• 한국정밀공학회지
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• 제17권3호
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• pp.83-91
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• 2000

During static walking of a quadruped walking robot, stability of the robot depends on whether the projection of the mass center is located within the supporting area that is varying with leg motion and formed by standing legs. In this paper, force margin instead of the mass center was used to determine stability and body-tilting method was used to enhance it. On-line control of body tilting was realized with simple reaction feedback based on force margin of the static walking model of the robot instead of complicated calculation. Model reference on-line control where the model searches stable pose for predefined force margin also gave good walking performance.

• Journal of Korean Dental Science
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• 제8권1호
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• pp.28-35
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• 2015

Purpose: To investigate the influence of crown margin design on the stress distribution and to localize critical sites in maxillary canine under functional loading by using three dimensional finite element analysis. Materials and Methods: The bite force of 100 N, 150 N, and 200 N was applied with an angulation of $45^{\circ}$ to the longitudinal axis of tooth. Six models were restored with IPS e.max (Ivoclar Vivadent, Schaan, Liechtenstein) with a different margin design. With lingual ledge and various thicknesses, three different core ceramics were designed in each model. Result: In the core ceramic, the maximum tensile stresses were found at the labiocervical region. In the veneering ceramic the maximum tensile stresses were found at the area where the force was applied in all models. Conclusion: Shoulder and chamfer margin types are acceptable for all-ceramic rehabilitations. A ledge on the core ceramic at cervical region may affect the strength of all-ceramic crowns.

• 한국지진공학회논문집
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• 제25권3호
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• pp.121-128
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• 2021

Structures of domestic nuclear power plants are designed to perform elastic behavior against beyond design earthquakes, but studies on the nonlinear behavior of structures have been insufficient since the beyond design earthquake. Accordingly, it is judged that it will be necessary to develop an evaluation method that considers the nonlinear behavioral characteristics to check the safety margin for a standard nuclear power plant structure. It is confirmed that the restoring force characteristics for each member level can be identified through the calculation formula, and the lateral stiffness for each story can also be easily calculated by JEAC 4601. In addition, as a result of applying the evaluation method of JEAC 4601 as a nonlinear restoring force model of the nuclear power plant, a certain degree of safety margin can be identified.

• 대한치과기공학회지
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• 제22권1호
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• pp.79-88
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• 2000

The objective of this finite element method study was to analyze the stress distribution induced in a maxillary central incisor Ni-Cr base metal coping ceramic crowns with various margin design. Margin designs of crown in this experiment were knife-edge metal margin on chamfer finishing line of tooth preparation(M1), butt metal margin on shoulder finishing line(M2), reinforced butt metal margin on shoulder finishing line(M3), beveled metal margin on bevelde shoulder finishing line(M4). Two- dimensional finite element models of crown designs were subjected to a simulated biting force of 100N which was forced over porcelain near the lingual incisal edge. Base on plane stress analysis, the maxium von Miss stresses(Mpa) in porcelain venner was 0.432, in metal coping was 0.579, in dentin abutment was 0.324 for M1 model, and M2 model revealed in porcelain was 0.556, in metal coping was 0.511, in dentin was 0.339, and M3 model revealed in porcelain was 0.556, in metal coping was 0.794, in dentin was 0.383 for M4 model. All values of each material in metal-ceramic crown were much below the critical failure values.

• 동력기계공학회지
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• 제14권3호
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• pp.39-45
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• 2010

The dynamic stability of a robot vehicle can be enhanced by the Force-Angle Stability Margin concept that considers a variety of dynamic effects. To evaluate the robot vehicle stability, a SPI(stability performance index), which is a function of the suspension arm angles, was used. If the SPI has a minimum value, the robot vehicle has maximum stability. The FASM and SPI concepts were incorporated in the mobility simulation by using ADAMS and MATLAB/Simulink. The simulation results using these concepts showed significant improvements of the vehicle stability on rough terrains.

