A novel technique for optimal placement of piezoelectric actuators on smart structures

The problem of positioning of actuators and sensors on smart materials has been a point of interest in recent years. This is due to the fact that in many practical applications there are limitations in space, weight, etc. of the smart structures, which make the problem of positioning more complex. In addition, it is required that the actuators/sensors have the best possible performance. The development of smart structures technology in recent years has provided numerous opportunities for vibration control applications. The use of piezoelectric ceramics or polymers has shown great promise in the development of this technology. The employment of piezoelectric material as actuators in vibration control is beneficial because these actuators only excite the elastic modes of the structures without exciting the rigid-body modes. This is important since very often only elastic motions of the structures are needed to be controlled. The purpose of this paper is to introduce a novel approach developed for optimizing the location of piezoelectric actuators for vibration suppression of flexible structures. A flexible fin with bonded piezoelectric actuators is considered in this study. The frequency response function (FRF) of the system is then recorded and maximization of the FRF peaks is considered as the objective function of the optimization algorithm to find the optimal placement of the piezoelectric actuators on the smart fin. Three multi-layer perceptron neural networks are employed to perform surface fitting to the discrete data generated by the finite element method (FEM). Invasive weed optimization (IWO), a novel numerical stochastic optimization algorithm, is then employed to maximize the weighted summation of FRF peaks. Results indicate an accurate surface fitting for the FRF peak data and an optimal placement of the piezoelectric actuators for vibration suppression is achieved.     

Generic two-degree-of-freedom linear and fuzzy controllers for integral processes

This paper presents a new framework for the design of generic two-degree-of-freedom (2-DOF), linear and fuzzy, controllers dedicated to a class of integral processes specific to servo systems. The first part of the paper presents four 2-DOF linear PI controller structures that are designed using the Extended Symmetrical Optimum method to ensure the desired overshoot and settling time. The second part of the paper presents an original design method for 2-DOF Takagi-Sugeno PI-fuzzy controllers based on the stability analysis theorem. Experimental results for the speed control of a servo system with variable load illustrate the performance of the new generic control structures.     

Active vibration control of an elastically connected double-string continuous system

The paper deals with the optimal control of a distributed host structure consisting of two elastically connected complex continuous double-string system and subjected to certain excitation load. Investigation of the behavior of such system is of great theoretical and practical importance. A technique is proposed to actively damp out the undesired vibrations in the structures by a combination of applied actuators and displacement feedback gains. Two performance measures, involving energies at the terminal time as well as applied and feedback control efforts, are introduced. The optimality conditions of the applied actuators are derived by using the method of eigenfunction expansion and calculus of variations. The feedback parameters are numerically determined from the solution of a minimization problem. The proposed approach is illustrated by a numerical example involving a system which consists of two strings subjected to a continuous load.     

The solutions of vibration control problems using artificial neural networks

This paper introduces an alternative method artificial neural networks (ANN) used to obtain numerical solutions of mathematical models of dynamic systems, represented by ordinary differential equations (ODEs) and partial differential equations (PDEs). The proposed trial solution of differential equations (DEs) consists of two parts: The initial and boundary conditions (BCs) should be satisfied by the first part. However, the second part is not affected from initial and BCs, but it only tries to satisfy DE. This part involves a feedforward ANN containing adjustable parameters (weight and bias). The proposed solution satisfying boundary and initial condition uses a feedforward ANN with one hidden layer varying the neuron number in the hidden layer according to complexity of the considered problem. The ANN having appropriate architecture has been trained with backpropagation algorithm using an adaptive learning rate to satisfy DE. Moreover, we have, first, developed the general formula for the numerical solutions of nth-order initial-value problems by using ANN.For numerical applications, the ODEs that are the mathematical models of linear and non-linear mass-damper-spring systems and the second- and fourth-order PDEs that are the mathematical models of the control of longitudinal vibrations of rods and lateral vibrations of beams have been considered. Finally, the responses of the controlled and non-controlled systems have been obtained. The obtained results have been graphically presented and some conclusion remarks are given.     

