Flexible Plate Structure Research Articles

Experimental study of the flow field induced by a resonating piezoelectric flapping wing

Flexible plate structures with integrated piezoelectric patches offer interesting possibilities when considered as actuation mechanisms for energy harvesting devices, cooling devices and propulsion devices of micro-aerial vehicles. Most of the studies reported in literature are based on the assumption of a 2D aerodynamic flow. However, the flow behind a finite span wing is significantly more complex than that of an infinite span wing. In order to corroborate this statement, the present experimental study contains high-speed particle image velocimetry measurements performed on a piezoelectric finite span wing oscillating in air, at 84.8 Hz. The paper focuses on the situation of low Keulegan–Carpenter numbers (KC < 3). The dimensionless KC number describes the relative importance of the drag forces over inertia forces for objects that oscillate in a fluid flow at rest. The evolution of the unsteady vortex structures near the plate is characterized for different conditions. This allows a better understanding of the unsteady aerodynamics of flapping flight. The accomplished experimental data analysis has shown that the flow phenomena are strongly dependent on the KC values.

Robust Nominal Model-Based Sliding Mode Robust Control for Vibration of Flexible Rectangular Plate

In this paper, we developed an approach for active vibration control of flexible rectangular plate structures using control theory. The flexible rectangular plate system is firstly modelled and simulated via a finite element method; and secondly, a new type of modelling method, and the state-space model are involved in the development of the equation of motion in state-space, which is efficiently used for the analysis of the system and design of control laws with a modern control framework. Then, the validity of the obtained new model is investigated by comparing the plate natural frequencies and forced vibration response analysis predicted by the finite element model with the calculated values obtained from new model. After validating the model, nominal model-based sliding mode robust MIMO controller is applied to the plate dynamics via the MATLAB/Simulink platform. The simulation results clearly demonstrate an effective vibration suppression capability that can be achieved using nominal model-based sliding mode robust MIMO controller.

Intelligence Swarm Model Optimization of Flexible Plate Structure System

This paper presents the performance of modeling the flexible plate structure with free-free-clamped-clamped (FFCC) edges boundary condition using conventional Recursive Least Squares (RLS) and evolutionary algorithm of Genetic Algorithm (GA) and Particle Swarm Optimization (PSO). The auto-regressive with exogenous (ARX) structure was used in this study to obtain the dynamic model of a flexible plate structure. Data acquisition and instrumentation system were designed and integrated with the experimental rig and several experimental procedures were conducted to acquire the input and output of the flexible plate. The input and output data collected from the experimental study were utilized to develop the model of the system. The 4000 data sets collected in the experiment were divided into two parts for training and testing. The first 3000 data sets were used to train the model developed while the last 1000 data sets were used to test the performance of thus developed model. All developed model using RLS, GA and PSO were validated using one step-ahead prediction (OSA), mean squared error (MSE) and correlation tests. Amongst all, it was found that PSO algorithm has performed better in term of lowest mean squared error achieved (0.00032719) as compared to conventional algorithm (RLS) and evolutionary algorithm (GA). However, by comparing in term of estimating the first mode of vibration which the dominant mode of structure, GA has performed better by presented the lowest percentage error (3.63 %). Besides that, it was found that, all estimated models using all methods proposed are comparable, acceptable and possible to be used as a platform of controller development and verification to suppress the vibration of the flexible plate structure.

Fuzzy control for geometrically nonlinear vibration of piezoelectric flexible plates

This paper presents a LMI(linear matrix inequality)-based fuzzy approach of modeling and active vibration control of geometrically nonlinear flexible plates with piezoelectric materials as actuators and sensors. The large-amplitude vibration characteristics and dynamic partial differential equation of a piezoelectric flexible rectangular thin plate structure are obtained by using generalized Fourier series and numerical integral. Takagi-Sugeno (T-S) fuzzy model is employed to approximate the nonlinear structural system, which combines the fuzzy inference rule with the local linear state space model. A robust fuzzy dynamic output feedback control law based on the T-S fuzzy model is designed by the parallel distributed compensation (PDC) technique, and stability analysis and disturbance rejection problems are guaranteed by LMI method. The simulation result shows that the fuzzy dynamic output feedback controller based on a two-rule T-S fuzzy model performs well, and the vibration of plate structure with geometrical nonlinearity is suppressed, which is less complex in computation and can be practically implemented.

