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1
Content available remote Active vibration suppression of axially moving string via distributed force
EN
In the paper the problem of suppression of the waves - traveling along the linear, axially moving string - by the active distributed force is presented. The control law is based upon the idea of wave cancellation. The distributed force density is assumed to be proportional to the string transverse velocity resulting from the original running wave, assumed in the form of packet wave with amplitude modulation. As an objective function of the optimization problem considered the energy dissipated by the damping force segment is taken. Simulation results included demonstrate the effectiveness of the control law assumed and superiority of the distributed damping force over the concentrated force.
EN
Due to their impressive capacity of sensing and actuating, piezoelectric materials have been widely merged in different industrial fields, especially aeronautic and aerospace area. However, in the aeronautic industry, the structures are operating under critical environ-mental loads such as high and very low temperature, which made the investigation of the effect of thermal forces on the piezoelectric struc-tures indispensable to reach the high functionality and performance. The present paper focuses on the effect of thermal loads on the active vibration control (AVC) of structures like beams. For this purpose, a finite element model of composite beam with fully covered piezoelec-tric sensor and actuator based on the well-known high order shear deformation theory is proposed by taking into account the electrical po-tential field and a linear temperature field. Hamilton’s principle is used to formulate the electro-thermo-mechanical governing equations. The negative velocity feedback controller is implemented to provide the necessary gain for the actuator. Different analyses are effectuated to present the effect of the temperature ranging from -70°C to 70°C on the active vibration control of the composite beam.
EN
An active vibration control system is proposed for suppressing the small amplitude plate vibration. The structure under study is a vibrating trapezoidal plate, having a constant thickness, to which MFC (Micro Fiber Composite) actuator is bonded. It was assumed, that the plate clamped at one edge is excited by a uniform periodic force generated by a loudspeaker. The control problem lies in using MFC actuator to reduce the plate vibrations. For the system under consideration the mathematical model obtained on the base of parametric identification method is constructed. This part of the research was done with the help of Polytec laser vibrometer. The apparatus is highly advanced tool that allows measurement of vibration of examined structure. With transfer function model obtained in identification process, using Matlabs Identification Toolbox, feedback control laws was created for changing response of the system in desired way. There are many ways to model controller having mathematical model of the object. In this article, authors propose approach to design an effective controller for vibration suppression of a trapezoidal plate with the use of the pole placement method in graphical SISOTool environment. This article describes concept, results of simulation tests and implementation for the designed controller.
EN
Vibration phenomena in mechanical structures including conical shells are usually undesirable. In order to overcome this problem, this study investigates active vibration control of isotropic truncated conical shells containing magnetostrictive actuators. The first-order shear deformation theory and the Hamilton principle are handled to obtain vibration equations. Moreover, a negative velocity feedback control law is used to actively suppress the vibration. The Ritz and modified Galerkin methods are utilized to obtain results of shell vibration. The results are validated by comparison with the results of literature and finite element software. Finally, the effects of control gain value, magnetostrictive layers thickness, isotropic layer thickness, length and semi-vertex angle of the conical shell on vibration suppression characteristics are obtained in details.
EN
Nowadays, feed axes are often equipped with multiple parallel-acting actuators in order to increase the dynamics of the machine tool. Also, additional actuators for active damping are widely used. Normally, the drives or actuators are controlled independently without consideration for the impact on each other. In contrast, by using the modal space control, the system can be decoupled and the modal control loops can be adjusted independently. This control approach is particularly suitable for motion systems, such as machine tools, which have more drives or actuators than degrees of freedom of movement. This paper deals with the pre-investigation of the modal-based vibration control for machine tools with additional actuators. The object of investigation is an elastic system with a movable saddle. The modal-based control is compared with a local control approach. The results obtained experimentally on the test rig are presented. The modal control is superior since, with the modal approach, each control loop corresponds to a specific vibration mode, and the control law for this loop is designed to provide the desired performance of the control system at the corresponding resonance frequency. The parameterisation of the control loops is simplified by modal control, since the modes can be controlled independently.
