基于多目标遗传算法的弧齿锥齿轮多学科优化设计

针对常规设计中弧齿锥齿轮存在的问题,将多学科优化设计引入到弧齿锥齿轮设计中,改善其不足。以大小弧齿锥齿轮体积之和最小、弧齿锥齿轮齿根弯曲应力最小以及工作噪音最小三个方面为目标函数,以齿数、齿宽中点螺旋角、齿宽和大端模数为设计变量,考虑齿面接触疲劳强度、齿根弯曲疲劳强度、环境保护等8个方面约束,建立弧齿锥齿轮的多学科优化设计数学模型。根据该数学模型,运用多目标遗传算法对文中的实例优化求解,计算结果表明该设计方法是合理的,行之有效的。     

Adaptive parallel decomposition for multidisciplinary design

The conceptual design of a rotorcraft system involves many different analysis disciplines. The decomposition of such a system into several subsystems can make analysis and design more efficient in terms of the total computation time. Adaptive parallel decomposition makes the structure of the overall design problem suitable to apply the multidisciplinary design optimization methodologies and it can exploit parallel computing. This study proposes a decomposition method which adaptively determines the number and sequence of analyses in each sub-problem corresponding to the available number of processors in parallel. A rotorcraft design problem is solved and as a result, the adaptive parallel decomposition method shows better performance than other previous methods for the selected design problem.     

基于Agent模型的多学科设计优化方法

复杂工程系统的设计往往涉及多门学科 ,多学科设计优化 (MDO)方法是一类求解复杂系统设计优化问题的方法。本文首先简要回顾现有 MDO方法的特点 ,然后基于 Agent模型提出了一种新的多学科设计优化方法——子空间自主式优化方法。这种方法具有如下特点 :流程简单 ;各个学科组可自主地、并行地进行设计和优化 ;灵活性强 ;所需系统分析的计算次数少 ;没有系统级协调优化环节。为了验证这种算法的有效性 ,对二个典型算例进行了数值实验。初步的数值实验结果表明 ,二个典型的算例经过几次迭代后均能收敛于最优解。子空间自主式方法是一种较有潜力的 MDO方法 ,值得进一步研究     

梳齿式微加速度计优化设计与仿真分析

给出了多学科层级优化算法模型,对梳齿式微加速度计的结构参数进行了优化设计,对优化前后的梳齿式微加速度计进行了有限元仿真分析.优化设计结果表明,微加速度计的工作性能有明显提高.有限元仿真分析结果验证了多学科层级设计优化方法的有效性.     

基于Kriging模型的后优化近似研究

后优化分析技术定量地研究当优化参数发生变化时,相应的优化结果会发生怎样的改变。过去的研究多集中在对优化结果的敏感度分析(一阶近似),所得到的结果只在当前参数的微小扰动范围内有效。用Kriging模型进行优化结果的插值近似(相对于优化参数),从而可以提供整个参数空间中优化结果的全貌。用简单的算例与一阶近似、二次响应面近似进行了比较,同时为了解决临界约束集发生改变时,目标函数突变对Kriging模型近似精度带来的影响,提出一种分片插值方案,较大地提高了Kriging的近似精度。     

Multidisciplinary optimization of a butterfly valve

A butterfly valve is a type of flow control device, typically used to regulate fluid flow. This paper proposes a new process to meet desired needs in valve design that is characterized by the complex configuration. First, the need is identified according to the valve user/company, and then the problem is defined with a characteristic function. Second, the initial model of valve is made, and then the initial analysis including fluid and/or structural analysis is carried out to predict the fluid and/or structural performance of the valve. Third, the optimization in the form of mathematical functions, which considers single or multiple objective and/or discipline, is handled. This part includes the design of computer experiment, approximation technique, topology optimization and sizing optimization. Finally, the validation experiment is conducted based on the optimum result to verify the accuracy of the optimization. An example is provided to confirm the availability of the process proposed here.     

基于ISIGHT的曲柄连杆机构多学科优化

多学科优化方法(MDO)可以弥补传统优化的不足,有效解决复杂优化问题,提高工程项目的设计和优化效率.针对柴油机曲柄连杆机构多学科部件优化问题,综合考虑曲轴和连杆两部件,采用协同优化方法,建立了相应的多学科优化数学模型,并基于ISIGHT软件构建多学科优化平台,进行了曲柄连杆机构多学科综合优化计算.研究结果表明,采用多学...     

