• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.4
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• pp.301-309
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• 2021

Pulse count method is the classical reaction wheel speed detection method. In this study, we represent the pulse count method as mathematical equations. Instead of rotation speed, we model the reaction wheel rotation through rotation angle during sampling periods. We verified the effectiveness of the proposed model by comparing the pulse counts variation and averaging method effects from the model and previous research results. Then, we add tacho pulse non-uniformity to this verified model, and examine the errors of pulse count method. We express the measurement error increasement due to non-uniformity as mathematical equations, and also shows the requirement of moving average numbers to offset the measurement errors.

• Journal of Astronomy and Space Sciences
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• v.25 no.4
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• pp.481-490
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• 2008

Reaction wheel is one of the actuators for spacecraft attitude control, which generates torque by changing an inertial rotor speed inside of the wheel. In order to generate required torque accurately and estimate an accurate angular momentum, wheel speed should be measured as close to the actual speed as possible. In this study, two conventional speed detection methods for high speed motor with digital tacho pulse (Elapsed-time method and Pulse-count method) and their resolutions are analyzed. For satellite attitude maneuvering and control, reaction wheel shall be operated in bi directional and low speed operation is sometimes needed for emergency case. Thus the bias error at low speed with constant acceleration (or deceleration) is also analysed. As a result, the speed detection error of elapsed-time method is largely influenced upon the high-speed clock frequency at high speed and largely effected on the number of tacho pulses used in elapsed time calculation at low speed, respectively.

• Aerospace Engineering and Technology
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• v.8 no.2
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• pp.92-97
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• 2009

Two conventional speed detection methods (Elapsed-time method and Pulse-count method) are analyzed and compared for a high speed motor with digital tacho pulse with non-uniformity. In general, the elapsed-time method usually has better performance than a pulse-count method in case sufficiently high speed clock is used to measure the time difference. But if a tacho pulse non-uniformity exists in the reaction wheel - most of reaction wheel has a certain amount of non-uniformity - the accuracy of the elapsed-time method is degraded significantly. Thus the performance degradation is analyzed with respect to the level of non-uniformity of tacho pulse distribution and an allowable bound is suggested.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.5
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• pp.69-76
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• 1995

This paper describes characteristics of EDT(Electro Discharge Texturing) and that the strip surface has influence on the paintability. The pulse mode and the capacitor mode of recently developed EDT method were investigated about the peak shape and the roughness of strip surface. And EDT method compared the above-mentioned contents with the SBT(Shot Blast Texturing) method. The peak count of the pulse mode is more than that of the capacitor mode. But the lower roughness below the Ra 3.2 .mu. m of the strip surface, the texturing time of the pulse mode is longer than the capacitor mode. In SBT method, the peak shape is similar to capacitor mode. But the EDT roll has more uniformity than the SBT roll and has more peak count than that of SBT roll. Therefore, in the painted steel sheet, EDT roll gives better surface of clarity image than the SBT roll.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 1989.10a
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• pp.65-70
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• 1989

This paper presents resarch results on the use of a corona detector and a pulse counter in order to diagnose for oil transformers. Using these experimental apparatus, tests were carried out on a typical transformer oil containing different carbonized paper and various moisture contents to measure the picocoulomb val-ues and pulse count. Through the result of this study it was found that the picocoulomb values and pulse count of corona were depended on the getting stained in transformer oil. The amplitude of the partial discharge amount and the number of pulse were decreased up to 70 [。c] and then was increased as the oil temperature goes up. It was concluded that the determinati-on level for diagnosis of oil transform-er was taken into account the temperatu-er of transformer oil, The use of pulse counter method, which have been taken the same property of voltage and temperature variation for the corona measurement mothod, considera-bly increase insulator avilability.

• Nuclear Engineering and Technology
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• v.55 no.12
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• pp.4350-4356
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• 2023

Radiation detection systems working at high count rates suffer from the overlapping of their output electric pulses, known as pulse pile-up phenomenon, resulting in spectrum distortion and degradation of the energy resolution. Pulse tail extrapolation is a pile-up correction method which tries to restore the shifted baseline of a piled-up pulse by extrapolating the overlapped part of its preceding pulse. This needs a mathematical model which is almost always nonlinear, fitted usually by a nonlinear least squares (NLS) technique. NLS is an iterative, potentially time-consuming method. The main idea of the present study is to replace the NLS technique by an integration-based non-iterative method (NIM) for pulse tail extrapolation by an exponential model. The idea of linear extrapolation, as another non-iterative method, is also investigated. Analysis of experimental data of a NaI(Tl) radiation detector shows that the proposed non-iterative method is able to provide a corrected spectrum quite similar with the NLS method, with a dramatically reduced computation time and complexity of the algorithm. The linear extrapolation approach suffers from a poor energy resolution and throughput rate in comparison with NIM and NLS techniques, but provides the shortest computation time.