PL
W artykule zaprezentowano przykład zastosowania Operatora Energetycznego Teagera-Kaisera w automatycznym wyważaniu wirnika. Operator Energetyczny Teagera-Kaisera jest metodą analizy sygnału, która pozwala w dla niektórych obiektów mechanicznych oszacować zmiany energii w ujęciu newtonowski za pomocą sygnału przemieszczenia. Wirniki są elementem konstrukcyjnym wykonującym obrót wokół osi. Tradycyjne wyważanie wirników polega na wprowadzaniu mas korekcyjnych, których celem jest zmniejszenie drgań i hałasu podczas pracy maszyn. Możliwe jest również nadążne wyważania rotorów. Może ono być realizowane przez system mas korekcyjnych o zmiennej odległości od osi obrotu. Zmiana odległości masy korekcyjnej od osi obrotu wpływa na zmianę bezwładności obiektu a tym samym zmniejsza niewyważenie. W zależności od konstrukcji urządzenia modernizacja może zakładać rozbudowę lub wymianę poszczególnych elementów. Poprawa pracy urządzenia wymaga selekcji elementów w zależności od całościowej ingerencji w pracę maszyny oraz wpływu na prace całego urządzenia. Przedstawiona autorska metoda sterowania automatycznego niewyważeniem z wykorzystaniem Operatora Energetycznego z doborem parametrów została wykonana na rzeczywistym stanowisku laboratoryjnym.
EN
The article presents an example of application of the Teager-Kaiser Energy Operator in automatic rotor balancing. The Teager-Kaiser Energy Operator is a signal analysis method, which allows for some mechanical objects to estimate energy changes in Newtonian terms by means of a displacement signal. Rotors are a structural element that rotates around an axis. Traditional balancing of the rotors is based on the introduction of correction masses, the aim of which is to reduce vibrations and noise during machine operation. Traditional balancing of the rotors is also possible. It can be realized by a system of correction masses with variable distance from the axis of rotation. The change of the correction mass distance from the axis of rotation influences the change of inertia of the object and thus reduces the unbalance. Depending on the design of the device, the modernization may assume extension or replacement of individual elements. Improvement of the operation of the device requires selection of elements depending on the overall interference in the operation of the machine and the impact on the operation of the entire device. The presented original method of automatic unbalance control with the use of the Energy Operator with the selection of parameters has been performed on a real laboratory stand.
EN
In traditional active vibration control, a single-objective control output is often considered and constrained, but in fact some conflicting performance indexes are always emerging simultaneously and a one-sided method for pursuing only one excellent output is adopted, which may sacrifice other control characteristics. In this paper, a novel active vibration control with multi-objective control output was proposed for machinery equipment and sensitive equipment, and the latest artificial intelligence – multi-objective particle swarm optimization (MOPSO) was utilized, and the active controller was evaluated by the H∞ criterion, meanwhile an active control with a single-objective control output was also carried out for comparison. Numerical studies demonstrated that a pair of conflicting indexes could be balanced well in the proposed strategy, and thus only one blindly pursued control output was effectively overcome.
EN
This paper presents position and vibration control of a flexible robot composed of two rigid and one flexible links. Position is controlled by the current applied to the DC motor armature. To control vibrations of the flexible structure, Shape Memory Alloys (SMA) are used. Due to phase transformations, the SMA can change its stiffness through temperature variation, considering and taking advantage of this characteristic the vibration control is done. Control is achieved via the State Dependent Ricatti Equations (SDRE) technique, which uses suboptimal control and system local stability search. The simulation results show the feasibility of the proposed control for the considered system.
EN
It is possible to enhance acoustic isolation of the device from the environment by appropriately controlling vibration of a device casing. Sound insulation efficiency of this technique for a rigid casing was confirmed by the authors in previous publications. In this paper, a light-weight casing is investigated, where vibrational couplings between walls are much greater due to lack of a rigid frame. A laboratory setup is described in details. The influence of the cross-paths on successful global noise reduction is considered. Multiple vibration actuators are installed on each of the casing walls. An adaptive control strategy based on the Least Mean Square (LMS) algorithm is used to update control filter parameters. Obtained results are reported, discussed, and conclusions for future research are drawn.
