• Proceedings of the KIEE Conference
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• 2000.11d
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• pp.765-768
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• 2000

Linearization of the biped dynamic equations and design of linear controller for the linearized equations are studied in this paper. The biped robot with inverted pendulum type trunk, used to stabilize the dynamic balancing of the biped robot during dynamic walking period, is modelled with 14 DOF and simulated. Despite of well defined linear control theories so far, the linear control methods was limited to the applications for a walking robot, because they have been inherently strong nonlinear properties, such as a modeling parameter uncertainties, external forces as noise, inertial and Coriolis terms by three dimensional modeling and so on. To linearize the nonlinear equations of motion of biped robot on MIMO and time varying linear equations of motion, 1st order Taylor series is used to formulate the linear equation. And a 2nd order numerical perturbation method Is used to approximate partial differential equations. Using the linearized equations of motion, a linear controller is designed by pole placement method with feed forward compensation. Using the obtained linearized equations and linear controller, the continuous walking simulation is performed.

• Current Optics and Photonics
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• v.2 no.1
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• pp.1-6
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• 2018

Our previous study showed that switching the inhaled gas from hypoxic gas to hyperoxic gas for 10 minutes increased tumor oxygenation and that the magnitude of oxyhemoglobin increase responded earlier than tumor volume change after chemotherapy. During 10 minutes of inhaled-oxygen modulation, oxyhemoglobin concentration first shows a rapid increase and then a slow but gradual increase, which has been fitted with a double-exponential equation in this study. Two amplitude values, amplitudes 1 and 2, respectively represent the magnitudes of rapid and slow increase of oxyhemoglobin. The trends of changes in amplitudes 1 and 2 were different, depending on tumor volume when chemotherapy started. However, both amplitudes 1 and 2 changed earlier than tumor volume, regardless of when chemotherapy was initiated. These results imply that by observing amplitude 1 changes post chemotherapy, we can reduce the time of a respiratory challenge from 10 minutes to less than 2 minutes, to see the chemotherapy response. We believe that by reducing the time of the respiratory challenge, we have taken a step forward to translating our previous study into clinical application.

• Journal of Institute of Control, Robotics and Systems
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• v.16 no.12
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• pp.1233-1240
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• 2010

In the flat panel display and semiconductor industries, the visual alignment system is considered as a core technology which determines the productivity of a manufacturing line. It consists of the vision system to extract the centroids of alignment marks and the stage control system to compensate the alignment error. In this paper, we develop a Kalman filter algorithm to estimate the alignment mark postures and propose a coarse-fine alignment control method which utilizes both original fine images and reduced coarse ones in the visual feedback. The error compensation trajectory for the distributed joint servos of the alignment stage is generated in terms of the inverse kinematic solution for the misalignment in task space. In constructing the estimation algorithm, the equation of motion for the alignment marks is given by using the forward kinematics of alignment stage. Secondly, the measurements for the alignment mark centroids are obtained from the reduced images by applying the geometric template matching. As a result, the proposed Kalman filter based coarse-fine alignment control method enables a considerable reduction of alignment time.

• The korean journal of orthodontics
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• v.17 no.1
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• pp.55-62
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• 1987

Diagnosis and treatment plans of patients are depended on cephalogram in most case. However, conventional cephalogram may change diagnosis because it ignores a conception of natural head position. The purpose of this study was to investigate the difference of head positions between conventional X-ray taking and x-ray taking in natural head position, and correlation between above results and craniofacial morphology, 60 male students in dental college, Yon sei Univ. were selected, and every cephalogram is studied by comparison of the change of head position. The results are as follows. 1. When taking X-ray by using conventional method, external auditary meatus FH was more tilted than ear rod FM by $2.1^{\circ}{\pm}1.8$ in forward and downward direction. 2. As facial form becomes concave, natural head position and head position, appeared in X-ray taking by using conventional method, become more similiar. 3. Change in head position had showed high correlations with facial form (N-A-Pog angle), and there was high significance to concave group when compared with average group, but significance to convex group was not found. 4. Multiple regression equation concerning change of head position was solved. ${\Delta}FH=24.5\;+\;0.31$ NAPog + 0.43 Prominence of Chin + 0.13 Facial length -0.32 Anterior facial height.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.7
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• pp.144-153
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• 1997

The inverse kinematics problem of a reclaimer which excavates and transports raw materials in a raw yard is investigated. Because of the geometric feature of the equipment in which scooping buckets are attached around the rotating disk, kinematic redundancy occurs in determining joint variable. Link coordinates are introduced following the Denavit-Hartenbery representation. For a given excavation point the forward kinematics yields 3 equations, however the number of involved joint variables in the equations is four. It is shown that the rotating disk at the end of the boom provides an extra passive degree of freedom. Two approaches are investigated in obtaining inverse kinematics solutions. The first method pre-assigns the height of excavation point which can be determined through path planning. A closed form solution is obtained for the first approach. The second method exploits the orthogonality between the normal vector at the excavation point and the z axis of the end-effector coordinate system. The geometry near the reclaiming point has been approximated as a plane, and the plane equation has been obtained by the least square method considering 8 adjacent points near the point. A closed form solution is not found for the second approach, however a linear approximate solution is provided.

