• Journal of Institute of Control, Robotics and Systems
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• v.22 no.9
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• pp.759-765
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• 2016

This paper presents the principle, dynamics modeling and control, hardware implementation, and flight test result of a hybrid-type unmanned aerial vehicle (UAV). The proposed UAV was designed to provide both hovering and fixed-wing type aerodynamic flight modes. The UAV's flight mode transition was achieved through the attitude transformation in pitch axis, which avoids a complex rotor tilt mechanism from a structural and control viewpoint. To achieve this, a different navigation coordinate was introduced that avoids the gimbal lock in pitch singularity point. Attitude and guidance control algorithms were developed for the flight control system. For flight test purposes, a quadrotor attached with a tailless fixed-wing structure was manufactured. An onboard flight control computer was designed to realize the navigation and control algorithms and the UAV's performance was verified through the outdoor flight tests.

• Structural Engineering and Mechanics
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• v.67 no.5
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• pp.439-455
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• 2018

Within a probabilistic framework, this paper addresses the determination of the static structural response of beams and frames with partially restrained (semi-rigid) connections. The flexibility of the nodal connections is incorporated via an idealized linear-elastic behavior of the beam constraints through the use of rotational springs, which are here considered uncertain for taking into account the largely scattered results observed in experimental findings. The analysis is conducted via the Probabilistic Transformation Method, by modelling the spring stiffness terms (or equivalently, the fixity factors of the beam) as uniformly distributed random variables. The limit values of the Eurocode 3 fixity factors for steel semi-rigid connections are assumed. The exact probability density function of a few indicators of the structural response is derived and discussed in order to identify to what extent the uncertainty of the beam constraints affects the resulting beam response. Some design considerations arise which point out the paramount importance of probability-based approaches whenever a comprehensive experimental background regarding the stiffness of the beam connection is lacking, for example in steel frames with semi-rigid connections or in precast reinforced concrete framed structures. Indeed, it is demonstrated that resorting to deterministic approaches may lead to misleading (and in some cases non-conservative) outcomes from a design viewpoint.

• Journal of Electrical Engineering and Technology
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• v.8 no.4
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• pp.719-728
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• 2013

Probabilistic assessment of voltage stability margin (VSM) with existence of correlated wind speeds is investigated. Nataf transformation is adopted to establish wind speed correlation (WSC) model. Based on the saddle-node bifurcation transversality condition equations and Monte Carlo simulation technique, probability distribution of VSM is determined. With correlation coefficients range low to high value, the effect of WSC on VSM is studied. In addition, two risk indexes are proposed and the possible threat caused by WSC is evaluated from the viewpoint of risk analysis. Experimental results show that the presence of correlated wind speeds is harmful to safe and stable operation of a power system as far as voltage stability is concerned. The achievement of this paper gives a detailed elaboration about the influence of WSC on voltage stability and provides a potentially effective analytical tool for modern power system with large-scale wind power sources integration.

• Journal of the Korea Fashion and Costume Design Association
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• v.9 no.2
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• pp.167-178
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• 2007

The purpose of this study is to systematically examine fusion phenomenon in the cultural aspect aiming to grasp the characteristics of fusion phenomenon, which has a steady impact on fashion trend. A reason for fusion to be noted as a cultural code is because diversely cultural interpretations are impossible from one viewpoint. Therefore, it is aimed to inquire into the characteristics of fusion culture, which is one phenomenon of newly mass culture, and to examine which cultural fusion phenomenon in modern fashion is being displayed in fashion design. First, the culturally fusion phenomenon, which was indicated in modern fashion, is displayed as repetition. The fusion, which integrates into fashion as a cultural code, is a trend of pursuing the experience with different culture. The needs of consumers are shown as fusion fashion that repeatedly uses the traditional detail and the modern detail through cultural repetition. Second, it is displayed as transformation. A concept of fusion is not the simple aggregate in [1+1=2], but the creation of new culture called [1+1=1]. In modern fashion, the cultures in the East and the West are harmoniously transformed, and through transformation, each culture is being compressively delivered. Third, it is displayed as interdependency. The fusion fashion which was newly re-interpreted while having reciprocal influence upon mutual culture, is re-interpreted by forming the equal relationship in heterogeneous elements without destroying fashion that was made previously.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.11
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• pp.1040-1047
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• 2007

This paper presents ripple-free method that can occur in multirate controller design. The conventional multirate input controller has the problem that the ripple occurs in track-following because of chattering phenomenon in control input signal. In order to resolve the problem of rippling, it was proposed to eliminate the ripple phenomenon using feedforward compensator. This paper makes explains problems in conventional ripple-tree multirate controller and introduces a multirate controller design method applying lifting technique based on current estimators in condition space. Using the ripple-tree multirate controller, we show that chattering does not occur in the control input signal through applying the final value theorem from the viewpoint of discrete-time transformation. Also, this study proves that the ripple of the proposed controller decreases with the increase of this sampling frequency and, when sampling frequency is fixed, it decreases with the increase of the control input period.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.126-131
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• 2001

