Ipek Basdogan

Analytical modeling and experimental validation of a structurally integrated piezoelectric energy harvester on a thin plate

Vibration-based energy harvesting using piezoelectric cantilevers has been extensively studied over the past decade. As an alternative to cantilevered harvesters, piezoelectric patch harvesters integrated to thin plates can be more convenient for use in marine, aerospace and automotive applications since these systems are often composed of thin plate-like structures with various boundary conditions. In this paper, we present analytical electroelastic modeling of a piezoelectric energy harvester structurally integrated to a thin plate along with experimental validations. The distributed-parameter electroelastic model of the thin plate with the piezoceramic patch harvester is developed based on Kirchhoff’s plate theory for all-four-edges clamped (CCCC) boundary conditions. Closed-form steady-state response expressions for coupled electrical output and structural vibration are obtained under transverse point force excitation. Analytical electroelastic frequency response functions (FRFs) relating the voltage output and vibration response to force input are derived and generalized for different boundary conditions. Experimental validation and extensive theoretical analysis efforts are then presented with a case study employing a thin PZT-5A piezoceramic patch attached on the surface of a rectangular aluminum CCCC plate. The importance of positioning of the piezoceramic patch harvester is discussed through an analysis of dynamic strain distribution on the overall plate surface. The electroelastic model is validated by a comparison of analytical and experimental FRFs for a wide range of resistive electrical boundary conditions. Finally, power generation performance of the structurally integrated piezoceramic patch harvester from multiple vibration modes is investigated analytically and experimentally.

Effect of Preservation Period on the Viscoelastic Material Properties of Soft Tissues With Implications for Liver Transplantation

The liver harvested from a donor must be preserved and transported to a suitable recipient immediately for a successful liver transplantation. In this process, the preservation period is the most critical, since it is the longest and most tissue damage occurs during this period due to the reduced blood supply to the harvested liver and the change in its temperature. We investigate the effect of preservation period on the dynamic material properties of bovine liver using a viscoelastic model derived from both impact and ramp and hold experiments. First, we measure the storage and loss moduli of bovine liver as a function of excitation frequency using an impact hammer. Second, its time-dependent relaxation modulus is measured separately through ramp and hold experiments performed by a compression device. Third, a Maxwell solid model that successfully imitates the frequency- and time-dependent dynamic responses of bovine liver is developed to estimate the optimum viscoelastic material coefficients by minimizing the error between the experimental data and the corresponding values generated by the model. Finally, the variation in the viscoelastic material coefficients of bovine liver are investigated as a function of preservation period for the liver samples tested 1 h, 2 h, 4 h, 8 h, 12 h, 24 h, 36 h, and 48 h after harvesting. The results of our experiments performed with three animals show that the liver tissue becomes stiffer and more viscous as it spends more time in the preservation cycle.

A review of active vibration and noise suppression of plate-like structures with piezoelectric transducers

Structural vibrations are the major causes of noise problems, passenger discomforts, and mechanical failures in aerospace, automotive, and marine systems, which are mainly composed of lightweight and flexible plate-like structures. In order to reduce structural vibrations and noise radiations of lightweight structures, passive and active treatments have been used and investigated over the last three decades. Our aim of this article is to review current state-of-the-art of active vibration and noise suppression systems for plate and plate-like structures with various kinds of boundary conditions. The reviewed articles use numerical methods and experimental tools to study different aspects of controller architectures. In particular, the focus is placed on the active vibration and noise control systems utilizing piezoelectric patches as sensors and actuators since their popularity in vibration-based applications has increased significantly during the last two decades. We first classify the controllers according to their architectures, then compare their performance in vibration and noise attenuation, and finally provide suggestions for further progress. The categorization of the information regarding the controller strategies and sensor/actuator configurations for different host structures can be used by the controller designers as a starting point for their specific configuration.

