• KSTLE International Journal
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• v.2 no.1
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• pp.22-28
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• 2001

A resin bonded copper-graphite brush was investigated to evaluate the characteristics electrical signal transmission through a sliding contact as a function of the relative amount of graphite and copper in the brush. Particular attention was given to the correlation between electrical signal fluctuation and tribological properties in an electrical sliding contact system. A ring-on-block type tribotester was used for this experiment and the ring was made from pure copper. Results showed that a copper-graphite brush at a particular composition range exhibited the most stable frictional behavior with a minimum voltage drop. The amount of voltage drop at the friction interface was affected by the surface roughness, transfer film formation at the friction interface, and the real area of contact. Microscopic observations and the surface analysis showed a good agreement with the results from this experiment. The results also indicated that the electrical signal flunctuation was directly associated with the oscillation of the coefficient of friction during sliding by nanoscale variation of contacts at the friction interface.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.3
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• pp.41-49
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• 2010

Two promising control candidates have been selected to test the sinusoidal reference tracking performance for a brush-type polishing machine having strong nonlinearities and disturbances. The controlled target system is an oscillating mechanism consisting of a common positioning stage of one degree-of-freedom with a screw and a ball nut driven by a servo motor those can be obtained commercially. Beside the strong nonlinearity such as stick-slip friction, the periodic contact of the polishing brush and the work piece adds an external disturbance. Selected control candidates are a Sliding Mode Control (SMC) and a variant of a feedback linearization control called Smooth Robust Nonlinear Control (SRNC). A SMC and SRNC are selected since they have good theoretical backgrounds, are suitable to be implemented in a digital environment and show good disturbance and modeling uncertainty rejection performance. It should be also noted that SRNC has a nobel approach in that it uses the position information to compensate the stickslip friction. For both controllers analytical and experimental studies have been conducted to show control design approaches and to compare the performance against the strong nonlinearity and the disturbances.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.641-643
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• 2002

Synchronous generator needs slip-ring and brush for supplying current to rotor with external source. but slip-ring and brush have some problems to supply DC power to field winding with friction and high power loss due to brush voltage drop at high field current. Thus synchronous generator have been designed to brushless machine. Brushless synchronous machines of using permanent halbach array can composed without back core and coreloss. In this paper, analyse on the characteristics of external rotor type permenant magnet brushless with halbach array.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.606-607
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• 2008

Nowadays, noise and vibration phenomena of a disc brake system have been given various names that provide some definitions of sound and vibration emitted such as grind, grunt, moan, squeak, squeal, judder and wire brush. The most common and annoying noise of a disc brake system is squeal noise. It is defined as noise whose frequency content is 1 kHz and higher with excessively high and irrigating sound pressure levels. In this paper, the noise and vibration characteristics of a disc brake system have been investigated to develop the fusion-type friction material, which overcomes the low steel and non-asbestos organic friction materials. For the purpose, both experimental evaluation and complex eigenvalue analysis have been carried out.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.2
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• pp.774-780
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• 2021

The auxiliary power unit (APU) of a rotorcraft starts the engine during operation/flying. The APU is composed of a gas turbine engine type. The starting principle of the component is that the electric start motor generates the power required for starting by rotating the shaft. In this study, quality improvement was performed by applying an over-running clutch (ORC) between the APU and the starter motor to secure the operability of the starter motor of the APU mounted on the rotorcraft. The starter motor has the main role of starting the APU, but during operation, it is rotated without load by the rotational force of the APU gear shaft, resulting in friction at the brush. This phenomenon causes abrasion of the brush of the starter motor. Consequently, when the APU operation time increases, the brush life decreases, and the operability of the APU is affected. In this study, an ORC that separates the interlocking between the start motor brush abrasion and the APU operation time was applied to improve the operability/durability of the APU starter motor. The effect was verified through a test, and the technical feasibility of the design change was analyzed.

• Journal of Biosystems Engineering
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• v.41 no.3
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• pp.201-207
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• 2016

Purpose: A water-spraying type automatic glochids removal system for cactus (Opuntia humifusa) stem was developed, and its performance was evaluated. The system was developed to reduce intensive human labor in removing glochids from cactus stem skin without inducing damage prior to further processing into value-added products. Methods: The developed system consists of conveyor and water-spraying systems. The conveyor system delivers cactus stems through water-spraying compartments and finally to a collecting box. In order to remove the glochids, rotating nozzles spray water over all areas (i.e., front and back faces and sides) of the cactus skin under controlled water pressure. Operating conditions such as conveyor speed, water pressure, angle of water-spraying nozzles, distance between conveyor belt and rotating nozzles, and angle of cactus flipping slide were adopted from our previous study and applied on the system design and manufacturing. The performance of glochids removal was evaluated by counting the number of glochids on the cactus stem before and after processing on the system. Results: The developed system performed efficiently and effectively under the pre-studied operating conditions except for the angle of cactus flipping slide. The new system had a glochids removal ratio of 94.1% without damaging the cactus skin. Considering the original number (approximately 30-60) of glochids, the remaining number was low (1-4), and most of them were found at the side edge of the cactus stem. This system can remove glochids from 360 cactus stems in 1 hr regardless of cactus size. Conclusions: The performance of the new system in glochids removal without damaging cactus skin is superior to any other existing device (i.e., brush type, rubber-friction type, and agitation type). The system is expected to be applied in cactus (O. humifusa) processing facilities.