• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.4
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• pp.241-250
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• 2022

This paper addresses the Feasible Angular Momentum(FAM) chart that can be used as an indicator for maneuverability analysis of spacecraft installed with control moment gyros(CMGs). Recently, as the demands for high agility of spacecraft has been increasing in order to perform the space mission given to spacecraft more effectively, interest in CMGs, which is a high torque generator is increasing. However, since the CMG has a singularity problem that does not generate the control torque in the specific directions, in this paper, we consider the two pairs of parallel control moment gyros(TPCMGs) that follows the roof-type configuration. The Gimbal space was newly defined except for the space where singularity can be generated and the space where torque error is generated due to the hardware limits. The feasible angular momentum space is defined as a FAM chart, and it is very meaningful that it is possible to analyze the spacecraft's rotational maneuverability effectively by deriving the spacecraft's 3-axis parameters in the corresponding gimbal space mathematically.

• Restorative Dentistry and Endodontics
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• v.31 no.3
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• pp.179-185
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• 2006

This study was conducted to evaluate canal configuration after shaping by $ProTaper^{TM}$ with various rotational speed in J-shaped simulated resin canals. Forty simulated root canals were divided into 4 groups, and instrumented using by $ProTaper^{TM}$ at the rotational speed of 250, 300, 350 and 400 rpm. Pre-instrumented and post-instrumented images were taken by a scanner and those were superimposed. Outer canal width, inner canal width, total canal width, and amount of transportation from original axis were measured at 1, 2, 3, 4, 5, 6, 7 and 8 mm from apex. Instrumentation time, instrument deformation and fracture were recorded. Data were analyzed by means of one-way ANOVA followed by Scheffe's test. The results were as follows 1. Regardless of rotational speed, at the $1{\sim}2mm$ from the apex, axis of canal was transported to outer side of a curvature, and at 3~6 mm from the apex, to inner side of a curvature. Amounts of transportation from original axis were not sienifcantly different among experimental groups except at 5 and 6 mm from the apex. 2. Instrumentation time of 350 and 400 rpm was significantly less than that of 250 and 300 rpm (p<0.01). In conclusion the rotational speed of $ProTaper^{TM}$ files in the range of $250{\sim}400rpm$ does not affect the change of canal configuration, and high rotational speed reduces the instrumentation time. However appearance of separation and distortion of Ni-Ti rotary files can occur in high rotational speed.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.76-76
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• 2017

4륜 승용관리기는 보통 후방이나 전방에 작업기를 장착하여 작업하나 3륜 승용관리기는 작업기를 복부에 장착함으로 작업의 정밀도, 편이성, 관측의 용이성 향상과 함께 지상고 제고, 차폭 조절, 조향 등의 성능 개선을 기할 수 있다. 국내에서는 3륜 승용관리기용 복부 장착 부속작업기가 거의 개발되어 있지 않으며, 특히 두류 재배에 있어서 일관기계화 작업을 위한 관리작업기의 개발이 매우 필요한 실정이다. 승용관리기의 중경배토기에 의한 작업은 기존 인력에 의한 작업보다 약 87%의 노력을 절감할 수 있으며, 잡초방제 효과도 인력에 비하여 크게 떨어지지 않고, 수량도 증가하는 것으로 보고되고 있다. 따라서 본 연구는 3륜 승용관리기에 적합한 복부장착형의 중경배토기를 설계 제작하였다. 3륜 승용관리기용 중경배토기는 승용관리기의 복부 PTO에서의 구동력 전달을 위한 연결 조인트, 중간축, 기어 및 체인 전동기구, 구동축으로 구성된 동력전달부, 4개의 로타리 날과 후방 1개의 배토날로 구성된 3조의 작업날, 로타리 날과 배토날의 경심 조절을 위한 3조의 바퀴, 흙의 비산 방지를 위한 로타리날 커버 및 케이스, 다양한 조간거리에 적응을 위한 조간조정 나사부, 3륜 승용관리기에의 부착을 위한 프레임 및 부착보조 작업기 이동용 바퀴장치 등으로 구성 설계 제작하였다. 로타리 날과 배토날은 기존 시판 관리기용 날을 사용하였다. 로타리 날은 진행방향으로 회전하도록 하였으며, 날의 회전반경은 약 330 mm, 조당 경운 폭은 약 230 mm 설계하였다. 최대 경심은 100 mm이며, 조간거리의 조절범위는 수동 나사에 의하여 620~900 mm 범위로 무단조절 할 수 있도록 하였다. 중경제초기는 3륜 승용 관리기 복부의 평행링크에 부착되므로 작업기의 이동 및 부착 편이를 위하여 이동용 바퀴를 설치하였다. 제작된 중경배토기의 크기는 길이${\times}$폭${\times}$높이가 $660{\times}2072{\times}880mm$, 중량은 약 200 kg으로 제작되었다.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.4
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• pp.708-716
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• 2013

