• Journal of Korean Society of Industrial and Systems Engineering
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• v.23 no.60
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• pp.37-46
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• 2000

A biomechanical model of lower extremity in seated postures was developed to assess muscular activities of lower extremity involved in a variety of foot pedal operations. The model incorporated four rigid body segments with the twenty-four muscles to represent lower extremity This study deals with quasi-static movement to investigate dynamic movement effect in seated foot operation. It is found that optimization method which has been used for modeling the articulated body segments does not predict the forces generated from biarticular muscles and antagonistic muscles reasonably. So, the revised nonlinear optimization scheme was employed to consider the synergistic effects of biarticular muscles and the antagonistic muscle effects from the stabilization of the joint. For the model validation, three male subjects performed the experiments in which EMG activities of the nine lower extremity muscles were measured. Predicted muscle forces were compared with the corresponding EMG amplitudes and it showed no statistical difference. For the selection of optimal seated posture, a physiological meaningful criterion was developed for muscular load sharing developed. For exertion levels, the transition point of type F motor unit of each muscle is inferred by analyzing the electromyogram at the seated postures. Also, for predetermined seated foot operations exertion levels, the recruitment pattern is identified in the continuous exertion, by analyzing the electromyogram changes due to the accumulated muscle fatigue.

• Journal of Navigation and Port Research
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• v.31 no.8
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• pp.683-687
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• 2007

Hydroelastic deformation of pontoon type floating structure in waves is critical in structural design. Therefore, it is necessary to develop additional technology that make to dissipate the wave energy as the submerged horizontal plate. In this study, we investigate the characteristics of hydrodynamic interaction effect by the submerged plate affecting to the radiation forces on a pontoon type floating structure using numerical analysis. We have developed the numerical method based on the composite grid system that consists of moving and fixed grid to compute the radiation forces due to the heaving motion of pontoon type floating structure and submerged plate. The numerical simulations based on the finite difference method are carried out to solve the fully nonlinear free surface involving the breaking waves and compared with the experimental data to confirm the reliability of the numerical method. Then, we discuss the interaction effects on the hydrodynamic forces that could influence on the hydroelastic response of floating structure.

• Journal of the Korean Institute of Intelligent Systems
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• v.20 no.1
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• pp.109-115
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• 2010

A main technology of opening and closing a sluice gate is accurate synchronous and position control for the two cylinders when they are moving with the sluice gate together over 10[m]. Since the supply flow and supply pressure of cylinders are not constant and a nonlinear friction force of the piston in cylinders exists, a difference will be made between the displacement of two cylinders. This difference causes the sluice gate to deform and abrade, and even it may be out of order. In order to solve this problem we design two kinds of fuzzy PI controllers. The former is for a position control of two cylinders, the latter is for their synchronous control. We show some simulation results compare the performance of fuzzy PI controller to the conventional PID controller.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.50 no.2
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• pp.147-153
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• 2014

The purpose of this paper is to examine the roll damping characteristics by bilge keels on the fishing vessel. Unlike other degree of freedom motions, roll motion is highly nonlinear. However the quantitative evaluation of roll damping combined with waves is very important for the fishing vessel. To reduce roll motion, roll motion stabilizers such as a bilge keel is used due to easy made and cheap cost rather than anti-rolling tank and fin-stabilizer. Authors paid attention to the shape of bilge keel and waves to grasp the roll damping for the fishing vessel and studied about the difference of tendencies of roll angle following the shapes of bilge keel. The model ship was the offshore large purse seiner and four types of bilge keel were used. The data from the experiments were provided and analyzed to investigate the rolling characteristics of the model ship being affected by the wave height, wave period and bilge keel shape. The results of the study showed that three types of the bilge keel have little effective, but only one has an effect on the roll damping. So bilge keel shape and its attachment method need to be a future study for the practical use in fishing vessel.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.6
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• pp.1152-1162
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• 2011

In this paper, a single-phase DC-AC inverter using two embedded Z-source converters is proposed. The proposed inverter is composed of two embedded Z-source converters with common DC source and output AC load. The output AC voltage of the inverter is obtained by the difference of output capacitor voltages of each converter. The output voltage of each converter take shape of the asymmetrical AC waveform centering zero voltage. Therefore, the proposed inverter can generate the same output voltage despite low VA rating L-C elements, compared to the conventional inverter using high DC voltage with AC ripple. To verify the validity of the proposed system, the PSIM simulation was achieved under the condition of rapid increase of DC source (110[V]${\rightarrow}$150[V]) and R-load (50[${\Omega}$]${\rightarrow}$300[${\Omega}$]). For controlling the voltage of the inverter system, the one-cycle controller was adopted. As results, the proposed inverter output the constant AC voltage (220[V]rms/60[Hz]) for all conditions. Also, the R-L load and nonlinear diode load were adopted for the proposed inverter loads, and we could know that the its output voltage characteristics were as good as the pure R-load. Finally, the RMS and THD of output AC voltage were examined for the different loads, input DC voltages and reference voltage signals.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.1
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• pp.8-14
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• 1999

