水声基阵波束图分析与优化设计软件

介绍西北工业大学开发的水声基阵波束分析与优化设计软件.该软件针对给定的基阵形式,可以设计期望的波束图,然后通过优化方法获得最优的波束形成权系数.同时软件还可以分析水声基阵的常规波束图和最优波束图,并计算波束图的主瓣宽度、旁瓣级、栅瓣位置、指向性指数等主要指标.软件中考虑的基阵形式主要有直线阵、圆阵、圆柱阵、平面阵、球阵、体积阵等.本软件的有效性通过波束优化设计与分析实例得到了验证.     

麦克风基阵结构的噪声源识别性能研究

为更好地应用麦克风阵列识别噪声源位置,本文针对多种不同基阵结构的噪声源识别性能展开研究.基于"延时-累加"波束形成原理建立了平面任意麦克风基阵结构的数学计算模型,并给出了麦克风基阵声源定位的通用计算方程组;分别推导分析了二元、三元及四元基阵的定位算法公式,并对三元基阵给出了其矩阵解.分析比较不同类型的麦克风基阵结构对噪声源的识别性能影响.通过建立由不同形式基阵构成的同等规模小型麦克风阵列,进行噪声源识别对比测试,最终的测试结果验证了本文所提出模型及算法的可靠性,并得出由正三元基阵构成的麦克风阵列结构具有较好的噪声源识别性能的结论.     

纸浆模塑缓冲包装结构参数的稳健性分析

针对纸浆模塑缓冲包装结构参数对缓冲性能的影响程度,引入基于实验设计的稳健性实验设计方法,探讨了纸浆模塑缓冲包装结构的厚度、斜度、缓冲高度和接触边长对缓冲性能的影响程度.此研究结果为缓冲包装结构的设计提供一定参考.     

基于阵列响应向量估计的宽容体积阵波束形成

0引言波束形成作为声纳系统的重要组成部分,直接影响着整体性能。通过优化波束形成权系数,为系统提高检测概率,精确定位、跟踪、识别搭建了良好的平台。然而这些优化设计都是在理想阵列流形的假设下进行的,权系数对误差比较敏感,如果实际的阵列流形发生失配时优化波束的效果将急剧降低。在体积阵中产生阵流形失配的原因有很多,     

一种换能器基阵的测量分析

水声换能器基阵的波束宽度及束控是声呐水下分机的重要性能要求,它又是影响声呐设备总体性能的重要指标;本文主要介绍一种仿制换能器基阵单元波束宽度及束控后波束宽度的测量。     

近场波束形成的约束最小平方和法

文章研究了近场情况下的波束形成问题。对于任意结构阵列,提出了近场波束形成的一种约束最小平方和法,用近场信号模型来设计近场波束。该方法借助于优化工具箱,在对波束旁瓣施加约束的条件下,使波束主瓣的误差平方和最小。该方法在主瓣区域和旁瓣区域都能得到满足设计要求的波束性能,可以方便地控制期望响应,简单易行。基于32元均匀离散圆阵的仿真设计结果表明了文中方法的有效性。     

考虑材料参数不确定性结构动力学稳健性拓扑优化设计

本文在考虑材料参数不确定性的条件下,对连续体结构动力学稳健性拓扑优化设计进行研究。在使结构的第一阶固有频率最大化的同时,显著减小其对材料性能不确定性的影响。基于非概率凸集模型,将材料参数的不确定性用有界区间变量表示;建立了能够抑制频率改变的结构动力学拓扑优化模型,用单层优化策略求解稳健性优化设计问题。通过对材料参数的导数分析,获得了在材料性能不确定情形下结构第一阶固有频率的二阶泰勒展开式,并推导出了频率对拓扑变量的一阶灵敏度显性表达式。基于变密度法,开展了结构动力学稳健性拓扑优化设计,并与确定性优化结果进行对比,验证了用本文方法获得的结构第一阶固有频率稳健性更高,受材料参数不确定性扰动影响更小,展示了考虑材料参数不确定性的重要性。     

