Showing papers on "Active vibration control published in 2000"

Bearing induced vibration in precision high speed routing spindles

Abstract: This paper presents a detailed model of bearing vibration, including the effect of contact spring non-linearity in balls-to-raceways' contacts. The model incorporates the effect of surface waviness of rolling elements and off-sized balls upon the dynamic internal radial clearance of the bearing. The vibration forces and moments generated are formulated and the significant principal and secondary side-band contributions are highlighted. This model is employed successfully in the recognition of complex real-time vibration spectra of a precision routing spindle, obtained by accurate non-contact sensors.

State-Switched Absorber for Semi-Active Structural Control

Abstract: A system that has the capability to make instantaneous changes in its mass, stiffness, or damping may be termed a state-switchable dynamical system. Such a system will display different dynamical responses dependent upon its current state. For example, state-switchable stiffness may be practically obtained through the control of the termination impedance of piezoelectric stiffness elements. If such a switchable stiffness element is incorporated as part of the spring element of a vibration absorber, the change in stiffness causes a change in the resonance frequencies of the system, thereby instantaneously “retuning” the state-switched absorber to a new frequency. This paper briefly develops the fundamental analysis tools for a Single-Degree-of-Freedom state-switchable device, and then considers the application of such a device for the purpose of vibration control in a 2-DOF system. Simulation results indicate that state-switched vibration absorbers may be advantageous over classical passive tuned vibration...

Experimental verification of the corrected transfer function of a piezoelectric laminate beam

Abstract: Piezoelectric materials are finding increasing applications in active vibration control of structures. Modeling of a piezoelectric laminate, often results in an infinite-dimensional or a very high-order model. For control design purposes, such a model is simplified by removing higher frequency modes which lie out of the bandwidth of interest. Truncation can considerably perturb the in-bandwidth zeros of the truncated model. This paper suggests a method of minimizing the effect of the removed higher order modes on the low-frequency dynamics of the truncated model of a piezoelectric laminate beam by adding a zero frequency term to the low-order model of the structure. Simulations and experimental results are presented.

Active vibration suppression of a flexible structure using smart material and a modular control patch

Abstract: The article of record as published may be found at http://dx.doi.org/10.1243/0954410001532024

Optimum Stiffener Layout for the Reduction of Vibration and Noise of Gearbox Housing

Abstract: Dynamic excitation from the gears generates vibration modes in the gearbox which causes radiation of unwanted structure-borne noise To reduce the noise as well as the vibration, the stiffened plate construction is frequently used for the housing, where the rib stiffener layout is the key to this design In this paper, the most effective position of stiffeners in order to reduce the vibration and noise radiation is searched and discussed The analysis considers first a plate fixed at edges and excited at its center, and then a simplified rectangular gearbox excited at the shaft bearing locations The housing of a simplified single-stage gearbox is modeled by triangular finite shell elements It is excited by a set of harmonic forces which are applied at the bearing positions The rib stiffener is modeled by beam elements, and its optimum layout is searched by a genetic algorithm The vibration energy is adopted as the objective function to be minimized for the design for low vibration On the other hand, the radiated sound power is the objective function for low noise Although the noise is caused by the vibration, the optimum stiffener layout to realize low noise is not always identical to the layout that yields low vibration because of the difference in radiation efficiency This is numerically clarified first from the viewpoint of the vibration mode of a plate In the case of the design for the gearbox housing concerned, the vibration mode which causes the difference in radiation efficiency is not presented Consequently, the optimum stiffener is placed along the line from the point of excitation to a fixed point, which reduces the vibration deflection of the faces with bearings as well as the in-plane displacement of the bearings

