• Journal of the Korean Society for Precision Engineering
• /
• v.18 no.11
• /
• pp.138-147
• /
• 2001

Alignment systems are frequently used under various semiconductor manufacturing environment. Particularly in PDP(Plasma Display Panel) manufacturing process, the alignment system is applied to the combining and sealing processes of the upper and lower glass panels of PDP, where these processes are performed in the vacuum chamber of high vacuum and high temperature. In this paper, the XYΘ-alignment stage is developed to align PDP panels. Because of high vacuum and high temperature environment, the alignment chamber has been designed to isolate the inner part of the alignment chamber from the outer environment of high vacuum and high temperature, in which every part of the alignment stage is inserted. As it is difficult to attach feedback sensors to the alignment stage in the alignment chamber, the alignment stage is implemented with the open loop algorithm, where the parallel link structure has been designed using step-motors and ball-screws for structural simplicity. The kinematic analysis is performed to drive the parallel link structure, based on the experiments of actuation-compensation of the alignment stage. For the error compensation, the hyperpatch model has been used to model the errors. From the experiments, the positional accuracy of the alignment stage can be improved significantly.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.45 no.10
• /
• pp.836-843
• /
• 2017

In lunar exploration, the necessity of utilizing rover is verified by the examples of the Soviet Union and China and the similar Mars missions of the United States. In order to achieve the successful management of a lunar rover, a high precision navigation technique is required, and accordingly, high precision initial alignment is essential. Even though it is general to perform initial alignment in a steady state, a multiposition alignment technique is applied when high performance is needed. On the lunar surface, however, the performance of initial alignment decreases from that on Earth, and it cannot be improved by applying multiposition alignment method owing to certain constraints of lunar environment. In this paper, a sun sensor aided multiposition alignment technique is proposed. The measurement model for a sun vector is established, and its observability analysis is performed. The performance of the proposed algorithm is verified through computer simulations, and the results show the estimation performance is improved dramatically.

• 한국전산유체공학회:학술대회논문집
• /
• 2008.03b
• /
• pp.389-392
• /
• 2008

The thrust axis alignment of the launch vehicle is very important because of the misalignment causes the unstable attitude control and results in mission failure. Generally, optical methods such as digital theodolite and laser tracker and mechanical method such as turn table method are used to thrust axis alignment. This article deals with the simple method of thrust axis alignment of Kick Motor.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2005.07a
• /
• pp.755-758
• /
• 2005

The mechanism responsible for liquid crystal (LC) alignment on solid substrates treated with mechanical rubbing or polarized UV is not understood. The results of x-ray reflectivity study of LC alignment on a large number of different alignment layers show that the anisotropy in the surface roughness of the substrate completely determines the LC alignment. The anchoring energy depends on the degree of roughness anisotropy and chemical interactions between the substrate and LC molecules.

• Proceedings of the SAREK Conference
• /
• 2005.11a
• /
• pp.274-280
• /
• 2005

The objective of this study Is to investigate the heat transfer performance of plate discrete fin-and-tube heat exchangers with large fin pitch. In this study, twenty-two heat exchangers were tested with a variation of fin pitch, number of tube row, longitudinal tube pitch and fin alignment. Discrete fin type exchangers improved heat transfer performance more than 10% compared to tile continuous fin type heat exchangers. The air-side heat transfer coefficient decreased with a reduction of the fin pitch and an increase of the number of tube row, The staggered fin alignment improved heat transfer performance more than 6% compared to the inline fin alignment. The effect of longitudinal tube pitch was insignificant on the j-factor and experiments found opposite effects on the j-factor with respect to fin alignment. Heat transfer correlations were developed from the measured data for flat plate discrete fin-and-tube heat exchangers with large fin pitch. The correlations yielded good predictions of the measured data with mean deviations of 1,4% and 0.3% for tire inline and staggered tube alignment, respectively.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.39 no.9
• /
• pp.879-884
• /
• 2015

Printed electronics is a technology that produces electronic devices and circuits by printing functional ink on a web, which is a film-like flexible material. This technology is suitable for large-scale and high-speed mass production, and is a next-generation process technology that can fabricate electronic devices from flexible materials. As precise measurement of the positions of the web is required in order to commercialize such a printed electronics process, a measurement system with an optical encoder with a precision of micrometers had been proposed in the preceding research of this study. However, the lateral positions of the web could not be measured in the preceding research as the phenomenon of the entire web being moved in the lateral direction could not be detected. In this study, a measurement system that utilizes the differences in the amount of light reflected from the alignment patterns depending on the web positions in the lateral direction was proposed for measuring the lateral positions of the web. In addition, its reliability was verified and then the effect when measuring printed alignment patterns was analyzed by experiments.

