• International Journal of Ocean System Engineering
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• v.1 no.3
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• pp.120-135
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• 2011

This paper proposes a model based trajectory tracking control scheme for under-actuated underwater robotic vehicles. The difficulty in stabilizing a non-linear system using smooth static state feedback law means that the design of a feedback controller for an under-actuated system is somewhat challenging. A necessary condition for the asymptotic stability of an under-actuated vehicle about a single equilibrium is that its gravitational field has nonzero elements corresponding to non-actuated dynamics. To overcome this condition, we propose a continuous time-varying control law based on the direct estimation of vehicle dynamic variables such as inertia, damping and Coriolis & centripetal terms. This can work satisfactorily under commonly encountered uncertainties such as an ocean current and parameter variations. The proposed control law cancels the non-linearities in the vehicle dynamics by introducing non-linear elements in the input side. Knowledge of the bounds on uncertain terms is not required and it is conceptually simple and easy to implement. The controller parameter values are designed using the Taguchi robust design approach and the control law is verified analytically to be robust under uncertainties, including external disturbances and current. A comparison of the controller performance with that of a linear proportional-integral-derivative (PID) controller and sliding mode controller are also provided.

• Journal of Power Electronics
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• v.13 no.3
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• pp.447-457
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• 2013

For grid-connected LCL-filtered inverters, resonance yields instability and low bandwidth. As a result, careful designs are required. This paper presents a systematic current control structure, where pole assignment consisting of one or more feedbacks is the inner loop, and the outer loop is the direct grid current control. Several other issues are discussed, such as the inner-loop feedback choices, pole-assignment algorithms, robustness and harmonic rejection. Generally, this kind of strategy has three different types according to the inner-loop feedback choices. Among them, a novel pole-assignment algorithm has been proposed, where the inner control maintains four freely-assigned poles which are just two pairs of conjugated poles located at the fundamental and resonance frequencies separately. It has been found that with the different types, the steady-state and dynamic performances are quite different. Finally, simulations and experiments have been provided to verify the control and design of the proposed methods.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.35C no.5
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• pp.33-40
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• 1998

In this paper, a design of current-mode continuous-time filters for low voltage and low frequency applications using complementary bipolar current mirrors is presented. The proposed current-mode filters consist of simple bipolar current mirrors and capacitors and are quite suitable for monolithic integration. Since the design method of the proposed current-mode filters are based on the integrator type of realization, it can be used for a wide range of applications. Since the input impedance of simple bipolar current mirror is small, in this paper, negative feedback amplifier is used to realize is designed by cascade method. The cutoff frequency of the designed filter can be easily tunable by the DC controlling current from 60kHz to 120kHz. The characteristics of the designed current-mode filters are simulated and examined by SPICE using standard bipolar transistor parameters.

• 제어로봇시스템학회:학술대회논문집
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• 1995.10a
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• pp.223-226
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• 1995

New output voltage control technique based on the simple feedback linearization is proposed. The system states are first divided into fast states and slow states. Then, the control stage is composed of the fast inner current control loop and the slow outer voltage control loop. From the inner loop, the average control is derived by the sliding mode concept and it is inserted into the dynamic equations of the slow states in the outer loop. Applying the feedback linearization technique to the obtained large-signal models of the PWM dc-dc converters, linearized large-signal models are obtained for the slow states. With this technique, the output voltage controller of the PWM dc-dc converters can be designed easily in the global state space and its control performance can also be much improved.

• Journal of the Korean Magnetics Society
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• v.22 no.1
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• pp.23-26
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• 2012

New digital feedback algorithm was developed to measure iron loss of soft magnetic materials under a condition of sinusoidal flux waveform. $V_{in}$(B) curve was used instead of H(B) curve to decide next input waveform in the feedback module so that adjusting phases of current waveform, flux waveform, and input waveform could be removed. The effectiveness of the developed algorithm was verified when iron loss of ferrite cores was measured under frequencies of 1 and 10 kHz.

• Atmosphere
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• v.20 no.2
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• pp.101-109
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• 2010

The service of health information was provided through internal and external weather agency web sites. The purpose of this study was to analyze current status of the weather agency web sites dealing with health information in the internet, and to evaluate their contents and technical aspects. The evaluation tool consisted of five area (appropriateness, accessibility, supportiveness, feedback, and continuance) with nineteen items. For the public confidence, web sites were limited to national meteorological administration and representative weather agencies. The evaluating web sites were fourteen from eight countries. The evaluation scores of fourteen web sites were 37.8 out of 53.0 in total. Each subcategory score were 5-12 out of 12 in appropriate, 4-12 out of 12 in accessibility, 4-10 out of 11 in supportiveness, 2-8 out of 9 in feedback, and 2-8 out of 9 in continuance. The score of feedback was the lowest. Survey results indicated that Korean Meteorological Administration homepage was middle status compared with the others in side of depth of health information and feedback from expert. Climate change affect human health, so it will be possible to prevent some disease at first through climate information. It should be developed to provide high quality health information and system related climate on KMA homepage.

