Showing papers on "Active vibration control published in 2006"

Electromagnetic and mechanical characterizations of noise and vibration in permanent magnet synchronous machines

Abstract: The effect of electromagnetic and mechanical characteristics in permanent magnet (PM) synchronous machines on noise and vibration is presented. Some mechanisms of electromagnetic and mechanical interaction of the machine resulting in noise and vibration are analyzed and calculated. Computational and experimental results are also compared. Noise and vibration resulting from electromagnetic forces dominates in the noise and vibration of PM electrical machine on rated load. When the exerting force frequencies coincide with modal frequencies of the stator, the motor can generate high noise and vibration peak

Active vibration control in palletised workholding system for milling

Abstract: This paper presents the development implementation and testing of an active controlled palletised workholding system for milling operations. The traditional approach to controlling vibration in a machining system is to develop control systems for cutting tools or machine spindles as in the case of milling machines. This work is a deviation from the traditional approach and targets a workholding system for the control of unwanted vibration. Palletised workholding systems, due to their compact design, offer an opportunity to design active control systems that are economical and easier to implement in the case of milling machines. The active control system developed here is based on an adaptive filtering algorithm, the filtered X-LMS, and employs piezo-actuators for dynamic control force. The system has been tested experimentally to demonstrate the reduction in dynamic force due to vibration. Extensive testing has been carried out to validate the performance of the system in terms of parameters of practical importance such as improvement in surface finish and increase in tool life.

Active/Passive distributed Absorber for Vibration and Sound Radiation Control

Abstract: Vibration or acoustic sound control is achieved using an elastic layer of thermal or insulation material in which a plurality of discrete masses are distributed throughout. The elastic layer may be installed as a pre-formed layer, or be blown into position within a structure where vibration or acoustic sound control is required.

Active Vibration Control for Subterranean Drilling Operations

Abstract: An active vibration control device improves drilling by actively applying a dampening profile and/or a controlled vibration to a drill string and/or bottomhole assembly (BHA). Embodiments of the present invention control the behavior of a drill string and/or BHA in order to prevent or minimize the occurrence of harmful drill string/BHA motion and/or to apply a vibration to the drill string/BHA that improves one or more aspects of the drilling process. Measurements of one or more selected parameters of interest are processed to determine whether the undesirable vibration or motion is present in the drill string or BHA and/or whether the drill string and/or BHA operation can be improved by the application of a controlled vibration. If either or both conditions are detected, corrective action is formulated and appropriate control signals are transmitted to one or more devices in the drill string and/or BHA.

Development of a three-axis active vibration isolator using zero-power control

Abstract: This paper presents the development of an active 3-degree-of-freedom (DoF) vibration isolation system using zero-power magnetic suspension. The developed system is capable to suppress direct disturbances and isolate ground vibrations of the 3-DoF motions, associated with vertical translational and rotational modes. Two categories of control strategy for the actuators are proposed, i.e., local control and mode control. The latter method allows to overcome limitations of the poor performances for rotational modes exhibited by the former. A mathematical model of the system is derived and each DoF motion is treated separately for the control system. It is demonstrated analytically that the infinite stiffness to static direct disturbances can be generated and the resonance peak due to floor vibration can effectively be suppressed for the system. Moreover, the experiments have been carried out to measure the static and dynamic responses of the isolation table to direct disturbances, and transmissibility characteristic of the isolator from the floor. The results indicate good vibration isolation and attenuation performances, and show the efficacy of the developed isolator for industrialization

Active vibration control using an inertial actuator with internal damping

Abstract: Collocated direct velocity feedback with ideal point force actuators mounted on structures is unconditionally stable and generates active damping. When inertial actuators are used to generate the control force, the system can become unstable even for moderate velocity feedback gains due to an additional -180 degree phase lag introduced by the fundamental axial resonant mode of the inertial actuator. In this study a relative velocity sensor is used to implement an inner velocity feedback loop that generates internal damping in a lightweight, electrodynamic, inertial actuator. Simulation results for a model problem with the actuator mounted on a clamped plate show that, when internal relative velocity feedback is used in addition to a conventional external velocity feedback loop, there is an optimum combination of internal and external velocity feedback gains, which, for a given gain margin, maximizes vibration reduction. These predictions are validated in experiments with a specially built lightweight inertial actuator.

