• Journal of Mechanical Science and Technology
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• 제16권7호
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• pp.882-888
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• 2002

In this paper, an algorithm to increase the shift speed is suggested by increasing the line pressure for a metal belt CVT. In order to control the shift speed, an algorithm to calculate the target shift speed is presented from the modified CVT shift dynamics. In applying the shift speed control algorithm, a criterion is proposed to prevent the excessive hydraulic loss due to the increased line pressure. Simulations are performed based on the dynamic models of the hydraulic control valves, powertrain and the vehicle. It is found from the simulation results that performance of the engine operation can be improved by the faster shift speed, which results in the improved fuel economy by 2% compared with that of the conventional electronic control CVT in spite of the increased hydraulic loss due to the increased line pressure.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1778-1782
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• 2004

A new algorithm, CBIR (Correlation-Based Image Registration) was proposed to improve the resolution of image registration for PSP (Pressure-Sensitive Paint). The local displacement vectors were obtained by finding the displacement which maximizes the cross-correlation between two interrogation windows of 'wind-off' and 'wind-on' images. A recursive multigrid processing was employed to increase the non-linear spatial resolutions. The variations of image were precisely measured without identifying the control points.

• 동력기계공학회지
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• 제21권6호
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• pp.56-61
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• 2017

The check valves are mechanical valves that permit fluids to flow in only one direction, preventing flow from reversing. It is classified as one way directional valves. There are various types of check valves that used in a marine application. A lift type check valve uses the disc to open and close the passage of fluid. The disc lift up from seat as pressure below the disc increases, while drop in pressure on the inlet side or a build up of pressure on the outlet side causes the valve to close. An important concept in check valves is the cracking pressure which is the minimum upstream pressure at which the valve will operate. On the other hand, optimization is a process of finding the best set of parameters to reach a goal while not violating certain constraints. The AMESim software provides NLPQL(Nonlinear Programming by Quadratic Lagrangian) and genetic algorithm(GA) for optimization. NLPQL is the implementation of a SQP(sequential quadratic programming) algorithm. SQP is a standard method, based on the use of a gradient of objective functions and constraints to solve a non-linear optimization problem. A characteristic of the NLPQL is that it stops as soon as it finds a local minimum. Thus, the simulation results may be highly dependent on the starting point which user give to the algorithm. In this paper, we carried out optimization design of the check valve with NLPQL algorithm.

• Nuclear Engineering and Technology
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• 제54권9호
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• pp.3283-3292
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• 2022

Based on the Deep Q-Network(DQN) algorithm of reinforcement learning, an active fault-tolerance method with incremental action is proposed for the control system with sensor faults of the once-through steam generator(OTSG). In this paper, we first establish the OTSG model as the interaction environment for the agent of reinforcement learning. The reinforcement learning agent chooses an action according to the system state obtained by the pressure sensor, the incremental action can gradually approach the optimal strategy for the current fault, and then the agent updates the network by different rewards obtained in the interaction process. In this way, we can transform the active fault tolerant control process of the OTSG to the reinforcement learning agent's decision-making process. The comparison experiments compared with the traditional reinforcement learning algorithm(RL) with fixed strategies show that the active fault-tolerant controller designed in this paper can accurately and rapidly control under sensor faults so that the pressure of the OTSG can be stabilized near the set-point value, and the OTSG can run normally and stably.

• 한국안전학회지
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• 제38권2호
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• pp.8-14
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• 2023

In various industrial sites, piping systems play an essential role in stable fluid supply and pressure maintenance. However, these systems are constantly exposed to risks of earthquakes, explosions, fires, and leaks, which can result in casualties or serious economic losses. With rapid advancements in the industry, different-sized piping systems have been launched; however, there are not enough maintenance personnel for troubleshooting and responding to situations where damages occur to piping systems. This increases the need for introducing autonomous damage management systems. In this study, a lab-based piping system was designed and manufactured by referring to the piping system of a naval ship to analyze the effectiveness of autonomous damage management systems. By using this testbed, a representative algorithm, the hydraulic resistance control algorithm, was realized and examinedIn addition, the difference between the averaged pressure and normalized pressure was introduced to improve the performance of the existing algorithm, which faces some limitations with regard to sensor noise and back pressure from the rupture-simulated pipeline part.

