• 한국운동역학회지
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• 제14권3호
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• pp.83-98
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• 2004

The purpose of this study was to investigate the test-retest of plantar pressures using the F-Scan system over speeds and plantar regions. 6 healthy female subjects in 20's were recruited for the study. Plantar pressure measurements during locomotor activities can provide information concerning foot function, particularly if the timing and magnitude of the loading profile can be related to the location of specific foot structures such as the metatarsal heads. The Tekscan F-Scan system consists of a flexible, 0.18mm thick sole-shape having 1260 pressure sensors, the sensor insole was trimmed to fit the subjects' right. left shoes - sneakers shoes & dress shoes. It was calibrated by the known weight of the test subject standing on one foot. The Tekscan measurements show the insole pressure distribution as a function of the time. This finding has important implications for the development of plantar pressure test protocols where the function of the forefoot is important. According to the result of analysis it is as follows 1) Center of force trajectory in women's dress shoes display direct movement, compare with center of force trajectory in Sneaker shoes displays a little bit curved slow pronation movement. Sneaker shoes in forefoot part display very quick supination movement, therefore, this shoes effects negative effectiveness for ankle's stability Considering center of force trajectory analyzing the more center of force close straight line, the more movement can be quick movement for locomotion. For foot pressure distribution, center of force trajectory in locomotion is better to curved trajectory with pronation movement. So sneaker shoes style is good shoes considering center of pressure distribution trajectory compare with women's dress shoes. 2) Women's dress shoes increased peak pressure in medial, this is effected by high hill's height. The more increased women's dress shoes's height, the more women's peak pressure will increase, pronation can increase compare with before. Supination movement increase, this focused pressure in lateral, also, supination increased more. If the supination movement increased, foot pressure focused in lateral, therefore, it is appeared force distribution in gait direction. This is bad movement in foot's stability. 3) Women's dress shoes in landing phase displayed a long time, this is when women's dress shoes wear, gait movement is unbalance, so, landing phase displayed a long time. For compensation in gait, swing phase quick movement. 4) Women's dress shoes displayed peak pressure distribution in lateral of rearfoot part, Sneakers shoes displayed peak pressure distribution in medial of forefoot part. Its results has good impact absorption compare with women's dress shoes. In forefoot part, sneakers shoes has good propulsive force compare with women's dress shoes.

• International Journal of Control, Automation, and Systems
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• 제1권4호
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• pp.474-483
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• 2003

Belt drives provide freedom to position the motor relative to the load and this phenomenon enables reduction of the robot arm inertia. It also facilitates quick response when employed in robotics. Unfortunately, the flexible dynamics deteriorates the positioning accuracy. Therefore, there exists a trade-off between the simplicity of the control strategy to reject time varying disturbance caused by flexibility of the belt and precision in performance. Resonance of the system further leads to vibrations and poor accuracy in positioning. In this paper, accurate positioning of a belt driven mechanism using a feed-forward compensator under maximum acceleration and velocity constraints is proposed. The proposed method plans the desired trajectory and modifies it to compensate delay dynamics and vibration. Being an offline method, the proposed method could be easily and effectively adopted to the existing systems without any modification of the hardware setup. The effectiveness of the proposed method was proven by experiments carried out with an actual belt driven system. The accuracy of the simulation study based on numerical methods was also verified with the analytical solutions derived.

• International Journal of Internet, Broadcasting and Communication
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• 제15권3호
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• pp.176-184
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• 2023

Points of interest (POIs) are widely used in tourism recommendations and to provide information about areas of interest. Currently, situation judgement using POI and GPS data is mainly rule-based. However, this approach has the limitation that inferences can only be made using predefined POI information. In this study, we propose an algorithm that uses POI data, GPS data, and schedule information to calculate the current speed, location, schedule matching, movement trajectory, and POI coverage, and uses machine learning to determine whether to stay or go. Based on the input data, the clustered information is labelled by k-means algorithm as unsupervised learning. This result is trained as the input vector of the SVM model to calculate the probability of moving and staying. Therefore, in this study, we implemented an algorithm that can adjust the schedule using the travel schedule, POI data, and GPS information. The results show that the algorithm does not rely on predefined information, but can make judgements using GPS data and POI data in real time, which is more flexible and reliable than traditional rule-based approaches. Therefore, this study can optimize tourism scheduling. Therefore, the stay detection algorithm using GPS movement trajectories and POIs developed in this study provides important information for tourism schedule planning and is expected to provide much value for tourism services.