• 전자공학회논문지B
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• 제33B권9호
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• pp.1-12
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• 1996

In this paper, we propose an adaptive gait by which a quadruped walking robot can walk against external disturbances. This adaptive gait mechanism makes it possible for a quadruped walking robot to change its gait and accommodate external disturbances form various external environmental factors. Under the assumption that external disturbances can be converted to an external force acting on the body of a quadruped walking robot, we propose a new criterion for the stability margin of a waling robot by using an effective mass center based on the zero moment point under unknown external force. And for a solution of an adaptive gait against external disturbances, an method of altitude control and reflexive direction control is suggested. An algorithmic search method for an optimal stride of the quadruped mehtod, the gait stability margin of a quadruped walking robot is optimized in changing its direction at any instance for and after the reflexive direction control. To verify the efficiency of the proposed approach, some simulaton results are provided.

• 한국지능시스템학회논문지
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• 제19권4호
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• pp.457-463
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• 2009

본 논문에서는 육족 보행 로봇의 새로운 힘 분배 알고리듬을 제안한다. 본 논문에서 고려하는 육족 보행 로봇은 다리 하나에 관절고착고장이 발생하여 내고장성 정적 세다리 걸음새로 보행한다. 제안되는 힘 분배 알고리듬의 핵심은 내고장성 걸음새가 가지는 안정여유도를 결정하는 지지 다리의 미끄러짐을 최소화시키는 것이다. 불연속적으로 움직이는 내고장성 세다리 걸음새는 정상 걸음새보다 안정도가 떨어진다는 약점이 있다. 본 논문에서 제안하는 힘 분배 알고리듬은 이러한 약점을 고려하여 내고장성 걸음새의 지지 다리가 세 개라는 성질과 Zero-Interaction Force 원리를 이용하여 최적화 기법을 쓰지 않고 대수적으로 모든 다리의 힘 성분을 구한다. 컴퓨터 시뮬레이션 사례 연구를 통해서 제안된 힘 분배 알고리듬과 기존 방법의 비교 분석을 실시하고 제안된 방법의 효용성을 입증한다.

• 전기학회논문지
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• 제58권3호
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• pp.614-620
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• 2009

The force distribution in multi-legged robots is a constrained, optimization problem. The solution to the problem is the set points of the leg contact forces for a particular system task. In this paper, an efficient and general formulation of the force distribution problem is developed using linear programming. The considered walking robot is a quadruped robot with a locked-joint failure, i.e., a joint of the failed leg is locked at a known place. For overcoming the drawback of marginal stability in fault-tolerant gaits, we define safety margin on friction constraints as the objective function to be maximized. Dynamic features of locked-joint failure are represented by equality and inequality constraints of linear programming. Unlike the former study, our result can be applied to various forms of walking such as crab and turning gaits. Simulation results show the validity of the proposed scheme.

• 한국운동역학회지
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• 제27권3호
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• pp.205-210
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• 2017

Objective: The aim of the study was to investigate the age-related ability of dynamic balance recovery through perturbation response during standing. Method: Six older and 6 younger adults participated in this study. External perturbation during standing as pulling force applied at the pelvic level in the anterior direction was provided to the subject. The margin of stability was quantified as a measure of postural stability or dynamic balance recovery, and using principal component analysis (PCA), the regularity of the margin of stability (MoS) was calculated. Results: Our results showed that in the older adult group, 60.99% and 28.63% of the total variance were captured using the first and second principal components (PCs), respectively, and in the younger adult group, 81.95% and 10.71% of the total variance were captured using the first and second PCs, respectively. Conclusion: Ninety percent of the total variance captured using the first two PCs indicates that the older adults had decreased regularity of the MoS than the younger adults. Thus, the results of the present study suggest that aging is associated with non-regularity of dynamic postural stability.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.577-580
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• 2005

This paper reports the high sensitivity actuator for flexible disk. The air stabilized flexible optical disk has very small axial runout. Therefore, It is proper to develop an actuator which has high sensitivity in tracking direction rather than in focusing direction. In order to maximize driving force in radial direction, we present an efficient design of magnetic circuit with simple multi-polarized magnets and auxiliary magnets. Designed magnetic circuit has big force in tracking direction. And we shift 2$^{nd}$ resonance frequency of moving parts Into high frequency band, not causing increase of mass and discord between force and mass centers to secure high sensitivities and sufficient control bandwidth. Finally, experimental results show that designed actuator has superior sensitivity in tracking direction.