Clinton Chee

A Review on the Modelling of Piezoelectric Sensors and Actuators Incorporated in Intelligent Structures

The main objective of this article is to present an overview of the modelling that has been proposed by various workers in the field of smart or intelligent structures. Before the main discussion on the various models, some background information will be presented in relation to intelligent structures and the types of adaptive materials that are available. Although there are several categories of materials that can be implemented in intelligent structures, this article will focus on models that use piezoelectric materials as sensors and/or actuators (S/A). The modelling of the intelligent structures can be categorised in terms of the structural configuration (e.g., rod composites, fibre composites, monolithic structures, etc.) and also according to the type of modelling whether by finite element modelling or by analytical exact solutions. Models in this field of work had incorporated concepts from different background including three-dimensional linear elastic theory and dielectric theory to give rise to the linear piezoelectric model. Rules of Mixture and methods for calculating effective properties of fibre composites were extended to include piezoelectric fibre composite models. Classical Laminated Plate Theory was also adopted in laminated composite models where some laminae were piezoelectric materials. Exact solutions were applied to simple models and illustrated the potential of using piezoelectrics. Finite element techniques were used for more complicated problems that included complex geometries, nonlinear behaviour and dynamic control of the structure. The difference between induced strain and actuation strain is usually not addressed when using FE techniques, instead the piezoelectric strain can be regarded as an equivalent external force/moment or incorporated into the strain energy. In regard to control algorithms, the most common form applied by investigators in this field seems to be the negative velocity feedback control with single input and single output and some included linear quadratic control. More advanced control algorithms such as using multiple input and multiple output or even neural networks are less established.

A mixed model for composite beams with piezoelectric actuators and sensors

A theoretical formulation to model composite smart structures in which the piezoelectric actuators and sensors are treated as constituent parts of the entire structural system is presented here. The mathematical model is based on a high order displacement field coupled with a layerwise linear electric potential. This model is developed for a composite beam structure using Hamiltons variational principle and is facilitated by the finite element (FE) formulation. The generic element implemented in the FE analysis is a two-noded Hermitian - 2(n+1) layerwise noded element for an n-layered beam. The variational principle led to a derivation that could include dynamic analysis but the present work will only focus on the static beam structure. This formulation in general will enable the modeling of vibration and shape control applications. Comparison of numerical results from this formulation with previous works, including three configurations - non-piezoelectric, actuator and sensor configurations, showed a high to a reasonable degree of correlation. The effects of varying actuator locations and orientations on the deflection and curvature of the beam were also studied.

A mixed model for adaptive composite plates with piezoelectric for anisotropic actuation

Abstract A theoretical formulation for modelling composite smart structures, in which the piezoelectric actuators and sensors are treated as constituent parts of the entire structural system, is presented. The mathematical model is based on a High Order Displacement field coupled with a Layerwise Linear electric potential. This model is developed for a composite laminated plate structure using Hamilton’s variational principle with the Finite Element (FE) formulation. The performance of the 8 node element was found to be superior to the four node element for very thin structures. This formulation was verified using existing FE software and results from literature. Investigation into the effects of different actuator locations, orientations and electric field directions illustrate anisotropic actuation capabilities. Then the variation in mechanical and piezoelectric anisotropy was also examined.

Piezoelectric actuator orientation optimization for static shape control of composite plates

A heuristic and intuitive algorithm is presented for the determination of the orientation of piezoelectric actuator patches in the application to shape control of smart structures. The fundamental concept of this approach is similar to another method developed by the same authors for voltage optimization, but the implementation of the current algorithm is significantly different. The mathematical model of the smart structure is based on a high order displacement (HOD) field coupled with a layerwise linear electric potential. The current shape control work will make use of the finite element formulation based on the above-mentioned mathematical model. The performance of the shape control algorithm were examined via the least squares errors in terms of displacements, slopes and curvatures as well as electrical input and effective anisotropy of actuators. The results show that the shape conformity of certain structural configurations were improved considerably by the application of the orientation shape control algorithm.

