• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.1140-1141
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• 2017

Depth of SWASH(Small Waterplane Area Single Hull) vessel which is an input value of its control system is measured by ultrasonic sensor. Distance to the its center of gravity can be simply calculated through ultrasonic sensor attached to the front of the vessel from the known values. However, it is to be calibrated with respect to its position for the accurate depth because it has geometric relation between the measurement value of ultrasonic sensor and the depth. In this research, depth calibration method of SWASH vessel using its position and ultrasonic sensor is introduced.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.12
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• pp.1086-1092
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• 2012

It has been studied for DGPS/INS(Differential Global Positioning System/Inertial Navigation System) to offer the more precise and reliable navigation data with the aviation industry development. The flight performance evaluation of navigation system is very significant because the reliability of navigation data directly affect the safety of aircraft. Especially, the high-level navigation system, as DGPS/INS, need more precise flight performance evaluation method. The performance analysis is performed by comparing between the DGPS/INS navigation data and reference trajectory which is more precise than DGPS/INS. The GPS receiver, which is capable of post-processed CDGPS(Carrier-phase DGPS) method, can be used as reference system. Generally, the DGPS/INS is estimated the CG(Center of Gravity) point of aircraft while the reference system is output the position of GPS antenna which is mounted on the outside of aircraft. For this reason, estimated error between DGPS/INS and reference system will include the error due to lever arm. In order to more precise performance evaluation, it is needed to compensate the lever arm. This paper presents procedure and result of flight test which includes lever arm compensation in order to verify reliability and performance of DGPS/INS more precisely.

• Radiation Oncology Journal
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• v.25 no.1
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• pp.54-61
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• 2007

[ $\underline{Purpose}$ ]: The purpose of this study is to develop a practical method for determining accurate marker positions for prostate cancer radiotherapy using CT images and kV x-ray images obtained from the use of the on- board imager (OBI). $\underline{Materials\;and\;Methods}$: Three gold seed markers were implanted into the reference position inside a prostate gland by a urologist. Multiple digital image processing techniques were used to determine seed marker position and the center-of-mass (COM) technique was employed to determine a representative reference seed marker position. A setup discrepancy can be estimated by comparing a computed $COM_{OBI}$ with the reference $COM_{CT}$. A proposed algorithm was applied to a seed phantom and to four prostate cancer patients with seed implants treated in our clinic. $\underline{Results}$: In the phantom study, the calculated $COM_{CT}$ and $COM_{OBI}$ agreed with $COM_{actual}$ within a millimeter. The algorithm also could localize each seed marker correctly and calculated $COM_{CT}$ and $COM_{OBI}$ for all CT and kV x-ray image sets, respectively. Discrepancies of setup errors between 2D-2D matching results using the OBI application and results using the proposed algorithm were less than one millimeter for each axis. The setup error of each patient was in the range of $0.1{\pm}2.7{\sim}1.8{\pm}6.6\;mm$ in the AP direction, $0.8{\pm}1.6{\sim}2.0{\pm}2.7\;mm$ in the SI direction and $-0.9{\pm}1.5{\sim}2.8{\pm}3.0\;mm$ in the lateral direction, even though the setup error was quite patient dependent. $\underline{Conclusion}$: As it took less than 10 seconds to evaluate a setup discrepancy, it can be helpful to reduce the setup correction time while minimizing subjective factors that may be user dependent. However, the on-line correction process should be integrated into the treatment machine control system for a more reliable procedure.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.1
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• pp.261-268
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• 2013

In this paper, we propose the algorithm that improves the linearity of the walking assistant robot on lateral slopes. The walking assistant robot goes out of the course due to the rotational moment which is caused by the weight of the robot and the slope. To compensate this, we give the weight to each driving axle after comparing the real rotational angular velocity with the target rotational angular velocity which is entered by an user. The results of applying the algorithm to the real walking assistant robot show that the yaw axis deviation of the robot without the algorithm diverges, but the yaw axis deviation of the robot with the algorithm lies within 20cm, which can be recognized as stable. In addition, the changing rate of the course deviation is stabilized and shows no more course deviation, after moving 300cm.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.6
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• pp.595-602
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• 2016

An automotive wheel bearing is important part that translates rotating motion and bears vehicle weight. Recently, in accordance with the demands for $CO_2$ emission reduction and fuel economy regulation, the requirements for the weight reduction and miniaturization of vehicles has increased. Therefore, life evaluation technology of the bearings has increased in necessity. Since the bearing life is affected by many parameters such as bearing geometry, bearing specifications, and vehicle specifications, it is difficult to predict. In this paper, the bearing life was tested by varying the applied load and rotation speed and comparing them with the basic rating life and modified rating life that were suggested in ISO standards. From the results, it was found that there was a difference between the test life and theoretical life and modified rating life than basic rating life was to be relatively well predicted by test life.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.8 no.3
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• pp.187-196
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• 2014

This paper suggests linearity enhancement algorithm to Ensure safety of Mobile Walker on Slope. Mobile Walker happens to get off track due to external forces from Walker's weight and the degree of the slope while slope driving. In order to compensate this, this research used the controller that estimates the external forces according to the slope of road surface and adjusts it to the motor output. Also, through comparisons between targeted rotational angular velocity which the user inputs and its velocity of the robot, algorithm was applied which applies a weight to each shaft. As a result of applying the proposed correction controller, it diverges in case of non-compensation experiments that deviates when moving, but it case of applying the ramp calibration algorithm, the deviation distance at max was within 10cm that it keeps safe driving, and change rate of deviation distance was also stabilized after 1m where no more changes occurred.

