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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.
2
Content available remote Online vibration suppression in lathe machine
EN
Purpose: The main objective of the project is to reduce the vibration of the tool and to increase the accuracy of the component. The efficiency of the tool and precise machining can be increased by this project. Design/methodology/approach: In this project sensors and vibration exciter are used. Findings: In order to suppress the vibration, sensors are placed on top of the tool and vibration exciter is placed at the bottom of the tool. The sensors will sense the vibration of the tool and the vibration exciter will generate opposite vibration force to suppress the vibration of the tool. By doing this we can acquire good surface finish of the components. Practical implications: The better surface finishes, increased tool life are obtained as the result of online vibration suppression, this methodology provides the simple and flexible control of vibration over conventional complex methods and the system adopt itself for variation in process parameters more over it is economically feasible.
3
Content available remote Prestressing for reduction of local vibrations in a rotorcraft
EN
The main objective of this paper is to investigate the possibility of local structural vibration suppression via introducing initial prestressing. In order to evaluate the effectiveness of the proposed method, a two-step approach has been used. Firstly, a prestressed modal analysis was conducted to measure the influence of the prestressing on changes of eigenfrequencies and eigenmodes. In the second step, a steady dynamic analysis was performed to harmonic excitation to demonstrate the reduction of local amplitudes. Numerical experiments have been conducted on the model of a small rotorcraft. Our results indicate that introduction of initial prestressing may be used to affect natural structure frequencies and to lower the amplitude of vibrations of the structure exposed to external extortions.
EN
The steam turbine blades of low pressure stages are endangerd by the high-cyclic fatigue due to the combined loading of dynamic stresses by the steam time-variant pressure and the pre-stress from centrifugal forces. Therefore, the importance of their experimental dynamic analysis in the design stage is critical. For laboratory tests of the blades, the piezo actuators placed on the blades, unlike electromagnets placed in the stationary space, give a possibility to excite the flexural vibration of the blades within the bladed disk by time continuous forces independently of the rotor revolutions. In addition, the piezo actuators can be also used to control the vibrations of the blade. Therefore, several dynamic experiments of the clamped model blade equipped with PVDF films were performed for the force description of the piezo foils and their behavior as actuators of the blade vibration. The numerical beam models were used for numerical analysis of the vibration suppression effects both by additional parametric excitation and by active damping. The optimal phase shift of piezo actuator voltage supply was ascertained both for amplitude amplification and suppression. The results contribute to the knowledge of the actuation and active damping of blade vibration by the piezo elements.
PL
W artykule przedstawiono zagadnienia związane z efektywnym tłumieniem drgań skrętnych w napędzie dwumasowym. We wstępie przedstawiono problematykę sterowania napędami z połączeniem sprężystym oraz metodę sterowania z wymuszeniem dynamiki. W kolejnych rozdziałach zaprezentowano model rozpatrywanego napędu oraz proponowaną strukturę sterowania. Następnie przedstawiono wyprowadzenie proponowanego prawa sterowania. Proponowana struktura umożliwia ograniczenia momentu skrętnego. Rozważania teoretyczne i symulacyjne zostały poparte badaniami eksperymentalnymi.
EN
In the paper issues related to the effective damping of the torsional vibration in the two-mass drive system are presented. In the introduction the control problem of the elastic drives as well as the basic of the forced dynamic control are presented. In the next section the model of the considered drives and proposed control structure are shown. Next, the methodology of the design of the control structure based on the forced dynamic control for the two-mass system is presented in detail. The proposed control structure allows the limitation of the shaft torque. The theoretical consideration and simulation study are supported by the experimental tests.
EN
This paper presents the problems encountered in the suppression of vibration in machines with a low degree of rigidity, especially when the vibration is to be suppressed in only part of a facility, as the oscillatory motion of the remaining equipment in the team is its normal working movement. An example of such a device is a vibrating sifter, this being a machine with a percussive (shock) way of operating. The nature of vibrations in this type of equipment depends on the foundation’s rigidity as well as the rigidity of the screen itself. Both may undergo change during operation of the machine, due to cracking of structural elements as a result of the impact of the force causing the movement of the screened material.
7
PL
W artykule przedstawiono wybrane zagadnienia związane z predykcyjną regulacją położenia w napędzie dwumasowym. We wstępie omówiono klasyczne metody sterowania położeniem stosowane w napędzie elektrycznym. Omówiono przyczyny wzrostu zainteresowania sterowaniem predykcyjnym. W dalszej części artykułu zaprezentowano model matematyczny układu napędowego oraz ideę sterowania predykcyjnego. W badaniach symulacyjnych pokazano właściwości dynamiczne i statyczne struktury sterowania pracującej w różnych warunkach. Kolejno, po krótkim opisie stanowiska laboratoryjnego przedstawiono wyniki testów eksperymentalnych. Uzyskane wyniki badań potwierdziły rozważania teoretyczne i udowodniły poprawność pracy układu sterowania.
EN
In the paper selected issues related to the predictive position control of the two-mass drive system are presented. In the introduction a classical methods of positioning of the electric drives are described. Also the reasons for increased popularity of predictive control are mentioned. Then the mathematical model of the two-mass system and the idea of predictive control are presented. In simulation tests performance of the drive system working under different condition are analyzed. Then, the results of the experimental verification of theoretical considerations are shown. The obtained results confirm the proper work of the designed control structure.