Topology optimization of piezoelectric sensors/actuators for torsional vibration control of composite plates

Abstract: Torsional vibration control can be crucial for applications of smart materials and structures. In this paper, the problem of topology optimization of collocated piezoelectric sensor/actuator (S/A) pairs for torsional vibration control of a laminated composite plate is directly addressed. Both isotropic and anisotropic PZT S/A pairs are considered and it is highlighted that the torsional vibration can be more effectively damped out by employing the topological optimal design of the S/A pairs than by using the conventional designs. To implement this topology optimization, a genetic algorithm (GA) based on a bit-array representation method is presented and a finite element (FE) simulation model based on the first-order shear theory and an output feedback control law is adopted. Numerical experiments are used to verify the present algorithm and show that the present optimal topology design can achieve significantly better active damping effect than the one using a continuously distributed PZT S/A pair, which was often adopted by many other researchers. Together with the progress in laser cutting and micromachining techniques, topology optimization of piezoelectric sensors and/or actuators would be promising in active vibration control of smart structures.

Spacecraft vibration suppression using variable structure output feedback control and smart materials

Abstract: A hybrid control scheme for vibration reduction of flexible spacecraft during rotational maneuvers is investigated by using variable structure output feedback control (VSOFC) for attitude control and smart materials for active vibration suppression. The proposed control design process is twofold: design of the attitude controller using VSOFC theory acting on the hub and design of an independent flexible vibration controller acting on the flexible part using piezoceramics as sensors and actuators to actively suppress certain flexible modes. The attitude controller, using only the attitude and angular rate measurement, consists of a linear feedback term and a discontinuous feedback term, which are designed so that the sliding surface exists and is globally reachable. With the presence of this attitude controller, an additional independent flexible control system acting on the flexible parts is designed for further vibration suppression. Using the piezoelectric materials as actuator/sensor, both single-mode vibration suppression and multimode vibration suppression are studied and compared for the different active vibration control algorithms, constant-gain negative velocity feedback (CGNVF) control, positive position feedback (PPF) control, and linear-quadratic Gaussian (LQG) control. Numerical simulations demonstrate that the proposed approach can significantly reduce the vibration of the flexible appendages and further greatly improve the precision during and after the maneuver operations.

Inertial vibration control using a shunted electromagnetic transducer

Abstract: Inertial drives and passive tuned-mass dampers utilize a suspended mass to reduce the vibration experienced by a host structure. Active vibration control systems typically include a voice coil type electromagnetic actuator to develop the required reaction forces. In this paper, the technique of sensorless active shunt control is applied to inertial vibration absorption. An electrical impedance is designed and connected to an electromagnetic coil with a view to minimizing structural vibration. Standard optimal control tools can be applied to design the required shunt impedance. This technique requires no additional feedback sensors. Vibration in an experimental structure is heavily attenuated by the application of an active shunt impedance.

Active vibration control of nonlinear giant magnetostrictive actuators

Abstract: A nonlinear constitutive model-based vibration control system for giant magnetostrictive actuators (Terfenol-D) is presented in this paper. Such actuators utilize the realignment of magnetic moments in response to applied magnetic fields to generate strains in the material. It has been found that the strains and forces generated in this manner are significantly larger than those produced by many other smart materials, associated with significant and complex nonlinear relations among the quantities of applied magnetic field, strain, and compressive pre-stress. Based on the negative feedback control law and the analytical expressions of the nonlinear constitutive model of Terfenol-D rods, here, the effectiveness of real control systems for suppressing a vibration is confirmed by the simulation results on a case study of negative velocity feedback when its feedback gain is taken in a limit region. It is found that the limit region is dependent on the bias magnetic field and pre-stress. When the gain is employed out of the limit region, the real control system is unstable, but the simulation results on the basis of the linear constitutive model still show a stability of the control systems. To utilize the full potential of these materials in active vibration controls, thus, these inherent nonlinearities of the materials must be considered in the design of the control systems.

Track-Following Control With Active Vibration Damping of a PZT-Actuated Suspension Dual-Stage Servo System

Abstract: In this paper we discuss the controller design of a PZT-actuated suspension dual-stage servo system in hard disk drives. The proposed control structure includes an active vibration damping control loop and a track-following control loop. The vibration damping control loop, which runs at a faster rate than the track-following control loop, utilizes a PZT element on a PZT-actuated suspension as a vibration sensor to damp the resonance modes of the voice coil motor (VCM) and the PZT actuator. The vibration damping controller is designed using Kalman filter based state feedback control techniques. A simple dual-stage track-following controller is designed, based on the damped actuator model, using the sensitivity function decoupling design method. Simulation and experimental results are presented to demonstrate the benefits of this control scheme in expanding servo control bandwidth and suppressing airflow excited structural vibrations.