• Journal of the Korean Institute of Intelligent Systems
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• v.20 no.6
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• pp.793-798
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• 2010

In this paper we propose a low-power walking compensation method for biped robot based on consumption energy analysis. Firstly, basic walking motions that can reduce energy consumption of robot movements are implemented based on consumption energy analysis according to robot axes. We define knee bent motion as a basic walking motion. It can improve energy consumption and motion stability by lowering center of gravity of the biped robot. We analyze consumption energy of left and right leg of the robot using motor currents and propose a compensation method of walking motions to reduce unbalance of consumption energy between left leg and right leg. It can also improve energy consumption and walking stability of the robot. The proposed low-power compensation method based on consumption energy analysis is verified by walking experiments of a small biped robot with an embedded system.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.4
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• pp.380-388
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• 2023

This study estimates the metacentric height (GM) of a model ship by varying the transverse weight distribution, considering the effects of the roll period and moment of inertia, and compares it with the GM values measured by the inclining test. In the process, the relationship between the values is analyzed. Three types of ships-a 7-ton fishing vessel, 20-ton fishing vessel, and KRISO Very Large Crude-oil Carrier (KVLCC)-were used for the experiment and comparison. The roll period and moment of inertia were measured using the free roll decay and swing frame tests, and the GM was measured using inclining test. The estimated GM from the roll period and moment of inertia showed the same trend as the GM measured using the inclining test in the change of the weight distribution. However, the GM values measured using the inclining test were lower. Therefore, additional correction factors or parameters other than the roll period and moment of inertia are necessary for estimating GM. In the future, the relationship between the weight center and the estimated GM will be analyzed to derive the correction factors.

• Journal of Internet Computing and Services
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• v.11 no.4
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• pp.59-72
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• 2010

WIM(Weigh-In-Motion) is the system measuring the weight of the vehicle with a high-speed. In the existing WIM system, vehicle weight is measured based on the constant speed and the error ratio has 10%. However, because of measuring the driving pattern, that is abnormal driving pattern which is like the acceleration and down-shift of the drivers, it has the error ratio which is bigger than the real. In order to it reduces the error ratio of WIM system, the improved WIM system needs to find the abnormal driving pattern. In order to reducing the error ratio of these WIM systems, the improved WIM system can find abnormal driving patterns. In this paper, the improved WIM system which analyzes the abnormality driving pattern influencing on the error ratio of WIM system of an existing and minimizes the error span is designed. The improved WIM system has the multi step loop structure of adding the loop sensor to an existing system. In addition, the measure function defined as an intrinsic is improved and the weight measured by the abnormal driving pattern is amended. The analysis of experiment result improved WIM system can know the fact that the error span reduces by 8% less than in the existing the maximum average sampling error 22.98%.

• Journal of the KSME
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• v.29 no.2
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• pp.175-183
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• 1989

오늘날 널리 연구되고 있고 공학자들에게 많은 관심을 끌고있는 압전 세라믹(ceramic)을 이용 하여 자연계에서 일어나는 각종 진동현상을 측정하고 해석하기 위한 센서(sensor)의 설계, 제작은 이미 선진국에서도 보편화된지 오래이다. 특히 압전형 가속도계(piezo type accelerometer)는 진동의 절대 측정에 가장 유용한 센서로 널리 알려져 있다. (1) 아주 넓은 사용 주파수 범위 (2) 넓은 동적범위(dynamic range)에 걸친 뛰어난 선형성(linearity) (3) 측정된 가속도 신호를 전기적으로 적분하여 속도와 변위에 대한 자료 제공 용이 (4) 높은 정확성 (5) 자발 전(self-generating)이므로 외부 전원 공급이 불필요 (6) 수명과 뛰어난 내구성 (7) 작은 크기와 가벼운 무게 등이다. 현재 기계 구조물 진동 측정에 이용되고 있는 스트레인 게이지 형(strain gage-type)의 가속도계는 감도가 좋고 저주파 진동 측정에는 편리한 반면 충격이나 높은 주파수 전동 측정에는 적합하지 않으며 내부 구조가 다소 복잡하다(2). 반면에 압전형 가 속도계는 압전 소자와 관성 질량의 조합 설계로서 저주파 진동 측정에 적합한 고감도의 가속도 계와, 감도는 떨어지나 아주 높은 주파수 범위의 진동까지 측정이 가능한 가속도계를 손쉽게 설계, 제작할 수 있다. 본 글에서는 선진국에 비해 낙후된 국내의 센서 설계, 제작 기술을 고 양시키고자 최근 한국과학기술원에서 시도된 압전형 가속도계의 개발 연구 사례를 중심으로 설계 및 제작시 고려 사항과 보정 문제를 소개하고자 한다.