Smart Vibration Control Research Articles

Finite element model updating of a plate type structure made of composite material using a network of PZT

Ambient vibrations are one of the most unpredicted, undesired, and uncontrolled destructive causes of sudden failure for many types of structural systems, predominantly those made of FRP thin plates. FRP thin plates may undergo dramatic collapse beneath the periodic ambient loads associated with frequencies, particularly those approaching natural frequencies. Much research has been done over the last few decades to enhance the structural damping behaviour capabilities of thin plates against ambient vibrations via several means and systems of active vibration control. Recent, exceptional advancements in the field of smart materials and their applications in the field of active vibration control have provided a viable alternative to conventional vibration control tools (sensors/actuators). For instance, the coupled properties inherited by PWAS were utilised to develop durable, compact, and efficient actuators/sensors. To minimize the influence of the disparity between the theoretical and actual dynamic structure performances, the numerical FEM has to be updated using real structural data. In the present study, a model update of the structural parameters of a smart beam is carried out by employing PWAS as smart vibration control tools (sensor/actuator) that have been previously installed on the substrate structure. A finite element model is developed to mimic this intelligent beam. Then, laboratory experiments are undertaken to determine system parameters, which are used to update the finite element model. Finally, optimization is done to minimize the FEM variance in the designated structure vibration response from the real one.

SISO Piezo Based Circuit Development for Active Structural Vibration Control

This paper deals with the issue of developing a smart vibration control platform following an innovative model-based approach. As a matter of fact, obtaining accurate information on system response in pre-design and design phases may reduce both computational and experimental efforts. From this perspective, a multi-degree-of-freedom (MDOF) electro-mechanical coupled system has been numerically schematized implementing a finite element formulation: a robust simulation tool integrating finite element model (FEM) features with Simulink® capabilities has been developed. Piezo strain actuation has been modelled with a 2D finite element description: the effects exerted on the structure (converse effect) have been applied as lumped loads at the piezo nodes interface. The sensing (direct effect) has instead been modelled with a 2D piezoelectric constitutive equation and experimentally validated as well. The theoretical study led to the practical development of an integrated circuit which allowed for assessing the vibration control performance. The analysis of critical parameters, description of integrated numerical models, and a discussion of experimental results are addressed step by step to get a global overview of the engineering process. The single mode control has been experimentally validated for a simple benchmark like an aluminum cantilevered beam. The piezo sensor-actuator collocated couple has been placed according to an optimization process based on the maximum stored electrical energy. Finally, a good level of correlation has been observed between the forecasting model and the experimental application: the frequency analysis allowed for characterizing the piezo couple behavior even far from the resonance peak.

An experimental study on dynamic analysis and active vibration control of smart laminated plates

Dynamic analysis and active vibration suppression of smart plates is presented in this work. An experimental set-up has been developed to carry out experimentation. The setup is composed of a specimen laminated composite plate, a data acquisition device, signal conditioning elements, a LabView based controller and cables/wires for electrical connections. Experiments are performed with laminated plates of different layups. Aluminium, polycarbonate and medium density polyethylene sheets are used as layup materials. Tensile tests are performed to determine the mechanical properties of the constituting material layers. Piezoelectric patches integrated with elastic layers of specimen plate are used as sensor and actuator pair. The open and closed loop responses are obtained for each specimen plate and the fundamental frequencies are determined experimentally. The closed loop responses are obtained using PID controller configured in LabVIEW graphical program. The experimental results have demonstrated the validity and efficiency of PID controller in active vibration control of smart structures. The problem plates are also modelled using ANSYS workbench for modal analysis. The experimental results of fundamental natural frequencies of specimen plates are validated through ANSYS finite element results. The results are in good agreement and thus can be used as a touchstone for analytical/numerical work.

