• 한국생산제조학회지
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• 제22권3호
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• pp.421-428
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• 2013

The current vibration reduction methods for positioning systems lead to either complicated motion or the need for additional hardware when the positioning systems carry out frequent short-distance movements. This paper proposes a simple yet efficient vibration reduction method for positioning systems subjected to frequent short-distance movements. The essence of the proposed method is the trapezoidal or triangular velocity profiles, whose acceleration/deceleration rates are designed to be related to the natural frequency of concern. The combined use of the proposed method and the input shaping method is also proposed for the possible application to multi-mode systems. Experiments are performed to validate the proposed method. The simulation and experiments prove that the proposed method is of great use for residual vibration reduction in positioning systems subjected to frequent short-distance movement.

• 대한의용생체공학회:의공학회지
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• 제31권2호
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• pp.162-169
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• 2010

This paper deals with the recognition algorithm of walking will based on torque estimation. Recently, concern about walking assistant aids is increasing according to the increase in population of elder and handicapped person. However, most of walking aids don't have any actuators for its movement. So, general walking aids have weakness for its movement to upward/download direction of slope. To overcome the weakness of the general walking aids, many researches for active type walking aids are being progressed. Unfortunately it is difficult to control aids during its movement, because it is not easy to recognize user's walking will. Many kinds of methods are proposed to recognize of user's walking will. In this paper, we propose walking will recognition algorithm by using torque estimation from wheels. First, we measure wheel velocity and voltage at the walking aids. From these data, external forces are extracted. And then walking will that is included by walking velocity and direction is estimated. Here, all the processes are verified by simulation and experiment in the real world.

• Advances in nano research
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• 제14권4호
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• pp.329-334
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• 2023

Organic ferroelectric material found vast application in a verity of engineering and health technology fields. In the present study, we investigated the application of the deformable organic ferroelectric in motion measurement and improving performance in tennis players. Flexible ferroelectric material P(VDF-TrFE) could be used in wearable motion sensors in tennis player transferring velocity and acceleration data to collecting devises for analyzing the best pose and movements in tennis players to achieve best performances in terms of hitting ball and movement across the tennis court. In doing so, ferroelectric-based wearable sensors are used in four different locations on the player body to analyze the movement and also a sensor on the tennis ball to record the velocity and acceleration. In addition, poses of tennis players were analyzed to find out the best pose to achieve best acceleration and movement. The results indicated that organic ferroelectric-based sensors could be used effectively in sensing motion of tennis player which could be utilized in the optimization of posing and ball hitting in the real games.

• 제어로봇시스템학회논문지
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• 제16권9호
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• pp.823-826
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• 2010

In this study, the control method of assistive robot was developed for the elderly. The control method of gait-assistant-robot was proposed considering the change of COP (Center of Pelves), BOS (Base of Support) and comparative analysis of the moving velocity for the elderly. We analyzed the movement of COP of the body and its velocity of the elderly equipped with manual walker and gait-assistant-robot. As a result, change in COP was greater from left to right than from anterior to posterior; also, the average velocity of the movement of COP and manual walker for manual walker gait was 0.7(m/s). Therefore, it is necessary to concern more on the left-right balance and synchronization of the velocity of COP.

• 한국운동역학회지
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• 제21권1호
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• pp.39-46
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• 2011

The purpose of this study was to examine differences between players who bend the left elbow and those who stretch it during the forward swing from BST to BC in a 2-handed backhand stroke among outstanding high school tennis players, and to assess the detailed 3D rotational kinematic characteristics of the shoulder and the hip. Statistically significant differences were observed between groups in the longitudinal axis rotation angle of the shoulder and the angle between the shoulder and the arm at BST, and in the side to side movement of the shoulder, the up and down movement of the hip, the side tilt angular velocity of the shoulder, the side tilt angular velocity of the hip, and the front tilt angular velocity of the hip at BC. The difference in the longitudinal axis rotation angle of the shoulder between the 2 groups suggests a difference in the flexibility of the joint in the shoulder arm racquet system. The longitudinal axis rotation angular velocity of the shoulder reached its peak at 75 % of the duration of the analyzed segment and then decreased little by little until BC. This time is considered the stage for increasing the angular velocity of the upper arm, the forearm, the hand and then the racquet, which are more distal segments than the shoulder.

• Interaction and multiscale mechanics
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• 제6권2호
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• pp.157-172
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• 2013

This paper presented an investigation of macromolecular suspension in a grooved channel by using the dissipative particle dynamics (DPD) with finitely extensible non-linear elastic (FENE) bead spring chains model. Before studying the movement and evolution of macromolecules, the DPD method was first validated by modeling the simple fluid flow in the grooved channel. For both simple fluid flow and macromolecular suspension, the flow fields were analyzed in detail. It is found that the structure of the grooved channel with sudden contraction and expansion strongly affects the velocity distribution. As the width of the channel reduces, the horizontal velocity increases simultaneously. Vortices can also be found at the top and bottom corners behind the contraction section. For macromolecular suspension, the macromolecular chains influence velocity and density distribution rather than the temperature and pressure. Macromolecules tend to drag simple fluid particles, reducing the velocity with density and velocity fluctuations. Particle trajectories and evolution of macromolecular conformation were investigated. The structure of the grooved channel with sudden contraction and expansion significantly influence the evolution of macromolecular conformation, while macromolecules display adaptivity to adjust their own conformation and angle to suit the structure so as to pass the channel smoothly.

