• Journal of Astronomy and Space Sciences
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• 제15권1호
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• pp.209-220
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• 1998

The stability problem of steady motion of a rigid body with multi-elastic appendages and multi-liquid-filled cavities, in the presence of no external forces or torque, is considered in this paper. The flexible appendages are modeled as the clamped -free-free-free rectangular plates, or/and as the discrete mass- spring sub-system. The motion of liquid in every single ellipsoidal cavity is modeled as the uniform vortex motion with a finite number of degrees of freedom. Assuming that stationary holonomic constraints imposed on the body allow its rotation about a spatially fixed axis, the equation of motion for such a systematic configuration can be very complex. It consists of a set of ordinary differential equations for the motion of the rigid body, the uniform rotation of the contained liquids, the motion of discrete elastic parts, and a set of partial differential equations for the elastic appendages supplemented by appropriate initial and boundary conditions. In addition, for such a hybrid system, under suitable assumptions, their equations of motion have four types of first integrals, i.e., energy and area, Helmholtz' constancy of liquid - vortexes, and the constant of the Poisson equation of motion. Chetaev's effective method for constructing Liapunov functions in the form of a set of first integrals of the equations of the perturbed motion is employed to investigate the sufficient stability conditions of steady motions of the complete system in the sense of Liapunov, i.e., with respect to the variables determining the motion of the solid body and to some quantities which define integrally the motion of flexible appendages. These sufficient conditions take into account the vortexes of the contained liquids, the vibration of the flexible components, and coupling among the liquid-elasticity solid.

• 전기학회논문지
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• 제64권1호
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• pp.136-142
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• 2015

In the paper, a design method of knee and pelvis joint in the biped robot is proposed for shock absorption and gravity compensation. Similarly to the human's body, the knee joints of the biped robot support most body weight and get a shock from the landing motion of the foot on the floor. The torque of joint motor is also increased sharply to keep the balance of the robot. Knee and pelvis joints with the spring are designed to compensate the gravity force and reduce the contact shock of the robot. To verify the efficiency of the proposed design method, we develope a biped robot with the joint mechanism using springs. At first, we experiment with the developed robot on the static motions such as the bent-knee posture both without load and with load on the flat ground, and the balance posture on the incline plane. The current of knee joint is measured to analyze the impact force and energy consumption of the joint motors. Also, we observe the motor current of knee and pelvis joints for the walking motion of the biped robot. The current responses of joint motors show that the proposed method has an effect on shock reduction and gravity compensation, and improve the energy efficiency of walking motions for the biped robot.

• 대한치과교정학회지
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• 제36권4호
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• pp.295-307
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• 2006

이 연구의 목적은 교정용 고정원으로 사용된 self-drilling과 self-tapping microscrew implants를 조직학적 및 생역적으로 비교하는 것이다. 28 마리의 가토에 112개의 microscrew implants (56개의 self-drilling microscrew implants 와 56개의 self-tapping microscrew implants)를 식립하였다. Self-tapping microscrew implants는 0.9 mm 드릴로서 홈을 형성한 후 식립하였고 self-drilling microscrew implants는 홈을 형성하지 않고 바로 식립하였다. 교정력은 식립 직후 바로 NiTi coil spring을 연결하여 가하였으며 일부는 교정력을 가하지 않았고 일부는 100 gm정도의 약한 교정력을 일부는 200 gm정도의 강한 교정력을 가하였다. 실험동물은 3주 혹은 5주에 희생하였으며 72개의 비탈회 표본을 만들어 전반적인 조직학적 관찰과 조직 계측을 시행하였다. 토크 게이지로 최대 식립 토크와 최대 제거 토크를 측정하였다. 모든 microscrew implants는 실험기간 동안 안정되게 유지되었고 최대 제거 토크의 측정에는 self-drilling과 self-tapping microscrew implants 사이에 통계학적으로 유이한 차이가 없었다. 조직 관찰에서 self-tapping microscrew implants에서 골 임프란트 계면에 골결손이 더 많았고 5주에서는 새로이 형성된 미성숙 골이 더 많았다. Self-drilling microscrew implants에서 골표면 혹은 골내막으로의 골 형성이 많이 관찰되었으나 5주에서는 흡수되는 양상을 보였다. 3주에서는 self-drilling microscrew implants가 더 많은 골접촉을 보였으나 5주에서는 두 군사이에 차이가 관찰되지 않았다. 이 결과는 두 방법이 모두 microscrew implant의 식립에 사용될 수 있음을 시사하나 self-tapping microscrew implants의 경우 초기에는 약한 힘을 가하는 것이 좋을 것으로 생각된다.

