• Geophysics and Geophysical Exploration
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• v.6 no.4
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• pp.187-194
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• 2003

A small-loop electromagnetic (EM) system using multiple frequencies has advantages in survey speed and cost despite of limitation on its depth of investigation. Therefore, small-loop EM surveys have been frequently used on various site investigations involving engineering and environmental problems. We have developed a subsurface imaging technique using small loop EM data. We used a one-dimensional (ID) inversion method to reconstruct a subsurface image from frequency EM sounding data. Tests using simulated data show that the method can reasonably recover the subsurface resistivity structure. Also, the method was tested on field data obtained with multiple frequency small loop EM system at a farm in Chunchon, Korea. The resistivity image obtained form field data compares favorably with the image from the dipole-dipole resistivity survey.

• Journal of Electrical Engineering and Technology
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• v.6 no.2
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• pp.226-232
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• 2011

The $H_{\infty}$ approach, adopted in this paper, is based on loop shaping using a normalized coprime factor combined with a field-oriented control to control induction motor. We develop two loops. The first one, the inner loop, controls the stator current by $H{\infty}$ controller in order to obtain good performance. The second loop, the outer one, guarantees stability and tracking performance of speed and rotor flux using a proportional integral controller. When the rotor flux cannot be measured, we introduce a flux observer to estimate the rotor flux. Simulation and experimental results are presented to validate the effectiveness and the good performance of this control technique.

• Journal of the Korea Computer Industry Society
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• v.4 no.4
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• pp.501-508
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• 2003

In this paper A new theory of linear loop transformation called Elimination of Data Dependency(BDD) is presented. The current framework of linear loop transformation cannot identify a significant fraction of parallelism. For this reason, a method to extract the maximum loop parallelism in perfect nested loops is presented. This technique is applicable to general loop nests where the dependence include both distance and directions.

• International Journal of Control, Automation, and Systems
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• v.5 no.1
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• pp.35-42
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• 2007

This paper presents an INS(Inertial Navigation System) grade, surface micro-machined differential resonant accelerometer(DRXL) manufactured by an epitaxially grown thick poly silicon process. The proposed DRXL system generates a differential digital output upon an applied acceleration, in which frequency transition is measured due to gap dependent electrical stiffness change. To facilitate the resonance dynamics of the electromechanical system, the micromachined DRXL device is packaged by using the wafer level vacuum sealing process. To test the DRXL performance, a nonlinear self-oscillation loop is designed based on the extended describing function technique. The oscillation loop is implemented using discrete electronic elements including precision charge amplifier and hard feedback nonlinearity. The performance test of the DRXL system shows that the sensitivity of the accelerometer is 24 Hz/g and its long term bias stability is about 2 mg($1{\sigma}$) with dynamic range of ${\sigma}70g$.

• Journal of Positioning, Navigation, and Timing
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• v.7 no.3
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• pp.113-125
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• 2018

Since the global positioning system receivers on the surface of the Earth use satellite signals sent from a remote distance and the intensity of received signals is weak, they are vulnerable to jamming. This paper implements a vector-tracking loop (VTL)-based global navigation satellite system (GNSS) receiver algorithm as an anti-jamming technique and compares the performance of VTL-based receivers with that of scalar-tracking loop (STL) that is used in general GNSS receivers at various jamming environments and a vehicle's dynamics. The simulation results shows that VTL is more robust against jamming than STL in all operating environments.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.646-653
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• 2001

LQG/LTR Control Methology is recently used for the analysis of multi-variable control in frequency domain. Target filter loop is designed by the demanding requirements such as cross-over frequency, disturbance rejection in low frequency domain, zero steady-state error, identification of maximum and minimum singular values and sensor noise rejection in high frequency domain. Loop transfer recovery is accomplished by solving the cheap control and then simulation close to the target filter loop. In this study, LQG/LTR Control Methodology is applied to the seat suspension system. It is found that this technique is very effective to control the system and improve the ride quality of human body.

• 제어로봇시스템학회:학술대회논문집
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• 1990.10b
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• pp.1327-1331
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• 1990

A new dual loop controller using color LCD bar graphs with LED back lights has been developed. An optional memory card is used to load or save the controller configuration, which may be a preprogrammed standard package or a user-programmed configuration, in addition to the built-in functions ready for user selection. The bar-graph display is selectable for single-loop or dual-loop use. A high grade of self-tuning functions using a modeling technique is built-in as standard. The controller can accommodate optional plug-in modules for thermocouples, communication, etc. All the options are fully field upgradable.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.52 no.7
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• pp.379-384
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• 2003

QFT(Quantitative Feedback Theory) is a very practical design technique that emphasizes the use of feedback for achieving the desired system performance tolerances in despite of plant uncertainties and disturbances. The loop shaping procedure of the QFT method is employed to design the robust controller, until the desired bounds are satisfied. This paper presents a method to estimate the Pm parameters using the loop shaping of the QFT. The proposed method identifies the parameter vector of PID controller from a linear system that develops from rearranging the two dimensional input matrices and output vectors obtained from the QFT bounds. The feasibilities of the suggested algorithm are illustrated with an example.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.38 no.2
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• pp.119-126
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• 1989

In this paper, a new technique, which uses an "input compensator", is proposed to design a controller for the rebalance loop of a Dynamically Tuned Gyroscope (DTG) and the performance of this new controller is compared with that of a Proportional and Integral (PI) controller through simulation. The rebalance loop is an essential part of a DTG` it is composed of a controller, low-pass filters, notch filters and torque drivers. Among them, the controller is the main attributor to determine the performance of the rebalance loop. Through simulation, it is concluded that the performance of the newly designed controller is better than that of a PI controller in the point of (1) low maximum overshoot, (2) short settling time and (3) small steady state error.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.45 no.4
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• pp.582-589
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• 1996

In this paper, an adaptive control problem of a hydraulic actuator for vehicle active suspension controller is divided into two parts: the inner loop controller and the outer loop controller. Inner loop controller, which is a nonlinear adaptive controller, is designed to control the force generated by the nonlinear hydraulic actuator acting under the effects of Coulomb friction. For simplicity of designing a nonlinear controller, the spool valve dynamics of a hydraulic actuator is reduced using a singular perturbation technique. The estimation error signal used to an indirect parameter adaptation is calculated without a regressor filtering. The absolute velocity of a sprung mass will be damped down by its negatively proportional term(sky-hook damper) adopted as an outer loop controller. Simulation results are presented to show the importance of controlling the actuator force and the validity of the proposed adaptive controller. (author). refs., figs. tab.