EN
Successful implementation of an active vibration control system is strictly correlated to the exact knowledge of the dynamic behavior of the system, of the excitation level and spectra and of the sensor and actuator’s specification. Only the correct management of these aspects may guarantee the correct choice of the control strategy and the relative performance. Within this paper, some preliminary activities aimed at the creation of a structurally simple, cheap and easily replaceable active control systems for metal panels are discussed. The final future aim is to control and to reduce noise, produced by vibrations of metal panels of the body of a car. The paper is focused on two points. The first one is the realization of an electronic circuit for Synchronized Shunted Switch Architecture (SSSA) with the right dimensioning of the components to control the proposed test article, represented by a rectangular aluminum plate. The second one is a preliminary experimental study on the test article, in controlled laboratory conditions, to compare performances of two possible control approach: SSSA and a feed-forward control approach. This comparison would contribute to the future choice of the most suitable control architecture for the specific attenuation of structure-born noise related to an automotive floor structure under deterministic (engine and road-tyre interaction) and stochastic (road-tyre interaction and aerodynamic) forcing actions.
PL
Udana implementacja układu aktywnej kontroli drgań jest ścisle uwarunkowana dokładną znajomością dynamicznych właściwości obiektu, poziomu i zawartości widmowej wymuszeń, a także parametrów czujników i elementów wykonawczych. Jedynie właściwe uwzględnienie wszystkich tych aspektów może zagwarantować poprawny wybór strategii sterowania i wynikające z niej działanie systemu. W pracy przedstawiono i przedyskutowano wyniki badań wstępnych ukierunkowanych na stworzenie prostego strukturalnie, taniego i łatwo wymienialnego aktywnego systemu sterowania, przeznaczonego dla paneli metalowych. Ostatecznym celem ma być kontrola i ograniczenie hałasu wytwarzanego przez drgające płyty metalowe w nadwoziu samochodu. Artykuł koncentruje się na dwu zagadnieniach. Pierwszym z nich jest realizacja układu elektronicznego działającego w architekturze synchronicznie kluczowanego bocznika (SSSA), z elementami dobranymi odpowiednio do sterowania testowanym obiektem, którym jest prostokątna płyta aluminiowa. Drugim celem jest wstępne studium doświadczalne nad zachowaniem się obiektu badanego, w kontrolowanych warunkach laboratoryjnych, służące porównaniu dwu możliwych koncepcji sterowania: z wykorzystaniem architektury synchronicznie kluczowanego bocznika (SSSA) oraz sterowania ze sprzężeniem wyprzedzającym. W przyszłości wyniki porównania ułatwią dokonanie wyboru architektury sterowania najwłaściwszej dla tłumienia hałasu strukturalnego wytwarzanego przez podłogę nadwozia samochodu pod wpływem wymuszeń deterministycznych (pochodzących od silnika i interakcji między oponami i nawierzchnią) oraz stochastycznych (aerodynamicznych i interakcji opona-nawierzchnia).
EN
Vibration control is critically important for engineering equipment, and in modern industrial engineering active strategies with robust performance are often adopted. In traditional studies, a single-objective consideration is often taken into account when robust control is performed, while a simultaneous multi-criterial consideration is ignored. The study outlined in this paper focuses on typical equipment, namely machinery and sensitive equipment. Meanwhile, evaluation of robust performances based on feedback control is considered as the vibration control objective, and performance indexes using H∞ and H2 criterion are regarded as fitness functions. In addition, the latest intelligent algorithm – MOPSO (multi-objective particle swarm optimization) is used and the SPEA2 (strength Pareto evolutionary algorithm 2) is also introduced for comparison as a representative of evolution algorithm. Numerical results show that the Pareto frontier of MOPSO is much smoother and more uniformly distributed than SPEA2, and even more important is that MOPSO can obtain a unique, global and optimal solution gbest, which can avoid having to select just one from a group of equivalent solutions Finally, an analysis of factors which affect the norms is performed, and the numerical verification shows that the disturbance type (single input or multi input) can apparently affect the magnitude of norms, and this finding can provide a broader understanding of robust vibration control. This research proposes a novel multi-objective optimization strategy for robust vibration control, while the traditional approaches can and are still employed. In addition, advanced artificial intelligence plays an important role in vibration detection in engineering application.