8
Content available remote Vibration Suppression of Composite Plate with MFC Active Elements
EN
Application of the Macro Fiber Composite (MFC) as active elements for suppression of composite plate vibrations is presented in this paper. Vibrations are reduced by the Nonlinear Saturation Control (NSC) method. Effectiveness of the algorithm is tested in Matlab package using a reduced model of a plate. The numerical results are verified experimentally.
EN
It is proposed to place the actuators to maximize the mean value of energy transmitted from or dissipated by the actuators, while the sensor location should maximize the mean square value of system output, which also maximizes the signal-to-noise ratio. By using explicit expressions for controllability and observability grammians as well as modal energies, it is shown that the approaches based on the system responses to transient and persistent disturbances are closely related, and are equivalent for structures which damping is small and the natural frequencies of which are well spaced. The method of actuator and sensor optimal location via grammians was proposed and compared it with results given by the method of matrix norms.
PL
Materiały piezoelektryczne mają szerokie zastosowanie w wielu dziedzinach nauki i techniki. Wykorzystywane są m.in. jako odbiorniki dźwięku, mikrofony, transformatory, serwomechanizmy i aktuatory. W artykule zaprezentowano metody modelowania charakterystyki pracy siłownika piezoelektrycznego. W pracy takiego aktuatora występuje zjawisko histerezy. Przedstawiono trzy modele teoretyczne opisujące zjawiska histerezy. Zaproponowano adaptację modelu siły tarcia (model Dahla) do odwzorowania histerezy. Przedstawiono ideę budowy modelu opracowaną przez Preisacha i jej rozszerzenie dla przypadku siłownika piezoelektrycznego. Jako trzeci model zaproponowano funkcję wielomianową opisującą histerezę. Prezentowane modele zostały poddane identyfikacji na podstawie badań doświadczalnych.
EN
Piezoelectric materials have a wide use in many fields of sciences and techniques. They are used as sound receivers, microphones, transformers, serwomachins and actuators. This article presents methods of modelling of piezoelectric actuator characteristics. Piezoelectric elements exhibit hysteresis behavior. Three models describing phenomenon of hysteresis are introduced. To describe the hysteresis a friction model (Dahl model) was used. The model worked out by Preisach is also introduced as well as its application for modelling the piezo actuator. Third model is a polynomial function which is used to describe the hysteresis. Models were identified on the basis of experimental data.
EN
The vibration of a machine tool is mainly caused by the dynamic acceleration of a motion axis and by the forces that act on it. All the disturbance forces are transmitted to the machine tool frame through the drive (motor) and its regulation loop and they excite its vibrations. Thus the achievable dynamics and machining quality is negatively influenced. There are several possibilities how to suppress the excited vibrations including the recently introduced "motor on motor" technique which is based on the serial connection of two linear motors. This paper presents new simulation results performed on the simulation model of a real machine tool. The maximal achievable tuning of the regulation loop parameters of the motion axis equipped with the "motor on motor" technique was confronted with the conventional feed drive setting. The "motor on motor" feed drive properties were also tested in the virtual machining operation mode where the real measured cutting force was used. The sensitivity analysis of the reaction force and the middle mass movement of the "motor on motor" feed drive solution to the predicted cutting force introduced to the feed drive control has been investigated. The middle mass is represented by the shared part of both linear motors which absorbs the high frequency part of the reaction force by its movement.
12
Content available Experimental testing of active feed drive
EN
The main disturbances of the machine tool frame are caused by operation of motion axes. Movement of high dynamic motion axes is connected with powerful force stroke that excite machine tool frame vibration and deteriorate machining surface quality and productivity. There are several possibilities how to suppress this vibration. This deals with the simulation and experimental testing of new advanced conception where the main motor is connected with the frame by an active element that is controlled by intelligent control technique.
EN
The paper deals with the application of the feed-forward and cascade-forward neural networks to mechanical state variable estimation of the drive system with elastic coupling. The learning procedure of neural estimators is described and the influence of the input vector size and neural network structure to the accuracy of state variable estimation is investigated. The quality of state estimation by neural estimators of different types is tested and compared. The simple optimization procedure is proposed. Optimized neural estimators of the torsional torque and the load machine speed are tested in the open-loop and closed-loop control structure of the drive system with elastic joint, with additional feedbacks from the shaft torque and the difference between the motor and the load speeds. It is shown that torsional vibrations of the two-mass system are damped effectively using the closed-loop control structure with additional feedbacks obtained from the developed neural estimators. The simulation results are confirmed by laboratory experiments.
EN
A performance study of a clamped beam with embedded self-sensing piezoceramic actuator will be presented. We will explore a problem in vibration suppress on for the free and forced vibration of the clamped beam. The both, the experimental implementation of the clamped beam with embedded self-sensing piezoceramic and the FEM model are developed and the comparison between experimental and simulation results for free and forced vibration is given.
PL
W artykule przedstawione zostaną badania dotyczące działania belki wspornikowej z wbudowanym inteligentnym siłownikiem piezoceramicznym. Przebadano problem tłumienia swobodnych i wymuszonych drgań belki. Opracowano zarówno doświadczalną realizację belki wspornikowej z wbudowanym inteligentnym siłownikiem piezoceramicznym jak i model MES. Na tej podstawie dokonano porównania pomiędzy wynikami uzyskanymi na drodze doświadczalnej a rezultatami symulacji w przypadku drgań swobodnych oraz wymuszonych.
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