Jung-Woo Sohn

An investigation on piezoelectric energy harvesting for MEMS power sources

Abstract This paper presents the feasibility of using piezoelectric materials in a power source for micro-electro-mechanical systems (MEMS) devices. The finite element method (FEM) is adopted to evaluate the power generations of commercially available piezofilms that are subjected to a fluctuating pressure source (blood pressure). The accuracy of the results obtained from the FEM is verified by comparing with the corresponding results obtained from a theoretical analysis. In addition, an experiment is undertaken in order to evaluate the power generation of two different shapes of the piezofilms: square and circle. Finally, a brief discussion is made on the storage of experimentally harvested power and use of the MEMS applications.

Vibration and Position Tracking Control of a Flexible Beam Using SMA Wire Actuators

This paper presents vibration and position control of a flexible beam structure by adopting shape memory alloy (SMA) wire actuators. The governing equation of motion of the proposed flexible structure is obtained via Hamiltons principle. The dynamic characteristics of the SMA wire actuator are experimentally identified and incorporated with the governing equation to furnish a control system model in the state space. Subsequently, a sliding mode controller which has inherent robustness to external disturbances and parameter uncertainties is formulated. The controller is then empirically realized for vibration control with relatively large tip displacement. In addition, tip position tracking control to follow desired trajectories with low-frequency sine and square waves is undertaken. Control performances such as tracking error are evaluated through both computer simulation and experimental investigation in time domain.

Road test evaluation of vibration control performance of vehicle suspension featuring electrorheological shock absorbers

Abstract This work presents road test results for vibration control of a vehicle suspension system equipped with continuously controllable electrorheological (ER) shock absorbers. The test vehicle is a mid-sized passenger car whose suspension systems are typical Macpherson strut types for the front part and multilink types for the rear part. The four ER shock absorbers (two for the front suspension and two for the rear suspension) are devised based on design specifications for the test vehicle and their damping forces are experimentally evaluated with respect to the electric field. The ER shock absorbers and conventional spring elements are then assembled into suspension systems. Prior to undertaking the road test, the front ER suspension is applied to the quarter-car facility in order to validate control performance of the skyhook controller embedded in on-chip hardware. Subsequently, the full-vehicle model incorporating four ER suspensions is established and the skyhook control gains are determined in an optimal manner. The controller is then implemented on the test vehicle which is equipped with several sensors, a data acquisition system, and high-voltage amplifiers. Control performances are evaluated under various road conditions (bump, long waved, rugged, paved, and unpaved) and presented in both time and frequency domains.

Active vibration control of smart hull structures using piezoelectric actuators

Abstract In this study, dynamic characteristics of an end-capped hull structure with surfacebonded piezoelectric actuators are studied and active vibration controller is designed to suppress the undesired vibration of the structure. Finite-element modelling is used to obtain practical governing equation of motion and boundary conditions of smart hull structure. A modal analysis is conducted to investigate the dynamic characteristics of the hull structure. Piezoelectric actuators are attached where the maximum control performance can be obtained. Active controller on the basis of a linear quadratic Gaussian (LQG) theory is designed to suppress the vibration of smart hull structure. It is observed that closed-loop damping can be improved with suitable weighting factors in the developed LQG controller and the structural vibration can be successfully suppressed.

Dynamic Modeling and Vibration Control of Smart Hull Structure

Dynamic modelingand active vibration control of smart hull structure using Macro Fiber Composite (MFC) actuators are conducted. Finite element modeling is used to obtain equations of motion and boundary effects of smart hull structure. Modal analysis is carried out to investigate the dynamic characteristics of the smart hull structure, and compared to the results of experimental investigation. Negative velocity feedback control algorithm is employed to investigate active damping of hull structure. It is observed that non-resonant vibration of hull structure is suppressed effectively by the MFC actuators.

Vibration Suppression of Hull Structure Using MFC Actuators

Performance evaluation of advanced piezoelectric composite actuator is conducted with its application of structural vibration control. Characteristics of MFC(macro fiber composite) actuator are investigated by comparing traditional piezoceramic patch actuator. Finite element modeling is used to obtain equations of motion and boundary effects of smart hull structure with MFC actuator. Dynamic characteristics of the smart hull structure are studied through modal analysis and experimental investigation. LQG control algorithm is employed to investigate active damping of hull structure. It is observed that vibration of hull structure is suppressed effectively by the MFC actuators.

Performance Characteristics of High Speed Jetting Dispenser Using Piezoactuator

This paper presents a new jetting dispenser driven by a piezoelectric actuator at high operating frequency to provide very small dispensing dot size of adhesive in modern semiconductor packaging processes. After describing the mechanism and operational principle of the dispenser, a mathematical model of the structured system is derived by considering behavior of each component such as piezostack and dispensing needle. In the fluid modeling, a lumped parameter method is applied to model the adhesive whose rheological property is expressed by Bingham model. The governing equations are then derived by integrating the structural model with the fluid model. Based on the proposed model, dispensing performances such as dispensing amount are investigated with respect to various input trajectories.

A New Type of Active Engine Mount System Featuring MR Fluid and Piezostack

An engine is one of the most dominant noise and vibration sources in vehicle systems. Therefore, in order to resolve noise and vibration problems due to engine, various types of engine mounts have been proposed. This work presents a new type of active engine mount system featuring a magneto-rheological (MR) fluid and a piezostack actuator. As a first step, six degrees-of freedom dynamic model of an in-line four-cylinder engine which has three points mounting system is derived by considering the dynamic behaviors of MR mount and piezostack mount. In the configuration of engine mount system, two MR mounts are installed for vibration control of roll mode motion whose energy is very high in low frequency range, while one piezostack mount is installed for vibration control of bounce and pitch mode motion whose energy is relatively high in high frequency range. As a second step, linear quadratic regulator (LQR) controller is synthesized to actively control the imposed vibration. In order to demonstrate the effectiveness of the proposed active engine mount, vibration control performances are evaluated under various engine operating speeds(wide frequency range) and presented in time domain.

Dynamic and control characteristics of 3-axis active mount system using piezoelectric actuators

This work presents dynamic characteristics of 3-axis active mount featuring the rubber element and the piezoelectric actuator. The rubber element is adopted to isolate external disturbance in the non-resonance frequency range, while the piezoactuator is employed to isolate the vibration in the neighborhood of the resonance. After identifying dynamic properties of the rubber element and the piezoactuator in the frequency domain, the governing equation of the active mount system is derived. Subsequently, generated force and moment of each actuator is evaluated in time domain. In addition, a comparative work between the simulation and measurement is undertaken.

Active Vibration Control of Smart Hull Structure Using MFC Actuators

Active vibration control of smart hull structure using Macro Fiber Composite (MFC) actuator is performed. Finite element modeling is used to obtain governing equations of motion and boundary effects of end-capped smart hull structure. Equivalent interdigitated electrode model is developed to obtain piezoelectric couplings of MFC actuator. Modal analysis is conducted to investigate the dynamic characteristics of the hull structure, and compared to the results of experimental investigation. MFC actuators are attached where the maximum control performance can be obtained. Active controller based on Linear Quadratic Gaussian (LQG) theory is designed to suppress vibration of smart hull structure. It is observed that closed loop damping can be improved with suitable weighting factors in the developed LQG controller and structural vibration is controlled effectively.