http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
김연수(Y. S. Kim),이대현(D. H. Lee),김용주(Y. J. Kim),정선옥(S. O. Chung),김태형(T. H. Kim),최창현(C. H. Choi) 유공압건설기계학회 2015 유공압건설기계학회 학술대회논문집 Vol.2015 No.10
This research is conducted to develop automatic steering system for unmanned agricultural machine developing, and performance of the system was evaluated by parallel parking of conventional vehicle. The automatic steering system consist MDPS (motor drivven power steering) to control steering, ESC (electronic stability control) to acquire wheel speed, ultrasonic sensor to recognize parking space, and controller to communicate and handle data. Parallel parking process using automatic steering control consist parking space recognition, backward path generation, and steering control for path tracking. To recognize parking space length and width of parking space were measured using ultrasonic sensor and calculated traveling distance. The path for parallel parking was generated based on kinematic model of conventional vehicle, and PI controller was used to control steering angle for path tracking. Parallel parking simulation was conducted to determine minimum speed of steering angle control, because too low speed of steering angle control increase error of vehicle position and too high speed of steering angle control has cause MDPS slip. The result of the simulation was that 500 °/s of control speed was selected as minimum speed of steering angle. In order to evaluate performance of the automatic steering system tests for performance evaluation of parking space recognition, position control of steering angle, parallel parking were conducted. The results of performance evaluation test were that measured area of parking space using ultrasonic sensor was smaller than the actual are in every case and standard error became larger when the speed of the car was faster. The performance of the position control of steering angle was that maximum overshoot increased if the speed and steering angle increased when checking at angles of 60, 120 and 180. Delay time was 0.3 seconds with fix time of 2 seconds was measure and the rate of error was mostly below 1% which showed outstanding performance. However, when measuring at 240 degree, the slip of MDPS occurred which caused no result to show. Parallel parking using automatic steering control was conducted by vehicle speed condition, the results show that the errors on x-axis and y-axis were below 0.54 m and 0.14 m, respectively, and error on steering angle was less than 1°; therefore it is possible that parallel parking using automatic steering control system for conventional vehicle.
논문 : 노외기계시스템공학 ; 농업용 트랙터의 주요 농작업 소요동력 분석
김용주 ( Y. J. Kim ),정선옥 ( S. O. Chung ),박승제 ( S. J. Park ),최창현 ( C. H. Choi ) 한국농업기계학회 2011 바이오시스템공학 Vol.36 No.2
The purpose of this study was to analyze power requirement of an agricultural tractor by major field operations. First a survey was conducted to obtain annual usage ratio of agricultural tractor by field operation. Plowing, rotary tillage, and loader operations were selected as major field operations of agricultural tractor. Second, a power measurement system was constructed with strain-gauge sensors to measure torque of four driving axles and a PTO axle, speed sensors to measure rotational speed of the driving axles and an engine shaft, pressure sensors to measure pressure of hydraulic pumps, an I/O interface to acquire the sensor signals, and an embedded system to calculate power requirement. Third, the major field operations were experimented under fields with different soil conditions following planned operation paths. Power requirement was analyzed during the total operation period consisted of actual operation period (plowing, rotary tillage, and loader operations) and period before and after the actual operation (3-point hitch operating, forward and reverse driving, braking, and steering). Power requirement of tractor major components such as driving axle part, PTO part, main hydraulic part, and auxiliary hydraulic part were measured and calculated to determine usage ratio of agricultural tractor power. Results of averaged power requirement for actual field operation and total operation were 23.1 and 17.5 kW, 24.6 and 19.1 kW, and 14.9 and 8.9 kW, respectively, for plowing, rotary tillage, and loader operations. The results showed that rotary tillage required the greatest power among the operations. Averaged power requirement of driving axles, PTO axle, main hydraulic part, and auxiliary part during the actual field operation were 8.1, 7.8, 3.4, and 1.5 kW, respectively, and the total requirement power was about 70% (20.8 kW) of the rated power. Averaged power requirement of driving axles, PTO axle, main hydraulic, and auxiliary hydraulic for the total operation period were 6.5, 6.0, 2.1, 0.9 kW, respectively, and total requirement power was about 52% (15.5 kW) of the rated power. Driving axles required the greatest amount of power among the components.
