This PDF file contains the front matter associated with SPIE Proceedings volume 7286, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.

Using an integrated finite element simulation-optimization tool, the design of a multiple zone composite wing is studied to improve its free vibration behavior. The composite structure zones are composed of multiple layers of woven fabrics with different fiber materials and orientations. Results show that a single critical zone in the structure can be identified and used (1) to significantly improve the natural frequencies of the wing regardless of other zones, (2) to perform a frequency tuning with no significant interactions with other zones, and (3) to optimally control the wing's free vibration behavior.

The advances in miniaturization techniques over the last decades has made the widespread of electronic devices greater than ever and the rate of growth increases each day. Research has been carried out all over the world aiming at developing devices capable of capturing ambient energy and converting it into useable energy in this very promissing field of energy harvesting. Piezoelectric laminates have been used in the design of energy harvesting systems. While most of current research considers traditional assemblies with bimorph transducers and proof masses, this work involves the design of novel energy harvesting devices and other laminate piezoelectric structures by applying topology optimization, which combines Finite Element Method with optimization algorithms. The finite element employs a robust formulation capable of representing both direct and converse piezoelectric effects, based on the MITC formulation. The topology optimization uses the PEMAP-P model (Piezoelectric Material with Penalization and Polarization) combined with the RAMP model (Rational Approximation of Material Properties), where the design variables are the pseudo-densities that describe the amount of piezoelectric material at each finite element. A multi-objective function is defined for the optimization problem, which aims at designing eigenvalues and eigenvectors and maximizing the electromechanical coupling of a specific mode. This paper presents the implementation of the finite element and optimization software and shows results achieved.

The purpose of the paper is the development of techniques for hybrid experimental - numerical photoelasticity analysis. The general scheme of such analysis is presented. Generation of digital images mimicking the effect of photoelasticity naturally incorporates into the hybrid iterative procedure enabling effective interpretation of experimental results of Investigation Smart structures and provides insight into the physical processes taking place in the analysed objects. Visualization techniques of the results from finite element analysis procedures are important due to several reasons. First is the meaningful and accurate representation of processes taking place in the analyzed smart structures. Second, and perhaps even more important, is building the ground for hybrid numerical - experimental techniques. A typical example of FEM application in developing a hybrid technique is presented in paper.

The hysteresis for shape memory alloy (SMA) actuators has been shown to undergo large changes in response to the applied loading frequency and amplitude. This paper demonstrates the methodology needed to model and control SMA actuators assuming a variable load frequency and amplitude. A one-dimensional model of an SMA actuator which accounts for the strain-dependent hysteresis of SMA actuators is derived. Moreover, a model based control algorithm is developed to control the position of the SMA actuator. Numerical simulations are performed to examine the approach.

Ferroelectric and ferromagnetic actuators are being considered for a range of industrial, aerospace, aeronautic and biomedical applications due to their unique transduction capabilities. However, they also exhibit hysteretic and nonlinear behavior that must be accommodated in models and control designs. If uncompensated, these effects can yield reduced system performance and, in the worst case, can produce unpredictable behavior of the control system. One technique for control design is to approximately linearize the actuator dynamics using an adaptive inverse compensator that is also able to accommodate model uncertainties and error introduced by the inverse algorithm. This paper describes the design of an adaptive inverse control technique based on the homogenized energy model for hysteresis. The resulting inverse filter is incorporated in an L₁ control theory to provide a robust control algorithm capable of providing high speed, high accuracy tracking in the presence of actuator hysteresis and nonlinearities. Properties of the control design are illustrated through numerical examples.

The use of finite element or finite difference techniques to discretize nonlinear smart material system models can yield full-order numerical models that accurately characterize the system dynamics but do so at significant computational cost. This can preclude the use of these full-order models for uncertainty analysis, sensitivity analysis, system design, or real-time control implementation. In this paper, we discuss the construction of reduced-order system models using proper orthogonal decompositions (POD) with updates. Through the use of snapshots constructed from the full-order models, fundamental physics is retained while significantly improving efficiency for high-speed implementation.

Comprehensive physical models can accurately quantify the dynamics of nonlinear and hysteretic systems but often require significant computational cost. This can reduce their effectiveness when performing sensitivity analysis, uncertainty analysis, parameter calibration or system design which typically requires multiple iterations of computationally expensive routines. This can also preclude the use of these models for real-time model-based control design. Emulators provide statistical approximations to comprehensive physical models which provide two advantages: high efficiency and statistical characterization of missing model components. We discuss the construction of statistical emulators to provide efficient surrogates for nonlinear smart material models. We will primarily focus on emulators for the homogenized energy model for ferroic compounds.

The primary objective of this research is to develop novel model-based multispectral controllers for smart material systems in order to deal with sidebands and higher harmonics and with several frequency components simultaneously. Based on the filtered-X least mean square algorithm, it will be integrated with a nonlinear model-based controller called model predictive sliding mode control. Their performance will be verified in simulation and with various applications such as helicopter cabin noise reduction. This research will improve active vibration and noise control systems used in engineering structures and vehicles by effectively dealing with a wide range of multispectral signals.

