Control Of Smart Structures Research Articles

A single-walled carbon nanotube reinforced 1–3 piezoelectric composite for active control ofsmart structures

We propose a new 1–3 piezoelectric composite comprised of armchair single-walled carbonnanotubes imbedded in a piezoceramic matrix which we call a NRPEC (nanotubereinforced 1–3 piezoelectric composite). Values of effective piezoelectric and elastic moduliof the NRPEC determined through a micromechanical analysis are found to be significantlyhigher than those of the 1–3 piezoelectric composite comprised of piezoelectric fibersimbedded in an epoxy matrix. The performance of the NPREC as a constraining layer inan active constrained layer damping (ACLD) treatment of a laminated composite beamhas been studied by the finite element method. Both in-plane and out-of-planeactuations by the constraining layer of the ACLD treatment have been considered, andits length has been optimized by implementing a controllability criterion. Thecomputed controllability measure and the frequency response reveal that the proposedconstraining layer performs better than the 1–3 piezoelectric/epoxy composite layer.

MIMO adaptive vibration control of smart structures with quickly varying parameters: Neural networks vs classical control approach

This paper presents experimental adaptive identification and control of smart structures using neural networks based on system classification technique. An inverted L-structure with surface-bonded piezoceramic sensors/actuators is used for analysis. The state space, as well as matrix fraction description presentation, from control input voltages to output sensor voltage, is established in multivariable form. It is observed that the computational time required for online parameter identification and controller design is generally quite high. For the system, whose parameters change abruptly with large amplitudes, classical adaptive control techniques give poor transient behavior and sometimes instability. Also, for obtaining the ideal closed-loop performance, linear quadratic regulator cannot be re-designed in real-time for changed parameters of the smart structures, even if these parameters are identified in real time. Closed-loop identification of system parameters and control gains using system classification-based neural networks is proposed and implemented. A preliminary experimental study is also done to see the effectiveness of the proposed technique over classical control methods.

Energy transduction analyses of piezoelectric based vibration control of smart structures

Passive vibration shunt control using piezoelectric materials and an electrical network can remove vibration energy from structures. However, the vibration shunt control efficiency relies on the optimization of the vibration energy transfer between a structure and a Lead-Zirconate-Titanate piezoelectric ceramic material. We present an analytical study of a parallel resistor-inductor piezoelectric vibration shunt control on a beam structure using Hamilton's principle and Galerkin's method. The influence of the material's mechanical property on vibration energy transfer between the structure and the Lead-Zirconate-Titanate is discussed. The results of the vibration shunt control with various materials obtained from numerical modeling and experiments are discussed and corroborated.

Extension of Projectile Range Using Oblique-Wing Concept

*† ‡ An innovative projectile design using body-conformal oblique wing/tails with smartstructure (actuator) control has been proposed to achieve an extended range without rocket assistance. This guided projectile would maintain the maximum lift-to-drag ratio throughout its gliding phase, from supersonic, through transonic, to subsonic gliding regimes. In the present work, intensive Navier-Stokes computations using the overset-grid approach have been performed to search for the optimal sweepback positions of the oblique wing for the given pairs of Mach numbers and the angles of attack in the supersonic and transonic gliding phases. With such an optimal deployment of the oblique wing, as shown in our preliminary two degrees-of-freedom trajectory analysis, it is feasible for the projectile to achieve the target 100 nm range without rocket assistance.

Design of Simultaneous Periodic Output Feedback Control for Smart Structures

This paper presents the problem of modelling simultaneous periodic output feedback control design to control the first two vibration modes of a flexible smart cantilever beam. The entire structure is modeled by finite element method using a piezoelectric beam element which includes a piezoelectric sensor and actuator dynamics. Simulation results demonstrate that a single controller can be employed to control the first two vibration modes for six different sensor/actuator locations along the beam. Application of simultaneous control introduces a redundancy in smart structure control.

