Chen et al. / Front Inform Technol Electron Eng 2019 20(1):1-3 1

Frontiers of Information Technology & Electronic Engineering www.jzus.zju.edu.cn; engineering.cae.cn; www.springerlink.com ISSN 2095-9184 (print); ISSN 2095-9230 (online) E-mail: [email protected]

Editorial: Complex system and intelligent control: theories and applications

Jie CHEN†‡1,2, Ben M. CHEN3,4, Jian SUN1 1School of Automation, Beijing Institute of Technology, Beijing 100081, China 2Tongji University, Shanghai 200092, China 3Department of Mechanical and Automation Engineering, Chinese University of Hong Kong, Hong Kong, China 4Department of Electrical and Computer Engineering, National University of Singapore, Singapore †E-mail: [email protected] https://doi.org/10.1631/FITEE.1910000

Complex systems are the systems that consist of and swarming intelligence. Intelligent control tries to a great many diverse and autonomous but interacting borrow ideas from the sciences of physics, mathe- and interdependent components whose aggregate matics, biology, neuroscience, and others to develop a behaviors are nonlinear. As phased by Aristotle, “the control system to manage a complex process in an whole is more than the sum of its parts;” properties of uncertain environment. Intelligent control is a kind of complex systems are not a simple summation of their interdisciplinary new technology, which integrates individual parts. the knowledges of , computer science, Complex systems are widespread. Typical exam- , information theory, and other ples of complex systems can be found in the human areas. Intelligent control has been shown to be effec- brain, flocking formation of migrating birds, power tive in controlling complex systems where traditional grid, transportation systems, autonomous vehicles, control methods can hardly perform well. social networks, and communication networks. In this context, the Chinese Academy of Engi- Complex systems have some distinct properties, neering (CAE) organized a special issue on complex such as highly nonlinear dynamics, emergence, ad- system and intelligent control in Frontiers of Infor- aptation, and self-organization, which are difficult to mation Technology and Electronic Engineering. This model precisely. Such properties lead to difficulties in special issue aims to promote research on complex understanding the behaviors of complex systems, to systems and intelligent control and reflect the most model them accurately, to control them, and to make recent advances, with emphasis on both theories and them work in a specific way we desire. applications. After rigorous review process, 11 papers There is no generally agreed definition of intel- by researchers worldwide have been selected for this ligent control. Generally speaking, intelligent control special issue, including one survey paper and 10 re- is a class of control methods that use artificial intel- search papers. ligence techniques, such as , neural net- Electric power grid as a typical example of works, evolutionary computation, , complex systems has brought a great change in our daily lives. An accurate, fast, and robust power sys- ‡ Corresponding author tem state estimation is undoubtedly significant. Gang © Zhejiang University and Springer-Verlag GmbH Germany, part of WANG et al. gave a comprehensive review on some Springer Nature 2019 2 Chen et al. / Front Inform Technol Electron Eng 2019 20(1):1-3 of the recent advances in power system state estima- ceived much attention since their wide applications in tion with an emphasis on the solvers that can effi- mobile sensor networks, formation of unmanned ciently obtain optimal or near-optimal solutions to flight vehicles, smart grids, etc. Formation control is nonconvex state estimation tasks. Some directions for an important topic in cooperative control for multi- future research were also discussed. agent systems. Mao-peng RAN et al. considered the Motion coverage is an important real-world ap- time-varying formation tracking problem for multi- plication for mobile robots. To deal with the multi- agent systems subject to unknown nonlinear dynam- robot coverage motion planning problem, Guan-qiang ics and external disturbances. An extended state ob- GAO and Bin XIN proposed an auction-based span- server (ESO) was designed to estimate the total un- ning tree coverage (A-STC) algorithm. Compared certainty of the system. An ESO-based time-varying with existing methods, this algorithm is effective, formation tracking protocol was proposed. Effec- time-efficient, and complete, especially in large tiveness of the theoretical results was demonstrated complex configuration spaces. by application to the target enclosing problem of a A snake robot is a biomorphic robot to imitate group of unmanned aerial vehicles (UAVs). Mao-bin snake’s morphology. To make a snake robot as agile LU and Lu LIU studied the leader-following con- as a biological snake, locomotion generation and sensus problem of a class of heterogeneous sec- body motion control are two important issues. ond-order nonlinear multi-agent systems subject to Wenjuan OUYANG et al. proposed a biomimetic disturbances. A class of distributed control laws that control approach for steering a snake robot. The depend on the relative state of the system were pro- proposed method includes an artificial central pattern posed to solve the problem. generator, a cerebellar model articulation controller, In recent years, UAVs have been widely applied and a proportional-derivative controller. Their simu- in many fields, such as reconnaissance, search and lations and experiments demonstrated good perfor- rescue, surveillance, environment monitoring, large- mance and adaptability of the method. accident investigation, parcel delivery, and agricul- Ning-shi YAO et al. presented an autonomous ture service. Among all the UAVs, the quadrotor robotic blimp equipped with only one monocular platform is the most popular one. Control and navi- camera, named Georgia Tech Miniature Autonomous gation of quadrotor UAV has received much attention. Blimp (GT-MAB). It was designed to support human Yu-jiang ZHONG et al. presented a reliable active robot interaction experiments in an indoor space. The fault-tolerant tracking control method for a quadrotor blimp is capable of effectively detecting the face of a UAV with model uncertainties and actuator faults. A human subject, following the human, and recognizing radial basis function neural network was introduced hand gestures by employing a deep neural network to estimate the model uncertainties online, modify the based algorithm. Their experimental results demon- reference model adaptively, and incorporate it into the strated that GT-MAB has reliable human-detection model reference adaptive control scheme. To deal and human-following capabilities. with actuator faults, a fault detection and diagnosis Execution control is a critical task of robot ar- estimator and a fault compensation term were intro- chitecture design, and has important influence on the duced into the control law. Shu-peng LAI et al. pro- quality of the final system. Martin MOLINA et al. posed a computationally efficient safe flying corridor presented a general method for execution control. The navigation method for a quadrotor UAV. This method proposed method was integrated in the Aerostack can generate a jerk-limited trajectory within a safe open-source framework. Their experiments demon- corridor. Unlike the existing methods, the proposed strated the validity, feasibility, and effectiveness of method can generate a smooth non-stop trajectory the proposed method. with safety guarantee but does not require the vehicle In recent years, multi-agent systems have re- stop at each intersected point of the connected boxes. Chen et al. / Front Inform Technol Electron Eng 2019 20(1):1-3 3

