• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.12
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• pp.1217-1224
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• 2009

A simple and effective guidance and control scheme that enables autonomous three-dimensional path-following for a fixed wing aircraft is presented. The method utilizes the nonlinear path-following guidance law for the outer loop that creates steering acceleration command based on the desired flight path and the current position and velocity of the vehicle. The scheme considers the gravity in the guidance level, where it is subtracted from the acceleration command to form the specific force acceleration command which the aircraft is better suited to follow than the total acceleration command in the inner-loop. A roll attitude control scheme is also presented that enables inverted flight or sideslip maneuvers such as slow roll and knife-edge. A series of aerobatic maneuvers are demonstrated through simulations to show the potential of the proposed scheme.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.8
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• pp.592-599
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• 2014

A torsional vibration at driveline happens seriously at rapid vehicle acceleration. The torsional vibration at driveline can be reduced by optimization of joint angle and yoke phase angle of driveline. But, the joint angle of driveline is changed according to vehicle driving condition as acceleration, deceleration, forward and backward driving, so that excessive vibration is transmitted to vehicle body at specific driving condition. Especially under rapid acceleration condition, vibration transmitted to body could be maximized because excitation force at rapid acceleration is bigger than that at normal driving condition due to changed joint angle. The torsional vibration of driveline can be kept at low level by controlling suspension parameter to minimize rigid axle displacement as well as optimizing joint angles considering the vehicle acceleration condition.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.2
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• pp.106-113
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• 2017

Attitude determination algorithms for aircraft and land vehicles use earth gravitational vector and geomagnetic vector; hence, magnetometers and accelerometers are employed. In dynamic situation, the output from accelerometers includes not only gravitational vector but also motional acceleration, thus it is hard to determine accurate attitude. The acceleration compensation method treated in this paper solves the problem to compensate the specific force vector for motional acceleration calculated by a GPS receiver. This paper analyzed the error from the corrected vector regarded as a constant by conventional acceleration compensation method, and improve the error by rederivation from measurements. The analyzed error factors and improvements by the proposed algorithm are verified by computer simulations.

• Journal of the Korean Institute of Telematics and Electronics T
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• v.36T no.1
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• pp.64-70
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• 1999

When manipulator moves the objects, the object position error can be occurred because of acceleration or negative acceleration according to the direction. So we make manipulator working path for establishing optimal gripper force control preventing occurrence of object position error. And we attached the tactile sensor on the gripper of manipulator which gives us very specific information between manipulator and object. Reasoning of continuous tactile image data, manipulator can sense rotation and slippage and change the grasping force that corrects calculated grasping force and compensation can be possible of the object position error. We use the FSR(Force Sensing Resistor)sensor which consists of 22 by 22 taxels and continuous taxel number is used for filtering and using the moment method for sensing algorithm in our experiment.

• ICROS
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• v.16 no.3
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• pp.40-45
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• 2010

물체의 운동을 측정하기 위하여 관성 센서(inertial sensor)에 대한 배경 지식이 없는 사용자가 가속도계(accelerometer)를 사용하고자 할 경우 센서의 이름이 주는 혼동에 의하여 물체의 운동 가속도(acceleration)를 쉽게 얻어낼 수 있으리라 기대하게 된다. 반면, 가속도계가 실제 측정하여 주는 값은 비력 가속도(acceleration due to specific force)에 해당되므로 적절한 처리를 부가하지 않으면 기대한 바와 같이 물체의 운동 가속도를 얻을 수 없다. 가속도계의 측정값으로부터 운동 가속도를 추출하기 위해서는 중력장 가속도 (gravitational acceleration), 중력 가속도 (acceleration due to gravity), 비력 가속도, 그리고 운동 가속도 사이의 관계를 명확하게 구분 이해할 필요가 있다. 본 고에서는 앞선 고들에서 다룬(막대) 벡터, 좌표값, 좌표계, 좌표변환행렬, 그리고 코리올리 효과 등의 개념을 확장하여 다양한 개념의 가속도들을 구분 설명하였다.