• Journal of Sensor Science and Technology
• /
• v.28 no.1
• /
• pp.30-35
• /
• 2019

Inertial measurement units (IMUs) are widely used for wearable motion-capturing systems in the fields of biomechanics and robotics. When the IMUs are combined with optical motion sensors (hereafter, OPTs) for their complementary capabilities, it is necessary to align the coordinate system orientations between the IMU and OPT. In this study, we compare the application of two coordinate transformation-based orientation alignment methods between two coordinate systems. The first method (M1) applies angular velocity coordinate transformation, while the other method (M2) applies gyroscopic angle coordinate transformation. In M1 and M2, the angular velocities and angles, respectively, are acquired during random movement for a least-square algorithm to determine the alignment matrix between the two coordinate systems. The performance of each method is evaluated under various conditions according to the type of motion during measurement, number of data points, amount of noise, and the alignment matrix. The results show that M1 is free from drift errors, while drift errors are present in most cases where M2 is applied. Thus, this study indicates that M1 has a far superior performance than M2 for the alignment of IMU and OPT coordinate systems for motion analysis.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.21 no.3
• /
• pp.100-109
• /
• 2022

In this study, calibration technology that increases the alignment accuracy in large flexible flat panels was studied. For precise of calibration, a systematization of the calibration algorithm was established, and a calibration correction technique was studied to revise calibration errors. A coordinate systems of camera and UVW stage was established to get the global position of the mark, and equations for translational and rotational calibration were systematically derived based on geometrical analysis. Correction process for the calibration data was carried, and alignment experiments were performed sequentially in cases of the presence or absence of calibration-correction. Alignment results of both calibration correction and non-calibration correction showed accuracy performance less than 1㎛. On the other hand, the standard deviation in calibration-correction is smaller than non-calibration correction. Therefore, calibration correction showed improvement of the alignment repeatability.

• Journal of the Semiconductor & Display Technology
• /
• v.10 no.4
• /
• pp.79-87
• /
• 2011

In this paper, suggested is a hybrid-type visual alignment system to align mask and panel in 3-D space, where mask and panel are to be controlled independently by two individual positioning mechanisms in order to compensate for spatial misalignments. In the hybrid visual alignment system, the below 4-PPR parallel mechanism provides in-plain motions to pattern mask like the other conventional alignment systems while the above 4-RPS parallel mechanism is to move glass panel to achieve a complete spatial alignment. For the control of the hybrid alignment system, first, inverse kinematic solutions for the parallel mechanisms are given to determine the driving distance of each active joint, and also an efficient way to determine the spatial alignment error is developed by exploiting three in-plane cameras.

• Korean Journal of Applied Biomechanics
• /
• v.25 no.2
• /
• pp.183-190
• /
• 2015

Objective : Walking with a Material handling is an activity frequently undertaken by agricultural workers in Korea, due to the nature of their work. This study aimed to investigate differences in biomechanical variables according to the mechanical alignment of the lower limbs when walking with a heavy load, and to use this as basic data in the design of various working environments to reduce the skeletomuscular burden on the knee joint. Method : The study subjects comprised of 22 right-foot dominant adult men and women aged between 20 and 23 years. The subjects were divided into a varus or valgus group according to the mechanical alignment of the lower limb by using radiographic findings. The subjects walked without any load and with a load of 10%, 20%, or 30% of their body weight held in front of them. The Kwon3d XP program was used to calculate biomechanical variables. Results : The flexion/extension moment of the knee joint showed a decreasing trend with increased load, irrespective of the mechanical alignment of the lower limb, while the varus group did not show normal compensatory action when supported by one leg at the point of maximum vertical ground reaction force. In addition, in terms of the time taken, subjects showed no difficulties in one-foot support time up to 20%/BW, but at 30%/BW, despite individual differences, there was an increase in single limb. The increased load resulted in a decrease in the ratio of standing phase to ensure physical stability. The valgus group showed a trend of increasing the stability of their center of mass with increasing load, through higher braking power in the early standing phase. Conclusion : In conclusion, although there was no statistical difference in biomechanical variables according to the mechanical alignment of the lower limbs, the varus group showed a more irregular walking pattern with a Material handling than the valgus group, partially proving the association between lower limb alignment and walking with a Material handling.