권철현 교수

Security of Cyber-Physical Systems (CPS) against cyber attacks is an important yet challenging problem. Since most cyber attacks happen in erratic ways, it is difficult to describe them systematically. In this paper, instead of identifying a specific cyber attack model, we are focused on analyzing the system's response during cyber attacks. Deception attacks (or false data injection attacks), which are performed by tampering with system components or data, are not of particular concern if they c

This technical note proposes an algorithm to assess the safety of the cyber-physical system (CPS) in the presence of cyber attacks, which can be designed intelligently to avoid the detection. The main idea is based on the reachability analysis that computes the reachable set of CPS states possibly reached by all potential cyber attacks regardless of their detection. The reachable set computation typically demands a large computation cost and has mostly relied on the (over) approximation techniqu

Cyber security has emerged as one of the most important issues in unmanned aerial systems for which the functionality heavily relies on onboard automation and intervehicle communications. In this paper, potential cyber threats and vulnerabilities in the unmanned aerial system’s state estimator to stealthy cyber attacks are identified, which can avoid being detected by the monitoring system. Specifically, this paper investigates the worst stealthy cyber attack that can maximize the state estimati

This study considers robust controller design for cyber–physical systems (CPSs) subject to cyber attacks. While previous studies have investigated secure control by assuming specific attack strategies, in this study the authors propose a robust hybrid control scheme containing multiple sub‐controllers, each matched to a different type of cyber attack. A system using this control scheme is able to adapt its behaviour to various cyber attacks (including those which have not been specifically addre

As unmanned aircraft systems become an increasingly integral part of a wide range of applications, ensuring the security of these systems against malicious cyber attacks is a very important concern. To address this problem, this paper considers a controls domain approach extending beyond the computing resources of the unmanned aircraft system to include the underlying physical behavior of the compromised system, successfully complementing the traditional computer security architecture. Specifica

Distributed estimation has proven to be suitable for many multiagent system (MAS) applications, yet it relies heavily on information exchange via a costly and vulnerable communication network. This paper proposes a sensing-based distributed estimation algorithm that enables a local monitoring agent to expand its estimation capabilities beyond its sensing range without needing communication overhead. The key to expanding the limited sensing range is to incorporate the MAS's cooperative control pr

Device to Device (D2D) communication takes advantage of the proximity between the communicating devices in order to achieve efficient resource utilization, improved throughput and energy efficiency, simultaneous serviceability and reduced latency. One of the main characteristics of D2D communication is reuse of the frequency resource in order to improve spectral efficiency of the system. Nevertheless, frequency reuse introduces significantly high interference levels thus necessitating efficient

In this study, the authors consider the distributed state estimation problem of a stochastic linear hybrid system (SLHS) observed over a sensor network. The SLHS is a dynamical system with interacting continuous state dynamics described by stochastic linear difference equations and discrete state (or mode) transitions governed by a Markovian process with a constant transition matrix. Most existing hybrid estimation algorithms are based on a centralised architecture which is not suitable for dist

This paper considers controller design for Cyber-Physical Systems (CPSs) that are robust to various types of cyber attacks. While the previous studies have investigated a secure control by assuming a specific attack strategy, in this paper we propose a hybrid robust control scheme that contains multiple sub-controllers, each matched to a specific type of cyber attacks. Then the system can be adapted to various cyber attacks (including those that are not assumed for sub-controller design) by swit

This paper considers the vehicle positioning problem of an automobile on-board navigation system which is mainly supported by Global Positioning System (GPS). To complement GPS, the existing navigation techniques incorporate additional vehicle sensors, together with the map data to match the positioning solution with the road map. We propose an advanced map-matching algorithm that integrates the additional map data with GPS and vehicle sensor measurements. Specifically, the detailed road map dat

Cyber security has emerged as one of the most important issues in the operation of Unmanned Aerial Systems (UASs) due to their heavy reliance on the on-board autopilot systems. As the first step to implement an autopilot system that is robust to possible cyber attacks, we have conducted a study to identify potential cyber threats and vulnerabilities inherent in the given UASs. In an attempt to study these vulnerabilities in more detail, this paper presents an analytical algorithm to test the beh

Distributed estimation and control schemes play an important role in cooperative Multi-Agent Systems (MASs), addressing various challenges of the insufficient capabilities of individual agents, such as limited sensing ranges. In this paper, we propose an augmented estimation algorithm that enables state estimation of agents which are out of sensing range from a local monitoring agent. The algorithm utilizes the probability of out-of-range agents affecting the behavior of in-range agents; this al

With recent progress in networked embedded control technology, cyber attacks have become one of the major threats to Cyber-Physical Systems (CPSs) due to their close integration of logical and physical processes. Since the conventional computer security techniques are unable to assure the underlying physical behavior against cyber attacks, this paper considers the safety of the compromised CPS from a controls domain perspective. Specifically, we propose an on-line algorithm to assess the safety

This paper presents an integrated control design approach for a class of dynamical systems that satisfy a certain matching condition subject to known input time-delay, unknown parameters, and time-varying disturbances, simultaneously. A novel nonlinear predictor adaptive robust control (PARC) is proposed to track a desired state trajectory. The controller uses predictor-based model compensation to attenuate the effect of input time-delay, gradient type projection with prediction-based learning m

Recently, the technologies of on-device AI have been accelerated with the development of new hardware and software platforms. Therefore, many researchers and engineers focus on how to enable ML technologies on mobile devices with limited hardware resources. In this paper, we revisit on-device ML designed to support ML technologies on mobile devices and describe the three challenges when using on-device ML in detail. Then, we propose a new data management policy, called Overlay-ML, which efficien