Active Vibration Control of Flexible Plate Structures with Distributed Disturbances

This paper presents the development of an active vibration control (AVC) system with distributed disturbances using genetic algorithms, particle swarm optimization, and ant colony optimization. The approaches are realized with multiple-input multiple-output and multiple-input single-output control configurations in a flexible plate structure. A simulation environment characterizing a thin, square plate, with all edges clamped, is developed using the finite difference method as a platform for test and verification of the developed control approaches. Simulations are carried out with random disturbance signal. The control design comprises a direct minimization of the error (observed) signal by allowing a collective determination of detection and secondary source locations together with controller parameters. The algorithms are formulated with a fitness function based on the mean square of the observed vibration level. In this manner, knowledge of the input/output characterization of the system is not required for design of the controller. The performance of the system is assessed and analyzed both in the time and frequency domains and it is demonstrated that significant vibration reduction is achieved with the proposed schemes.

ADAPTIVE ITERATIVE LEARNING CONTROL FOR VIBRATION OF FLEXURAL RECTANGULAR PLATE

In this paper, we developed an approach for active vibration control of flexible rectangular plate structures using control theory. The flexible rectangular plate system is firstly modeled and simulated via a finite element method; and secondly, a new type of modeling method, and the state-space model are involved in the development of the equation of motion in state-space, which is efficiently used for the analysis of the system and design of control laws with a modern control framework. Then, the validity of the obtained new model is investigated by comparing the plate natural frequencies, mode shapes, statical analysis and forced vibration response analysis predicted by the finite element model with the calculated values obtained from new model. After validating the model, adaptive iterative learning MIMO controller is applied to the plate dynamics via the MATLAB/Simulink platform. The simulation results clearly demonstrate an effective vibration suppression capability that can be achieved using adaptive iterative learning MIMO controller.http://dx.doi.org/10.5755/j01.mech.17.5.724

Non-parametric modelling of a rectangular flexible plate structure

This research investigates the performance of dynamic modelling using non-parametric techniques for identification of a flexible structure system for development of active vibration control. In this paper, the implementation details are described and the experimental studies conducted in this research are analysed. The input–output data of the system were first acquired through the experimental studies using National Instruments (NI) data acquisition system. A sinusoidal force was applied to excite the flexible plate and the dynamic response of the system was then investigated. Non-parametric modelling of the system were developed using several artificial intelligent methodologies namely Adaptive Elman Neural Networks (ENN), Backpropagation Multi-layer Perceptron Neural Networks (MLPNN) and Adaptive Neuro-Fuzzy Inference System (ANFIS). The performance of all these methodologies were compared and discussed. Finally, validation and verification of the obtained model was conducted using One Step Ahead (OSA) prediction, mean squared error (MSE) and correlation tests. The prediction ability of the model was further observed with unseen data. The results verified that the MLPNN converge to an optimum solution faster and the dynamic model obtained described the flexible plate structure very well. The non-parametric models of the flexible plate structure thus developed and validated will be used as the representation of the transfer function of the system in subsequent investigations for the development of active vibration control strategies for vibration suppression in flexible structures.

Vibration Suppression of Flexible Plate Structures Using Swarm and Genetic Optimization Techniques

This paper presents the development of an active vibration control mechanism using genetic algorithm and particle swarm optimization. The approaches are realized with single-input single-output and single-input multiple-output control configurations in a flexible plate structure with all edges clamped. Simulations are carried out with different disturbance signal types, namely random, pseudo random binary sequence, and finite-duration step. The control design comprises a direct minimization of the error (observed) signal by searching the optimal locations of the detector and secondary source, along with the controller parameters. The algorithms are formulated with an objective function based on mean square of the observed vibration. In this manner, knowledge of the input/output characterization of the system is not required for design of the controller. The performance of the system is assessed and analyzed both in the time and frequency domains and it is demonstrated that the proposed scheme reduces vibration of the flexible plate significantly.

ANFIS Modelling of Flexible Plate Structure

This paper presented an investigation into the performance of system identification using an Adaptive Neuro-Fuzzy Inference System (ANFIS) technique for the dynamic modelling of a two-dimensional flexible plate structure. It is confirmed experimentally, using National Instrumentation (NI) Data Acquisition System (DAQ) and flexible plate test rig that ANFIS can be effectively used for modelling the system with highly accurate results. The accuracy of the modelling results is demonstrated through validation tests including training and test validation and correlation tests.

