Topology synthesis of electrothermal compliant mechanisms using line elements

This paper presents a line-element-based approach to the topology synthesis of electrothermal compliant (ETC) mechanisms. A line element is a one-dimensional model of the electrical, thermal, and elastic behavior of a beam-like continuum. In contrast to topology synthesis of ETC mechanisms by a continuum-element-based approach, the line-element-based approach offers significant conceptual and practical advantages. The line element allows for straightforward modeling of surface heat transfer in the topology optimization framework. It also obviates the need to interpolate electrical and thermophysical properties in the topology synthesis procedure. Moreover, this approach results in clean geometries that are easy to fabricate directly in their optimized form. Solutions obtained from this procedure are compared with results from continuum-based optimal synthesis procedures as well as intuitive designs reported in the literature. A number of design examples are used to demonstrate the ability of the procedure to generate nonintuitive topologies. The synthesis procedure is also used to study the influence of the direction of output and the electrical and thermal resistance of the workpiece on the resulting optimal topologies.     

Two-stage compliant microleverage mechanism optimization in a resonant accelerometer

Compliant microleverage mechanisms can be used in micro-electro-mechanical systems (MEMS) to transfer an input force/displacement to an output to achieve mechanical/geometrical advantages. By stacking multiple stages of microlevers together, a compound microleverage mechanism is obtained with a higher amplification factor. This paper presents the analysis and optimization of a two-stage microleverage mechanism in a resonant output micro-accelerometer for force amplification. It is found that the compliance of the two-stage mechanism needs to be appropriately distributed in order for both stages to have the desired amplification effect. June 13, 2000     

Applications of regional strain energy in compliant structure design for energy absorption

Topology optimization of regional strain energy is studied in this paper. Unlike the conventional mean compliance formulation, this paper considers two main functions of structure: rigidity and compliance. For normal usages, rigidity is chosen as the design objective. For compliant design, a portion of the structure absorbs energy, while another part maintains the structural integrity. Therefore, we implemented a regional strain energy formulation for topology optimization. Sensitivity to regional strain energy is derived from the adjoint method. Numerical results from the proposed formulation are presented.     

Topology optimization of structures with integral compliant mechanisms for mid-frequency response

The purpose of this paper is to present a method for developing new truss-like sandwich structures that exhibit desirable mid-frequency vibratory characteristics. Specifically, a genetic algorithm optimization routine is used to determine candidate small scale structural topologies, i.e. unit cells, that may be used in the design of larger scale periodic sandwich structures. This multi-scale procedure is demonstrated starting with several unit cell topology optimization examples. From these examples a specific optimal unit cell is selected for further investigation and integration into a periodic sandwich beam. Computational results indicate that the proposed optimization approach is effective when used to design new structures for reduced mid-frequency vibratory response.     

物质点拓扑变量法在柔性机构设计中的应用

为克服柔性机构拓扑优化设计中的各类数值不稳定性问题,提出一种以物质点拓扑变量为设计变量的拓扑优化方法.物质点拓扑变量可视为节点密度概念的进一步拓展,基于修正网格无关性过滤函数提出了新的拓扑变量场插值形函数.基于弹簧模型,建立了柔性机构的多约束拓扑优化模型,推导了常见结构响应量的敏度表达式,采用移动渐进线法进行优化求解.最后通过二维数值算例验证了文中方法的可行性和有效性.     

压电智能结构的主动控制及压电执行器布局优化

本文对压电梁、板结构振动主动控制进行了研究,分别建立了压电悬臂梁的耦合动力学方程以及Kirchhoff假设下矩形压电薄板的耦合动力学方程,通过采用独立模态空间控制法,实现了对压电智能结构前两阶模态的主动振动控制.为提高主动控制的抑振效果,通过仿真实例分析了压电执行器在梁上的不同布局对于主动控制抑振效果的影响,得到了压电执行器粘附于悬臂梁上的最佳布局.最后实验验证了压电悬臂梁在自由振动以及模态共振下压电执行器对于悬臂梁响应控制的可行性和有效性.     

压电作动器的动态迟滞建模与H∞鲁棒控制

压电作动器具有率相关动态迟滞非线性特性,给传统建模和控制技术提出了挑战.本文针对压电作动器,提出了一种基于Bouc-Wen的Hammerstein率相关迟滞非线性模型,其中Bouc-Wen模型和线性动态模块分别用于描述系统的静态迟滞非线性特性和率相关特性.同时,构造了一个基于Bouc-Wen模型的迟滞补偿器,将迟滞补偿器与被控对象串联使系统线性化;并建立了不确定性系统模型,提出了一种H∞鲁棒跟踪控制方案,可以实现给定频率范围内单频率和复合频率参考信号的良好跟踪.实验结果表明,所建动态模型具有良好的泛化能力,跟踪控制相对误差小于8%,证明了所提出方法的有效性.     

Topology optimization of continuum structures subjected to pressure loading

This paper presents a generalization of topology optimization of linearly elastic continuum structures to problems involving loadings that depend on the design. Minimum compliance is chosen as the design objective, assuming the boundary conditions and the total volume within the admissible design domain to be given. The topology optimization is based on the usage of a SIMP material model. The type of loading considered in this paper occurs if free structural surface domains are subjected to static pressure, in which case both the direction and location of the loading change with the structural design. The presentation of the material is given in a 2D context, but an extension to 3D is straightforward. The robustness of the optimization method is illustrated by some numerical examples in the end of the paper. Received August 3, 1999