A matrix-based approach to verifying stability and synthesizing optimal stabilizing controllers for finite-state automata

In this paper, we develop a matrix-based methodology to investigate the problems of stability and stabilizability for a deterministic finite automaton (DFA) in the framework of the semi-tensor product (STP) of matrices. First, we discuss the equilibrium point stability (resp., set stability) of a DFA, i.e., verifying whether or not all state trajectories starting from a subset of states converge to a specified equilibrium point (resp., subset of states). The necessary and sufficient conditions for verifying both stabilities are given, respectively. Second, equilibrium point stabilizability (resp., set stabilizability) of a DFA is investigated as verifying the issue of whether or not a DFA can be globally or locally stabilized to a specified equilibrium point (resp., subset of states) by a permissible state-feedback controller. Based on the pre-reachability set and invariant-subset defined in this paper, the matrix-based criteria for verifying equilibrium point stabilizability and set stabilizability are derived, respectively. Furthermore, for each type of stabilizability, all permissible state-feedback controllers for the case of minimal length state trajectories, called optimal state-feedback controllers, are characterized by using the proposed polynomial algorithms. Finally, two examples are presented to illustrate the effectiveness of the theoretical results.     

A comparative study of vibration isolation performance using negative stiffness and inerter dampers

Two types of passive devices, namely, negative stiffness damper (NSD) and inerter damper (ID), have been receiving growing interest in vibration isolation and suppression, because both can produce negative-slope force-displacement relationships that are similar to those associated with active control forces. Despite such a similarity, these two passive dampers possess obvious differences in their mechanical behaviors. This study aims to illustrate the similarity and difference between these two dampers in vibration isolation applications with respect to the H₂ and H_∞ performance. The comparative study indicates that both dampers can reduce the H_∞ norm effectively; the negative stiffness devices can reduce the H₂ norm as well, whereas the H₂ norm cannot converge under the influence of inerter. This finding explains why a tuned-inerter damper, i.e., an inerter connected in series with a spring with proper frequency tuning, is more commonly adopted in vibration isolation. The pros and cons of both devices were further discussed.     

Bond graph formulation of an optimal control problem for linear time invariant systems

A recent communication has proposed a conjectural procedure for representing a category of optimal control problems in bond graph language [W. Marquis-Favre, B. Chereji, D. Thomasset, S. Scavarda, Bond graph representation of an optimal control problem: the dc motor example, in: ICBGM’05 International Conference of Bond Graph Modelling and Simulation, New Orleans, USA, January 23-27, 2005, pp. 239-244]. This paper aims at providing a fundamental theory for proving the effectiveness of this procedure. The class of problem that the procedure can deal with has been extended. Its application was formerly restricted to linear time invariant siso system. The systems considered now are linear time invariant mimo systems. The optimization objective is the minimization of dissipation and input. The developments concerning the optimal control problem are based on the Pontryagin maximum principle and the proof of the effectiveness of the procedure makes a broad use of the port-Hamiltonian concept. As a result, the bond graph representation of the given optimization problem enables the analytical system, which provides the optimal solution, to be derived. The work presented in this paper is the first step in research with perspectives towards formulating dynamic optimization problems in bond graph and, towards coupling this formulation with a sizing methodology using bond graph language and a state-space inverse model approach. This sizing methodology, however, is not the topic of this paper and thus is not presented here.     

Numerical solutions of optimal control for linear time-varying systems with delays via hybrid functions

By applying hybrid functions of general block-pulse functions and Legendre polynomials, the linear-quadratic problem of linear time-varying systems with delays are transformed into the optimization problem of multivariate functions. The approximate solutions of the optimal control and state as well as the optimal value of the objective functional are derived. The numerical examples illustrate that the algorithms are valid.     

Interference suppression of linear antenna arrays by phase-only control using a clonal selection algorithm

In this paper, an efficient technique based on clonal selection algorithm (CLONALG) for linear antenna array pattern synthesis with null steering by controlling only the element excitation phases is presented. The CLONALG is an evolutionary computation method inspired by the clonal selection principle of human immune system. To show the versatility and flexibility of the proposed CLONALG, some examples of Chebyshev array pattern with the imposed single, multiple and broad nulls are given. The sensitivity of the nulling patterns due to small variations of the element phases is also investigated.     

