Joon Lyou

A new sensorless drive scheme for a BLDC motor based on the terminal voltage difference

This paper presents a new sensorless drive scheme for a brushless DC (BLDC) motor based on the terminal voltage difference. Unlike the zero crossing point (ZCP) of the phase back electro-motive force (BEMF) which has been used in the conventional sensorless drive schemes, the ZCP of the BEMF difference between two phases corresponds to the commutation point of a BLDC motor accurately. So as to detect the ZCP and adopt it to the BLDC motor commutation, a circuit which constitutes of a differential amplifier and a comparator is designed. Some experimental results show that the output of the suggested circuit is analogous to the hall sensor signal and it can be used for BLDC motor sensorless drive.

Neural Network Based Terrain Classification Using Wavelet Features

Terrain perception technology using passive sensors plays a key role in enhancing autonomous mobility for military unmanned ground vehicles in off-road environments. In this paper, an effective method for classifying terrain cover based on color and texture features of an image is presented. Discrete wavelet transform coefficients are used to extract those features. Furthermore, spatial coordinates, where a terrain class is located in the image, are also adopted as additional features. Considering real-time applications, we applied a neural network as classifier and it is trained using real off-road terrain images. Through comparison of the classification performance according to applied feature sets and color space changes, we can find that the feature vectors with spatial coordinates extracted using the Daub2 wavelet in the HSI color space have the best classification performance. Experiments show that using the wavelet features and spatial coordinates features improves the terrain cover classification performance. The proposed algorithm has a promising results and potential applications for autonomous navigation.

An error compensation method for transfer alignment

This paper deals with the transfer alignment problem of SDINS (StrapDown Inertial Navigation System) subjected to roll and pitch motions of the ship. Specifically, to reduce alignment errors induced by measurement time-delay and ship body flexure, an error compensation method is deviced based on delay state augmentation and DCM (Direction Cosine Matrix) partial matching. A linearized error model for the velocity and attitude matching transfer alignment system is first derived by linearizing the nonlinear measurement equation with respect to its time delay and augmenting the delay state into the conventional linear state equations. And then DCM partial matching is properly combined to reduce effects of a ships Y axis flexure. The simulation results show that the present method is effective enough resulting in considerably less azimuth alignment errors.

The role of an amorphous carbon layer on a multi-wall carbon nanotube attached atomic force microscope tip in making good electrical contact to a gold electrode

Multi-wall carbon nanotube (MWNT) attached atomic force microscope (AFM) tips (MWNT tips) have good potential for use in AFM lithography. Good conducting MWNT tips are needed in such applications. However, characterizing the conductance of MWNT tips is nontrivial: making a good electrical contact between the MWNT and electrode is difficult. We observed that MWNT tips produced by hydrocarbon-deposition attachment usually do not make good electrical contacts to gold electrodes because of the thin and rough amorphous carbon layer on the MWNT that was unintentionally deposited during the attachment. We found that good contacts can be made if a more amorphous carbon layer is deposited to form a thick and smooth amorphous carbon layer on MWNTs. Good contact was made either by transformation of the amorphous carbon layer into a conducting or peel-off layer, exposing the bare MWNT surface. MWNT tips with an exposed MWNT surface showed the well-known high-current-flowing capacity and the stepped-cutting behavior of bare MWNTs. The peeling-off behavior of a thick amorphous carbon layer may be utilized in producing bare-surfaced MWNT tips that have good conductance and therefore are useful for applications.

Reliability Analysis of Safety Grade Programmable Logic Controller

This paper focuses on the random hardware failures necessary for the safety assessment of the reactor protection system (RPS). A prediction method of the hardware failure rate for safety assessment is suggested, and applied to the safety grade programmable logic controller (PLC) to identify design weak points from a safety point of view

A practical collision-free trajectory planning for two robot systems

A practically applicable collision-free trajectory planning technique for two robot systems is proposed. The robot trajectories considered in this work are composed of many segments between which the robots stop to assemble, weld, or do other jobs by end-effector. The proposed method is based on the planning-coordination decomposition approach in which planning finds the trajectory of each robot independently according to their tasks and coordination finds velocity modification to avoid collision with each other. To fully utilize the convenience of independent trajectory planning and to ensure no geometrical path change after coordination, a simple technique avoiding collision by adding least delay-time in the local sense before moving along the next path-segment is developed. The least delay time is determined by a graphical method on the space called co-ordination space where collision between two robots and coordination of two robots are easily visualized.

Evaluation of carbon nanotube probes in critical dimension atomic force microscopes

Abstract. The decreasing size of semiconductor features and the increasing structural complexity of advanced devices have placed continuously greater demands on manufacturing metrology, arising both from the measurement challenges of smaller feature sizes and the growing requirement to characterize structures in more than just a single critical dimension. For scanning electron microscopy, this has resulted in increasing sophistication of imaging models. For critical dimension atomic force microscopes (CD-AFMs), this has resulted in the need for smaller and more complex tips. Carbon nanotube (CNT) tips have thus been the focus of much interest and effort by a number of researchers. However, there have been significant issues surrounding both the manufacture and use of CNT tips. Specifically, the growth or attachment of CNTs to AFM cantilevers has been a challenge to the fabrication of CNT tips, and the flexibility and resultant bending artifacts have presented challenges to using CNT tips. The Korea Research Institute for Standards and Science (KRISS) has invested considerable effort in the controlled fabrication of CNT tips and is collaborating with the National Institute of Standards and Technology on the application of CNT tips for CD-AFM. Progress by KRISS on the precise control of CNT orientation, length, and end modification, using manipulation and focused ion beam processes, has allowed us to implement ball-capped CNT tips and bent CNT tips for CD-AFM. Using two different generations of CD-AFM instruments, we have evaluated these tip types by imaging a line/space grating and a programmed line edge roughness specimen. We concluded that these CNTs are capable of scanning the profiles of these structures, including re-entrant sidewalls, but there remain important challenges to address. These challenges include tighter control of tip geometry and careful optimization of scan parameters and algorithms for using CNT tips.

Terrain cover classification based on wavelet feature extraction

The terrain perception technology using passive sensors plays a key role to enhance autonomous mobility for military UGV(unmanned ground vehicle) in off-road environment. In this paper, an effective method is presented to classify terrain cover based on the color and texture features of an image. Coefficients from the discrete wavelet transform are used to extract the color and texture features of the image. Furthermore, spatial coordinates where a terrain class is located in the image are also adopted as additional features. Considering real-time applications, the neural network is applied for the terrain classifier to be trained using real off-road terrain images. By comparing the classification performance according to the applied feature sets and its color space change, the experimental results show that the proposed algorithm has a promising result and potential possibilities for autonomous navigation.

On-line Magnetic Distortion Calibration Method for a Magnetometer

This paper describes an on-line magnetic distortion calibration procedure for a magnetometer. The horizontal magnetic field is calculated through the earth magnetic field sensed by 3-axes magnetometer. The ellipse equation is derived from a set of horizontal magnetic field data using least square method and calibration parameters are determined. The calibration process is performed iteratively until parameters are not renewed, and experimental results show the effectiveness of the devised method.

Digital image stabilization using simple estimation of the rotational and translational motion

This paper presents a rotational motion estimation and correction technique for digital image stabilization. An equivalent rotation model is derived so as to accommodate a combined rotational and the translational motion. Based on this model, the rotation center and angle are estimated, and followed by the motion compensation. The suggested estimation algorithm does not require the time consuming parameter searching, while showing a comparable performance to the previous ones.