• Title/Summary/Keyword: Ball speed

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Development of Indoor Locomotion Assistive Robot, Ball-Chair, for the Elderly (고령자를 위한 실내 이동 보조 로봇 볼체어의 개발)

  • Kim, Woo-Yong;Kim, Jung-Yup
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.38 no.7
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    • pp.799-807
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    • 2014
  • This paper describes the development of an indoor locomotion assistive robot, Ball-Chair, comprising a novel drive system. This robot facilitates locomotion assistive operation in narrow spaces, in which common wheelchairs cannot move easily. The Ball-Chair has two main features: its structural feature and driving mechanism. The exoskeleton frames of the Ball-Chair have been designed with octagonal shapes resembling a circle, for minimizing its volume and weight. Additionally, all its driving parts (including the ball) are mounted within of the robot to enhance its safety. The Ball-Chair features a reverse ball-mouse driving mechanism comprising two driving omni-wheels in the x- and y-axes. By controlling the speed of each omni-wheel, a holonomic driving system that can facilitate omnidirectional locomotion has been achieved using only two wheels. The effective movement of the Ball-Chair in any direction within narrow indoor spaces was experimentally verified. The paper outlines the development procedure in detail.

A Study on the characteristics of the High Speed Machining for several Tool Materials change of Ellipse Mirror Machining to be used in Millimeter Wave Interferometer System (밀리미터파 간섭계용 타원 반사경의 공구 변화에 따른 고속절삭 특성 연구)

  • Lee, Sang-Yong;Kim, Geon-Hee;Kim, Hyo-Sik;Yang, Soon-Cheol;Hong, Chang-Deoc;Cho, Byung-Moo;Won, Jong-Ho
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.6 no.4
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    • pp.22-27
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    • 2007
  • This study aims to find the optimal cutting conditions, when ellipse mirrors consisted Aluminum alloy were made it the Millimeter-Wave Interferometer System mirror with several tools on the High-Speed Machine. Machining technique for precision machining characteristics of ellipse mirrors consisted Al6061 matter by Ball endmill is reported in this paper., Results of machining on the High-Speed Machine(using NCD(Natural Crystalline diamond), WC and coated TiAlN ${\phi}6mm$ ball endmill tool) had measurement of surface roughness and form accuracy with cutting conditions(the Feed rate, the Depth of cut and the Cutting speed). the Millimeter-Wave Interferometer System ellipse mirror had been machined foundational precision machining characteristics of aluminum.

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Thermal Characteristics of the High Frequency Motor Spindle according to the Bearing Preloads and Cooling Conditions (예압과 냉각조건에 따른 고주파 모터 내장형 주축계의 열특성)

  • Choi D. B.;Kim S. T.;Jung S. H.;Kim J. H.;Kim Y. K.
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 2005.05a
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    • pp.138-143
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    • 2005
  • The important problem in the high speed spindles is to reduce and minimize the thermal effect by the motor and ball bearings. Thermal characteristics according to the bearing preload and hollow shaft cooling are studied for the spindle with the oil mist lubrication and high frequency motor. Temperature distribution and thermal deformation according to the spindle speed, preload and flow rate are measured by thermocouple and gap sensor. Temperature distribution and thermal deformation are analyzed by using the finite element method. The results of analysis are compared with the measured data. This paper show that the suitable preload and hollow shaft cooling are very effective to minimize the thermal effect by the motor and ball bearings. This study indicates that temperature distribution and thermal deformation of the high speed spindle system can be estimated reasonably by using the three dimensional model through the finite element method and supports thermal optimization and more effective cooling method.