This study aims to understand the applied forces and related vibrational characteristics of a tripod joint (TJ), which is mostly used in front-drive-type middle-sized sedans in South Korea. The plunging force (PF) and generated axial force (GAF) are the most influential quantities related to the vibrational characteristics of a driveshaft. To obtain meaningful data, specially designed tests were performed using MTS test sets. The results of direct measurements reveal that higher PF and GAF values appear to worsen the vibrational characteristics of the vehicle. On the other hand, the measured apparent mass is useful for calculating the applied forces for a short driveshaft that has no dynamic vibration absorber. Among diversely controlled samples, it shows that the viscosity and tight fit are very sensitive to shudder vibrations of the vehicle. Therefore, these are good design factors for quality controls in the production line of constant-velocity joints.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.4
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• pp.1453-1459
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• 2012

The dual stage manipulator is composed of the voice coil motor (VCM) and piezoelectric ceramics transducer (PZT), which can produce the high precise displacement and express a well dynamic performance. However, inaccurate modeling of the dual stage will exacerbate the positioning accuracy. This paper presents an approach to model the dual stage system by using bond graph theory. And the state space equations can be derived through the bond graph straightforwardly, which can be used in computing simulations. Through designing the compensators for the dual stage system and simulating, the dual stage performs better dynamics characteristic than the single actuator system.

• Journal of Institute of Control, Robotics and Systems
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• v.14 no.4
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• pp.385-391
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• 2008

To effectively cope with a complexity of kinematic metrology due to workspace enlargement of the planar stage, the linear induction motor is suggested as its new driving source. Especially, the linear induction motor under uniform plate type of secondary doesn't inherently have a periodical force ripple which is generally shown in the brushless DC motor. But, it presents a poor transient characteristic at zero or low speed zone owing to time delay of flux settling, resulting in slow response. To improve the servo property of linear induction motor and apply successfully it to the precision stage, this paper discusses a modified vector control methodology. The controller has a novel input form, fixed d-axis current, q-axis current and forward-fed DC current, to control thrust force and normal force of the linear induction motor independently. Influence of the newly introduced input and the feasibility of controller are validated experimentally.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.6
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• pp.580-586
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• 2015

A brushless DC (BLDC) motor control system for four-axis driving fins to control the flight attitude of a guided artillery munition is developed in this study. This system adopts a simple sensorless control scheme without a Hall sensor. A 12-step driving sensorless BLDC motor scheme is used to improve the output torque. This system has many restrictive problems that hinder the verification of a real system. For example, this has cost and environmental limitations. Therefore, this study develops HILS to verify a four-axis driving fin control system and verifies the position control system hardware by HILS operation.

