• Journal of Electrical Engineering and Technology
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• 제13권2호
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• pp.1030-1041
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• 2018

The aim of this paper is to design a centrifugal deformation error compensation method with guaranteed performance that allows angular velocity measurement of the magnetically suspended sensitive gyroscopes (MSSGs). The angular velocity measurement principle and the structure of the MSSG are described, and the analytical model of errors caused by MSSG rotor centrifugal deformation is established. Then, an on-line rotor centrifugal deformation error compensation method based on measurement of rotor spinning speed in real-time has been designed. The common issues caused by centrifugal deformation of spinning rotors can be effectively resolved by the proposed method. Comparative experimental results before and after compensation demonstrate the validity and superiority of the error compensation method.

• Journal of Magnetics
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• 제21권4호
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• pp.529-536
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• 2016

Magnetically suspended sensitive gyroscopes (MSSGs) provide an interesting alternative for achieving precious attitude angular measurement. To effectively reduce the measurement error caused by dynamic imbalance, this paper proposes a novel compensation method based on analysis and modeling of the error for a MSSG. Firstly, the angular velocity measurement principle of the MSSG is described. Then the analytical model of dynamic imbalance error has been established by solving the complex coefficient differential dynamic equations of the rotor. The generation mechanism and changing regularity of the dynamic imbalance error have been revealed. Next, a compensation method is designed to compensate the dynamic imbalance error and improve the measurement accuracy of the MSSG. The common issues caused by dynamic imbalance can be effectively resolved by the proposed method in gyroscopes with a levitating rotor. Comparative simulation results before and after compensation have verified the effectiveness and superiority of the proposed compensation method.

• 한국정밀공학회지
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• 제10권3호
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• pp.41-46
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• 1993

The transitional characterisics of oscillations and rotational speeds from the starting to the stationary states in damped single degree of freedom systems acted upon the rotor unbalance forces are studied. Angular travel is assumed to vary with time. The theoretical analysis is obtained by using Laplace transform method. Integration involved in the theoretical results is carried out by the numerical analysis program of continuous-time linear systems to arbitrary inputs. It is evident that the transitional charcterixtics of a machine are affected remarkably by damping ratios, stationary angular velocity time and frequency ratios.

• 한국운동역학회지
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• 제17권1호
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• pp.29-39
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• 2007

This study were obtained elapsed time phase-by-phases, displacement, user angle, velocity and angular velocity to analyse kinematically contributing factors at impact of forehand drive motion, on targeting three male players. The results of the study were presented as follows; In the forehand drive swing, the elapsed time by phases was a total of .52 seconds: .30 seconds from backswing to impact and .22 seconds from impact to follow-through, Considering the mean change in locations of COM of each(part$\rightarrow$body segment) at impact, racket head, left shoulder, right wrist and left hip, the left-right directions(X-axis) were showm to be each $.61{\pm}.03$, $1.19{\pm}.08$, $.66{\pm}.03$, $.94{\pm}.06$, and $.45{\pm}.03m$. The displacement differences of COM of each body segment were shown to be -.57, -.05, -.33, and .16m. For the vertical direction(Z-axis), the center of mass was lowest at impact and highest at E3. For the displacement of the right wrist on the left hip, the right wrist moved to .82m to the lower direction without change in the locations of the hip from E1 from E2. When the left hip moved .02m from E2 to E3, the right wrist moved .7m in the upper direction. In respect to the velocity of each body segment, the hip and the shoulder joint accelerated and then the wrist followed. Then the right wrists of all the subjects and their racket heads showed maximum speed, and an effective swing was observed. At the angle of each part, the angle of the right wrist was the smallest at the backswing and the largest at the moment of the impact. Then it increased gradually in the follow-through section. In respect of angular velocity for subject A, the hip moved and the largest change occurred. Immediately before the impact, the subject made a swing using his right wrist, his hip, and the shoulder joint, showing the maximum value, which was judged to be effective.

• 대한기계학회논문집B
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• 제22권2호
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• pp.139-152
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• 1998

In the present study, the flow characteristics of developing laminar oscillatory flows in a square -sectional 180 deg. curved duct are investigated experimentally. The experimental study using air in a square-sectional 180 deg. curved duct is carried out to measure velocity distributions with a data acquisition and LDV (Laser Doppler Velocimetry) processing system. In this system, Rotating Machinery Resolver (RMR) and PHASE program are used to obtain the results of unsteady flows. The major flow characteristics of developing oscillatory flows are found by analyzing velocity curves, mean velocity profiles, time-averaged velocity distribution of secondary flow, wall shear stress distributions, and entrance lengths. In a lower dimensionless angular frequency, the axial velocity distribution of laminar oscillatory flow in a curved duct shows a convex shape in a central part and axial symmetry. The maximum value of wall shear stress in a lower dimensionless angular frequency is located in an outside wall, but according to increasing the dimensionless angular frequency, the maximum of wall shear stress is moved to inner wall. The entrance lengths of laminar oscillatory flows in a square-sectional 180 deg. curved duct is obtained to 90 deg. of bended angle of duct in this experimental conditions.

