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In designing lenses with the damped least squares method, the solution obtained by optimization routine is a local minimum of the merit function. To get out of this and seek a different solution, we propose to use an ‘escape function’ as an additional operand of the lens system, to be controlled. Experiments were made on simple models of merit function and the advantage of this technique was ascertained. We also planted this algorithm into OSLO SIX (lens design software by Sinclair Optics) by means of CCL (C-compatible language) and applied it to actual lens design. Experiments convinced us that the method would be an effective tool for global optimization. 相似文献
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针对启发式算法在优化换热网络后期由于种群多样性消失等原因造成难以找到使年综合费用进一步下降的进化方向,本文提出换热器耦合联动进化策略.该策略在一般启发式算法优化后期通过按一定概率分布抽取部分换热量不为零的换热器参与联动进化,以找到使费用下降的耦合匹配.算例验证表明,该策略效果明显.将该策略与RWCE算法相结合组成一种混合算法.首先采用RWCE算法对求解域进行初步探索,利用该算法强大的全局搜索能力找到求解域内各个潜力结构.然后再用耦合联动进化策略对各潜力结构进行深入搜索,搜索完成后再经变异反馈给RWCE算法.将该混合算法应用于10SP2和15SP算例,得到了较好的优化结果. 相似文献
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Issues concerning the efficiency of the Global Explorer (GE) algorithm are studied. Global optimization with GE consists of many local optimization runs with or without the escape function using the damped-least-squares method. In order to improve the efficiency of the local optimization and the GE run, two search schemes are incorporated. The first one searches for the best damping factor which effectively determines the optimum direction of the solution vector in the multi-dimensional variable space, and the second search is conducted along that direction to find the optimum length of the solution vector. Experiments are also made to determine the optimum default values for the parameters of the escape function. The algorithm with the improvements is successfully implemented in the GOLD program developed by Beijing Institute of Technology. Design examples using the software are given, which show that the global optimization feature is practical and powerful. 相似文献
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In this paper we derive a general analytical solution for a monocentric lens system and present a global optimization method combining sequential design for global optimization and an expected improvement algorithm for global optimization for the design and analysis of a layered monocentric lens system, which provides an “intelligent” way to search the optimization space based on accumulated experience. We then apply these methods to an example of monocentric lens design, and explore the improvement in system performance obtained through increasing the system volume. 相似文献
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ZEMAX和CODE V等光学设计软件,虽然有很强的优化功能,但如果想得到好的设计结果,初始解的选择至关重要。求初始解的普遍做法是,将已有的光学系统或其中某一个组元拿来进行缩放。这种办法带有盲目性。另一种方法就是利用高斯光学和三级像差理论求变焦距物镜的初始解。这一方法有助于创新设计,但却很少被应用。本文介绍了作者在运用这一方法过程中产生的观点、理念、经验和成果。本文通过一个十倍变焦距物镜设计实例,详细介绍了求初始解的过程,为了验证该初始解的效果,还用ZEMAX进行了像差优化。为了增加说服力,设计过程的每一步,都给出了具体的数据,包括经ZEMAX优化得到的最后结果。 相似文献
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Chunhui Chung 《Journal of sound and vibration》2011,330(12):2947-2963
The classical modal analysis is applied to derive the analytical solution and to obtain the free vibration response of damped axially moving wire in this paper. The corresponding eigenvalues, eigenfunctions, and orthogonal relationship are presented. The orthogonality property and closed-form solution of free vibration response with damping are the main contributions of this study. In addition, the analytical modal analysis, with damping factor removed, shows agreement with those in existing research literature of moving wire without damping. The specific relevance of this general solution is discussed with respect to the moving wire in a slurry wiresaw. The theoretical definition of the damping factor of the slurry wiresaw system is also provided. 相似文献
