BLDC 모터의 비선형 마찰 모델 식별

장지영(Jiyoung Jang),허준서(Junseo Heo),좌동경(Dongkyoung Chwa) 대한전기학회 2021 대한전기학회 학술대회 논문집 Vol.2021 No.10

본 논문에서는 brushless direct current(BLDC) 모터의 정밀한 제어를 위해 비선형 마찰 모델인 Stribeck 모델을 이용하여 모터의 마찰력을 나타낸다. 비선형 마찰 모델을 포함하는 모터 운동 방정식의 파라미터를 Levenberg-Marquardt(LM) 알고리즘을 이용하여 식별한다. 본 논문에서는 실제 모터와 식별된 비선형 마찰 모델을 포함하는 시뮬레이션 모델이 얼마나 유사한지 검증하기 위해 실제 모터의 각속도 출력값과 시뮬레이션의 각속도 출력값을 비교한다.

원청기업 매출의존도에 따른 하청기업의 이익유연화 현상

장지영(Jiyoung Jang),이준호(Joonho Lee),권선국(Sunkook Kwon) 한국산업경영학회 2012 경영연구 Vol.27 No.3

본 연구의 목적은 자동차 산업에 속해 있는 하청기업 중 주문자위탁생산방식(OEM)으로 원청 기업에 제품을 공급하는 기업을 대상으로 원청기업 매출의존도에 따른 하청기업 이익유연화 정도를 검증하고자 한다. 연구 목적을 달성하기 위해 자동차 산업과 관련된 기업의 감사보고서를 검토하여 원청기업에 OEM 방식으로 제품을 납품하는 94개사를 대상으로 원청기업에 대한 매출의존도가 이익유연화에 어떠한 영향을 미치는지를 실증 분석하였다. 분석 결과, 하청기업의 원청기업 매출의존도가 기업 마다 상당한 차이를 보이는 것으로 나타났다. OEM 방식으로 제품을 납품 하더라도 의존도가 낮은 집단과 높은 집단 간 이익유연화 정도는 상당한 차이가 있었다. 즉, 원청기업에 대한 매출의존도가 높은 기업은 낮은 기업에 비해 상대적으로 더 많이 이익을 유연화하는 것으로 나타났다. 원청기업에 대한 매출의존도가 높은 집단과 OEM 방식으로 제품을 납품하지 않은 집단을 이용한 추가분석에서도 동일한 결과가 나타났다. 그러나 원청기업에 대한 매출의존도가 낮은 집단과 OEM 방식으로 제품을 납품하지 않은 집단 간 이익유연화 정도는 차이가 없었다. 전반적으로 하청기업은 원청기업의 압력으로부터 자유로울 수 없는 상황이나, 하청기업의 교섭력은 원청기업에 대한 매출의존도에 따라 상이할 것이다. 이로 인하여 하청기업은 원청기업에 대한 매출의존도에 따라 이익을 유연화하려는 정도가 상이한 것으로 나타났다. 본 연구는 하청기업의 회계처리에 대한 연구로 일화적 증거에 대한 실증적 근거를 제시하였다는 데 큰 의의가 있다. The purpose of this research is to examine income smoothing of subcontractors according to sales dependence on prime companies. This research examined audit reports of 94 companies in the automotive industry. The results show that subcontractors’ sales dependency on prime companies appeared to have significant differences in the degree of income smoothing between low dependence group and high dependence group. In other words, companies with high sales dependency on prime companies showed to have relatively higher income smoothing than companies with low dependency. In additional analysis comparing high sales dependency group on prime companies to the group that did not supplied on OEM basis showed the same result. However, there was no difference in income smoothing between group that had low sales dependency to the prime companies and group that did not supply products in OEM basis. Generally, subcontractors are not free from the pressures of prime companies, since the bargaining power of subcontractors differs according to the sales dependency on prime companies. As a result, subcontractors appeared to have different level in income smoothing depending on the sales dependency to prime companies. This research shows empirical evidence that the relationship between prime companies and subcontractors on the income smoothing of subcontractors.

전방향 이동로봇의 적분 슬라이딩 모드 제어 기반 고장 허용 비주얼 서보잉

장지영(Jiyoung Jang),좌동경(Dongkyoung Chwa) 대한전기학회 2022 정보 및 제어 심포지엄 논문집 Vol.2022 No.10

비선형 마찰 모델을 고려한 BLDC 모터의 적분 슬라이딩 모드 제어

장지영(JiYoung Jang),허준서(Junseo Heo),좌동경(Dongkyoung Chwa) 대한전기학회 2022 전기학회논문지 Vol.71 No.1

This paper proposes an integral sliding mode control method for robust control of brushless direct current (BLDC) motor. In order to improve the control performance, the friction force of the motor is expressed using the Stribeck friction model, which is a nonlinear friction model that can accurately represent the friction force at low speed. The parameter values required to design the integral sliding mode controller are then obtained by identifying the parameters of the dynamic equations of the motor including the nonlinear friction model using the Levenberg-Marquardt (LM) algorithm. The performance of the proposed integral sliding mode control method for the BLDC motor is verified through both the simulation results and the actual motor speed control test results.

