• 제목/요약/키워드: Ball-screw System

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Flip 모션을 이용한 신개념 필드 로봇 플랫폼의 큰 장애물 등반 정적 해석 및 실험 (Static Analysis and Experimentation on Obstacle-overcoming for a Novel Field Robotic Platform using Flip Motion)

  • 서병훈;신명석;정경민;서태원
    • 제어로봇시스템학회논문지
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    • 제20권10호
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    • pp.1067-1072
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    • 2014
  • The ability to overcome obstacles is necessary for field robots for various applications including the ability to climb stairs. While much research has been performed focusing on overcoming obstacles, the resulting robots do not have sufficient ability to overcome obstacles such as stairs. In this research, the purpose is to overcome relatively large obstacles by flipping locomotion through the modification of the stair climbing robotic platform of the previous research. We propose two scenarios to overcome large obstacles: a rear wheel driving system and an elevation system using a ball screw. The research is performed based on static analyses on obstacle-climbing. As the simulation results indicate, we determined the optimal posture of the robot for climbing obstacles for rear wheel driving. Also, an elevation system is analyzed for obstacle climbing. Between the two scenarios an elevation system is determined to reduce the operating torque of the actuator, and the prototype was recently assembled. The climbing ability of the robotic platform is verified. We expect the application area for this robotic platform will be in accident areas of nuclear power plants.

일체형원자로 제어봉구동장치의 낙하 및 완충특성 (Drop and Damping Characteristics of the CEDM for the Integral Reactor)

  • 최명환;김지호;허형;유제용
    • 한국소음진동공학회논문집
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    • 제20권7호
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    • pp.658-664
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    • 2010
  • A control element drive mechanism(CEDM) is a reactor regulating system, which inserts, withdraws or maintains a control rod containing a neutron absorbing material within a reactor core to control the reactivity of the core. The ball-screw type CEDM for the integral reactor has a spring-damper system to reduce the impact force due to the scram of the CEDM. This paper describes the experimental results to obtain the drop and damping characteristics of the CEDM. The drop tests are performed by using a drop test rig and a facility. A drop time and a displacement after an impact are measured using a LVDT. The influences of the rod weight, the drop height and the flow area of hydraulic damper on the drop and damping behavior are also estimated on the basis of test results. The drop time of the control element is within 4.5s to meet the design requirement, and the maximum displacement is measured as 15.6 mm. It is also found that the damping system using a spring-hydraulic damper plays a good damper role in the CEDM.

레이저보조가공에서 레이저 렌즈 교환장치의 정밀도 평가에 관한 연구 (Study on Accuracy Evaluation of Laser Lens Changer for a Laser-Assisted Machining System)

  • 오원정;김은중;이춘만
    • 한국정밀공학회지
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    • 제32권8호
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    • pp.687-692
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    • 2015
  • LAM (Laser-Assisted Machining) is an effective method for processing difficult-to-cut workpieces. The focal length of a LAM system is changed by the change of the workpiece shape during laser preheating; this problem is solved by changing the lens of the laser module. Linear- and rotary-type lens changers were developed to change the laser lens of a LAM system. The linear-type lens changer is operated by a motor with a ball-screw, and the rotary type is operated by a stepping motor. The natural frequency and structural stability of the laser lens changers were confirmed by using a finite element analysis; in addition, the functions of the lens changers were verified by measuring the iterative accuracy. The measured results show that the rotary-type lens changer is more accurate than the linear-type changer.

Pre-Sliding Friction Control Using the Sliding Mode Controller with Hysteresis Friction Compensator

  • Choi, Jeong Ju;Kim, Jong Shik;Han, Seong Ik
    • Journal of Mechanical Science and Technology
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    • 제18권10호
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    • pp.1755-1762
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    • 2004
  • Friction phenomenon can be described as two parts, which are the pre-sliding and sliding regions. In the motion of the sliding region, the friction force depends on the velocity of the system and consists of the Coulomb, stick-slip, Streibeck effect and viscous frictions. The friction force in the pre-sliding region, which occurs before the breakaway, depends on the position of the system. In the case of the motion of the friction in the sliding region, the LuGre model describes well the friction phenomenon and is used widely to identify the friction model, but the motion of the friction in the pre-sliding such as hysteresis phenomenon cannot be expressed well. In this paper, a modified friction model for the motion of the friction in the pre-sliding region is suggested which can consider the hysteresis phenomenon as the Preisach model. In order to show the effectiveness of the proposed friction model, the sliding mode controller (SMC) with hysteresis friction compensator is synthesized for a ball-screw servo system.

