• Journal of the Korean Society for Precision Engineering
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• v.23 no.1 s.178
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• pp.145-151
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• 2006

Wheel bearing unit has been exclusively applied to car wheel supporting device. The seal for wheel bearing is required to have both high sealing effects and low reaction forces because wheel bearing are operated on adverse environmental conditions such as mud and splash water. High sealing effects are for the protection of bearing ball wear from dust influx. In order to ensure high sealing effects, it is a easiest way to increase contact force which are affected by geometric characteristics, material properties and interferences between seal and inner bearing but induces higher wear phenomena. Interferences in all variables are most important factor to determine the performance of wheel bearing. In this study, optimization of interference amount was performed with finite element analysis with commercial code ABAQUS. For the sake of finite element analysis, tensile tests of rubber material were conducted and governing equation of nonlinear behavior was achieved. Hock-up bearing was manufactured with optimized interference amount. Results of torque and mud spray tests using this bearing unit are performed. Less torque and moisture influx of bearing with optimized interference amount is evidence to validity of this study.

• Tribology and Lubricants
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• v.7 no.1
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• pp.35-39
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• 1991

The performance of the ultra-precision machine tools depends on the steady state characteristics of the main spindle bearings. For excluding the effect of machining error with perpendicularity, conical or spherical bearing has been used. In this paper, steady analysis of the externally pressurized conical gas bearing for ultraprecision is carried out based on the direct numerical method with assumption of point source. As a result of theoretical analysis, design parameters for optimal condition of conical gas bearing are' presented in dimensionless form.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.04a
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• pp.336-340
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• 1996

This paper presents the development of a collocated capacitance sensor and its application to the decentralized PID controller design for 4-axis magnetic bearing system. The main feature of the sensor is that it is made of a compact printed circuit board (PCB) so that it can be built in to the actuator coil of the magnetic bearing unit. The signal processing unit has been also developed. Then, decentralized PED controller is designed using simplified rotor system model. Finally, the experimental results on the performance of the collocated sensor based decentralized PID controller for a magnetic bearing rotor system is presented.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.355-358
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• 2003

This paper presents characteristics of vacuum preloaded porous air bearing. Pressure distribution of a porous pad and vacuum pocket are calculated. And load capacity and stiffness of the bearing are analyzed with various vacuum parameters, that is. clearance height. tube diameter, tube length. pumping speed of vacuum pump, vacuum pocket to porous pad area ratio. From the simulation results, optimum clearance for best performance can be selected adjusting these parameters, especially tube diameter which is the most dominant source.

• 제어로봇시스템학회:학술대회논문집
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• 1992.10a
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• pp.558-563
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• 1992

Bearing information of target is used critically for target tracking in underwater environment. In passive sonar, target bearing measurements are obtained by processing the acoustic signal emanating from the target. PDA tracking algorithm is usually applied in this case since bearing measurements have several peaks due to interference with other acoustic sources or reflections from underwater media. In this paper, we propose a modified PDA algorithm adopting new probabilistic distributions of the number, position, and amplitude of peaks based on the analysis of real data. This algorithm is tested on real and artificially generated data. The computer simulation result shows improvement of the tracking performance.

• Tribology and Lubricants
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• v.27 no.2
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• pp.77-87
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• 2011

In this study, using the governing equation for thermohydrodyamic lubrication involving the homogeneous mixture of incompressible fluid derived by based on the principle of continuum mechanics, it is discussed the effects of water within turbine oil on the performance of high speed journal bearing of a steam turbine shipping engine. The governing equation is the general equation being able to be applied on the mixture of Newtonian fluid and non-Newtonian fluid. Here, the fluid viscosity index, n of power-law non-Newtonian fluid is supposed to be 1 for the application of the journal bearing in a steam turbine shipping engine lubricated with the mixture of two Newtonian fluid, for example, water within turbine oil. The results related with the bearing performance are showed.

• KSTLE International Journal
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• v.10 no.1_2
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• pp.6-12
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• 2009

In this study, the effect of oil supply conditions on the dynamic performance of a hydrodynamic journal bearing is analyzed numerically. Axial length, circumferential length and location of oil grooves are considered as oil supply conditions. The perturbation equations of the perturbed film contents are obtained by applying Elrod's universal equation implementing JFO film rupture / reformation boundary conditions to Lund's infinitesimal perturbation method. The dynamic coefficients of a hydrodynamic journal bearing are calculated by solving the perturbation equations, and the linear stability analysis is carried out by using those for a variety of oil supply conditions.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2003.11a
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• pp.267-272
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• 2003

This paper presents a performance analysis model of corrugated bump foil bearings. The analyses for not only 1st generation bump foil journal bearings but also bump foil thrust bearings are performed. Static performances such as load capacity, attitude angle, pressure distribution, foil deflection, and film thickness are accurately estimated by using soft elasto-hydrodynamic analysis technique and finite difference numerical method. Also dynamic performances such as stiffness coefficients and damping coefficients are estimated by perturbation method. The analysis technique may be appliable to rotordynamic analysis, stability analysis, and optimized bearing design.

• Journal of KSNVE
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• v.5 no.1
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• pp.59-65
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• 1995

In this study, we investigated the operational limit of magnetic bearing-rotor system due to the maximum force limit and slew rjate limit of the electromagnetic actuator as a function of the time dependent control characteristics. The feedback gain of the controller varies the current of the electromagnet coil with the motion of the rotor. The distorsion of magnetic force due to the slew rate limit is not occurred jup to 30, 000 rpm in the magnetic bearing that we have a close relation with the rotational speed and vibration level of the rotor and the proportional gain of the controller. Therefore the maximum force limit determines the maximum allowable orbit radius of the magnetic bearing-rotor system. The maximum allowable vibration levels are exponentially decreased according to the increment of rotational speed and proportional gain of the controller.

• Journal of Institute of Control, Robotics and Systems
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• v.22 no.10
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• pp.788-796
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• 2016

Bearing and frequency measurements of TMA (Target Motion Analysis) in passive line array SONAR have lower bearing rate and frequency doppler, and are not detected or tracked continuously because of various ocean environments. This is a main reason to effect the TMA performance and it takes a long time to get TMA solutions. We propose the bearing and frequency TMA(BFTMA) using accumulative batch estimation to solve the TMA problem of line array passive SONAR. The accumulative batch estimation structure is based on MLE (Maximum Likelihood Estimation) but used accumulative measurements. The accumulative batch estimation is applied for the BFTMA with nonlinear Kalman filter to estimate the target range, speed and course. Simulation and sea data analysis were carried out to verify the performance and applicability of the proposed techniques.