A parametric study on design of a microrate-gyroscope with parametric resonance

Parametric excitation for MEMS gyroscopes can provide resonance in both the drive and the sense modes, even with mismatched natural frequencies. In this paper, requirements for such a condition are studied by analyzing the effect of each factor on the steady state amplitudes of the two modes. To develop a general study, the governing equation of the gyroscope is scaled and non-dimensionalized. The resulting governing equation is in the form of a cubic Mathieu equation coupled to a Duffing equation. In the study of the scaled system, for a gyroscope with matched natural frequencies, three sets of optimum designs are obtained. Then, the robustness of parametric excitation for a gyroscope with mismatching modes is shown. As the results indicate, parametric excitation is able to provide high accuracy and robustness for MEMS gyroscopes.     

机械多学科设计优化中的产品建模技术研究

从产品到建立优化模型,是理论与经验交互的工作.提出建立产品学科树和产品性能树,不仅实现用树的形式表达产品建模的工作过程,而且分别获取了产品的设计变量和设计函数.     

Performance optimization of hypervelocity launcher system using experimental data

This study presents the performance optimization of hypervelocity launcher system by using the experimentall data. During the optimization, the RSM (Response Surface Method) is adopted to find the operating parameters that could maximize the projectile speed. To construct a reliable response surface model, 3 full factorial method is used with the selected design variables, such as piston mass and 2 driver fill pressure. Nine test data could successfully construct the reasonable response surface, which used to yield the optimal operational conditions of the system using the genetic algorithm. The optimization results are confirmed by the experimental test with a good accuracy. Thus, the optimization can improve the performance of the facility.     

Reliability-based design optimization of slider air bearings

This paper presents a design methodology for determining configurations of slider air bearings considering the randomness of the air-bearing surface (ABS) geometry by using the iSIGHT. A reliability-based design optimization (RBDO) problem is formulated to minimize the variations in the mean values of the flying heights from a target value while satisfying the desired probabilistic constraints keeping the pitch and roll angles within a suitable range. The reliability analysis is employed to estimate how the fabrication tolerances of individual slider parameters affect the final flying attitude tolerances. The proposed approach first solves the deterministic optimization problem. Then, beginning with this solution, the RBDO is continued with the reliability constraints affected by the random variables. Reliability constraints overriding the constraints of the deterministic optimization attempt to drive the design to a reliability solution with minimum increase in the objective. The simulation results of the RBDO are listed in comparison with the values of the initial design and the results of the deterministic optimization, respectively. To show the effectiveness of the proposed approach, the reliability analyses are simply carried out by using the mean value first-order second-moment (MVFO) method. The Monte Carlo simulation of the RBDO’s results is also performed to estimate the efficiency of the proposed approach. Those results are demonstrated to satisfy all the desired probabilistic constraints, where the target reliability level for constraints is defined as 0.8.     

基于自定义特征的透平叶轮产品族参数化建模方法研究

针对制冷透平膨胀机叶轮的结构特点,以UG软件为支撑平台,运用实体建模概念,结合表达式、电子表格以及用户自定义特征等功能,提出了叶轮产品族三维参数化建模的方法,为企业实现叶轮产品的快速开发提供了一种新的途径.     

基于遗传算法的非线性控制系统参数优化方法

本文针对非线性控制系统参数优化问题,结合非线性控制系统理论、最优化理论及遗传算法,提出了一种新的仿真优化方法,该方法利用遗传算法来求解非线性控制系统参数优化问题,由于遗传算法是在解空间的多个区域内进行搜索,能以较大的概率跳出局部最优,因此可技巧以整体最优解。仿真结果表明,该方法是一种有效的非线性控制系统参数优化方法。     

复杂微机电系统多学科设计方法研究

针对复杂微机电系统设计涉及多个学科领域的特点,提出了应用多学科设计优化方法来设计复杂微机电工程产品,归纳分析了复杂微机电系统在设计过程中可能涉及的学科,探讨了多学科设计方法在复杂微机电系统设计中的应用。     

A parametric study of sheet metal denting using a simplified design approach

In the interest of improved automotive fuel economy, one solution is reducing vehicle weight. Achieving significant weight reductions will normally require reducing the panel thickness or using alternative materials such as aluminum alloy sheet. These changes will affect the dent resistance of the panel. In this study, the correlation between panel size, curvature, thickness, material properties and dent resistance is investigated. A parametric approach is adopted, utilizing a “design software” tool incorporating empirical equations to predict denting and panel stiffness for simplified panels. The most effective time to optimize an automotive body panel is early in its development. The developed design program can be used to minimize panel thickness or compare different materials, while maintaining adequate panel performance.     