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In this paper, we propose a hybrid biological image processing approach, which is based on Chaotic Differential Search (CDS) algorithm and lateral inhibition (LI) mechanism. We named this hybrid biological image processing approach as LI-CDS. Differential Search (DS) algorithm is a new bio-inspired optimization algorithm mimicking the migration behavior of an organism, and has been successfully used for solution of coordinate system transformation. The property of chaotic variable is integrated into DS to improve its search strategy so that it can escape from the local optimum. Furthermore, lateral inhibition mechanism, which is verified to have good effects on image edge extraction and image enhancement, is employed to pre-process images involved. In this hybrid biological image processing mechanism, our proposed LI-CDS method incorporates both advantages of chaos theory and lateral inhibition mechanism. Series of comparative experimental results by using LI-CDS, DS, CDS and Particle Swarm Optimization (PSO) demonstrate that the proposed LI-CDS performs better than the other three methods. 相似文献
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The Fresnel lens is one of the most extensively studied components in both classical and integrated optics. This structure is free from axial spherical aberration, but is heavily affected by both off-axis and chromatic aberrations. The latter can be compensated by introducing a refractive component, whose chromatic behavior is the opposite of that of the diffractive lens. This hybrid refractive-diffractive structure, however, is not able to deal effectively with off-axis aberrations, namely, with coma. In this work, a novel methodology for the design of corrected hybrid lenses is proposed which allows for correction of both chromatism and coma. The design method is based on a ray-optics variational approach which provides a range of possible achromatic solutions. An optimization procedure is performed by means of a series of beam propagation method numerical calculations which make it possible to simulate the lens operation and thus to find the best solution. 相似文献
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Now Ground penetrating radar (GPR) nondestructive testing methods have been applied to many fields of physics. But traditional electromagnetic methods (usually based on least square and local iteration) just roughly give the information of location, level and quality. In this paper we consider inverse electromagnetic problem which is concerned with the estimation of electric conductivity of Maxwell’s equations. A wavelet multilevel representation is proposed to inversion of GPR nondestructive testing. Once we decompose the objective functional onto different levels from the smallest to the largest, there are very few local minimum on the largest level component of the problem. Then local convergent Gauss-Newton method could easily find the global minimum on this level which is close to the global optimization solution on the second largest level. So, Gauss-Newton method with initial value which is solved on the largest level has serious possibility to find the global minimum of the second largest level. Repeating this step one could find the global optimization solution of the original inverse problem. On each level, the stable and fast local convergent Gauss-Newton method is carried out. Results exhibits clear advantages over damping Gauss-Newton method and testify that it is an available method, especially on aspects of wide convergence and precision. 相似文献
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Structure borne vibration and noise in an automobile are often explained by representing the full vehicle as a system of elastically coupled beam structures representing the body, engine cradle and body subframe where the engine is often connected to the chassis via inclined viscoelastic supports. To understand more clearly the interactions between a beam structure and isolators, this article examines the flexural and longitudinal motions in an elastic beam with intentionally inclined mounts (viscoelastic end supports). A new analytical solution is derived for the boundary coupled Euler beam and wave equations resulting in complex eigensolutions. This