The paper first presents a general purpose finite element based simulation tool for piezoelectric controlled smartstructures. In addition to the standard finite elements, this tool contains a number of coupled electr...
详细信息
The paper first presents a general purpose finite element based simulation tool for piezoelectric controlled smartstructures. In addition to the standard finite elements, this tool contains a number of coupled electromechanical finite elements as well as numerical tools to simulate controlled structures in statics and dynamics. The effectiveness of a smart structure decisively depends on the amount and distribution of active materials across the passive structure and on the controller design. To solve this design problem automatically, a discrete optimization technique and ideas from topology optimization are presented. The control parameters are considered as continuous design variables. Mathematical solution algorithms for nonlinear, mixed continuous and discrete-valued optimization techniques are used to solve the optimization problem. As a test example the distribution of piezoelectric wafers over a beam structure is presented. Finally, this paper gives an outlook for new developments in this field.
In this paper, the finite-element/boundary-element program CAPA is presented, which has been developed by the authors during the last decade. With this software environment we are able to model quite different types o...
详细信息
In this paper, the finite-element/boundary-element program CAPA is presented, which has been developed by the authors during the last decade. With this software environment we are able to model quite different types of transducers which mostly ask for the numerical solution of a multifield problem, such as coupled electric-mechanical fields or magnetic-mechanical fields. Practical applications in the area of smartstructures will demonstrate the applicability of the developed software.
Adaptive structures optimal design problems and solution methods are presented and discussed for the cases of shape control and active damping. A general method to solve simultaneously optimal placement and control pr...
详细信息
Adaptive structures optimal design problems and solution methods are presented and discussed for the cases of shape control and active damping. A general method to solve simultaneously optimal placement and control problems for active damping applications is outlined. This method is based on a finite element structural model and on the calculation of the closed-loop system poles. Numerical results are given to illustrate this method for the case of a beam with collocated PZT sensor/actuator pair and a direct velocity feedback controller.
In this paper, the integrated finite element methodology developed in our earlier work for designing active vibration control strategies in smartstructures, is extended to compute the stresses and strains in the stru...
详细信息
In this paper, the integrated finite element methodology developed in our earlier work for designing active vibration control strategies in smartstructures, is extended to compute the stresses and strains in the structure, due to combined thermal, mechanical and electrical excitations. A layered composite brick elements with linear strain-displacement and linear thermopiezoelectric constitutive relations is used to model the structure. The method, which has been encoded into a software called smartCOM provides a design and analysis capability that simultaneously accounts for the coupled thermopiezoelectric and control capabilities of the smart structural systems. Numerical examples are provided for structures with surface bonded piezoelectric sensors and actuators, under various types of mechanical, thermal and electrical load. Comparisons are made to other available solutions to verify the accuracy of the smartCOM simulations. The method provides accurate results and is seen as a valuable tool for the design and analysis of these smartstructures.
Modeling of piezoelectric smartstructures including absorbing material was studied for cabin noise problems. The finite element method which uses a combination of three dimensional piezoelectric, flat shell and trans...
详细信息
Modeling of piezoelectric smartstructures including absorbing material was studied for cabin noise problems. The finite element method which uses a combination of three dimensional piezoelectric, flat shell and transition finite elements is adopted to model the piezoelectric active structure. The acoustic pressure in the cubic shaped cavity, is represented in terms of modes of the cavity and the absorbing material is modeled using surface acoustic impedance. Finally, the effect of the cavity pressure is introduced in the finite element equations. The simulation result of sound pressure in the cavity is compared with an experiment and they show a good agreement. The cavity pressure is reduced in a wide frequency range except the resonance frequencies of the plate by applying absorbing material. It can be concluded that the piezoelectric smartstructures with absorbing materials can be creative technology for cabin noise problems.
One important component in the development of many smartstructures and microdevices is the growth of thin films. The control of the growth processes, therefore, is of interest. In the design of a control system for m...
详细信息
One important component in the development of many smartstructures and microdevices is the growth of thin films. The control of the growth processes, therefore, is of interest. In the design of a control system for molecular beam epitaxy (MBE), it is important to have simple mathematical models that describe the different growth morphologies that a growing film may exhibit and incorporate atomic-scale information. Of the three types of models currently being considered (atomistic, continuum, and bulk), bulk models have the most interest to control. Still, due to the complexity of such models, however, a model reduction must be carried out to make real-time control possible. A model reduction routine based on a new version of the nonlinear Galerkin methods is proposed and explained for three different bulk models. A total reduction of one-third the number differential equations is obtained.