The active devices used at microwave frequency have the different phase shift according to input power. Especially, The difference of the phase shift is large in the saturation region of the amplifier. In this paper, we disigned the phase control system for fixing the different phase shift at device. With the high frequency nonlinear amplifier, we fabricated such system that the phase shift to be fixed automatically using the varible phase shifter. The variable phase shifter fixed total phase variation of the circuit using the information that was obtained from the comparison of imputsignal phase with output signal phase. Even though the input signal is 2-tone or FM type, we could estimate and also fix the phase variation on DUT Dynamic range is about 10dB. It has been experimented at 1960MHz using Teflon (H=31mil, ${\varepsilon}r$=3.2)

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.5
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• pp.199-208
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• 2017

Lithium polymer batteries are used in energy storage systems (ESS), electric vehicles (EVs), etc. due to their high safety, fast charging and long lifecycle, and now they are used in agricultural drones. However, when overcharging and overdischarging, the lithium-polymer battery is destroyed in the gap structure in the lithium-ion battery and the battery life is reduced. In order to prevent overcharge and overdischarge, uneven cell voltage Cell balancing system is needed. In this paper, a fuzzy controller suitable for nonlinear systems is proposed by detecting the unbalanced cells by detecting the voltage difference between charging and discharging of each cell, and suggesting the applied cell balancing algorithm. In this paper, we have designed the cell balancing of the battery pack of agricultural drones by fuzzy control and it is designed for equal control between cells. As a final result, we checked whether cell balancing is good, and when there are two cells, Cell balancing was confirmed. We tested whether it could be used for other products. As a result, we confirmed that cell balancing is good regardless of the number of cells used.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.8
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• pp.56-64
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• 2005

It is prerequisite that we have to fomulate the nonlinear mathematical modeling to design the guidance and control system of rotorcraft-based unmanned aerial vehicle using a small-scaled commercial helicopter. The small-scaled helicopters are very different from the full-scale helicopters in dynamic behavior such as high rotation speed and high frequency dynamic characteristics. In this paper, the formulation of the mathematical model of the small-scaled helicopter to minimize the complexity is presented by component and source build-up approach. It is linearized at the trim condition of hovering and forward flight and analyzed the flight modes. The results of this approach have general trends but a little difference. To verify this approach, it is necessary to compare this theoretical model with experimental results by system identification using flight test as a next research topic.

• Journal of Biomedical Engineering Research
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• v.24 no.3
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• pp.183-192
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• 2003

A transformation methode of the chromaticity coordinates was proposed to calibrate the measured data obtained by a urine analysis system which implemented in our previous study. Generally. the reacted color of a reagent strip by urine analysis system often exhibit the color distortions due to nonlinear characteristics of the various devices that is the optic module mechanism. hardware, and surround circumstance. A color correction method for minimizing the color distortion play a few role in maintaining high accuracy and reproduction of the urine analysis system. In this work, we used the compensation method such as the shading correction, the characteristic curve extraction of RGB color by means of third order spline interpolation, and linear transformation using a reference color. In addition, 1931 CIE XYZ color space was used to compensate the color of the measured data by a standard reference system as colorimeter. A compensation matrix was obtained so that the output values of the urine analysis system is nearly equal to that of a standard reference system for identical color sample. Color correction obtained by a urine analysis system which implemented in our previous study exhibited a good color accuracy when it was compared with the reference data. Observed result from an experiments on ten items or a urinalysis strip that color difference or between two urine analysis system was 1.28.

• Journal of the Korean Institute of Intelligent Systems
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• v.16 no.2
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• pp.215-221
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• 2006

This paper is concerned with the control of multiple nonlinearities included in a humanoid robot system. A humanoid robot has some problems such as the structural instability, which leads to consider the control of multiple nonlinearities caused by driver parts as well as gear reducer. Saturation and backlash are typical examples of nonlinearities in the system. The conventional algorithms of backlash control were fuzzy algorithm, disturbance observer and neural network, etc. However, it is not easy to control the system by employing only single algorithm since the system usually includes multiple nonlinearities. In this paper, a switching Pill is considered for a control of saturation and a dual feedback algorithm is proposed for a backlash control. To implement the above algorithms, the system identification is firstly performed for the minimization of the difference between the results of simulation and experiment, and then the switching Pill gains are determined using genetic algorithm with some heuristic approach. The performance of the switching Pill controller for saturation and the dual feedback for backlash control is investigated through the simulation. Finally, it is shown that the implemented control system has good results and can be applied to the real humanoid robot system ISHURO.