• Structural Engineering and Mechanics
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• v.27 no.6
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• pp.697-711
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• 2007

Though extensive research has been carried out for the ultimate strength of steel reinforced concrete (SRC) members under static and cyclic load, there was only limited information on the applied analysis models. Modeling of the inelastic response of SRC members can be accomplished by using a microcosmic model. However, generally used microcosmic model, which usually contains a group of parameters, is too complicated to apply in the nonlinear structural computation for large whole buildings. The intent of this paper is to develop an effective modeling approach for the reliable prediction of the inelastic response of SRC columns. Firstly, five SRC columns were tested under cyclic static load and constant axial force. Based on the experimental results, normalized trilinear skeleton curves were then put forward. Theoretical equation of normalizing point (ultimate strength point) was built up according to the load-bearing mechanism of RC columns and verified by the 5 specimens in this test and 14 SRC columns from parallel tests. Since no obvious strength deterioration and pinch effect were observed from the load-displacement curve, hysteresis rule considering only stiffness degradation was proposed through regression analysis. Compared with the experimental results, the applied analysis model is so reasonable to capture the overall cyclic response of SRC columns that it can be easily used in both static and dynamic analysis of the whole SRC structural systems.

• Journal of Institute of Control, Robotics and Systems
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• v.10 no.10
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• pp.869-877
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• 2004

This paper deals with motion planning algorithm for kinematically redundant manipulators that are not fixed to the ground. Differently from usual redundant manipulators fixed to the ground, the stability issue should be taken into account to prevent the robot from falling down. The typical ZMP equation, which is employed in human walking, will be employed to evaluate the stability. This work proposes a feed forward ZMP planning algorithm. The algorithm embeds the 'ZMP equations' indirectly into the kinematics of the kinematic model of a manipulator via a ZMP stability index The kinematic self motion of the redundant manipulator drives the system in such a way to keep or plan the ZHP at the desired position of the footprint. A sequential redundancy resolution algorithm exploiting the remaining kinematic redundancy is also proposed to enhance the performances of joint limit index and manipulability. In addition, the case exerted by external forces is taken into account. Through simulation for a 5 DOF redundant robot model, feasibility of the proposed algorithms is verified. Lastly, usual applications of the proposed kinematic model are discussed.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.1
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• pp.87-93
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• 2014

Conventional two-wheeled balancing robots are limited in terms of turning speed because they lack the lateral motion to compensate for the centrifugal force needed to stop rollover. In order to improve lateral stability, this paper suggests a two-wheeled balancing mobile platform equipped with a tilting mechanism to generate roll motions. In terms of static force analysis, it is shown that the two-body sliding type tilting method is more suitable for small-size mobile robots than the single-body type. For the mathematical modeling, the tilting-balancing platform is assumed as a 3D inverted pendulum and the four-degrees-of-freedom equation of motion is derived. In the velocity/posture control loop, the desired tilting angle is naturally determined according to the changes of forward velocity and steering yaw rate. The efficiency of the developed tilting type balancing mobile platform is validated through experimental results.

• Journal of Electrical Engineering and Technology
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• v.11 no.3
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• pp.653-661
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• 2016

This paper proposes a capacitance estimation method of the dc-link capacitor for brushless DC motor (BLDCM) drive systems. In order to estimate the dc-link capacitance, the BLDCM is operated in quadrant-II or -IV among four-quadrant operation. Quadrant-II and -IV are called reverse braking and forward braking, respectively. During the braking operation of the BLDCM, the capacitor is charged by the phase current and then the voltage is increased during the braking operation time. The capacitor current and voltage can be obtained by using the phase current sensor of BLDCM and the dc-link voltage sensor. The capacitance and be easily obtained by the voltage equation of the capacitor. The proposed method guarantees the reliable and simple calculation of the dc-link capacitance without additional hardware system except several the sensors already installed for the motor control system. The effectiveness of the proposed method is verified through both the simulation and experimental results.

• Geomechanics and Engineering
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• v.14 no.3
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• pp.241-246
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• 2018

The displacement monitoring data series reconstruction method was developed under equal water level effects based on displacement monitoring data of concrete dams. A dam displacement variation equation was set up under the action of temperature and aging factors by optimized analysis techniques and then the dam displacement hydraulic pressure components can be separated. Through the dynamic adjustment of temperature and aging effect factors, the aging component isolation method of dam displacement was developed. Utilizing the isolated dam displacement aging components, the dam stability model was established. Then, the dam stability criterion was put forward based on convergence and divergence of dam displacement aging components and catastrophe theory. The validity of the proposed method was finally verified combined with the case study.