EN
Light flexible structures are easily prone to vibrate due to external forces or due to forces generated in the inner structure. This situation is common in machinery or mechanical structures with rotational devices. The unwanted vi-bration of such structures can be compensated with the addition of piezoelectric actuators for active vibration control (AVC). The rejection of harmonic disturbances is frequently done with controllers based on the internal model principle. The goal of this research is to reduce the effect of harmonic disturbances with known (measured) time-varying fre¬quencies acting on a system as well as to increase the damping of the system for the transient response (first mode of vibration). The experimental setup is made up of a slender aluminium flexible beam, a pair of piezoelectric actuators, an accelerometer and two DC motors, as well as the data acquisition and signal conditioning equipment. The harmonic disturbance is generated by DC motors. The control design utilizes an augmented description of the plant. The plant including the disturbance is modelled as a polytopic linear parameter-varying (pLPV) system. An observer-based gain-scheduling controller is calculated based on quadratic stability and the stability is guaranteed for the specified range ofvariation of the scheduling parameters, also restriction in the performance is introduced in the sense of the H2-norm. Experimental results show very good disturbance cancellation.
PL
Lekkie konstrukcje są podatne na drgania wzbudzane przez wymuszenia zewnętrzne oraz siły występujące wewnątrz układu. Drgania tego typu konstrukcji mogą być zredukowane przy zastosowaniu aktuatorów piezoelektrycznych i układów aktywnej regulacji. Układy eliminacji drgań często wykorzystują regulatory zaprojektowane przy wykorzysta¬niu modelu obiektu. Celem obecnych badań była redukcja wpływu harmonicznie zmiennych parametrów układu oraz zwiększenie tłumienia drgań nieustalonych. Obiekt sterowania został zamodelow any jako liniowy układ niestacjonarny. Układ regulacji uwzględniający obserwator stanu został zaprojektowany przy wykorzystaniu normy H2. Przeprowadzono weryfikację doświadczalną zaproponowanej metody. W skład stanowiska doświadczalnego wchodziły: podatna bel¬ka wykonana z aluminium, para aktuatorów piezoelektrycznych, akcelerometr, dwa silniki prądu stałego oraz układ akwizycji danych i ich kondycjonowania. Zaburzenie harmoniczne było generowane przez silniki prądu stałego. Wyniki badań doświadczalnych potwierdziły dużą skuteczność zaproponowanej metody redukcji drgań.
13
Content available Active rotor vibration control
EN
The article deals with the analysis of active vibration control of a rotor which is supported by journal bearings. The oil fi lm between the journal and bushing induces the rotor instability, which causes rotor vibrations if rotational speed is greater than a threshold of system stability. This phenomenon is very important for high-speed rotational machines for which restricts the operational range of the rotational speed. Therefore increasing the rotor stability threshold is very important for preventing rotor vibrations. The rotor instability results in lateral vibrations which do not conform to the forces of the unbalanced masses or other external forces. The frequency of the lateral vibration is slightly less than half of the rotational frequency. The main result of the article is the analytical determination of the infl uence of the setting of the PD type controller on the threshold of stability.