The simplest form for the dynamics of constrained tensegrity system is a non-minimal realization. This paper gives a control law to force the tensegrity system to modify its shape to a pre-specified shape, using the smallest control force. The approach is similar to a multi-Lyapunov approach. We create a vector of Lyapunov functions, chosen to force the desired shape change, as well as other performance properties that may be selected. This vector is forced by the control system to satisfy a linear stable differential equation. Some tensegrity examples illustrate the ideas.

This paper reports on the development and testing of electrostatically actuated deformable mirrors for optical correction. The system considered here is limited to the lower modes of aberration; namely, focus/defocus and tip/tilt. The main problem with using electrostatics is due to the nonlinear relationship between force and distance in such a system. Accordingly, this work uses a nonlinear control system in order to obtain greater deflection for a given voltage. The paper describes recent experimental results with closed loop control.

In this paper we incorporate a novel approach to synthesize a class of closed-loop feedback control, based on the variational structure assignment. Properties of a viscoelastic system are used to design an active feedback controller for an undamped structural system with distributed sensor, actuator and controller. Wave dispersion properties of onedimensional beam system have been studied. Efficiency of the chosen viscoelastic model in enhancing damping and stability properties of one-dimensional viscoelastic bar have been analyzed. The variational structure is projected on a solution space of a closed-loop system involving a weakly damped structure with distributed sensor and actuator with controller. These assign the phenomenology based internal strain rate damping parameter of a viscoelastic system to the usual elastic structure but with active control. In the formulation a model of cantilever beam with non-collocated actuator and sensor has been considered. The formulation leads to the matrix identification problem of two dynamic stiffness matrices. The method has been simplified to obtain control system gains for the free vibration control of a cantilever beam system with collocated actuator-sensor, using quadratic optimal control and pole-placement methods.

A procedure to monitor crack growth in Aluminum lug joints subject to fatigue loading is developed. Sensitivity analysis is used to decide sensor importance and monitor crack growth rate. A new feature extraction technique based on Discrete Cosine Transformation (DCT) is developed to analyze complex sensor signals. Self-sensing piezoelectric sensors are surface mounted on Al 2024 T351 lug joint samples, 0.25 in. thickness. Samples with single crack site and multiple crack sites were used in this study and to initiate multiple crack sites, they were notched symmetrically near the shoulders and then tested under a fatigue load of 110lbs (0.49kN) to 1100lbs (4.9kN). Crack lengths were monitored over the entire life of the lug joint sample using a CCD camera. Active sensing was carried out at every crack length, when the machined was stopped. The piezoelectric actuator was excited with a chirp signal, swept between 1kHz to 500kHz, and sensor readings were collected at a sampling rate of 2Ms/s. Using three different sensor sensitivity algorithms, the sensor signals are analyzed and their efficiency in predicting crack growth rates and deciding sensor importance is studied. Sensor sensitivity is defined as the changes observed in sensor signals obtained from a damaged sample compared to healthy sample. The first two algorithms, ORCA and One-Class SVM's, are based on statistical techniques for outlier detection and the third algorithm, a new detection framework, is based on feature extraction using Discrete Cosine Transformation (DCT). The efficacy of these methods for damage characterization is presented.

Prognostic algorithms indicate the remaining useful life based on fault detection and diagnosis through condition monitoring framework. Due to the wide-spread applications of advanced composite materials in industry, the importance of prognosis on composite materials is being acknowledged by the research community. Prognosis has the potential to significantly enhance structural monitoring and maintenance planning. In this paper, a Gaussian process based prognostics framework is presented. Both off-line and on-line methods combined state estimation and life prediction of composite beam subject to fatigue loading. The framework consists of three main steps: 1) data acquisition, 2) feature extraction, 3) damage state prediction and remaining useful life estimation. Active piezoelectric and acoustic emission (AE) sensing techniques are applied to monitor the damage states. Wavelet transform is used to extract the piezoelectric sensing features. The number of counts from AE system was used as a feature. Piezoelectric or AE sensing features are used to build the input and output space of the Gaussian process. The future damage states and remaining useful life are predicted by Gaussian process based off-line and on-line algorithms. Accuracy of the Gaussian process based prognosis method is improved by including more training sets. Piezoelectric and AE features are also used for the state prediction. In the test cases presented, the piezoelectric features lead to better prognosis results. On-line prognosis is completed sequentially by combining experimental and predicted features. On-line damage state prediction and remaining useful life estimation shows good correlation with experimental data at later stages of fatigue life.

The ability to detect anomalies in signals from sensors is imperative for structural health monitoring (SHM) applications. Many of the candidate algorithms for these applications either require a lot of training examples or are very computationally inefficient for large sample sizes. The damage detection framework presented in this paper uses a combination of Linear Discriminant Analysis (LDA) along with Support Vector Machines (SVM) to obtain a computationally efficient classification scheme for rapid damage state determination. LDA was used for feature extraction of damage signals from piezoelectric sensors on a composite plate and these features were used to train the SVM algorithm in parts, reducing the computational intensity associated with the quadratic optimization problem that needs to be solved during training. SVM classifiers were organized into a binary tree structure to speed up classification, which also reduces the total training time required. This framework was validated on composite plates that were impacted at various locations. The results show that the algorithm was able to correctly predict the different impact damage cases in composite laminates using less than 21 percent of the total available training data after data reduction.