• Earthquakes and Structures
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• v.24 no.1
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• pp.53-64
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• 2023

Earth fissures with several kilometers will inevitably approach or cross the metro line, significantly threatening the safety of the underground structure in the earth fissure site. However, the influence of the earth fissure site's amplification effect on the metro station's dynamic response is still unclear. A representative earth fissure in Xi'an was taken as an example to establish a numerical model of a metro station in the earth fissure site. The dynamic response characteristics of the metro stations at different distances from the earth fissure under various seismic waves were calculated. The results show that the existence of the earth fissure significantly amplifies the dynamic response of the nearby underground structures. The responses of the axial force, shear force, bending moment, normal stress, horizontal displacement, inter-story drift, and relative slip of the metro station were all amplified within a specific influence range. The amplification effect increases with the seismic wave intensity. The amplification effect caused by the earth fissure has relatively weak impacts on the axial shear, shear force, bending movement, normal stress, and horizontal movement; slightly larger impacts on the inter-story drift and acceleration; and a significant impact on the relative slip. The influence ranges of the axial force and normal stress are approximately 20 m. The influence ranges of the acceleration and inter-story drift can reach 30 m. Therefore, the seismic fortification level of the underground structure in the earth fissure site needs to be improved.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.3
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• pp.136-143
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• 2001

A micro particle manipulator, which is devised for trapping particles at fixed positions by negative dielectrophoretic force (DEP force), has been fabricated and experimented. It is composed of square type electrode arrays fabricated by nickel electroplating with the height of 28 ${\mu}m$. To improve the quality of electroplated nickel electrodes, plating conditions have been optimized. Micro particles used in this study are polystyrene spheres and their to the specific position and trapped. The DEP force along the moving path of the particles has been estimated by the motion equation of a single particle. The displacement of a particle with an elapsed time was measured using a high-speed camera (1000 frames/sec). The velocity and acceleration of the particle were calculated from the measured data. The DEP force acting on the particle was estimated.

• International Journal of Control, Automation, and Systems
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• v.4 no.1
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• pp.10-16
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• 2006

In this paper, moving a fragile object from an initial point to a specific location in the minimum time without damage is studied. In order to achieve this goal, initially, the maximum acceleration and velocity ranges are specified. These ranges can be dynamically generate on the planned path by the manipulator. The path can be altered by considering the geometrical constraints. Later, considering the impulsive force constraint on the object, the range of maximum acceleration and velocity are obtained to preserve object safety while the manipulator is carrying it along the curved path. Finally, a time-optimal trajectory is planned within the maximum allowable range of acceleration and velocity. This time-optimal trajectory planning can be applied to real applications and is suitable for both continuous and discrete paths.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.327-332
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• 2006

In airborne gravimetry, there are two data streams. One is the specific force measured by an air/sea gravimeter or accelerometers, the other is kinematic acceleration measured by DGPS. And the difference of them provides the gravity disturbance information. To satisfy the requirement of most applications, an accuracy of 1mGal $(1mCal=10^{-5}m/s^{2})$ with a spatial resolution of 1km is the aim of current airborne gravimetry. There are two different methods to derive the kinematic acceleration. The generally used method is to differentiate the position twice, and the position can be calculated by commercial DGPS software. The main defect of this method is that integer ambiguities need to be fixed to get the precise position solution, but it's not a trivial thing for long base line. And to fix integer ambiguities, the noisier iono-free measurement is used. When differentiation is applied, noise is amplified and will influence the accuracy of acceleration. The other method is to get carrier phase acceleration by differentiate the carrier phase first, and then using the acceleration of GPS satellite to derive the vehicle acceleration. The main advantages include that fixing integer ambiguities is not needed anymore, position can be relaxed to about 10 meters, and smoother acceleration can be got since iono-free measurement is not needed. In some literatures, it's considered that the dynamic performance of the second method is inferior to that of the first. Through analysis, it is found that the performance degradation in dynamic environment results from the simplification of the GPS carrier phase observable model. And an iterative algorithm is presented to compensate the model error. Using a dynamic GPS data from an aeromagnetic survey, the importance of this compensation is showed at last.

• Earthquakes and Structures
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• v.9 no.4
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• pp.875-891
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• 2015

Earthquake can occur anywhere in the world and it is essential to design important members in special structures based on maximum possible forces that can be produced in them under severe earthquake. In addition, since the earthquake is an accidental phenomena and there are no similar earthquakes, therefore the possibility of strong earthquakes should be taken into account in earthquake-resistant design of important structures. Based on this viewpoint, finding the critical acceleration which maximizes internal forces is an essential factor in structural design. This paper proposes critical excitation method to compute the critical acceleration in design of important members in special structures. These critical accelerations are computed so that the columns' internal shear force at the base of the structure at each time step is maximized under constraints on ground motion. Among computed critical accelerations (of each time step), the one which produces maximum internal shear force is selected. A numerical example presents to show the efficiency of critical excitation method in determining the maximum internal shear force and base moment under variety of constraints. The results show that these method can be used to compute the resonant earthquake which have large enough effective duration of earthquake strong motion (between 12.86 sec to 13.38 sec) and produce the internal shear force and base moment for specific column greater than the same value for selected earthquakes in constructing the critical excitation (for different cases about 2.78 to 1.29 times the San Fernando earthquake). Therefore, a group of them can be utilized in developing the response spectrum for design of special structures.