Role of a buried indium zinc oxide layer in the performance enhancement of triboelectric nanogenerators

Park, Daehoon,Lee, Sol,Anh, Cao Viet,Park, Pangun,Nah, Junghyo Elsevier 2019 Nano energy Vol.55 No.-

<P><B>Abstract</B></P> <P>Generally, triboelectric generators (TENGs) demonsrate a considerably lower output current than output voltage; this has largely limited their performance enhancement. Thus, enormous research efforts have been made to address this problem. In this work, we present a simple method to enhance the triboelectric output current by burying an indium zinc oxide (IZO) layer under the triboelectric polymer friction layer. The IZO layer provides large interface density of states, which function as a charge reservoir. During frictional contact-separation motion of the TENG, electrons can be stored in or pumped out of these states. By optimizing the properties of the IZO layer, the output performance of the TENG is greatly improved, generating an output power density of ~ 25 mW/cm<SUP>2</SUP>. Specifically, an output voltage and current density of ~ 140 V and ~ 180 μA/cm<SUP>2</SUP> were obtained, which are 4-fold and 9-fold higher, respectively, than a TENG without an IZO layer. The method introduced here suffers less from friction layer wear-out and can effectively enhance the performance of TENGs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We report the performance enhancement of TENG by burying a metal oxide semiconductor (IZO) under the frictional surface, which contributes substantial increase of output current </LI> <LI> The roles of a buried IZO layer on the performance enhancement of TENG were investigated. </LI> <LI> The optimal composition and fabrication process of the IZO layer were determined for the TENG. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

High Confidence Networked Control for Next Generation Air Transportation Systems

Park, Pangun,Khadilkar, Harshad,Balakrishnan, Hamsa,Tomlin, Claire J. IEEE 2014 IEEE transactions on automatic control Vol.59 No.12

<P>This paper addresses the design of a secure and fault-tolerant air transportation system in the presence of attempts to disrupt the system through the satellite-based navigation system. Adversarial aircraft are assumed to transmit incorrect position and intent information, potentially leading to violations of separation requirements among aircraft. We propose a framework for the identification of adversaries and malicious aircraft, and then for air traffic control in the presence of such deliberately erroneous data. The framework consists of three mechanisms that allow each aircraft to detect attacks and to resolve conflicts: fault detection and defense techniques to improve Global Positioning System (GPS)/inertial navigation, detection and defense techniques using the Doppler/received signal strength, and a fault-tolerant control algorithm. A Kalman filter is used to fuse high frequency inertial sensor information with low frequency GPS data. To verify aircraft position through GPS/inertial navigation, we propose a technique for aircraft localization utilizing the Doppler effect and received signal strength from neighboring aircraft. The control algorithm is designed to minimize flight times while meeting safety constraints. Additional separation is introduced to compensate for the uncertainty of surveillance information in the presence of adversaries. We evaluate the effect of air traffic surveillance attacks on system performance through simulations. The results show that the proposed mechanism robustly detects and corrects faults generated by the injection of malicious data. Moreover, the proposed control algorithm continuously adapts operations in order to mitigate the effects these faults. The ability of the proposed approaches to defend against attacks enables reliable air traffic operations even in highly adversarial surveillance conditions.</P>

Performance Comparison of Industrial Wireless Networks for Wireless Avionics Intra-Communications

Park, Pangun,Chang, Woohyuk IEEE 2017 IEEE communications letters Vol.21 No.1

<P>Recently, the United Nations voted to grant a frequency band for wireless avionics intra-communications (WAICs) to replace the heavy and expensive cables used in aircraft with wireless systems. However, WAICs require extremely low failure probability for the flight certification of the safety-critical avionics applications. Existing industrial wireless networks are possible candidate technologies, since they are designed to meet the high reliability requirement of industrial automation within a harsh environment surrounded by metals. This letter provides a theoretical framework to compare the performance of representative industrial wireless networks against the system requirements of the flight certification. A mathematical model is proposed to evaluate the considered protocols in terms of the deadline missing probability per flight hour. Furthermore, the model is used to derive the maximum allowable packet loss probability while guaranteeing the flight certification.</P>

Hybrid Communication Protocols and Control Algorithms for NextGen Aircraft Arrivals