PL
Artykuł omawia analizę aktywnego sterowania drganiami wirnika podpartego łożyskami ślizgowymi. Film olejowy w szczelinie pomiędzy czopem i panwią łożyska wywołuje niestabilność wirnika, co dla prędkości obrotowej większej od progu stabilności systemu powoduje jego drgania. Zjawisko to jest bardzo ważne dla maszyn o wysokich prędkościach obrotowych, ponieważ ogranicza zakres prędkości roboczych. Dlatego podwyższenie progu stabilności wirnika jest bardzo znaczące dla zapobiegania drgań wirnika. Niestabilność wirnika przejawia się drganiami poprzecznymi, które nie są w zgodzie z siłami niewyważenia oraz pozostałymi siłami zewnętrznymi. Częstotliwość tych drgań poprzecznych jest nieco mniejsza niż połowa częstotliwości obrotowej wirnika. Podstawowym wkładem artykułu jest analityczne pokazanie wpływu regulatora PD na próg stabilności wirnika.
14
Content available Simulations of the active cab suspension
EN
In the context of growing ergonomic concerns and pressing competition on the market, designing machines and vehicles offering a better operator comfort has become a major trend in development of heavy-duty machines and vehicles. During the ride over the rough terrain, the cab is subjected to excitations in the form of low frequency and high-amplitude vibration. This study investigates the vibration reduction strategy whereby the machine structure should incorporate an active suspension of the cab. An actuating mechanism is incorporated, connected to the machine frame and the cab, and placed in between. The main system component is a mobile platform to which the cab is attached. Respective drives set in motion the passive links in the actuating mechanism. The drives are equipped with cylinders capturing the instantaneous velocities derived in the control sub-system. The machine frame, subjected to kinematic excitations, performs a movement in space, which has to be measured with a set of sensors to support the control process. Basing on the measured movements of the machine frame, the control sub-system calculates the realtime values of the anticipated load and the required drive velocities. This study focuses on the development of a mechanical model of the actuating mechanism operating in several degree of freedom options. Solving the direct and inverse problems involving the position and velocity of the mechanism allows the Jacobean matrix to be applied in Newton-Euler’s equations. The purpose of the active suspension system is to stabilise the cab in the vertical position and to reduce its lateral vibrations and seat vibrations in the vertical. This study summarises the results of simulations performed to evaluate the system's performance and its power demand.
EN
The active vibration control system for 3D mechanical structures is presented in the paper. The steel space framework which consists of 126 steel bars and 44 aluminium joints is a subject of our investigations. It is equipped in two piezoelectric stacks which are a part of chosen vertical bars in a plane X-Z. Bars, joints and piezo-stacks have got glue connections. The mathematical model was decoupled to change Two Input Two Output (TITO) system into two Single Input Single Output (SISO) systems. Such approach allowed us to design simple control laws with help of computer simulation procedure. In the last chapter the investigations on the laboratory stand of the active vibration control system with local controllers PD are described. Experimental results have proved that these PD controllers work good increasing the damping level. Additional damp in the system causes the excellent vibration reduction for the whole mechanical structure.
PL
Aktywne sterowanie drganiami przestrzennej konstrukcji prętowej zostało przedstawione w poniższym artykule. Obiektem badań jest przestrzenna konstrukcja prętowa zawierająca 126 elementów prętowych, 44 aluminiowe węzły oraz dwa piezostosy. Wspomniane piezoelektryczne aktuatory stosowe zostały wklejone do konstrukcji w wybranych pionowych elementach prętowych w płaszczyźnie X-Z. Globalny model matematyczny obiektu jest układem o dwóch wejściach i dwóch wyjściach (TYTO), który na potrzeby projektowania praw sterowania został rozprzężony na dwa podukłady o jednym wejściu i jednym wyjściu (SISO). Projektowanie praw sterowania zostało przeprowadzone na drodze badań symulacyjnych w środowisku Matlab. W końcowej części artykułu opisano badania eksperymentalne wraz z zaprojektowanymi lokalnymi regulatorami PD. Wyniki tych badań udowadniają, że wspomniane regulatory PD zwiększają poziom tłumienia. Tym samym dodatkowe tłumieniem które pojawiło się w układzie powoduje znakomitą redukcję drgań całej konstrukcji mechanicznej.