• Journal of Institute of Control, Robotics and Systems
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• v.21 no.6
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• pp.577-582
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• 2015

This paper proposes an efficient detection of absolute position of a robot joint using two incremental encoders. We considers a robot joint comprising a motor, a reducer, two encoders, and a motor drive. An incremental(first) encoder provides motor's rotor position or input position of reducer while another incremental(second) encoder does output position of the reducer. A table is made where the relationship between the first and the second encoder counts is recorded. The key point is placed where the table is constructed: when a pulse occurs in the second encoder, there exists a corresponding unique count value of the first encoder. The absolute position is detected using the table by searching the second encoder position corresponding to the first encoder count value when a pulse occurs in the second encoder. The proposed method needs a small rotation, as just one second encoder's pulse angle, for the initial absolute position detection.

• Nuclear Engineering and Technology
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• v.52 no.5
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• pp.1029-1035
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• 2020

The detector suffers from pulse pileup by overlapping of the signals when it was used in high radiation fields. The pulse pileup deteriorates the energy spectrum and causes count losses due to random co-incidences, which might not resolve within the resolving time of the detection system. In this study, it is aimed to propose a new pulse pileup correction method. The proposed method is to correct the start point of the pileup pulse. The parameters are obtained from the fitted exponential curve using the peak point of the previous pulse and the start point of the pileup pulse. The amplitude at the corrected start point of the pileup pulse can be estimated by the peak time of the pileup pulse. The system is composed of a NaI (Tl) scintillation crystal, a photomultiplier tube, and an oscilloscope. A 61 μCi ¹³⁷Cs check-source was placed at a distance of 3 cm, 5 cm, and 10 cm, respectively. The gamma energy spectra for the radioisotope of ¹³⁷Cs were obtained to verify the proposed method. As a result, the correction of the pulse pileup through the proposed method shows a remarkable improvement of FWHM at 662 keV by 29, 39, and 7%, respectively.

• Nuclear Engineering and Technology
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• v.56 no.1
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• pp.56-63
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• 2024

In high radiation fields, gamma cameras suffer from pulse pile-up, resulting in poor energy resolution, count losses, and image distortion. To overcome this problem, various methods have been introduced to reduce the size of the aperture or pixel, reject the pile-up events, and correct the pile-up events, but these technologies have limitations in terms of mechanical design and real-time processing. The purpose of this study is to develop a real-time gamma camera to evaluate the radioactive contamination in high radiation fields. The gamma camera is composed of a pinhole collimator, NaI(Tl) scintillator, position sensitive photomultiplier (PSPMT), signal processing board, and data acquisition (DAQ). The pulse pile-up is corrected in real-time with a field programmable gate array (FPGA) using the start time correction (STC) method. The STC method corrects the amplitude of the pile-up event by correcting the time at the start point of the pile-up event. The performance of the gamma camera was evaluated using a high dose rate ¹³⁷Cs source. For pulse pile-up ratios (PPRs) of 0.45 and 0.30, the energy resolution improved by 61.5 and 20.3%, respectively. In addition, the image artifacts in the ¹³⁷Cs radioisotope image due to pile-up were reduced.

• Journal of Korean Medical classics
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• v.20 no.4
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• pp.17-35
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• 2007

Objectives : To consider same or not the positions of acupoints on the meridian in the old acupuncture books. Methods: On the basis of old acu-books, We count the number of acupoints that are on pulse. Thru the three books-"Yijongkumkam(醫宗金鑑)","Chimkuhak 1st(鍼灸學-上)", Kyunghyulhakchongseo(經穴學叢書)"-We Compared the way of positioning of acupoints, also did on the location of acupoints, vein, vascular system, around the acupoints, based on the anatomical structures(esp. artery) Results : On the basis of old acu-books, the number of acupoints(only in the twelve meridian) on the pulse is 35, and the number of points not in the old books but on the pulse is 6, sum is 41 points. Comparion from Sambukuhu consultation method(三部九候診法) in "Somun(素問)", Some points, Taeyang(太陽, not in the twelve meridian), Yimun(耳門) and Koryo(Yimun and Koryo are in) are on pulse. Like Chonbu(天府) and Hyupbaek(俠白), We can feel the pulse on ulna side of biceps muscle, noton radial side. Shikdu(食竇) was described as on pulse in the "Chimkushimbopyokyul(鍼灸心法要訣)", but we could hardly feel it. Conclusions : It'll be right to add the Yimun(耳門) and Koryo to the points on pulse, of course two points are not in the twelve meridian. We must take the points Chonbu(天府) and Hyupbaek(俠白), on ulna side of biceps muscle. Shikdu(食竇) must be excepted, because we cannot feel the pulse in consultation.