Impedance Losses in Negative Capacitance Circuits for Semi-Passive Vibration Control with Piezo-Ceramics

Damping or absorbing effect in vibration control applications with piezo elements may be customized by an external impedance shunt branch connected to the plates of the piezo element. The negative capacitance present in the shunt significantly improves the damping and absorbing performance of such systems. The circuit is built up of an electronic gyrator realized by the operational amplifier, which is in reality not the ideal element. Therefore the performance of the proposed systems is limited, concerning the maximum voltages and currents at which the operational amplifiers can operate. In the paper, the finite gain of the operational amplifier, together with the loss impedances and the feedback gain factor is studied. The influence of the certain imperfections in the design of the electronic gyrator is based on 1DOF mechanical oscillator, with a piezo stack. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Impedance Passive and Conservative Boundary Control Systems

The external Cayley transform is used for the conversion between the linear dynamical systems in scattering form and in impedance form. We use this transform to define a class of formal impedance conservative boundary control systems (colligations), without assuming a priori that the associated Cauchy problems are solvable. We give sufficient and necessary conditions when impedance conservative colligations are internally well-posed boundary nodes; i.e., when the associated Cauchy problems are solvable and governed by C ₀ semigroups. We define a “strong” variant of such colligations, and we show that “strong” impedance conservative boundary colligation is a slight generalization of the “abstract boundary space” construction for a symmetric operator in the Russian literature. Many aspects of the theory is illustated by examples involving the transmission line and the wave equations. Received: August 21, 2006. Accepted: October 22, 2006.     

A Heuristic for the Control of Inventory in a Multi-echelon Environment with Transportation Costs and Capacity Limitations

This paper develops, demonstrates and tests a heuristic procedure for controlling finished goods in a multi-echelon environment where there are significant transportation costs and capacity limitations on storage and transportation resources. This overall problem can be formulated as a large, mixed-integer linear programme (MILP), but solving such a model for practical-sized problems is costly and time-consuming, or even impossible, given computer systems typically used by businesses. Instead, the MILP formulation is used to both motivate and provide a benchmark for testing the performance of the heuristic procedure developed in this paper. When compared to the optimal results from the MILP, the cost performance of the heuristic procedure is found to be excellent.     

Modeling of Active Noise and Vibration Control with Finite Elements and Boundary Elements

A recently developed coupled finite element-boundary element modeling scheme for the design of active noise and vibration control of multi-coupled structural-acoustic systems is presented. The approach allows the computation of structural vibrations and resulting sound fields. By means of an example, the paper describes the theoretical background of the coupled approach. In order to show the performance of the developed approach, test simulations are carried out in the frequency domain. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

集成结构振动主动控制和抑制

采用一种新的压电板单元,建立了含有分布压电传感元件和执行元件的集成结构的有限元动力模型。研究了这种集成结构在常增益负速度反馈控制规律作用下,振动的主动控制与抑制的问题,并提出了集成结构振动主动控制和抑制的一般方法。最后,提供了数值示例,说明本文提出方法的有效性。     

非线性梁结构的参数振动稳定性及其主动控制

采用压电材料研究了参数激励非线性梁结构的运动稳定性及其主动控制,通过速度反馈控制算法获得主动阻尼,利用Hamilton原理建立含阻尼的立方非线性运动方程,采用多尺度方法求解运动方程获得稳定性区域．通过数值算例,分析了控制增益、外激振力幅值等因素对稳定性区域和幅频曲线特性的影响．分析表明:控制增益增大,结构所能承受的轴向力也增大,在一定范围内结构的主动阻尼比也增加;随着控制增益的增大,响应幅值逐渐降低,但所需的控制电压存在峰值点．     

Diffraction of Electromagnetic Waves on an Impedance Interface between Two Media with Different Perturbations in Impedance

The problem on the diffraction of the electromagnetic plane wave on the impedance interface between two media is investigated. The impedance is assumed to be different from a constant on a segment of the interface, where the impedance is described by piecewise-linear, quadratic, or step functions. Bibliography: 4 titles.     

Active Vibration Damping and Model-Based Control for an Adaptronic Actuator

The static and dynamic flexibility of a machine tool is often the major limiting factor for the machining quality, especially if high processing speeds as well as high accuracies are desired. Particularly parallel kinematic machines, which have been developed for high processing speeds and accuracy and which often use lightweight structures, can suffer from severe problems with vibrations of system components and the loss of accuracy due to deformations of machine parts. Introducing so–called adaptronic or smart components into the machine tool structure opens up new and interesting possibilities to actively control the deformations and vibrations of flexible machine parts. They allow to specifically target such undesired properties and to significantly reduce or even eliminate their influence on the system performance. Concepts of active vibration damping and model–based control are presented here for such an adaptronic actuator implemented in a machine tool with parallel kinematics. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

具有主动约束层阻尼板的振动杂交控制*

本文研究了局部附加主动约束阻尼层(LACL)板的主、被动杂交控制问题.基于弹性、粘弹性、压电材料的本构关系,建立了系统的控制方程.利用Galerkin方法和GHM方法将偏微分方程转换为维数不高的常微分方程组,应用LQR方法进行了数值模拟.计算结果表明,这种主动和被动结合的杂交控制方式具有良好的控制效果.     