Finite element model based on an efficient layerwise theory for dynamics and active vibration control of smart functionally graded beams

In this work, we present a two-noded efficient finite element (FE) model incorporating the layer-wise mechanics for the dynamics and active vibration control of smart functionally graded (FG) beams. The material properties in the FG beam are assumed to vary smoothly in the thickness direction according to power law variation. The effective properties are computed using Mori-Tanaka homogenization scheme. Electric potential profile in the electroded piezoelectric layers/patches is assumed quadratic across its thickness. The equations of motion are derived using extended Hamilton’s principle. Due to the complex algebraic expressions involved in the effective properties of FG system, the inertia and stiffness parameters are computed numerically using six point Gauss integration method. To fulfill the convergence requirements for weak integration of various energy terms in the variational formulation, the transverse displacement is interpolated with Hermite interpolation function possessing C1-continuity while the inplane displacement, shear rotation and quadratic component of the electric potential are interpolated with linear Lagrangian functions of C0-continuity. The equipotential condition of the electroded piezoelectric sensors and actuators is conveniently modelled using electric node concept. The control system is designed for constant gain velocity feedback (CGVF), and optimal LQR and LQG control strategies for a reduced order model using state space approach. The control performance is studied for single-input-single-output (SISO) and multi-input-multi-output (MIMO) configurations under various excitations. The effect of material inhomogeneity on stability/instability of the closed-loop response in the CGVF control has been discussed.

Active vibration control of smart laminated beams using PFRC patches as sensors and actuators

Abstract The aim of this paper is to present the performance of piezoelectric fiber-reinforced composite (PFRC) sensors and actuators in active vibration suppression of smart laminated beams. Finite element based on an efficient layerwise theory has been selected for the kinematic modelling of smart beam. Both classical (CGVF) and optimal (LQR and LQG) feedback control systems are employed to actively suppress the vibration. The effects of fiber volume fraction and fiber direction of PFRC on the settling time, active damping ratios, peak tip deflection and peak control voltage are studied. The effectiveness of control strategies in terms of minimum control voltage for a given settling time is presented

Neuro-Fuzzy modal control of smart laminated composite structures modeled via mixed theory and high-order shear deformation theory

Abstract The present study develops and applies a neuro-fuzzy modal vibration control of smart laminated composite structures with piezoelectric layers via Mixed theory. Differently from previous studies, the composite structures in this paper are modeled via the Mixed Theory using the High-order Shear Deformation Theory (HSDT) theory. The Mixed Theory adopts a single layer when representing the mechanical displacement field, through HSDT theory, and multiple layers (Layerwise theory) for the electrical degrees of freedom. The Mixed Theory is computationally implemented in the Matlab® software using a plate-type element called Serendipity. Moreover, a neuro-fuzzy active vibration controller is implemented to attenuate the vibration of the smart composite structures. The numerical results validate the electric-mechanical coupling adopted, showing the importance of the mixed theory in the static and dynamic modeling of slender beams and plates with piezoelectric layers. Finally, the results of the robustness analysis indicate that the neuro-fuzzy controller has benefits compared with the linear quadratic regulator.

Semi-active vibration control of smart isolated highway bridge structures using replicator dynamics

In the past two decades, passive control strategies using isolation and fluid dampers have been employed for the seismic protection of bridge highway structures. The isolation vibration control, however, lacks the adaptability to react in real-time for changes during unpredictable earthquake loadings. This research advances the idea of combining the conventional passive control (base isolation) with a semi-active or active control system to create the next generation of smart bridge structures. A novel control algorithm based on the evoluationary game theory concept of replicator dynamics is investigated for vibration reduction of highway bridge structures equipped with both a passive isolation system and semi-active control devices subjected to earthquake loadings. The proposed methodology is evaluated by application to a benchmark example based on Interstate 5 overcrossing California State Route 91 (abbreviated as 91/5) bridge in southern California subjected to near-field historical earthquake excitations. Substantial reduction in mid-span displacement is achieved compared with the conventional base-isolated bridge.

A Study on the Effects of Multiwall Carbon Nanotubes on Dynamic Stiffness of Hydrophilic-base Magnetorheological Gel

Background: Recently, addition of multi-walled-carbon-nanotubes (MWCNTs) has been researched to enhance the rheological properties of magnetorheological (MR) materials of fluid, elastomer and gel. However, there is a lack of study on the effects of MWCNTs on hydrophilic based MR gels (MRG), which have shown a high potential to be applied in smart vibration control systems. Objective: This study is aimed to analyze the effect of MWCNTs on the dynamic stiffness of hydrophilic based MRG. Method: Dynamic stiffness of hydrophilic based MRG was experimentally computed under different magnetic fields and strain amplitudes. Results: Experimental results indicate that the addition of MWCNTs in hydrophilic MRG showed overall degradation of stiffness variation in contradictory to similar research performed on silicon oil based MR gel. Conclusion: These contradictory results reveal that MRGs of hydrophilic base have a different interaction with MWCNTs than hydrophobic oil base.

