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...
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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...
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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 ...
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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...
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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...
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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.
Recent developments in adaptive composite structures with distributed multifunctional actuators and sensors have attracted significant attention in the research community due to their potential commercial benefits in ...
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Recent developments in adaptive composite structures with distributed multifunctional actuators and sensors have attracted significant attention in the research community due to their potential commercial benefits in a wide range of applications such as vibration suppression, shape control and noise attenuation. In this study, composite plate and shell finite element models with electromechanical properties are presented. The adaptive composite consists of a plate or shell structure with piezoelectric actuators either bonded or embedded as a laminate in the structure. Its applications in aircraft internal noise suppression are investigated. The underlying concept consists of stiffening the structure using the distributed electromechanical actuation.
This paper presents a neural network controller for a piezoelectric controlled structure by emulating the control performance of a Linear Quadratic Gaussian (LQG) controller. The configuration of the Artificial Neural...
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This paper presents a neural network controller for a piezoelectric controlled structure by emulating the control performance of a Linear Quadratic Gaussian (LQG) controller. The configuration of the Artificial Neural Network (ANN) is simple, yet it is efficient in terms of its high learning speed and good generalization ability. A case study is presented to demonstrate the performance of the ANN controller versus the LQG controller. The test results for different disturbances on the structure show excellent agreement between the ANN and LQG controllers.
Piezoelectric devices represent an important new group of actuators and sensors for active vibration control systems. Indeed, this technology allows to construct spatially distributed devices. A mathematical model of ...
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Piezoelectric devices represent an important new group of actuators and sensors for active vibration control systems. Indeed, this technology allows to construct spatially distributed devices. A mathematical model of a multilayered piezoelectric plate, which takes hysteresis and polarization of the piezoelectric laminae into account, is presented. Passive control for Lagrangian systems is used to derive a class of stabilizing control laws, which are based on the collocation of sensors and actuators. Therefore, the design of the spatial distribution of the sensors/actuators is considered as a part of the controller synthesis.
In high-precision motion systems, like wafer stages and electron microscopes, mechanical vibrations are a major point of concern. Often, these vibrations have small amplitudes (micrometers) and relatively high frequen...
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In high-precision motion systems, like wafer stages and electron microscopes, mechanical vibrations are a major point of concern. Often, these vibrations have small amplitudes (micrometers) and relatively high frequency (>50 Hz). The so-called smart Disc (a combined piezoelectric actuator and sensor) is a device that might be used to suppress these vibrations actively. The feasibility of the smart Disc concept is investigated, using an experimental set-up, consisting of a double mass-spring system, with two smart Discs. This system has two badly damped resonance modes, to be damped by the smart Disc(s), by means of feedback of the measured local interaction forces to the actuated displacements. The corresponding control problem, is to minimize the vibrations of the two masses, as a result of a disturbing force. With the experimental set-up, some aspects have been investigated. In the modelling phase, the system revealed high-frequent (3 kHz) resonance peaks, which appeared to originate from the smart Disc housings. These dynamics have been identified and taken into account in the control design. Because of these high-frequent dynamics near the Nyquist frequency, and the high gain at that frequency (which is inherent to the smart Disc concept) discrete time effects have been taken into account explicitly. Besides conventional active vibration control strategies, more sophisticated (MIMO H∞, discrete time) control design strategies have been applied successfully.
A coupled finite element/boundary element method is developed for the fully coupled structural/acoustic/piezoelectric system. This approach uses the dual reciprocity boundary element method to describe time dependent ...
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A coupled finite element/boundary element method is developed for the fully coupled structural/acoustic/piezoelectric system. This approach uses the dual reciprocity boundary element method to describe time dependent acoustic field and the finite element to structures and piezoelectric materials. A time-domain formulation of the coupled method is obtained. Based on the coupled time domain formulation, a linear quadratic regulator and a feedforward controller are applied to reduce the acoustic pressure transmitted into a cavity through a composite plate using embedded piezoelectric actuators. The controls of interior acoustic fields due to excitations at different frequencies are investigated, transmission losses and deflection of the plates of the controlled and uncontrolled systems are presented.
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