Fanping Sun

Coupled Electro-Mechanical Analysis of Adaptive Material Systems-Determination of the Actuator Power Consumption and System Energy Transfer

This article presents a coupled electro-mechanical analysis of piezoelectric ceramic (PZT) actuators integrated in mechanical systems to determine the actuator power consumption and energy transfer in the electro-mechanical systems. For a material system with integrated PZT actua tors, the power consumed by the PZT actuators consists of two parts: the energy used to drive the system, which is dissipated in terms of heat as a result of the structural damping, and energy dissi pated by the PZT actuators themselves because of their dielectric loss and internal damping. The coupled analysis presented herein uses a simple model, a PZT actuator-driven one-degree-of- freedom spring-mass-damper system, to illustrate the methodology used to determine the actuator power consumption and energy flow in the coupled electro-mechanical systems. This method can be applied to more complicated mechanical structures or systems, such as a fluid-loaded shell for active structural acoustic control. The determination of the actuator power consumption can be very im portant in the design and application of intelligent material systems and structures and of particular relevance to designs that must be optimized to reduce mass and energy consumption.

Truss Structure Integrity Identification Using PZT Sensor-Actuator

This paper presents a frequency domain impedance-signature-based technique for health monitoring of an assembled truss structure. Unlike conventional modal analysis approaches, the technique uses piezoceramic (PZT) elements as integrated sensor-actuators for acquisition of signature pattern of the truss. The concept of the localization of sensing/actuation area for damage detection of an assembled structure is presented for the first time. Through a PZT patch bonded to a truss node and the measurement of its electric admittance, which is coupled with the mechanical impedance of the truss, the signature pattern of a truss is monitored. The admittance of a truss in question is compared with that of the original healthy truss. Statistic algorithm is then applied to extract a damage index of the truss based on the signature pattern difference. Experimental proof that over a selected band, the detection range of a bonded PZT sensor on a truss is highly constrained to its immediate neighborhood is presented. This characteristic allows accurate determination of the damage location in a complex real-world structure with a minimum mathematical modeling and numerical computation.

Electro-mechanical impedance modeling of active material systems

An active material system may be generalized as an electro-mechanical network because of the incorporation of actuators (electrically driven) and sensors (that convert mechanical energy into electrical energy). An investigation of the coupled electrical and mechanical aspects of an active material system will help reveal some of its most important characteristics, in particular regarding energy conversion and consumption issues. The research performed in the area of the electro-mechanical impedance (EMI) modeling of active material systems is herein summarized. In this paper, a generic EMI model to describe the electro-mechanical network behavior (time domain and frequency domain) of active material systems will be discussed. The focus of the discussion will be on the methodology and basic components of the EMI modeling technique and its application to assist in the design of efficient active control structures. This paper will first introduce the basic concept of the EMI modeling and its general utility in the area of active material systems. The methodology of the EMI modeling technique will be illustrated using an example of PZT actuator-driven mechanical systems. The basic components of the EMI modeling, including the electro-mechanics of induced strain actuators, the dynamic analysis of active material systems, and the electrical power consumption and requirements, will be discussed. Finally, some applications of the EMI modeling approach, including the determination of the optimal actuator locations, modal analysis using collocated PZT actuator - sensors, and the prediction of radiated acoustic power, will be presented.

Determination of Design of Optimal Actuator Location and Configuration Based on Actuator Power Factor

In this paper, a new design algorithm is proposed for optimization of the inducedstrain actuator location and configuration for active vibration control based on an actuator performance index, namely the actuator power factor. The concept of actuator power factor, developed recently by the authors, describes the capability of an integrated induced strain actuator, such as PZT or Terfenol, to transfer the supplied electrical energy into structural mechanical energy (kinetic or potential energy of the mechanical system). A system optimized based on the actuator power factor will guarantee the highest energy efficiency for single frequency and broad-band applications. This paper will also show that a higher energy efficiency corresponds to higher mechanical performance. The approach introduced in this paper is much more convenient to use than the conventional modal domain optimization approach. Furthermore, since the power factor approach can include the electrical parameters from the power system, it will allow a system optimization design including the power electronics and energy consumption. The basic concept of the actuator power factor will be introduced first in this paper. Its utility in the system optimization will be discussed using a PZT actuator-driven simply-supported beam. The optimization of actuator location, length, and thickness will be discussed through numerical examples. This paper will also discuss how to use the actuator energy density and actuator power factor to estimate the dynamic response of a system.

An Impedance Method for Dynamic Analysis of Active Material Systems

This paper describes a new approach to analyzing the dynamic response of active material systems with integrated induced strain actuators, including piezoelectric, electrostrictive, and magnetostrictive actuators. This approach, referred to as the impedance method, has many advantages compared with the conventional static approach and the dynamic finite element approach, such as pin force models and consistent beam and plate models. The impedance approach is presented and described using a simple example, a PZT actuator-driven one-degree-of-freedom spring-massdamper system, to demonstrate its ability to capture the physics of adaptive material systems, which is the impedance match between various active components and host-structures, and its utility and importance by means of an experimental example and a numerical case study. The conventional static and dynamic finite element approaches are briefly summarized. The impedance methodology is then discussed in comparison with the static approach. The basic elements of the impedance method, i.e., the structural impedance corresponding to actuator loading and the dynamic output characteristics of PZT actuators, are addressed. The advantages of using the impedance approach over conventional approaches are discussed using a simple numerical example. A comparison of the impedance method with the static and the dynamic finite element approaches are provided at the conclusion of this paper.

Debond Detection Using Broad-Band High-Frequency Excitation and Non-Contacting Laser Vibrometer System

A membrane vibration-based method of detecting a debond between a host structure and a composite repair patch is presented. The two distinguishing features of this new method are the excitation and the measurement. The excitation uses a non-instrusive surface-mounted piezoceramic patch and a broad-band high-frequency multi-sine sweep. The measurement uses a noncontacting laser vibrometer and converts the broad-band excitation response into a single value equal to the RMS value of the velocity. The frequency band is selected such that the local membrane vibration of the debonded area is excited, resulting in relatively higher velocity in the debond area. The work is principally experimental with a theoretical justification of the membrane resonance detection technique. Two case studies of glass/epoxy repair patches bonded to aluminum plates with corner and edge debonds, respectively, are presented. In this work, it is shown that accurate detection of composite repair patch debonds is achievable.