• Journal of Information Processing Systems
• /
• 제16권5호
• /
• pp.1158-1168
• /
• 2020

The distance vector-hop wireless sensor node location method is one of typical range-free location methods. In distance vector-hop location method, if a wireless node A can directly communicate with wireless sensor network nodes B and C at its communication range, the hop count from wireless sensor nodes A to B is considered to be the same as that form wireless sensor nodes A to C. However, the real distance between wireless sensor nodes A and B may be dissimilar to that between wireless sensor nodes A and C. Therefore, there may be a discrepancy between the real distance and the estimated hop count distance, and this will affect wireless sensor node location error of distance vector-hop method. To overcome this problem, it proposes a wireless sensor network node location method by modifying the method of distance estimation in the distance vector-hop method. Firstly, we set three different communication powers for each node. Different hop counts correspond to different communication powers; and so this makes the corresponding relationship between the real distance and hop count more accurate, and also reduces the distance error between the real and estimated distance in wireless sensor network. Secondly, distance difference between the estimated distance between wireless sensor network anchor nodes and their corresponding real distance is computed. The average value of distance errors that is computed in the second step is used to modify the estimated distance from the wireless sensor network anchor node to the unknown sensor node. The improved node location method has smaller node location error than the distance vector-hop algorithm and other improved location methods, which is proved by simulations.

• Smart Structures and Systems
• /
• 제6권5_6호
• /
• pp.689-709
• /
• 2010

In this paper, a low cost, low power but multifunctional wireless sensor node is presented for the impedance-based SHM using piezoelectric sensors. Firstly, a miniaturized impedance measuring chip device is utilized for low cost and low power structural excitation/sensing. Then, structural damage detection/sensor self-diagnosis algorithms are embedded on the on-board microcontroller. This sensor node uses the power harvested from the solar energy to measure and analyze the impedance data. Simultaneously it monitors temperature on the structure near the piezoelectric sensor and battery power consumption. The wireless sensor node is based on the TinyOS platform for operation, and users can take MATLAB$^{(R)}$ interface for the control of the sensor node through serial communication. In order to validate the performance of this multifunctional wireless impedance sensor node, a series of experimental studies have been carried out for detecting loose bolts and crack damages on lab-scale steel structural members as well as on real steel bridge and building structures. It has been found that the proposed sensor nodes can be effectively used for local wireless health monitoring of structural components and for constructing a low-cost and multifunctional SHM system as "place and forget" wireless sensors.

• 한국산학기술학회:학술대회논문집
• /
• 한국산학기술학회 2009년도 추계학술발표논문집
• /
• pp.190-193
• /
• 2009

무선 센서 네트워크에서 가장 중요하고 기본적인 요소는 환경 정보를 수집하고 이를 사용자 응용시스템에 전송하는 무선 센서 노드이다. 무선 센서 노드는 센서로 환경 정보를 수집하고 이를 저장, 가공하여 처리된 데이터를 사용자에게 전송하는 무선 송수신 장치로 기술의 발전에 따라 소형화, 지능화되고 있다. 특히 마이크로컨트롤러, RF 모듈, 메모리 등을 하나의 칩 내부에 모두 통합하는 SoC(System-on-Chip)기술은 센서 노드의 소형화와 제조 단가를 낮추는데 중요한 역할을 한다. 본고에서는 상용 SoC를 사용하여 무선 센서 네트워크를 위한 소형 무선 센서 노드를 설계하였으며 이를 이용한 여러 활용 방안 및 추가적인 고려사항에 대하여 논하였다.

• 전기학회논문지
• /
• 제59권7호
• /
• pp.1302-1308
• /
• 2010

In this study, Zigbee Sensor Node to transmit harmful gases CO and $CO_2$ information using wireless communication within the ground and underground structures were developed. Wireless communication protocol was used Zigbee Stack included IEEE 802. 15.4 MAC protocol. For wireless transmission of detected harmful gas signal from ADC of MCU was implemented Zigbee Sensor Node that was developed protocol using Serial-Port-Profile(SPP) here. The proposed Zigbee Sensor Node was verified transmission distance from experiments. Transmission distance was into 90m in experiments. Distance experiments were measured at 10m intervals using sine & pulse wave input signal at indoors. The proposed Route Sensor Node was applied mesh routing protocol. When built up USN(Ubiquitous Sensor Network)using Route Sensor Node, transmission distance was not limited. On the experimental results, harmful gas values between direct measurements and USN measurements were consistent. The semiconductor CO sensor and N-DIR $CO_2$ sensor module as a harmful sensor was used. Therefore, the proposed Zigbee Sensor Node was verified about reliability and validity to build USN for transmission of harmful gas information.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제7권5호
• /
• pp.998-1013
• /
• 2013

Wireless wearable sensor networks have emerged as a promising technique for human motion tracking due to the flexibility and scalability. In such system several wireless sensor nodes being attached to human limb construct a wearable sensor network, where each sensor node including MEMS sensors (such as 3-axis accelerometer, 3-axis magnetometer and 3-axis gyroscope) monitors the limb orientation and transmits these information to the base station for reconstruction via low-power wireless communication technique. Due to the energy constraint, the high fidelity requirement for real time rendering of human motion and tiny operating system embedded in each sensor node adds more challenges for the system implementation. In this paper, we discuss such challenges and experiences in detail during the implementation of such system with wireless wearable sensor network which includes COTS wireless sensor nodes (Imote 2) and uses TinyOS 1.x in each sensor node. Since our system uses the COTS sensor nodes and popular tiny operating system, it might be helpful for further exploration in such field.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 2011년도 정기 학술대회
• /
• pp.36-39
• /
• 2011

In this paper, performance of EMI interface and multi-channel wireless impedance sensor node is evaluated for SHM on bolted connection. To achieve the objective, following approaches are implemented. Firstly, an interface washer is designed to monitor loosened bolt through the variation in EMI of interface washer due to change in preload in bolt. Secondly, a multi-channel wireless impedance sensor node based on Imote2 platform is designed for automated and cost-efficient impedance-based SHM on bolted connections. Finally, performance of the multi-channel wireless impedance sensor node and the interface washer are experimentally validated for a lab-scale bolted connection model. A damage monitoring method using RMSD index of EMI signatures is utilized to examine the strength of each individual bolted connection.