• 대한의용생체공학회:의공학회지
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• 제21권4호
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• pp.411-417
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• 2000

본 연구에서는 시뮬레이션을 이용하여 동맥압 파형 형태에 대한 오실로메트릭 방법을 분석하고 수축기압과 이완기압을 검출할 수 있는 새로운 알고리즘을 제시하였다. 동맥압 파형 형태에 대한 오실로메트릭 방법을 분석하고 수축기압과 이완기압을 검출할 수 있는 새로운 알고리즘을 제시하였다. 동맥압 파형 형태에 대한 오실로메트릭 방법을 분석하기 위해 동맥압 파형 형태를 쉽게 가변할 수 있는 동맥압 모델을 만들었으며, 기존의 정적인 동맥 압력-용적 지수함수 모델을 이용하여 오실로메트릭 모델의 구현 및 컴퓨터 시뮬레이션을 수행하였다. 동맥압 파형 형태와 보편화된 혈압 검출 기준인 특성비율과의 상관관계 분석을 통하여 동맥압 파형 형태와 맥압의 영향 때문에 특성비율이 수축기압과 이완기압을 결정하는 유일한 기준이 될 수 없음을 밝혔으며, 동맥압 파형 형태와 오실레이션 파형 형태의 상관관계 분석을 통하여 오실레이션 파형으로부터 동맥압 파형 형태를 추정할 수 있는 방법을 제시하였다. 최대 크기 오실레이션 파형과 동맥압 파형의 관계로부터 맥압을 구할 수 있는 맥압 표를 구성하여 수축기압과 이완기압을 검출할 수 있는 혈압 검출 알고리즘을 제시하였으며 그 결과 수축압, 이완압, 평균압의 절대편차 평균값은 각각 1.62%, 2.40%, 2.20%를 얻었다. 결론적으로 제안된 알고리즘은 정확한 혈압검출을 위한 유용 가능성을 보였다.

• 한국공간구조학회논문집
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• 제21권4호
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• pp.49-56
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• 2021

This study aims to develop a form-finding algorithm for a single-layered pneumatic membrane. The initial shape of this pneumatic membrane, which is an air-supported type pneumatic membrane, is to find a state in which a given initial tension and internal pneumatic pressure are in equilibrium. The algorithm developed to satisfy these conditions is that a nonlinear optimization problem based on the force method considering the deformed shape is formulated, and, it's able to find the shape by iteratively repeating the process of obtaining a solution of the governing equations. An computational technique based on the Gauss-Newton method was used as a method for obtaining solutions of nonlinear equations. In order to verify the validity of the proposed form-finding algorithm, a single-curvature pneumatic membrane example and a double-curvature air pneumatic membrane example were adopted, respectively. In the results of these examples, it was possible to well observe the step-by-step convergence process of the shape of the pneumatic membrane, and it was also possible to confirm the change in shape according to the air pressure. In addition, the calculation results of the shape and internal force after deformation due to initial tension, air pressure, and self-weight were obtained.

• Steel and Composite Structures
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• 제19권1호
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• pp.75-92
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• 2015

In this paper, optimization of cylindrical shells under external pressure to minimize its weight has been studied. Buckling equations are based on standard of ABS underwater vehicles. Dimension and type of circumferential stiffeners, and its distance from each other are assumed as variables of optimization problem. Considering the extent of these variables, genetic algorithms have been used for optimization. To study the effect of hydrostatic pressure on the shell and its fabrication according to the existing standards, geometrical and construction as well as stress and buckling constraints have been used in optimization algorithm and also penalty functions are applied to eliminate weak model. Finally, the best model which has the minimum weight considering the applied pressure has been presented.

• 한국정보통신학회논문지
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• 제26권7호
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• pp.963-971
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• 2022

상수도 관망은 국가 수도 시설의 주요한 구성 요소이지만 대부분이 지중에 매립되어 있어 배관의 노후화 정도 및 누수를 파악하기 어려우므로 유지관리 하기가 매우 어렵다. 본 연구에서는 관망에 설치된 다양한 센서 조합을 가정하여, 데이터 조합에 따른 관로 누수 판별 가능성을 검토하기 위하여 선형회귀분석, 뉴로퍼지 등의 인공지능 알고리즘을 통한 유량과 압력 예측을 실시하여 최적 알고리즘을 도출하였다. 공급압력 예측을 통한 누수판별의 경우 뉴로퍼지 알고리즘이 선형회귀분석에 비하여 우수하였다. 누수유량 예측에서는 뉴로퍼지를 이용한 유량예측이 우선 고려되어야 한다. 다만, 유량을 모사하기 힘든 경우에는 선형 알고리즘을 이용한 공급압력 예측이 이루어져야 할 것으로 사료 된다.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2003년도 추계학술대회 논문집
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• pp.63-66
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• 2003

A new algorithm, CBIR (Correlation Based Image Registration) was proposed to improve the resolution of image registration for PSP (Pressure Sensitive Paint). The local displacement vectors were obtained by finding the displacement which maximizes the cross-correlation between two interrogation windows of 'wind-off' and 'wind-on' images. A recursive multigrid processing was employed to increase the non-linear spatial resolutions. The variations of image were precisely measured without identifying the control points.