A flywheel suspended on active magnetic bear- Prof. Jie CHEN received BS, MS, and ings as a kind of complex system has been found to PhD degrees in control theory and control engineering from the Beijing have many applications in energy storage devices. Institute of Technology, Beijing, China, However, the controller design problem for a in 1986, 1993, and 2001, respectively. flywheel system is still challenging. Xujun LYU et al. He is currently the President of Tongji applied the characteristic model based all-coefficient University, China. He is an Academi- adaptive control method to active magnetic bearings cian of the Chinese Academy of Engi- neering and IEEE Fellow. His current suspended flywheel systems. An extensive simulation research interests include intelligent control and decision in showed that the characteristic model based all- complex systems, multi-agent systems, and optimization coefficient adaptive control method has considerable methods. robustness with respect to plant uncertainties, exter- Prof. Ben M. CHEN received the BS nal disturbances, and time delay. degree in computer science from Xia- Ze-zhi TANG et al. investigated the disturbance men University, China in 1983, MS rejection problem of active magnetic bearing systems. degree in electrical engineering from A disturbance observer based iterative learning con- Gonzaga University, USA in 1988, and trol strategy that combines the extended state ob- PhD degree in electrical and computer engineering from Washington State server with a classic iterative learning control law was University, USA in 1991. He is cur- proposed. Their simulation and comparison con- rently a professor in the Department of firmed that the proposed method can yield good Mechanical and Automation Engineering at Chinese Univer- tracking performance. sity of Hong Kong, and a professor in the Department of Electrical and Computer Engineering, National University of The papers included in this special issue cover a Singapore. His current research interests include unmanned broad spectrum of current research topics on complex systems, robust control, and control applications. He is an systems and intelligent control, including formation IEEE Fellow. control of complex multi-agent systems, control and navigation of a quadrotor UAV, robust control of Prof. Jian SUN received the BS degree from the Department of Automation robots, interaction between human and robot, control and Electric Engineering at Jilin Insti- of systems with model uncertainties and disturbances. tute of Technology, China in 2001, the We hope that this special issue will benefit the re- MS degree from Changchun Institute of searchers in these fields and foster research on com- Optics, Fine Mechanics and Physics, Chinese Academy of Sciences (CAS), plex systems and intelligent control. China in 2004, and the PhD degree This special issue would not be possible without from Institute of Automation, CAS, the support of many people, including the authors and China in 2007. He is currently a professor in School of Auto- reviewers. We are indebted to the editorial staff of the mation at Beijing Institute of Technology, China. His current journal for their enormous assistances, and to the research interests include networked control systems, time- delay systems, and security of cyber-physical systems. Editors-in-Chief, Profs. Yun-he PAN and Xi-cheng

LU, for this great opportunity.