• 전자공학회논문지CI
• /
• 제44권5호
• /
• pp.28-37
• /
• 2007

IEEE 1451 standard는 네트워크와 transducer간에 표준 interface를 정의한다. 본 논문에서는 IEEE 1451 Standard 기반의 data acquisition system과 무선 smart sensor node를 구성하기 위한 구조적인 모델을 제안한다. 제안 된 Network Capable Application Processor(NCAP)은 data acquisition의 역할과 smart sensor node와 네트워크 사이에 가교 역할을 한다. 또한 무선 sensor node에게 영향을 주지 않으면서 재구성이 가능하고 DB를 이용하여 transducer의 정확한 정보를 얻는다. Smart sensor node는 그 자신에 관한 기본적인 정보를 디지털 형식으로 제공하는 능력을 가지고 있다. 이 디지털 형식은 Transducer Electronic Data Sheet(TEDS)라 하며 sensor node의 plug-and-play 기능을 가능하게 한다. IEEE 1451.4에서 정의하고 있는 TEDS와 Template를 무선 환경에서 적용하기 위해 형식을 간략화 하였으며 ad-hoc routing을 통해 전송이 이루어진다. 본 연구 시스템은 의료정보 서비스를 제공하기 위한 목적으로 체온과 ECG(Electrocardiogram) 센서를 사용하였다. Template 형식은 센서들의 data sheet를 통해 결정하였으며 센서의 특징을 정확히 표현하기 위해 재구성하였다. NCA의 DB는 다양한 센서 개발에 따라 새로운 Template 및 하부 항목의 등록이 가능하도록 구현하였다.

• 한국정보통신학회논문지
• /
• 제15권1호
• /
• pp.227-232
• /
• 2011

현재 무선센서노드 기반의 헬스케어 모니터링 시스템이 활발히 연구되고 있다. 하지만 생체신호의 모니터링을 위한 전체 데이터의 전달은 무선센서네트워크 내의 데이터 트래픽과 에너지 소모가 증가하게 된다. 본 연구에서는 경량의 전처리 과정 및 알고리즘을 통해 ECG신호에서 의미있는 파라미터만을 검출하여 전송하였다. 본 연구에서는 정상적인 ECG에서 무선센서노드에서 R피크, RR간격을 검출할 수 있는 TinyOS 기반 어플리케이션을 구현하였으며 결과로 dECG, R피크, RR간격, HRV를 그래프로 확인 할 수 있었다. 따라서 본 연구를 이용하면 ECG신호 전체 데이터가 아닌 주요 정보만을 보냄으로서 에너지 소모, 데이터량을 줄일 수 있다.

• Journal of Computing Science and Engineering
• /
• 제9권4호
• /
• pp.163-176
• /
• 2015

Self-organization of distributed wireless sensor nodes is a critical issue in wireless sensor networks (WSNs), since each sensor node has limited energy, bandwidth, and scalability. These issues prevent sensor nodes from actively collaborating with the other types of sensor nodes deployed in a typical heterogeneous and somewhat hostile environment. The automated self-organization of a WSN becomes more challenging as the number of sensor nodes increases in the network. In this paper, we propose a dynamic self-organized architecture that combines tree topology with a drawn-grid algorithm to automate the self-organization process for WSNs. In order to make our proposed architecture scalable, we assume that all participating active sensor nodes are unaware of their primary locations. In particular, this paper presents two algorithms called active-tree and drawn-grid. The proposed active-tree algorithm uses a tree topology to assign node IDs and define different roles to each participating sensor node. On the other hand, the drawn-grid algorithm divides the sensor nodes into cells with respect to the radio coverage area and the specific roles assigned by the active-tree algorithm. Thus, both proposed algorithms collaborate with each other to automate the self-organizing process for WSNs. The numerical and simulation results demonstrate that the proposed dynamic architecture performs much better than a static architecture in terms of the self-organization of wireless sensor nodes and energy consumption.

• Smart Structures and Systems
• /
• 제6권5_6호
• /
• pp.661-673
• /
• 2010

This paper presents recent developments in an extremely compact, wireless impedance sensor node (the WID3, $\underline{W}$ireless $\underline{I}$mpedance $\underline{D}$evice) for use in high-frequency impedance-based structural health monitoring (SHM), sensor diagnostics and validation, and low-frequency (< ~1 kHz) vibration data acquisition. The WID3 is equipped with an impedance chip that can resolve measurements up to 100 kHz, a frequency range ideal for many SHM applications. An integrated set of multiplexers allows the end user to monitor seven piezoelectric sensors from a single sensor node. The WID3 combines on-board processing using a microcontroller, data storage using flash memory, wireless communications capabilities, and a series of internal and external triggering options into a single package to realize a truly comprehensive, self-contained wireless active-sensor node for SHM applications. Furthermore, we recently extended the capability of this device by implementing low-frequency analog-to-digital and digital-to-analog converters so that the same device can measure structural vibration data. The compact sensor node collects relatively low-frequency acceleration measurements to estimate natural frequencies and operational deflection shapes, as well as relatively high-frequency impedance measurements to detect structural damage. Experimental results with application to SHM, sensor diagnostics and low-frequency vibration data acquisition are presented.