• Journal of the Korean Society for Precision Engineering
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• v.21 no.1
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• pp.116-123
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• 2004

The demand for the stable and comfortable cabin of a high speed passenger ship is increasing. The study on shipboard comfort has been mainly concentrated on the motion control of a whole hull body. In this study, however, a new control system operated by two parallel robots (3RPS, 3SPR) such as the active suspension system of motor vehicle is proposed. The goal of this control is keeping zero velocity of the upper robot (cabin) although the lower robot (ship) is moving by the waves. Jacobian matrix was used to design the controller, From the simulation results, the remarkable reduction of motion of the cabin (upper platform) was observed. The 3SPR parallel robot shows better performance compared to the 3RPS robot.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.166.3-166
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• 2001

This paper presents a modeling and control method of active suspension system with full-car model by using H$\infty$ control theory. The full-car model has seven degree of freedom including heaving, pitching and rolling motions. As the control method, H$\infty$ controller is designed so as to guarantee the robustness of closed loop system under the presence of uncertainties and disturbances. Active system with H$\infty$ controller can reduce the accelerations of the car-body in the heaving, pitching and rolling directions. The effectiveness of the controller is proved through simulation results in both time and frequency domains.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.3
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• pp.306-314
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• 2009

The pelvis platform is the mechanical part which accomplishes the activities of diminishing the disturbances from the lower body and maintaining a balanced posture. When a biped robot walks, a lot of disturbances and irregular vibrations are generated and transmitted to the upper body. As there are some important machines and instruments in the upper body or head such as CPU, controller units, vision system, etc., the upper part should be isolated from disturbances or vibrations to functions properly and finally to improve the biped stability. This platform has 3 rotational degrees of freedom and is able to maintain balanced level by feedback control system. Some sensors are fused for more accurate estimation and the control system which integrates synchronization and active filtering is simulated on the virtual environment.

• Journal of Power System Engineering
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• v.7 no.3
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• pp.48-53
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• 2003

This paper deals with the control of a horizontally placed flexible rotor levitated by electromagnets in a multi-input/multi-output (MIMO) active magnetic bearing(AMB) system. AMB is a kind of novel high performance bearing which can suspend the rotor by magnetic force. Its contact-free manner between the rotor and stator results in it being able to operate under much higher speed than conventional rolling bearings with relatively low power losses, as well as being environmental-friendly technology for AMB system having no wear and no lubrication requirements. In this MIMO AMB system, the rotor is a complex mechanical system, it not only has rigid body characteristics such as translational and slope motion but also bends as a flexible body. Reduced order nominal model is computed by consideration of the first 3 mode shapes of rotor dynamics. Then, the $H_{\infty}$ control strategy is applied to get robust controller. Such robustness of the control system as the ability of disturbance rejection and modeling error is guaranteed by using $H_{\infty}$ control strategy. Simulation results show the validation of the designed control system and the modeling method to the rotor.

• Journal of the Korean Society of Food Culture
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• v.23 no.3
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• pp.403-409
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• 2008

Recently, the desire for low body weight, which is an abnormal weight construct along with obesity, has become an evident and serious problem in teenagers. In Korea, the desire for low weight is not perceived as an important problem, but it is rapidly expanding relative to the physical changes and developmental issues teenagers experience. The social atmosphere presented through mass media is the key influencer for the increasing low weight occurrence in teenagers. Because thoughts about beauty have changed among people, and since there is apparent blind interest in slim body shape and appearance, already low-weight individuals are attempting to lose weight along with obese persons. Thus, we consider it necessary to guide teenagers toward having correct perceptions with regard to weight and their own body shape, and that a healthy and appropriate weight is beautiful. Therefore, for this study, we investigated body perception, abnormal weight, attitude toward weight control, and factors related to eating behavior among teenage girls, who are considered the at risk group for overt body weight control behavior. Based on this, we have attempted to set in motion a systematic and active nutrition education program that will allow us to increase body satisfaction by educating on nutritional issues related to development, and ultimately, implant healthy body shape perceptions.

