• The Transactions of the Korean Institute of Power Electronics
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• v.10 no.4
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• pp.363-372
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• 2005

This paper presents an improved sensorless vector control system for high performance induction motor drives fed by a matrix converter with non-linearity compensation. The nonlinear voltage distortion that is caused by commutation delay and on-state voltage drop in switching devices is corrected by a new matrix converter model. A Reduced Order Extended Luenberger Observer (ROELO) is employed to bring better response in the whole speed operation range and a method to select the observer gain is presented. Experimental results are shown to illustrate the performance of the proposed system.

• Journal of Mechanical Science and Technology
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• v.16 no.12
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• pp.1643-1651
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• 2002

Magnetic levitation systems are required to have a large operating range in many applications. As one method to solve this problem, Time Delay Control (TDC) is applied to a single-axis magnetic levitation system in this paper A reduced-order observer is utilized to estimate states excluding measurable states in the control law. The system consists of a square air-core solenoid and a circular permanent magnet attached on a plastic ball. Theoretical magnetic forces of the system are obtained on the basis of the location of the magnet around the solenoid. The magnetic levitation force is obtained by the experiment, and then compared with the theoretical one. As the results of the control experiments, the nonlinear controller (TDC : 1-2 ㎜) has a larger operating range than the linear controller (PD control : 1-1.4 ㎜), and is superior to linear. control in the robustness to the modeling uncertainty and the performance of the disturbance rejection.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.9
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• pp.21-27
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• 2015

An improved method based on direct extraction and simultaneous optimization is developed to determine model parameters of symmetric inductors fabricated by the high resistivity(HR) silicon-on-insulator(SOI) RF CMOS process. In order to improve modeling accuracy, several model parameters are directly extracted by Y and Z-parameter equations derived from two equivalent circuits of symmetric inductor and grounded center-tap one, and the number of unknown parameters is reduced using parallel resistance and total inductance equations. In order to improve optimization accuracy, two sets of measured S-parameters are simultaneously optimized while same model parameters in two equivalent circuits are set to common variables.

• International Journal of Aerospace System Engineering
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• v.2 no.1
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• pp.43-46
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• 2015

Aeroelastic gust response analysis plays an important role in design of aircrafts. For gust response analysis, frequency domain aerodynamics method has been typically used with generalized aerodynamic influence coefficient matrices at various reduced frequencies. However, it cannot be applied to the aeroservoelastic analysis, such as gust alleviation control. Time-domain state space (SS) models must be built. It attacks little attention that gust response analysis relies on continuous gust time-domain input signal in terms of its PSD function. The aim the current study is to provide a reduced-order modeling (ROM) method based on CFD to model gust responses for continuous gust responses for continuou gust inputs in time domain. The paper analyzed the gust response of AGARD445.6 wing subjected to the Dryden gust with ROMs and compared the difference between the rigid structure and elastic one. The results demonstrate that structure elastic effect effect should be considered in the design of aircraft.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.8 no.4
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• pp.19-28
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• 1999

In order to control thermal deformation of the machine origin of machine tools a empirical model and a compensation system have been developed, Prior to empirical modeling the volumetric error considering shape errors and joint errors of slides is formulated through the homogeneous transformation matrix (HTM) and kinematic chain. Simulation results of the HTM method show that the thermal error of the machine origin is more critical than position-dependent errors. In order to make a stable and effective software error compensation system the GMDH (Group Method of Data Handling) models are constructed to estimate the thermal deformation of the machine origin by measuring deformation data and temperature data. A test bar and gap sensors are used to measure the deformation data. In order to compensate the estimated error the work origin shift method is developed by implementing a digital I/O interface board between a CNC controller and an IBM PC. The method shifts the work origin as much as the amounts which are calculated by the pre-established thermal error model. The experiment results for a vertical machining center show that the thermal deformation of the machine origin is reduced within $\pm$5$mu extrm{m}$.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.6
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• pp.1075-1088
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• 1992

This paper presents techniques used to model a two arm experimental robot. Both arms are compliant and the robot operates in a vertical plane and is therefore influenced by gravity. The robot is being built to study different control strategies for robots containing compliant members. The system is built with extremely flexible members. This limits the required bandwidth of the control electronics, and mimics the flexible motions that are observed for stiffer faster robots. The objective of this paper is to develop a reduced order model of the robot system and to experimentally validate the model. Validation requires that the model includes gravitational effects. Therefore, an assumed modes model is developed which facilitates modeling of gravitational effects. In order to select the order and mode shapes for the model, an analytical solution is derived for a linearized continuous model. This is compared to the assumed modes model to determine the number of mode shapes needed to model the system. The final model, which includes shortening effects, correlates very well with experimental results.

• Journal of Welding and Joining
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• v.29 no.4
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• pp.48-53
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• 2011

A thermal distortion analysis which takes strains directly as boundary conditions removed barrier of analysis time for the evaluation of welding distortion in a large shell structure like ship block. If the FE analysis time is dramatically reduced, the structure modeling time or the input-value calculating time will become a new issue. On the contrary to this, if the calculation time of analysis input-value is dramatically reduced and its results also are more meaningful, a little longer analysis time could be affirmative. In this study, instead of using inherent strain based on elastic analysis, a thermal strain based on elasto-plastic analysis is used as the boundary condition of weldments in order to evaluate the welding distortion. Here, the thermal strain at the weldment was established by using a stress-strain curve established from the test results. It is possible to automatically recognize the modeling induced-stiffness in the shrinkage direction of welded or heated region. The validity of elasto-plastic thermal distortion analysis was verified through the experiment results with various welding sequence.

• The Journal of Information Technology and Database
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• v.6 no.1
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• pp.1-13
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• 1999

The modeling components in the object-oriented paradigm are based on the object, not the structured function or procedure. That is, in the past, when one wanted to solve problems, he would describe the solution procedure. However, the object-oriented paradigm includes the concepts that solve problems through interaction between objects. The object-oriented model is constructed by describing the relationship between object to represent the real world. As in object-oriented model the relationships between objects increase, the control of objects caused by their insertions, deletions, and modifications comes to be very complex and difficult. Because the loss of the referential integrity happens and the object reusability is reduced. For these reasons, the necessity of the control of objects and the visualization of the relationships between them is required. In order that we design a database necessary to implement Object Browser that has functionalities to visualize Java objects and to perform the query processing in Java object modeling, in this paper we show the processes for EER modeling on Java object and its transformation into relational database schema. In addition we implement Java Object Parser that parses Java object and inserts the parsed results into the implemented database.

• Proceedings of the KIEE Conference
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• 1993.07a
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• pp.319-322
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• 1993

This paper presents model reduction method of multivariable systems using orthogonal transformation based on aggregation method in time domain. Reduced model which is desisted by presented method preserve stability as relative dominant eigenvalues are selected in original system and obtained computational advantages using orthogonal functions.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.6
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• pp.23-30
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• 2013

This paper shows the method of winding connection and the balance of three phase of dual inverter systems used for offshore wind power generator. In order to satisfy low cost manufacturing of large scaled wind generator, the number of slot per pole per phase should be reduced. For this reason, in this research, the number is selected as '1' which is the minimum number that stator can have. Based on the prototype machine, three types of machine for the analysis are selected, and various performances especially in terms of electrically balanced condition are also investigated. Moreover, in this paper, new inductance modeling of dual 3-phase considering cross-coupling between two inverter systems is proposed. The several inductances such as mutual-, synchronous inductances are studied. By using FEA, based on calculated the flux linkage of d and q-axis, the validity of the proposed inductance modeling is confirmed.