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A Study on the Tribological Characteristics of PTFE Composites-filled with Nano CuO Particles Under a Slow Sliding Speed and Low Load Condition (나노 CuO입자로 충진된 PTFE 나노복합소재의 저속 및 하중 조건에서의 트라이볼로지 특성에 관한 연구)

  • Minhaeng Cho;Junghwan Kim
    • Tribology and Lubricants
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    • v.39 no.3
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    • pp.111-117
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    • 2023
  • This paper presents an experimental investigation of the tribological characteristics of PTFE composites filled with nano CuO particles under low sliding speed and load. All the specimens were prepared by sintering. Before sintering, the mixture of PTFE powder and CuO particles were mixed by a high-speed mixer using CuO volume fractions of 0.2 vol. % and 5 vol. %. Each mixture was sintered at 350 ℃ for 30 min on the steel disk. We conducted ball-on-disk sliding test an hour using a steel ball against PTFE composites, including pure PTFE. The load and sliding speed used was 2 N and 0.01 m/s, respectively. Adding nano CuO particles increases the friction coefficient because of the abrasiveness of hard nano CuO particles. The highest coefficient of frictions was obtained from 5 vol. % CuO. Conversely, the lowest wear of the composites was obtained from the 5 vol. % CuO nanocomposite. This study reveals that the addition of nano CuO particles can lower the wear of PTFE, despite an increase in the coefficient of friction. However, the coefficient friction is still moderate compared to other engineering polymers. In addition, the amount of CuO nano particles has to be optimized to reduce friction and wear at the same time.

Prediction of the Fatigue Life of Deep Groove Ball Bearing Under Radial and Moment Loads - Fatigue Life Tests and Proposal of the Life Adjustment Factors (반경방향과 모멘트하중 하에서의 깊은홈 베어링의 피로수명평가 - 수명시험 및 수명보정계수 제안)

  • 김완두;한동철
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.12
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    • pp.3149-3158
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    • 1994
  • In this paper, using the formulation of dynamic equivalent load considering the effects of moment load and the equation to estimate the cage rotational speed, the new life equation of deep groove ball bearing under radial and moment loads was proposed. Fatigue life test apparatus with the measuring equipment of shaft and cage speed was designed and developed to be capable of subjecting combined radial and moment load. Fatigue life tests were executed by sudden death test method and the reliability of fatigue lives was evaluated by Weibull distribution analysis. From the results of fatigue tests and analysis, the relationships between film parameters and life adjustment factors were acquired. And it was turned out that so as to estimate the effect of moment load on fatigue life, the life adjustment factor as well as the dynamic equivalent load must be taken into account.

A Study on the Silicone Rubber of Sabot Assembly for the Velocity Multiplication of Mini Ball (소형구의 속도증폭을 위한 사보 조립체의 실리콘고무 특성 연구)

  • Kim, Young-Min;Jin, Doo-Han;Chung, Dong-Teak
    • Journal of the Korea Institute of Military Science and Technology
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    • v.18 no.4
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    • pp.395-401
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    • 2015
  • A mini ball launch system was developed for the study of dynamic fracture of ceramic materials. The principle of velocity multiplication system is similar to two stage gun. The plastic sabot assembly houses steel plunger and the void filled with silicone rubber. The sabot is stopped by the stopper block then the steel plunger inside the sabot compress the silicone rubber to high pressure. Then the compressive energy of the silicone rubber is transferred to the ball. More than ten times of initial speed was attained. In this study, most effective silicone rubber for the highest final speed was chosen out of three different varieties by launch tests.

The role of nanotechnology in reducing the impact on the ball and increasing the speed of its movement

  • Yongyong Wang;Qixia Jia;Tingting Deng
    • Geomechanics and Engineering
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    • v.32 no.5
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    • pp.463-474
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    • 2023
  • Materials produced with the help of new technology are used in the design of materials used in all science and engineering departments today. A sports engineering and sports equipment department is one of these departments. The use of nanotechnology in sports equipment is one of the most popular uses of this technology today. Nanomaterials have been used in sports equipment for many years, and reputable companies have benefited. Athletes' equipment allows them to display their skills to the fullest extent. It has always been a dream of professional athletes and their coaches to have unique equipment. As a result, engineers have spent all their time and effort solving this problem. Science and engineering can do various things to meet the needs of all sports levels, including specific and detailed designs, the use of appropriate materials, and standardization tests on equipment. However, these aspects must remain aligned with the latest technologies as they develop, just as with other sciences. These technologies, especially nanotechnology, are essential to sports equipment and devices developed today by sports engineers. This article examines the balls that use nanotechnology and can also improve the athlete's performance by using this technology in a specific structure. Using nanotechnology to make nanocomposite poly-hope balls, which makes them lighter and more acceptable, reduces the impact on the ball and increases its movement speed.

