarkable abilities in improving reliability and maintaining scalability, especially, in terms of their fast convergence, robustness to load variations and communication delays, plug-and-play feature, and tradeoff functionality.\\
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Impact:  According to Clarivate Analytics Web of Science Core Collection, as of 26 March 2021, this paper received 94 citations which are ranked as No. 11 in 547 articles published in IEEE Transactions on Industrial Informatics in 2018 and is a highly cited paper in the field of “Engineering”. \\
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[[10]  L. Ding, Q.-L. Han, and X.-M. Zhang, “Distributed secondary control for active power sharing and frequency regulation in islanded microgrids using an event-triggered communication mechanism,” IEEE Transactions on Industrial Informatics, vol. 15, no. 7, pp. 3910-3922, July 2019. \\
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Significance:  For distributed control of microgrids, limited communication resources may result in detrimental consequences, such as traffic congestion and limits on critical monitoring and protection functions, degrading or even destroying the control performance. To address this issue, a new and efficient method is developed to achieve distributed control for islanded microgrids subject to limited communication resources. More specifically, a novel sampled-data-based event-triggered communication mechanism is presented to reduce the frequency of exchange data among neighbourhood distributed generation. A new distributed secondary control strategy incorporating the sampled-data-based event-triggered communication mechanism is proposed to achieve accurate active power sharing and frequency regulation simultaneously for islanded microgrids. The proposed distributed control strategy can improve reliability, efficiency, and scalability of microgrids.\\
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Impact:  This paper received The 2020 IEEE Industrial Electronics Society IEEE Transactions on Industrial Informatics Outstanding Paper Award.\\
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According to Clarivate Analytics Web of Science Core Collection, as of 26 March 2021, this paper received 73 citations which are ranked as No. 6 in 623 articles published in IIEEE Transactions on Industrial Informatics in 2019 and is a highly cited paper in the field of “Engineering”. \\
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