Vibration Control Technique Research Articles

Active Vibration Control in Smart Structures

When a system is subjected to dynamic loading, it causes vibratory motion. For the better stability of the system, this vibration should be eliminated. But practically vibration can be brought down to some extent, and cannot be eliminated completely. It can be control by appropriate control methods. The passive and active vibration control techniques can be used for control. This can be achieved by modification of the system’s structural response. The objective of the present work is to carry out modeling, analysis and simulation of active vibration control of an Aluminium cantilever beam using piezoelectric sensors and actuators. The mathematical model of the cantilever beam bonded with piezoceramic actuator is formulated as a multilayer piezo composite beam. The finite element modeling and analysis of the beam with sensors and actuators is done using the finite element package ANSYS. The location of the piezo is determined based on maximum deflection of beam obtained in ANSYS coupled field analysis. Modal analysis is performed in ANSYS and the natural frequencies and mode shapes of the beam are found out for the applied voltage. Proportional-integral controller was developed and experiments was carried out by using Labview software

Czochralski growth of NaNO3–LiNO3 solid solution single crystals using axial vibrational control technique

T-x diagram of LiNO3–NaNO3 quasi-binary system has been improved using an original technique based on Raman measurements of condense phase. (LiNO3)x(NaNO3)1−x solid solution single crystal has been grown at different regimes of axial vibrational control (AVC) technique. Significant difference in segregation coefficient behavior between AVC-CZ and conventional CZ grown crystals has appeared: with AVC intensity increase the segregation coefficient (SC) raises for light molecular weight elements, SC reduces for medium molecular weight elements, and SC remains practically unchangeable for heavy molecular weight elements. Effect of vibrational intensity on vibron and optical characteristics, microhardness of AVC-CZ (LiNO3)x(NaNO3)1−x solid solution single crystals has been studied. For the AVC-CZ crystals has been observed increases in microhardness as well as in optical transmission up to 10rel% compare to conventional CZ grown crystals.

Feedforward and Feedback Vibration Control and Algorithm Design for Cable-Bridge Structure Nonlinear Systems

Technique of feedforward and feedback optimal vibration control and simulation for long-span cable-bridge coupled systems is developed. Buffeting loading systems of long-span cable-bridge structure are constructed by weighted amplitude wave superposition method. Nonlinear model of cable-bridge coupled vibration control system is established and the corresponding system of state space form is described. In order to reduce buffeting loading influence of the wind-induced vibration for the structure and improve the robust performance of the vibration control, based on semiactive vibration control devices and optimal control approach, a feedforward and feedback optimal vibration controller is designed, and an algorithm is presented for the vibration controller. Numerical simulation results are presented to illustrate the effectiveness of the proposed technique.

Semi-active vibration suppression for smart structures with sliding-mode control

A semi-active vibration suppression system is developed for flexible structures. The vibration suppression system comprises bimorph piezoelectric ceramic tiles shunted by a resistor–inductor electrical circuit with a switching component. The vibration suppression control is designed by tuning the optimal resistance and inductance parameters of the shunted resistor–inductor network. In this article, we propose a semi-active vibration control technique to improve the damping effect while maintaining the stability of the passive control system. The proposed control law is similar to a sliding-mode control that accelerates the convergence of the system using switching functions. This study shows that the resonant circuit functions as a type of dynamic damper for mechanical systems and that the sliding-mode control is very effective for damping the multi-mode responses. The results of the numerical simulations of a cantilevered beam show that a semi-active vibration control system is more effective in damping vibrations than a passive control system. A hardware demonstration based on a laboratory model has also been carried out. The preliminary results of the experiment show that the system is sensitive to the noise, and improved implementation of the switching circuit is needed for practical application.

Dynamic responses of a 492-m-high tall building with active tuned mass damping system during a typhoon

SUMMARY This paper presents observations on the dynamic properties and wind-induced response characteristics of a 492-m-high building installed with an active tuned mass damping (ATMD) system during a typhoon. Damping ratios, natural frequencies, and wind-induced vibrations of the super-tall building with/without the operation of the ATMD system are investigated. Field measurement results show that the ATMD system functioned efficiently for the suppression of the wind-induced vibrations of this super-tall building, and the building's acceleration responses were well confined within the range stipulated in the International Standards Organization for serviceability concerns. A modified time-weighted random decrement operator is proposed for estimation of damping ratio, which is able to provide more reasonable estimations than unmodified form under nonstationary conditions. In addition, extreme responses of this building under the typhoon are studied using the crossing method and the generalized extreme value model. The main objective of this study is to investigate the effectiveness of the ATMD system and the performance of the actively controlled high-rise structure under typhoon condition to assess the benefits gained from the application of the vibration control technique. Copyright © 2013 John Wiley & Sons, Ltd.

