• Title/Summary/Keyword: Cylindrical capacitive displacement sensor

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Effects of Geometric Errors on the Measurement of Error Motions of Rotor with the Cylindrical Capacitive Displacement Sensor (형상오차가 원통형 정전용량 변위센서의 축 회전오차의 측정에 미치는 영향)

  • 안형준;장인배;한동철
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1995.10a
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    • pp.487-490
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    • 1995
  • This paper discisses the effects geometric errors on the measurement of error motions of rotor with the cylindrical capacitive displacement sensor. Analytic model of the measuring process with this sensor is derived and this model shows that the effect of geometric errors of sensor is larger than that of rator on the measurement of error motions of rotor. The computer simulation shows effect of periodic errors in this sensor on the measuring orbit.

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A Study on the Measurement Characteristics of Cylindrical Type Capacitive Transducers to the Roundness Errors of Rotor for Magnetic Bearing (자기베어링용 로우터의 형상 오차에 대한 실린더형 캐패시턴스 센서의 측정특성에 관한 연구)

  • Lee, S.H.;Jung, S.C.;Han, D.C.
    • Journal of the Korean Society for Precision Engineering
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    • v.12 no.3
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    • pp.23-31
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    • 1995
  • The sending characteristics of the non-contact type displacement transducers can affect the performances of the magnetic bearing systems when they support the rotating shaft. The probe type displacement sensor detects not only the displacement of the rotor at the sensing position but also the surface irregularitis of the rotor such as surface roughnessand roundness errors. If there exist such measuring errors, the magnetic bearing can not apply proper force against the rotor displacements for the detected signal is the input to the magnetic bearing controllers. The cylindrical shape capacitive transducer can detect the rotor displacement by the integral sum of the charges which are formed between the sensor plates and rotor so that it can reduce the detecting errors induced by the surface irregularities of the rotor. By theore- tical analysis, we compared the sensing characteristics of the cylindrical shape capacitive transducers for the rotors that have some sinusoidal irregularities with that of the ideal probe type displacement transducers.

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Automatic and precise calibration of 4-channel cylindrical capacitive displacement sensor (4채널 원통형 정전용량 변위센서의 자동ㆍ정밀 검보정)

  • 김종혁;김일해;박만진;장동영;한동철;백영종
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 2004.04a
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    • pp.387-393
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    • 2004
  • General purpose of cylindrical capacitive displacement sensor(CCS) is measuring run-out motion and deflection of rotor. If CCS has narrow sensing range, its sensitivity coefficients must be calibrated precisely. And x, y component of CCS output can be coupled. In this research, CCS calibration procedure is automated with automatic calibration program and PC-controlled stage. And, coupled-terms of CCS signals were removed and the errors between measured position and mapped CCS signal were reduced obviously by sensitivity matrix that linearly.

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Performance of Built-in Capacitance Type Transducer of a Magnetic Bearing System (캐패시턴스형 센서가 내장된 자기베어링 시스템의 작동성능에 관한 연구)

  • 장인배;한동철
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.19 no.9
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    • pp.2082-2088
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    • 1995
  • In this paper, we designed and fabricated the magnetic bearings and built-in type cylindrical capacitive transducers for improving the vibration characteristics of rotating shaft. The eddy current and magnetic field from the electromagnet of the bearing don't affect the measuring signal of the capacitive type transducers so that it is possible to locate the capacitive sensor plates around the magnetic bearing poles and can improve the spillover problem which is induced by the noncollocation of the sensors and actuators. According to the sensitivity calibration schemes using a X-Y table, the cylindrical capacitive transducers have a good linearities in the .+-.70.mu.m range from the geometric center of the sensor plates. The measured results also show high displacement sensitivities of the sensors. According to the performance test of the magnetic bearing which is controlled by the analog PD controllers, we found that the built-in capacitive transducer system successfully measures the journal displacement in the magnetic field and therefore the magnetic bearing system supports the rotating shaft up to 12,000 rpm.

Chatter Monitoring of Milling Process using Spindle Displacement Signal (주축 변위 신호를 이용한 밀링가공의 채터 감시)

  • Chang, Hun-Keun;Kim, Il-Hae;Jang, Dong-Young
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.16 no.6
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    • pp.140-145
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    • 2007
  • To improve productivity of a metal cutting process, it is required to monitor machining stability in real time. Since cutting environment is harsh against sensing conditions due to vibration, chip, and cutting fluid, etc., it is necessary to develop a robust and reliable sensing system for the practical application. In this work, a chatter monitoring system was developed and its effectiveness was proved. Spindle displacement caused by cutting was selected as a main monitoring parameter. A cylindrical capacitive displacement sensor was adopted. Chatter frequencies were identified through modal analysis. To quantify chatter vibrations, chatter correlation coefficient was introduced. The identification of the monitoring system showed a good agreement with the result of experiment.