Self-learning active vibration control of a flexible plate structure with piezoelectric actuator

In this paper, an active vibration control (AVC) incorporating active piezoelectric actuator and self-learning control for a flexible plate structure is presented. The flexible plate system is first modelled and simulated via a finite difference (FD) method. Then, the validity of the obtained model is investigated by comparing the plate natural frequencies predicted by the model with the reported values obtained from literature. After validating the model, a proportional or P-type iterative learning (IL) algorithm combined with a feedback controller is applied to the plate dynamics via the FD simulation platform. The algorithms were then coded in MATLAB to evaluate the performance of the control system. An optimized value of the learning parameter and an appropriate stopping criterion for the IL algorithm were also proposed. Different types of disturbances were employed to excite the plate system at different excitation points and the controller ability to attenuate the vibration of observation point was investigated. The simulation results clearly demonstrate an effective vibration suppression capability that can be achieved using piezoelectric actuator with the incorporated self-learning feedback controller.

Active Vibration Control of a Flexible Plate Using Real Coded Genetic Algorithm

AbstractIn this paper, a flexible plate structure is utilised as a platform to assess the performance of an active vibration control (AVC) mechanism developed in this work based on a real coded genetic algorithm. The system employs a single input and single output (SISO) control configuration, and this is realised within the Matlab/Simulink environment. A model-based control design approach, incorporating identification of the system model based on genetic algorithm is carried out to design the controller. The investigations concentrate on the first five resonance modes of the structure, and assess the ability of developed control approach in attenuating the deflection of the plate structure. The performance of the AVC system is presented in both time and frequency domains under a pseudo random binary sequence (PRBS). Simulation results reveal that good performance is achieved in this approach.

Parametric and Non-Parametric Identification of a Two Dimensional Flexible Structure

An investigation into the parametric and non-parametric modelling of a two dimensional flexible plate structure is presented in this paper. The parametric approaches obtaining linear parametric models of the system using recursive least squares and genetic algorithms. The non-parametric models of the system are developed using a non-linear AutoRegressive process with eXogeneous input model with multi-layered perceptron neural networks, Elman recurrent neural networks and adaptive neuro-fuzzy inference systems. The models are validated using several validation tests including input-output mapping, mean squares of error and correlation tests. A comparative assessment of the techniques used is presented and discussed in terms of accuracy, efficiency and performance in estimating the modes of vibration of the system.

Actuator Placement Optimization and Adaptive Vibration Control of Plate Smart Structures

In this paper, a performance criterion is proposed for the optimization of piezoelectric patch actuator locations on flexible plate structures based on maximizing the controllability grammian. This is followed by the determination of parameters required for actuator location optimization through Structuring Analysis in ANSYS Finite Element Analysis Package. Genetic Algorithm is then used to implement the optimization. Finally, with the actuators bonded on optimized locations, a filtered-x LMS-based multichannel adaptive control is applied to suppress vibration response of the plate. Numerical simulations are performed in suppressing tri-sinusoidal response at three points of the plates. The results show that the developed actuator placement optimization methodology is very effective in searching for the optimal actuator locations that minimize the energy requirement of vibration control. The control algorithm is also demonstrated to be efficient and robust in the smart structure vibration control.

Active Stiffener Actuators for High-Precision Shape Control of Circular Plate Structure

Spaced-based adaptive optic systems have gained considerable attention within the past couple of decades. Achieving the increasingly stringent performance requirements for these systems is greatly hindered by strict weight restrictions, size limitations, and subjected hostile environments. There has been considerable attention in lightweight adaptive optics, where piezoelectric sheet actuators are directly attached on the back of optical mirrors to achieve a high-precision surface shape with minimum additional weight. In recent studies, it was discovered that the performance of the system could be further improved if the piezoelectric sheet actuator were decoupled in direction, meaning that the actuation in one of the two directions is eliminated. To realize the decoupling effect, the concept of utilizing the active stiffener for high-precision shape control is proposed and investigated in the study. The active stiffener is a stiffener-piezoceramic actuator pair that consists of an passive insert (stiffener) placed between the host structure and the active piezoelectric actuator. The basic premise is that the insert (stiffener) will reduce the action transmitted in one direction while allowing adequate action to transmit in the orthogonal direction. In this research, analytical and experimental efforts are carried out to examine the effect of the active stiffener actuators for shape control of circular plate structures. Analysis is performed on two large flexible circular plate structures, one having the direct attached actuators and the other utilizing the active stiffener actuators. It is shown that more reductions in the surface error can be achieved with the active stiffeners, as compared to systems with the direct attached actuators. It is illustrated that the direct attached actuators generate more localized deformation in the structure, whereas the decoupling capability of the active stiffener reduces the undesired localized deformation considerably. The experimental results verify the analytical predictions and clearly demonstrate the performance improvement of the active stiffener concept over the direct attached actuator.

