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Indoor Dead Reckoning Localization Using Ultrasonic Anemometer with IMU
Seo, Woojin,Baek, Kwang-Ryul Hindawi Limited 2017 Journal of sensors Vol.2017 No.-
<P>Dead reckoning is an important aspect of estimating the instantaneous position of a mobile robot. An inertial measurement unit (IMU) is generally used for dead reckoning because it measures triaxis acceleration and triaxis angular velocities in order to estimate the position of the mobile robot. Positioning with inertial data is reasonable for a short period of time. However, the velocity, position, and attitude errors increase over time. Much research has been conducted in ways to reduce these errors. To position a mobile robot, an absolute positioning method can be combined with dead reckoning. The performance of a combined positioning method can be improved based on improvement in dead reckoning. In this paper, an ultrasonic anemometer is used to improve the performance of dead reckoning when indoors. A new approach to the equation of an ultrasonic anemometer is proposed. The ultrasonic anemometer prevents divergence of the mobile robot’s velocity. To position a mobile robot indoors, the ultrasonic anemometer measures the relative movement of air while the robot moves through static air. Velocity data from the ultrasonic anemometer and the acceleration and angular velocity data from the IMU are combined via Kalman filter. Finally we show that the proposed method has the performance with a positioning method using encoders on a good floor condition.</P>
서우진(Woojin Seo),한광일(Kwang-Il Han),백광렬(Kwang-Ryul Baek) 제어로봇시스템학회 2017 제어·로봇·시스템학회 논문지 Vol.23 No.1
This paper presents a positioning method using range-based Bluetooth RSSI data and odometry data for a mobile robot. These days, Bluetooth beacons are widely used for various applications which are based on both location and environmental information. There are two localization methods: a range-free method called the ‘fingerprint method’ and a range-based method called the ‘triangulation method’. Because of the Bluetooth RSSI resolution, most researches are using the fingerprint method. In this paper, the localization method, which uses odometry data and range-based Bluetooth RSSI data, is proposed. The range data from Bluetooth RSSI is directly used without triangulation. Also, the particle filter is adopted to combine the odometry data with the range data from Bluetooth RSSI. The performance of the proposed method is evaluated by simulations and experiments.
Woojin Choi,Hojin Ryu,Namcheol Jeon,Minseong Lee,Ho-Young Cha,Kwang-Seok Seo IEEE 2014 IEEE electron device letters Vol.35 No.1
<P>In this letter, reduction of threshold voltage instability in gate recessed normally-off GaN metal insulator semiconductor high electron mobility transistors with SiN<SUB>x</SUB> gate insulator was investigated. A plasma enhanced atomic layer deposition technique was successfully employed for very thin SiN<SUB>x</SUB> (5 nm) as an interfacial layer. The hysteresis and drift of threshold voltage in transfer curve and the forward biased gate leakage current were effectively reduced.</P>
Combined Dithered Sigma-Delta Modulation based Random PWM Switching Scheme
Seo-Hyeong Kim,Woojin Choi,Sewan Choi,Kyo-Beum Lee 전력전자학회 2009 JOURNAL OF POWER ELECTRONICS Vol.9 No.5
The PWM (Pulse Width Modulation) control signals have a drawback in that their power spectrum tends to be concentrated around the switching frequency and the resulting harmonic spikes cause an EMI (Electromagnetic Interference) and switching losses in semiconductors, etc. The SDM (Sigma-Delta Modulation) is a type of switching modulation used to reduce these harmonic spikes, and several SDM schemes are investigated in this paper. In the DSDM (Dithered SDM), the SDSDM (Space-Dithered SDM) and TDSDM (Time-Dithered SDM), the signals are classified by the location of their random dither additions. In these schemes, the switching frequency is spread by a random dither generator placed on the input or the output parts. Experimental results are presented where the advantages of the new proposed CDSDM (Combined Dithered SDM) are confirmed by applying to a buck converter.
Woojin Jo,Seok-Jun Seo 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.2
Korea Atomic Energy Research Institute (“KAERI”) has been developing various studies related to the nuclear fuel cycle. Among them, KAERI was focusing on the pyroprocess, which recycles some useful elements white reducing the volume and toxicity of spent nuclear fuel (SNF). Pyroprocess involves the handling of SNF, which cannot be handled directly by the facility worker. Therefore, SNF is handled and processed through remote handling device within a shielded facility such as a hot cell. Nuclear Facilities with such hot cells are called nuclear fuel cycle facilities, and unlike other facilities, heating, ventilating, and air conditioning (HVAC) system are particularly important in nuclear fuel cycle facilities to maintain the atmosphere in the hot cell and remove radioactive materials. In addition, due to the nature of the pyroprocess, which uses molten salt, corrosion is a problem in air atmosphere, so the process can only be carried out in an inert gas atmosphere. KAERI has a nuclear fuel cycle facility called the Irradiation Material Examination Facility (IMEF), and has built and operated the ACPF inside the IMEF, which operates an inert atmosphere hot cell for the demonstration of the pyroprocess. For efficient process development of the pyroprocess, it is necessary to put the developed equipment into the hot cell, which is a radiationcontrolled area, after sufficient verification in a mock-up facility. For this purpose, the ACPF mock-up facility, which simulates the system, space, and remote handling equipment of the ACPF, is operated separately in the general laboratory area. The inert gas conditioning system of the ACPF consists of very complex piping, blowers, and valves, requires special attention to maintenance. In addition, if there is a small leak in the piping within these valves or piping, radioactive materials can be directly exposed to facility workers, so continuous monitoring and maintenance are required to prevent accident. In this study, the applicability of acoustic emission technology and ultrasonic technology for leak detection in the inert gas conditioning system of ACPF mock-up facility was investigated. For this purpose, new bypass pipes and valves were installed in the existing system to simulate the leakage of pipes and valves. Acoustic emission sensors are attached directly to pipes or valves to detect signals, while ultrasonic sensors are installed at a distance to detect signals. The optimal parameters of each technology to effectively suppress background noise were derived and, and the feasibility of identifying normal and abnormal scenarios in the system was analyzed.