• 센서학회지
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• 제28권1호
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• pp.30-35
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• 2019

Inertial measurement units (IMUs) are widely used for wearable motion-capturing systems in the fields of biomechanics and robotics. When the IMUs are combined with optical motion sensors (hereafter, OPTs) for their complementary capabilities, it is necessary to align the coordinate system orientations between the IMU and OPT. In this study, we compare the application of two coordinate transformation-based orientation alignment methods between two coordinate systems. The first method (M1) applies angular velocity coordinate transformation, while the other method (M2) applies gyroscopic angle coordinate transformation. In M1 and M2, the angular velocities and angles, respectively, are acquired during random movement for a least-square algorithm to determine the alignment matrix between the two coordinate systems. The performance of each method is evaluated under various conditions according to the type of motion during measurement, number of data points, amount of noise, and the alignment matrix. The results show that M1 is free from drift errors, while drift errors are present in most cases where M2 is applied. Thus, this study indicates that M1 has a far superior performance than M2 for the alignment of IMU and OPT coordinate systems for motion analysis.

• 전기학회논문지
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• 제59권3호
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• pp.674-677
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• 2010

The purpose of this study was to analyze bradykinesia of forearm movement in patients with Parkinson's disease (PD) as compared to those of normal subjects. A gyrosensor was selected for the measurement of forearm movement, because it can provide angular velocity signal which is free from the gravitational artifact and also because it can be conveniently used during clinical test of bradykinesia. Forty PD patients (age: $65.7\pm11.1$ yrs, H&Y stage:$2.3\pm0.5$), 14 age-matched elderly subjects ($65\pm3.9$ yrs) and 17 healthy young subjects ($24\pm2.1$ yrs) participated in this study. Angular velocity during forearm movement of pronation/supination was measured in both arms. Suggested quantitative measures of bradykinesia were root-mean-squared (RMS) angular velocity, RMS angle, peak power and total power which were derived from the angular velocity. ANOVA showed that all measures were significantly different among three groups (p<0.001). Subsequent post-hoc test revealed that all measures in PD patients were significantly smaller than in healthy elderly and healthy young subjects (p<0.05). This results suggest that PD patients can be differentiated from normal subjects using suggested measures.

• 제어로봇시스템학회논문지
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• 제20권5호
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• pp.563-569
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• 2014

This article focuses on a hemispherical resonator gyro driven by the Coriolis effect. A hemispherical shell, called a resonator, is maintained in the resonance state by amplitude control and phase locking control. Parametric excitation has been used to control the amplitude. For rate measurement mode or FTR mode, nodal points have been kept to an amplitude of zero. Angular rate measurement has been demonstrated by rotating a resonator. Frequency mismatch between two stiffness principal axes is a major cause of low performance: vibrating pattern drift and reduced control effectiveness. This mismatch has been reduced significantly by the addition of small mass. A negative spring effect, which lowers resonance frequencies, has been verified experimentally.

• ETRI Journal
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• 제38권6호
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• pp.1031-1041
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• 2016

This paper presents millimeter-wave (mmWave) propagation characteristics and channel model parameters including path loss, delay, and angular properties based on 28 GHz and 38 GHz field measurement data. We conducted measurement campaigns in both outdoor and indoor at the best potential hotspots. In particular, the model parameters are compared to sub-6 GHz parameters, and system design issues are considered for mmWave 5G Giga communications. For path loss modeling, we derived parameters for both the close-in free space model and the alpha-beta-gamma model. For multipath models, we extracted delay and angular dispersion characteristics including clustering results.

• International Journal of Computer Science & Network Security
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• 제21권6호
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• pp.47-53
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• 2021

The article deals with the problems of application of microwave methods in systems of geoecological monitoring of natural environments and resources of the agro-industrial complex. It is noted that the methods of microwave radiometry make it possible, by the power of the measured intrinsic radio-thermal radiation of the atmosphere, when solving inverse problems using empirical and semi-empirical models, to determine such parameters of the atmosphere as thermodynamic temperature, humidity, water content, moisture content, precipitation intensity, and the presence of different fractions of clouds.In addition to assessing the meteorological parameters of the atmosphere and the geophysical parameters of the underlying surface based on the data of microwave radiometric measurements, it is possible to promptly detect and study pollution of both the atmosphere and the earth's surface. A technique has been developed for the analysis of sources of measurement error and their numerical evaluation, because they have a significant effect on the accuracy of solving inverse problems of reconstructing the values of the physical parameters of the probed media.To analyze the degree of influence of the limited spatial selectivity of the antenna of the microwave radiometric system on the measurement error, we calculated the relative measurement error of the ratio of radio brightness contrasts in two angular directions. It has been determined that in the system of geoecological monitoring of natural environments, the effect of background noise is maximal with small changes in the radiobrightness temperature during angular scanning and high sensitivity of the receiving equipment.