Soft computing-based active vibration control of a flexible structure

Control of vibration of flexible structures has been of remarkable research attention in the last decade. Conventional control methods have not been widely successful due to the dynamic complexity of flexible structures. The literature has recently seen an emergence of demand of soft computing techniques in modelling and control of such dynamic systems. However, the form of soft computing required depends on the nature of the application. This paper accordingly presents investigations into modelling and control techniques based on soft computing methods for vibration suppression of two-dimensional flexible plate structures. The design and analysis of an active vibration control (AVC) system utilising soft computing techniques including neural networks and fuzzy logic is presented. The investigation involves soft computing approach with single-input single-output (SISO) and single-input multi-output (SIMO) AVC structures. A comprehensive comparative assessment of the approaches in terms of performance and design efficiency is also provided. Investigations reveal that the developed soft computing-based AVC system performs very well in the suppression of vibration of a flexible plate structure. It is also shown that the developed SIMO AVC system performs much better in the suppression of vibration of a flexible plate structure in comparison to the SISO AVC system.

Parametric Modeling of a Flexible 2D Structure

This paper investigates the utilization of genetic algorithms (GAs) for dynamic modeling of a highly non-linear system. The global search technique of GA is used to identify the parameters of a flexible square plate structure based on one-step-ahead prediction. The results obtained, in both time and frequency domains, are compared with those obtained using the recursive least squares (RLS) technique. Simulations indicate the superiority of a GA technique over RLS algorithm in modeling a flexible square plate structure.

Finite Difference Simulation of a Flexible Plate Structure

In this paper, an investigation into the dynamic characterisation of a two dimensional (2D) flexible structure is presented. A thin, flat plate, with all edges clamped, is considered. A simulation algorithm characterising the dynamic behaviour of the plate is developed through a discretisation of the governing partial differential equation formulation of the plate dynamics using finite difference methods. The algorithm is implemented within the Matlab environment, and it allows application and sensing of a disturbance signal at any mesh point on the plate. Such a provision is desirable for the design and development of active vibration control techniques for the system. The performance of the developed algorithm in characterising the dynamic behaviour of the system is assessed in comparison with previously reported results using various other methods. The validation of the algorithm is presented in both the time and frequency domains. Investigations reveal that the measured parameters associated with the first five resonance modes of the system compare favourably with previously reported results. The simulation algorithm thus developed and validated forms a suitable test and verification platform in subsequent investigations for development of active vibration control strategies for flexible plate structures.

Bending and torsional vibration control of a flexible plate structure using H/sub ∞/-based robust control law

This paper presents a method of controlling the bending and torsional vibration modes of a flexible plate structure (theoretically which has infinite number of vibration modes) using H/sub /spl infin//-based robust control. For this purpose, a three degree of freedom (DOF) reduced order lumped mass model of a plate structure is derived by considering first three vibration modes and neglecting the all other high-frequency modes. These neglected modes constitute the unstructured uncertainties of the system and taken care of in the time of design process. An idea is proposed to reduce the unmodeled system uncertainties by placing actuators in the node points of a neglected mode. As a result, it is possible to avoid the spillover instability (avoid the influence of a neglected mode) without affecting the control of lower order modes. Then a static state feedback controller is designed based on the reduced order model and the approximate knowledge of unmodeled uncertainties. The efficacy of feedback controller is shown through simulation and experimental studies.

Dynamic Peripheral Milling of Flexible Structures

A dynamic model for peripheral milling of very flexible plate type structures has been presented. The structural dynamics of a cantilevered plate structure is modelled at the tool-workpiece contact zone. The interaction of the very flexible plate structure and rigid end mill during dynamic milling is modelled. The variation in surface, chip thickness, and structural dynamics of the plate are considered in determining the milling forces. The proposed model provides surface finish form errors displacements at the tool-workpiece contact zone, and cutting forces for dynamic end milling operations.

Application of cross-spectral density to a measurement of vibration power flow between connected plates

It is shown that the flow of vibration power through a rigid ’’point’’ connection between flexible plate structures may be evaluated by measuring the imaginary part of the cross-spectral density between the coupling force and the acceleration at the connection point.