• 한국산학기술학회논문지
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• 제18권10호
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• pp.102-109
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• 2017

디젤 분사시스템의 고압펌프는 저압으로 공급된 연료를 압축하여 고압 연료로 만들고 엔진 작동조건에 따라 커먼레일의 연료를 요구되는 압력수준으로 유지한다. 고압펌프는 차량의 전체 수명기간 동안 연료를 2000 bar에 달하는 고압으로 압축하여 원활히 동작해야 하므로 설계기술, 재료의 내구성, 고도의 가공정밀도가 요구된다. 이 연구에서는 1-플런저 레이디얼 피스톤 펌프 형태의 고압펌프에 대한 시뮬레이션 모델을 상용 소프트웨어인 AMESimpp의 서브 모델들을 이용하여 개발하고, 고압펌프의 동작특성을 살펴보기 위해 시뮬레이션을 실시한다. 주요한 시뮬레이션 내용들은 입구 및 출구 밸브의 변위, 유량, 압력 특성, 캠의 토크 특성, 그리고 연료 미터링밸브의 압력 제어 특성과 오버플로밸브의 동작 특성이다. 또한 입구 밸브의 구멍지름과 스프링 초기력 등의 파라미터 변화에 따른 입구 및 출구 밸브의 유량과 커먼레일 압력 등의 고압펌프의 동작 특성과 응답 특성을 시뮬레이션을 통해 검토한다. 이를 통해서 개발된 펌프 모델의 동작이 논리적으로 타당함을 제시하고, 고압펌프를 설계변경하거나 개발초기에 설계변수들의 설정과 튜닝에 활용할 수 있는 시뮬레이션 모델을 제안한다.

• Journal of Biosystems Engineering
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• 제2권1호
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• pp.7-24
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• 1977

This paper is the forth and fifth one of the study on balanced type oscillating mole drainer. In the light of the results from previous reports about the model tests, some design criteria were established and a prototype machine was set up for experimental purpose. Motion characteristics and functionof the each parts of the machine were checked and analyzed. After that, performance tests of the prototype machine were carried out in thefield. Obtained results are summarized as follows ; 1. Ten centimeter of the bullet diameter was determined so as to be able to attach it to the tractors with capacity of 30 PS to 40 PS. 2. To maintain the balance between the moments of the front shank and rear shank, the oscillating amplitude of the rear bullet was determined to be larger than that of the front bullet. At the same time , the oscillating direction of the rear bullet was designed with the inclines of ten to thirty degrees. 3. An octagonal dynamo transduced was developed for measuring the compressive force of the upper link is measuring the draft force of the machine. Acceptable linear relationship between forces and strain responses from O.D.T. was obtained. 4. Analysing the balancing mechanism of the acting part of the machine , it was found that the total draft force of the machine was equal to the difference between the sum of the draft force produced from the right and left side bending moments of the lower drawber and the compressive force on the upper link. 5. There are acceptable linear relationship between the strain and twisting moment by driving shaft, and between strain and shank moment. Above results enable us to carry out the field experiment with prototype machine. 6. When the test machine was used in the field, it was possible to reduce the oscillating acceleration by forty percent in average as compared it with the single bullet mole drainer. 7. When the test machine was used under the oscillating condition, the dratt torce was reduced by 27 percent to 59 percent as compared it with the test machine under non-oscillating condition, while the draft force was increased by 7 percent to 20 percent as compared it with the mole drainer having oscillating single bullet. The reasoning behind this fact was considered as the resistance force due to the rear shank and bullet. 8. As the amplitude and frequency of the bullet were increased, the torque was increased accordingly. This tendency could be varied with the various characteristics of the given soils. And the larger frequency and amplitute, the more increasing oscil\ulcornerlating power but decreasing draft brce were needed, and draft force was increased as the velocity was increased.9. When the amplitude of the rear bullet was designed to be larger than that of the front bullet, the minimum value of the moment was lowered and oscillating acceleration was reduced. And when the oscillating direction of the rear bullet was declined back\ulcornerwards, oscillating acceleration was increased along with the increasing angle of decli\ulcornernation. When the test machine was operated in high speed, the difference between maximum moments and minimum ones became narrow. This varying magnitude of moments appeared on the moment oscillogram seems to be correlated to the oscillating acceleration and draft force. 10. From the analysis of variance, it was found that those factors such as frequency, amplitude, and operating velocity significantly affected in the oscillating acceleration, the draft resistance, the torque, the moment, and the total power required. And interaction between frequency and amplitude affected in the oscillating acceleration. 11. Within the given situation of this study, the most preferable operating conditions of the test machine were 7 Hz in oscillating frequency, 0.54 m/sec in operating velocity, and 39.1 mm in oscillating amplitude of front and rear bullets. However, it is necessary to select the proper frequency and magnitude of oscillation depending on the soil properties of the field in which the mole drainer is practiced by use of a bal1nced type oscillating mole drainer. 12. It is recommended that a comparative study of the mole drainers would be performed in the near future using two separate balanced oscillating bullet with the one which is operated by oscillating the movable bullet in a single cylinder or other balanced type which may be single oscillating bullet with spring, damper or balancing weight, and that of thing. To expand the applicability of the balanced type oscillating mole drainer in practical use, it is suggested to develop a new mechanism which perform mole drain with vinyl pipe or filling material such as rice hull.