2221 スマート構造のエネルギー回生振動制御に関する研究(スマート構造システム同定・振動制御・診断)

Energy consumption of actuator is thought as a disadvantage of active vibration control. However, the actuator of active vibration control system absorbs energy from vibrating structure to suppress the vibration. In other words, the actuator regenerates energy from the vibrating structure. Especially, piezoelectric actuator often used in smart structures can regenerate energy effectively, because it has few internal energy loss. Energy consumption of active control system is not caused by the actuator but caused by energy loss of conventional linear amplifier to drive the actuator. Recently, class D amplifier based on switching circuit has been utilized due to its high-efficiency. It can regenerate energy automatically from the load without loss under the ideal condition when the power consumption of the load is negative. Therefore, the energy regenerative active vibration control system can be realized by using the class D amplifier to drive the actuator. In this paper, we show the validity of the energy regenerative active vibration control of smart structure using the class D amplifier by numerical simulation of a smart cantilever beam with a piezoelectric actuator driven by a class D amplifier.

Extensive Experiments on Genetic Algorithms for the Optimization of Piezoelectric Actuator Locations

For shape control of smart structures, we have developed a series of micro-genetic-algorithms for optimal placement of a large number of piezoelectric actuators. Here, we investigate the effect on the solution quality of 1) different random seed generators; 2) restart criteria in micro-genetic-algorithms, specifically the two parameters, the number of generations used for the inner loop and the level of diversity in the population; and 3) different numbers of actuators. We also report a comparison of our genetic algorithms with two heuristic integer programming algorithms: worst-out-best-in and exhaustive single point substitution proposed by Haftka and Adelman (Selection of Actuator Locations for Static Shape Control of Large Space Structures by Heuristic Integer Programming, Computers and Structures, Vol. 20, 1985, pp. 572-582). Using current genetic algorithms, we not only get better layouts of actuators than reported in our previous publications, but we also find that the most distinct nature of genetic algorithms is randomness and robustness. The best parameter setting of genetic algorithms is dependent on both the number of evaluations used for termination and the seed generator used. Moreover, the best parameter setting of genetic algorithms varies as the number of actuators changes. To get the highest quality of solutions, multiple runs using different random seed generators are necessary. The time of investigation can be significantly reduced using a coarse grain parallel computing. Comparison of our genetic algorithms with the worst-out-best-in and exhaustive single point substitution shows that for a group of runs our genetic algorithms usually converge faster in the first few thousand evaluations and are more likely to find better solutions than the worst-out-best-in and exhaustive single point substitution algorithms.

Piezo actuator placement and sizing for good control effectiveness and minimal change inoriginal system dynamics

Piezoelectric actuators are commonly considered for active vibration control of smartstructures. The placement and sizing of the actuators are normally decided basedon control effectiveness. A piezo actuator affects the host structure’s mass andstiffness properties and thus alters the original system, which would have beendesigned to have a certain natural frequency spectrum in relation to the disturbanceexcitation. For a rotating structure, the mass of the actuator additionally contributesto the centrifugal stiffening effect. In the event of failure of the active system,natural frequencies of the structure with piezos (now rendered passive) becomesignificant. Considering the example of a stationary and rotating beam-like structure,it is attempted to identify the piezo actuator sizing and location that possesssignificant control effectiveness yet cause minimal change in the system dynamics.

Hybrid modeling for the active control of multibody smart structures – modeling validation

This study deals with the modeling of multibody smart structures including distributed piezoelectric actuators and sensors. The hybrid modal-nodal (HMN) modeling method proposed for modal active control is based on a modal modeling of structural behavior and a nodal modeling of piezoelectric behavior independent of each other. The electromechanical coupling modeling is validated by applying it to a clamped-free smart beam model. The accuracy of the HMN method is shown by comparison with other modeling methods and experiment. Then, a hub-beam application including electromechanical couplings as well as mechanical couplings between rigid body modes and flexible modes is described. The corresponding modeling, the experiment and the comparison of the results are presented. This application demonstrates that the HMN method provides an appropriate and efficient solution for the predictive modeling and control of multibody smart structures with complex assemblies and geometries.

Adaptive hybrid control of smart structures subjected to multiple disturbances

In the present work, it is observed that, to maintain stability, different sets offeedback control gains should be applied for free and forced vibration attenuation.For forced vibrations, feedback controllers with certain optimum positions ofclosed loop poles give maximum vibration reduction. By combining the feedbackand feed forward controllers (i.e. by using a hybrid controller), better transientperformance can be obtained in the case of forced vibrations. By using the concept of adead zone and making the hybrid controller adaptive, ideal performance andguaranteed stability of the closed loop system can be achieved for both free and forcedvibrations. The proposed controller remains effective for large variation in systemparameters.