Robust stable pole-placement-based adaptive control of continuous linear systems with two parametrical estimation schemes

This paper deals with the pole-placement-type robust adaptive control of continuous linear systems in the presence of bounded noise and a common class of unmodeled dynamics provided that two estimation schemes are used in parallel. Both estimation schemes are introduced in order to minimize the plant identification error by selecting, as plant parameter estimates, a convex combination of both parameter estimates which leads to the selection of one of the estimation schemes, via a switching rule, on time intervals of at least a minimum prefixed residence duration. The weights of the individual parameter vector estimates are provided at each time by an optimization or suboptimization scheme for a quadratic loss function of the possibly filtered tracking error and/or control input. The robust stability of the overall adaptive scheme is ensured by an adaptation relative dead zone which takes into account the contribution of the unmodeled dynamics and bounded noise. The basic results are derived for two different estimation strategies which have either a shared regressor with the plant or individual regressors for the input contribution and its contributed derivatives. In this second case, the plant input is obtained from a similar convex combination rule as the one used for the estimators in the first approach. An extension of the basic strategies is also pointed out including a combined use of the (sub) optimization scheme with a supervisor of past measures for the on-line calculation of the estimator weights in the convex combination. Finally, the extension of the scheme for the use of any number of parametrical estimators is focused on.     

Robust preliminary analysis of large-scale linear model for optimal industrial investments

Which equipment should be bought for a given sum to increase the profit of an industrial enterprize with a known specification of production within given limits? This problem is described as a large-scale linear program (LP) of a specific structure. An effective preliminary analysis for this structure was proposed in Ioslovich and Makarenkov [On methods of dimensionality reduction in linear programming, Econ. Math. Methods Moscow (in Russian) 11(3) (1975) 316-324] which aimed to reduce the size of the problem by detection of the redundant and active constraints. In this paper a robust system is considered, dealing with box-constrained uncertainties in the input coefficients. The analysis is based on robust evaluations of bounds for primal and dual constraints. A robust evaluation of uncertain duals presented in [I. Ioslovich, P.-O. Gutman, Robust redundancy determination and evaluation of the dual variables of linear programming problems in the presence of uncertainty, 1, in, V. Kucera, M. Sebek (Eds.), Proceedings of 3rd IFAC Symposium on Robust Control Design (ROCOND 2000), IFAC, Prague, Czech Republic, Elsevier Science, Amsterdam, 2000, paper 115] is essentially used.     

A comparative study of numerical methods for solving quadratic Riccati differential equations

In this paper, we use Legendre wavelet method for solving quadratic Riccati differential equations and perform a comparative study between the proposed method and other existing methods. Our results show that in comparison with other existing methods, the Legendre wavelet method provides a fast convergent series of easily computable components. The present study is illustrated by exploring two kinds of nonlinear Riccati differential equations that shows the pertinent features of the Legendre wavelet method.     

A comparative study of tumor markers of adenocarcinoma prostate

The present study deals with the evaluation and comparison of the tumor markers for prostatic carcinoma—The Total Acid Phosphatase (ACP Total) and its Prostatic Fraction (ACP PF) estimated by the enzyme kinetic method, an immunoreactive Prostatic Acid Phosphatase (PAP) and Prostate Specific Antigen (PSA) estimated by enzyme immunoassay. The comparison of all four markers revealed that there was no perfect positive correlation between any of these four markers. PSA had shown a better correlation with ACP Total and its prostatic fraction ACP PF. No correlation was observed between PSA and PAP. Of the four markers PAP exhibited a very low sensitivity, positive and negative predictive values. PSA had shown an absolute specificity, sensitivity, positive and negative predictive values for adenocarcinoma prostate. PSA levels in all phases of disease showed a 100% correlation with disease status. Being a marker with very high tissue specificity and sensitivity, it is revolutionizing the diagnosis of prostatic carcinoma. Hence, it could be used effectively for screening of elderly people over 50 years of age who are at high risk for developing prostatic carcinoma for early diagnosis of this disease.     

中国在哈萨克斯坦矿业投资区域优选评价研究

哈萨克斯坦与我国接壤,位于丝绸之路经济带核心区,是全球最大的内陆国,是中亚地区矿产资源最为丰富的国家,地缘战略地位突出,已成为中国企业投资的最为重要的海外国家之一。哈萨克斯坦国土面积广大,地区间资源禀赋与投资环境差异较大,优选重点矿业开发区域对指导中国企业到哈萨克斯坦投资意义重大。本文统筹国家战略需求与企业需求,建立了哈萨克斯坦矿业投资评价指标体系,涵盖资源禀赋、投资环境、资源市场需求以及国家战略需求4个二级指标和资源潜力、竞争环境和社会环境等12个三级指标。采用层次分析法（AHP）对哈萨克斯坦的14个州进行了矿业投资区域优选评价,按照得分高低,并结合实际情况,将14个州分为矿业投资优选区、矿业投资鼓励区和一般矿业投资区域三类。矿业投资优选区包括阿特劳州、卡拉干达州、东哈萨克斯坦州、曼格斯套州和南哈萨克斯坦州,矿业投资鼓励区包括西哈萨克斯坦州、阿拉木图州、巴甫洛达尔州、北哈萨克斯坦州和科斯塔奈州,以及一般矿业投资区包括阿克托别州、江布尔州、阿克莫拉州和克孜勒州奥尔达州。     

