Amalia Moutsopoulou

Innovation in Active Vibration Control Strategy of Intelligent Structures

Large amplitudes and attenuating vibration periods result in fatigue, instability, and poor structural performance. In light of past approaches in this field, this paper intends to discuss some innovative approaches in vibration control of intelligent structures, particularly in the case of structures with embedded piezoelectric materials. Control strategies are presented, such as the linear quadratic control theory, as well as more advanced theories, such as robust control theory. The paper presents sufficiently a recognizable advance in knowledge of active vibration control in intelligent structures.

Modeling of Active Vibration Control in Smart Structures

The paper presents active control of smart structures within a focused frame of piezoelectric applications in active vibration and noise attenuation with potential applications in mechanical and civil engineering. Smart structure has become an increasingly common term describing a structure embedded or bonded with a large number of lightweight active electro-mechanical sensors and actuators. In this paper, we consider the modelling and control issues related to smart structures bonded with piezoelectric sensors and actuators with emphasis on robust control design taking into account structural uncertainties using the H Infinity control theory. The results show that the vibrations can be significantly suppressed by H Infinity controller.

UNCERTAINTY OF MODELS IN INTELLIGENT SYSTEMS UNDER STOCHASTIC LOADING

Abstract. In this paper, we address the problem of vibrations of intelligent structures. Stimuli may come from external perturbations of the system, disturbances or excitation that may cause structural vibrations, such as wind loading or earthquake. First, an accurate model of a piezocomposite intelligent structure with special boundary conditions is derived by using of FEM analysis. Then the robustness of the uncertain closed-loop model performances has been investigated. Obtained results show the higher performance of Hinfinity design approach in rejection of disturbances.

OPTIMAL CONTROL TUNNING IN SMART STRUCTURES WITH DELAMINATIONS

Abstract. An efficient strategy for calculation of delaminations in composite beams and intelligent structures is used in order to quantify structural uncertainties within a finite element model of a piezocomposite (multilayered plate theory). Furthermore the dynamical system is connected with robust and neurofuzzy control. The problem of positioning of actuators and sensors has been investigated. Model based simulations of increasing complexity illustrate some of the attractive features of the strategy in terms of accuracy as well as computational cost. This shows the possibility of using such strategies for the development of smart structural and systems.

ROBUST CONTROL OF SMART STRUCTURES WITH OPTIMALLY PLACED ACTUATORS AND SENSORS

The objective of this work is to design robust controller for smart structures to control its response under the influence of external excitation. An accurate model for the analysis of smart composite beams with surface bonded piezoelectric sensors and actuators patches is considered. Optimal placement of five piezoelectric sensor/actuator pairs are found, by exhaustively examining all possible configurations in order to suppress the first six modes of vibration. The LQR performance index is used as objective function to locate the sensor/actuator pairs. Vibration reduction for the cantilever beam with piezoelectric patches bonded in the optimal location was investigated to attenuate the first six modes of vibration using a Hinfinity scheme. After modeling multiplicative uncertainty, the augmented uncertain plant is obtained; an optimal robust controller is designed using Hinfinity. A robust controller is designed based on the augmented plant composed of the nominal model and it’s accompanied uncertain. Robust and nominal performances of designed controllers are achieved for perturbed plants and results were compared.

Systematic Formulation of Model Uncertainties and Robust Control in Smart Structures Using H ∞ and μ-Analysis

The influence of structural uncertainties on actively controlled smart beams is investigated in this paper. The dynamical problem of a model smart composite beam is based on a simplified modelling of the actuators and sensors, both being realized by means of piezoelectric layers. In particular, a practical robust controller design methodology is developed, which is based on recent theoretical results on H ∞ control theory and μ-analysis. Numerical examples demonstrate the vibration-suppression property of the proposed smart beams.

Nonsmooth and Nonconvex Optimization for the Design and Order Reduction of Robust Controllers Used in Smart Structures

H-infinity controller design for linear systems is a difficult, nonconvex typically nonsmooth optimization problem when the controller is fixed to be of order less than the one of the open-loop plant, a requirement with some importance in embedded smart systems. In this paper we use a new Matlab package called HIFOO, aimed at solving fixed-order stabilization and local optimization problems; it is based on a new hybrid solution algorithm. The problem is to reduce the vibration of the smart system using H-infinity control and nonsmooth optimization.

Uncertainty Modeling and Robust Control for Smart Structures

In this work a robust control problem for smart beams is studied. First the structural uncertainties of basic physical parameters are considered in the model of a composite beam with piezoelectric sensors and actuators subjected to wind-type loading. The control mechanism is introduced and is designed with the purpose to keep the bean in equilibrium in the event of external wind disturbances and in the presence of mode inaccuracies using the available measurement and control under limits. For this model we considered the analysis and synthesis of a H ∞ -controller with the aim to guarantee the robustness with respect to parametric uncertainties of the beam and of external loads. In addition a robust m-controller was analyzed and synthesized, using the D − K Iterative method. The results are compared and commented upon using the various controllers.