Vehicular active noise/vibration/sound control system, and vehicle incorporating such system

Abstract: An active noise/vibration/sound control system for a vehicle has an ANC (active noise control apparatus), an AVC (active vibration control apparatus), and an ASC (active sound control apparatus). To prevent the ANC, the AVC, and the ASC from interfering with each other and hence to prevent vehicle cabin environment of vibrations, noise, and sound from being impaired, activation and inactivation of the ANC, the AVC, and the ASC are controlled or their control characteristics are controlled in relation to each other by a weighting variable calculator as a coordination controller, depending on an engine rotation frequency and a frequency change which are representative of a running state of the vehicle as detected by an engine rotation frequency detector and a frequency change detector that serve as a running state detector.

Vibration Control of a Plate using a Self-sensing Piezoelectric Actuator and an Adaptive Control Approach

Abstract: This article describes the active vibration control of a plate using a self-sensing actuator (SSA) and an adaptive control method. In a self-sensing actuator, the same piezoelectric element functions as both a sensor and an actuator so that the total number of piezoelectric elements required can be reduced. A method to balance the bridge circuit of the SSA was proposed and its effectiveness was confirmed by using an extra piezoelectric sensor, which is not necessary for balancing bridge circuits of SSA in future applications. A control system including the SSA and an adaptive controller using a finite impulse response (FIR) filter and the filtered-X LMS algorithm was established. The experimental results show that the bridge circuit was well balanced and the vibration of the plate was successfully reduced at multiple resonance frequencies below 1.2 kHz.

Piezoelectric vibration element and piezoelectric device

Abstract: A piezoelectric vibration element having a favorable drive level characteristic for miniaturization, and a piezoelectric oscillator. The piezoelectric vibration element includes a base made of a piezoelectric material, a plurality of vibration arms extended from the base, a long groove formed along a longitudinal direction of a main surface of each of the plurality of vibration arms, and an exciting electrode provided inside the long groove. A center position in a width dimension of the long groove is decentered in a minus X-axis direction from a center position of an arm width dimension.

Novel Approach to Self-Sensing Actuation for Semi-Active Vibration Suppression

Abstract: A novel self-sensing method using piezoelectric actuators for semi-active vibration suppression is proposed and investigated. By using extended system equations, this self-sensing method can be implemented with a Kalman filter instead of the conventional bridge circuit technique. The method separates electrical status into two cases concerning electrical current, and characterizes each of these to establish the self-sensing system. This method is applicable to multiple-degree-of-freedom structures with multiple piezoelectric actuators. A numerical vibration suppression simulation demonstrated that the self-sensing method works well on a truss structure and has significant robustness against parameter variations. Experimental results also demonstrated that the self-sensing method suppresses not only single-mode vibration but also multiple-mode vibration.

Active Vibration Control of a Flexible Beam Using a Buckling-Type End Force

Abstract: In this paper, we explore the use of end forces for vibration control in structural elements The process involves vibration measurement and observer-based estimation of modal amplitudes, which are used to determine when to apply an end load such that it will remove vibration energy from the structure For this study, we consider transverse vibration of a cantilever beam with a buckling-type end load that can be switched between two values, both of which are below the buckling load The stability of the control system is proven using Lyapunov stability theory and its effectiveness is demonstrated using simulations and physical experiments It is shown that the effectiveness of the approach is affected by the bandwidth of the actuator and the attendant characteristics of the filter, the level of the control force, and the level of bias in the end force The experiments employ a beam fitted with a cable mechanism and motor for applying the end force, and a piezoelectric patch for taking vibration measurements It is shown that the first two modes of the beam, whose natural frequencies are less than the bandwidth of the motor, are very effectively controlled by the proposed scheme

Substrate support vibration structure, input device with tactile function, and electronic equipment

Abstract: PROBLEM TO BE SOLVED: To provide a highly rigid vibration substrate, and to secure high reliability as to vibration transferability, irrespective of a using attitude of the vibration substrate. SOLUTION: The vibration substrate is provided with rigid parts 61a, 61b fixedly provided columnarly or/and longitudinally between a display means 29 and a touch panel 24, and piezoelectric actuators 25a, 25b having a vibration action part 8a and central electrodes 3a, 3b and provided in prescribed positions between the display means 29 and the touch panel 24, or in prescribed positions of longitudinal portions of the rigid parts 61a, 61b, and the vibration action part 8a and the central electrodes 3a, 3b are overlapped along a direction to layer an input detecting means and the display means. By this composition, a highly rigid vibration casing is provided with a property capable of restraining a dimensional change at a low level against a bending force and a torsional torque. COPYRIGHT: (C)2008,JPO&INPIT