system is demonstrated to be self-adjoint when the support stiffness matrices are symmetric; thus, the modal analysis is used to decouple the equations of motion and solve for the steady state, damped harmonic response. Experimental validation and computational verifications confirm the validity of the proposed formulation. New and interesting phenomena are presented including coupled rigid motions, modal properties for ideal angled roller boundaries, and relationships between coupling and system modal loss factors. The ideal roller boundary conditions when inclined are seen as a limiting case of coupled longitudinal and flexural motions. In particular, the coupled rigid body motions illustrate the influence of support stiffness coupling on the eigenvalues and eigenfunctions. The relative modal strain energy concept is used to distinguish the contribution of longitudinal and flexural deformation modes. Since the beam is assumed to be undamped, the system damping is derived from the viscoelastic supports. The support damping (for a given loss factor) is shown to be redistributed between the system modes due to the inclined coupling mechanisms. Finally, this article provides valuable insight by highlighting some technical issues a real-life designer faces when balancing modeling assumptions such as rigid or elastic formulations, proportional or non-proportional damping, and coupling terms in multidimensional joint properties. 相似文献
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为了解决高功率白光LED光源输出高均匀度窄光束的问题,设计了一种由复合抛物面反射器、菲涅尔透镜和非球面透镜组成的照明系统。设计中以板上芯片型(COB)集成光源的配光曲线为依据构建光源仿真模型,由复合抛物面反射器实现大角度光线初次会聚之后,再由菲涅尔透镜控制溢散光,最后利用非球面透镜进行准直配光。采用TracePro进行蒙特卡洛光线追迹,根据仿真得到的系统性能指标,并研制出实物装置进行实验测试。最终测试结果表明:窄光束均匀照明系统可以输出±7.9°的光束,并且在距离系统出光面0.7 m左右的区域形成均匀度超过96%的圆形光斑,整体光效达到60%。 相似文献
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为了保持神经网络在优化计算求解过程中结构不被改变, 以迟滞混沌神经元和迟滞混沌神经网络为研究对象, 提出了一种基于滤波跟踪误差的控制策略来实现神经元/网络的稳定控制. 采用该控制策略, 在不改变非线性特性发生机理的情况下, 神经元/网络可实现函数优化计算问题的求解. 所设计的控制律包含两部分: 一部分是系统进入滤波跟踪误差面时的等效控制部分, 另一部分为确保系统快速进入滤波跟踪误差面的控制部分. 采用Lyapunov方法对神经元/网络的控制进行了稳定性证明. 根据待寻优函数直接求得神经元的控制律, 在该控制律的作用下, 神经元/网络可逐渐稳定到优化函数的极值点, 从而实现优化问题的求解, 仿真实验结果验证了该控制方法在优化计算中的可行性和有效性. 相似文献
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提出一种基于自然选择的粒子群算法(SelPSO)的扩展光源匀透镜设计方法。该方法通过DDE技术,将TracePro的光线追迹功能与Matlab的信息处理功能有机结合,建立以点光源透镜轮廓为对象的优化模型,进而利用加入平滑度约束的SelPSO算法对模型进行全局优化。以h/d=2.5∶1的紧凑型匀光透镜为例,结果表明:SelPSO算法与PSO算法在相同参数下进行优化,SelPSO算法具有更强且更快的全局收敛能力,优化后透镜表面光滑易加工,且均匀度、光效分别达到87.566%、89.536%;对透镜安装公差进行分析后,将横向、纵向位移误差分别控制在[0 mm,2 mm]内,对照明效果产生的影响较小;此方法还具有较强普适性,可针对不同照明范围的照明系统进行优化,且整体照明效果良好。 相似文献
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Two-mode vibration control of a beam using nonlinear synchronized switching damping based on the maximization of converted energy 总被引:2,自引:0,他引:2
In this paper, a new switch control strategy based on an energy threshold is proposed for the synchronized switch damping techniques in multimode control. This strategy is derived from the total converted energy of a synchronized switch damping (SSD) system in a given time window. Using the new strategy the voltage is inverted only at those extrema where the effective distance, which is proportional to the converted energy between two neighboring extrema, exceeds the threshold. The new switch control strategy is used in both the synchronized switch damping on inductor (SSDI) technique and the synchronized switch damping on voltage source (SSDV) technique, which are applied to the two-mode control of a composite beam. Their control performances are compared with those of the single-mode control and those of classical SSDI and SSDV techniques in two-mode control. The experimental results show that voltage inversion is prevented at some of the displacement extrema to increase the total converted energy, and exhibit better global damping effect than classical SSDI and classical SSDV, respectively. In single mode, the best control performance is achieved when the voltage is inverted at every extremum. But in multimodal control, the total converted energy in a given time window is increased and the control performance is improved when some extrema are skipped. 相似文献