Adaptive vibration control of smart structures: a comparative study

Fixed gain controllers, designed for a nominal system, degrade in performance whenthe system parameters are perturbed. By making the controller adaptive, idealperformance and granted stability of the closed loop system can be achieved for even alarge change in system parameters. In the present study, adaptive controllersbased on minimum variance, pole placement and linear quadratic techniquesare investigated. The controller based on minimum variance is noise sensitiveand the actuator voltage changes sign after each sampling interval. Hence, it isdetrimental to the life of piezoelectric actuators. An adaptive controller based on thepole placement technique requires high control effort and gives poor performanceat and near the nominal system. But linear quadratic control based adaptivecontrollers are noise tolerant and are free from the above-mentioned limitations.

Vibration control of piezoelectric smart structures based on system identification technique: Numerical simulation and experimental study

The aim of this study is to investigate the efficiency of a system identification technique known as observer/Kalman filter identification (OKID) technique in the numerical simulation and experimental study of active vibration control of piezoelectric smart structures. Based on the structure responses determined by finite element method, an explicit state space model of the equivalent linear system is developed by employing OKID approach. The linear quadratic Gaussian (LQG) algorithm is employed for controller design. The control law is then incorporated into the ANSYS finite element model to perform closed loop simulations. Therefore, the control law performance can be evaluated in the context of a finite element environment. Furthermore, a complete active vibration control system comprising the cantilever plate, the piezoelectric actuators, the accelerometers and the digital signal processor (DSP) board is set up to conduct the experimental investigation. A state space model characterizing the dynamics of the physical system is developed from experimental results using OKID approach for the purpose of control law design. The controller is then implemented by using a floating point TMS320VC33 DSP. Numerical examples by employing the proposed numerical simulation method, together with the experimental results obtained by using the active vibration control system, have demonstrated the validity and efficiency of OKID method in application of active vibration control of piezoelectric smart structures.

Topology optimization of piezoelectric sensors/actuators for torsional vibration control ofcomposite plates

Torsional vibration control can be crucial for applications of smart materials andstructures. In this paper, the problem of topology optimization of collocated piezoelectricsensor/actuator (S/A) pairs for torsional vibration control of a laminated composite plateis directly addressed. Both isotropic and anisotropic PZT S/A pairs are considered and it ishighlighted that the torsional vibration can be more effectively damped out by employingthe topological optimal design of the S/A pairs than by using the conventional designs. Toimplement this topology optimization, a genetic algorithm (GA) based on a bit-arrayrepresentation method is presented and a finite element (FE) simulation model based onthe first-order shear theory and an output feedback control law is adopted. Numericalexperiments are used to verify the present algorithm and show that the presentoptimal topology design can achieve significantly better active damping effectthan the one using a continuously distributed PZT S/A pair, which was oftenadopted by many other researchers. Together with the progress in laser cutting andmicromachining techniques, topology optimization of piezoelectric sensors and/oractuators would be promising in active vibration control of smart structures.

Finite element-based overall design of controlled smart structures

The paper presents possibilities of the overall design and control of smart structures based on the finite element method as a successful tool for their simulation and design. The application of distributed sensors and actuators attached to the structure surface or laminated into a composite structure results in a highly integrated smart structural system. An optimal exploitation of such facilities of piezoelectric materials requires effective and robust numerical tools for an optimal overall design. In this paper the finite element approximation, based on multi-field thin-shell elements is presented as a method which in our opinion provides an excellent approach to simulation and design of complex smart structures. As an important issue in the design process the distribution of the active material at the passive base structure is considered. A design concept based on the controllability and observability indices is presented, which results in an acceptable first design even in complex industrial applications. The paper is focused on active vibration and noise control of lightweight structures, which have to fulfil specific design criteria during operation, even if undesired disturbances are exciting the structure. Different application examples illustrate the capability of the smart structures simulation and design. Copyright © 2005 John Wiley & Sons, Ltd.

