• Title/Summary/Keyword: Speed Improvement

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Improvement and Estimation of Effect for Speed Limit Tolerance (속도위반 단속 허용범위 개선안 제시 및 효과 추정)

  • Su-hwan Jeong;Kyeung-hee Han;Min-ho Lee;Choul-ki Lee
    • The Journal of The Korea Institute of Intelligent Transport Systems
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    • v.22 no.2
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    • pp.164-181
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    • 2023
  • In a low speed limit environment, the speed limit tolerance of automated traffic enforcement devices is very high, which is one of the main factors for the low compliance rate. Therefore, in this study, we aimed to the improve the speed limit tolerance and to present a new standard. The effects of the operator and user errors that can cause speeding by drivers were analyzed. Based on the results of the analysis, an improvement of the tolerance was proposed by applying an error in the enforcement device and GPS speed. In addition, long-term expected safety effects such as the accident rate and severity were estimated from the operator's perspective when improving the tolerance. As a result of the estimation, the speed limit compliance rate, accident rate, and change rate of a number of severe accidents due to speed change, and pedestrian traffic accident mortality rate were all improved in all speed limit environments. The introduction of the proposed improvement is expected to improve road safety significantly.

A study on the improvement of PLL system for three phase induction motor speed control (삼상유도전동기의 속도제어를 위한 PLL System의 개선에 관한 연구)

  • 정연택;이성용
    • 전기의세계
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    • v.30 no.12
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    • pp.832-837
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    • 1981
  • The study of PLL System to control the Speed of three phase induction motor is described. By solving some problems of conventional PLL system, the system has ability to be easily locked under any conditions. In order to study response velocity and stability of system, this paper presents different filter types and methods of determination of time constant.

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Study for Application of High Speed R-bar System in Metro Express Railway Tunnel (광역급행철도 터널에 고속 R-bar 적용에 관한 연구)

  • Ahn, Young-Hoon;Song, Jin-Ho;Kim, Si-Gu
    • Proceedings of the KSR Conference
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    • 2011.05a
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    • pp.409-412
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    • 2011
  • Maximum speed of the train could not exceed over 160km/h with R-bar system in the underground type tunnel structure. By the research to overcome this speed limit, maximum speed has reached up to 200~250km/h recently by new R-bar system. It is under discussion to construct Metro Express Line between Gyonggido and Seoul which requires maximum speed 180km/h~230km/h. New R-bar is an optimal system to achieve the speed improvement in this line. This study shows application of the high speed R-bar system in the underground tunnel section.

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Development of High Speed Machining Technology (고속절삭가공기술개발)

  • 이춘만;최치혁;정원지;정종윤;고태조;김태형
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 2002.04a
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    • pp.266-272
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    • 2002
  • High-speed machining is one of the most effective technology to improve productivity. Because of the high speed and hugh fried rate, high-speed machining can alive great advantages for the machining of dies and molds. This paper describes on the improvement of machining accuracy in high-speed machining. Depth of cut, feed rate and spindle revolution are control factors. The effect of the control factors on machining accuracy is discussed fur the results of surface roughness and machining error in Z-direction of the high speed machining.

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Performance Evaluation on Impeller Related Parameters Change in Centrifugal Pump of very Low Specific Speed (극저비속도 영역에서 임펠러 관련인자 변화에 따른 원심펌프 성능 평가)

  • Choung, Young-Dae;Lee, Kye-Bock
    • The KSFM Journal of Fluid Machinery
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    • v.14 no.1
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    • pp.11-17
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    • 2011
  • The numerical study was conducted to investigate the pump performance due to impeller related parameters change in centrifugal pump of very low specific speed by using CFD code. A small centrifugal pump whose specific speed is $N_s=76.2$ was used, and the performance characteristics were discussed for different number of vanes, rotational speed, and the length and height of vane. The numerical results at a very low specific speed show that the increase of the number of vanes has little effect on improvement of output pressure but results in the reduction of pressure fluctuation, and that the head increases with the increase in the rotational speed. The decreasing the length of vane has a considerable reduction of the capacity coefficient in comparison with decreasing the height of vane.