16
Content available remote Control of active piezoelectric beam system applying DSP – based controler
EN
The paper presents laboratory setup based on DSP-controller used to achieve active control of mechanical vibrations and to determine characteristics of smart materials. Smart materials are composite structures with built-in piezo-actuators and sensors. Some preliminary experimental results are presented in the paper, in particular parameter identification of a supply system (gain factor, bandwidth, time constants) and beam (resonant frequencies, damping factors) is shown.
PL
W artykule przedstawiono układ laboratoryjny oparty na układzie DSP umożliwiający kontrolę drgań mechanicznych i wpływanie na właściwości materiałów inteligentnych. Materiały inteligentne tworzą struktury kompozytowe z wbudowanymi elementami aktywnymi i czujnikami. W artykule przedstawiono wyniki eksperymentów, a w szczególności identyfikację parametrów od strony układu zasilania (współczynnik wzmocnienia, pasmo przenoszenia, stałe czasowe) oraz parametrów belki (częstotliwość rezonansowa, współczynnik tłumienia).
17
Content available remote Kontrola drgań konstrukcji
PL
Kontrola drgań jest ważnym problemem, ze względu na wymagania konstrukcyjne i komfort użytkowników budowli. W artykule przedstawiono zwięzły opis nowoczesnych metod kontroli drgań konstrukcji z ich zaletami i ograniczeniami. Ponadto opisano też zasady działania kilku wybranych urządzeń kontroli drgań, z uwzględnieniem ich zastosowania.
EN
Vibration control is an important aspect in terms of structural reąuirements and comfort for people using a building. Modern methods of vibration control of structures with their advantages and limitations arę described in the paper. An operation of selec-ted control devices in the context of its application is also presented.
18
Content available remote Prototype magnetorheological fluid damper for active vibration control system
EN
Purpose: The paper presents a concept of a system for isolation from external vibration sources with use of a magnetorheological (MR) dampers. Design/methodology/approach: Results of experimental studies of a prototype magnetorheological damper at various magnitudes of control current and the manner of modelling electromagnetic phenomena occuring in the damper are presented in this paper. The effect of magnetic field on magnetorheological fluid is modelled by the finite element method. The mathematical model of the system as well as the damper model are outlined along with the relevant control facilities. Numerical simulations were carried out for an exemplary excitation. Findings: The elaborated damper and applied control algorithms substantially infuences the values for velocities and accelerations. Incorporation of a controllable damper into the stabilization system significantly decreases displacements of the mass to be stabilized being the results of shocks and bumps caused by excitations w(t) as a compared to similar displacement of the same mass when only a passive damper was used. Research limitations/implications: For the future research it is necessary to improve characteristics of elaborated damper in order to improve its efficiency. Practical implications: Many mechanical systems should separate from sources of vibrations. The active or semiactive vibration control systems offer a number of advantages as compared with passive systems so that better efficiency of vibration damping is assured. Originality/value: The paper presents new concept of vibration damper with magnetorheological fluids and way of its application in industrial practice.
EN
In this paper application of piezomaterials used as distributed sensor and actuator for active vibration control is shown. The research proved that piezoelectric patches could be applied to systems in which the control of dynamic features is reąuired.
20
Content available remote Predictive feedback approach to structural vibration suppresion
EN
The problem of active vibration control of a plate has been vastly researched and described in recent years. Theoretical and experimental results demonstrate the effectiveness of the designed controllers and indicate the potential of control techniques for reducing transient and steady state dynamics in structural acoustic systems. The examples from the computational studies, confirmed that vibration levels could be effectively reduced, however, the implementation procedures are not yet ideal, still exists the gap between experimental and simulations findings. To overcome this problem, autors propose extension for the Fuzzy-PID controller, with an on-line identification technique coupled with a control scheme, for a plate vibrationsupression. It is assumed, that the system to be regulated is unknown, the control schemes presented in this work have the ability to identify and suppress a plate vibrations with only an initial estimate of the system order. A prediction method implemented was designed using a neutral network (NN) identification algorithm, based on the well-known Runge-Kutta methods. This algorithm is similar to described by Wang and Lin [14], but it uses a copmutation structure of Runge-Kutta-3/8. with radial cosine basis neural network.
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