Vibro-Acoustic Design Optimization Study to Improve the Sound Pressure Level Inside the Passenger Cabin

The interior noise inside the passenger cabin of automobiles can be classified as structure-borne or airborne. In this study, we investigate the structure-borne noise, which is mainly caused by the vibrating panels enclosing the vehicle. Excitation coming from the engine causes the panels to vibrate at their resonance frequencies. These vibrating panels cause a change in the sound pressure level within the passenger cabin, and consequently generating an undesirable booming noise. It is critical to understand the dynamics of the vehicle, and more importantly, how it interacts with the air inside the cabin. Two methodologies were used by coupling them to predict the sound pressure level inside the passenger cabin of a commercial vehicle. The Finite Element Method (FEM) was used for the structural analysis of the vehicle, and the Boundary Element Method (BEM) was integrated with the results obtained from FEM for the acoustic analysis of the cabin. The adopted FEM-BEM approach can be utilized to predict the sound pressure level inside the passenger cabin, and also to determine the contribution of each radiating panel to the interior noise level. The design parameters of the most influential radiating panels (i.e., thickness) can then be optimized to reduce the interior noise based on the three performance metrics. A structured parametric study, based on techniques from the field of industrial design of experiments (DOE) was employed to understand the relationship between the design parameters and the performance metrics. A DOE study was performed for each metric to identify the components that have the highest contribution to the sound pressure levels inside the cabin. For each run, the vibro-acoustic analysis of the system is performed, the sound pressure levels are calculated as a function of engine speed and then the performance metrics are calculated. The highest contributors (design parameters) to each performance metric are identified and regression models are built to be used for optimization studies. Then, preliminary optimization runs are employed to improve the interior sound pressure levels by finding the optimum configurations for the panel thicknesses. Our results show that the methodology developed in this study can be effectively used for improving the design of the panels to reduce interior noise when the vibro-acoustic response is chosen as the performance criteria.

Equivalent circuit modeling of a piezo-patch energy harvester on a thin plate with AC–DC conversion

As an alternative to beam-like structures, piezoelectric patch-based energy harvesters attached to thin plates can be readily integrated to plate-like structures in automotive, marine, and aerospace applications, in order to directly exploit structural vibration modes of the host system without mass loading and volumetric occupancy of cantilever attachments. In this paper, a multi-mode equivalent circuit model of a piezo-patch energy harvester integrated to a thin plate is developed and coupled with a standard AC–DC conversion circuit. Equivalent circuit parameters are obtained in two different ways: (1) from the modal analysis solution of a distributed-parameter analytical model and (2) from the finite-element numerical model of the harvester by accounting for two-way coupling. After the analytical modeling effort, multi-mode equivalent circuit representation of the harvester is obtained via electronic circuit simulation software SPICE. Using the SPICE software, electromechanical response of the piezoelectric energy harvester connected to linear and nonlinear circuit elements are computed. Simulation results are validated for the standard AC–AC and AC–DC configurations. For the AC input–AC output problem, voltage frequency response functions are calculated for various resistive loads, and they show excellent agreement with modal analysis-based analytical closed-form solution and with the finite-element model. For the standard ideal AC input–DC output case, a full-wave rectifier and a smoothing capacitor are added to the harvester circuit for conversion of the AC voltage to a stable DC voltage, which is also validated against an existing solution by treating the single-mode plate dynamics as a single-degree-of-freedom system.

A Numerical and Experimental Study of Optimal Velocity Feedback Control for Vibration Suppression of a Plate-Like Structure

This study presents a numerical and an experimental study on an active vibration control system. The system includes a fully-clamped plate and two surface bonded piezoelectric actuators and a collocated velocity sensor at one of the actuator locations. One of the piezoelectric actuators is used for disturbance actuation and the other one is used for control actuation. A model based optimal velocity feedback controller is used as control algorithm. The disturbance and actuator models are obtained through experimental characterization of the plate under the effect of the disturbance source. A representative SIMULINK model is built in parallel to the development of the experimental setup in order to investigate performance of the controller for various control parameters. After the model based optimal controller is designed, performance of the optimal velocity feedback controller is validated with the experimental study by comparing the vibration suppression values at multiple modes of the structure. Results show that the developed control methodology effectively suppresses the vibration amplitudes at multiple modes of the structure and also vibration attenuation levels can be predicted accurately with the simulations for various controller design parameters. It is also demonstrated that using an optimal controller enhances the performance of the system as opposed to just using velocity feedback algorithm for the active vibration control of the smart plate.