High Bandwidth Tunability in a Smart Vibration Absorber

Abstract: An electrically tunable vibration absorber based on the strong ΔE effect of Terfenol-D has been developed. A general description of tuned vibration absorbers is presented along with a description of the magnetostrictive effects that make an electrically tunable Terfenol-D vibration aborber function. It is emphasized that the large modulus changes achievable with the proposed magnetostrictive vibration absorber arise as a consequence of the stiffening of the crystal lattice as the magnetic field is increased from the demagnetized state to magnetic saturation. This is in contrast to the small modulus changes often reported in the literature which are achieved by operating smart materials between their open- and short-circuit states. Experimental results are presented that show agreement with prior art and demonstrate control of a magnetostrictive actuator resonant frequency between 1375 Hz and 2010 Hz by electrically varying the elastic modulus of a magnetostrictive material. This operating principle is then implemented to obtain high bandwidth tunability in a Terfenol-D vibration absorber.

Hybrid passive and active vibration isolator architecture

Abstract: A vibration isolator which may be constructed in the form of a cube for use in retrofitting a device which is subjected to unwanted vibration present in an attached member which utilizes an active vibration isolator and a passive isolator in series between the members and which may include an overload protection device in the form of a deformable member in parallel with the isolators.

Improvement of the longitudinal vibration system for the hybrid transducer ultrasonic motor

Abstract: This paper presents a symmetric hybrid transducer ultrasonic motor designed to produce large longitudinal vibration stress in the rotor/stator contact interface for high-torque operation. The nodal plane of the longitudinal vibration mode was adjusted to match the rotor/stator contact interface, and the piezoelectric ceramic disks for the longitudinal vibration were installed at the nodal plane of the longitudinal vibration mode for effective excitation. An experimental motor, 20 mm in diameter, using the first torsional vibration mode and the second longitudinal vibration mode was manufactured. A maximum torque of 0.8 N/spl middot/m was achieved in the prototype, an improvement over previous versions.

Active vibration isolator, exposure apparatus, exposure method and device manufacturing method

Abstract: An active vibration isolator includes a vibration isolation platform on which an object to be isolated from vibration is mounted, an air-spring actuator which supports the vibration isolation platform, the air-spring actuator including a valve, which is subjected to feedback drive, a vibration measurement device which measures vibration of the vibration isolation platform and outputs acceleration and velocity signals, a position measurement device which measures position of the vibration isolation platform and first, second and third feedback loops. The first feedback loop feeds back an output of a force measurement device, which measures a working force applied by the air-spring actuator to the vibration isolation platform, thereby controlling the working force supplied by the air-spring actuator. The second feedback loop has a PI compensator and signals of the vibration measurement device are fed back to an input side of the compensator, for producing damping and spring effects which act upon the platform. The third feedback loop feeds back an output from the position measurement device, thereby positioning the platform at a designated position.

Self-Powered Active Vibration Control Using Continuous Control Input

Abstract: A new method to achieve self-powered active vibration control is proposed. The proposed system produces continuous control input using energy absorbed by a damper and does not require external energy. In the previous self-powered system, the actuator was controlled by the on-off controller and could not produce continuous control input. This induces chatter for high frequency motion and degrades its performance. To examine the performance of the new system, the authors fabricated an experimental setup. Energy regenerated by the damper is accumulated in the condenser and the actuator uses it for active control. The variable resistor whose resistance is controlled by a computer is installed in the circuit of the actuator and this produces continuous control input. The experiments show that the proposed self-powered active control has better isolation performance than the previous on-off, semiactive and passive systems.

Active vibration control system for helicopter with improved actustor placement

Abstract: An aircraft has a fuselage that defines an interior cabin and an exterior; a first housing located along one side of the fuselage exterior; a second housing located along the second side of the fuselage exterior; and an active vibration control system for limiting fuselage vibration, the vibration control system comprising a plurality of sensors located in the cabin; a controller in signal receiving relation with the sensor means; first actuator means located in the first housing and second actuator means located in the second housing and wherein the actuator means are in signal receiving relation with the controller.