Pangun Park,Khadilkar, Harshad,Balakrishnan, Hamsa,Tomlin, Claire IEEE 2014 IEEE transactions on intelligent transportation sy Vol.15 No.2

<P>Capacity constraints imposed by current air traffic management technologies and protocols could severely limit the performance of the Next Generation Air Transportation System (NextGen). A fundamental design decision in the development of this system is the level of decentralization that balances system safety and efficiency. A new surveillance technology called automatic dependent surveillance-broadcast (ADS-B) can be potentially used to shift air traffic control to a more distributed architecture; however, channel variations and interference with existing secondary radar replies can affect ADS-B systems. This paper presents a framework for managing arrivals at an airport by using a hybrid centralized/distributed algorithm for communication and control. The algorithm combines the centralized control that is used in congested regions with the distributed control that is used in lower traffic density regions. The hybrid algorithm is evaluated through realistic simulations of operations around a major airport. The proposed strategy is shown to significantly improve air traffic control performance under various operating conditions by adapting to the underlying communication, navigation, and surveillance systems. The performance of the proposed strategy is found to be comparable to fully centralized strategies, despite requiring significantly less ground infrastructure.</P>

Cross-Layer Optimization for Industrial Control Applications Using Wireless Sensor and Actuator Mesh Networks

Park, Pangun,Marco, Piergiuseppe Di,Johansson, Karl Henrik IEEE 2017 IEEE transactions on industrial electronics Vol.64 No.4

<P>When multiple control processes share a common wireless network, the communication protocol must provide reliable performance in order to yield stability of the overall system. In this paper, the novel cross-layer optimized control (CLOC) protocol is proposed for minimizing the worst case performance loss of multiple industrial control systems. CLOC is designed for a general wireless sensor and actuator network where both sensor to controller and controller to actuator connections are over a multihop mesh network. The design approach relies on a constrained max-min optimization problem, where the objective is to maximize the minimum resource redundancy of the network and the constraints are the stability of the closed-loop control systems and the schedulability of the communication resources. The optimal operation point of the protocol is automatically set in terms of the sampling rate, scheduling, and routing, and is achieved by solving a linear programming problem, which adapts to system requirements and link conditions. The protocol has been experimentally implemented and evaluated on a testbed with off-the-shelf wireless sensor nodes, and it has been compared with a traditional network design and a fixed-schedule approach. Experimental results show that CLOC indeed ensures control application stability and fulfills communication constraints while maximizing the worst case redundancy gain of the system performance.</P>

제어 시스템을 위한 MIMO 무선 연산

박판근(Pangun Park),김선(Seon Kim),나정효(Junghyo Nah) 한국정보통신학회 2023 한국정보통신학회논문지 Vol.27 No.3

최근 제안된 MIMO-AirComp (Multiple input multiple output over-the-air computation) 기술은 무선 통신과 컴퓨팅 자원을 효율적으로 통합하기 위하여 다중 액세스 채널의 중첩 속성을 활용한다. 본 논문에서는 제어 시스템의 제어 신호를 추정하기 위한 MIMO-AirComp 프레임워크를 제안한다. 제시된 MIMO-AirComp 프레임워크는 센서의 측정 정보 전처리, 무선 채널의 협업 중첩, 제어기의 수신 신호 후처리 기능으로 구성된다. 시뮬레이션을 활용한 성능평가를 통하여, 제안된 MIMO-AirComp가 기존 방식에 비하여 제어 신호 처리량을 향상 시켜 제어 시스템의 성능을 개선하는 것을 보여 주었다. 특히, 제안된 MIMO-AirComp 기법은 다수의 고잡음 무선 센서로 구성된 제어 시스템에서 기존의 분리된 무선 통신 및 컴퓨팅 설계 방식으로는 불가하였던 시스템의 안정성을 보장하였다. The recently proposed technique, multiple input multiple output over-the-air computation (MIMO-AirComp), leverages the superposition property of the multiple access channel to efficiently integrate the communication and computation. This article proposes the MIMO-AirComp framework to compute the control signal of control systems. The proposed framework efficiently computes the target control signal by coordinating local pre-processing at each node, aggregation through the wireless channel, and post-processing at the controller. The simulation results show that the proposed MIMO-AirComp framework considerably improves the control performance by increasing the computation throughput compared to the conventional separated communication and computation approach. The proposed scheme with many nodes essentially suppresses the noise impact of both the wireless channel and the measurement, while the conventional one only reduces the impact of the channel noise. Specifically, the proposed scheme guarantees control stability in a network composed of high-noise wireless sensors, which is infeasible with the conventional approach.