논문 : 노외기계시스템공학 ; 로타리 경운작업 시 트랙터 PTO 가혹도 평가
김용주 ( Y. J. Kim ),정선옥 ( S. O. Chung ),최창현 ( C. H. Choi ),이대현 ( D. H. Lee ) 한국농업기계학회 2011 바이오시스템공학 Vol.36 No.3
Analysis of load on major parts of the tractor power drive line is critical for efficient and optimum design of a tractor. The purpose of this study was to evaluate severeness of the tractor PTO driving axle during rotary tillage operation. First, S-N (stress vs. number of cycle) curve of a PTO driving gear was obtained through the fatigue life test using a PTO dynamometer. Second, PTO severeness was evaluated during rotary tillage operation. Torque measurement system was constructed with strain-gauge sensors to measure torque of a PTO axle, an I/O interface to acquire the sensor signals, and an embedded system to calculate severeness. The severeness of PTO was analyzed using measured torque data during rotary tillage. In the PTO gear life fatigue test, breakage time and bending stress of the gear were measured by tooth widths and torque change during the fatigue life test. The S-N curve showed a good linear relationship between bending stress and number of cycle (life) with a coefficient of determination of 0.97. For PTO severenss evaluation, rotary tillage operations were conducted at two PTO rotational speeds (level-1, level-2) under different paddy and upland field sites with different soil conditions. Results of averaged relative severeness for PTO level-1 and PTO level-2 were 1.96 and 3.34, respectively, at paddy field sites, and they were 1.36 and 2.51, respectively, at upland field sites. The results showed that the PTO driving axle experienced more severe load during rotary tillage at paddy fields than at upland sites, and relative severeness was greater at the higher PTO rotational speed under all of the soil conditions.
산소 플라스마에서의 분자살 적층성장에 의한 CeO₂ 박막의 성장과 구조
김용주(Y. J. Kim),S. A. Chambers(S. A. Chambers) 한국진공학회(ASCT) 2000 Applied Science and Convergence Technology Vol.9 No.1
CeO₂ 박막이 3가지 다른 기판-Si(111), MgO(001), SrTiO₃(001)-위에 넓은 성장조건의 영역에서 산소 플라스마의 분자살 적층성장에 의하여 성장되었다. 본 연구에서 이용된 기판 중 순수 단결정의 CeO₂(001) 박막은 SrTiO₃(001) 기판 위에서만 성장되었다. 이 박막의 구조와 조성은 x-ray diffraction, reflection high-energy electron diffraction, low-energy electron diffraction, x-ray photoelectron spectroscopy, x-ray photoelectron diffraction을 이용하여 확인하였다. 순수 단결정 CeO₂ 박막 성장은 격자상수 차이가 적은 기판의 선택이 아주 중요하고 박막의 성장조건에는 크게 영향을 받지 않는 것으로 나타났다. SrTiO₃(001) 위에 성장된 CeO₂(001) 박막은 표면 reconstruction이 없는 bulk CeO₂와 같은 구조임을 밝혔다. 박막 성장 온도가 650℃ 이상일 때는 기판의 Ti이 CeO₂ 박막으로 확산됨을 관찰하였다. The epitaxial growth of CeO₂ films has been investigated on three different substrates-Si(111), SrTiO₃(001), and MgO(001)-over wide range of growth parameters using oxygen-plasma-assisted molecular beam epitaxy. Pure-phase, single-crystalline epitaxial films of CeO₂(001) have been grown only on SrTiO₃(001). We discuss the growth conditions in conjunction with the choice of substrates required to synthesize this oxide, as well as the associated characterization by menas of x-ray diffraction, reflection high-energy electron diffraction, low-energy electron diffraction, and x-ray photoelectron spectroscopy and diffraction. Successful growth of single crystalline CeO₂ depends critically on the choice of substrate and is rather insensitive to the growth conditions studied in this investigation. CeO₂(001) films on SrTiO₃(001) exhibit the structure of bulk CeO₂ without surface reconstructions. Ti outdiffusion is observed on the films grown temperatures above 650℃.