• The Transactions of the Korean Institute of Electrical Engineers D
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• v.50 no.1
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• pp.31-37
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• 2001

A robust adaptive technique for the longitudinal control of a platoon of automated vehicles is presented. A nonlinear model is used to represent the dynamics of each vehicle within the platoon. The external disturbances such as wind gust and a disturbance term due to engine transmission variations and so on are considered. The state observer is used to avoid direct measurement of the relative velocity or acceleration between the controlled and leading vehicles or the controlled vehicles's acceleration. The proposed controller guarantees to recover platoon stability in operation even if a speed dependent spacing policy is adopted, which incorporates a constant time headway in addition to the constant distance. It is shown that the proposed observer is exponentially stable, and the at the robust adaptive controller is stable. The simulation results demonstrate excellent tracking even in the presence of disturbances.

• Journal of the Korean Institute of Navigation
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• v.8 no.1
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• pp.15-42
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• 1984

Many studies have been done in the field of fuzzy logic theory, but it's application to the ship's steering system is few until this date. This paper is to survey the effect of application of fuzzy logic control by new compositional rule of Inference to the ship's steering system. The controller is made up of a set of Linguistic Control Rules which are conditional linguistic statements connecting the inputs and output, and take the inputs derived from deviation angle and it's angular velocity. The Linguistic Control Rules are implemented on the digital computer to verify the performance of the fuzzy logic controller and simulations have been done in six cases of initial condition and disturbance type. Consequently, it was proved that the ship's steering system by introducing the F.L.C. is performed efficiently and less energy loss system compared with the conventional autopilot.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.1041-1043
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• 1993

A robust position control scheme for a Brushless Direct Drive Motor(BLDDM) is presented. To obtain the robustness under the load variation, a Variable Structure Controller(VSC) is used. However, the VSC has a chattering problem and require the full state informations. To overcome this problem, in this paper, the sliding mode observer is used for compensating the load disturbance and estimating the motor velocity. As a result, the VSC for a BLDDM posision control is designed by using only position measurment and the chattering problem is greatly reduced. To show the validaty of the proposed scheme, the simulation study is carried out.

• Proceedings of the KIEE Conference
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• 1998.11a
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• pp.393-396
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• 1998

To examine the influence of unsteady wake on the flow and heat transfer characteristics, an experiment has been conducted in a four-vane linear cascade. Flow and heat transfer measurements are made for the inlet Reynolds number of 66000(based on chord length and free-stream velocity). Turbulent intensity and stress were measured using hot wire anemometer, and to measure the convective heat transfer coefficients on the blade surfaces liquid crystal/gold film Intrex technique was used. The disturbance by the unsteady wake is characterized by the unresolved unsteadiness. The unsteady wake enhances the turbulent motion of flow in the cascade passage. It also promotes the boundary layer development and transition. The results show that heat transfer coefficients on the suction surface increase with increasing unresolved unsteadiness.

• Journal of the Korean Academy of Clinical Electrophysiology
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• v.3 no.1
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• pp.71-84
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• 2005

This study had performed with purposes to analyze the influence of the change of vestibular sens, visual and proprioceptive sense to the postural sway, so as to supply the necessary clinical materials through developing the physical therapeutic interventions and assessment format for the diabetic neuropathy patients. The sample consisted of fifteen diabetic neuropathy patients with sensory disorder in their lower limbs and fifteen age-matched normal control group. Then the effect of the GVS and the visual cue open and closed to the postural sway were measured by CoP. The summary of the comparison results were obtained below. In the comparison of diabetes neuropathy patients group and age matched normal control group, however diabetes neuropathy patients group had a decrease in superficial tactile sense(p<.001) and nerve conduction velocity(p<.001), they were able to control the posture and walk. So it is, diabetes neuropaty patients had more disturbance compared with AMC group on at a hard surface, particularly in the visual cue open(p<.001) and visual cue closed(p<.01). Moreover, since diabetes neuropathy patients group had more differences in visual cue open and closed(p<. 01), GVS(p<.01), it meant that they're affected largely by vestibular sense, visual sense. In addition, since there're the largest change in doubled sense disturbance such as visual cue open and closed under GVS, it meant that compensation of other senses were quite important for the diabetes neuropathy patients' postural control. In the conclusion, diabetes neuropathy patients who decrease or lose the somatosensory system, sensory training of visual and vestibular system are likely to be quite essential to control the posture and balance.

• Journal of Mechanical Science and Technology
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• v.16 no.10
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• pp.1187-1200
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• 2002

This paper is concerned with the design or an LMI (Linear Matrix Inequality) -based H$\infty$ controller for a line of sight (LOS) stabilization system and with its robustness performance. The linearization of the system is necessary to analyze various nonlinear characteristics, but the linearization entails modeling uncertainties which reduce its performance. In addition, the stability of the LOS can be adversely affected by angular velocity disturbances while the vehicle is moving. As the vehicle accelerates, all the factors that are Ignored and simplified for the linearization tend to Inhibit the performance of the system. The robustness in the face of these uncertainties needs to be assured. This paper employs H$\infty$ control theory to address these problems and the LMI method to provide a suitable controller with minimal constraints for the system. Even though the system matrix does not have a full rank, the proposed method makes it possible to design a H$\infty$ controller and to deal with R and S matrices for reducing the system order. It can be also shown that the proposed robust controller has a better disturbance attenuation and tracking performance. The LMI method is also used to enhance the applicability of the proposed reduced-order H$\infty$ controller for the system given. The LMI-based H$\infty$ controller has superior disturbance attenuation and reference input tracking performance, compared with that of the conventional controller under real disturbances.