Optimal design of nonlinear squeeze film damper using hybrid global optimization technique

The optimal design of the squeeze film damper (SFD) for rotor system has been studied in previous researches. However, these researches have not been considering jumping or nonlinear phenomena of a rotor system with SFD. This paper represents an optimization technique for linear and nonlinear response of a simple rotor system with SFDs by using a hybrid GA-SA algorithm which combined enhanced genetic algorithm (GA) with simulated annealing algorithm (SA). The damper design parameters are the radius, length and radial clearance of the damper. The objective function is to minimize the transmitted load between SFD and foundation at the operating and critical speeds of the rotor system with SFD which has linear and nonlinear unbalance responses. The numerical results show that the transmitted load of the SFD is greatly reduced in linear and nonlinear responses for the rotor system.     

Topological design sensitivity on the air bearing surface of head slider

In this study, a topological design sensitivity of the air bearing surface (ABS) is suggested by using an adjoint variable method. The discrete form of the generalized lubrication equation based on a control volume formulation is used as a compatible condition. A residual function of the slider is considered as an equality constraint function, which represents the slider in equilibrium. The slider thickness parameters at all grid cells are chosen as design variables since they are the topological parameters determining the ABS shape. Then, a complicated adjoint variable equation is formulated to directly handle the highly nonlinear and asymmetric coefficient matrix and vector in the discrete system equation of air-lubricated slider bearings. An alternating direction implicit (ADI) scheme is utilized for the numerical calculation. This is an efficient iterative solver to solve large-scale problem in special band storage. Then, a computer program is developed and applied to a slider model of a sophisticated shape. The simulation results of design sensitivity analysis (DSA) are directly compared with those of FDM at the randomly selected grid cells to show the effectiveness of the proposed approach. The overall distribution of DSA results are reported, clearly showing the region on the ABS where special attention should be given during the manufacturing process.     

Ethanolysis of soybean oil into biodiesel: process optimization via central composite design

A process for production of ethyl ester for use as biodiesel has been studied. The sodium hydroxide catalyzed transesterification of soybean oil with ethanol was carried out at different molar ratio of alcohol to oil, reaction temperature and catalyst amount for a constant agitation in two hours of reaction time. Central composite design and response surface methodology were used to determine optimum condition for producing biodiesel. It was found that ethanol to oil ratio and catalyst concentration have a positive influence on ester conversion as well as interaction effects between the three factors considered. An empirical model obtained was able to predict conversion as a function of ethanol to oil molar ratio, reaction temperature and catalyst concentration adequately. Optimum condition for soybean ethyl ester production was found to be moderate ethanol to oil ratio (10.5: l), mild temperature range (70°C) and high catalyst concentrations (l.0%wt), with corresponding ester conversion of 93.0%.     

System identification of a composite plate using hybrid response surface methodology and particle swarm optimization in time domain

Material properties of composites are identified using a novel hybrid RSM–PSO method in this paper. Different response surface methodology (RSM) methods and particle swarm optimization (PSO) methods are studied initially on a 4 degrees-of-freedom (4DOF) dynamic system on their performance in terms of speed and accuracy. The best combination is used as a hybrid RSM–PSO method to evaluate the performance on system identification of an orthotropic plate along with a 4DOF dynamic system and an isotropic plate. The novelty of the present paper is to identify the composite plate material properties using RSM methods based on time domain signals, which is not hitherto reported in the literature. Also, whereas previous papers have used full factorial design for system identification, here CCDI is used. The input factors (design variables) are the system parameters which are to be identified and the response (objective function) is error sum-of-square of acceleration response with respect to new test system. The performance of the proposed method is also evaluated with the addition of 5% Gaussian noise to simulate the experimental errors. The system parameters of the orthotropic plate were identified with 0% and 0.25% average prediction error with zero and 5% addition of noise respectively by the proposed hybrid RSM–PSO method. It is also showed a much better performance and robustness to noise addition when compared to the other RSM methods in the literature.     

纳秒近红外KTP光学参量振荡器的理论设计

对纳秒近红外KTP光学参量振荡器(KTP-OPO)进行了全面系统的理论设计。讨论了KTP-OPO的相位匹配,计算了KTP的走离角、允许角和有效非线性系数,数值模拟了角度调谐曲线和增益曲线,从而确定了调谐范围为1.35~2.0 μm,晶体切割角为59.6°。同时,分析了晶体长度、走离角以及输出镜耦合率对OPO阈值的影响,总结了降低参量阈值的几种方法。