Static Shape Control of Composite Plates Using a Slope-Displacement-Based Algorithm

An intuitive approach for the determination of voltage distribution in the application to shape control of smart structures using piezoelectric actuators is presented. This novel approach introduces slope as the fine-tuning criterion on top of the common displacement-based shape control. The algorithm, called the perturbation buildup voltage distribution is based on an iterative approach inspired by a previous algorithm on displacement control. This method aims to provide a means of targeting the desired shape of a structure with a higher-order criterion such as slope. A natural consequence of this method is the smoothing of the resultant structure. This effect will be illustrated by numerical examples. Iterative parameters are varied to investigate favorable choices of the parameters. Results show that the slopes of the structure can be improved, but at a tolerable expense of the displacement criteria. Another result of practical interest is the reduction of internal stresses compared to cases using pure displacement shape control.

Static shape control of composite plates using a curvature-displacement based algorithm

Abstract An intuitive algorithm for the determination of voltage distribution in the application to shape control of smart structures using piezoelectric actuators is presented here. This approach uses curvature as the fine-tuning criteria on top of the common displacement-based shape control, and is an extension of the slope–displacement method developed by the same authors. The algorithm called the perturbation buildup voltage distribution (PBVD) is based on an iterative approach inspired by a previous algorithm BVD on displacement control. This method aims to provide a means of targeting the desired shape of a structure by using a higher level shape attribute, in this case curvature. Intuitive iterative parameters of the PBVD method allow the user to have better control over the degree of conformity of the structure’s shape. A natural consequence of this method is the smoothing of the resultant shape. Results show that the slopes and curvatures of the structure can be improved but at a tolerable expense of the displacement criteria. Another result of practical interest is the reduction of internal stresses compared to cases using pure displacement shape control.

CIMA Based Remote Instrument and Data Access: An Extension into the Australian e-Science Environment

The Common Instrument Middleware Architecture (CIMA) is being used as a core component of a portal based remote instrument access system being developed as an Australian e-Science project. The CIMA model is being enhanced to use federated Grid storage infrastructure (SRB), and the Kepler workflow system to, as much as possible, automate data management, and the facile extraction and generation of instrument and experimental metadata. The Personal Grid Library is introduced as a user friendly portlet interface to SRB data and metadata, and which supports customisable metadata schemas. An Instrument Instruction Module has been introduced as a CIMA plug-in for instrument control. A virtual instrument portlet provides a simulation of the instrument during a data collection. The system is being further augmented with a tool for collaborative data visualisation and evaluation.

Remote instrument control with CIMA Web services and Web 2.0 technology

The Common Instrument Middleware Architecture (CIMA) model for Web services based monitoring of remote scientific instruments is being extended and enhanced to provide a capability for remote instrument control. X-ray diffraction has been selected as an ideal domain for prototype development, with the goal being a comprehensive and feature rich portal system for access to remote instruments and their data. The system has two principle components, one of which serves the instrument and data, and the second serves the client user. Plugin modules are used to provide flexibility and re-use, and the notion of plugin control is being developed. The architecture supports remote access to multiple instruments from a single portal. The use of Web 2.0 Pushlet and AJAX technologies has been introduced for push based portlet refresh and updating. An X3D based 3D virtual representation of the instrument provides data collection simulation and (pseudo) real time instrument representation.

Shape functions generation using Macsyma

An algorithm for the generation of general shape functions is presented here. The algorithm is coded using the Macsyma program which has symbolic/algebraic manipulation capabilities. The current technique is based on the direct approach of calculating shape functions which is seldom used due to manual algebraic tediousness. Listing of the code is included in this paper as well as examples showing how it correctly generates some of the common shape functions with ease. Two examples of new shape functions were created for C2 elements. Hence, the more useful purpose of this algorithm is that it can be used to investigate the existence of new types of shape functions by making use of the power of symbolic computational software. Copyright

Portal Services for Collaborative Remote Instrument Control, Monitoring and Data Access

A two component portal system is being developed for collaborative remote instrument and data control and monitoring. The system builds on and enhances the common instrument middleware architecture (CIMA) model for Web services based monitoring of remote scientific instruments and sensors. The architecture supports remote access to multiple instruments from a single portal. Plugin modules are used to provide flexibility and re-use, and the notion of plugin control is being developed. The use of Web 2.0 Pushlet and AJAX technologies has been introduced for push based portlet refresh and updating. An X3D based 3D virtual representation of the instrument provides data collection simulation and (pseudo) real time instrument representation. An important component of the system is a Webs services driven portlet for collaborative image viewing.