Integration of controllers with smart structural system require the controllers to consume less power and to be small in hardware size. These requirements pose as limits on the control input and the order of the contr...
详细信息
Integration of controllers with smart structural system require the controllers to consume less power and to be small in hardware size. These requirements pose as limits on the control input and the order of the controllers. Use of reduced order model of the plant in the controller design can cause spill over problems in the closed loop system due to possible excitation of the unmodeled dynamics. In this paper we present the design of output feedback robust controllers for smartstructures in the presence of control input limits considering unmodeled dynamics as additive uncertainty in the design. The performance requirements for the design are specified as regional pole placement constraints on the closed loop poles. Formulation of this multi-objective design problem in terms of matrix inequalities resulted in a feasibility problem involving bilinear matrix inequalities (BLMIs) in the unknown variables. To facilitate the solution of this feasibility problem, a change of variables is used to convert these BLMIs into linear matrix inequalities (LMIs) which can be readily solved by the use of available tools. Finally, this design procedure is applied on a experimental smart structure and the results are presented.
A one-dimensional model for shape memory alloys is presented that permits the simulation of actuatoric behavior. It is an improved version of the Muller-Achenbach single crystal model and calculates the length change ...
详细信息
A one-dimensional model for shape memory alloys is presented that permits the simulation of actuatoric behavior. It is an improved version of the Muller-Achenbach single crystal model and calculates the length change as a response to electric heating. Based on this model, a polycrystalline version is developed, which is shown to be in excellent agreement with experimental results. Finally, as an illustrative application, a real-time control is calculated for an adaptive beam using SMA actuators.
smartmaterials and structural systems are increasingly attracting attention from the engineering community because of their importance in current and future high performance structural applications. As these new stru...
详细信息
smartmaterials and structural systems are increasingly attracting attention from the engineering community because of their importance in current and future high performance structural applications. As these new structural systems emerge, there is an important need to have capabilities that can be employed for assessing their performance with reference to the primary functional requirement of structural integrity and control robustness as well as reliability. Furthermore, it is desirable to establish adequate performance metrics (which account for inherent or environmental uncertainties) that can be used as a quantitative basis for the comparative evaluation of various design options or for assessing the state of such systems that are already in service. In this study, two measures that can be used for probabilistic characterization and assessment of the performance of actively controlled smartstructures are developed. The framework is based on the use of the probabilistic finite element strategy for modelling the parent (host) structure as well as the piezoelectric materials that are employed for sensing and actuation in the assembled system. The uncertainties inherent in the parent structure and the piezoelectric materials are propagated through the probabilistic finite element model. This enables rational and realistic characterization of the performance measures. The probabilistic models are based on the use of advanced reliability analysis algorithms which utilize fast probability integration algorithms that are robust and computationally more efficient than Monte Carlo simulation schemes. To facilitate efficient computation, an adaptive response surface methodology is employed for the approximation of the probabilistic finite element response quantities. Example problems are used to illustrate the robustness and usefulness of the proposed methodology.
The incorporation of an active control system into an aerospace structure as part of a smart structure has raised the issue of: How does the controller respond when the structure is damaged? The answer is usually depe...
详细信息
The incorporation of an active control system into an aerospace structure as part of a smart structure has raised the issue of: How does the controller respond when the structure is damaged? The answer is usually dependent on the answer to numerous other questions regarding the type of controller, the type of damage, the application of the smart structure, etc. However, previous research has indicated that the Direct Model Reference Adaptive control (DMRAC) algorithm has potential in preventing the damaged smart structure from becoming unstable. Maintaining stability following an impact damage is of minimal usefulness if the controller can not also provide satisfactory performance before the damage event. This paper presents the simulation results of research comparing a velocity and position feedback controller with a DMRAC controller. The primary areas of concern were the undamaged performance (damping augmentation) and the damaged performance (stability and steady state response). The traditional controller design performed better before the damage occurred, but the DMRAC controller was significantly better after the damage occurred.
暂无评论