Vibration Control Applications Research Articles

Dynamically tuned magnetostrictive spring with electrically controlled stiffness

This paper presents the design and testing of an electrically controllable magnetostrictive spring that has a dynamically tunable stiffness (i.e., a magnetostrictive Varispring). The device enables in situ stiffness tuning or stiffness switching for vibration control applications. Using a nonlinear electromechanical transducer model and an analytical solution of linear, mechanically induced magnetic diffusion, Terfenol-D is shown to have a faster rise time to stepped voltage inputs and a significantly higher magnetic diffusion cut-off frequency relative to Galfenol. A Varispring is manufactured using a laminated Terfenol-D rod. Further rise time reductions are achieved by minimizing the rod’s diameter and winding the electromagnet with larger wire. Dynamic tuning of the Varispring’s stiffness is investigated by measuring the Terfenol-D rod’s strain response to dynamic, compressive, axial forces in the presence of sinusoidal or square wave control currents. The Varispring’s rise time is ms for 1 A current switches. Continuous modulus changes up to 21.9 GPa and 500 Hz and square wave modulus changes (dynamic effect) up to 12.3 GPa and 100 Hz are observed. Stiffness tunability and tuning bandwidth can be considerably increased by operating about a more optimal bias stress and improving the control of the electrical input.

Modelling of Hysteresis in Vibration Control Systems by means of the Bouc-Wen Model

The review presents developments concerning the modelling of vibration control systems with hysteresis. In particular, the review focuses on applications of the Bouc-Wen model that describes accurate hysteretic behaviour in vibration control devices. The review consists of theoretical aspects of the Bouc-Wen model, identification procedures, and applications in vibration control.

Realization of Resonance of a Diaphragm at Any Desired Frequency

AbstractIn noise control, the reactance of a mechanical system needs to be minimized while the resistance is chosen suitably. This work illustrates the possibility of and the ease at which such design tasks may be accomplished by utilizing strong electromechanical coupling. Moving-coil loudspeaker is chosen as the vehicle of illustration and it is considered as a simple spring-mass system when operated below its first diaphragm mode. It is shown that the system mechanical property may be tuned easily by a simple R-LC circuit. In addition to the assigned resonance frequency, there can be a maximum of two other resonances. It is argued that the ability to tune the system mechanical resonance to any frequency, such as the ones at very low frequencies, can be very useful for noise and vibration control applications.

Delayed-feedback vibration absorbers to enhance energy harvesting

Recovering energy from ambient vibrations has recently been a popular research topic. This article is conceived as a concept study that explores new directions to enhance the performance of such energy harvesting devices from base excitation. The main idea revolves around the introduction of delayed feedback sensitization (or tuning) of an active vibration absorber setup. To clarify the concept, the Delayed Resonator theory is reviewed and its suitability for energy harvesting purposes is studied. It is recognized that an actively tuned and purely resonant absorber is infeasible for such applications. The focus is then shifted to alternative tuning schemes that deviate from resonance conditions. Also called Delayed Feedback Vibration Absorbers, these devices may indeed provide significant enhancements in energy harvesting capacity. Analytical developments are presented to study energy generation and consumption characteristics. Effects of excitation frequency and absorber damping are investigated. The influences of time-delayed feedback on the stability and the transient performance of the system are also treated. The analysis starts from a stand-alone absorber, emulating seismic mass type harvesters. The work is then extended to vibration control applications, where an absorber/harvester is coupled with a primary structure. The results are demonstrated with numerical simulations on a case study.

Energy Regeneration From Suspension Dynamic Modes and Self-Powered Actuation

This paper concerns energy harvesting from vehicle suspension systems. The generated power associated with bounce, pitch, and roll modes of vehicle dynamics is determined through analysis. The potential values of power generation from these three modes are calculated. Next, experiments are carried out using a vehicle with a four jack shaker rig to validate the analytical values of potential power harvest. For the considered vehicle, maximum theoretical power values of 1.1, 0.88, and 0.97 kW are associated with the bounce, pitch, and roll modes, respectively, at 20 Hz excitation frequency and peak-to-peak displacement amplitude of 5 mm at each wheel, as applied by the shaker. The corresponding experimental power values are 0.98, 0.74, and 0.78 kW. An experimental rig is also developed to study the behavior of regenerative actuators in generating electrical power from kinetic energy. This rig represents a quarter-vehicle suspension model where the viscous damper in the shock absorber system is replaced by a regenerative system. The rig is able to demonstrate the actual electrical power that can be harvested using a regenerative system. The concept of self-powered actuation using the harvested energy from suspension is discussed with regard to applications of self-powered vibration control. The effect of suspension energy regeneration on ride comfort and road handling is presented in conjunction with energy harvesting associated with random road excitations.

A novel magnetorheological actuator for micro-motion control: identification of actuating characteristics

A novel actuator using magnetorheological (MR) fluid sandwiched between two electrode type coils is proposed in this research work. The key enabling concept of the proposed actuator is to enhance the force due to the magnetic field produced by the electrode coil using the magnetorheological fluid. The direction and amount of current input to the top and bottom electrode coils decide the characteristics such as contraction, extension and the force generated by the actuator, respectively. To obtain the required displacement and actuation force, the viscosity of the MR fluid sandwiched between the two electrode coils is precisely varied by the input current. In this work, the MR fluid is operated in one of the most powerful modes, called squeeze mode, and hence the designed magnetorheological actuator is more powerful and precise. The experimental results shown in this paper show that it has a great advantage in micron-level displacement and vibration control applications. The main contribution of this innovative magnetorheological actuator design is that it can also behave like a damper. This technology will lead to a new dimension in the design of self-actuation and damping devices. In addition, the proposed magnetorheological actuator has additional advantages such as cost effectiveness and easy implementation.