VRF 시스템의 고효율 부하대응 열교환기 가변유로 기술에 관한 연구

장지영(JiYoung Jang),송치우(ChiWoo Song),윤필현(PhilHyun Yoon),사용철(YongCheol Sa) 대한설비공학회 2022 대한설비공학회 학술발표대회논문집 Vol.2022 No.6

In this study, the latest heat exchanger technology to improve the performance of the VRF system is introduced. The heat exchanger is a key component in VRF system performance and in order to respond effectively to various loads, a technology has been developed that divides the heat exchanger into three passages through valve control and realizes optimal load-response operation by changing the flow passage. This technology enables bypass operation to respond to a small load under heating overload conditions, and prevents freezing of the lower end of the heat exchanger to supply continuous heating operation. In addition, it was possible to increase the operating efficiency by about 20% by changing the heat exchanger flow path during cooling and heating operation.

BLDC 모터의 비선형 마찰 모델 식별

장지영(Jiyoung Jang),허준서(Junseo Heo),좌동경(Dongkyoung Chwa) 대한전기학회 2021 정보 및 제어 심포지엄 논문집 Vol.2021 No.10

VRF 시스템의 고효율 부하대응 열교환기 가변유로 기술에 관한 연구

장지영(JiYoung Jang),송치우(ChiWoo Song),윤필현(PhilHyun Yoon),사용철(YongCheol Sa) 대한설비공학회 2022 대한설비공학회 학술발표대회논문집 Vol.2022 No.6

In this study, the latest heat exchanger technology to improve the performance of the VRF system is introduced. The heat exchanger is a key component in VRF system performance and in order to respond effectively to various loads, a technology has been developed that divides the heat exchanger into three passages through valve control and realizes optimal load-response operation by changing the flow passage. This technology enables bypass operation to respond to a small load under heating overload conditions, and prevents freezing of the lower end of the heat exchanger to supply continuous heating operation. In addition, it was possible to increase the operating efficiency by about 20% by changing the heat exchanger flow path during cooling and heating operation.

Multiple arc FSRT와 Conformal FSRT의 DVH 비교

김기환,김준상,장지영,김재성,김성호,송창준,박민규,존문준,Kim Ki-Hwan,Kim Jun-Sang,Jang JiYoung,Kim Jae-Sung,Kim Seong-Ho,Song Chang-Joon,Park Min-Kyu,Cho Moon-June 대한방사선종양학회 1999 Radiation Oncology Journal Vol.17 No.3

목적 : Multiple arc FSRT (fractionated stereotactic radiotherapy)와 conformal FSRT의 치료계획에 있어서 종양의 모양과 DVH (dose volume histogram)를 비교하여 두 기법간의 유용성에 대하여 논하고자 한다. 대상 및 방법 : 16명의 뇌종양 환자들을 대상으로 1997년 8월부터 1998년 12월까지 충남대학교병원 치료방사선과에서 112회의 FSRT를 실시하였다. 치료 전 모의치료에서 얻은 AP(Anterior-posterior), Lateral 필름상의 금속표지자의 좌표값을 ISOLOC프로그램에 입력하여 얻은 기준점과의 오차를 확인한 후 치료계획을 하였다. 치료계획은 종양용적과 종양표면적를 계산한 후 if (Irregular factor)를 고려하여 multiple arc FSRT 혹은 conformal FSRT를 선택하였다. Multiple arc FSRT는 종양의 IF값이 1-1.2인 경우에 고려하였고, conformal FSRT는 IF값이 1.3 이상인 경우에 고려한 후 종양용적에 대하여 처방선량 이상의 선량에 대한 DVH곡선에 의한 면적이 최소이면서 처방선량 이하의 선량에 대한 DVH곡선에 의한 면적이 최대가 되도록 하는 치료계획을 선택하여 평가하였다. 결과 : 치료전 모의치료에서 시행한 금속표지자의 좌표값을 ISOLOC프로그램에 입력하여 얻은 기준점과의 오차는 1 mm 이내였다. Huitlple arc FSRT는 누적DVH상에서 처방선량의 90, 91, 92, $93\%$에서 전체 종양용적을 포함하고 있었으며 평균값은 $90.6\%$이었고, conformal FSRT 는 누적DVH상에서 처방선량의 81, 85, 86, 87, $91\%$에서 전체 종양용적을 포함하고 있었으며 평균값은 $8\%$이었다. 두 방식 모두 결정장기들에는 최대선량의 $5\%$이하의 적은 선량이 조사되었다. 결론 : Multiple arc FSRT와 conformal FSRT를 IF를 기준으로 치료 계획하여 구형의 종양에 multiple arc FSRT를 시행하였으며, 불규칙한 모양의 종양에는 conformal FSRT를 시행하여 종양의 모양에 관계없이 적절한 FSRT치료계획을 수립할 수 있었다. Purpose : In FSRT (Fractionated stereotactic radiotherapy) planning, we studied the usefulness between multiple arc FSRT and conformal FSRT by comparing tumor shape and DVH (dose volume histogram). Materials and Methods In Chungnam Univ. hospital, we had treated the sixteen patients with FSRT from Aug. 1997 to Dec. 1998. In choosing multiple arc FSRT or conformal FSRT, we had considered If (irregular factor) after calculating tumor volume and surface area. We had considered multiple arc FSRT if tumor shape was similar to sphere or the value of If was less than 1.25, conformal FSRT if tumor shape was very irregular or If was more than 1.3. For evaluation of treatment planning, we had considered the appropriate DVH for tumor volume and for critical organs. Results : The errors between reference point and the coordinates point on AP, Lat radiography were less than 1 mm before treatment. We had planned $3\~$5 arcs for multiple arc FSRT, $5\~6$ports for conformal FSRT. The mean dose distribution of tumor volume of cumulative DVH between multiple arc FSRT and conformal FSRT was 90.6, 85%, respectively. The dose of critical organs irradiated was less than $5\%$ maximum dose of cumulative DVH. Conclusion : We had obtained the similar value between multiple arc FSRT and conformal FSRT, so that we had appropriate treatment planning of FSRT for multiple arc FSRT and conformal FSRT according to tumor shape and size.