Circuits and Cocircuits in Regular Matroids

A classical result of Dirac's shows that, for any two edges and any n−2 vertices in a simple n-connected graph, there is a cycle that contains both edges and all n−2 of the vertices. Oxley has asked whether, for any two elements and any n−2 cocircuits in an n-connected matroid, there is a circuit that contains both elements and that has a non-empty intersection with all n−2 of the cocircuits. By using Seymour's decomposition theorem and results of Oxley and Denley and Wu, we prove that a slightly stronger property holds for regular matroids.     

Efficiency and Optimality in Minisum,Minimax 0-1 Programming Problems

Inspired by an increasing interest in multicriteria 0-1 programming problems in general and by a recent result on the reducibility of minimax to minisum problems in particular, we consider properties of efficient and optimal solutions to two-criteria (minisum and minimax) 0-1 programming problems with any constraint set.A solution procedure is suggested for solving problems whose objective functions are a convex combination of these criteria. The solution properties are illustrated with examples mainly within the context of locational decision problems.     

弹性振动点观测反馈控制古典解的存在性

本文运用有界线性算子的积分半群理论证明弹性振动点观测反馈控制方程古典解的存在性     

反常积分号下取极限的两个定理及应用

针对n→∞时相应反常积分的极限介绍两个有用的定理,特别是积分形式的Tannery定理,这在现有的文献中很少见到.这些结果有助于完善教材相关内容.最后给出了几个应用例子.     

兼顾效率和成本的ARMA控制图多目标优化设计

ARMA控制图是一种有效的自相关过程质量监控方法,为了能够同时对ARMA控制图监控方案的效率和成本进行优化,本文分别研究了ARMA控制图的平均运行长度和质量成本的计算方法,并由此建立了ARMA控制图的多目标优化设计模型。采用NSGA-Ш智能优化算法,通过一个具体的算例对该模型的计算方法进行了说明,针对不同程度的过程偏移给出了多目标优化设计的非劣解解集。然后通过灵敏度分析的方法研究了模型中的主要设计参数对监控方案的效率和成本的影响程度。最后,通过与其它几种ARMA控制图优化设计方案的比较分析,说明了本文提出的设计方法的优势。     

Scheduling Jobs of Equal Durations with Tardiness Costs and Resource Limitations

In this paper it is shown that the combinatorial problem of scheduling jobs of equal duration with tardiness costs and resource limitations can be solved by formulating the problem as a classical transportation model which is here highly degenerate. A new algorithm derived from the classical stepping stone method is given. The algorithm produces a strict decrease of the objective at each iteration. A special case which could be called the simplest problem of scheduling is also studied.     

Exterior Wedge Diffraction Problems with Dirichlet,Neumann and Impedance Boundary Conditions

Classes of problems of wave diffraction by a plane angular screen occupying an infinite 270 degrees wedge sector are studied in a Bessel potential spaces framework. The problems are subjected to different possible combinations of boundary conditions on the faces of the wedge. Namely, under consideration there will be boundary conditions of Dirichlet-Dirichlet, Neumann-Neumann, Neumann-Dirichlet, impedance-Dirichlet, and impedance-Neumann types. Existence and uniqueness results are proved for all these cases in the weak formulation. In addition, the solutions are provided within the spaces in consideration, and higher regularity of solutions are also obtained in a scale of Bessel potential spaces.     

Existence and Uniqueness for a Linear Mixed Variational Inequality Arising in Electrical Circuits with Transistors

The main object of this paper is to present an existence and uniqueness result for a class of variational inequalities which is of particular interest to study electrical circuits involving devices like transistors.     

A Coupled FE-BE Analysis of Smart Lightweight Structures for Active Noise and Vibration Control

Over the past years much research and development has been done in the area of active control in order to improve the acoustical and vibrational properties of thin–walled lightweight structures. An efficient technique for actively reducing the structural vibration and sound radiation is the application of smart structures. In smart structures piezoelectric materials are often used as actuators and sensors. The design of smart structures requires fast and reliable simulation tools. Therefore, the purpose of this paper is to present a coupled finite element–boundary element formulation, which enables the modeling of piezoelectric smart lightweight structures. The paper describes the theoretical background of the coupled approach in which the finite element method (FEM) is applied for the modeling of the passive vibrating shell structure as well as the surface attached piezoelectric actuators and sensors. The boundary element method (BEM) is used to characterize the corresponding sound field. In order to derive a coupled FE–BE formulation additional coupling conditions are introduced at the fluid–structure interface. Since the resulting overall model contains a large number of degrees of freedom, the mode superposition method is employed to reduce the size of the FE submodel. To validate the accuracy of the proposed approach, numerical simulations are carried out in the frequency domain and the results are compared with analytical reference solutions. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)