항공기내 무선 네트워크 구축 연구

박판근(Pangun Park),정방철(Bang Chul Jung),반태원(Tae-Won Ban),장우혁(Woohyuk Chang) 한국항공우주학회 2017 한국항공우주학회 학술발표회 논문집 Vol.2017 No.4

Traffic Generation Rate Control of Wireless Sensor and Actuator Networks

IEEE 2015 IEEE COMMUNICATIONS LETTERS Vol.19 No.5

<P>The traffic generation rate of the network used for cyber-physical systems is a crucial design parameter since it directly affects the stability of physical systems and the congestion level of communication systems. In this paper, we propose a novel modeling framework of the general wireless sensor and actuator networks of cyber-physical systems where the sensor-controller and controller-actuator sides communicate over a lossy network. The performance model is then used to derive the optimal traffic generation rate of sensors and controllers for minimizing the maximum outage probability of the stability constraint of the control systems while guaranteeing a schedulability constraint. The resulting problem is a non-linear optimization problem which allows to obtain the global optimum. An efficient approximation converts the proposed optimization problem into a linear programming problem. One interesting finding is that the optimal solution assigns higher traffic generate rate on the controller-actuator link compared to the one of the sensor-controller link since the actuating-link is more critical to guarantee the stability of the control systems.</P>

Power controlled fair access protocol for wireless networked control systems

Springer-Verlag 2015 WIRELESS NETWORKS Vol.21 No.5

네트워크 제어 시스템을 위한 최적화된 매체 접근 확률

박판근,Park, Pangun 한국정보통신학회 2015 한국정보통신학회논문지 Vol.19 No.10

Distributed Networked Control Systems (NCSs) through wireless networks have a tremendous potential to improve the efficiency of various control systems. In this paper, we define the State Update Interval (SUI) as the elapsed time between successful state vector reports derived from the NCSs. A simple expression of the SUI is derived to characterize the key interactions between the control and communication layers. This performance measure is used to formulate a novel optimization problem where the objective function is the probability to meet the SUI constraint and the decision parameter is the channel access probability. We prove the existence and uniqueness of the optimal channel access probability of the optimization problem. Furthermore, the optimal channel access probability for NCSs is lower than the channel access probability to maximize the throughput. Numerical results indicate that the improvement of the success probability to meet the SUI constraint using the optimal channel access probability increases as the number of nodes increases with respect to that using the channel access probability to maximize the throughput. 무선 네트워크를 통한 네트워크 제어 시스템 (NCS: Networked Control Systems)은 다양한 제어 시스템의 효율성을 극대화 할 수 있는 잠재력을 가지고 있다. 본 연구에서는 네트워크 제어 시스템으로부터 이끌어낸 상태갱신주기(SUI: State Update Interval)라는 성능 메트릭을 정의한다. 제시된 상태갱신주기는 제어와 통신 시스템 계층 사이의 핵심적인 상호작용을 포함하고 있다. 제시된 성능 메트릭은 NCS를 위한 최적화 문제를 도출하는데 사용이 되었으며, 이러한 최적화 문제의 목적 함수는 상태갱신주기의 제한 요소를 만족하는 확률이며 변수는 매체접근 확률로 표현되었다. 본 연구에서는 제시된 최적화 문제의 최적 매체접근 확률이 유일한 해를 가진다는 것을 증명하였다. 또한 NCS를 위한 최적의 매체접근 확률은 전송률을 극대화하는 기존의 매체접근 확률보다 낮다는 결론을 도출하였다. 성능 분석 결과를 통하여 시스템의 안정도가 상태갱신주기를 고려한 최적의 매체접근 확률을 사용하였을 때가 전송률을 최대화하는 매체접근 확률을 사용 했을 때 보다 높다는 점을 보였다.