Multiple patch–based broadband piezoelectric energy harvesting on plate-based structures

Several engineering systems, such as aircraft structures, are composed of load-bearing thin plates that undergo vibrations and employ wireless health, usage, and condition monitoring components, which can be made self-powered using vibrational energy harvesting technologies. Integrated piezoelectric patches can be implemented for enabling self-powered sensors in the neighborhood of plate-based structures. In this work, coupled electroelastic modeling and experimental validations of broadband energy harvesting from structurally integrated piezoelectric patches on a rectangular thin plate are presented. A distributed-parameter electroelastic model for multiple patch–based energy harvesters attached on a thin plate is developed. Closed-form structural and electrical response expressions are derived for multiple vibration modes of a fully clamped thin plate for the series and parallel connection configurations of multiple patch–based energy harvesters. Experimental and analytical case studies are then compared for validating the analytical models of structurally integrated multiple patch–based energy harvesters. It is shown that analytical electroelastic frequency response functions exhibit very good agreement with the experimental frequency response function measurements for the series and parallel connection cases. In addition to offering an effective interface for energy harvesting from two-dimensional thin structures, series and parallel multiple patch–based energy harvester configurations yield effective broadband energy harvesting by combining the electrical outputs of harvester patches for multiple vibration modes.

Random vibration energy harvesting on thin plates using multiple piezopatches

Vibrational energy harvesting using piezoelectric cantilever beams has received significant attention over the past decade. When compared to piezoelectric cantilever-based harvesters, piezopatch energy harvesters integrated on plate-like thin structures can be a more efficient and compact option to supply electrical power for wireless structural health and condition monitoring systems. In this article, electroelastic modeling, analytical and numerical solutions, and experimental validations of piezopatch-based energy harvesting from stationary random vibrations of thin plates are presented. Electroelastic models for the series and parallel connected multiple piezopatches are given based on a distributed-parameter modeling approach for a thin host plate excited by a transverse point force. The analytical and numerical solutions for the mean power output and the mean-square shunted vibration response are then derived. The experimental measurements are carried out by employing a fully clamped thin plate with three piezopatches connected in series. It is shown that the analytical and numerical model predictions for the mean power output and the mean-square velocity response are in very good agreement with the experimental measurements. The electroelastic modeling framework and solution methods presented in this work can be used for design, performance analysis, and optimization of piezoelectric energy harvesting from stationary random vibration of thin plates.

Two-axis MEMS scanner for display and imaging applications

Two-axis gimbaled scanner used in an SVGA display product with 58deg optical scan angle, 1.5 mm mirror size, and 21 KHz resonant frequency is reported. Scanner is actuated electromagnetically using a single coil on the outer frame and by mechanical coupling of outer frame motion into the inner mirror frame

Model Validation Methodology for Design of Micro Systems

Micro Electro Mechanical Systems (MEMS) are the new and emerging technology of the future and have many applications on different disciplines like biomedical, imaging technology, biology etc. Predicting the dynamic performance and reliability characteristics of such systems early in the design process can impact the quality of the design. This paper presents our modeling, testing, and validation methodologies to predict the dynamic performance of micro systems. A two-dimensional torsional micro scanner mirror is chosen as the case study to demonstrate the developed methodologies. Modeling methodology includes modal analysis of the micro scanner using finite element modeling techniques. The validation methodology uses an experimental modal analysis set-up for measuring the dynamic characteristics of the scanner mirror. The finite element analysis and experimental results are compared to identify the inaccuracies in the modeling assumptions. Additionally, modal damping coefficients are also determined since they are critical to predict the response of such systems to external forces.Copyright