Huanshui Zhang    Shandong University of Science and Technology

Huanshui Zhang was born in Shandong province of China in 1963. He received the B. S. degree in mathematics from Qufu Normal University in 1986, and the M.S. and Ph. D. degree in control theory from Heilongjiang University and Northeastern University in 1991 and 1997, respectively. He was promoted to an associate professor at Taishan University in 1994 and promoted to a professor at Shandong University in 1999. He was a postdoctoral fellow at Nanyang Technological University, Singapore, from 1998 to 2001, and a research fellow at Hong Kong Polytechnic University from 2001 to 2003. He joined Harbin Institute of Technology and appointed as professor from 2003 to 2006. In 2006， he was appointed as the distinguished professor of Taishan Scholar. In the year 2008, he obtained a grant from the National Science Foundation for Distinguished Young Scholars of P. R. China. In the year 2010, he was appointed as the distinguished professor of Changjiang Scholar, Ministry of Education of the P. R. China. Now he is a professor in Shandong University of Science and Technology.

Professor Zhang is one of the most reputable researchers and leaders in optimal control for time delay and stochastic systems. He has had important contributions to the basic methods of control theory and solved a number of long-standing fundamental problems. His outstanding research has led to 1 monograph, 169 journal articles (46 in IEEE Transactions including 18 IEEE TAC, and 25 in Automatica) and 143 conference papers, and has created paramount impacts with citation count of over 5600 in Google Scholar. He is the winner of National Outstanding Youth Fund (2008) and the winner of National Science Award （2008）of China. His major contributions include:

1. Contribution to optimal control and estimation of systems with input/output delays:

Optimal control for time-delay systems has received huge attention. Important progress was made in 1960s and 1980s, including the development of Kalman filter and linear quadratic (LQ) control for time-delay systems based on partial differential/difference Riccati equations (PDREs) or state augmentation in the discrete-time case. However, these results have serious limitations due to their computational complexity. Thus, how to design a controller/estimator for delay systems via standard Riccati differential/difference equations had become an open problem for a long time. Over the past 20 years, Prof. Zhang has made fundamental contributions to optimal estimation and control of multiple output/input delay systems. His seminal contributions include: (i) He developed a new approach known as ‘reorganized innovation’ [Zhang et al., IEEE TAC, 49(10), 2004; Lu, Zhang et al., Automatica, 41(8), 2005; Zhang et al., IEEE TAC, 51(5), 2006] and provided a complete solution to the optimal estimation for systems with multiple delayed measurements using standard differential/difference Riccati equations. The solution avoids solving complicated PDREs or state augmentation as in the traditional approach. His work laid a foundation for solving many related problems; (ii) By establishing a duality between optimal control of multiple input delay systems and fixed-lag smoothing, and leveraging on the ‘reorganized innovation’ approach, he solved the optimal LQ control problem for systems with multiple input delays, which was acknowledged to be “difficult problem” in [Kojima and Ishijima, IEEE CDC, p. 991, 2001], via a standard Riccati equation approach [Zhang et al., Automatica, 42(9), 2006]; (iii) By applying the indefinite Krein space and ‘reorganized innovation’ approaches, he provided a complete solution to the H-infinity fixed-lag smoothing (or estimation with preview) based on standard Riccati equations [Zhang et al, IEEE TAC, 49(12), 2004; Zhang et al., Automatica, 41(5), 2005]. The problem was listed as one of the open problems in the book [Blondel et al., 1999]. His work in this area has been cited over 3000 times.

2. Contribution to stochastic control

Stochastic linear quadratic (LQ) control for multiplicative noise systems with delay has remained very challenging since the 1970s [Bismut, SICON, 14(3), 1976] and little progress was made in several decades. The major obstacle lies in that the ‘separation principle’ does not hold for stochastic systems and thus the conventional control theory becomes ineffective. By proposing a novel method for solving delayed forward-backward differential/difference equations (FBDEs) arising from the optimal LQ control, Professor Zhang developed a new ‘separation principle’ for stochastic LQ control with a Riccati-type equation called Riccati-ZXL equation, and provided a complete solution to stochastic control with input delay, including the necessary and sufficient conditions for existence and analytical controllers for both the finite and infinite horizon stochastic LQ control problems [Zhang et al., IEEE TAC, 60(10), 2015; Zhang et al., IEEE TAC, 62(1), 2017]. This work represents an important breakthrough for stochastic control since 1970s. The proposed method for decoupling FBDEs by Professor Zhang is a significant contribution to control theory, which breacks through the obstacle from maximum principle to feedback controller design for some complicated control problems. With the method, Professor Zhang solved a number of fundamental control problems: (i) He obtained a necessary and sufficient condition for the mean square stabilizability of networked control systems (NCSs) with simultaneous transmission delay and packet dropout [Tan, Li and Zhang, Automatica, 59(9), 2015; Tan and Zhang, IEEE TAC, 62(8), 2017]. This problem was recognized to be extremely difficult and challenging under User Datagram Protocol in [W. Zhang et al., Automatica, 44, p. 3206, 2008]; (ii) For the first time, he obtained the necessary and sufficient condition for the mean square stabilizability of mean-field stochastic systems under the basic assumptions [Zhang et al., IEEE TAC, 64(3), 2019; Qi, Zhang et al., IEEE TAC, 64(8), 2019]; (iii) He solved the long-standing fundamental problem of singular (irregular) LQ control. Singular LQ has received significant attention since the 1970s. However, most of the existing results are limited to some special cases: specially given initial state [Ho, JOTA, 9(1), 1972]; positive-definite higher order derivatives [Krener, SICON, 15(2), 1977; Zhang and Zhang, SICON, 53(4), 2015]; open-loop control [Sun et al., SICON, 54(5), 2016]. Professor Zhang derived the necessary and sufficient solvability condition for singular control with arbitrary initial values [Zhang and Xu, SCIS, 62(9), 2019]; (iv) He provided a complete solution to the open-loop LQ control of the Stakelberg game with the necessary and sufficient solvability condition under wild assumptions [Xu, Zhang et al., IEEE TAC, 60(5), 2015].

Prof. Zhang is active in national and international academic activities. He has served as various positions in international journals and conferences, such as Associate Editor IEEE Trans. on Circuits and Systems Part I: Regular Papers, and IEEE Trans. on Automatic Control, Journal of Control, Automation, and Systems, and Journal of Industrial and Management Optimization, and regional chair of the 13th IEEE International Conference on Control and Automation, Macedonia, regional program co-chair of the 8th World Congress on Intelligent Control and Automation, Jinan, China, distinguished lecture speaker of the 24th Chinese Control and Decision Conference and the 30th Chinese Control Conference.