Optimal vibration control of smart fiber reinforced composite shell structures using improved genetic algorithm

In the present article, an improved genetic algorithm (GA) based optimal vibration control of smart fiber reinforced polymer (FRP) composite shell structures has been presented. Layered shell finite elements have been formulated and the formulation has been validated for coupled electromechanical analysis of curved smart FRP composite structures having piezoelectric sensors and actuators patches. An integer-coded GA-based open-loop procedure has been used for optimal placement of actuators for maximizing controllability index and a real-coded GA-based linear quadratic regulator (LQR) control scheme has been implemented for optimal control of the smart shell structures in order to maximize the closed-loop damping ratio while keeping actuators voltages within the limit of breakdown voltage. Results obtained from the present work show that this combined GA-based optimal actuators placement and GA-based LQR control scheme is far superior to conventional active vibration control using LQR schemes and simple placement of actuators reported in literatures. Results also show that the present improved GA-based combined optimal placement and LQR control scheme not only leads to increased closed-loop damping ratio but also shows a drastic reduction in input/actuation voltage compared to the already published results.     

粒子群优化模糊控制在汽车空调温控系统应用

针对汽车空调这样一个复杂的热力系统,因其受到车内新风带入热量、太阳辐射、人体散热、车身渗透热等多方面热源的影响产生热负荷,所以利用各种传感器检测车内外温度以及制冷循环部门的温度等参数。本文运用模糊PID进行理论分析与仿真实验,以此为基础加入PSO算法来优化控制器的参数。通过Matlab仿真,说明了基于粒子群优化模糊PID控制的汽车空调温控系统具备较高的控制精度,这种高精度、高稳定性的控制效果为乘客提供了一个舒适的环境,具有一定的实用价值。     

Resonant vibration control of rotating beams

Rotating structures, like e.g. wind turbine blades, may be prone to vibrations associated with particular modes of vibration. It is demonstrated, how this type of vibrations can be reduced by using a collocated sensor-actuator system, governed by a resonant controller. The theory is here demonstrated by an active strut, connecting two cross-sections of a rotating beam. The structure is modeled by beam elements in a rotating frame of reference following the beam. The geometric stiffness is derived in a compact form from an initial stress formulation in terms of section forces and moments. The stiffness, and thereby the natural frequencies, of the beam depend on the rotation speed and the controller is tuned to current rotation speed to match the resonance frequency of the selected mode. It is demonstrated that resonant control leads to introduction of the intended level of damping in the selected mode and, with good modal connectivity, only very limited modal spill-over is generated. The controller acts by resonance and therefore has only a moderate energy consumption, and successfully reduces modal vibrations at the resonance frequency.     

Active control of friction-induced self-excited vibration using adaptive fuzzy systems

Vibration caused by friction is harmful to engineering systems. Understanding the mechanism of such a physical phenomenon and developing some strategies to effectively control the vibration have both theoretical and practical significance. Based on our previous work, this paper deals with a problem of active compensation control of friction-induced self-excited vibration using adaptive fuzzy systems. Comparative studies on control performance are carried out, where a class of adaptive compensation control schemes with various friction models are applied to control a motion dynamics with friction. It is observed that our proposed modeling and control techniques are powerful to eliminate the limit cycle and the steady-state error. Furthermore, robustness of the proposed controller with respect to external disturbances is discussed. Simulation results show that the active controller with adaptive fuzzy friction compensation outperforms other active controllers with compensation terms characterized by three well-known friction models.     

Free vibration of FGM Timoshenko beams with through-width delamination

Free vibration of functionally graded beams with a through-width delamination is investigated.It is assumed that the material property is varied in the thickness direction as power law functions and a single through-width delamination is located parallel to the beam axis.The beam is subdivided into three regions and four elements.Governing equations of the beam segments are derived based on the Timoshenko beam theory and the assumption of‘constrained mode’.By using the differential quadrature element method to solve the eigenvalue problem of ordinary differential equations governing the free vibration,numerical results for the natural frequencies of the beam are obtained.Natural frequencies of delaminated FGM beam with clamped ends are presented.Effects of parameters of the material gradients,the size and location of delamination on the natural frequency are examined in detail.     

Free vibration of composite membranes with arbitrary shape

This paper is concerned with a method for solving problems of a composite membrane with an arbitrarily shaped outer boundary and an arbitrarily shaped inner boundary. The boundary conditions and the conditions of continuity are satisfied directly by using a Fourier expansion collocation method which has been given by Nagaya. The general equation for finding the natural frequencies of the composite membranes has been presented. As examples, numerical calculations have been carried out for composite polygonal membranes, composite elliptical membranes and composite circular membranes with eccentric circular boundaries.     