多尺度几何分析阈值去噪的比较研究

多尺度几何分析方法用于图像去噪已经成为图像处理方向的研究的一个热点。简要介绍和分析了几种常用于去噪的多尺度几何分析方法(曲波变换、轮廓波变换、剪切波变换),其中剪切波能提供了更稀疏的表示,图像实现最优逼近。实验结果也证明,剪切波变换阈值去噪在主观视觉上与峰值信噪比优于其他多尺度分析方法。     

The role of feedback in changing organizational routine: A case study of Haier,China

The ability to change organizational routines according to the need of organizational transformation is difficult to achieve, but increasingly vital for an organization to survive in a highly turbulent business environment. However, despite fruitful research on organizational routines, how routines evolve through feedback remains unclear. This study aims to investigate the role of feedback in routine changes by examining a case study of Haier, the largest home appliance manufacturer in the world. The findings of this case show that feedback of a routine plays a critical role in routine changes. It highlights that feedback helps an organization to make sense of its behavior patterns and evaluate these patterns properly, which enable the organizations to better initiate and advocate routine changes that are necessary for a successful organizational transformation. Further, this case shows the importance of leveraging IT in managing routine changes.     

A dynamic output feedback control law for elastic joint robots via feedback-passivity approach

Motivated by recent dynamic output feedback passivation results, a new set-point control law is presented for an elastic joint robot when the velocity measurements are not available. The proposed methodology designs an additional dynamics with which the parallel-connected system is feedback passive. That is, the composite nonlinear robot system has relative degree one with a new output and its zero-dynamics subsystem becomes the virtual closed-loop system with a simple proportional-derivative (PD) control law. This approach provides an alternative way of replacing the role of the velocity measurements for the PD law. With the proposed control law, the transfer function of the additional system has the form of sG(s) with a strictly positive real (SPR) G(s). Robustness analysis is also given with regard to uncertainties on the robot parameters. The performance of the proposed control law is illustrated in the simulation studies of a manipulator with three revolute elastic joints.     

中国在亚洲地区学科研究相对优弱势比较研究

 本研究以相对科学推动力为衡量基础,以学科研究“相对优势系数”为新指标,以ESI1996~2006为数据来源, 采用线图分析、单因素方差分析,等级聚类、相似性比较等方法,对亚洲地区论文产出七强进行了学科研究质量相对优弱势等级评价, 数据用SPSS处理。结果表明,除香港的大部分学科超出世界水平外,绝大多数亚洲学科研究质量都低于世界水平,而中国的学科研究质量属于亚洲七强中的弱势。     

A direct approach using the finite element method for the solution of the linear optimal control problem with a quadratic criterion

The present paper proposes a numerical approach to a linear optimal control problem with a quadratic performance index. In this technique, the time interval is divided into a number of time segments and all of the unknown functions which appear in the performance index are either interpolated linearly with respect to time or assumed to be constant in each time segment. The augmented performance index is discretized within each time element through the ordinary finite element technique.The main advantage of the present method is as follows: all of the necessary conditions for the performance index to be stationary can be expressed in the form of algebraic equations and the performance sequence of the state variables can be eliminated. As a result, the optimal control problem is reduced to the simple one of finding the sequence of control variables alone, which minimizes the quadratic performance index.A general formulation of the method is given and simple numerical examples are shown to demonstrate the effectiveness of the technique.     

Design and comparison of LQG/LTR and H∞ controllers for a VSTOL flight control system

In this paper two robust controllers for a multivariable vertical short take-off and landing (VSTOL) aircraft system are designed and compared. The aim of these controllers is to achieve robust stability margins and good performance in step response of the system. LQG/LTR method is a systematic design approach based on shaping and recovering open-loop singular values while mixed-sensitivity H_∞ method is established by defining appropriate weighting functions to achieve good performance and robustness. Comparison of the two controllers show that LQG method requires rate feedback to increase damping of closed-loop system, while H_∞ controller by only proper choose the weighting functions, meets the same performance for step response. Output robustness of both controllers is good but H_∞ controller has poor input stability margin. The net controller order of H_∞ is higher than the LQG/LTR method and the control effort of them is in the acceptable range.