Biomechanical Evaluation of Elbow Moment in Pitching Types according to the Throwing Speed: A Pilot Study

  • Lee, Chang-Hyung;Yang, Jin-Hwan;Lee, Seung-Hoo;Lee, Gyu-Chang;Park, Jong-Chul
    • Korean Journal of Applied Biomechanics
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    • v.30 no.1
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    • pp.1-6
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    • 2020
  • Objective: The incidence rate of elbow ulnar collateral ligament injuries is dependent on the throwing speed or pitching type, especially in adolescent baseball players. However, mixed results have been reported due to a lack of controlled biomechanical analysis. Thus, the purpose of this study was to investigate the biomechanical analysis of the elbow in relation to throwing speed and pitching type. Method: Four overhead type high-school baseball players were recruited for this study. The participants were asked to throw balls with different types of pitch and speed. While the throwing speeds were measured, each pitching moment of the elbow was recorded. Descriptive statistics, frequency analysis, mean comparison analysis, and Pearson's correlation analysis were performed in order to examine differences in peak varus and valgus moment during pitching motion in the elbow in all throwing speed and pitching types. Results: There was no significant difference in physical characteristics, throwing speed, and momentum variability among all players. The mean varus moments were 44.38±1.55 Nm, 48.83±1.66 Nm, and 48.94±0.95 Nm, and the moment gaps between varus and valgus were 7.36±3.25 Nm, 7.44±2.02 Nm, and 7.36±2.62 Nm in fastball, curveball, and slider ball, respectively. The varus moment was higher in the curved and slider balls than in the fastballs, and there was no significant differences between the varus moments regarding the pitching type. However, the increase in valgus moment and decrease in moment gap according to throwing speed was significantly increased in the slider ball (r=0.718 and -0.591, respectively). Conclusion: The possibility of elbow injury caused by the valgus moment or moment gapincreases more rapidly in slider balls as the speed increases. Based on our results, appropriate pitching guidelines should be suggested to prevent ulnarligament injuries, especially in adolescent baseball players.

Frictional Behavior and Film Thickness of Some Liquid Crystals in Elastohydrodynamic Lubrication (탄성 유체 윤활에서의 액정의 마찰 특성 및 유막두께)

  • 이희성
    • Tribology and Lubricants
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    • v.18 no.4
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    • pp.255-259
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    • 2002
  • The tribological properties of eight different liquid crystals were investigated in a concentrated point contact device and a ball-on-flat contact. For comparison, the same tests were also performed with commercial greases and the corresponding base oils. Under the fully flooded conditions studied, liquid crystals in a concentrated point contact showed lower friction than commercial greases and greater film thickness dependence on rolling speed than grease base oils or greases. Test results also showed that the film thickness and friction were little influenced by the composition of the examined liquid crystals.

유한차분법을 이용한 볼스크류 시스템의 열팽창 해석

  • 박정균;정성종
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1991.11a
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    • pp.101-104
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    • 1991
  • Bal1 screw systems has been used for positioning elements of machine tools. In order to maintain high rigidity and accuracy, preload is applied between nut and screw. However, large amount of preload increases frictional heat. Temperature rises remarkably at high speed notion, Thermal expansion degrades positioning accuracy, In this paper, finite differance method is applied to compute temperature distributions and thermal expansions of ball screw systems according to preload condition and rotational steed. Some simulation results show that the developed methodology is good to study thermal expansion of ball screw systems.

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