Vibration actuator having three vibration modes

Abstract: In a vibration actuator using a magnetic circuit device (14), a supporting arrangement (23) elastically supports the magnetic circuit device. A coil (17) is inserted into a magnetic gap (15) of the magnetic circuit device and is supported by a vibration plate (19). The vibration actuator has a first operation mode in which the magnetic circuit device mainly vibrates to transmit vibration through the vibration plate to the outside, a second vibration mode in which the coil mainly vibrates to produce a buzzer sound through the vibration plate, and a third vibration mode in which the magnetic circuit device and the coil mainly vibrate to produce a sound corresponding to a speech through the vibration plate.

Rotary knife with electromagnetic active vibration control

Abstract: A rotary knife incorporates the use of an electronically controlled, active damping system to control vibrations of knife cylinders. The system preferably uses pairs of electromagnetic actuators to provide opposing pulling forces on a ferromagnetic portion of a lever arm that is mechanically coupled to the stationary support shaft for the knife cylinder. Vibration sensors, preferably accelerometers, are used to monitor vibrations of the respective knife cylinders. A digital signal processor implementing a state space control system controls the electromagnetic actuators to actively cancel vibration energy in the knife cylinders.

Real-time vibration control using CMAC neural networks with weight smoothing

Abstract: The CMAC neural network concept is applied to real-time active vibration control at audio rates. A new weight smoothing CMAC is used in the control loop to cancel a disturbance input.

Fuzzy control of vibration of a smart CFRP laminated beam

Abstract: In the present study, the fuzzy control of vibration is investigated for a hybrid smart composite beam actuated by piezoceramics and electro-rheological fluids (ERFs) actuators. A carbon fiber reinforced plastics cantilevered beam containing ERF with bonded piezoceramics is vibrated under forced sinusoidal external excitation. A fuzzy model of the controlled element containing two actuators is formed because the application of a linear control theory to the vibration control is difficult due to intense nonlinearity in the ERF actuator. The parameters of the fuzzy model are identified by using a hybrid neuro-fuzzy system. The fuzzy controller for vibration suppression of the composite beam designed is based on the fuzzy model by using modern control theory. The effect of the vibration control system with a fuzzy controller is verified by simulation and experiment.

Active vibration control of smart composite plates using self-adaptive neuro-controller

Abstract: A neural network-based control system is developed for self-adapting vibration control of laminated plates with piezoelectric sensors and actuators. The conventional vibration control approaches are limited by the requirement of an explicit and often accurate identification of the system dynamics and subsequent `offline' design of an optimal controller. The present study utilizes the powerful learning capabilities of neural networks to capture the structural dynamics and to evolve optimal control dynamics. A hybrid control system developed in this paper is comprised of a feed-forward neural network identifier and a dynamic diagonal recurrent neural network controller. Sensing and actuation are achieved using piezoelectric sensors and actuators. The performance of the hybrid control system is tested by numerical simulation of a composite plate with embedded piezoelectric actuators and sensors. Finite-element equations of motion are developed based on shear deformation theory and implemented for the plate element. The dynamic effects of the mass and stiffness of the piezoelectric patches are considered in the model. Numerical results are presented for a flat plate. A robustness study including the effects of structural parameter variation and partial loss of the sensor and actuator is performed. The hybrid control system is shown to perform effectively in all of these cases.

Simulations and experiments on active vibration control of a plate with integrated piezoceramics

Abstract: A frequency domain model on the basis of a rectangular plate with symmetrically integrated piezo-elements is extended to time domain suitable to use for on-line active vibration control simulations. Electromechanical effects of piezoceramic elements such as mass, stiffness and actuation are included in the model. The model is coupled to a control simulator comprising both Feedforward and Feedback algorithms. Simulations are made using the model to investigate some important aspects that may be encountered in practice such as system identification and control performance for different configurations. Finally, both controllers are implemented in DSP boards and experiments are carried out. Results demonstrate the representativeness of the system model and the efficiency of the algorithms for a SISO system. It is noted that the model developed in this paper is accurate and flexible enough to represent the real system in a control situation. The whole on-line simulation process is capable of reproducing reliable results to guide implementation of controllers.

