List of English Publication

@inproceedings{nokey,

title = {Conversion of Controllers to Have Integer State Matrix for Encrypted Control: Non-Minimal Order Approach},

author = {Joowon Lee and Donggil Lee and Seungbeom Lee and Junsoo Kim and Hyungbo Shim},

url = {https://ieeexplore.ieee.org/abstract/document/10383200},

doi = {10.1109/CDC49753.2023.10383200},

isbn = {979-8-3503-0124-3},

year  = {2023},

date = {2023-12-14},

urldate = {2023-12-14},

booktitle = {2023 62nd IEEE Conference on Decision and Control (CDC)},

pages = {5091-5096},

publisher = {IEEE Control Systems Society},

address = {Marina Bay Sands, Singapore},

abstract = {To implement an encrypted dynamic controller based on homomorphic encryption that operates for an infinite time horizon, it is essential for every component of the controller's state matrix to be an integer. In this paper, we tackle the challenge of converting a pre-designed controller into a new one with an integer state matrix while preserving its control performance in the closed-loop system. This enables encrypted dynamic systems to be realized without re-encryption and approximation of control parameters, compared to the previous results. To achieve this, we propose two approaches and provide sufficient conditions on the design parameter for each. The first approach is to design the new controller as an estimator of the original closed-loop system, and the conditions on the estimator gain are derived. Our second approach is to formulate a problem of finding certain polynomials, whose solution leads to the design of the new controller. In a special case when the numerator of the plant transfer function is a constant, we provide a constructive method to obtain such solution.},

keywords = {Controller encryption, Homomorphic encryption, Linear Systems},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{nokeyt,

title = {Data-Driven Inverse of Linear Systems and Application to Disturbance Observer},

author = {Yongsoon Eun and Jaeho Lee and Hyungbo Shim},

url = {https://ieeexplore.ieee.org/document/10156256},

doi = {10.23919/ACC55779.2023.10156256},

isbn = {979-8-3503-2806-6},

year  = {2023},

date = {2023-05-31},

booktitle = {2023 American Control Conference (ACC)},

pages = {2806-2811},

publisher = {IEEE},

address = {San Diego, CA, USA},

abstract = {This work develops a data-based construction of inverse dynamics for LTI systems. Specifically, the problem addressed here is to find an input sequence from the corresponding output sequence based on pre-collected input and output data. The problem can be considered as a reverse of the recent use of the behavioral approach, in which the output sequence is obtained for a given input sequence by solving an equation formed by pre-collected data. The condition under which the problem gives a solution is investigated and turns out to be L-delay invertibility of the plant and a certain degree of persistent excitation of the data input. The result is applied to form a data-driven disturbance observer. The plant dynamics augmented by the data-driven disturbance observer exhibits disturbance rejection without the model knowledge of the plant.},

keywords = {Data-driven control, Disturbance observer, Disturbance rejection, Linear Systems},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{KimLeeLeeShimSeo18,

title = {Local Identification of Sensor Attack and Distributed Resilient State Estimation for Linear System},

author = {Junsoo Kim and Jin Gyu Lee and Chanhwa Lee and Hyungbo Shim and Jin H. Seo},

doi = {10.1109/CDC.2018.8619126},

year  = {2018},

date = {2018-12-17},

booktitle = {Proc. of 2018 IEEE 57th Conference on Decision and Control},

pages = {2056-2061},

publisher = {IEEE},

address = {Miami, USA},

abstract = {This paper presents a distributed attack-resilient state estimation scheme for continuous-time linear systems having redundant sensors when some of them are corrupted by adversaries. We first design a distributed state observer so that individual observers from each of output measurements communicate with their neighbors and cooperate to recover the full state of the system. Then, the observers are partitioned into disjoint groups and local monitoring systems are designed for each of them. Even though the system is not observable from measurements in each group, every influential attack is detected and identified by local monitors using only local information and local observer estimates within the local group, with the help of sensing redundancy. In process of local attack identification, a notion of sensor attack identifiability is introduced which does not require observability. Finally, all corrupted output measurements are removed from the observer communication and the distributed resilient state estimation is achieved},

keywords = {Linear Systems},

pubstate = {published},

tppubtype = {inproceedings}

}