EMBEDDED COMPUTER BASED ACTIVE VIBRATION CONTROL SYSTEM FOR VIBRATION REDUCTION OF FLEXIBLE STRUCTURES

Research on Active Vibration Control System (AVCS) is being carried out to reduce structural vibration s caused by unwanted vibrations in many application a reas such as in space, aircraft structures, satelli tes, automobiles and civil structures (bridges), particu larly at low frequencies. The unwanted vibration ma y cause damage to the structure or degradation to the structure’s performance. The AVCS comprises physical plant, a sensor to detect the source vibration, a D SP based electronic controller using an actuator co nnected to the structure generates a counter force that is appropriately out of phase but equal in amplitude t o the source vibration. As a result two equal and opposit e forces cancel each other by the principle of supe r position and structure stops vibrating. The main ob jective of this research work is to develop an embe dded computer based real time AVCS for reducing low frequency tonal vibration response of a vibrating flexi ble cantilever beam by automatic modification of the vi brating beam’s structural response and to verify th e performance of the developed system experimentally. The developed AVCS is a generic design platform that can be applied for designing adaptive feed for ward AVC and feedback AVC. This study presents the vibration control methodology adapted for reducing tonal vibration generated by a sine generator conne cted to the primary source actuator attached to one end of the cantilever beam. The secondary actuator is attached to the beam on the other end through the A VCS to reduce primary vibration by destructive interference with the original response of the syst em, caused by the primary source of vibration. Adap tive feed forward Active Vibration Control (AVC) technique is used with Filtered-X Least Mean Square (FxLMS) algorithm using FIR digital filter. A canti lever beam was considered as plant and embedded computer based AVCS was tested and evaluated using an experimental setup. The experimental results are presented for the cantilever beam excited at one of its natural frequency using active vibration contr ol system and an appreciable reduction was achieved up to 20 dB.

Modeling of a hybrid semi-active/passive vibration control technique

In this paper a new hybrid vibration damping technique as a combination of the semi-active pulse switching technique and passive constrained layer damping is proposed as an effective vibration control method for all frequency ranges. The semi-active pulse switching technique is an effective method to damp any type of vibrations with no need for external energy sources. However, its performance in high-frequency ranges decreases. In addition, passive techniques are not so effective in low-frequency ranges, but have significant effects in high-frequency ranges. The proposed hybrid damping technique as a combination of these two control methods is a new effective control technique for all frequency ranges. It covers the weakness of the semi-active method and provides significant damping in both low and high-frequency vibrations.

Modeling of axial vibrational control technique for CdTe VGF crystal growth under controlled cadmium partial pressure

A VGF growth setup assisted by axial vibrations of baffle submerged into CdTe melt with controlled Cd partial pressure was designed. An influence of baffle shape on flow velocity map, temperature distribution in CdTe melt and interface shape of growing crystal was analyzed by numerical simulation and physical modeling. To produce the desirable shape of crystal melt interface we slant under different angles vertical generatrix in a cylindrical disk and made chasing on faceplates of a disk. It was ascertained that a disk with conical generatrix formed more intensive convective flows from a faceplate with larger diameter. It was shown that at CdTe VGF crystal growth rate about 10mm/h application of AVC technique made it possible to produce convex interface for 2in. crystal diameter.

On the control of vibrations using synchrophasing

This paper describes the application of a technique, known as synchrophasing, to the control of machinery vibration. It is applicable to machinery installations, in which several synchronous machines, such as those driven by electrical motors, are fitted to an isolated common structure known as a machinery raft. To reduce the vibration transmitted to the host structure to which the machinery raft is attached, the phase of the electrical supply to the motors is adjusted so that the net transmitted force to the host structure is minimised. It is shown that while this is relatively simple for an installation consisting of two machines, it is more complicated for installations in which there are more than two machines, because of the interaction between the forces generated by each machine. The development of a synchrophasing scheme, which has been applied to propeller aircraft, and is known as Propeller Signature Theory (PST) is discussed. It is shown both theoretically and experimentally, that this is an efficient way of controlling the phase of multiple machines. It is also shown that synchrophasing is a worthwhile vibration control technique, which has the potential to suppress vibration transmitted to the host structure by up to 20 dB at certain frequencies. Although the principle of synchronisation has been demonstrated on a one-dimensional structure, it is believed that this captures the key features of the approach. However, it should be realised that the mode-shapes of a machinery raft may be more complex than that of a one-dimensional structure and this may need to be taken into account in a real application.