采用约束最小平方和法实现近场波束形成

本文研究了近场情况下的波束形成问题。对于任意结构阵列,提出了实现近场波束形成的一种约束最小平方和法,由近场信号模型来设计近场波束。该方法在对波束旁瓣施加约束的条件下,使波束主瓣的误差平方和最小,可借助于优化工具箱实现。该方法在主瓣区域和旁瓣区域都能得到满足设计要求的波束性能,不仅可以方便地控制期望响应,而且简单易行。基于32元均匀离散圆阵的仿真设计结果表明了本文方法的有效性。     

多响应问题的稳健性设计优化

基于双响应曲面方法提出了一种解决多响应稳健设计的优化方案。对多响应稳健设计优化问题进行分析,提出了双响应曲面方法与满意度函数法相结合的稳健优化设计方法。该方法通过引入多响应均值满意度和多响应方差满意度,将可控因素和噪声因素的波动产生的方差结合到满意度函数中,并考虑了优化结果的稳健性。采用该方法对文献实例进行分析,得到了较好的优化结果。     

基于主成分分析的多响应稳健性优化方法研究

将主成分分析法与双响应曲面法相结合,提出了一种同时优化响应均值和标准差的多响应优化方法.通过主成分分析,将多个响应的位置和散布特性值转化为主成分综合得分,并以二者的加权和作为优化指标,克服了传统的多响应优化方法只考虑响应均值的不足,将响应的标准差也纳入优化范畴,实现优化的稳健性.实例表明,该方法充分考虑了响应标准差对优化结果的影响,优化结果得到一定改善.     

Experimental stress analysis of an arbitrary geometry containing irregularly shaped hole

Stresses can significantly influence the mechanical integrity of engineering structures. Motivated by prevalence of members containing cutouts, the objective of this paper is to demonstrate ability to stress analyse a finite, complicated‐shaped plate containing an asymmetrical, irregularly shaped hole. Combining the load‐induced temperature information with analytical and numerical tools provides the independent stresses full field, including on edges of the plate and adjacent to the top load. In addition to utilising real, rather than complex, variables, the technique smooths the recorded information, evaluates individual stresses, and requires neither differentiating the measured data nor knowing the elastic properties. Results are supported by those from a finite element analysis, force equilibrium, and strain gages.     

高强钢控制臂件冲压工艺优化及稳健性分析

为获得高强钢控制臂件冲压工艺参数最优解,提高冲压工艺稳健性,基于6sigma稳健设计理论,采用数值模拟方法分析预成形模具间隙、局部翻边模间隙、预成形压边力、摩擦系数、板料轮廓尺寸等对拐角处材料减薄率的影响规律;将坯料位置、料片厚度、摩擦系数、塑性应变比、屈服强度、抗拉强度、板料尺寸等作为噪声变量输入,分析工艺的稳健性;根据敏感性分析结果,选用局部翻边模间隙、预成形模具间隙为变量,3σ水平设为目标,成形过程能力Cp值为1.0,进行优化计算;最后采用优化后的局部翻边模间隙、预成形模具间隙值,其他噪音变量不变,再次进行稳健性分析.研究发现,影响控制臂局部过度减薄甚至开裂的主要因素为预成形模具间隙及局部翻边模具间隙.根据模拟结果试模,零件的壁厚分布与模拟结果相比,最大误差小于6%.通过对关键参数的敏感性分析以及考虑噪声因素的稳健性分析,优化工艺参数后,成形质量水平提高,成形结果可靠.     

A functional for shells of arbitrary geometry and a mixed finite element method for parabolic and circular cylindrical shells

In this study a higher‐order shell theory is proposed for arbitrary shell geometries which allows the cross‐section to rotate with respect to the middle surface and to warp into a non‐planar surface. This new kinematic assumption satisfies the shear‐free surface boundary condition (BC) automatically. A new internal force expression is obtained based on this kinematic assumption. A new functional for arbitrary shell geometries is obtained employing Gâteaux differential method. During this variational process the BC is constructed and introduced to the functional in a systematic way. Two different mixed elements PRSH52 and CRSH52 are derived for parabolic and circular cylindrical shells, respectively, using the new functional. The element does not suffer from shear locking. The excellent performance of the new elements is verified by applying the method to some test problems. Copyright © 2000 John Wiley & Sons, Ltd.     