Integrated Optimization of Actuator Array and Adaptive Control for Smart Structures

Integrated Optimization of Actuator Array and Adaptive Control for Smart Structures

Vibration Control of Composite Smart Structures by Feedforward Adaptive Filter in Digital Signal Processor

Intelligent structures with built-in piezoelectric sensors and actuators have been found to be preferable in vibration control. However, it is difficult to model the uncertainties of interfaces between the composite lamina and the embedded sensor/actuator. This article presents an adaptive filter design for system dynamics identification of composite laminated smart structures. A feedforward adaptive controller based on an adaptive filter with dynamic convergence is also developed for vibration suppression. Both the adaptive filter for system identification and the adaptive controller for vibration suppression are implemented in TMS320C32 digital signal processor for real-time applications. Experimental verifications show that the adaptive control is superior to active damping control and it is effective and robust to vibration suppression of smart structures.

펄스폭변조를 이용한 지능구조물의 능동진동제어

This paper is concerned with the active vibration control of smart structure using actuator signal made of pulse width modulation. The pulse width modulation has been used in motor control, where the amount of energy fed into the motor is controlled by the pulse width instead of applied voltage. The advantage of using the pulse width modulation is that analog signal can be replaced by the digital signal so that we can reduce system costs and power consumption. The effect of pulse width modulation on the vibration response was investigated in this study and the valid transformation rule was found. Then, the pulse width modulation was realized using a microprocessor and electronic circuit. The active vibration suppression was carried out by combining the positive position feedback controller and the pulse width modulation. The experimental result shows that we can replace an expensive amplifier with a pulse width modulation system thus reducing the system cost. The result also shows that the active vibration control can be achieved by the pulse width modulation technique.

An incremental algorithm for static shape control of smart structures with nonlinear piezoelectric actuators

Optimum control voltage design for static shape control of structures with nonlinear piezoelectric actuators is studied in this paper. In order to perform static shape control, the finite element equations of plates with nonlinear piezoelectric actuator patches is formulated using an eight-node adhesive element which combines a pair of collocated four-node quadrilateral elements for the upper and lower plates and a pseudo-adhesive layer element. An iteratively calibrated incremental method is presented to find the optimal control voltages that can actuate a shape best matching the desired shape. In this method, the desired shape is expressed by the sum of a number of small incremental desired shapes, and the control voltages to achieve each incremental desired shape are calculated step by step. The control voltages in each step are then calibrated by using the accumulated intermediate desired shape iteratively. Finally, a simulation example is given to illustrate that the present algorithm is effective in finding the optimal control voltage distribution for shape control of nonlinearly actuated structures. The results show that the present method can give satisfactory control voltages with a reasonable number of incremental steps.

Active Vibration Control and Fault Detection of Smart Structures(International Workshop on Smart Materials and Structural Systems, W03 Jointly organized by Material & Processing Division, Material & Mechanics Division, Dynamics & Control Division and Space Engineering Division.)

Experimental researches on active control of smart structures with piezoelectric actuators have been conducted in the laboratory. The major objective of the researches is to develop a robust and reliable control system for smart structures considering system uncertainties such as structural parameter errors and system failures. Two topics are introduced in this paper. One is the study on a discrete-state sliding mode control (SMC) for vibration control of smart structures. The discrete-state subspace system identification (4SID) is used in combination with the discretestate SMC design, and a software module for seamless transformation from discrete system to continuous system has been developed. The proposed discrete-state sliding mode control has been applied to the flexible cantilever beam equipped with a piezoelectric actuator. It is shown both by numerical simulations and by hardware experiments that the discrete-state SMC has high performance of vibration suppression and robustness against system uncertainties. The second topic is a new method for the fault detection and health monitoring of smart structures. The Eigensystem Realization Algorithm (ERA), a time-domain system identification algorithm, is applied to detect system failures by monitoring the estimated eigenvalues of the system matrix. The ERA is a powerful tool for detecting the small variation in the stifftiess parameter that indicates a structural damage.

Experimental evaluation of augmented UD identification based vibration control of smart structures

Experimental evaluation of augmented UD identification based vibration control of smart structures