• 제어로봇시스템학회:학술대회논문집
• /
• 1996.10b
• /
• pp.52-55
• /
• 1996

In order to establish the robust current controller design technique of series wound motor driver system. This paper proposes a method of compensated Bang-Bang current control using a series wound motor driver system under improperly variable load. To get minimum time torque control. A compensated Bang-Bang current controller structure is simpler than the structure of PID plus Bang-Bang controller. This paper shows that a general 8 bits microprocessor be used efficiently implementing such an algorithm. The calculation time of software is extremely small when compared with conventional PID plus Bang-Bang a controller. Both nonlinear operating characteristics of Digital switching elements and Describing Function methods are used for the analysis and synthesis. Real time implementation of compensated Bang-Bang current is achieved. Concept design strategy of the control and PWM waveform generation algorithms are presented in the paper.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.12 no.4
• /
• pp.1-8
• /
• 2003

It is well known that design cost is only about 5% of final product cost but over 70% of it is determined during design stage. Earlier in the product design and development cycle the design changes occur, more economic they become. Therefore, it is recommended that the manufacturing time and cost of product are considered in steps involved in designing and manufacturing a product as early as possible. In this study, it is proposed a possible way that cm be available for estimating manufacturing time of parts, which are manufactured by conventional material removal processes (e.g. turning, milling and drilling). For it to be useful in the early design stage, the minimum number of informations on dimension shape, and design features of part will be used in this method.

• Journal of Astronomy and Space Sciences
• /
• v.36 no.4
• /
• pp.225-234
• /
• 2019

We explore the associations between the total sunspot area, solar north-south asymmetry, and Southern Oscillation Index and the physical characteristics of clouds by calculating normalized cross-correlations, motivated by the idea that the galactic cosmic ray influx modulated by solar activity may cause changes in cloud coverage, and in turn the Earth's climate. Unlike previous studies based on the relative difference, we have employed cloud data as a whole time-series without detrending. We found that the coverage of high-level and low-level cloud is at a maximum when the solar north-south asymmetry is close to the minimum, and one or two years after the solar north-south asymmetry is at a maximum, respectively. The global surface air temperature is at a maximum five years after the solar north-south asymmetry is at a maximum, and the optical depth is at a minimum when the solar north-south asymmetry is at a maximum. We also found that during the descending period of solar activity, the coverage of low-level cloud is at a maximum, and global surface air temperature and cloud optical depth are at a minimum, and that the total column water vapor is at a maximum one or two years after the solar maximum.

• Journal of Institute of Control, Robotics and Systems
• /
• v.18 no.4
• /
• pp.365-370
• /
• 2012

Most path planning algorithms for a marine robot in the ocean environment have been developed without considering the robot's heading angle. As a result, the robot has a difficulty in following the path correctly. In this paper, we propose a limit-cycle circle set that applies to the $Theta^*$ algorithm. The minimum turning radius of a marine robot is calculated using a limit-cycle circle set, and circles of this radius is used to generate a configuration space of an occupancy grid map. After applying $Theta^*$ to this configuration space, the limit-cycle circle set is also applied to the start and end nodes to find the appropriate path with specified heading angles. The benefit of this algorithm is its fast computation time compared to other 3-D ($x,y,{\theta}$) path planning algorithms, along with the fact that it can be applied to the 3-D kinematic state of the robot. We simulate the proposed algorithm and compare it with 3-D $A^*$ and 3-D $A^*$ with post smoothing algorithms.

• Tribology and Lubricants
• /
• v.35 no.4
• /
• pp.244-266
• /
• 2019

The purpose of this study is to estimate the wear volumes of engine journal bearings operating at variable angular velocity of a shaft in the beginning of firing start-up cycle. To do this, first we find the potential region of wear scar on engine journal bearings where the applied bearing load and crank shaft velocity are variable. The potential wear regions are discovered by finding minimum oil film thickness at every crank angle existing below most oil film thickness scaring wear (MOFTSW) obtained based on the concept of the centerline average surface roughness. Then we calculate the wear volume from the wear depth and two wear angles decided by the magnitude of each film thickness lower than MOFTSW at every crank angle. The results show that the expected wear region is located at a few bearing angles after and/or behind the upper center of a big-end bearing and the lower center of a main bearing. And the real wear region is similar to the estimated wear region. Further we find that the wear scar on an engine journal bearing may occur at re-starting time after switch-off of a start motor especially under the condition of high oil temperature.

• Journal of the Korea Society of Computer and Information
• /
• v.19 no.5
• /
• pp.89-98
• /
• 2014

This paper suggests heuristic algorithm for single-model simple assembly line balancing problem that is a kind of NP-hard problem. This problem primarily can be solved metaheuristic method. This heuristic algorithm set the main-path that has a most number of operations from start to end-product. Then the clustering algorithm can be assigns operations to each workstation within cycle time follow main-path. This algorithm decides minimum number of workstations and can be reduces the cycle time. This algorithm can be better performance then metaheuristic methods.

