• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제53권3호
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• pp.123-127
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• 2004

Mode conversion type ultrasonic rotary motor using bolt tightened Langevin type vibrator was studied. Driving frequency of the motor, displacements and elliptical trajectories at tip of the coupler were simulated by finite element analysis program (ANSYS). Speed and torque of the fabricated motor were measured as functions of input voltage and load. As results, from FEA the driving frequency of 40.8[kHz] and useful elliptical trajectories were found. Fabricated motor rotated clockwise at frequency of 38.2[kHz]. Speed and torque of the motor were increased when the input voltage was increased. Maximum speed, torque and efficiency were 75[rpm], 0.14[Nm] and 6.28[％], respectively.

• 아동학회지
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• 제30권4호
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• pp.69-85
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• 2009

The purpose of this study was to identify developmental trajectories of externalizing problems in preschoolers and to investigate dimensions of temperament and parental behaviors associated with trajectory groups. Subjects were 180 3- to 5-year-old preschoolers (96 males, 84 females) in the metropolitan area of Seoul. They were assessed three times at 5 month intervals over a one year period. Teachers reported on children's behavior problems, and parents reported on children's temperaments. Latent Growth Curve Modeling Analysis with cohort sequential design revealed externalizing behaviors gradually decreased between 3 and 6. At the 6-year-old level externalizing behaviors were associated with high novelty seeking temperament. The results were discussed in terms of the importance of longitudinal research in developmental psychopathology.

• 가정과삶의질연구
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• 제26권5호
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• pp.51-60
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• 2008

This study examined the influence of attachment to parents, parents' monitoring, and deviant peers on trajectories of internalizing and externalizing problems in adolescence. Participants were 2528(1251 male and 1277 female) adolescent from the 2004(age:16 of latent growth curve modeling indicated that (1) Individual differences of internalizing and externalizing problems' nitial levels and changes were significant. (2) Attachment to parents influenced both initial levels and changes of internalizing problems. (3) Attachment to parents and parents' monitoring influenced initial levels of externalizing problems, and deviant peers influenced both initial levels and changes of externalizing problems.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.120.4-120
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• 2001

In this paper, a method of generating trajectories in real time for a mobile robot in a dynamic environment is proposed. Specifically, this method is focused on soccer-playing robots that need to calculate trajectories in real time, which are constantly subject to rapidly change as targets and obstacles move. The robots also should move at the fastest available speed, while tracking the generated trajectories. The method proposed in this paper solves the geometric problem of finding a smooth curve that joins two endpoints. To have this solved, we assign five constraints to each endpoint, which are the usual x, y, theta, and curvature as well as the influence of the initial robot velocity on the path. With these five constraints, the path generated can always be physically followed by robot. Through this method, the travel time of the robot over the entire path can b optimized. Therefore it can ...

• Advances in aircraft and spacecraft science
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• 제4권4호
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• pp.371-399
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• 2017

The motion of propeller driven airplanes, flying at constant speed on ascending or descending helical trajectories is analyzed. The dynamical abilities of the airplane are shown to result in restrictions on the ranges of the geometrical parameters of the helical path. The physical quantities taken into account are the variation of air density with altitude, the airplane mass change due to fuel consumption, its load factor, its lift coefficient, and the thrust its engine can produce. Formulas are provided for determining all the airplane dynamical parameters on the trajectory. A procedure is proposed for the construction of tables from which the flyability of trajectories at a given angle of inclination and radius can be read, with the corresponding minimum and maximum speeds allowed, the final altitude reached and the amount of fuel burned. Sample calculations are shown for the Cessna 182, a Silver Fox like unmanned aerial vehicle, and the C-130 Hercules.

• 제어로봇시스템학회논문지
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• 제2권3호
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• pp.148-157
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• 1996

Availability of input trajectories corresponding to desired output trajectories is often important in designing control systems for batch and other transient processes. In this paper, we propose a predictive control-type model-based iterative learning algorithm which is applicable to finding the nominal input trajectories of a linear time-invariant batch process. Unlike the other existing learning control algorithms, the proposed algorithm can be applied to nonsquare systems and has an ability to adjust noise sensitivity as well as convergence rate. A simple model identification technique with which performance of the proposed learning algorithm can be significantly enhanced is also proposed. Performance of the proposed learning algorithm is demonstrated through numerical simulations.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1990년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 26-27 Oct. 1990
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• pp.1145-1149
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• 1990

This paper proposes a numerical method for redundant manipulators using predetermined optimal resolution. In order to obtain optimal joint trajectories, it is desirable to formulate redundancy resolution as an optimization problem having an integral cost criterion. We predetermine the trajectories of redundant joints in terms of the Nth partial sum of the Fourier series, which lead to the solution in the desirable homotopy class. Then optimal coefficients of the Fourier series, which yield the optimal solution within the predetermined class, are searched by the Powell's method. The proposed method is applied to a 3-link planar manipulator for cyclic tasks in Cartesian space. As the results, we can obtain the optimal solution in the desirable homotopy class without topological liftings of the solution. To show the validity of the proposed method, we analyze both optimal and extremal solutions by the Fast Fourier Transform (FFT) and discuss joint trajectories on the phase plane.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 심포지엄 논문집 정보 및 제어부문
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• pp.334-336
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• 2007

This paper presents a beat gesture recognition method to synchronize the tempo of a robot playing a piano with the desired tempo of the user. To detect an unstructured beat gesture expressed by any part of a body, we apply an optical flow method, and obtain the trajectories of the center of gravity and normalized central moments of moving objects in images. The period of a beat gesture is estimated from the results of the fast Fourier transform. In addition, we also apply a motion control method by which robotic fingers are trained to follow a set of trajectories, Since the ability to track the trajectories influences the sound a piano generates, we adopt an iterative learning control method to reduce the tracking error.

• Advances in aircraft and spacecraft science
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• 제5권5호
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• pp.551-579
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• 2018

This work is concerned with the motion of propeller driven airplanes, flying at constant velocity on ascending or descending rectilinear trajectories. Its purpose is to provide important features of rectilinear flights that are required for airplane trajectory planning but that cannot be found already published. It presents a method for calculating the amount of fuel used, the restrictions on the trajectory parameters, as inclination and speed, which result from the load factor, the lift coefficient, the positivity and upper boundedness of the power available. It presents a complete discussion of both ascending and descending flights, including gliding. Some original remarks are made about the parameters of gliding. It shows how to construct tables of parameters allowing to identify rapidly flyable trajectories. Sample calculations are shown for the Cessna 182 and a Silver Fox like unmanned aerial vehicle.

• 한국분말재료학회지
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• 제4권1호
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• pp.55-62
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• 1997

Flow and heat transfer characteristics of gas, and trajectories and cooling characteristics of droplets/particles in a gas atomizer were investigated by a numerical simulation using FLUENT code. Among several kinds of solution method, the k-$\varepsilon$ turbulent model, power-law scheme, SIMPLE algorithm is adopted in this study. Momentum and heat exchange between a continuous phase(gas) and a dispersed phase(particle) were taken into account. Particle trajectories are simulated using the Lagrangian method, and Rosin-Rammler formula is used for the particle size distribution. Streamlines, velocities and pressures of gas, and trajectories, velocities and cooling rates of particles have been investigated for the various gas inlet conditions. Small but very intensive recirculation is found just below the melt orifice, and this recirculation seems to cause the liquid metal to spread radially. Particle trajectory depends on the particle size, the location of particle formation and the turbulent motion of gas. Small particle cools down rapidly, while large diameter particles solidify slowly, and this is mainly due to the differences in thermal inertia.