• Journal of Ocean Engineering and Technology
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• v.31 no.2
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• pp.177-182
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• 2017

This paper describes an unscented Kalman filter approach to estimate the bias in magnetic field measurements. A microelectromechanical systems attitude heading reference system (MEMS AHRS) was used to measure the magnetic field, together with the acceleration and angular rate. A magnetic field is usually used for yaw detection, while the acceleration serves to detect the roll and pitch. Magnetic field measurements are vulnerable to distortion due to hard-iron effect and soft-iron effect. The bias in the measurement accounts for the hard-iron effect, and this paper focuses on an approach to estimate this bias. The proposed method is compared with other methods through experiments that implement the navigation of an underwater robot using an AHRS and Doppler velocity log. The results verify that the compensation of the bias by the proposed method improves the navigation performance more than or comparable to the compensation by other methods.

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.316-321
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• 2001

The optical storage device has recently experienced significant improvement, especially for the aspects of high capacity and fast transfer rate. However, it is necessary to study a new shape of air bearing surface for the rotary type actuator because the optical storage device has the lower access time than that of HDD (Hard Disk Drives). In this study, we proposed the air bearing shape by using SA (Simulated Annealing) algorithm which is very effective to achieve the global optimum instead of many local optimums. The objective of optimization is to minimize the deviation in flying height from a target value 100nm. In addition, the pitch and roll angle should be maintained within the operation limits.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.2
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• pp.107-117
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• 1998

As the traffic congestion and parking problems in urban areas are increased the tall and narrow commuter vehicles have interested as a means to increase the utilization of existing freewa- ys and parking facilities. However, in hard cornering those vehicles could reduce stability against overturning compared to conventional vehicles. This tendency can be mitigated by tilting the body toward the inside of the turn. In this paper those tilting vehicles are considered in which at speed at least, the tilt angle is controlled by steering the front wheels. In other word, if the driver turns the steering wheel the tilt controller automatically steers the road wheel to tilt the body inside of the turn. Also, the dynamic tilting vehicle model with tire slip angles is constructed by adding the roll degree of freedom. Finally, through computer simulation the behaviors of the tilting vehicles are investigated.

• Tribology and Lubricants
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• v.8 no.2
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• pp.26-34
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• 1992

This paper suggests a method to predict the flying state of the head slider in a hard disk drive (HDD) by using an optimization technique. The modified Reynolds equation for the hydrodynamic lubrication theory under the slip flow condition is used to describe the air-bearing system and a Finite Volume Method (FVM) is applied to solve the equation. Especially, Augmented Lagrange Multiplier (ALM) method is employed to find the minimum flying height, the pitch angle and the roll angle of the slider, which is shown to be faster and more general than the conventional update schemes. By using the proposed method, the variations of the flying state are analyzed as a function of the slider position in the direction of the disk radius for various disk velocities and skew angles.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.359-359
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• 2011

Many research applications in basic sciences and biology such as protein crystallography require hard x-rays in the range of 3-20 keV with high brightness. A medium energy storage ring as PLS-II with a beam energy of 3 GeV can meet such high photon energies. In-vacuum undulators (IVU) with a period length of 20 mm and a peak field of 0.97 T are used in the PLS-II ring to produce such X-rays in the fundamental or higher harmonics. Due to the many poles and high fields, insertion devices like wigglers and undulators have a significant impact on the stability of the electron beam with potential degradation of beam quality and life time. Therefore, nonlinear fields must be determined by measurement and evaluated as to their impact on beam stability. Specifically, transverse field roll-off can be a serious detriment to injection in top-up mode and must be corrected. We use magnetic field measurement data to evaluated beam stability by tracking particles using an explicit symplectic integrator in both, transverse and longitudinal planes.

• Proceedings of the KIEE Conference
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• 2003.11c
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• pp.456-459
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• 2003

This paper deal with the biped walking stability by inverted pendulum type balancing joints. This model is hard to interpretation for the nonlinearity caused by upper direction movement then conventional model which have roll and prismatic joints. We can interpret this model by a linear approximation or interpolation method. This paper use a linear approximation method that can decide a movement of upper direction. Inverted pendulum type balancing joints have a advantage of less movement for keep stability and similar with human than conventional model and this model can be used for humanoid robot. We can see a stability of biped by ZMP(Zero Moment Point). Genetic algorithm is used for trajectory planning that is important for stable walking of biped.

• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.5
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• pp.463-470
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• 2015

When a camera installed on a vehicle is used, estimation of the camera pose including tilt, roll, and pan angle with respect to the world coordinate system is important to associate camera coordinates with world coordinates. Previous approaches using huge calibration patterns have the disadvantage that the calibration patterns are costly to make and install. And, previous approaches exploiting multiple vanishing points detected in a single image are not suitable for automotive applications as a scene where multiple vanishing points can be captured by a front camera is hard to find in our daily environment. This paper proposes a camera pose estimation method. It collects multiple images of lane markings while changing the horizontal angle with respect to the markings. One vanishing point, the cross point of the left and right lane marking, is detected in each image, and vanishing line is estimated based on the detected vanishing points. Finally, camera pose is estimated from the vanishing line. The proposed method is based on the fact that planar motion does not change the vanishing line of the plane and the normal vector of the plane can be estimated by the vanishing line. Experiments with large and small tilt and roll angle show that the proposed method outputs accurate estimation results respectively. It is verified by checking the lane markings are up right in the bird's eye view image when the pan angle is compensated.

• The korean journal of orthodontics
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• v.53 no.6
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• pp.402-419
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• 2023

Objective: This study assessed the differences in soft tissue deviations of the nose, lips, and chin between different mandibular asymmetry types in Class III patients. Methods: Cone-beam computed tomography data from 90 Class III patients with moderate-to-severe facial asymmetry were investigated. The sample was divided into three groups based on the extent of mandibular rolling, yawing, and translation. Soft tissue landmarks on the nose, lips, and chin were investigated vertically, transversely, and anteroposteriorly. A paired t test was performed to compare variables between the deviated (Dv) and nondeviated (NDv) sides, and one-way analysis of variance with Tukey's post-hoc test was performed for intergroup comparisons. Pearson's correlation coefficient was calculated to assess the relationship between the soft and hard tissue deviations. Results: The roll-dominant group showed significantly greater differences in the vertical positions of the soft tissue landmarks between the Dv and NDv than other groups (P < 0.05), whereas the yaw-dominant group exhibited larger differences in the transverse and anteroposterior directions (P < 0.05). Moreover, transverse lip cant was correlated with the menton (Me) deviation and mandibular rolling in the roll-dominant group (P < 0.001); the angulation of the nasal bridge or philtrum was correlated with the Me deviation and mandibular yawing in the yaw-dominant group (P < 0.01). Conclusions: The three-dimensional deviations of facial soft tissue differed based on the mandibular asymmetry types in Class III patients with similar amounts of Me deviation. A precise understanding of soft tissue deviation in each asymmetry type would help achieve satisfactory facial esthetics.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.8
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• pp.1545-1551
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• 2002

The optical storage device has recently experienced significant improvement, especially for the aspects of high capacity and fast transfer rate. However, it is necessary to study a new shape of air bearing surface for the rotary type actuator because the optical storage device has the lower access time than that of HDD (Hard Disk Drives). In this study, we proposed the air bearing shape by using SA (Simulated Annealing) algorithm which is very effective to achieve the global optimum instead of many local optimums. The objective of optimization is to minimize the deviation in flying height from a target value 100nm. In addition, the pitch and roll angle should be maintained within the operation limits.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2012.03a
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• pp.105-105
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• 2012

기능성 아웃도어 제품을 제조하기 위해서 사용되어지는 멤브레인은 크게 미세다공형과 친수무공형으로 구분할 수 있다. 최근에는 소비자들이 기능성 아웃도어에 쾌적성을 요구하고 있으며, 그 측면에서 본다면 미세다공형 멤브레인이 친수무공형보다 유리하다. 기존의 미세다공형 멤브레인은 고가이며, casting이 불가능한 단점을 가지고 있다. 본 연구에서는 분자구조 및 유화제 첨가에 따른 casting이 가능한 미세다공형 폴리우레탄 멤브레인의 특성에 대하여 연구하였다. Casting용 미세다공형 폴리우레탄은 soft segment와 hard segment의 비가 1/2일 때, 그리고 사용되는 용제가 MEK 단독일 때 안정적인 반응성과 이상적인 필름의 물성을 보이는 것을 확인 하였으며, 수지에 첨가되는 분산유화제의 양이 10%이상일 때 상분리 현상이 발생하지 않음을 확인 할 수 있었다. 개발된 수지의 적용성을 평가한 결과, J-knife를 이용하여 knife over roll 방식으로 25~35$g/m^2$ (dry add on)를 도포하여 $80/120/140^{\circ}C{\times}10m/min$의 다단건조 공정으로 진행했을 때 최적의 물성을 얻을 수 있었다.