• 대한치과교정학회지
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• 제52권2호
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• pp.85-101
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• 2022

Objective: To classify facial asymmetry (FA) phenotypes in adult patients with skeletal Class III (C-III) malocclusion. Methods: A total of 120 C-III patients who underwent orthognathic surgery (OGS) and whose three-dimensional computed tomography images were taken one month prior to OGS were evaluated. Thirty hard tissue landmarks were identified. After measurement of 22 variables, including cant (°, mm), shift (mm), and yaw (°) of the maxilla, maxillary dentition (Max-dent), mandibular dentition, mandible, and mandibular border (Man-border) and differences in the frontal ramus angle (FRA, °) and ramus height (RH, mm), K-means cluster analysis was conducted using three variables (cant in the Max-dent [mm] and shift [mm] and yaw [°] in the Manborder). Statistical analyses were conducted to characterize the differences in the FA variables among the clusters. Results: The FA phenotypes were classified into five types: 1) non-asymmetry type (35.8%); 2) maxillary-cant type (14.2%; severe cant of the Max-dent, mild shift of the Man-border); 3) mandibular-shift and yaw type (16.7%; moderate shift and yaw of the Man-border, mild RH-difference); 4) complex type (9.2%; severe cant of the Max-dent, moderate cant, severe shift, and severe yaw of the Man-border, moderate differences in FRA and RH); and 5) maxillary reverse-cant type (24.2%; reverse-cant of the Max-dent). Strategic decompensation by pre-surgical orthodontic treatment and considerations for OGS planning were proposed according to the FA phenotypes. Conclusions: This FA phenotype classification may be an effective tool for differential diagnosis and surgical planning for Class III patients with FA.

• Transactions on Control, Automation and Systems Engineering
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• 제4권3호
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• pp.231-238
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• 2002

In this paper, we present a new approach to autopilot design for skid-to-turn missiles which may have severe aerodynamic cross-couplings and nonlinearities with angle of attack. The model of missile motion is derived in the maneuver plane and, based on that model, pitch, yaw, and roll autopilot are designed. They are composed of a nonlinear term which compensates for the aerodynamic couplings and nonlinearities and a linear controller driven by the measured outputs of missile accelerations and angular rates. Besides the outputs, further information such as Mach number, dynamic pressure, total angle of attack, and bank angle is required. With the proposed autopilot and simple estimators of bank angle and total angle of attack, it is shown by computer simulations that the induced moments and some aerodynamic nonlinearities are properly compensated and that the performance is superior to that of the conventional ones.

• 한국자동차공학회논문집
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• 제24권2호
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• pp.198-204
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• 2016

In this study, a wind tunnel test was conducted to measure the aerodynamic characteristics of a streamline-designed high-speed bus with the change of wind direction and speed and the result is compared with the aerodynamic performance of a commercialized high-speed bus model (Model-0) manufactured by Zyle Daewoo Bus Corp. Aerodynamic performance of the existing rear-spoiler was tested to prove its aerodynamic effect on the test model bus. From the study, it was found that 24.6 % of the total drag of the original bus model (Model-0) was reduced on the streamline-designed model bus(model-1) without the rear-spoiler but only 14.3 % of the total drag was reduced with the spoiler on the streamlined model bus. It means that the rear spoiler does not work properly with the streamlined model bus (model-1) and should be noted that an optimum design of a rear-spoiler of a vehicle is important to reduce the induced pressure drag and increase the driving stability of a vehicle against yaw motion. The experimental outcome was also compared to the previous numerical research result to evaluate the reliability of the numerical algorithm of the aerodynamic performance analysis of a vehicle. The error rate (%) of the numerical result to the experimental output is about 5.4 % and it is due to the simplified body configuration of the numerical model bus. The drag increases at the higher yaw angle because the transparent frontal area of the model vehicle increases and the downward force increases with the yaw angle as well. It has a positive effect to the driving stability of the vehicle but the moderated downward force should be kept for the fuel economy of a vehicle.

• 한국군사과학기술학회지
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• 제15권6호
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• pp.721-728
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• 2012

The tracked SUGVs(Small Unmanned Ground Vehicles) are frequently operated in the narrow slope such as stairs and trails. But due to the nature of the tracked vehicle which is steered using friction between the track and the ground and the limited field of view of driving cameras mounted on the lower position, it is not easy for SUGVs to trace narrow slopes. To properly trace inclined narrows, it is very important for SUGVs to keep it's heading direction to the slope. As a matter of factor, no roll value control of a SUGV can makes it's heading being located in the direction of the slope in general terrains. But, the problem is that we cannot directly control roll motion for SUGV. Instead we can control yaw motion. In this paper, a new slope driving method that enables the vehicle trace the narrow slopes with IMU sensor usually mounted in the SUGV is suggested which including an estimation technique of the desired yaw angle corresponding to zero roll angle. In addition, a fuzzy steering controller robust to changes in driving speed and the stair geometry is designed to simulate narrow slope driving with the suggested method. It is shown that the suggested method is quite effective through the simulation.