600 mm 급 다기능 광폭 센터리스 연삭시스템 개발 (Development of Multi-functional Centerless Grinding System with 600 mm Wide Grinding Wheels)

  • 오정수;조창래;쯔끼시마 히데히로;조순주;박천홍;오정석;황인범;이원재;김석일
    • 한국정밀공학회지
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    • 제30권11호
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    • pp.1129-1137
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    • 2013
  • We report a centerless grinding machine which can perform multi-function with 600 mm wide grinding wheels. By increasing manufacturing area, long workpiece such as camshaft and steering shaft, is allowed to grind more quickly, compared with cylindrical grinding system. In this paper, the design of centerless grinding machine puts emphasis on symmetry to exploit the thermal stability. Results of finite element analysis shows that the difference of the structural deflection in the front and rear guideways is less than $1.5{\mu}m$ due to symmetric design. The difference is less than $3.0{\mu}m$, even though the thermal deformation is considered. According to the performance evaluation, the radial error motion of the G/W spindle, which is measured by applying Donaldson Ball Reversal, is about 1.1${\mu}m$. The yaw error of the G/W slide is improved from 2.1 arcsec to 0.5 arcsec by readjusting the slide preload and ball screw.

Stability of the prosthetic screws of three types of craniofacial prostheses retention systems

  • Lanata-Flores, Antonio Gabriel;Sigua-Rodriguez, Eder Alberto;Goulart, Douglas Rangel;Bomfim-Azevedo, Veber Luiz;Olate, Sergio;de Albergaria-Barbosa, Jose Ricardo
    • Journal of the Korean Association of Oral and Maxillofacial Surgeons
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    • 제42권6호
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    • pp.352-357
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    • 2016
  • Objectives: This study aimed to evaluate the stability of prosthetic screws from three types of craniofacial prostheses retention systems (bar-clip, ball/O-ring, and magnet) when submitted to mechanical cycling. Materials and Methods: Twelve models of acrylic resin were used with implants placed 20 mm from each other and separated into three groups: (1) bar-clip (Sistema INP, São Paulo, Brazil), (2) ball/O-ring (Sistema INP), and (3) magnet (Metalmag, São Paulo, Brazil), with four samples in each group. Each sample underwent a mechanical cycling removal and insertion test (f=0.5 Hz) to determine the torque and the detorque values of the retention screws. A servo-hydraulic MTS machine (810-Flextest 40; MTS Systems, Eden Prairie, MN, USA) was used to perform the cycling with 2.5 mm and a displacement of 10 mm/s. The screws of the retention systems received an initial torque of 30 Ncm and the torque values required for loosening the screw values were obtained in three cycles (1,080, 2,160, and 3,240). The screws were retorqued to 30 Ncm before each new cycle. Results: The sample was composed of 24 screws grouped as follows: bar-clip (n=8), ball/O-ring (n=8), and magnet (n=8). There were significant differences between the groups, with greater detorque values observed in the ball/O-ring group when compared to the bar-clip and magnet groups for the first cycle. However, the detorque value was greater in the bar-clip group for the second cycle. Conclusion: The results of this study indicate that all prosthetic screws will loosen slightly after an initial tightening torque, also the bar-clip retention system demonstrated greater loosening of the screws when compared with ball/O-ring and magnet retention systems.