Free vibration analysis of planar curved beams by wave propagation

In this paper, a systematic approach for the free vibration analysis of a planar circular curved beam system is presented. The system considered includes multiple point discontinuities such as elastic supports, attached masses, and curvature changes. Neglecting transverse shear and rotary inertia, harmonic wave solutions are found for both extensional and inextensional curved beam models. Dispersion equations are obtained and cut-off frequencies are determined. Wave reflection and transmission matrices are formulated, accounting for general support conditions. These matrices are combined, with the aid of field transfer matrices, to provide a concise and efficient method for the free vibration problem of multi-span planar circular curved beams with general boundary conditions and supports. The solutions are exact since the effects of attenuating wave components are included in the formulation. Several examples are presented and compared with other methods.     

Free vibration analysis of linear particle chain impact damper

Impact dampers have gained much research interest over the past decades that resulted in several analytical and experimental studies being conducted in that area. The main emphasis of such research was on developing and enhancing these popular passive control devices with an objective of decreasing the three parameters of contact forces, accelerations, and noise levels. To that end, the authors of this paper have developed a novel impact damper, called the Linear Particle Chain (LPC) impact damper, which mainly consists of a linear chain of spherical balls of varying sizes. The LPC impact damper was designed utilizing the kinetic energy of the primary system through placing, in the chain arrangement, a small-sized ball between each two large-sized balls. The concept of the LPC impact damper revolves around causing the small-sized ball to collide multiple times with the larger ones upon exciting the primary system. This action is believed to lead to the dissipation of part of the kinetic energy at each collision with the large balls.     

Adaptive fuzzy sliding mode control of smart structures

Smart structures are usually designed with a stimulus-response mechanism to mimic the autoregulatory process of living systems. In this work, in order to simulate this natural and self-adjustable behavior, an adaptive fuzzy sliding mode controller is applied to a shape memory two-bar truss. This structural system exhibits both constitutive and geometrical nonlinearities presenting the snap-through behavior and chaotic dynamics. On this basis, a variable structure controller is employed for vibration suppression in the chaotic smart truss. The control scheme is primarily based on sliding mode methodology and enhanced by an adaptive fuzzy inference system to cope with modeling inaccuracies and external disturbances. The robustness of this approach against both structured and unstructured uncertainties enables the adoption of simple constitutive models for control purposes. The overall control system performance is evaluated by means of numerical simulations, promoting vibration reduction and avoiding snap-through behavior.     

基于粒子群算法和OGY方法的混沌系统混合控制

利用引导混沌轨道的基本原理,将模拟鸟群寻食过程的粒子群算法用于混沌控制,提出了基于粒子群算法引导混沌轨道的新方法,在此基础上利用混沌参数小扰动控制方法（OGY方法）,把混沌系统稳定到不动点.以Hnon混沌系统为例,仿真表明此方法实现混沌控制有良好效果. 关键词： 混沌控制 粒子群算法 OGY控制 引导轨道     

Experimental evaluation of a piezoelectric vibration absorber using a simplified fuzzy controller in a cantilever beam

This study presents a novel resonant fuzzy logic controller (FLC) to minimize structural vibration using collocated piezoelectric actuator/sensor pairs. The proposed fuzzy controller increases the damping of the structures to minimize certain resonant responses. The vibration absorber is first experimentally examined by a cantilever beam test bed for impulse and near-resonant excitation cases. Moreover, the effectiveness of the new fuzzy control design to a state-of-the-art control scheme is compared through the experimental studies. The experimental results indicate the proposed controller is highly promising for this application field. Our results further demonstrate that the fuzzy approach is much better than traditional control methods. In summary, a novel vibration absorption scheme using fuzzy logic has been demonstrated to significantly enhance the performance of a flexible structure with resonant response.     

Vibration control of a structure with ATMD against earthquake using fuzzy logic controllers

In this paper, fuzzy logic and PD controllers are designed for a multi-degree-of freedom structure with active tuned mass damper (ATMD) to suppress earthquake-induced vibrations. Fuzzy logic controller (FLC) is preferred because of its robust character, superior performance and heuristic knowledge use effectively and easily in active control. A fifteen-degree-of-freedom structural system is modeled with two types of actuators. These actuators are installed on the first storey and fifteenth storey which has ATMD. The system is then subjected to Kocaeli Earthquake vibrations, which are treated as disturbances. In control, linear motors are used as the active isolators. At the end of the study, the time history of the storey displacements and accelerations, ATMD displacements, control voltages, frequency responses of the both uncontrolled and the controlled structures are presented. Performance of the designed FLC has been shown for the different loads and disturbances using ground motion of the Kobe Earthquake. The results of the simulations show a good performance by the fuzzy logic controllers for different loads and the earthquakes.     

Design and implementation of fuzzy logic based automatic gain controller for EDFAs

In this study, the design and implementation of a fuzzy logic (FL) based automatic gain controller card (AGC) is performed in order to control the pump laser current with respect to signal power and signal wavelength. The FL-AGC card consists of an amplifier, an analogue to digital converter (ADC), a digital to analogue converter (DAC), and a FL based software that is embedded to a microcontroller. With this configuration, gain flattening at the output of the erbium doped fibre amplifier (EDFA) along C band is achieved. In this way, ergonomically designed FL-AGC card can be easily matched with EDFAs and can be applicable to optical system applications.     