• 한국운동역학회지
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• 제20권1호
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• pp.49-55
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• 2010

The purpose of the study was to analyze kinetic factors required to the three-point jump shot of the basketball games through 3-D analysis and ground reaction force(GRF) analysis. Six university male players participated in this study. The results of the study were showed that (1) resultant velocity in the center of mass(COM) was $0.84{\pm}0.27\;m/s$ since a player didn't shot a ball in the highest peak and shot ball at the moment of going up forward and vertical movement. Therefore, it is necessary to find a proper timing to shot a ball; (2) the angular velocity was largely increased in upper arm and fore arm out of the upper-limb segments and the hands had the largest angular velocity since the body is in a fixed situation and angular speed is rapidly increased by the wrist' snap with the rapid movement of upper arm and forearm at the time of release a ball; (3) it is judged that a player can shot a ball at the accurate and high release point when the player collects power vertically to the maximum by keeping GRF to the right and the rear in a proper way and by keeping the body's balance so that a large power may not be dispersed.

• Wind and Structures
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• 제14권2호
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• pp.167-186
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• 2011

This paper presents the results of measurements relating to the aerodynamic forces on flat square plates which were allowed to rotate at different speeds about their horizontal axis, by modifying the velocity of the incoming flow. A 1 m square test-sheet and a 0.3 m square test-sheet were fitted with a number of pressure sensors in order to obtain information relating to the instantaneous pressure distribution acting on the test-sheet; a compact gyroscope to record the angular velocity during the rotational motion was also implemented. Previous work on autorotation has illustrated that the angular velocity varies with respect to the torque induced by the wind, the thickness and aspect ratio of the test-sheet, any frictional effects present at the bearings, and the vorticity generated through the interaction between the plate and the wind flow. The current paper sets out a method based on the solution of the equation of motion of a rotating plate which enables the determination of angular velocities on autorotating elements to be predicted. This approach is then used in conjunction with the experimental data in order to evaluate the damping introduced by the frictional effects at the bearings during steady autorotation.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.2526-2531
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• 2005

A practical pinch torque estimator based on the Kalman filter is proposed for low-cost anti-pinch window control systems. To obtain the accurate angular velocity from Hall-effect sensor measurements, the angular velocity calculation algorithm is executed with additional procedures for removing the measurement noises. Apart from the previous works using the angular velocity estimates and torque estimates for detecting the pinched condition, the torque rate is augmented to the system model and the proposed pinch estimator is derived by applying the steady-state Kalman filter recursion to the model. The motivation of this approach comes from the idea that the bias errors in torque estimates due to the motor parameter uncertainties can be almost eliminated by introducing the torque rate state. For detecting the pinched condition, a systematic way to determine the threshold level of the torque rate estimates is also suggested via the deterministic estimation error analysis. Simulation results are given to certify the pinch detection performance of the proposed algorithm and its robustness against the motor parameter uncertainties.

• The Journal of Korean Physical Therapy
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• 제22권4호
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• pp.49-55
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• 2010

Purpose: The purpose of this study was to investigate the effects of isokinetic exercise on muscular performance and thickness of the quadriceps muscle. Methods: Twenty one healthy male students participated in this study. Participants were divided into 2 groups: $60^{\circ}/sec$ of isokinetic exercise (n=7), $180^{\circ}/sec$ (n=7) and $300^{\circ}/sec$ (n=7). Each group did isokinetic exercises 3 times a week for 6 weeks. Each group was measured for peak torque per body weight, average power and total work using a Biodex System 4. Rectus femoris, vastus laterails and vastus medialis were measured for muscle thickness using a SONOACE 6000C. Data were analyzed by repeated measures ANOVA using SPSS 12.0. Results: There was a significant time-related effect in peak torque per body weight, average power and total work. There was a significant time-related effect in the vastus medialis and rectus femoris muscle thickness. However, there was a significant group by time interaction for vastus laterlis muscle thickness. Conclusion: Isokinetic exercise may be an effective method for improving quadriceps muscle performance regardless of angular velocity. However, the thickness of the rectus femoris and vastus medialis muscle may be increased regardless of the angular velocity of the quadriceps muscle the vastus lateralis muscle may only be remarkably improved when doing exercise with low angular velocity.

• 전자공학회논문지
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• 제54권7호
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• pp.127-132
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• 2017

이 논문에서는 모델 기반 설계에 근거한 이륜 도립진자 로봇의 제어이득을 설계하고 NXT 마인드스톰과 RobotC 언어를 이용하여 수업에 활용 가능한 로봇을 제작 및 실험한다. 이륜 도립진자 로봇은 NXT 마인드스톰, 서보 직류전동기, 자이로 센서, 가속도 센서로 구성된다. 직류전동기에 내장된 엔코더를 이용하여 바퀴의 회전각을 검출하며 이동평균을 이용하여 바퀴의 회전각속도를 계산한다. 자이로 센서는 몸체의 피치 각속도를 측정하며 가속도 센서는 몸체의 피치 각도를 측정한다. 자이로와 가속도의 센서 융합을 통해 몸체 각도를 계산한다. 제어기 이득 요소는 휠 각도, 휠 각속도, 몸체 피치 각도, 몸체 피치 각속도에 대한 가중치이다. 이들 제어이득의 변화에 따른 도립진자 로봇의 변화를 실험하며 유용성을 확인한다.