Topology optimization for designing strain-gauge load cells

Load cells are used extensively in engineering fields. This paper describes a novel structural optimization method for single- and multi-axis load cell structures. First, we briefly explain the topology optimization method that uses the solid isotropic material with penalization (SIMP) method. Next, we clarify the mechanical requirements and design specifications of the single- and multi-axis load cell structures, which are formulated as an objective function. In the case of multi-axis load cell structures, a methodology based on singular value decomposition is used. The sensitivities of the objective function with respect to the design variables are then formulated. On the basis of these formulations, an optimization algorithm is constructed using finite element methods and the method of moving asymptotes (MMA). Finally, we examine the characteristics of the optimization formulations and the resultant optimal configurations. We confirm the usefulness of our proposed methodology for the optimization of single- and multi-axis load cell structures.     

Topology optimization of reflector antennas based on integrated thermal-structural-electromagnetic analysis

Structural and Multidisciplinary Optimization - In the area of structural design of reflector antennas, the existing researches mainly focus on size/shape optimization or just optimizing for...     

Topology optimization of electric machines based on topological sensitivity analysis

Topological sensitivities are a very useful tool for determining optimal designs. The topological derivative of a domain-dependent functional represents the sensitivity with respect to the insertion of an infinitesimally small hole. In the gradient-based ON/OFF method, proposed by Ohtake et al. (IEEE Trans Magn 41(5):1788–1791, 2005), sensitivities of the functional with respect to a local variation of the material coefficient are considered. We show that, in the case of a linear state equation, these two kinds of sensitivities are equivalent provided that the problem is discretized by a low order finite element method on a uniform grid. For the sensitivities computed in the ON/OFF method, the generalization to the case of a nonlinear state equation is straightforward, whereas the computation of topological derivatives in the nonlinear case is ongoing work. We will show numerical results obtained by applying the ON/OFF method to the optimization of an electric motor in the nonlinear case.     

基于在线优化的线性系统状态反馈鲁棒镇定

建立关于Sylvester方程的鲁棒极点配置梯度流优化算法模型,在线求解相应的二次优化问题,并在线计算状态反馈增益矩阵.使得闭环系统矩阵的伞部特征值位于给定的区域中.对于一切满足条件的扰动,具有最小灵敏度,闭环系统人范围一致渐近稳定.仿真结果验证了该方法适用十非线性系统的鲁棒镇定问题和在线鲁棒极点配置问题.     

Support-free robust topology optimization based on pseudo-inverse stiffness matrix and eigenvalue analysis

Structural and Multidisciplinary Optimization - Current finite element analysis (FEA) and optimizations require boundary conditions, i.e., constrained nodes. These nodes represent structural...     

Topology optimization based on level set for a flexible multibody system modeled via ANCF

A topology optimization methodology is proposed for the flexible multibody system undergoing both large overall motion and large deformation. The system of concern is modeled via the absolute nodal coordinate formulation. The equivalent static load method is employed to transform the topology optimization of the nonlinear dynamic response of the system into a static one, and evaluated to adapt to the absolute nodal coordinate formulation by splitting the elastic deformations of the flexible components from the overall motions of those components. During the static topology optimization, the material interface is implicitly described as the zero level set of a higher-dimensional scalar function. Then, the semi-implicit level set method with the additive operator splitting algorithm is employed to solve the corresponding Hamilton-Jacobi partial differential equation. In addition, the expert evaluation method of weights based on the grey theory is utilized to define the objective function, and a modified augmented Lagrange multiplier method is proposed to treat the inequality volume constraint so as to avoid the oscillation and drift of the volume. Finally, two numerical examples are provided to validate the proposed methodology.     

Fine-tuning an aggregated reduced-order model that approximates a linear,time-invariant system

It is shown that the worst-case error bound, previously developed for linear, time-invariant aggregated reduced-order models, can be used to obtain an output matrix that minimizes the model's worse-case output error while holding fixed the coefficient matrices in the model's differential equation. Two example problems are given to illustrate the fine-tuning improvement in the worst-case output error.     