• Structural Engineering and Mechanics
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• 제62권5호
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• pp.619-629
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• 2017

This paper focuses on the study of complete dynamic modeling and maximum dynamic load carrying capacity computation of N-flexible links and N-flexible joints mobile manipulator undergoing large deformation. Nonlinear dynamic analysis relies on the Timoshenko theory of beams. In order to model the system completely and precisely, structural and joint flexibility, nonlinear strain-displacement relationship, payload, and non-holonomic constraints will be considered to. A finite element solution method based on mixed method is applied to model the shear deformation. This procedure is considerably more involved than displacement based element and shear deformation can be readily included without inducing the shear locking in the element. Another goal of this paper is to present a computational procedure for determination of the maximum dynamic load of geometrically nonlinear manipulators with structural and joint flexibility. An effective measure named as Moment-Height Stability (MHS) measure is applied to consider the dynamic stability of a wheeled mobile manipulator. Simulations are performed for mobile base manipulator with two flexible links and joints. The results represent that dynamic stability constraint is sensitive when calculating the maximum carrying load. Furthermore, by changing the trajectory of end effector, allowable load also changes. The effect of torsional spring parameter on the joint deformation is investigated in a parametric sensitivity study. The findings show that, by the increase of torsional stiffness, the behavior of system approaches to a system with rigid joints and allowable load of robot is also enhanced. A comparison is also made between the results obtained from small and large deformation models. Fluctuation range in obtained figures for angular displacement of links and end effector path is bigger for large deformation model. Experimental results are also provided to validate the theoretical model and these have good agreement with the simulated results.

• 한국해양환경ㆍ에너지학회지
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• 제1권1호
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• pp.56-65
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• 1998

해상 누유의 이동경로 및 풍화와 관련된 여러 물리현상들의 모델링 기법들이 검토되었으며, 이에 기초한 해상누유 확산 예측모델 "푸른바다"가 소개된다. 실시간 누유확산을 시뮬레이션하기 위해서는 조류에 관한 데이터베이스가 필수적이며, 본 연구에서는 누유 사고가 빈번한 남해안 일대의 조류 데이터베이스가 구축되었다 남해 조석류의 실시간 예측을 위해 4개의 주요분조(M₂, S₂, K₁, O₁ 조석류)를 채택하였으며, 각 분조들의 각속도와 위상 값들은 천문상수들로부터 얻어진다. 주요분조들의 조화상수는 천해 조류 방정식을 풀어 구한다. 푸른바다는 사용자 편의성의 극대화와 해양환경 데이터베이스의 확장이 용이한 유연한 구조를 그 특징으로 한다. 매몰도 인근해역에서 좌초되어 누유를 발생시켰던 오성호 사고를 시뮬레이션함으로서 푸른바다의 유효성을 검증하였다. 시뮬레이션 결과를 관측된 누유확산 경로와 비교하였으며, 이를 통해 푸른바다가 누유의 거동 예측에 있어 타당한 추정치를 줄 수 있음을 확인하였다.

• Investigative Magnetic Resonance Imaging
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• 제25권4호
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• pp.293-299
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• 2021

Purpose: To accelerate magnetic resonance fingerprinting (MRF) by developing a flexible deep learning reconstruction method. Materials and Methods: Synthetic data were used to train a deep learning model. The trained model was then applied to MRF for different organs and diseases. Iterative reconstruction was performed outside the deep learning model, allowing a changeable encoding matrix, i.e., with flexibility of choice for image resolution, radiofrequency coil, k-space trajectory, and undersampling mask. In vivo experiments were performed on normal brain and prostate cancer volunteers to demonstrate the model performance and generalizability. Results: In 400-dynamics brain MRF, direct nonuniform Fourier transform caused a slight increase of random fluctuations on the T2 map. These fluctuations were reduced with the proposed method. In prostate MRF, the proposed method suppressed fluctuations on both T1 and T2 maps. Conclusion: The deep learning and iterative MRF reconstruction method described in this study was flexible with different acquisition settings such as radiofrequency coils. It is generalizable for different in vivo applications.