Optimal design of semiactive MR-TLCD for along-wind vibration control of horizontal axis wind turbine tower

Present study aims to address the design of smart vibration control scheme for horizontal axis wind turbine tower using magneto-rheological tuned liquid column damper. With this in view, a reduced order model of the blade-tower system is used, considering centrifugal stiffening and gravitational effects that lead to time-dependent dynamic stiffness matrix. Aerodynamic load on the blades is modeled using blade element momentum theory. Semiactive control law in linear quadratic regulator framework is developed to mitigate the along-wind vibration of the tower. To implement the control law, multiblade coordinate transformation is adopted that converts the system matrices in the nonrotating framework to tackle its time dependency. The performance of the proposed control algorithm is demonstrated using numerical simulations with and without controller. Clipped optimality of the control force is imposed to keep the parameters of magneto-rheological tuned liquid column damper in the feasible range. Finally, sensitivity analysis is carried out to demonstrate the performance envelope of the proposed control algorithm for different operational scenario. Results presented in this paper clearly demonstrate that the proposed algorithm can be employed for effective along-wind vibration control of large HWAT tower.

Influence of piezoelectric nonlinearity on active vibration suppression of smart laminated shells using strong field actuation

In this work, we study the effect of piezoelectric nonlinearity on shape and active vibration control of smart piezolaminated composite and sandwich shallow shells under strong field actuation. An efficient finite element model with advanced laminate kinematics and full electromechanical coupling is developed for this purpose. The nonlinearity is modeled using a rotationally invariant quadratic constitutive relationship for the piezoelectric material. For the laminate kinematics, a recently developed efficient layerwise theory, which is computationally as efficient as an equivalent single-layer theory, and has been shown to yield very accurate results in comparison with three-dimensional piezoelasticity based solutions for linear electromechanical response of hybrid laminated shells, has been employed. The nonlinear static response for shape control is obtained using the direct iteration method, and the active vibration control response with linear quadratic Gaussian controller is obtained by using the feedback linearization approach through control input transformation. It is shown that the linear model significantly overestimates the voltage required for shape or vibration control, when the applied electric field is beyond the threshold limit of the actuator. Thus, the use of the nonlinear model is essential for designing the control system utilizing the full actuation authority of the actuators. The effects of actuator thickness, radius of curvature to span ratio and applied loading on the relative difference between linear and nonlinear predictions are illustrated for shape and vibration control of smart cylindrical and spherical shells.

Active Vibration Control of Smart Functionally Graded Beams

This work is devoted to examine the performance of the constraining layer of the active constrained layer damping (ACLD) treatment made of the active fiber composites (AFC) materials for vibration control of functionally graded (FG) beams. The task of investigating the performance of the active constrained layer damping (ACLD) treatment has been accomplished to demonstrate the use of AFCs as the materials for distributed actuators. Finite Element (FE) model is developed to describe the open loop and closed loop dynamics of the FG beams integrated with the patches of the ACLD treatment. The closed loop frequency response functions computed by the FE models reveal that the ACLD treatment with its constraining layer composed of AFC material significantly enhances the damping characteristics of the FG beams.The performance of the ACLD treatment when the orientation angle of the piezoelectric fibers of the AFC constraining layer is varied has also been investigated. Such variation of piezoelectric fiber orientation angle significantly affects the controllability of the ACLD treatment for active damping of the FG beams. The investigations carried out here may be useful for further experimental verifications and suggest the potential use of AFC materials for developing new distributed actuators of light-weight smart structures.

Vibration Control of Sandwich Plates

This paper presents the active control of vibrations of sandwich plates using piezoelectric composites (PZC). The top surface of the plate is integrated with the patches of active constrained layer damping treatment. Active fiber composite, one of the commercially available PZCs, is used as the material of the constraining layer of the patches and the constrained layer of the patch is composed of a viscoelastic material. Considering the first order shear deformation theory individually for each layer of the sandwich plate, a three-dimensional finite element model has been developed. The performance of active fiber composite for the smart vibration control of the sandwich plates has been studied and numerical results are presented. Emphasis has also been placed on investigating the effect of variation of piezoelectric fiber orientation angle in the constraining layer on the control authority of the patches.