The Characteristics of High Speed Feed Drive System using High Lean Screw (High Lead Ball Screw를 사용한 고속이송계의 특성)

  • 고해주;박성호;정윤교
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.10 no.4
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    • pp.97-103
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    • 2001
  • The study on the high-speed machine tool is very important for the improvement of productivity since it can shortens cutting and non-cutting time. Especially, high speed of feed drive system is the major research field. In the industries of the advanced countries, the feed drive systems at the speed of 60 m/min have been already developed based on the high lead ball screws. In this study, a high speed feed drive system at the speed of 60 m/ min has been developed, and its movements characteris-tics are investigated. As the movement characteristics, positioning accuracy, angular accuracy, straightness and micro step-response are measured. Thermal characteristics of the system is also discussed. For measuring the movement characteris-tics, a laser interferometer, a memory-based Hi-coder and a cooling device are used. The experimental results confirm that the movement characteristics and the thermal behavior of the system are satisfactory in the aspect of accuracy and stability.

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Shift Speed Improvement of a Metal Belt CVT

  • Lee, Heera;Kim, Hyunsoo
    • Journal of Mechanical Science and Technology
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    • v.15 no.12
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    • pp.1623-1629
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    • 2001
  • This parer presents a CVT line pressure control strategy for the increased shift speed. Firstly, an algorithm to increase the CVT shift speed is suggested based on a modified CVT shift dynamics and shift speed maps are constructed. In addition, simplified dynamic models of the line pressure and the ratio control valve are derived by considering the CVT shift dynamics, and low level control algorithms for the ratio and the line pressure control are proposed. Using the shift speed maps and the simplified dynamic models of the CVT system, shift performance is investigated. It is found from the experimental and simulation results that improved shift speed can be achieved by increasing the lilly pressure.

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Optimization of Spindle Units Considering the Decrease of Bearing Stiffness at High Speed Revolution (고속 회전시 베어링 강성강하를 고려한 주축 유니트의 최적화)

  • Lee, Chan-Hong
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.19 no.6
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    • pp.717-723
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    • 2010
  • Radial stiffness of angular contact ball bearings are decreased remarkably at high speed revolution, because the inner and outer ball contact angle with races arc changed under the ball centrifugal forces at high speed. In the past, the optimizations of spindle units were done under the assumption of unchanged bearing stiffness for the whole speed range. But the bearing stiffness is changed and the dimension of optimum spindle is also changed with speed. In the design phase, only one model of many optimum spindle models with speed should be selected. As optimization criterion, the area of transfer function at spindle nose is proposed to estimate simply and accurately improvement of dynamic characteristics in spindle units. Finally, according to many analyses of diverse spindle models with decreased bearing stiffness, the spindle with shorter bearing span is better than longer bearing span from the viewpoint of dynamic characteristics.

Evaluation of Combustion Stability of Idling Speed State (LBT연소를 통한 Idling 운전시의 연소안정성 평가)

  • 이중순;이종승;김진영;정성식;하종률
    • Transactions of the Korean Society of Automotive Engineers
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    • v.7 no.5
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    • pp.66-72
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    • 1999
  • It is necessary to discuss lightening engine parts and reducing the friction of sliding parts to improve fuel consumption and combustion stability at idling condition. Lean best torque combustion which produce maximum power at a lean air-fuel ratio is effective for the reduction of exhaust gas emission and the improvement of fuel consumption. Accordingly, this study deals with the expansion of lean combustible limitation, the combustion stability and the reduction of idle speed through the analysis of combustion characteristics on the base of the control technique of precise air-fuel ratio because it does not need to maximum power at idling condition. The idle speed is increased proportional to ISC(Idle Speed Control) duty ratio. On the other hand the idle speed decreased by lean air-fuel ratio. The COV in engine speed is stable within maximum two percent up to 17.6 mixture ratio by the control of ISC duty ratio.

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Performance Improvement of BLDC Motor Speed Control Using Hybrid PWM Method (하이브리드 PWM 방식을 이용한 브러시리스 직류 전동기의 속도 제어 성능 향상)

  • 이동훈;오태석;전성구;김일환;남부희
    • The Transactions of the Korean Institute of Electrical Engineers D
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    • v.53 no.7
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    • pp.491-500
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    • 2004
  • This paper considers a hybrid PWM(pulse width modulation) method which can be used in the brushless DC motor controller. Due to many disadvantages of bipolar PWM method, unipolar PWM method is mostly used in industrial field. In constant speed control application, the unipolar PWM method shows the good performance of speed control. But in the wide range of speed control application, it shows poor performance especially when deceleration is needed. So we propose the hybrid PWM method that utilizes both of bipolar and unipolar PWM methods according to the sign of the speed controller output. Simulation and experimental result show that the proposed method improves speed control performance of the brushless DC motor which is applied to the industrial sewing machines.