• Proceedings of the Korea Information Processing Society Conference
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• 2022.11a
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• pp.600-602
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• 2022

2차원 이미지 또는 영상을 통한 자세 추정의 경우, 영상 내에서 발생할 수 있는 탐지 오류, 피사체 잘림, 폐색(Occlusion) 등으로 인해 자세 추정 정확도가 감소할 수 있다. 본 논문에서는 4장 이상의 다양한 각도로 촬영한 이미지를 NeRF(Neural Radiance Fields)를 통해 이미지 합성(Image synthesis)을 진행하여 3차원 모델을 생성한다. 이후 DeepLabCut을 사용하여 관절 좌표와 골격(Skeleton)을 구축한다. 구축한 골격을 인공지능에 학습시킨 뒤 2차원 영상에서의 관절 좌표 인식, 골격 구축, 자세 추정을 진행한다. 2차원 영상 테스트 데이터를 통해, 3차원 모델을 사전 학습한 인공지능 모델과 기존 2차원 이미지를 사용하여 학습한 인공지능 모델의 자세 추정 정확도를 비교한다.

• Journal of the Korean Society of Radiology
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• v.5 no.5
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• pp.277-282
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• 2011

When we keep sitting for a long time, we end up with pain due to changes in the curvature in the waist. This study examined impacts from the wearing of a SPINE-GUARD(belt for the waist stabilization) on a cross-legged sit on variations of the Cobb's angle, lower back pain and trunk flexion angle. 15 men for the examination have watched movies or attended lectures while wearing a belt for 90 minutes per round for every five rounds for two weeks. The Cobb's angle showed a significant decrease from $48.36{\pm}14.57$ before wearing to $28.09{\pm}11.63$ after wearing (p<0.05). Pain decreased from $4.53{\pm}2.36$ before wearing to $2.733{\pm}2.153$ after wearing (p<0.05). The trunk flexion angle also showed a significant decrease from $82.33{\pm}20.30$ before wearing to $70.2{\pm}19.43$ after wearing (p<0.05). Given these findings, the wearing of a SPINE-GUARD seems to affect variations of the Cobb's angle and trunk flexion angle, and decrease of lower back pain.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.33 no.2
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• pp.131-142
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• 2015

In order to support the development of a cost-effective river bathymetric system, this research has focused on modeling GPS observables, which are obtained by array of five single-frequency receivers (i.e., two references and three rovers) to estimate the high accurate kinematic position, and the surveying vessel altitude. Also, by applying all GPS measurements as multiple-baselines with constraining rover baselines, we derived the socalled ‘kinematic network model.’ From the model, the integer-constrained least-squares (LS) for position estimation and the implicit LS for attitude determination were implemented, while a series of simulation tests with respect to the baseline lengths around 2km performed to demonstrate its accuracy analysis. The on-the-fly (OTF) ambiguity resolution tests revealed that ninety-nine percents of time-to-fix-first ambiguity (TTFF) can be decided in less than two seconds, when the positioning accuracy of ambiguity-fixed solutions was assessed as the greater than or equal to one and two centimeters in horizontal and vertical, respectively. Comparing to the GPS-derived attitudes, the achievable accuracy gradually descended in sequence of yaw, pitch and roll due to the antenna geometric configuration. Furthermore, the RMSE values for the baseline lengths of three to six meters were within ±1′for yaw, and less than ±10′and ±20′for pitch and roll, respectively, but those of between six to fifteen meters were less than ±1′for yaw, ±5′for pitch, and ±10′for roll.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.6 no.2
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• pp.55-62
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• 2012

In this paper we propose a control system to preserve the interior angle between back section and upper leg section to be larger than 90 degrees using a single limit switch. To design the control system we analyze the kinematics of actuation mechanisms for the back section and the upper leg section, and find out an optimal solution for the controller design. Using a prototype control system we perform experiments to test the controller performance, and show that the interior angle between the back section and the upper leg section is always preserved larger than 90 degree. From the experimental results, we show the proposed control system is feasible to keep the body posture stability.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.8
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• pp.619-626
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• 2017

In this work, the effect of attitude angle variation on drag coefficients of hemisphere in a Mach 6 flow has been investigated. Experiments were conducted in a shock tunnel and a free-falling technique was used to minimize flow disturbance by a sting. For attitude and drag coefficient measurements of a free-falling hemisphere, a free-falling technique based on a releasing mechanism with a stair-typed module and an electromagnet was developed. A shadowgraph technique was used for flow visualization using a high-speed camera.

