Resilient Network Control Systems
Sponsored by European Commission, FP7 PIRG

Introduction:


The compounding complexity of digital devices, the expansion of networks in size and diversity, and the ever increasing dependency of business and government sectors alike on networked infrastructures has undoubtedly resulted in a pressing need for advanced design/analysis tools and for effective monitoring and control strategies. More critically, however, it has become urgently necessary to obtain scalable and effective methodologies for diagnosing faults, assessing and estimating system properties of interest, and operating these complex systems in uncertain environments and possibly in the presence of communication constraints, faults or adversaries. Depending on the underlying application, the causes for these adversarial conditions may range from design inconsistencies, component malfunctions  and communication delays/lapses to variability in interconnection topologies and actions by intruders or users/operators that are misbehaving. The implications of faults and adversarial behavior can be far ranging, including user dissatisfaction and nuisance, large economic costs, and even loss of life.


This research project aimed to directly address these needs by focusing primarily on networked control systems (initially within the context of interacting discrete event systems and eventually expanding to switched linear systems and to more general hybrid systems). The project concentrated on the following two objectives:
(i) Establishment of techniques for monitoring and diagnosing faults or, more generally, abnormal behavior and functional changes in dynamic systems and networks, under limited and possibly corrupted information. The aim was to explore a variety of techniques and models, which include both deterministic and probabilistic settings. In particular, considering probabilistic settings, the project studied error bounds using optimal classification rules in hidden Markov models (WP2), and developed extensions of probabilistic model-based diagnosis approaches to distributed settings by combining ideas from distributed fault diagnosis (in deterministic  settings) and belief propagation techniques (WP3). Considering deterministic models, in an effort to handle complexity issues that arise in large-scale systems, this part of the project developed distributed synchronization schemes for fault diagnosis in distributed systems (WP4).
(ii) Development of resiliency- and privacy-ensuring control strategies for networked control systems. In particular, one of the objectives here was to study  supervisory control strategies for preserving opacity in discrete event systems (WP1), and also develop a game-theoretic framework for preserving opacity in settings where multiple systems interact (WP5).


The research was completed successfully and significant progress was made in both of the objectives mentioned above. This progress can ultimately enable the automated operation of detection and control mechanisms, which will naturally lead to resilient and safe operation of these complex systems despite the presence of malicious or non-malicious disruptions. Though some of these challenges have been addressed using centralized algorithms (e.g., monolithic diagnosers and controllers for supervisory control), the scientific challenge in the case of the large-scale networked control systems that emerge as a result of the proliferation of networking and digital technology is to fully extend these techniques to distributed/decentralized settings, understand the costs and performance tradeoffs involved, and (if necessary) develop new algorithms that can provide suboptimal but adequate performance at reasonable costs. Some steps towards this direction have already been taken within the context of this project.






Publications:


Published and accepted journal publications within the context of this project are provided below. A complete list of publications by Dr. Hadjicostis can be found here.


11) Lingxi Li and C. N. Hadjicostis, ``Minimum Initial Marking Estimation in Labeled Petri Nets,'' IEEE Transactions on Automatic Control (to appear).

10) A. Saboori and C. N. Hadjicostis, ``Verification of Infinite-Step Opacity and Analysis of its Complexity,'' IEEE Transactions on Automatic Control, vol. 57, no. 5, pp. 1265-1269, May 2012.

9) A. Saboori and C. N. Hadjicostis, ``Opacity Enforcing Supervisory Strategies via State Estimator Constructions,'' IEEE Transactions on Automatic Control, vol. 57, no. 5, pp. 1155-1165, May 2012. Supplement with proofs for ``Opacity Enforcing Supervisory Strategies via State Estimator Constructions."

8) A. Saboori and C. N. Hadjicostis, ``Coverage Analysis of Mobile Agent Trajectory via State-Based Opacity Formulations,'' Control Engineering Practice (Special Issue on ``Selected Papers from 2nd International Workshop on Dependable Control of Discrete Systems"), vol. 19, no. 9, pp. 967-977, September 2011 (invited).

7) A. Saboori and C. N. Hadjicostis, ``Verification of K-Step Opacity and Analysis of its Complexity,'' IEEE Transactions on Automation Sciences and Engineering, vol. 8, no. 3, pp. 549-559, July 2011. Supplement with proofs for ``Verification of K-Step Opacity and Analysis of its Complexity."

