• Title/Summary/Keyword: Profile optimization

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Velocity Profile Optimization of Flapping Wing Micro Air Vehicle (초소형 날갯짓 비행체의 최적 날갯짓 속도 분포 연구)

  • Cho, Sungyu;Lee, Junhee;Kim, Chongam
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.48 no.11
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    • pp.837-847
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    • 2020
  • A velocity profile for flapping flight is optimized to increase the power efficiency of 20g weighted flapping wing micro air vehicle in hover. The experimental optimization of flapping velocity profile is carried out with a real sized flapper, and various velocity profiles are realized by non-circular gear. Kriging with noise is adopted as a meta model of the profile optimization to reflect the data noise by uncertainty. The optimization results confirm that the flapping efficiency (thrust-to-power ratio) is substantially improved (11.3%) through the elastic deformation that carries the angular kinetic energy from previous stroke.

A Study on Dynamic Simulation and Cam Profile Optimization for OHV Type Valve Trains (OHV형 밸브트레인의 동특성 해석 및 최적 캠 형상설계에 관한 연구)

  • 김도중;윤수환;박병구;신범식
    • Transactions of the Korean Society of Automotive Engineers
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    • v.4 no.1
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    • pp.110-122
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    • 1996
  • The objective of this study is to understand the dynamic characterictics of OHV type valve trains and to design and optimal cam profile which will improve engine performance. A numerical model for valve train dynamics is presented, which aims at both accuracy and computational efficiency. The lumped mass model and distributed parameter model were used to describe the valve train dynamics. Nonlinear characterictics in the valve spring behavior were included in the model. Comprehensive experiments were carried out concerning the valve train dynamics, and the model was tuned based on the test results. The dynamic model was used in designing an optimal cam profile. Because the objective function has many local minima, a conventional local optimizer cannot be used to find an optimal solution. A modified adaptive random search method is successfully employed to solve the problem. Cam lobe area could be increased up to 7.3% without any penalties in kinematic and dynamic behaviors of the valve train.

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A Study on the Optimal Design of Automotive Cam Profiles using Hermite Curve (Hermite 곡선을 이용한 자동차 엔진 캠 형상의 최적 설계에 관한 연구)

  • 김도중;김원현
    • Transactions of the Korean Society of Automotive Engineers
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    • v.6 no.4
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    • pp.129-140
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    • 1998
  • A numerical method is proposed to optimize automotive cam profiles. An acceleration curve of a cam follower motion is described by Hermite spline curves. Because of the intrinsic characteristics of the Hermite curve, it is possible to design an acceleration curve with arbitrary shape. Design variables in the optimization problem are location of control points which define the acceleration curve. Objective function includes dynamic performances as well as kinematic properties of a valve train. Similar optimization procedure was also performed using Polydyne cam profile synthesis method. Optimized profiles using the Hermite curve are proved to be superior to those using the Polydyne method.

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Design and Optimization of TG-CVI Heater (TG-CVI용 히터 형상설계 및 최적화)

  • 이성호;홍성석;구형회
    • Journal of the Korea Institute of Military Science and Technology
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    • v.3 no.2
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    • pp.244-249
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    • 2000
  • Thermal gradient chemical vapor infiltration (TG-CVI) process, which is one of the CVI techniques to densify a porous fiber preform, requires for a heater to have uniform surface temperature distribution. Thus, it is essential to design the shape of the heater and to predict the temperature distribution when the heater has a profile which is not a simple cylinder. In this study, an analytical method has been used to design the inner profile of a conical heater showing uniform temperature distribution, if its outer shape is specified. Temperature distribution on the heater surface has been calculated with the finite difference method and compared with the experimental results. When a heater had a combined profile with a large cone and a small cylinder, temperature was higher in the cylindrical part. To reduce the temperature difference between these areas, a hole-machining method has been proposed including other possible ones. A shape design and optimization program has been made to improve the temperature uniformity of the TG-CVI heater better than that designed with the analytical method.

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Optimization of Etching Profile in Deep-Reactive-Ion Etching for MEMS Processes of Sensors

  • Yang, Chung Mo;Kim, Hee Yeoun;Park, Jae Hong
    • Journal of Sensor Science and Technology
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    • v.24 no.1
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    • pp.10-14
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    • 2015
  • This paper reports the results of a study on the optimization of the etching profile, which is an important factor in deep-reactive-ion etching (DRIE), i.e., dry etching. Dry etching is the key processing step necessary for the development of the Internet of Things (IoT) and various microelectromechanical sensors (MEMS). Large-area etching (open area > 20%) under a high-frequency (HF) condition with nonoptimized processing parameters results in damage to the etched sidewall. Therefore, in this study, optimization was performed under a low-frequency (LF) condition. The HF method, which is typically used for through-silicon via (TSV) technology, applies a high etch rate and cannot be easily adapted to processes sensitive to sidewall damage. The optimal etching profile was determined by controlling various parameters for the DRIE of a large Si wafer area (open area > 20%). The optimal processing condition was derived after establishing the correlations of etch rate, uniformity, and sidewall damage on a 6-in Si wafer to the parameters of coil power, run pressure, platen power for passivation etching, and $SF_6$ gas flow rate. The processing-parameter-dependent results of the experiments performed for optimization of the etching profile in terms of etch rate, uniformity, and sidewall damage in the case of large Si area etching can be summarized as follows. When LF is applied, the platen power, coil power, and $SF_6$ should be low, whereas the run pressure has little effect on the etching performance. Under the optimal LF condition of 380 Hz, the platen power, coil power, and $SF_6$ were set at 115W, 3500W, and 700 sccm, respectively. In addition, the aforementioned standard recipe was applied as follows: run pressure of 4 Pa, $C_4F_8$ content of 400 sccm, and a gas exchange interval of $SF_6/C_4F_8=2s/3s$.