• 전자공학회논문지 IE
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• 제43권3호
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• pp.13-21
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• 2006

Ryu 등은 배열센서 출력을 이용하여 추정한 신호부공간으로부터 표적의 방위각 측정치를 구하고, 이를 이용하여 표적의 방위각 궤적을 추적하는 알고리즘을 제안하였다. Ryu 등이 제안한 방위각 추적 알고리즘은 별도의 데이터연관 필터가 필요 없으며 구조가 간단하다는 장점을 가지고 있다. Ryu의 방위각 추적 알고리즘에서는 신호부공간이 센서출력에 의해서 계속 쇄신되고 있지만 표본시간의 신호부공간에서 구한 측정치만을 사용하고 있으며, 신호대잡음비가 낮은 경우에는 Ryu 알고리즘의 추적 성능이 매우 급격히 저하되는 문제점을 가지고 있다. 본 논문에서는 Ryu 알고리즘의 방위각 추적 성능을 개선하기 위하여 표본시간의 신호부공간에서 구한 측정치뿐만 아니라 표본시간에 인접한 신호부공간으로부터 구한 측정치까지 사용할 수 있도록 ML(Maximum Lekelihood)에 기반을 둔 측정치 융합 기법을 제안한다. 그리고 제안한 측정치 융합 기법을 이용하여 Ryu 알고리즘과 같은 구조를 가지는 새로운 방위각 추적 알고리즘을 제안한다. 제안한 방위각 추적 알고리즘은 Ryu 알고리즘의 장점을 그대로 유지하면서 Ryu 알고리즘보다 향상된 추적 성능을 가진다.

• 전기학회논문지
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• 제60권10호
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• pp.1959-1965
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• 2011

Measuring the movement of joint angle of human body is very important clinically. Human joint angle displacement can be used to evaluate the degree of disease and disability. Also, we can determine the rehabilitation process with angular information. Conventional methods for measuring angular displacement are many weakness. The purpose of this study is to overcome the limitations of existing equipments by using optical method. For this reason, optical sensor system was used to correlate detected light signal with joint angle. Experimental results of the applied joint model in this study showed that joint angular displacement can be measured by optical signals. The suggested method is simple, durable, small, lightweight, convenient, and cost effective.

• Journal of the Optical Society of Korea
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• 제13권2호
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• pp.261-266
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• 2009

The angular dispersion-type non-scanning Fabry-Perot was applied to an ethanol-water mixture in order to investigate its acoustic properties such as the sound velocity and the absorption coefficient. The scattered light from the mixture was analyzed by using the charge-coupled-device area detector, which made the measurement time much shorter than that obtained by using the conventional scanning tandem multi-pass Fabry-Perot interferometer. The sound velocity showed a deviation from ultrasonic sound velocities at low temperatures accompanied by the increase in the absorption coefficient, indicating acoustic dispersion due to the coupling between the acoustic waves and some relaxation process. Based on a simplified viscoelastic theory, the temperature dependence of the relaxation time was obtained. The addition of water molecules to ethanol reduced the relaxation time, consistent with dielectric measurements. The present study showed that the angular dispersion-type Fabry-Perot interferometer combined with an area detector could be a very powerful tool in the real-time monitoring of the acoustic properties of condensed matter.

• 동력기계공학회지
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• 제13권1호
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• pp.33-38
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• 2009

In this study, the nose of cam in the automobile engine was modelled into circular disk to analyze the torsional vibration of the cam shaft. The distance between disks was fixed, but the diameter of disks was changed. The torsional vibration of the cam shaft was studied experimentally by the motion of the modelled disk with changing the disk diameter. And the sizes of the modelled disk were selected not to show the natural frequencies over all the experimental ranges. The torsional vibration meter used in this study has a laser system with non-contact measurement method, which can measure both torsional angular vibration velocity and torsional angular vibration displacement simultaneously. The Experimental analysis shows that the characteristics of the torsional vibration in the horizontal rotating shaft can be considerably affected by the arrangement of the modelled disks.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.541-546
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• 2005

Tracking control of an automatic pipe cutting robot (APCROMB) is studied. Using magnetic force APCROMB, which is designed and developed in Kyung Hee University, binds itself to the pipe and executes unmanned cutting process. The gravity effect on the movement of APCROMB varies as it rotates around the cylindrical pipe laid in the gravitational field. To maintain a constant velocity and consistent cutting performance against the varying gravitational effect, the authors adopt a multi-rate repetitive learning controller (MRLC), which learns the required effort to cancel the repetitive tracking errors caused by nonlinear effect. In addition to the varying gravity effect other types of nonlinear disturbances including backlash in the driving system and the slip between the wheels of APCROMB and the pipe also cause degradation in the cutting process. In order to identify those nonlinear disturbances the position estimation based on the encoder attached at the motor is not good enough. To identify the absolute angular position of APCROMB the authors propose the angular position estimation based on the signals from a MEMS-type two-axis accelerometer mounted on APCROMB. The tracking performances of APCROMB with a MRLC using the encoder-based position estimation is experimentally measured and results are shown. Also the difference between the encoder-based angular displacement measurement and the accelerometerbased angular displacement measurement is included.