6) Lingxi Li and C. N. Hadjicostis, ``Least-Cost Transition Firing Sequence Estimation in Labeled Petri Nets with Unobservable Transitions," IEEE Transactions on Automation Science and Engineering, vol. 8, no. 2, pp. 394-403, April 2011.

5)  Yu Ru and C. N. Hadjicostis, ``Sensor Selection for Structural Observability in Discrete Event Systems Modeled by Labeled Petri Nets,'' IEEE Transactions on Automatic Control, vol. 55, no. 8, pp. 1751-1764, August 2010.


4) Yu Ru and C. N. Hadjicostis, ``Fault Diagnosis in Discrete Event Systems Modeled by Partially Observed Petri Nets,'' Journal of Discrete Event Dynamic Systems (Special Issue on ``Selected Papers from WODES 2008, the 9th International Workshop on Discrete Event Systems"), vol. 19, no. 4, pp. 551-575, December 2009 (invited).


3) E. Athanasopoulou, Lingxi Li, and C. N. Hadjicostis, ``Maximum Likelihood Failure Diagnosis in Finite State machines Under Unreliable Observations,'' IEEE Transactions on Automatic Control, vol. 55, no. 3, pp. 579-594, March 2010.

2) Lingxi Li and C. N. Hadjicostis, ``Least-Cost Planning Sequence Estimation in Labeled Petri Nets,'' Transactions of the Institute of Measurement and Control, vol. 33, no. 3-4, pp. 317-331, May 2011 (Special Issue on ``Planning and Scheduling in Complex Systems").

1) Tung Le and C. N. Hadjicostis, ``Graphical Inference for Multiple Intrusion Detection,'' IEEE Transactions on Information Forensics and Security (Special Issue on ``Statistical Methods for Network Security and Forensics"), vol. 3, no. 3, pp. 370-380, September 2008.





Published and accepted conference publications within the context of this project are provided below. A complete list of publications by Dr. Hadjicostis can be found here.


24) C. N. Hadjicostis, ``Resolution of Initial State Opacity in Security Applications of DES," Proceedings of MED 2012, the 20th Mediterranean Conference on Control and Automation, Barcelona, Spain, 2012 (to appear).


23) C. Keroglou and C. N. Hadjicostis, ``Bounds on the Probability of Misclassification among Hidden Markov Models," Proceedings of CDC/ECC 2011, the 50th IEEE Conference on Decision and Control and European Control Conference, pp. 385-390, Orlando, FL, December 12-15, 2011 (presented by the researcher).


22) Tung Le and C. N. Hadjicostis, "Marginal Analysis on Binary Pairwise Gibbs Random Fields," Proceedings of IEEE CASE 2011, the 7th Annual IEEE Conference on Automation Science and Engineering, pp. 316-321, Trieste, Italy, August 2011 (presented by the researcher).


21) C. Keroglou and C. N. Hadjicostis, ``Bound on the Probability of Misclassification between Two HMMs," Proceedings of MED 2011, the 19th Mediterranean Conference on Control and Automation, pp. 449-454, Corfu Island, Greece, 2011.


20) Tung Le and C. N. Hadjicostis, ``Convergence of Belief Propagation Algorithms on Binary Pairwise Gibbs Random Fields," Proceedings of 2011 IFAC World Congress, Milan, Italy (presented by the researcher).


19) Yu Ru and C. N. Hadjicostis, ``Constrained Sensor Selection for Discrete Event Systems Modeled by Petri Nets," Proceedings of ACC 2011, the 2011 American Control Conference, pp. 4502-4507, San Francisco, California, 2011.


18) A. Saboori and C. N. Hadjicostis, ``Opacity Verification in Stochastic Discrete Event Systems," Proceedings of CDC 2010, the 2010 IEEE Conference on Decision and Control, pp. 6759-6764, Atlanta, GA, 2010 (presented by the researcher).


17) Tung Le, S. Tatikonda, and C. N. Hadjicostis, ``Performance Analysis of Belief Propagation Algorithms for Multiple Fault Diagnosis Applications," Proceedings of CDC 2010, the 2010 IEEE Conference on Decision and Control, pp. 1627-1632, Atlanta, GA, 2010 (presented by the researcher).


16) C. N. Hadjicostis, ``Supervisory Control Strategies for Enhancing System Security and Privacy," Proceedings of the 48th Annual Allerton Conference on Communication, Control, and Computing, pp. 1622-1627, Allerton House, IL, 2010 (invited, presented by the researcher).


