• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.19 no.8
• /
• pp.759-763
• /
• 2009

The goal of this study is to examine the effect of the number of slots on the noise from BLDC motors. To this end, the number of poles was fixed to 4 and the number of the slots was set to 6 or 24 before noise was measured. Motors having different numbers of slots showed clear differences in noise. Cogging torque, torque ripple and normal local force were interpreted, analyzed and compared to determine the reason for the differences. To determine the cause of the noise, cogging torque, torque ripple and normal local force were calculated, which are representative noise sources of BLDC motors, and FFT was performed to analyze their frequency components(harmonics). The results show that torque ripple and normal local force were the dominant factors in the noise difference between the 6-slot and 24-pole motors. As the number of the slots increased, the number of harmonics decreased and their amplitude of harmonic were reduced, which was attributed as the reason for the noise differences.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.34 no.4
• /
• pp.242-245
• /
• 2021

In this work, we fabricated oxide on an n-type silicon substrate through local anodic oxidation (LAO) using atomic force microscopy (AFM). The resulting oxide thickness was measured and its correlation with load force, scan speed and applied voltage was analyzed. The surface oxide layer was stripped using a buffered oxide etch. Ohmic contacts were created by applying silver paste on the silicon substrate back face. LAO was performed at approximately 70% humidity. The oxide thickness increased with increasing the load force, the voltage, and reducing the scan speed. We confirmed that LAO/AFM can be used to create both lateral and, to some extent, vertical shapes and patterns, as previously shown in the literature.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.20 no.5
• /
• pp.647-653
• /
• 2017

In this paper, we deal with the experimental verification of 1D virtual force field algorithm based reflexive local path planning on uneven and dusty environment. The existing obstacle detection method on uneven and dusty environment and 1D virtual force field based reflexive local path planning algorithm simply are introduced. Although the 1D virtual force field algorithm is verified by various simulations, additional efforts are needed to verify this algorithm in the real-world. The introduced methods are combined with each other, installed to real mobile platforms and verified by various real experiments.

• Ceramist
• /
• v.10 no.5
• /
• pp.93-101
• /
• 2007

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.22 no.3
• /
• pp.208-213
• /
• 2012

With great advancement of the automobile functions, environmental factors become important performances, especially noise. This paper investigates noise sources of outer rotor type BLDC motor using in the air-conditioner of the automobiles. To this end, this paper is analyzed two viewpoints, structural and electromagnetic causes. Structural analysis is conducted through modal test and analysis. For modal analysis, 3D finite element analysis is carried out using commercial program ansys. Electromagnetic causes are analyzed from local force that is computed by Maxwell stress tensor method. Local force excites structure of motor directly. Finally, correlation analysis is performed to determine effect between noise causes.

• Proceedings of the KIEE Conference
• /
• 2003.11b
• /
• pp.11-14
• /
• 2003

In this paper, we use Fuzzy Logic and Potential field method for optimal path planning of an autonomous mobile robot and apply to navigation for real-time mobile robot in 2D dynamic environment. For safe navigation of the robot, we use both Global and Local path planning. Global path planning is computed off-line using sell-decomposition and Dijkstra algorithm and Local path planning is computed on-line with sensor information using potential field method and Fuzzy Logic. We can get gravitation between two feature points and repulsive force between obstacle and robot through potential field. It is described as a summation of the result of repulsive force between obstacle and robot which is considered as an input through Fuzzy Logic and gravitation to a feature point. With this force, the robot fan get to desired target point safely and fast avoiding obstacles. We Implemented the proposed algorithm with Pioneer-DXE robot in this paper.

• The Journal of Korea Robotics Society
• /
• v.8 no.3
• /
• pp.206-216
• /
• 2013

We investigate the role of contact location information on the perception of local features during contour following in a virtual environment. An absolute identification experiment is conducted under force-alone and force-plus-contact-location conditions to investigate the effect of the contact location information. The results show that the participants identify the local features significantly better in terms of higher information transfer for the force-plus-contact-location condition, while no significant difference was found for measures of the efficacy of contour following between the two conditions. Further data analyses indicate that the improved identification of local features with contact location information is due to the improved identification of small surface features.

• Smart Structures and Systems
• /
• v.15 no.2
• /
• pp.375-393
• /
• 2015

In this study, local dynamic characteristics of mountable PZT interfaces are numerically analyzed to verify their feasibility on impedance monitoring of the prestress-loss in tendon anchorage subsystems. Firstly, a prestressed tendon-anchorage system with mountable PZT interfaces is described. Two types of mountable interfaces which are different in geometric and boundary conditions are designed for impedance monitoring in the tendon-anchorage subsystems. Secondly, laboratory experiments are performed to evaluate the impedance monitoring via the two mountable PZT interfaces placed on the tendon-anchorage under the variation of prestress forces. Impedance features such as frequency-shifts and root-mean-square-deviations are quantified for the two PZT interfaces. Finally, local dynamic characteristics of the two PZT interfaces are numerically analyzed to verify their performances on impedance monitoring at the tendon-anchorage system. For the two PZT interfaces, the relationships between structural parameters and local vibration responses are examined by modal sensitivity analyses.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.25 no.4
• /
• pp.294-297
• /
• 2012

In this work, local oxidation behavior in phosphorous ion-implanted 4H-SiC has been investigated by using atomic force microscopy (AFM). The AFM-local oxidation (AFM-LO) has been performed on the implanted samples, with and without activation anneal, using an applied bias (~25 V). It has been clearly shown that the post-implantation annealing process at $1,650^{\circ}C$ has a great impact on the local oxidation rate by electrically activating the dopants and by modulating the surface roughness. In addition, the composition of resulting oxides changes depending on the doping level of SiC surfaces.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.13 no.1
• /
• pp.848-857
• /
• 2021

This paper proposes an efficient approach based on a machine learning technique to predict the local stresses on mooring chain links. Three-link and multi-link finite element analyses were conducted for a target chain link of D107 with steel grade R4; 24,000 and 8000 analyses were performed, respectively. Two serial Artificial Neural Network (ANN) models based on a deep multi-layer perceptron technique were developed. The first ANN model corresponds to multi-link analyses, where the input neurons were the tension force and angle and the output neurons were the interlink angles. The second ANN model corresponds to the three-link analyses with the input neurons of the tension force, interlink angle, and the local stress positions, and the output neurons of the local stress. The predicted local stresses for the untrained cases were reliable compared to the numerical simulation results.