• Journal of the Korean Society of Clothing and Textiles
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• v.9 no.3
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• pp.45-51
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• 1985

The purpose of this study is to research into the thermal condition and the weight of clothes suitable for the officers engagged in light works in an air-conditioned room in summer. The Major findings are as follows: 1. Thermal conditions of the working environment are $24.5^{\circ}C$ (Dry bulb temp.), $68\%$ (Relative humidity) and 2.6m/sec (Air Velocity). 2. Total clothing weights are 416.6 g/$m^2$ (male) and 340.9 g/$m^2$ (female). Underwear weights are 96.8g/$m^2$ (male) and 85.1g/$m^2$ (female). The latter turned out to be statistically significant in Sexual difference. 3. Means of the thermal sensation are 3.0 (comfortable; male) 2.7 ('Slightly cool' -'Comfortable'; female) and the relationship between clothing weights and thermal sensation proves to be significantly correlated in the case of female. 4. $66.7\%$ of the women and $37.1\%$ of the men feel sensation of coldness at the body's specific area and $79.5\%$ of the women and $54.3\%$ of the men reveals air-conditioning disturbance. 5. As the thermal sensation is close to 'cool-cold', sensation of coldness or air conditioning disturbance are showed up more frequently which is reversely related with weight of under-wear. It is also proved that air conditioning disturbances are influenced by sexual difference in addition to sensation of coldness and thermal sensation. 6. According to the result of experiment, we can have the idea that at condition $X_1$, the drop of limbs' skin temp. is remarkable. At condition $X_2$ skin temp. for distal limbs and mean skin temp. are raised and the falling degree is similar. At condition $X_3$, mean skin temp. and distal skin temp. are remarkably raised, and the falling degree decreases and the beats of pulse rate increase and diastoric blood pressure is lowered.

• Geophysics and Geophysical Exploration
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• v.7 no.1
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• pp.62-69
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• 2004

The objective of this study is to estimate the distribution of a zone disturbed by excavation (EDZ) around tunnels that have been excavated at about 500 m depth in pre-Tertiary hard sedimentary rock. One of the most important tasks is to evaluate changes in the dynamic stability and permeability of the rock around the tunnels, by investigating the properties of the rock after the excavation. We performed resistivity and acoustic tomography using two boreholes, 5 m in length, drilled horizontally from the wall of a tunnel in pre-Tertiary hard conglomerate. By these methods, we detected a low-resistivity and low-velocity zone 1 m in thickness around the wall of the tunnel. The resulting profiles were verified by permeability and evaporation tests performed at the same boreholes. This anomalous zone matched a high-permeability zone caused by open fractures. Next, we performed resistivity monitoring along annular survey lines in a tunnel excavated in pre-Tertiary hard shale by a tunnel-boring machine (TBM). We detected anomalous zones in 2D resistivity profiles surrounding the tunnel. A low-resistivity zone 1 m in thickness was detected around the tunnel when one year had passed after the excavation. However, two years later, the resistivity around the tunnel had increased in a portion, about 30 cm in thickness, of this zone. To investigate this change, we studied the relationship between groundwater flow from the surroundings and evaporation from the wall around the tunnel. These features were verified by the relationship between the resistivity and porosity of rocks obtained by laboratory tests on core samples. Furthermore, the profiles matched well with highly permeable zones detected by permeability and evaporation tests at a horizontal borehole drilled near the survey line. We conclude that the anomalous zones in these profiles indicate the EDZ around the tunnel.

• Journal of Astronomy and Space Sciences
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• v.26 no.1
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• pp.31-46
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• 2009

An Unscented Kalman Filter (UKF) for estimation of the attitude and rate of a spacecraft using only magnetometer vector measurement is developed. The attitude dynamics used in the estimation is the nonlinear Euler's rotational equation which is augmented with the quaternion kinematics to construct a process model. The filter is designed for small satellite in low Earth orbit, so the disturbance torques include gravity-gradient torque, magnetic disturbance torque, and aerodynamic drag torque. The magnetometer measurements are simulated based on time-varying position of the spacecraft. The filter has been tested not only in the standby mode but also in the detumbling mode. Two types of actuators have been modeled and applied in the simulation. The PD controller is used for the two types of actuators (reaction wheels and thrusters) to detumble the spacecraft. The estimation error converged to within 5 deg for attitude and 0.1 deg/s for rate respectively when the two types of actuators were used. A joint state parameter estimation has been tested and the effect of the process noise covariance on the parameter estimation has been indicated. Also, Monte-Carlo simulations have been performed to test the capability of the filter to converge with the initial conditions sampled from a uniform distribution. Finally, the UKF performance has been compared to that of the EKF and it demonstrates that UKF slightly outperforms EKF. The developed algorithm can be applied to any type of small satellites that are actuated by magnetic torquers, reaction wheels or thrusters with a capability of magnetometer vector measurements for attitude and rate estimation.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.11
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• pp.1055-1065
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• 2009

In this study, stability analysis of boundary layers on airfoils is performed by using parabolized stability equations(PSE). Boundary layer edge conditions are obtained by compressible inviscid flow calculations. Mean velocity and temperature profiles of the laminar boundary layer are obtained by solving compressible boundary layer equations in generalized curvilinear coordinates with fourth order accuracy in the wall normal direction. Laminar mean flow profiles are used as input data for PSE to investigate growth rates of disturbances and stability characteristics. For the cases of boundary layer on NACA0012 and HSNLF(1)-0213 airfoils at Mach number 0.5, growth rates with respect to disturbance frequencies and profiles of disturbance amplitude are investigated. The effect of angle of attack on stability characteristics are examined at both upper and lower surfaces. The neutral stability curves, effect of Mach number and effect of airfoil section shapes are also analyzed.