Swashplateless Helicopter Rotor System with Trailing-Edge Flaps for Flight and Vibration Controls

Abstract: The objective of this study is to demonstrate the concept of active trailing-edge flaps as primary flight control and vibration reduction devices for a typical full-scale helicopter. A comprehensive rotorcraft analysis based on UMARC was developed to analyze the swashplateless rotor. A parametric study of various key design variables involved in the trailing-edge flap design was carried out. An optimal design of a trailing-edge flap system that provides effective control authority within the complete range of advance ratios as well as minimum actuation requirements was achieved. Trailing-edge flaps demonstrated the capability of performing both primary flight control and active vibration control functions. At a high forward speed (advance ratio of 0.32), the 4/rev vertical force and roll and pitch moments at hub are successfully eliminated (by 90%), and the 4/rev in-plane hub forces are reduced by more than 40%. The half peak-to-peak value of the trailing-edge flap deflection for primary flight control is 7.1 deg, and an additional 4.7 deg is required for active vibration control.

Active Vibration Control of Flexible Structures Using Genetic Optimisation

Abstract: This paper presents an investigation into the development of an adaptive control mechanism for vibration suppression of flexible beam structures using genetic algorithms (GAs). The global search technique of GA is used to estimate the controller transfer function, based on one-step-ahead prediction. An active vibration control (AVC) system is designed utilizing a single-input single-output (SISO) control structure to yield optimum cancellation of broadband vibration at an observation point along the beam. The mean-squared error of observed deflection is adopted as the fitness function and randomly selected controller parameters are optimised for different, arbitrarily chosen order to fit to the system by applying the working mechanism of GA. The global search technique of the GA is utilised to obtain the best parameters among all attempted orders for the controller. The GA-AVC algorithm thus developed is implemented within the simulation environment of a flexible beam structure and simulation results are presented to assess the performance of the system, with different types of excitation namely pseudo-random binary sequence, uniform random and finite duration step signals. It is noted that, the system performance is satisfactory and significant amount of vibration reduction over a broad range of frequencies of the input signal is achieved.

Piezo actuator placement and sizing for good control effectiveness and minimal change in original system dynamics

Abstract: Piezoelectric actuators are commonly considered for active vibration control of smart structures. The placement and sizing of the actuators are normally decided based on control effectiveness. A piezo actuator affects the host structure's mass and stiffness properties and thus alters the original system, which would have been designed to have a certain natural frequency spectrum in relation to the disturbance excitation. For a rotating structure, the mass of the actuator additionally contributes to the centrifugal stiffening effect. In the event of failure of the active system, natural frequencies of the structure with piezos (now rendered passive) become significant. Considering the example of a stationary and rotating beam-like structure, it is attempted to identify the piezo actuator sizing and location that possess significant control effectiveness yet cause minimal change in the system dynamics.

Decentralized harmonic active vibration control of a flexible plate using piezoelectric actuator-sensor pairs.

Abstract: We have investigated decentralized active control of periodic panel vibration using multiple pairs combining PZT actuators and PVDF sensors distributed on the panel. By contrast with centralized MIMO controllers used to actively control the vibrations or the sound radiation of extended structures, decentralized control using independent local control loops only requires identification of the diagonal terms in the plant matrix. However, it is difficult to a priori predict the global stability of such decentralized control. In this study, the general situation of noncollocated actuator-sensor pairs was considered. Frequency domain gradient and Newton-Raphson adaptation of decentralized control were analyzed, both in terms of performance and stability conditions. The stability conditions are especially derived in terms of the adaptation coefficient and a control effort weighting coefficient. Simulations and experimental results are presented in the case of a simply supported panel with four PZT-PVDF pairs distributed on it. Decentralized vibration control is shown to be highly dependent on the frequency, but can be as effective as a fully centralized control even when the plant matrix is not diagonal-dominant or is not strictly positive real (not dissipative).

Method and apparatus for monitoring machinery vibration

Abstract: An apparatus and method for monitoring vibration of the stator core and/or the conductors of electrical machinery during its operation involves positioning vibration sensors at the stator bar ends and operatively coupling the vibration sensors to a central controller. The vibration sensors are axially disposed along the length of an optical fiber and form an interferometer with a reference reflector. The central controller receives a reflected signal from each sensor which represents a measure of the vibration occurring in the stator core and/or the conductors at the location of the sensor.