• Transactions of the Society of Information Storage Systems
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• v.8 no.2
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• pp.67-71
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• 2012

Page-oriented holographic data storage (HDS) is very sensitive to the tilt error. Therefore, tilt error should be measured and compensated. Especially, mechanical tilt measurement method cannot cope with tilt error measurement because photopolymer medium has shrinkage problem. Therefore, the method to solve this problem is using the reconstructed image which can represent both tilt and shrinkage effect. In this paper, we suggest disc tilt measurement algorithm using image pattern of retrieval data.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.2
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• pp.149-156
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• 2014

A magnetic compass module must be calibrated accurately before use. Moreover, the calibration process must be performed taking into account any magnetic dip if the magnetic compass module has tilt angles. For this, a calibration method for a magnetic compass module is explained. Tilt error of the magnetic compass module is compensated using a biaxial accelerometer generally. The accelerometer error causes a tilt angle calculation error that gives rise to an azimuth calculation error. For error property analysis, error equations are derived and simulations are performed. In the simulation results, the accuracy of derived error equations is verified. If a biaxial magnetic compass module is used instead of a triaxial one, the magnetic dip and z-axis magnetic compass data must be estimated for tilt compensation. Lastly, estimation equations for the magnetic dip and z-axis magnetic compass data are derived, and the performance of the equations is verified based on a simulation.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.219.2-219.2
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• 2012

We are developing Adaptive Optics (AO) system for 24 inch telescope at Seoul National University Observatory. It consists of the tip-tilt correction system and the residual wavefront error correction system with a deformable mirror and a wavefront sensor. We present the construction and performance measurements of the tip-tilt correction system. The tip-tilt component is the single largest contributor to wavefront error, especially for small telescope. The tip-tilt correction system consists of a quadrant photodiode, a tip-tilt mirror and a feed back loop. The collimated He-Ne laser beam is used for input light source and is artificially disturbed by air turbulence generated by a heat gun. Most of the turbulence is of low frequency less than 20 Hz, but extends to a few hundreds Hz. It is found that the closed loop system using proportional-integral-derivative (PID) control successfully corrects tip-tilt error at a rate as high as 300~400 Hz.

• The Journal of Korean Society for Radiation Therapy
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• v.22 no.2
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• pp.85-95
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• 2010

Purpose: The degradation of an image quality and error of the beam dose calculation can be caused because the metal artifact is generated during the CT simulation of head and neck patient. The usability of the gantry tilt scan for reducing the metal artifact tries to be appraised. Materials and Methods: The inferior $20^{\circ}$ gantry tilt scan was made in order to reduce the metal artifact and $0^{\circ}$ reconstruction image was acquired. The AAPM CT performance Phantom was used in order to compare the CT number of the reconstructed image and Original image. the difference of volume was compared by using the acrylic phantom. The homogeneity of the CT number was evaluated the Intensity volume Histogram (IVH) as in order to evaluate an influence by the metal artifact. A dose was evaluated as the Dose Volume Histogram (DVH). Results: in the comparison of the CT number and volume, the difference showed up less than 0.5%. As to the comparison of IVH, in the gantry tilt scan, influence by an artifact was reduced and the homogeneity of the CT number was improved. The comparison of DVH result reduced the mean dose error of the both sides parotid 0.2~6%. Conclusion: In the Head & Neck radiation therapy, It is difficult and to distinguish tumor and normal tissue and the error of dose is generated by the metal artifact. The delineation of the exact organization was possible if the Gantry tilt scan was used. The CT number homogeneity was improved and the error of dose could be reduced. The Gantry tilt scan confirmed in the Head & Neck radiation therapy to be very useful in the exact radiation therapy.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.856-860
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• 2008

Wire-suspensions in the conventional actuators mechanically support the moving part and guarantee the accuracy of the actuator without tangential tilt actuation. However, such a suspension configuration has considerable stiffness in the tangential tilt direction with two additional wire beams for the tangential tilt. Thus, we performed a design sensitivity analysis for the wire-suspension stiffness of 4-axis actuator and controlled the main parameters such as distance among wire-suspensions and wire-suspension length to allow tangential tilt flexibility. The elasticity of frame PCB that supports the moving part by wire-suspensions was also exploited to improve the flexibility of wire-suspension in the tangential tilt direction. A novel suspension structure was devised by establishing eight wire-suspensions at both sides of the moving part for electrical connection to coils. The magnetic circuit according to the proposed 4-axis actuator using multi-polar magnet and coils was also suggested for the generation of electromagnetic forces in the focusing, tracking, radial and tangential tilt directions.