This paper deals with implementation of inverter systems for DC power regeneration, which can regenerate the excessive DC power from DC bus line to AC supply in substations for traction systems. From the viewpoint of both power capacity and switching losses, a three-phase square-wave inverter system is adopted. To control the regenerated power, the magnitude and phase of fundamental output voltages should be appropriately controlled in spite of the variation of input DC voltage. Inverters are operated with modified a-conduction mode to fix the potential of each arm. The overall system consists of the line-to-line voltage and line current sensors, an actual power calculator using d-q transformation method, a complex power controller with PI control scheme, a gating signal generator for modified $\alpha-conduction\;mode\;with\;\delta\;and\;\alpha$, a DPLL for frequency followup, and power circuit.

• Journal of the Korean Regional Science Association
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• v.10 no.2
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• pp.45-51
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• 1994

The purpose of this paper is to present the optimal investment conditions of SOC facilities for maximizing regional social welfare in implementing the urban development project in the theoretical fashion. Particularily, SOC facilities are divided into both supply-side($P_s$) and demand-side SOC ($P_d$) in the paper. General equilibrium analysis from the intra-regional viewpoint by utilizing Pareto's Optimal Conditions and by revising Samuleson's Conditions for public goods($P_s$ and $P_d$) results in the optimum pattern of SOC investment. The following are important implications from the analysis. First, rather than the pursue social equity, SOC investment is to resolve the issue of efficiency to activate the regional economy. Second, the marginal rate of transformation (MRT) between $P_s$ and $P_d$ in the region is to play a significant role in structuring SOC investment plant of local government for social welfare maximization. Third, the optimal SOC investment policy based on this regional economy but also to generate the enhancement of soical amenities of the residents.

• Wind and Structures
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• v.6 no.5
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• pp.357-386
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• 2003

A number of methods based on various ideas have been proposed for simulating the non-Gaussian stationary process. However, these methods have some limitations. This paper reviewed several simulation methods based on the translation method using logarithmic and polynomial functions, which have emerged in the history of statistics and in the field of civil engineering. The applicability of each method is discussed from the viewpoint of the reproducibility of higher order statistics of the object function in the simulated sample functions, and examined using pressure signals measured from wind tunnel experiments for various shapes of buildings. The parameter estimation methods, i.e. the method of moments and quantile plot, are also reviewed, and the useful aspects of each method are discussed. Additionally, a simple worksheet for parameter estimation is derived based on the method of moment for practical application, and the accuracy is discussed comparing with a set of previously proposed formulae.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.33B no.7
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• pp.40-50
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• 1996

An unified compliant control algorithm to regulate the force by dual arms is proposed, where tow arms are treated as one arm in a kinematic viewpoint. The force error calculated form the information of two force/torque sensors attached to the end of each arm is transferred to minimum actuator coordinates, and then is distributed to total system actuator coordinates. The position adjustment at the total actuator coordinates is computed based on the effective computed based on the effective compliance matrix with respect to total actuator coordinates, which is obtained by coordinate transformation between the task coordinates and the total actuator coordinates. An experiment is carried out for dual arms with asymmetric kinematic structure to control an interaction force between manipulators and the environment. The performances of the proposed control algorithm are experimentally compared to those of dual arms employing master/slave scheme. The proposed compliant control algorithm not only ouperforms other algorithms, but also can be treated as an unified approach n the sense that it can be applied to arbitrary dual arm systems with general kinematic structures.

• Korean Journal of Remote Sensing
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• v.21 no.5
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• pp.433-443
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• 2005

This paper show that, without installation of expensive VR (Virtual Reality) program, the sharing information is possible through posting three-dimensional road structures on the web, and avoiding the conventional top-down decision making method, fast bottom-up communication is possible base on the Virtual GIS (Geographic Information System). In this paper, using Viewpoint Scene Builder, internet-based software, the transformation was conducted to give pertinent type for web posting. In order to use the completed route at the scene builder, the output with ASCII Export is required, and ASE (ASCII Scene Export) contains the property information including the coordinate and frame of mesh vertex. Through in advance recognition of the problems regarding route design and petition due to environmental rights infringement, the time and cost due to design alteration can be reduced. It's difficult to provide VR based on the internet because file that embodied with internet GIS was complicated and its capacity comes to scores of mega-bites. But, this study provides VR with internet according to a basis by simplification of files.