15) A. Saboori and C. N. Hadjicostis, ``Reduced-Complexity Verification for Initial-State Opacity in Modular Discrete Event Systems," Proceedings of WODES 2010, the 10th International Workshop on Discrete Event Systems, Berlin, Germany, 2010 (invited, presented by the researcher).


14) A. Saboori and C. N. Hadjicostis, ``Probabilistic Opacity for Stochastic Discrete Event Systems," Proceedings of MTNS 2010, the 19th International Symposium on Mathematical Theory of Networks and Systems, Budapest, Hungary, 2010 (presented by the researcher).


13) Yu Ru and C. N. Hadjicostis, ``Reachability Analysis for a Class of Petri Nets," Proceedings of CDC 2009, the 2009 IEEE Conference on Decision and Control, pp. 1261-1266, Shanghai, China, 2009 (invited).


12) S. Sundaram and C. N. Hadjicostis, ``Information Dissemination in Networks via Linear Iterative Strategies Over Finite Fields," Proceedings of CDC 2009, the 2009 IEEE Conference on Decision and Control, pp. 3781-3786, Shanghai, China, 2009 (invited, presented by the researcher)).


11) A. Saboori and C. N. Hadjicostis, ``Verification of K-Step Opacity and Analysis of its Complexity," Proceedings of CDC 2009, the 2009 IEEE Conference on Decision and Control, pp. 205-210, Shanghai, China, 2009 (presented by the researcher).


10) Lingxi Li and C. N. Hadjicostis, ``Minimum Initial Marking Estimation in Labeled Petri Nets," Proceedings of ACC 2009, the 2009 American Control Conference, pp. 5000-5005, St. Louis, MS, 2009 (invited).


9) S. Sundaram and C. N. Hadjicostis, ``Linear Iterative Strategies for Transmitting Input Streams in Sensor Networks," Proceedings of MED 2009, the 17th Mediterranean Conference on Control and Automation, pp. 106-111, Thessaloniki, Greece, 2009 (invited, presented by the researcher).


8) A. Saboori and C. N. Hadjicostis, ``Verification of Infinite-Step Opacity and Analysis of its Complexity," Proceedings of DCDS 2009, the Second IFAC Workshop on Dependable Control of Discrete Systems, pp. 51-56, Bari, Italy, 2009 (presented by the researcher). Available online at http://www.ifac-papersonline.net/Detailed/42295.html .


7) Yu Ru, M. P. Cabasino, A. Giua, and C. N. Hadjicostis, ``Supervisor Synthesis for Discrete Event Systems with Arbitrary Forbidden State Specifications," Proceedings of CDC 2008, the 47th IEEE Conference on Decision and Control, pp. 1048-1053, Cancun, Mexico, 2008.


6) E. Athanasopoulou and C. N. Hadjicostis, ``Probability of Error Bounds for Failure Diagnosis and Classification in Hidden Markov Models," Proceedings of CDC 2008, the 47th IEEE Conference on Decision and Control, pp. 1477-1482, Cancun, Mexico, 2008 (presented by the researcher).


5) A. Saboori and C. N. Hadjicostis, ``Opacity-Enforcing Supervisory Strategies for Secure Discrete Event Systems," Proceedings of CDC 2008, the 47th IEEE Conference on Decision and Control, pp. 889-894, Cancun, Mexico, 2008 (presented by the researcher).


4) Tung Le and C. N. Hadjicostis, ``Low-Complexity Max-Product Algorithms for Problems of Multiple Fault Diagnosis,'' Proceedings of ICARCV 2008, the 10th International Conference on Control, Automation, Robotics and Vision, pp. 470-475, Hanoi, Vietnam, 2008.


3) A. Saboori and C. N. Hadjicostis, ``Verification of Initial-State Opacity in Security Applications of DES," Proceedings of WODES 2008, the 9th International Workshop on Discrete Event Systems, pp. 328-333, Goteborg, Sweden, 2008 (presented by the researcher).


2) Yu Ru and C. N. Hadjicostis, ``Fault Diagnosis in Discrete Event Systems Modeled by Petri Nets with Outputs," Proceedings of WODES 2008, the 9th International Workshop on Discrete Event Systems, pp. 443-448, Goteborg, Sweden, 2008 (invited, presented by the researcher).


1) M. P. Cabasino, A. Giua, C. N. Hadjicostis, and C. Seatzu, ``Fault Model Identification with Petri Nets," Proceedings WODES 2008, the 9th International Workshop on Discrete Event Systems, pp.455-461, Goteborg, Sweden, 2008 (invited).