微型磁通门铁芯结构的拓扑分析与优化

多孔铁芯有利于满足微型磁通门传感器降低功耗的要求,但不同的拓扑结构所取得的效果不同,对多孔铁芯结构进行了拓扑分析与针对性优化,并采用微机电系统(MEMS)工艺制备了不同铁芯结构的微型磁通门进行性能测试与对比验证.实验结果证明:优化后的铁芯结构能更好地降低微型磁通门传感器功耗,提高器件整体性能.     

Necessary and sufficient conditions for global optimality of eigenvalue optimization problems

The necessary and sufficient conditions for global optimality are derived for an eigenvalue optimization problem. We consider the generalized eigenvalue problem where real symmetric matrices on both sides are linear functions of design variables. In this case, a minimization problem with eigenvalue constraints can be formulated as Semi-Definite Programming (SDP). From the Karush-Kuhn-Tucker conditions of SDP, the necessary and sufficient conditions are derived for arbitrary multiplicity of the lowest eigenvalues for the case where important lower bound constraints are considered for the design variables. Received May 18, 2000     

Topology optimization based on finite strain plasticity

In this paper infinitesimal elasto-plastic based topology optimization is extended to finite strains. The employed model is based on rate-independent isotropic hardening plasticity and to separate the elastic deformation from the plastic deformation, use is made of the multiplicative split of the deformation gradient. The mechanical balance laws are solved using an implicit total Lagrangian formulation. The optimization problem is solved using the method of moving asymptotes and the sensitivity required to form convex separable approximations is derived using a path-dependent adjoint strategy. The optimization problem is regularized using a PDE-type filter. A simple boundary value problem where the plastic work is maximized is used to demonstrate the capability of the presented model. The numerical examples reveal that finite strain plasticity successfully can be combined with topology optimization.     

Reachability analysis of rational eigenvalue linear systems

One of the key problems in the safety analysis of control systems is the exact computation of reachable state spaces for continuous-time systems. Issues related to the controllability and observability of these systems are well-studied in systems theory. However, there are not many results on reachability, even for general linear systems. In this study, we present a large class of linear systems with decidable reachable state spaces. This is approached by reducing the reachability analysis to real root isolation of exponential polynomials. Furthermore, we have implemented this method in a Maple package based on symbolic computation and applied to several examples successfully.     

An eigenvalue based approach for the robust stabilization of linear time-delay systems

We present a new numerical procedure for the robust stabilization of linear delay differential equations, based on the position of the eigenvalues in the complex plane. We assume static perturbations on the system matrices and express the robustness of the stability in terms of complex stability radii. In the numerical procedure, these stability radii are maximized as a function of the controller parameters. This corresponds to a synthesis problem, which is solved by a quasi-continuous shaping of some frequency response plots. The structure of the algorithm is analogous to the continuous pole placement algorithm for the (non-robust) stabilization of linear delay differential equations.     

Topology optimization of freely vibrating continuum structures based on nonsmooth optimization

The non-differentiability of repeated eigenvalues is one of the key difficulties to obtain the optimal solution in the topology optimization of freely vibrating continuum structures. In this paper, the bundle method, which is a very promising one in the nonsmooth optimization algorithm family, is proposed and implemented to solve the problem of eigenfrequency optimization of continuum. The bundle method is well-known in the mathematical programming community, but has never been used to solve the problems of topology optimization of continuum structures with respect to simple or multiple eigenfrequencies. The advantage of this method is that the specified information of iteration history may be collected and utilized in a very efficient manner to ensure that the next stability center is closer to the optimal solution, so as to avoid the numerical oscillation in the iteration history. Moreover, in the present method, both the simple and multiple eigenfrequencies can be managed within a unified computational scheme. Several numerical examples are tested to validate the proposed method. Comparisons with nonlinear semidefinite programming method and 0–1 formulation based heuristic method show the advantages of the proposed method. It is showed that, the method can deal with the nonsmoothness of the repeated eigenvalues in topology optimization in a very effective and efficient manner without evaluating the multiplicity of the eigenvalues.     