Semi-Active Pulse-Switching Vibration Suppression Using Sliding Time Window

The performance of pulse-switching vibration control technique is investigated using a new method for switching sequence, in order to enhance the vibration damping. The control law in this method which was developed in the field of piezoelectric damping is based on triggering the inverting switch on each extremum of the produced voltage (or displacement); however, its efficiency in the case of random excitation is arguable because of the local extremum detection process. The new proposed method for switching sequence is only based on the fact that the triggering voltage level was determined using windowed statistical examination of the deflection signal. Results for a cantilever beam excited by different excitation forces, such as stationary and nonstationary random samples, and pulse forces are presented. A significant decrease in vibration energy and also the robustness of this method are demonstrated.

Output frequency response function based design of additional nonlinear viscous dampers for vibration control of multi-degree-of-freedom systems

This paper is concerned with the development of a new technique for the optimal placement and design of additional nonlinear viscous dampers for vibration control of Multi-Degree-Of-Freedom (MDOF) systems. The MDOF systems described by a multi-storey shear building model and subjected to harmonic loadings are first considered in the present study; then, the basic ideas of the design are extended to the cases of earthquake loadings. The studies are based on the concept of Output Frequency Response Function (OFRF) and associated methods proposed recently by the authors in control engineering and extend, for the first time, the well-established linear viscous damper optimal placement and design techniques for MDOF system vibration control to the nonlinear case. The design examples verify the effectiveness of the new technique, and demonstrate the beneficial effects of the designed additional nonlinear dampers on the MDOF system vibration control and the advantages of nonlinear viscous dampers over linear dampers in such applications.

Optimal Vibration Control for Tracked Vehicle Suspension Systems

Technique of optimal vibration control with exponential decay rate and simulation for vehicle active suspension systems is developed. Mechanical model and dynamic system for a class of tracked vehicle suspension vibration control is established and the corresponding system of state space form is described. In order to prolong the working life of suspension system and improve ride comfort, based on the active suspension vibration control devices and using optimal control approach, an optimal vibration controller with exponential decay rate is designed. Numerical simulations are carried out, and the control effects of the ordinary optimal controller and the proposed controller are compared. Numerical simulation results illustrate the effectiveness of the proposed technique.

Independent modal variable structure fuzzy active vibration control of cylindrical thin shells laminated with photostrictive actuators

Photostrictive actuator, which can produce photodeformation strains under the activation of ultraviolet lights, is a new promising non-contact photoactuation technique for active vibration control of flexible structures. Generally, the membrane control action plays a major role in vibration control of flexible thin shell structures. However, it is unfortunate that the existing photostrictive actuator configuration can not induce negative membrane control forces. In this paper, a novel multi-layer actuator configuration is first presented to remedy this deficiency, followed by presenting the photostrictive/shell coupling equations of thin cylindrical shells laminated with the proposed multi-layer actuator configuration. Moreover, considering the time-variant and nonlinear dynamic characteristics of photostrictive actuator, variable structure self-adjusting parameter fuzzy active controller is explored to overcome disadvantages of conventional control schemes, in which off-line fuzzy control table is adopted. The optimal switching surface is derived to increase the range of sliding mode to facilitate vibration suppression. A continuous function is used to replace the sign function for reducing the variable structure control chattering. Finally, two case studies are carried out to evaluate the effectiveness of the proposed actuator configuration and the control scheme. Numerical simulation results demonstrate that the proposed actuator configuration is effective in shell actuation and control. It is also suggested that the proposed control strategy could give better control responses than the proportional velocity feedback.

Independent Modal Variable Structure Fuzzy Active Vibration Control of Cylindrical Thin Shells Laminated with Photostrictive Actuators

Photostrictive actuator, which can produce photodeformation strains under the activation of ultraviolet lights, is a new promising non-contact photoactuation technique for active vibration control of flexible structures. Generally, the membrane control action plays a major role in vibration control of flexible thin shell structures. However, it is unfortunate that the existing photostrictive actuator configuration can not induce negative membrane control forces. In this paper, a novel multi-layer actuator configuration is first presented to remedy this deficiency, followed by presenting the photostrictive/shell coupling equations of thin cylindrical shells laminated with the proposed multi-layer actuator configuration. Moreover, considering the time-variant and nonlinear dynamic characteristics of photostrictive actuator, variable structure self-adjusting parameter fuzzy active controller is explored to overcome disadvantages of conventional control schemes, in which off-line fuzzy control table is adopted. The optimal switching surface is derived to increase the range of sliding mode to facilitate vibration suppression. A continuous function is used to replace the sign function for reducing the variable structure control chattering. Finally, two case studies are carried out to evaluate the effectiveness of the proposed actuator configuration and the control scheme. Numerical simulation results demonstrate that the proposed actuator configuration is effective in shell actuation and control. It is also suggested that the proposed control strategy could give better control responses than the proportional velocity feedback.