• Advances in aircraft and spacecraft science
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• v.1 no.1
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• pp.27-41
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• 2014

An active flow control technique based on "smart-tabs" is proposed to delay flow separation on a circular cylinder. The actuators are retractable and orientable multilayer piezoelectric tabs which protrude perpendicularly from the model surface. They are mounted along the spanwise direction with constant spacing. The effectiveness of the control was tested in pre-critical and in post-critical regime by evaluating the effects of several control parameters of the tabs like frequency, amplitude, height, angular position and plate incidence with respect to the local flow. Measurements of the mean static pressure distribution around the cylinder were used to estimate the pressure drag coefficient. The maximum drag reduction achieved in the pre-critical regime was of the order of 30%, whereas in the post-critical regime was about 10%, 3% of which due to active forcing. Furthermore, pressure fluctuation measurements were performed and spectral analysis indicated an almost complete suppression of the vortex shedding in active forcing conditions.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.11
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• pp.1672-1684
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• 2004

In this paper, an active vibration control with the use of an air-cell seat for passenger cars is investigated. The roles of the air-cell inserted between the polyurethane foam of the seat and seat cover are first to extend the seat's capability to adopt various shapes of human body and to improve the ride-comfort against road disturbances. The air-cell seat is modeled as a 1-d.o.f. spring-damper system. Because an exact modeling of the air-cell itself is alomost impossible, its dynamic characteristics are analyzed through experiments. A road-adaptive gain-scheduled sky-hook control for the air-cell seat system is proposed. The skyhook gains are scheduled in such a way that the acceleration level transmitted to human body on various road conditions is minimized. Simulations and experimental results are provided.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.10a
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• pp.938-944
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• 1994

Active damping has been shown to offer increased suspension performance in terms of vehicle isolation, suspension packaging, and road-tire contract force. Many semi-active damping strategies have been introduced to approximate the response of active damping with the modulation of passive damping parameters. This study investigates the characteristics of semi-active suspension control through the simulation of passive, skyhook active, and semi-active damping models. A quarter car model is studied with the conrolled damping replacing both passive and active damping. A new semi-active scheme is suggested to eliminate the abrupt changes in semi-active damping force. It is shown that the new strategy performs almost identically to the so called "force controlled" semi-active law without steep changes in damping force or body acceleration.eleration.

• Journal of Korean Academy of Nursing
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• v.30 no.2
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• pp.391-401
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• 2000

This descriptive study was designed to identify the factors associated with weight control behaviors among 273 high school girls with normal body weight. The objectives of the study were ⅰ) to evaluate subjective obesity and satisfaction with the body shape, ⅱ) to describe the weight control behaviors and the motivation, ⅲ) to reveal the relationships between the weight control behaviors and BMI (Body Mass Index), iv) to investigate the relationships between the weight control behaviors and subjective obesity and satisfaction with the body shape, and v) to investigate the relationships between the weight control behaviors and family support. The results showed that 62.6% of the adolescent girls with normal weight perceived that they were fatty and 9.9% thought they were obese. Seventy-five percent of them were not satisfied with their body shape. Eighty percent of the participants reported the main motivation of weight control was to have an attractive appearance. In this study, self-reported weight control methods included dieting (64.8%, skipping or reducing meals), exercise (36.6%), and special dieting (20.1%) such as eating an increased amount of juice or vegetables. It was shown that the subjects who were not satisfied with their body shape and perceived themselves as fatty or obese were active in exercise, diet, and other special diets. Subjects who were on diets and special diets had a higher level of BMI than who were not on diet and special diet. Subjects who exercise had a lower level of BMI than who did not exercised. Family support was significantly related to exercise behavior. The research suggested that there is a increasing responsibility for school nurse to instruct on the body shape and weight control behaviors through health education and consultation. Also, the results suggested that it is important to develop proper diet and exercise methods for adolescents girls to maintain their weight and health.

• Transactions of the Korean Society of Automotive Engineers
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• v.2 no.2
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• pp.73-82
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• 1994

Low-band type active suspension system is implemented on a passenger car. Level. roll, pitch and bouncing motion of body are controlled by a digital controller. Sky-hook damper is applied to control bouncing motion. This paper describes overall construction of the system, design of hydraulic system, sensor system, controller, and control scheme. Performance of prototype car has been evaluated on a test track and reported in the second paper.