On the robustness and efficiency of the SAM algorithm for structural optimization

A parameter study involving a feasibility factor, adaptive tolerance refinement and active set and move limits is conducted on the interior feasible direction method with successive approximations (SAM). The study involves the sizing design of five structural problems of which one is a large power transmission tower to be designed in adherence with a standard design code. It is concluded that a move limit is dispensable for this application while adaptive tolerance refinement makes the algorithm more efficient. Optimal ranges for the feasibility factor and active set limits are suggested. This study reaffirms and quantifies the exceptional stability and robustness of the SAM algorithm.     

Frequency domain analysis for stability robustness of multivariable feedback systems

Abstract

This paper presents techniques for analyzing stability robustness of multivariable control systems. The upper bounds for each element of the allowable perturbation matrices can be obtained whether highly structural information is available or not. Approaching from testing the nonsingularity of a matrix by its eigenvalues instead of using matrix norms, the main algorithm involved is the computation of the spectral radii of certain nonnegative matrices. Due to the fact that any matrix norm is never less than the spectral radius of the same matrix, less conservative results are obtained using our criteria as compared with those obtained by utilizing matrix norms.     

A graph‐based postoptimization approach for covering arrays

Covering arrays (CAs) are combinatorial objects with interesting features that have practical applications such as experimental design and fault detection in hardware and software. We introduce a graph‐based postoptimization (GBPO) approach to reduce the size of CAs exploiting the redundancy in CAs previously constructed. To evidence the advantages of using GBPO, we have instantiated it with 2 sets of CAs: (1) 560 CAs of strength 2≤t≤6, alphabet 2≤v≤6, and parameters 3≤k≤32 generated by an optimized version of In‐Parameter‐Order‐Generalized (IPOG‐F) and GBPO improved all CAs, and 37 cases matched the best‐known upper bounds; and (2) 32 CAs of strength t=2, alphabet 3≤v≤6, and number of parameters 8≤k≤146; in this set, 16 cases were improved, and 16 cases were matched.     

Development of a simple and efficient method for robust optimization

Robust optimization problems are newly formulated and an efficient computational scheme is proposed. Both design variables and design parameters are considered as random variables about their nominal values. To ensure the robustness of objective performance, we introduce a new performance index bounding the performance together with a constraint limiting the performance variation. The constraint variations are regulated by considering the probability of feasibility. Each probability constraint is transformed into a sub‐optimization problem by the advanced first‐order second moment (AFOSM) method for computational efficiency. The proposed robust optimization method has the advantages that the mean value and the variation of the performance function are controlled simultaneously and rationally and the second‐order sensitivity information is not required even in case of gradient‐based optimization process. The suggested method is examined by solving three examples and the results are compared with those for the deterministic case and those available in the literature. Copyright © 2002 John Wiley & Sons, Ltd.     

On stress singularities at angular corners of plates of arbitrary thickness under tension

Stress singularities at angular corners of plates of arbitrary thickness with free boundaries subjected to in-plane loading are studied within the first order plate theory. By adapting a stress resultant function approach a characteristic equation for determining the structure and orders of the singularities near the vertex is developed. This equation differs from that obtained within the classical plane theory of elasticity (Williams solution) and includes singularities of the out-off-plane shear stress resultants.     

钢铝板材压力连接模具几何参数多目标优化

为解决钢铝混合车身中钢和铝异种材料间的连接问题,对无铆钉自冲铆连接钢铝异种材料的可行性进行了实验研究和仿真分析.在实验验证的基础上,为得到连接接头处的最优机械性能,以接头颈厚值和自锁值为评价指标,综合运用实验设计、统计分析、代理模型构造响应面以及遗传算法对钢铝压力连接模具几何参数进行多目标优化,得到了接头颈厚值和自锁值...