This paper explores the use of Principal Component Analysis (PCA), an extended form of PCA and, the T²- statistic and Q-statistic; distances that detect and distinguish damages in structures under varying operational and environmental conditions. The work involves an experiment in which two piezoelectric transducers are bonded on an aluminium plate. The plate is subjected to several damages and exposed to different levels of temperature. A series of tests have been performed for each condition. The approach is able to determine whether the structure has damage or not, and besides, gives qualitative information about its size, isolating effects of the temperature.

A new constitutive modeling framework is presented to predict polarization reorientation from mechanical loading in ferroelectric materials. The modeling framework employs a homogenized energy approach to predict the reorientation of local polarization variants in response to multi-axial mechanical loading. Single crystal energy relations are given and integrated into a polycrystal model using a reduced order modeling technique that employs a set of stochastic parameters which accommodate material inhomogeneities. The homogenized energy approach provides a methodology that simplifies computations required to predict nonlinear polarization reorientation from applied stresses. The new formulation circumvents the need for large scale minimization problems of multi-well energy potentials and facilitates constitutive model integration into finite element codes and nonlinear control designs. The theory is presented, numerically implemented, and compared with experiments on lead zirconate titanate given in the literature.

The multi-body dynamics appear in a new form, as a matrix differential equation, rather than the traditional vector differential equation. The model has a constant mass matrix, and the equations are non-minimal. A specific focus of this paper is tensegrity systems. A tensegrity system requires prestress for stabilization of the configuration of rigid bodies and tensile members. This paper provides an efficient model for both static and dynamic behavior of such systems, specialized for the case when the rigid bodies are axi-symmetric rods.

In the one-dimensional classical analogs to Anderson localization, whether optical, acoustical or structural dynamic, the periodic system has its periodicity disrupted by having one or more of its parameters randomly disordered. Such randomized systems can be modeled via an infinite product of random transfer matrices. In the case where the transfer matrices are 2x2, the upper (and positive) Lyapunov exponent of the random matrix product is identified as the localization factor (inverse localization length) for the disordered one-dimensional model. It is this localization factor which governs the confinement of energy transmission along the disordered system, and for which the localization phenomenon has been of interest. The theorem of Furstenberg for infinite products of random matrices allows us to calculate this upper Lyapunov exponent. In Furstenberg's master formula we integrate with respect to the probability measure of the random matrices, but also with respect to the invariant probability measure of the direction of the vector propagated by the long chain of random matrices. This invariant measure is difficult to find analytically, and, as a result, either an approximating assumption is frequently made, or, less frequently, the invariant measure is determined numerically. Here we calculate the invariant measure numerically using a Monte Carlo bin counting technique and then numerically integrate Furstenberg's formula to arrive at the localization factor for both continuous and discrete disorder of the mass. This result is cross checked with the (modified) Wolf algorithm.

Actuation mechanism of chitosan-blended cellulose (CBC) electro-active paper (EAPap) bending actuator was studied using a theoretical model and experimental data. The model of bending displacement of EAPap is combined ion traveling model with multi-layer cantilever beam model. Also, the result of the model is compared with experimental data. From this model, we can predict actuation behavior as well as redistribution of ions inside of CBC EAPap under different humidity levels and electric fields. Therefore, the actuation model of EAPap can be applied to investigate the electro-mechanical actuation behavior of EAPap devices such like artificial muscles, micro robots and other various actuators.

On the basis of static, dynamic and transient analysis for the prestressing cable structures, the parameters to control the vibration of the system for transient main cables and catwalk of some long-span suspension bridge at the construction stages with the assistant cables are investigated adopting the method of the finite element considering the geometry nonlinearity. The review and prospect to control vibration with assistant cables are summarized, the finite element modeling of the system for transient main cables and catwalk is established, and the influence of the position of the assistant cables, disposed fashion and the tensile forces upon the critical frequencies of the system for transient main cables and catwalk is researched. At the same time, the effect of the damp and the tensile forces of the assistant cables on the equivalent damping ratio of the system for transient main cables and catwalk inside and outside the plane is studied and the effect to control the vibration of the system is analysed. In the end, the influence of the transformation for the tensile forces about assistant cables upon those of the transient main cables and catwalk is also investigated. Results show that, to increase the critical frequencies of the system, the assistant cables should be laid vertically with the main cables and be located in interim span or between the tower and interim span, and to increase the amount of the assistant cables can increase the critical frequencies ,and to increase the rigidities of the assistant cables can improve the ones of the transient main cables but decrease the anti-torsion ability of the catwalks, and to increase the damp of the assistant cables can improve the vibration of the transient main cables inside and outside the plane but the result is little outside the plane, and in addition the effect of the rigidities of the assistant cables is larger outside the plane but is little inside the plane. The results also show that the influence of the change of the tensile forces for the assistant cables upon those of the transient main cables and catwalk is very little.