Actuators for active vibration control - tunable resonant devices

Abstract: This paper is concerned with the control of vibration using a smart structure. Such a structure requires actuators and sensors coupled with a controller, but only actuators are discussed here. Because the limiting factor in the active control of vibration is often the actuator, the work described in this paper discusses the use of resonant devices to generate the required secondary force. The control of such a device is much simpler than a fully active system as it simply involves tuning the device so that it operates most effectively at the unwanted disturbance frequency. A major issue is how to design a tunable device, and four ways of achieving this with a simple beam and attached masses are described and compared in this paper.

Active vibration control of a multi-degree-of-freedom structure by the use of direct model reference adaptive control

Abstract: In the paper, the problem of active vibration control of multi-degree-of-freedom high-rise buildings is considered. A direct model reference adaptive control (DMRAC) algorithm is implemented on the multi-degree-of-freedom structure, which is modeled as being composed of spring-mass-damper subsystems. The system is then subjected to earthquake vibrations and wind effects, which are treated as disturbances. Satisfactory vibration suppression is achieved.

Robust Active Vibration Control of a Bandsaw Blade

Abstract: An analytical study of a vibrating bandsaw blade is presented. The blade is modeled as a plate translating over simply-supporting guides. Gyroscopic effects due to the blade's axial motion as well as in-plane forces resulting from tensioning and the influence of the cutting force are included in the model. The latter is modeled as a nonconservative follower force on the cutting edge of the blade and shown to be destabilizing. A state-space model is developed which includes the effects of time-varying cutting forces and exogenous disturbances. Feedback control via a collocated force actuator/rate sensor is introduced and recent advances in robust control theory are used develop controllers which achieve robust stability and performance with respect to the time-varying model.

Hybrid active and passive control of vibratory power flow in flexible isolation system

Abstract: A hybrid active and passive vibration control strategy is developed to reduce the total power flows from machines, subject to multiple excitations, to supporting flexible structures. The dynamic interactions between machines, controllers, and receiving structures are studied. A force feedback control process governed by a proportional control law is adopted to produce active control forces to cancel the transmitted forces in the mounts. Computational simulations of a simple and a multiple dimensional hybrid vibration isolation system are performed to study the force transmissibility and the total power flows from vibration sources through active and passive isolators to the supporting structures. The investigation focuses on the effects of a hybrid control approach to the reduction of power flow transmissions and the influence of the dynamic characteristics of the control on power flow spectra. The hybrid control mechanism is synthesised from the power flow analysis. Conclusions and control strategies, well supported by numerical simulations, are deduced providing very useful guidelines for hybrid vibration isolation design.

Active acoustic and structural vibration control without online controller adjustment and path modeling

Abstract: Active vibration control (AVC) systems without online path modeling and controller adjustment are provided that are able to adapt to an uncertain operating environment. The controller (250, 280, 315, 252, 282, 317, 254, 319) of such an AVC system is an adaptive recursive neural network whose weights are determined in an offline training and are held fixed online during the operation of the system. AVC feedforward, feedback, and feedforward-feedback systems in accordance with the present invention are described. An AVC feedforward system has no error sensor and an AVC feedback system has no reference sensor. All sensor outputs of an AVC system are processed by the controller for generating control signals to drive at least one secondary source (240). While an error sensor (480, 481) must be a vibrational sensor, a reference sensor (230, 270, 295, 305, 330) may be either a vibrational or nonvibrational sensor. The provided AVC systems reduce or eliminate most of such shortcomings of the prior-art AVC systems as use of an error sensor, relatively slow convergence of a weight/waveform adjustment algorithm, frequent adjustment of a path model, use of a high-order adaptive linear transversal filter, instability of an adaptive linear recursive filter, failure to use a useful nonvibrational reference sensor, failure to deal with the nonlinear behavior of a primary or secondary path, weight adjustment using control predicted values, use of an identification neural network, and online adjustment of the weights of a neural network.