• 한국컴퓨터정보학회논문지
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• 제27권2호
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• pp.9-14
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• 2022

본 연구에서는 유연성을 가지는 공기 조형물과 같은 기구물이 사용자가 원하는 자세를 안정적으로 유지하며 이동하기 위한 방안을 제안한다. 이를 수행하기 위해 IMU를 이용한 수평 유지 자세 제어와 PI 알고리즘을 적용하여 주어진 궤적에 따라 주행이 가능한 이동로봇의 구조를 가지는 로봇 시스템을 연구하였다. 본 연구에서 사용된 공기 조형물은 고정된 자세로 얇은 끈을 이용하는 경우가 많다. 다른 방법으로는 무게 중심부에 하중을 실어 자세를 유지며 공기의 압력을 사용하므로 유연성을 가지는 시스템이다. 이러한 구조물은 디지털 센서 기술의 융합과정을 통해 유연한 형태의 구조물과 이동로봇의 결합으로 다양한 성과를 얻을 수 있을 것으로 기대한다. 본 연구는 로봇의 한 분야인 AGV(무인 반송차)의 주행 기술과 다양한 센서를 응용한 기술들을 융합하여 자세제어를 수행하였다. 검증은 공인인증시험을 통해 주어진 성능 평가를 수행하였으며 실험을 통해 그 타당성을 검증하였다.

• 한국정밀공학회지
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• 제2권1호
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• pp.41-52
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• 1985

This study is a step in developing the sliding mode control methodology for the robust control of a class of nonlinear time-varying systems. The methodology uses in its idealized form piecewise continuous feedback control, resulting in the state trajectory "sliding" slong a time-varying sliding surface in the state space. This idealized control law achieves perfect tracking. The method is applied to the control of a two-link manipulator handling variable loads in a flexible manufacturing system environment with noise. The result through simulation is that the tracking problem of articular robot with high precision can be realized by using the variable structure system (VSS) theory. The motions of articular robot were insensitive to various payloads. payloads.

• 로봇학회논문지
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• 제3권4호
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• pp.315-322
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• 2008

A new soft finger mechanism using a spring as a backbone is proposed in this work. It is a 4 DOF mechanism that consists of a spring and 3 cylinders, which behave like joints with 3 up-and-down rotations and 1 left-and-right rotation. To control each joint, cylinders have small holes in their cross-sectional areas, and wires of different length are penetrated into these holes. We can control each joint by pulling the corresponding wire. The forward kinematics is solved by using the geometry of mechanism. And the relationship (Jacobian) between the linear velocity of the wires and the joint angular rate is obtained. A virtual simulator is developed to test the validity of the kinematic model. In the experiment, first, the position control is conducted by tracking a given trajectory. Second, to verify the flexibility and safety, we show that the soft finger deflects in a safe manner, in spite of the collision with environment.

• 대한기계학회논문집A
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• 제26권2호
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• pp.399-405
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• 2002

This paper proposes a new type of piezoactuator-driven valve system. The piezoceramic actuator bonded to both sides of a flexible beam surface makes a movement required to control the pressure at the flapper-nozzle of a pneumatic valve system. After establishing a dynamic model, an appropriate size of the valve system is designed and manufactured. Subsequently, a robust H$_{\infty}$ control algorithm is formulated in order to achieve accurate tracking control of the desired pressure. The controller is experimentally realized and control performance for the sinusoidal pressure trajectory is presented in time domain. The control bandwidth of the valve system, which directly represents the fastness, is also evaluated in the frequency domain.