• Journal of Biomedical Engineering Research
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• v.16 no.4
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• pp.543-554
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• 1995

This paper describes the improvement of driving stability and the control system for INMEL-VII which is motorized manual wheelchair to satisfy requirements of the disabled The INMEL-VI was based on high maneuverability of the omnidirection drive and safety But the results of field tests about two years showed some problems to the disabled in daily life such as driving stability, Pm switching noise, and rotation of motor without driving command on negative slope. To solve the problems due to an increased DC motor power and applied to direct connection method in INMEL- VII. It improved the driving circuits and set switching frequency to 5KHz to eliminate the switching noise caused by PWM control of DC motor, As compare with the INMEL-VI, INMEL-VII is improved in driving stability by transfer the weight center to forward. The results of field testing proved the improvement of the driving stability and software algorithm It has been estimated to have a hlgh practical use for powered walking aids to the disabled's daily life.

• Journal of the Institute of Convergence Signal Processing
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• v.6 no.4
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• pp.191-197
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• 2005

Biped walking is the main feature of a humanoid robot. In a biped walking robot, there are many actuators to be controlled and many sensors to be interfaced. In this paper, we propose a DSP-based controller for a miniature biped walking robot with 21 RC servo motors. The proposed controller has a hierarchical structure; a host PC, a DSP-based main controller, and an auxiliary controller with an FPGA chip. The host PC generates and transmits the robot walking data for given walking parameters such as stride, walking period, etc. The main controller implemented with a TMS320LF2407A controls 21 RC servo motors via the auxiliary controller. We also perform some experiments for balancing motion and walking on a slope terrain with interfacing a 2-axis acceleration sensor and a TMS320LF2407A.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.77-77
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• 2017

현재 국내의 경우 4륜 승용관리기가 개발되었으나 성능 미비와 편이성 부족으로 승용관리기 및 부속 작업기 보급이 매우 저조한 상태이다. 3륜 승용관리기는 작업기 복부 장착으로 작업의 정밀도, 편이성, 관측의 용이성 향상과 함께 지상고 제고, 차폭 조절, 조향 등의 성능 개선을 기할 수 있다. 국내에서는 3륜 승용관리기용 복부 장착 부속작업기가 거의 개발되어 있지 않으며, 특히 두류 재배에 있어서 일관기계화 작업을 위한 관리작업기의 개발은 매우 필요한 실정이다. 승용관리기에 의한 중경제초는 잡초방제는 물론 물 빠짐과 토양 속 통기가 좋아지고, 지온 조절, 쓰러짐 방지, 부정근 발생을 조장하여 콩의 생육과 결실을 좋게 함으로써 수량이 증가되는 효과가 있다. 따라서 본 연구는 3륜 승용관리기에 적합한 복부장착형의 중경제초기를 설계 제작하였다. 3륜 승용관리기용 중경제초기는 승용관리기의 복부 PTO에서의 구동력 전달을 위한 연결 조인트, 중간축, 기어 및 체인 전동기구, 구동축으로 구성된 동력전달부, 중경제초를 위한 5개의 로타리 날과 후방 1개의 제초날로 구성된 3조의 작업날, 경심 조절을 위한 바퀴, 다양한 조간거리에 적응을 위한 조간조정 나사부, 흙의 비산 방지를 위한 로타리 날 커버 및 케이스, 3륜 승용관리기에의 부착을 위한 프레임 및 부착보조 작업기 이동용 바퀴장치 등으로 구성 설계 제작하였다. 로타리 날은 기존 시판 관리기용 로타리 중경 날을 사용하였는데 진행방향에 역으로 회전하도록 하였고, 날의 회전반경은 약 330 mm, 조당 경운 폭은 약 250 mm, 최대 경심 100 mm로 설계하였다. 조간거리의 조절범위는 수동나사에 의하여 620~900 mm 범위로 무단조절 할 수 있도록 하였다. 중경제초기는 3륜 승용 관리기 복부의 평행링크에 부착되므로 작업기의 이동 및 부착 편이성을 위하여 이동용 바퀴를 설치하였다. 제작된 중경제초기의 크기는 길이${\times}$폭${\times}$높이가 $660{\times}2072{\times}880mm$, 중량은 약 200 kg으로 제작되었다.