• ETRI Journal
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• v.27 no.3
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• pp.280-288
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• 2005

This paper presents an efficient algorithm for using the two-axis magnetic compass in portable devices. The general magnetic compass module consists of a three-axis magnetic compass and a two-axis inclinometer to calculate tilt-compensated azimuth information. In this paper, the tilt error is compensated using just a two-axis magnetic compass and two-axis accelerometer. The third-axis data of the magnetic compass is estimated using coordinate information that includes the extended dip angle and tilt information. The extended dip angle is estimated during the normalization process. This algorithm can be used to provide the tilt-compensated heading information to small portable devices such as navigation systems, PDAs, cell phones, and so on.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.479-484
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• 1996

This paper describes a method of measuring tilt motion. This method measures the tilt motion of drilling machines using a laser interferometer, a simple sliding linear bearing, measurement of the probe and the LSC(least square center) method. The next order of business is discussing the procedure of measurement. First, The measured position is considered to be the point of contact between the drill shank and the probe. The revolution of the drill axis delivers the point of contact to the probe. Second, because the laser interferometer is attached on the sliding linear bearing, any movement of probe influences laser reflector. Thus, the laser program displays the moving factor of laser reflector. Namely, this is tilt factor. Third. the points of measurement are a full circle which has 8 points (each are 45$^{\circ}$), After it is finished measuring the 8 points, let the spindle of the drilling machine move down about 5 cm. Repeating this procedure three times, we can get tilt motion's values which are calculated by LSC method. Many error factors affect the accurate measurement of tilt motion. However in this paper we ignore some error factors because they are less significant than tilt motion.

• Journal of Biosystems Engineering
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• v.25 no.3
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• pp.233-240
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• 2000

A commercially available Doppler radar was modified and evaluated for on-board monitoring of ground speed. The radar output was corrected for pitch angle of aircraft based on the output of an electrolytic tilt sensor. The effects of aircraft speed, height and mounting angle on error in the ground speed were evaluated. The speed error decreased with an increase of the mounting angle since the radar contact angle with respect to the ground approached to the mounting angle. The error increased with an increase of the nominal aircraft speed. The altitude insignificantly affected the speed error. The Doppler radar provided acceptable percent errors within 5% in most measurements. The error can be reduced within ${\pm}$1.5% by increasing the mounting angle ($43^{\circ}$). The error of -3.8% at the mounting angle of $29^{\circ}$could be reduced by adjusting the mounting angle with respect to the radar contact angle.

• Transactions of the Society of Information Storage Systems
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• v.7 no.1
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• pp.19-24
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• 2011

Holographic Data Storage System, one of the next generation data storage devices, is a 2-dimensional page oriented memory system using volume holograms in writing and retrieving process. Recently photopolymer with disc type substrate was selected as a media for the Holographic Data Storage System. The disc tilt occurs when the media rotates and the external disturbance applies. The disc tilt causes the change of the angle between the reference beam and the media, the data cannot be retrieved with the right angle or other data page is retrieved. The tilt is generated in a 2-axis direction (tangential, radial). The tangential tilt direction is the same with the multiplexing plane, while the radial tilt direction is a perpendicular to the multiplexing plane. In this research we propose 2-axis tilt angle servo system. The tilt errors are measured by using external photo detector and the additional red laser. Then the tangential direction tilt is compensated by using the galvano mirror. Also the radial direction tilt is compensated by the rotating prism between the relay lens in the reference field. Finally we confirm the compensation results through the Signal to Noise Ratio(SNR) and Bit Error Rate(BER).

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.330-333
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• 2003

In this thesis. the application of the synchronizing control of the intelligent indoor lift system is showed. The separate axes of the indoor lift system are driven independently. PID controller, synchronous flexible logic compensating method and tilt sensor are applied to enhance the performance of the intelligent indoor lift system. the tilt sensor senses the horizontal error of the whole system. PID controller and synchronous flexible logic are used to compensate the synchronous errors of both the separate axes and whole system to be zero. Namely, using not the hardware coupling but the software algorithm. the indoor life system is operated without the error. Before applying the real system, the simulation using matlab testifies the possibility of the lift system. And the realization of the system is demonstrated with two DC servo motors. In the experiment test, flexible logic to compensate the synchronous error is chosen by the comparative method. the indoor lift system has to be considered the loading factor as the disturbance. Because the intelligent indoor lift system is developed to support the patients who don't change for themselves to move. finally, the system which considers the weight of the patient as the disturbance can carry the patients safely without synchronous and position error.