New Design of Cylindrical Capacitive Sensor for On-line Precision Control of AMB Spindles (자기베어링의 실시간 정밀제어를 위한 원통형 정전용량 변위센서의 새로운 설계)

  • Jeon, Soo;Ahn, Hyeong-Joon;Han, Dong-Chul
    • Proceedings of the KSME Conference
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    • 2000.11a
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    • pp.548-553
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    • 2000
  • A new design of cylindrical capacitive sensor(CCS) for the displacement measurement of precision active magnetic bearing(AMB) spindle is presented in this paper. This research is motivated by the problem that existing 4-segment CCS is still sensitive to the $3^{rd}$ harmonic component of the geometric errors of a rotor. The procedure of designing new CCS starts from the modeling and error analysis of CCS. The angular size of CCS is set up as a design parameter, and new 8-segment CCS is introduced to possess an arbitrary angular size. The optimum geometry of CCS to minimize the effect of geometric errors is determined through minimum norm approach. Experimental results with test rotors have confirmed the improvement in geometric error suppression.

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On-line Cutting Force Estimation by N[ensuring Spindle Displacement in High-Speed Milling Process (고속 밀링 가공 시 주축 변위 측정을 통한 절삭력의 실시간 감시)

  • Kim J.H.;Kim J.H.;Kim I.H.;Ahn H.J.;Jang D.Y.;Han D.C.
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2006.05a
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    • pp.133-134
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    • 2006
  • A cylindrical capacitive displacement sensor (CCS) was developed and applied for monitoring end milling processes. Dynamic characteristics of a spindle-assembly were measured using the CCS and a designed magnetic exciter. The technique to extract the spindle displacement component caused only by cutting from the measured signals using the CCS was proposed in the paper. Using CCS signals and FRF (Frequency Response Function) derived from dynamics of the spindle tool system, dynamic cutting forces are estimated quantitatively.

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Design of Thermal Displacement Compensation Sensor for High Reliability Machine Tools (고신뢰 머시닝센터를 위한 열변위 보상 센서 설계기술)

  • Kim, Il-Hae;Jang, Dong-Young;Park, Jeong-Hoon;Park, Sung-Wook;Shim, Poong-Soo
    • Journal of the Korean Society for Precision Engineering
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    • v.28 no.8
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    • pp.886-893
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    • 2011
  • To increase the reliability and positional accuracy of a machine tool, a novel capacitive displacement sensor having a cylindrical shape is presented to measure the axial displacement of a machine tool spindle. Characteristics of the sensor were analyzed by numerical simulation. The sensor was built into a specific machine tool spindle and its performance was experimentally investigated. The accuracy of a thermal error compensation system of a machine tool can be enhanced greatly using proposed sensor.

A Study on Cutting Force Measurement Using Cylindrical Capacitance-Type Spindle Displacement Sensor (주축 변위 센서를 이용한 절삭력 측정에 관한 연구)

  • 김일해;박만진;장동영;한동철
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 2001.04a
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    • pp.89-94
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    • 2001
  • A cylindrical capacitance-type spindle displacement sensor was designed and tested in the hard turning as a way to develop a sensor that can estimate cutting forces without using a tool dynamometer. The displacement sensor was installed between the face of spindle cover and the chucking element, and measured pure radial motion of the spindle. Ceramic inserts and tool steel workpieceof 65 Rc were used during the hard turning tests. The signals from the sensor showed the same pattern of cutting force variations as those from the tool dynamometer. The research results showed that the developed sensor could be utilized as an effective and cheap on-line sensing device to estimate cutting forces.

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CUTTING FORCE PREDICTION USING SPINDLE DISPLACEMENT IN MILLING (밀링가공에서의 주축 변위 측정을 통한 절삭력 예측)

  • 장훈근;장동영;한동철
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 2004.10a
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    • pp.485-489
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    • 2004
  • Cutting force is important to understand cutting process in milling. To measure cutting force, tool dynamometer is widely used but it is hard to apply in workshop condition. Cutting force measurement which doesn't affect cutting process is needed. Using relations between cutting force and spindle displacement, cutting force can be predicted. Cylindrical capacitive sensor was used to measure spindle displacement during cutting. And signals from tool dynamometer collected to compare with spindle displacement. The result shows spindle displacement has a linear relation with cutting force. Using this result, a simple method to predict cutting force could be applied at workshop condition.

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