• Earthquakes and Structures
• /
• v.7 no.3
• /
• pp.271-294
• /
• 2014

In recent years, along with the advances made in performance-based design optimization, the need for fast calculation of response parameters in dynamic analysis procedures has become an important issue. The main problem in this field is the extremely high computational demand of time-history analyses which may convert the solution algorithm to illogical ones. Two simplifying strategies have shown to be very effective in tackling this problem; first, simplified nonlinear modeling investigating minimum level of structural modeling sophistication, second, wavelet analysis of earthquake records decreasing the number of acceleration points involved in time-history loading. In this paper, we try to develop an efficient framework, using both strategies, to solve the performance-based multi-objective optimal design problem considering the initial cost and the seismic damage cost of steel moment-frame structures. The non-dominated sorting genetic algorithm (NSGA-II) is employed as the optimization algorithm to search the Pareto optimal solutions. The constraints of the optimization problem are considered in accordance with Federal Emergency Management Agency (FEMA) recommended design specifications. The results from numerical application of the proposed framework demonstrate the capabilities of the framework in solving the present multi-objective optimization problem.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.13 no.2
• /
• pp.103-114
• /
• 2013

This paper suggests a method to reduce the number of performances of Kruskal and Reverse-delete algorithms. Present Kruskal and Reverse-delete algorithms verify whether the cycle occurs within the edges of the graph. For this reason, they have problems of unnecessarily performing extra algorithms from the edges, even though they've already obtained the minimum spanning tree. This paper, first of all, suggests the 1st method which reduces the no. of performances by introducing stop point criteria of algorithm, but at the same time, performs algorithms from all the edges, just like how Kruskal and Reverse-delete algorithms. Next, it suggests the 2nd method which finds the minimum spanning tree from the remaining edges after getting rid of all the unnecessary edges which are considered not to affect the minimum spanning tree. These suggested methods have an effect of terminating algorithm at least 1.4 times and at most 3.86times than Kruskal and Reverse-delete algorithms, when applied to the real graphs. We have found that the 2nd method of the Reverse-delete algorithm has the fastest speed in terminating an algorithm, among 4 algorithms which are results of the 2 suggested methods being applied to 2 algorithms.

• Journal of Astronomy and Space Sciences
• /
• v.40 no.2
• /
• pp.45-57
• /
• 2023

This study examined the effect of solar flux (F10.7) and sunspots number (R) on the daily variation of equatorial electrojet (EEJ) and morning/afternoon counter electrojet (MCEJ/ACEJ) in the ionospheric E region across the eight longitudinal sectors during quiet days from January 2008 to December 2013. In particular, we focus on both minimum and maximum solar cycle of 24. For this purpose, we have collected a 6-year ground-based magnetic data from multiple stations to investigate EEJ/CEJ climatology in the Peruvian, Brazilian, West & East African, Indian, Southeast Asian, Philippine, and Pacific sectors with the corresponding F10.7 and R data from satellites simultaneously. Our results reveal that the variations of monthly mean EEJ intensities were consistent with the variations of solar flux and sunspot number patterns of a cycle, further indicating that there is a significant seasonal and longitudinal dependence. During the high solar cycle period, F10.7 and R have shown a strong peak around equinoctial months, consequently, the strong daytime EEJs occurred in the Peruvian and Southeast Asian sectors followed by the Philippine regions throughout the years investigated. In those sectors, the correlation between the day Maxima EEJ and F10.7 strengths have a positive value during periods of high solar activity, and they have relatively higher values than the other sectors. A predominance of MCEJ occurrences is observed in the Brazilian (TTB), East African (AAE), and Peruvian (HUA) sectors. We have also observed the CEJ dependence on solar flux with an anti-correlation between ACEJ events and F10.7 are observed especially during a high solar cycle period.

• Journal of Environmental Science International
• /
• v.13 no.3
• /
• pp.245-250
• /
• 2004

The SBR(Sequencing Batch Reactor) process is ideally suited to treat high loading wastewater due to its high dilution rate. SBR operates by a cycle of periods consisting of filling, reacting, settling, decanting and idling. The react phases such as aeration or non-aeration, organic oxidation, nitrification, denitrification and other bio-logical reactions can be achieved in a reactor. Although the whole reactions can be achieved in a SBR with time distributing, it is hard to manage the SBR as a normal condition without recognizing a present state. The present state can be observed with nutrient sensors such as ${NH_{4}}^{+}-N$, ${NO_{2}}^{-}-N$, ${NO_{3}}^{-}-N} and ${PO_{4}}^{ 3-}-P.$ However, there is still a disadvantage to use the nutrient sensors because of their high expense and inconvenience to manage. Therefore, it is very useful to use common on-line sensors such as DO, ORP and pH, which are less expensive and more convient. Moreover, the present states and unexpected changes of SBR might be predicted by using of them. This study was conducted to get basic materials for making an inference of SBR process from ORP(oxidation reduction potential) of synthetic wastewater. The profiles of ORP, DO, and pH were under normal nitrification and denitrification were obtained to compare abnormal condition. And also, nitrite and nitrate accumulation were investigated during reaction of SBR. The bending point on ORP profile was not entirely in the low COD/NOx ratio condition. In this case, NOx was not entirely removed, and minimum ORP value was presented over -300mV. Under suitable COD/NOx ratio which complete denitrification was achieved, ORP bending point was observed and minimum ORP value was under -300m V. Under high COD/NOx ratio, ORP bending point was not detected at the first subcycle because of the fast denitrification and minimum ORP value was under -300mV at the time.