一种基于集中模式的负载分析系统的开发

服务器管理程序应能提供稳定的服务,因此可以开发一种新的基于集中模式的分析系统来协助管理程序来管理分布式服务。该系统可以使管理程序监测服务器的状态,并进一步检测系统是否因请求过多而过载,并能降低与管理有关的开销。     

基于汇聚流回推的DDoS防御系统

提出了一种基于汇聚流回推的DDoS(Distributed Denial of Setvice)综合防御方案。此方案对本地路由器上的汇聚流及其上游汇聚流回推树上第n层路由器上的汇聚流进行分布限速,以达到抵御DDoS攻击的目的。给出了汇聚流限流算法和回推汇聚流所需的反向汇聚流往返树的构建算法。汇聚流限流算法旨在最大限度地限制DDoS流,同时保护正常的用户流。反向汇聚流往返树的构建算法通过动态地探测高流量的汇聚流路径,将自动生成回推汇聚流所需的反向汇聚流往返树。     

Topology optimization of hyperbolic metamaterials for an optical hyperlens

This paper presents a level set-based topology optimization method for the microstructural design of an optical hyperlens. The resolution of conventional optics is generally diffraction limited, but the diffraction limit can be overcome by a hyperlens that converts evanescent waves to propagation waves, utilizing a cylindrical geometry to magnify the subwavelength features of imaged objects, which allows such features to be resolved beyond the diffraction limit at the hyperlens output. To support electromagnetic waves that contain information of subwavelength features, the hyperlens must have material properties that include a positive permittivity in the angular direction and a negative permittivity in the radial direction. Here, an energy-based homogenization method is used to obtain the effective permittivity of a metamaterial hyperlens unit cell. A level set-based topology optimization is applied so that the boundaries of the structure are clearly expressed. Moreover, a finite element mesh regeneration scheme is used to precisely capture the boundaries of the metal and dielectric materials of the unit cell that will ultimately form the hyperlens. The optimization algorithm uses the finite element method (FEM) to solve the equilibrium and adjoint equations. Optimum design examples for the design of a hyperlens microstructure are provided to confirm the utility and validity of the presented method.     

Topology optimization for designing periodic microstructures based on finite strain viscoplasticity

Structural and Multidisciplinary Optimization - This paper presents a topology optimization framework for designing periodic viscoplastic microstructures under finite deformation. To demonstrate...     

基于声灵敏度的车身拓扑优化

为探讨板件结构对车内噪声的影响,建立某商务车的白车身有限元模型,分析其模态和车身声灵敏度,确定对汽车低频振动和噪声影响较大的板件;结合变密度法在整车环境下对板件进行减振降噪的拓扑优化,根据拓扑优化结果对板件进行结构修改. 优化后的车身声灵敏度曲线与原车身声灵敏度曲线相比,低频范围内的峰值都有不同程度的降低,表明结合整车动态响应的汽车板件结构拓扑优化可以有效降低车内低频振动噪声.     

基于JavaScript的生物信息学分析系统的优化和扩展

对基于JavaScript的SMS核酸和蛋白质序列分析系统进行了改进,汉化并优化了系统界面,对系统中多序列同源性分析和引物搜索设计进行了较大幅度的改进,以提高精确度和实用性,增加了基于JavaScript的蛋白质理化性质曲线分析功能。为生物信息学和生物序列研究提供了更为有效的工具。     

基于JavaScript的生物信息学分析系统的优化和扩展

对基于JavaScript的SMS核酸和蛋白质序列分析系统进行了改进，汉化并优化了系统界面，对系统中多序列同源性分析和引物搜索设计进行了较大幅度的改进，以提高精确度和实用性，增加了基于JavaScript的蛋白质理化性质曲线分析功能。为生物信息学和生物序列研究提供了更为有效的工具。