• Journal of Power Electronics
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• v.12 no.6
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• pp.886-894
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• 2012

This paper presents a secondary-side, dual-mode feedback LLC resonant controller IC with dynamic PWM dimming for LED backlight units. In order to reduce the cost, master and slave outputs can be generated simultaneously with a single LLC resonant core based on dual-mode feedback topologies. Pulse Frequency Modulation (PFM) and Pulse Width Modulation (PWM) schemes are used for the master stage and slave stage, respectively. In order to guarantee the correct dual feedback operation, Phased-Locked Loop (PLL)-based automatic duty control circuit is proposed in this paper. The chip is fabricated using $0.35{\mu}m$ Bipolar-CMOS-DMOS (BCD) technology, and the die size is $2.5mm{\times}2.5mm$. The frequency of the gate driver (GDA/GDB) in the clock generator ranges from 50 to 425 kHz. The current consumption of the LLC resonant controller IC is 40 mA for a 100 kHz operation frequency using a 15 V supply. The duty ratio of the slave stage can be controlled from 40% to 60% independent of the frequency of the master stage.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.2
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• pp.41.1-41.1
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• 2018

We constrain cosmological parameters by combining three different power spectra measured from galaxy clustering, galaxy-galaxy lensing, and cosmic shear using the Deep Lens Survey (DLS). Two lens bins (centered at z~0.27 and 0.54) and two source bins (centered at z~0.64, and 1.1) containing more than one million galaxies are selected to measure the power spectra. We re-calibrate the initial photo-z estimation of the lens bins by matching with SHELS and PRIMUS and confirm its fidelity by measuring a cross-correlation between the bins. We also check the reliability of the lensing signals through the null tests, lens-source flipping and cross shear measurement. Residual systematic errors from photometric redshift and shear calibration uncertainties are marginalized over in the nested sampling during our parameter constraint process. For the flat LCDM model, we determine S_8=sigma_8(Omega_m/0.3)^0.5=0.832+-0.028, which is in great agreement with the Planck data. We also verify that the two independent constraints from the cosmic shear and the galaxy clustering+galaxy-galaxy lensing measurements are consistent with each other. To address baryonic feedback effects on small scales, we marginalize over a baryonic feedback parameter, which we are able to constrain with the DLS data alone and more tightly when combined with Planck data. The constrained value hints at the possibility that the AGN feedback in the current OWLS simulations might not be strong enough.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.79.2-79.2
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• 2019

Based on three types of 2-point statistics (galaxy clustering, galaxy-galaxy lensing, and cosmic shear power spectra) from the Deep Lens Survey (DLS), we constrain cosmology and baryonic feedback. The DLS is a deep survey, so-called a precursor to LSST, reaching down to ~27th magnitude in BVRz' over 20 deg2. To measure the three power spectra, we choose two lens galaxy populations centered at z ~0.27 and 0.54 and two source galaxy populations centered at z ~0.64 and 1.1, with more than 1 million galaxies. We perform a number of consistency tests to confirm the reliability of the measurements. We calibrated photo-z estimation of the lens galaxies and validated the result with galaxy cross-correlation measurement. The B-mode signals, indicative of potential systematics, are found to be consistent with zero. The two cosmological results independently obtained from the cosmic shear and the galaxy clustering + galaxy-galaxy lensing measurements agree well with each other. Also, we verify that cosmological results between bright and faint sources are consistent. While there exist some weak lensing surveys showing a tension with Planck, the DLS constraint on S8 agrees nicely with the Planck result. Using the HMcode approach derived from the OWLS simulation, we constrain the strength of baryonic feedback. The DLS results hint at the possibility that the actual AGN feedback may be stronger than the one implemented in the current state-of-the-art simulations.

• Journal of IKEEE
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• v.27 no.4
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• pp.386-390
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• 2023

In this study, we examined the quasi-nonvolatile memory characteristics of silicon nanosheet (SiNS) feedback field-effect transistors (FBFETs) fabricated using a complementary metal-oxide-semiconductor process. The SiNS channel layers fabricated by photoresist overexposure method had a width of approximately 180 nm and a height of 70 nm. The SiNS FBFETs operated in a positive feedback loop mechanism and exhibited an extremely low subthreshold swing of 1.1 mV/dec and a high ON/OFF current ratio of 2.4×10⁷. Moreover, SiNS FBFETs represented long retention time of 50 seconds, indicating the quasi-nonvolatile memory characteristics.