• 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.

• 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.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.276-279
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• 2005

This paper presents a novel cylindrical capacitive sensor (CCS) for both radial and axial motion measurements. Although the new CCS has almost the same geometric configuration as the conventional CCS, the unused axial area of the CCS is utilized to measure the axial motion of the rotor, which can affords more compact design and reduction of the system complexity. First, a theoretical model of the proposed CCS is derived. Based on the derived theoretical model, compensation methods to decouple the radial and axial motion measurements are proposed. In addition, error analysis is performed and a design rule is proposed to guarantee the same accuracy in measuring both radial and axial motions. Finally, a test rig and electronics for the proposed CCS are built and the effectiveness of the proposed CCS is verified with experiments and simulations.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.613-618
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• 2004

CCS was developed and applied to rotating machines because of accurately measuring the spindle error motion without significant efforts. However, researches on the CCS have been focused on ideal cases where circumferential gaps were ignored. This paper presents the effects of circumferential gaps and proposes an optimal CCS considering the circumferential gaps. First, electrostatic analysis of the CCS that includes the circumferential gaps is performed using the FEM, and an additional capacitance due to the circumferential gap can be approximated as an equivalent extended sensor length. Second, a mathematical model of the CCS considering the circumferential gaps is derived, and the optimal CCS is determined through minimization of the weighted error amplification factor. Finally, two CCSs, both considering and ignoring the circumferential gaps, are built, and the effectiveness of the optimal design is verified through simulation and experiment.

• 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.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.11a
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• pp.230-236
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• 2001

We developed a built-in sensor bearing to measure the rotor motion of a rolling piston type compressor for the air conditioner. Because of needs for the high efficiency and long life span of compressor, and the usage of alternative refrigerants, the operating condition of the compressor becomes more severe. The accurate measurement of the rotor motion of the compressor can contribute greatly to the design and analysis of the hydrodynamic bearing. However, it is difficult to measure accurately the shaft behavior of small compressor because of the small space for the sensor mount, high temperature and pressure of compressor, oil mixed with refrigerant, and electromagnetic noise of the motor. To overcome these difficulties, we develop the cylindrical capacitive sensor that is built in the hydrodynamic bearing and calibrate the built-in sensor bearing indirectly through measuring the oil relative permittivity. We measured the rotor motion as well as suction and discharge pressures in various conditions. The several experimental results show that the developed built-in sensor bearing can measure the rotor motion not only in steady state but also in transient state.