IEEE Systems, Man and Cybernetics Magazine - April 2021 - 54

Future Work
CPSs play key roles in critical areas, such as smart
grids, water networks, and process control industries,
and thus it is critical to monitor their security. We
believe that security control reduces threats, improves
resilience, and enhances reliability. There are many
works about IT system security, but CPS security control is a relatively new subject that requires further
investigation. In the following, some potential future
areas of study are discussed.
◆◆ The detectability of attack diagnosis methods: CPSs
have complex structures with many components.
Hackers usually gain knowledge of systems and launch
intelligent attacks, such as replay and deception
strikes, which are difficult to detect [92]-[94]. The
sooner an attack is detected, the less damage it may
cause. However, only a few studies that include high
attack detectability, such as authentication control signals [95], [96] and coding-based secure control methods [100], [219], exist in the literature. Therefore, this is
an area requiring further exploration.
◆◆ The convergence of estimates under attack conditions:
One of the main CPS challenges is the convergence of
estimators and observers under attack conditions.
The complexity of CPSs and their infrastructures
makes it hard to develop estimation and observer
design methodologies that are stable. Only a few methods, such as those in [9], [103], [107], and [110], can
guarantee estimation method stability under attack
conditions. Thus, the issue represents a significant
concern that needs more attention. Furthermore,
many open problems remain in the area of designing
robust attack and fault detection estimators for various system classes.
Sensor Data Fusion to Improve Attack Detectors
Attackers can take advantage of a lack of observability in
parts of CPSs, and they can take actions to make systems
unobservable. This is a problem that requires further
research. In certain situations, one approach to design
robust attack detectors and resilient controllers is to
employ multisensory configurations and apply data fusion
techniques. Multisensor fusion methods utilize redundancy in multiple sets of data to improve attack detectors
[97], [108], [161], [205], [215]. These strategies should be
further studied to arrive at more robust observers and
resilient controllers.

component failures, FTC methodologies should be studied
in the context of a CPS under attack.
Acknowledgments
We acknowledge financial support from the Natural Sciences and Engineering Research Council of Canada and
other sponsors.
About the Authors
Mojtaba Kordestani (kordest@uwindsor.ca) earned his
B.S. degree in electronic engineering and his M.S. degree
in control engineering from Malek Ashtar University and
Tehran Azad University, Iran, in 2002 and 2008, respectively. He earned his Ph.D. degree in electrical engineering in
2018 from the University of Windsor, Windsor, Ontario,
N9B 3P4, Canada, where he is a postdoctoral fellow. His
research interests include control, estimation, fault diagnostics and fault tolerant control, and predictive control.
He has published more than 40 refereed journal and conference papers in these areas. He received a full research
scholarship from the University of Windsor in 2015, and
he won an Ontario Graduate Scholarship in 2017. He
chaired IEEE Young Professionals at the University of
Windsor during 2016-2018. He served as vice chair of the
IEEE Windsor Section in 2019-2020 and is the 2021 chairelect. He is a Senior Member of IEEE.
Mehrdad Saif (msaif@uwindsor.ca) earned his B.S.
degree in 1982, M.S. degree in 1984, and D.Eng. degree in
1987, all in electrical engineering, from Cleveland State
University, Ohio. He has been the dean of the Faculty of
Engineering, University of Windsor, Windsor, Ontario,
N9B 3P4, Canada, since July 2011, overseeing program
expansions into areas such as aerospace engineering,
engineering management, and mechatronics. His
research interests include cyberphysical systems, estimation and observer theory, model-based fault diagnostics,
condition monitoring, cybersecurity, diagnostics and
prognostics, and applications of these areas to automotive, power, autonomous systems, and other complex systems. He is currently a member of the editorial boards of
IEEE Access; IEEE Systems, Man, and Cybernetics
Magazine; and IEEE Systems Journal. He is a registered
professional engineer in Ontario, Canada, and a fellow of
the Canadian Academy of Engineering and the Institution
of Engineering and Technology. He is a Senior Member
of IEEE.
References

Resilient Control System Design
Resilient control is a relatively new area of study [102],
[111], [118], [128], [207], [218]. CPSs need resilient control
methodologies to maintain operations during attacks.
There is a rich body of literature in the field of fault-tolerant control (FTC). Although control system resiliency in
CPSs that are being attacked may be a more complicated
problem than it is in systems that are experiencing
54

IEEE SYSTEMS, MAN, & CYBERNETICS MAGAZINE Apri l 2021

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