• Journal of Astronomy and Space Sciences
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• v.16 no.1
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• pp.69-78
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• 1999

We have developed an attitude sensing S/W system, one of modules of Mission Analysis System(MAS), which simulates attitude sensing data as almost the same as the real sensor of a satellite in orbit. When attitude elements($alpha,delta$) of a satellite and positions of Earth, Moon, and Sun are given, the S/W system calculates look angles and dihedral angles of each celestial bodies relative to the rotations axis of the satellite. It consists of two sub-modules : One is ephemeris service module which consider the perturbations of four planets(Venus, Mars, Jupiter, Saturn) for positions of Sun and Moon and 4 $\times$4 earth gravitational potential terms for a satellite's position. The other is attitude simulation module which generates attitude sensing data. Varying the rotational axis of a satellite and it's orbital elements, we simulated the generating attitude sensing data with this S/W system and discussed their results.

• Journal of the Korean Institute of Intelligent Systems
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• v.20 no.5
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• pp.677-682
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• 2010

This paper addresses a method of estimating roughly the human pose by comparing Haar-wavelet value which is learned in face detection technology using AdaBoost algorithm. We also presents its application to face recognition. The learned weak classifier is used to a Haar-wavelet robust to each pose's feature by comparing the coefficients during the process of face detection. The Mahalanobis distance is used to measure the matching degree in Haar-wavelet selection. When a facial image is detected using the selected Haar-wavelet, the pose is estimated. The proposed pose estimation can be used to improve face recognition speed. Experiments are conducted to evaluate the performance of the proposed method for pose estimation.

• Proceedings of the Korea Information Processing Society Conference
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• 2015.10a
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• pp.1372-1374
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• 2015

본 논문에서는 농구 경기에서의 대표적 자세 중 Standing shoot, Jump shoot, Pass, Dribble, Lay-up shoot, 총 5가지 자세를 인식하기 위해 각 자세와 3축 가속도 값과의 상관관계를 보여주고 있다. 스마트폰에 내장되어 있는 가속도 센서로부터 데이터를 생성해주는 어플리케이션인 Sensor log를 활용하여 얻은 3축 가속도 값으로 수직, 수평축과 3축 가속도의 크기를 구해 Instance로 사용하였다. 위 데이터는 대표적인 데이터 마이닝 도구인 Weka tool을 이용하여 각 모션과 데이터 값의 상관관계를 확인하였고, 실험 결과 10-fold에서 평균 59.8%를 보였으나 Training set과 Test set의 결과 80.8%를 보였다.

• The korean journal of orthodontics
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• v.35 no.5 s.112
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• pp.341-350
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• 2005

The Purpose of this study was to compare the degree of vortical head rotation and to evaluate the reproducibility of natural Head posture (NHP) according to two guiding methods, the head posture aligner (HPA) method and the solf balance posture (SBP) method. The subjects consisted of 30 adults. On the first day. lateral and frontal cephalometric radiographs were obtained through the two guiding methods. One mouth later. lateral and frontal cephalometric radiographs were obtained again through both guiding methods. The degrees of vertical head rotation of both guiding methods were compared and the reproducibility was evaluated for each guiding method. A comparison of the degrees of vortical head rotation for the two methods revealed that the vertical head posture was lower in the SBP method than in the HPA method by an average of $2.79^{\circ}$. All measurements obtained using the HPA and SBP methods with a time interval of one north did not show any significant difierence in lateral and frortal cephalometric radiographs. The results of the present study suggest that the SBP method may be used as an alternative to the HPA method in case the HPA method can not be applied.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.5
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• pp.517-526
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• 2015

This paper presents the results of study for improving the reliability of quadrotor attitude control by applying a multi-sensor along with a data fusion algorithm. First, a mathematical model of the quadrotor dynamics was developed. Then, using the quadrotor mathematical model, simulations were performed using the improved reliability multi-sensor data as the inputs. From the simulation results, we designed a Gimbal-equipped quadrotor system. With the quadrotor in a hover state, we performed experiments according to the angle change of the user's specifications. We then calculated the attitude control data from the actual experimental data. Furthermore, with additional simulations, we verified the performance of the designed quadrotor attitude control system with multiple sensors.