회전축을 따라 이동하는 강체의 동해석 (Dynamic Analysis of a Rigid Body Traveling on the Rotating Shaft)

  • 박용석;홍성철
    • 한국산학기술학회논문지
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    • 제11권2호
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    • pp.435-442
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    • 2010
  • 이동하중을 받는 구조물의 동적 거동은 이동물체의 속도에 따라 정하중을 받을때 보다 큰 처짐을 나타내게 되어 구조물의 설계에 중요한 영향을 미치게 된다. 기계가공이나 볼스크류우를 이용한 위치제어분야에서 개선 및 성능 유지를 위한 해석의 기법이 요구되고 있다. 회전하는 티모센코축을 따라 이동하는 두 개의 이동하중을 받는 시스템에 대한 운동방정식이 Hamilton의 원리로 유도되었다. 무차원화된 속도비, 질량비, Rayleigh 계수비의 영향이 시스템의 응답에 미치는 영향을 해석하였다.

전기 구동 이동형 인공호흡기의 개선 및 평가 (Improvement and Evaluation of Portable Electrical Ventilator)

  • 고성호;최낙빈;김대웅;이상훈;오용석;이계한;이성희;이태수
    • 대한의용생체공학회:학술대회논문집
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    • 대한의용생체공학회 1998년도 추계학술대회
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    • pp.149-150
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    • 1998
  • We have developed electrically driven portable ventilator and evaluated through in-vitro and in-vivo test. Ventilator is consists of DC servo motor(Kollmorgen), piston and ball screw, sensing system, power system with backup battery and micro controller. For the precise and stable volume control, the dynamic brake and the PI speed control loop is employed. The main functions are as followers; control, control+sigh, control/assist, control/assist+sigh and SIMV. The animal experiment showed stable performance when it is operated in control mode.

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Experimental studies on the axisymmetric sphere-wall interaction in Newtonian and non-Newtonian fluids

  • Lee, Sang-Wang;Sohn, Sun-Mo;Ryu, Seung-Hee;Kim, Chongyoup;Song, Ki-Won
    • Korea-Australia Rheology Journal
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    • 제13권3호
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    • pp.141-148
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    • 2001
  • In this research, experimental studies leave been performed on the hydrodynamic interaction between a spherical particle and a plane wall by measuring the force between the particle and wall. To approach the system as a resistance problem, a servo-driving system was set-up by assembling a microstepping motor, a ball screw and a linear motion guide for the particle motion. Glycerin and dilute solution of polyacrylamide in glycerin were used as Newtonian and non-Newtonian fluids, respectively. The polymer solution behaves like a Boger fluid when the concentration is 1,000 ppm or less. The experimental results were compared with the asymptotic solution of Stokes equation. The result shows that fluid inertia plays all important role in the particle-wall interaction in Newtonian fluid. This implies that the motion of two particles in suspension is not reversible even in Newtonian fluid. In non-Newtonian fluid, normal stress difference and viscoelasticity play important roles as expected. In the dilute solution weak shear thinning and the migration of polymer molecules in the inhomogeneous flow field also affect the physic of the problem.

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강인한 마찰 상태 관측기와 순환형 퍼지신경망 관측기를 이용한 비선형 마찰제어 (Nonlinear Friction Control Using the Robust Friction State Observer and Recurrent Fuzzy Neural Network Estimator)

  • 한성익
    • 한국공작기계학회논문집
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    • 제18권1호
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    • pp.90-102
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    • 2009
  • In this paper, a tracking control problem for a mechanical servo system with nonlinear dynamic friction is treated. The nonlinear friction model contains directly immeasurable friction state and the uncertainty caused by incomplete modeling and variations of its parameter. In order to provide the efficient solution to these control problems, we propose a hybrid control scheme, which consists of a robust friction state observer, a RFNN estimator and an approximation error estimator with sliding mode control. A sliding mode controller and a robust friction state observer is firstly designed to estimate the unknown infernal state of the LuGre friction model. Next, a RFNN estimator is introduced to approximate the unknown lumped friction uncertainty. Finally, an adaptive approximation error estimator is designed to compensate the approximation error of the RFNN estimator. Some simulations and experiments on the mechanical servo system composed of ball-screw and DC servo motor are presented. Results demonstrate the remarkable performance of the proposed control scheme.