基于混沌粒子群优化算法的异结构混沌反同步自抗扰控制

针对一类连续时间异结构混沌系统, 利用自抗扰控制很强的鲁棒性, 提出了一种异结构混沌系统反同步的自抗扰控制策略.针对所设计的自抗扰控制器参数较多, 难以整定的问题, 提出了应用混沌粒子群优化算法对控制器进行参数寻优设计. 以Lorenz系统和Chua系统两个异结构混沌系统为例进行仿真验证, 由仿真结果可知, 该方法可以实现异结构混沌系统较快的反同步控制, 且具有很强的抗干扰能力. 关键词： 异结构混沌系统反同步 自抗扰控制器 混沌粒子群优化算法 参数寻优     

Free vibration analysis of moderately thick asymmetric piezoelectric adaptive cantilever beams using the distributed transfer function approach

A semi-analytical distributed transfer function (DTF) approach is proposed for the free-vibration analysis of moderately thick cantilever beams with a single surface-bonded piezoelectric patch. The asymmetric piezoelectric adaptive structure is decomposed into three segments; the first and third segments are bare beam parts before and after the patch, while the second segment contains the beam part with attached piezoelectric patch bonded to its upper surface. The theoretical formulation assumes first-order shear deformation kinematics and linear electric potential through the patch thickness with an electrode equipotential physical condition, and uses the extended Hamilton?s principle to derive the equations of motion and electromechanical boundary conditions. The latter, together with the continuity and equilibrium conditions at the segments interfaces, are then transformed into a first-order state space equation that is solved using the DTF approach. The electrodes of the piezoelectric patch are considered either in short-circuit (SC) or open-circuit (OC); this leads to two free-vibration problems to be solved for the corresponding SC and OC frequencies, from which the Electro-Mechanical Coupling Coefficient (EMCC) is post-treated. Four benchmarks from the open literature are simulated in order to validate the proposed approach. Very satisfactory correlations are obtained for all examples with maximum errors less thank 5 percent in all results. For future reference, an additional benchmark is proposed to assess the influence of the patch-to-composite host width ratio on the effective modal EMCC. It was found that the latter is mode-dependent (as expected) and decreases with increasing the former.     

Chattering alleviation in vibration control of smart beam structures using piezofilm actuators: Experimental verification

This paper presents a new discrete-time sliding mode controller to alleviate undesirable chattering in vibration control of a flexible beam structure. A smart beam featuring a piezoelectric film is devised and its governing equation of motion is derived. A discrete-time sliding mode controller which consists of discontinuous part and equivalent part is then designed by considering the separation principle. By doing this, undesirable chattering of the beam structure can be attenuated in the settled phase. The proposed controller is experimentally realized, and both transient and forced vibration control responses are evaluated in time domain.     

Free vibration of curved sandwich beams by the method of finite elements

The finite element displacement method is used to investigate the flexural vibration characteristics of curved sandwich beams. Three displacement models are used incorporating an element having three, four and five degrees of freedom per node and various parametric studies are made to investigate their effect on the natural frequencies of curved clamped-clamped sandwich beams.     

Hybrid fuzzy logic control of laser surface heat treatments

This paper presents an advanced hybrid fuzzy logic control system for laser surface heat treatments, which allows to increase significantly the uniformity and final quality of the obtained product, reducing the rejection rate and increasing the productivity and efficiency of the treatment. Basically, the proposed hybrid control structure combines a fuzzy logic controller, with a pure integral action, both fully decoupled, improving the performances of the process with a reasonable design cost, since the system nonlinearities are fully compensated by the fuzzy component of the controller, while the integral action contributes to eliminate the steady-state error.     

Free vibration analysis of corner-supported rectangular plates with symmetrically distributed edge beams

Analytical type solutions are obtained for the free vibration frequencies and mode shapes of thin corner-supported rectangular plates with symmetrically distributed reinforcing beams, or strips, attached to the plate edges. The method of superposition is employed. Equations governing reactions at plate-beam interfaces are developed in dimensionless form. The approach is comprehensive in that both lateral and rotational stiffness, and inertia, of the beam are incorporated into the analysis. For illustrative purposes computed eigenvalues and mode shapes are presented for two plate-beam systems of realistic geometries. It is shown that the method is easily extended to cover the case where the edge beams do not have a symmetrical distribution. This appears to be the first comprehensive analytical study of this problem of industrial interest.     

Free vibration of thin walled open section beams with constrained damping treatment

Free vibration characteristics of a thin walled, open cross-section beam, with constrained damping layers at the flanges, are investigated. Both uncoupled transverse vibration and the coupled bending-torsion oscillations, of a beam of a top-hat section, are considered. Numerical results are presented for natural frequencies and modal loss factors in the first two modes of simply supported and clamped-clamped beams. For the uncoupled mode the constrained damping treatment is more effective than an unconstrained one, but for the coupled mode the effect is just the opposite.