CGLワイピング部における電磁石を用いた鋼板の振動および形状制御

Hot-dip galvanized steel sheets are often used for automobile exterior body panels to enhance the corrosion performance. The requirements for their surface appearance from automakers have become higher recently. Especially, a uniform coating layer of zinc is required. In a continuous hot-dip galvanizing line (CGL), a pair of gas wipers, which are installed just above the zinc pot, is used to control the thickness of the coating layer. The strip vibration at the gas wipers causes the uneven coating thickness in the traveling direction, while the cross-bow of the strip leads to the unevenness in the width direction. The behavior of the strip at the gas wipers should be stable for the uniform coating layer. In order to make the strip stable and flat, a strip vibration and shape control technique using electromagnets has been developed. It greatly contributes to produce hot-dip galvanized steel sheets with excellent surface appearance.

Thermodynamic features of axial vibrational control technique for crystal growth from the melt

Direct measurements of crystallization heat of NaNO3 and CdTe melts activated by low-frequency vibrations by oscillating an inert baffle submerged into the melt demonstrated up to 30% increase compared to the regular melt. At a stationary state the crystallization heat increase depends on vibrational amplitude and frequency. The study of melt structure by Raman spectroscopy proved the assumption about the changing of component composition followed by its restructure under AVC processing. Kinetics of melt reconstruction depending on temperature and vibrational intensity was examined.

汎用マイコンモジュールによるスマート構造のセルフセンシング振動制御

The purpose of this paper is to verify the effectiveness of self-sensing piezoelectric actuation using an affordable micro-controller. In recent years, space structural systems have been required high precision and high functionality for advanced space missions. Vibration control is one of important issues to realize high mirror accuracy of antennas for a high-resolution observation and a high-capacity communication. Generally, active vibration control needs not only actuators and sensors, but also AD/DA converters and highly advanced arithmetic processing. However, it is difficult to mount complex and heavy devices on satellites. A compact and modulized unit for vibration control is necessary. Then, this study focused on an affordable micro-controller that is small, low power consumption and easily-available. And self-sensing actuation was chosen as the vibration control technique to reduce in size and weight of the control system. Numerical simulations and experiments to damp free decay vibration and harmonic vibration of a smart cantilever were demonstrated, and show that the presented approach is very useful for realizing the active vibration control unit.

The Fractional-Order Control Method of Dynamic Elastoplastic Responses of Benchmark Buildings

The elastoplastic phenomenon of the structures will be advent under the action of the strong earthquakes, the presented research on the vibration control of the ones is chiefly concentrated on fuzzy and neuro-controller with the expense of bigger energy. In the paper, the 3-storey benchmark building is used as research object, the control strategy of vibration system with fractional-order is studied. The control method based on acceleration responses output is emphatically concerned as it is usually adopted in most actual application of active vibration control techniques. The concrete courses include the following three steps: the integer-order approximation of fraction-order, the transfer function reduction in frequency-domain which base on Pade approximation, the controller design and simulation. In the last, an example is used to show the feasibility of proposed method.

Active control to reduce the horizontal seismic response of buildings taking into account the soil-structure interaction

In this paper an active vibration control technique to reduce the seismic response of a soil-retaining structure interaction (SRSI) system is presented. The proposed control technique is a synthesis of the adaptive input estimation method (AIEM) and the linear quadratic Gaussian (LQG) controller. The AIEM can estimate online the unknown input. The LQG controller offers optimal control forces to suppress the SRSI system vibration. The control performance of the proposed control technique is numerically evaluated. The obtained results show that the proposed method is more robust than the conventional LQG method.

Educational Use of a Small-Scale Cherrypicker

Cherrypickers are a useful class of machines that can lift people to great heights. Unfortunately, the operator bucket oscillates and the entire machine can tip over in catastrophic accidents. Understanding the dynamics and stability of these machines is crucial for efficient and safe operation. To this end, a small-scale cherrypicker was constructed for experimental dynamic analysis and educational use. The dynamic behavior of the cherrypicker, as well as the improved system response using vibration-control techniques are presented. The cherrypicker was used during fall 2010 as an experimental apparatus in an advanced graduate controls course taught simultaneously at the Georgia Institute of Technology and the Massachusetts Institute of Technology. Its educational use in this multi-institutional course is discussed.