Multidisciplinary Design Optimization for Vibration Control of Smart Laminated Composite Structures

The structure and vibration control system of smart laminated composites consisting of graphite–epoxy composites and piezoelectric actuators are designed for optimum vibration suppression. The placement of piezoelectric actuators, the lay-up configurations of laminated composite plates, and the H2 control system are employed as design variables and they are optimized simultaneously by a simple genetic algorithm. To reduce complexity, only pre-selected families of lay-up configurations are considered. An objective function is the H2 performance with respect to the controlled response for vibration suppression. A multidisciplinary design optimization is performed with the above three design variables and then the output feedback system is reconstructed with a dynamic compensator based on a linear matrix inequality approach. The validity of the modeling and calculation technique is confirmed experimentally. Optimization results show that optimized smart composites with the present approach successfully realize vibration suppression and it is confirmed that the proposed multidisciplinary design optimization technique enhances the vibration suppression of smart composites.

Effects of structural configuration on vibration control of smart laminated beams under random excitations?

The influence of structural configuration on vibration responses of smart laminated beams under random loading is studied. The effect of laminate configurations and locations of sensors/actuators in the smart system is also investigated. The layer-wise approximation for displacement and electric potential is utilized to construct the finite element model. The closed-loop control response is determined through an optimal control algorithm based on the Linear Quadratic Regulator (LQR). The correlation coefficient between the input random force and the applied actuating voltage for various configurations is also computed. It is revealed that for softer configurations, the correlation coefficient is higher than that for harder configurations. The study on the effect of sensor/actuator collocation pairs on optimal vibration control reveals that as the actuator shifts away from the sensor location, the peak of power occurs at higher frequency and becomes more distributed through all the frequencies in the domain.

Genetic algorithm based optimal control of smart composite shell structures undermechanical loading and thermal gradient

In the present paper an improved genetic algorithm (GA) based linear quadratic regulator(LQR) control scheme has been proposed for active vibration control of smart fiberreinforced polymer (FRP) composite shell structures under combined mechanicaland thermal loading. A layered shell finite element formulation has been done toobtain the electro-thermo-mechanical response of fiber reinforced polymer (FRP)composite shell structures bonded with piezoelectric patches. Based on the responsesobtained from finite element analysis, a real coded GA based improved LQRcontrol scheme has been incorporated, which maximizes the closed loop dampingwhile keeping the actuator voltages within limit. It has been observed that thedeveloped FE code can be used for determination of the accurate response ofsmart FRP shell structures for the simulation of active vibration control of suchstructures. The proposed GA based LQR control scheme could control both dynamicoscillation due to mechanical load as well as the static displacement due to athermal gradient, which was not possible with conventional LQR control scheme.

Towards Smart Vibration Control for Printed Circuit Boards

This article is focused on the problem of vibration control for Printed Circuit Boards (PCBs). The proposed control is based on a semi-passive technique called Synchronized Switch Damping on Inductor (SSDI). Implementation of this technique requires PZT inserts and only a few electronic components. Since no external source provides electrical energy to the inserts, a relatively important electromechanical coupling factor is needed to get significant vibration damping. Moreover, the PCB surface that can be covered by the PZT inserts is restricted, limiting the global coupling factor. Optimal location and geometry of the active material are determined according to these constraints using Finite Element Modelling (FEM) of the structure. Experimental results exhibit 15 dB and 10 dB attenuations for the first and the third bending modes respectively. These results are in good agreement with the theoretical predictions. Transient vibration decay is more than 4 times faster. These promising results show that the SSDI technique provides effective protection of PCBs against shocks and vibrations, while the system is lighter than active controls and more robust than passive controls.

Development of a Self-Sensing Actuator with Laminated Piezoelectric Films Toward the Smart Vibration Control of Two-Dimensional Structures.

A self-sensing actuator constructed by four laminated piezoelectric films is developed toward the smart vibration control of two-dimensional structures. First, three kinds of mechanisms of self-sensing acutuators with two or four laminated piezoelectric films are proposed by examining the combinations of film construction and bridge circuits of analog electric controllers. And those self-sensing actuators are applied to the free vibration control of the first mode of a cantilever beam and it is ascertained that the vibration suppression effects are obtained by all the three mechanisms and the theories show good agreements with the experiments. Finally, the mechanism constructed by four laminated piezoelectric films is applied to the vibration control of a simply-supported rectangular plate as an example of two-dimensional structures and it is verified that the vibration control effect is actually obtained and the theory agrees well with the experiment.