• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.8
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• pp.1974-1984
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• 1994

This paper presents a relative coordinate formulation for constrained mechanical systems. Relative coordinates are defined along degrees of freedom of a joint. Graph theoretic analyses are performed to identify topological paths in mechanical systems. Cut constraints are generated to handle closed loop systems. Equations of motion are derived in the Cartesian space and transformed to the joint space. Relative generalized coordinates are corrected to satisfy the cut constraints by a parametrizatiom method.

• Journal of the Korean Mathematical Society
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• v.39 no.1
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• pp.149-161
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• 2002

We study the torsions in the integral homology of the double loop space of the compact simple Lie groups by determining the higher Bockstein actions on the homology of those spaces through the Bockstein lemma and computing the Bockstein spectral sequence.

• The KIPS Transactions:PartA
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• v.8A no.2
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• pp.167-178
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• 2001

This paper presents a new methodology for specification and control of the motion of an articulated rigid body for the purposes of animation by coordinate transformations. The approach is to formulate the problem as a coordinate transformation from the joint space of the body to a user-defined animation space which is chosen for convenience in constraining the motion. Constraints are applied to the resulting coordinate transformation equations. It is sufficiently general so that it can be applied to all common types of control problems, including closed loop as well as open loop mechanisms. We also provided a new approach to simulate a closed loop mechanism, which is using animation space transformation technique. The method is formulated in detail and is demonstrated by animating the motion of an inchworm.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.466-469
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• 2001

In this paper, closed loop V/f control of induction motor has been implemented by the estimated speed. Closed loop V/f control improve the performance of induction motor drive system at low speed compared to open loop V/f control. However, closed loop V/f control need speed sensor. By using the estimated speed, closed loop V/f control is possible without speed sensor. Rotor speed is calculated from the difference between synchronous frequency and slip angular frequency. 3-phase voltage reference is obtained from synchronous frequency. And the PWM technique using space vector PWM is applied in this scheme. In the space vector PWM, effective time of 3-phase voltage reference is used to simplify the calculation of effective voltage time. This scheme is simple to implement and one chip microprocessor was used in experimental system.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.3
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• pp.244-249
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• 2008

In this paper, the stable region for missile guidance loop employing an integrated proportional navigation guidance law is derived. The missile guidance loop is formulated as a closed-loop control system consisting of a linear time-invariant feed-forward block and a time-varying feedback gain. By applying the circle criterion to the system, a bound for the time of flight up to which stability can be assured is established as functions of flight time. Less conservative results, as compared to the result by Popov criterion, are obtained.

• 한국지구물리탐사학회:학술대회논문집
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• 2006.06a
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• pp.3-6
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• 2006

There are three types of frequency-domain loop-loop EM induction method, depending on the loop separation and their location relative to the ground surface: horizontal-loop EM (HLEM), fixed small-loop EM, and helicopter-borne EM (HEM) methods. Multidimensional inversion provides tomographic images of the subsurface resistivity structure and thus enhances the interpretational accuracy of loop-loop EM data. HLEM method is shown to be effective for exploring groundwater resources in weathered and fractured crystalline basement terrains in semi-arid regions. Also, HEM method is useful for locating weak zones in landslide areas. The applicability of inversion to small-loop EM data depends solely on the S/N ratio. The quadrature response of small-loop EM data can only give the equivalent conductivity of a homogenous half-space model, and thus the in-phase component is essential in inverting EM data. However, the in-phase response is much lower and decreases more rapidly with decreasing frequency than the quadrature response. Further work is needed to obtain conductivity-depth images from small-loop EM data.

• Bulletin of the Korean Space Science Society
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• 1995.04a
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• pp.21-21
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• 1995

The structures of 17GHz microwave burst for bipolar sunspots have investigated. which included the effects of the projected shapes of radio sources as they traverse across the solar disk using a magnetic loop employing a model of solenoid coils. An ensemble of high-energy electrons confined in the loop be assumed. The projected brightnesls distributions of gyrosynchrotron emission in x- and o-modes are computed and converted into total intensity and circular polarization difference at 17GHz for various heliocentric distances using numerical integration of the transfer equation along the line of sight. The results of computations at 17GHz for optical thin case will be presented. and the effects of the orientation of the loop will be discussed in detail, as well as the effect of size, position, Structure, and polarization of the emission. Also the results of the various physical P8lrameters such as the strength of magnetic field. high and low energy cut-off of accelerated electrons. spectral index and density of electrons will be preslmted. After comparing the results of model calculation with observations. we found that the observations can be well explained in terms of a loop model and its projection effect.effect.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.6
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• pp.492-501
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• 2016

Three-Loop autopilot is generally used for the acceleration control of guided missiles. Because the acceleration command to the three-loop autopilot is given as values at the center of gravity, feedback information of IMU should be obtained at the same position. However, the position of IMU might not be located at the center of gravity due to the sub-system assignment. This paper presents the stability analysis of three-loop autopilot with respect to the arbitrary position of IMU and variation rate of center of gravity. Gain and phase margins are calculated for several trim points for general anti-tank missiles.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.12
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• pp.13-19
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• 2008

In this paper, we propose a new CL-OSTBC (Closed Loop Orthogonal Space-Time Block Code) scheme for four transmit antennas and compare the scheme with existing closed loop schemes on the performance of BER (Bit Error Rate). In the proposed scheme, a transmitter receives channel feedback information and combines modulated symbols by the symbol combiner, and transmits the symbols encoded by the space-time block encoder. As a result, the proposed scheme achieves full-rate and maximal channel gains by more efficient utilization of the channel feedback information. Moreover, the scheme can reduce computation complexity by using a linear detector. Simulation results on the BER performance show that the proposed CL-OSTBC scheme outperforms existing CL-OSTBC schemes.

• Journal of the Korea Society of Computer and Information
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• v.11 no.2 s.40
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• pp.201-211
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• 2006

The standardization of third Generation Partnership Project(3GPP) has been performed in of order to support interactive multimedia services under mobile environments. In this 3GPP, transmit diversity solutions are applied to increase the available diversity effectively using 2 or more antennas. In this paper, we analyzer the performances on STTD(Space Time Transmit Diversity) technique and its modified techniques such as STTD-OTD, CL-STTD, and 4TX-STTD out of open loop transmit diversities that the standardization of 3GPP has released. We also propose the open loop transmitter and receiver diversities to add the receiver diversity. We analyze and discuss the performance of the proposed techniques and using the Matlab simulation under the flat fading channel environment.