Optimization of Stacking Line and Blade Profile for Design of Axial Flow Fan Blade (중첩선과 단면형상을 고려한 축류 송풍기 날개의 최적설계)

  • Samad, Abdus;Lee, Ki-Sang;Jung, Sang-Ho;Kim, Kwang-Yong
    • 한국전산유체공학회:학술대회논문집
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    • 2008.03b
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    • pp.420-423
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    • 2008
  • This present work is to find optimum design of a NACA65 axial fan blade with weighted average surrogate model. The numerical analysis by Reynolds-average Navier-Stokes equations with shear stress turbulence(SST) is discretized by finite volume approximations and solved on hexahedral grids for flow analysis. The blade aerodynamic shape is modified by six design variables for the optimization. The blade profile as well as stacking line is modified to enhance blade total efficiency. Six design variables, airfoil maximum camber, maximum camber location, leading edge radius, trailing edge radius, lean angle at 50% span and lean angle at 100% span, are selected for blade profile to enhance the total efficiency. The PBA model which is basically weighted average of the basis surrogates is used to find the optimal design in the design space from the constructed response surface model for the objective function. By the optimization, the total efficiency is increased by 1.4%.

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Optimum design of steel floor system: effect of floor division number, deck thickness and castellated beams

  • Kaveh, A.;Ghafari, M.H.
    • Structural Engineering and Mechanics
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    • v.59 no.5
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    • pp.933-950
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    • 2016
  • Decks, interior beams, edge beams and girders are the parts of a steel floor system. If the deck is optimized without considering beam optimization, finding best result is simple. However, a deck with higher cost may increase the composite action of the beams and decrease the beam cost reducing the total cost. Also different number of floor divisions can improve the total floor cost. Increasing beam capacity by using castellated beams is other efficient method to save the costs. In this study, floor optimization is performed and these three issues are discussed. Floor division number and deck sections are some of the variables. Also for each beam, profile section of the beam, beam cutting depth, cutting angle, spacing between holes and number of filled holes at the ends of castellated beams are other variables. Constraints include the application of stress, stability, deflection and vibration limitations according to the load and resistance factor (LRFD) design. Objective function is the total cost of the floor consisting of the steel profile cost, cutting and welding cost, concrete cost, steel deck cost, shear stud cost and construction costs. Optimization is performed by enhanced colliding body optimization (ECBO), Results show that using castellated beams, selecting a deck with higher price and considering different number of floor divisions can decrease the total cost of the floor.

Multi-level Optimization using Reduced Basis Technique for Prestressed Concrete Box Girders (기저함수 감소기법을 이용한 프리스트레스트 콘크리트 박스거더의 다단계 최적설계)

  • 조효남;민대홍;김환기;정봉교
    • Proceedings of the Korea Concrete Institute Conference
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    • 2001.05a
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    • pp.827-832
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    • 2001
  • A multi-level optimum design algorithm for prestressed concrete (PSC) box girders is proposed in this paper. To save the numerical efforts, a multi-level optimization technique using model coordination method that separately utilizes both tendon profile design and section design is incorporated. And also, a reduced basis technique for the efficient tendon profile optimization is proposed in this paper. From the numerical investigations, it may be positively stated that the optimum design of PSC box girder based on the new approach proposed in this study will lead to more rational and economical design compared with the currently available designs.

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Multi-Objective Optimization of Steel Frames For Standardized Steel Profiles Under Seismic Loads (지진하중을 받는 강뼈대구조물의 표준단면에 대한 다목적 최적설계)

  • Cho, Hyo Nam;Min, Dae Hong;Jeong, Bong Gyo
    • Journal of Korean Society of Steel Construction
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    • v.14 no.6
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    • pp.783-791
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    • 2002
  • An improved formulation for multi-objective optimization was proposed. This formulation was applied to steel seismic loads. The multi-objective optimization problem was formulated with minimum structural weight, maximum strstability. The global criterion method was employed to find a rational solution closest to the ideal solution for the optimization problem using standard steel profile, To efficiently solve the optimization problem, the decomposition meth both system-level and element-level was used. In addition, various techniques including efficient reanalysis technique intermediate variables and sensitivity analysis using an automatic differentiation(AD) were incorporated. Moreover the reamong section properties fitted to the section profile used in order to link the system level and the element level. From numerical investigation, it could be stated that the proposed method will lead to the more rational design compared with one.

Multiple Drones Collision Avoidance in Path Segment Using Speed Profile Optimization (다수 드론의 충돌 회피를 위한 경로점 구간 속도 프로파일 최적화)

  • Kim, Tae-Hyoung;Kang, Tae Young;Lee, Jin-Gyu;Kim, Jong-Han;Ryoo, Chang-Kyung
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.50 no.11
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    • pp.763-770
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    • 2022
  • In an environment where multiple drones are operated, collisions can occur when path points overlap, and collision avoidance in preparation for this is essential. When multiple drones perform multiple tasks, it is not appropriate to use a method to generate a collision-avoiding path in the path planning phase because the path of the drone is complex and there are too many collision prediction points. In this paper, we generate a path through a commonly used path generation algorithm and propose a collision avoidance method using speed profile optimization from that path segment. The safe distance between drones was considered at the expected point of collision between paths of drones, and it was designed to assign a speed profile to the path segment. The optimization problem was defined by setting the distance between drones as variables in the flight time equation. We constructed the constraints through linearize and convexification, and compared the computation time of SQP and convex optimization method in multiple drone operating environments. Finally, we confirmed whether the results of performing convex optimization in the 20 drone operating environments were suitable for the multiple drone operating system proposed in this study.