환경유래 식품오염물질의 우선순위 선정 기법 (Food-CRS-Korea)의 개발과 적용

양지연(Jiyeon Yang),장지영(Jiyoung Jang),김수환(Soohwaun Kim),김윤관(Yoonkwan Kim),이효민(Hyomin Lee),신동천(Dong-Chun Shin),임영욱(Youngwook Lim) 환경독성보건학회 2010 환경독성보건학회지 Vol.25 No.1

The aims of this study were to develop the suitable system software in chemical ranking and scoring (CRS) for the food hazardous chemicals associated with environmental emission and to suggest the priority lists of food contamination by environmental-origined pollutants. Study materials were selected with reference to the priority pollutants list for environment and food management from domestic and foreign research and the number of study materials is 103 pollutants (18 heavy metals, 10 PBTs, 10 EDs, and 65 organic compounds). The Food-CRS-Korea system consisted of the environmental fate model via multimedia, transfer environment to food model, and health risk assessment by contaminated food intake. We have established that health risks of excess cancer risks, hazard quotients (HQs) by chronic toxicity and HQs by reproductive toxicity convert to score, respectively. The creditable scoring system was designed to consider uncertainty of quantitative risk assessment based on VOl (Value-Of-Information). The predictability of the Food-CRS-Korea model was evaluated by comparing the presumable values and the measured ones of the environmental media and foodstuffs. The priority lists based on emissions with background-level-correction are 15 pollutants such as arsenic, cadmium, and etc. The priority lists based on environmental monitoring date are 17 pollutants including DEHP, TCDD, and so on. Consequently, we suggested the priority lists of 13 pollutants by considering the several emis-sion and exposure scenarios. According to the Food-CRS-Korea system, arsenics, cadmium, chromes, DEHP, leads, and nickels have high health risk rates and reliable grades.

파이썬을 활용한 온라인 기반 프로젝트의 집중학기제 운영사례 : S 여대를 중심으로

권선아(Kyun, Suna),장지영(Jang, Jiyoung) 한국공학교육학회 2021 공학교육연구 Vol.24 No.5

This study deals with the case of online-based project learning, which was designed for the purpose of university educational innovation and enhancing learners’ competencies required by society, operated during the COVID-19 pandemic. The course was applied Python programming language, team-based project learning, and intensive course system, which is required by our society and companies in the era of the 4th industrial revolution. Also it was operated as a non-face-to-face online class, which would have been operated in an offline class if it had not been for Covid 19 pandemic, to explore the possibilities and educational effects of online learning. To do this, 32 university students participated in online-based project learning during 8 weeks, and then conducted a survey. The survey results were analyzed in terms of i) non-face-to-face online learning, ii) team-based project learning, and iii) application of the intensive course system. Results say that most of the learners were satisfied with the online learning, team-based project learning, and the intensive semester system applied in this course at a high level, and also they clearly presented the reasons. Thereby, it has been confirmed that the learners were already well aware of the pros and cons of each learning method. Based on these results, the implications were discussed.