• 센서학회지
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• 제32권5호
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• pp.307-312
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• 2023

To measure the flow velocity and direction in the near field of an unmanned underwater vehicle, an optical measurement unit containing an image sensor and a phosphor-integrated pillar that mimics the neuromasts of a fish was constructed. To analyze pillar movement, which changes with fluid flow, fluorescence image analysis was conducted. To analyze the flow velocity, mean force analysis, which could determine the relationship between the light intensity of a fluorescence image and an external force, and length-force analysis, which could determine the distance between the center points of two fluorescence images, were employed. Additionally, angle analysis that can determine the angles at which pixels of a digital image change was selected to analyze the direction of fluid flow. The flow velocity analysis results showed a high correlation of 0.977 between the external force and the light intensity of the fluorescence image, and in the case of direction analysis, omnidirectional movement could be analyzed. Through this study, we confirmed the effectiveness of optical flow sensors equipped with phosphor-integrated pillars.

• 한국운동역학회지
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• 제16권4호
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• pp.49-59
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• 2006

The purpose of this study was to investigate the relations between the segments of the body, the three dimensional anatomical angle according to sweep shot in ice hockey. The subjects of this study were five professional ice hockey players. The reflective makers were attached on anatomical boundary line of body. For the movement analysis three dimensional cinematographical method(APAS) was used and for the calculation of the kinematic variables a self developed program was used with the LabVIEW 6.1 graphical programming(Johnson, 1999) program. By using Eular's equations the three dimensional anatomical Cardan angles of the joint and ice hockey stick were defined. 1. In three dimensional linear velocity of blade the Y axis showed maximum linear velocity almost impact, the X axis(horizontal direction) and the Z axis(vertical direction) maximum linear velocity of blade did not show at impact but after impact this will resulted influence upon hitting puck. 2. The resultant linear velocity of each segment of right arm showed maximum resultant linear velocity at impact. It could be suggest that the right arm swing patterns is kind of push-like movement. therefore the upper arm is the most important role in the right arm swing. 3. The three dimensional anatomical angular displacement of trunk in flexion-extension showed flexion all around the wrist shot. The angular displacement of trunk in internal-external rotation showed internal rotation angle at the backswing top and and increased the angle after the impact. while there is no significant adduction-abduction. 4. The three dimensional anatomical angular displacement of trunk showed most important role in wrist shot. and is follwed by shoulder joints, in addition the movement of elbow/wrist joints showed least to the shot. this study result showed upperlimb of left is more important role than upperlimb of right.

• Korean Chemical Engineering Research
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• 제48권4호
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• pp.462-469
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• 2010

기체와 액체가 만나는 2상 공정들은 화학공학, 생명화학공학, 환경공학, 식품공학 등에 두루 존재한다. 위와 같은 공정의 최적화를 위해서는 거품의 움직임과 형태에 대한 정확한 파악이 필요하다. 액체 내부에서 거품의 움직임은 액체의 밀도, 점도, 표면장력과 거품의 크기와 속도에 영향을 받는다. 본 논문에서는 고점도 실리콘 오일 내부에서의 거품의 움직임과 형태를 관찰하였다. 또한 국외 논문 및 저서에서 정립된 거품의 에너지 수지 식, 항력계수와 변형계수를 이용하여 거품의 종말속도, 항력계수, 변형계수, 형태를 예측해 보고 이를 실험결과와 비교해 보았다. 실험 결과 거품의 속도는 점도가 낮을 경우가 더 빨랐고, 거품의 항력계수는 점도가 클 때 더 컸다. 거품의 형태는 점도가 클 때 덜찌그러진(구형에 가까운) 형태였다. 실험결과와 국외 논문 및 저서에서 정립된 항력계수와 변형계수를 이용한 예측결과를 비교해 본 결과 Batchelor가 제시한 이론이 가장 정확한 예측을 하는 것으로 나타났다. Batchelor가 제시한 거품의 에너지 수지식, 항력계수와 변형계수를 사용하여 예측한 거품의 2차원 측면 형태는 실험에서 관찰된 거품의 2차원 측면 형태와 유사하였다.

• 한국운동역학회지
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• 제20권2호
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• pp.139-148
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• 2010

The purpose of this study was to comparatively analyze the kinematic variables between the squash backhand and racquetball backhand strokes through three-dimensional cinematography. Three expert racquetball players and three expert squash players were involved in the data gathering process. The horizontal, vertical and lateral displacement of racket and trunk segment, intersegmental angular velocity of the wrist, elbow and shoulder joints, and the linear velocity of the racket were descriptively analyzed, and the followings were concluded. The racket of the squash backhand stroke showed an 'U' shaped movement where the racket moved rapidly downward and moved forward to make an impact and followed through to a front-top finish, while the racket of racquetball backhand stroke showed an 'O' shaped movement where the racket showed circular movement through the rear and bottom positions for the impact, and showed rotation through the lower-front and upper front to a upper-rear-ward finish during the follow-through. The peak velocity of racket was found before the impact point in the squash backhand stroke and at the impact point in the racquetball backhand stroke. For the final conclusion, for the squash backhand stoke, instructors might be better to make the racket move downward to make highest velocity before the impact and finished short follow-through, while for the racquetball backhand stroke, to make the racket move forward to make highest velocity at the impact and finished rather long follow-through.