• Tribology and Lubricants
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• v.37 no.4
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• pp.129-135
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• 2021

An air-bearing stage uses externally pressurized air as the lubricant between the stage and the rail. The supporting force generated by the supplied air makes the stage rise and move smoothly with extremely low friction. Mechanical contacts rarely happen, the bearing surfaces do not produce wear particles, and dust is not generated. It also has the advantage of having low energy loss and high precision. Because of its advantages, an air-bearing stage is used in several types of machines that require high precision. In this article, the effect of the pocket depth on the hammering phenomena of the air bearing is studied. An analysis program is developed to calculate the dynamic behavior of the stage by solving the Reynolds equation between the stage and the guideway and the equations of motion on the stage. The acceleration, constant movement, and deceleration are applied to the stage. The stage is modeled as a five-degree-of-freedom system. In the course of the dynamic behavior, the hammering phenomena occur under some special conditions. The deeper the pocket, the more unstable the behavior of the stage, and air hammering occurs when it exceeds a certain depth. In addition, the higher the supply pressure, the more unstable the behavior of the stage. However, hammering occurs even with a shallow pocket depth. Other conditions that affect the hammering phenomena are calculated and discussed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.7
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• pp.3158-3163
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• 2013

In this study, squeal noise test was conducted by using the lab-scaled brake dynamometer. Squeal conditions with respect to the angle of the brake pads ($34^{\circ}30^{\circ}26^{\circ}$) and negative slope, were studied. Squeal frequency of the In-plane-like mode was confirmed by hammering test and finite element analysis. This Squeal mode was difficult to control by the pad angle variation. Also the squeal sound was found to be periodic signal which has higher harmonic components. Squeal noise is independent of the negative slope. It implies that squeal noise can reach the stick-slip oscillation.

• Korean Journal of Optics and Photonics
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• v.10 no.1
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• pp.73-79
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• 1999

Semiconductor optical switch modules of 1$\times$2, 1$\times$4, and 4$\times$4 types for 1550 nm optical communication systems were fabricated by using laser welding technique, embodying in 30-pin butterfly package. For better coupling efficiency between switch chip and optical fiber, tapered fibers of 10~15mm lens radii were used, which provided up to 60% optical coupling efficiency. With the help of new laser hammering process, we could recover the lost optical power almost completely up to average 82% of initially obtained power. The fabricated optical switch modules showed good thermal stability of less than 5% degradation even after 200 times thermal cycling test. The 2.5 Gbps optical transmission characteristics of the 4$\times$4 switch module showed low sensitivities of less than -30dB for all possible switching paths. The transmission penalties of 1$\times$2 switch module at $10^{-10}$ BER were 0.6dB and 0.7dB for 50Xm and 90 Km optical fibers, respectively.