• Current Research on Agriculture and Life Sciences
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• 제32권3호
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• pp.159-163
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• 2014

본 논문에서는 저가의 MEMS 관성 센서와 지자기 센서를 이용하여 자세 정보를 제공받는 자세측정장치(ARHS)를 구현하였다. 저가형 IMU센서와 MCU를 이용하여 운동 자세각을 계산하는 DCM 알고리즘을 설계하고, 3축짐벌에 장착하여 연산결과의 정확도를 측정하였다. DCM 알고리즘을 이용 연산된 자세각의 정확도는 roll 및 pitch에 대하여 약 1.1%로 나타났으며, yaw각의 경우는 3.7%로 나타났다. Yaw 각의 경우에는 스텝핑 모터를 구동하는 실험환경에 따른 교란의 영향으로 그 오차가 상대적으로 크게 나타난 것으로 평가되었다. 짐벌 실험장치를 이용한 센서의 검증에서 더욱 정밀한 실험을 위해서는 주변 환경 요인에 대한 제어가 요구될 것으로 보이며, 실험장치의 스테핑 모터 구동 시 발생하는 진동 및 자기장의 영향과 실험 장치의 금속성 구조물의 영향으로 생각되는 센서 데이터의 오차 및 불안정 상태를 차단할 수 있는 장치의 보완이 필요할 것으로 보인다. 그리고 지자기 센서의 경우 좁은 범위의 측정에 추가하여 넓은 범위의 측정도 보완되어야 할 것으로 생각된다.

• 한국자동차공학회논문집
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• 제19권1호
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• pp.51-57
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• 2011

Information of the lateral velocity and the sideslip angle in a vehicle is very useful in many active vehicle safety applications such as yaw stability control and rollover prevention. Because cost-effective sensors to measure the lateral velocity and the sideslip angle are not available, reliable algorithms to estimation them are necessary. In this paper, a sliding mode observer is designed to estimate the lateral velocity. The side slip angle is estimated using the recursive least square with the disturbance observer and the pseudo integral. The estimated parameters from the combined estimation method are updated recursively to minimize the discrepancy between the model and the physical plant, and any possible effects caused by disturbances. The performance of the proposed monitoring system is evaluated through simulations and experiments.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.1102-1105
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• 2004

In this paper, the problem of a viewer's head tracking in a desktop-based interactive stereoscopic display system is considered. A fast and low-cost approach to the problem is important for such a computing environment. The system under consideration utilizes a shuttle glass for stereoscopic display. The proposed method makes use of an image taken from a single low-cost video camera. By using a simple feature extraction algorithm, the obtained points corresponding to the image of the user-worn shuttle glass are used to estimate the glass center, its local 'yaw' angle, as measured with respect to the glass center, and its global 'yaw' angle as measured with respect to the camera location. With these estimations, the stereoscopic image synthetic program utilizes those values to interactively adjust the two-view stereoscopic image pair as displayed on a computer screen. The adjustment is carried out such that the so-obtained stereoscopic picture, when viewed from a current user position, provides a close-to-real perspective and depth perception. However, because the algorithm and device used are designed for fast computation, the estimation is typically not precise enough to provide a flicker-free interactive viewing. An error concealment method is thus proposed to alleviate the problem. This concealment method should be sufficient for applications that do not require a high degree of visual realism and interaction.

• Wind and Structures
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• 제25권5호
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• pp.475-492
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• 2017

Inclined and yawed circular cylinder is an essential element in the widespread range of structures. As one of the applications, cables on bridges were reported to have the possibility of suffering a kind of large amplitude vibration called dry galloping. In order to have a detailed understanding of the aerodynamics related to dry galloping, this study carried out a set of wind tunnel tests for the inclined and yawed circular cylinders. The aerodynamic coefficients of circular cylinders with three surface configurations, including smooth, dimpled pattern and helical fillet are tested using the force balance under a wide range of inclination and yaw angles in the wind tunnel. The Reynolds number ranges from $2{\times}10^5$ to $7{\times}10^5$ during the test. The influence of turbulence intensity on the drag and lift coefficients is corrected. The effects of inclination angle yaw angle and surface configurations on the aerodynamic coefficients are discussed. Adopting the existed the quasi-steady model, the nondimensional aerodynamic damping parameters for the cylinders with three kinds of surface configurations are evaluated. It is found that surface with helical fillet or dimpled pattern have the potential to suppress the dry galloping, while the latter one is more effective.

• 한국자동차공학회논문집
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• 제11권6호
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• pp.197-204
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• 2003

This paper develops a computer model for estimating the handling of a cabover type large-sized truck. The truck is composed of front and rear suspension systems, a frame, a cab, and ten tires. The computer model is developed using ADAMS. A shock absorber, a rubber bush, and a leaf spring aunt a lot on the dynamic characteristic of the vehicle. Their stiffness and damping coefficient are measured and used as input data of the computer model. Leaf springs in the front and rear suspension systems are modeled by dividing them three links and joining them with joints. To improve the reliability of the developed computer model, the frame is considered as a flexible body. Thus, the frame is modeled by finite elements using MSC/PATRAN. A mode analysis is performed with the frame model using MSC/NASTRAN in order to link the frame model to the computer model. To verify the reliability of the developed computer model, a double lane change test is performed with an actual vehicle. In the double lane change, lateral acceleration, yaw rate, and roll angle are measured. Those test results are compared with the simulation results.

• International Journal of Aeronautical and Space Sciences
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• 제10권2호
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• pp.43-51
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• 2009

In the flight of air vehicles, accurate air data information is required to control them effectively. Especially, helicopters are often put in drastic motion involved with high angle of attacks in order to perform difficult missions. Among various sensors, the multi function probe (MFP) has been used in the present study mainly owing to its advantages in structural simplicity and capability of providing various information such as static and total pressure, speed, and pitch and yaw angles. In this study, a five-hole multi-function probe (FHMFP) is developed and its calibration is conducted using multiple regressions. In this work a calibration study on the FHMFP, an air data sensor for helicopters, is reported. It is shown that the pitch and yaw angles' accuracy of calibration is ${\pm}0.91^{\circ}$ at a cone angle of $0^{\circ}{\sim}30^{\circ}$ and ${\pm}2.0^{\circ}$ at $30^{\circ}{\sim}43^{\circ}$, respectively, which is summarized in table 3.