Neurodynamics-Based Robust Pole Assignment for High-Order Descriptor Systems.

In this paper, a neurodynamic optimization approach is proposed for synthesizing high-order descriptor linear systems with state feedback control via robust pole assignment. With a new robustness measure serving as the objective function, the robust eigenstructure assignment problem is formulated as a pseudoconvex optimization problem. A neurodynamic optimization approach is applied and shown to be capable of maximizing the robust stability margin for high-order singular systems with guaranteed optimality and exact pole assignment. Two numerical examples and vehicle vibration control application are discussed to substantiate the efficacy of the proposed approach.

Fluid-structure interaction effects for minimizing transmission in waveguides: Time and frequency domain approach

In many noise and vibration control applications, transmission loss in waveguides needs to be maximized. We propose a waveguide comprising of two different fluids with large impedance mismatch. The two dissimilar fluids are separated by two identical spring-mass combinations. An analytical model for such waveguide is undertaken using principles of one-dimensional linear wave propagation theory. Transmission loss for the waveguide across the frequency range is formulated in terms of (i) impedance mismatch of the fluids (ii) fluid-structure interaction parameter. It is shown that an appropriate choice of the above two parameters leads to a minimal transmission across the frequency range. The above inference is also corroborated through transient Finite Element Analysis. For transient simulation an initial condition is imposed on the system and the simulation is carried on till the first transmission is observed. The ratio of the maximum response in the transmitted pulse to the maximum response in the incide...

The three-hinged arch as an example of piezomechanic passive controlled structure

Although piezoelectric transducers are employed in a variety of fields, their application for vibration control of civil or industrial structures has not yet been fully developed, at the best of authors’ knowledge. Thanks to a new generation of ever more performing piezoceramic materials and to the recent development of scientific proposals based on a very simple technology, this paper presents a step forward to engineering applications for the control of structural systems. A three-hinged arch controlled by piezoelectric stack actuators and passive RL electrical circuits is chosen as a simple structural model that may represent the starting point for a generalization to the most common typologies of civil and industrial engineering structures. Based on the concept of electromechanical analogy, the evolution equations are obtained through a consistent Lagrangian approach. A multimodal vibration suppression is guaranteed by the spectral analogy between the mechanical and electrical components. Preliminary applications related to free oscillations, with one or more actuators on each member, seem to lead to excellent performance in terms of multimodal damping and dissipated energy.

Influence of shock impulse characteristics on vibration control using nonlinear fluid viscous dampers

Energy dissipating damping devices such as fluid viscous dampers (FVDs) often have applications in shock vibration control of structural and mechanical systems. Nonlinear FVDs are more suitable compared to the linear FVDs for applications where large force and velocities are exerted, such as in structures subjected to shock excitations. This paper discusses the influence of shock impulse characteristics on vibration control of a single-degree-of-freedom system with linear and nonlinear fluid viscous dampers for three types of shock excitation profile, viz. half-cycle sine, initial-peak saw tooth and rectangular. The following response parameters have been considered: (1) maximum acceleration of the structure, (2) maximum displacement of the structure, and (3) time required for attenuation of response below a specified threshold. An approximation based on the concept of equal energy dissipation to determine the response of the structure with nonlinear fluid viscous dampers subjected to shock excitation has been proposed. The paper also presents non-dimensional design charts for above shock pulses for linear and nonlinear fluid viscous dampers, which can be used for preliminary decision on damper parameters to be used in design.

Studies of band gaps in flexural vibrations of a locally resonant beam with novel multi-oscillator configuration

To realize a broadened band gap as a potential application of vibration control in the electric vehicle powertrain system requires, a novel configuration of locally resonant (LR) beam with multi-oscillators attached is proposed, in which two types of oscillators are periodically and alternately attached at identical intervals. An analytical model is proposed based on transfer matrix method, which is validated by a finite element simulation. The band gaps in flexural vibration generated by this novel structure are investigated by the analytical model. The band gap coupling effect is observed and the influence of the intervals and oscillator parameters are discussed. The novel configuration effectively enlarges the range of band gaps in flexural vibrations.

Design and application of permanent magnet flux sources for mechanical testing of magnetoactive elastomers at variable field directions.

Magnetoactive elastomers (MAEs) are a class of smart materials whose mechanical properties can be rapidly and reversibly changed by an external magnetic field. Due to this tunability, they are useable for actuators or in active vibration control applications. An extensive magnetomechanical characterization is necessary for MAE material development and requires experiments under cyclic loading in uniform but variable magnetic fields. MAE testing apparatus typically rely on fields of adjustable strength, but fixed (transverse) direction, often provided by electromagnets. In this work, two permanent magnet flux sources were developed as an add-on for a modular test stand, to allow for mechanical testing in uniform fields of variable direction. MAE specimens, based on a silicone matrix with isotropic and anisotropic carbonyl iron particle distributions, were subjected to dynamic mechanical analysis under different field and loading configurations. The magneto-induced increase of stiffness and energy dissipation was determined by the change of the hysteresis loop area and dynamic modulus values. A distinct influence of the composite microstructure and the loading state was observed. Due to the very soft and flexible matrix used for preparing the MAE samples, the material stiffness and damping behavior could be varied over a wide range via the applied field direction and intensity.

Stability and convergence analysis for different harmonic control algorithm implementations

In many engineering systems there is a common requirement to isolate the supporting foundation from low frequency periodic machinery vibration sources. In such cases the vibration is mainly transmitted at the fundamental excitation frequency and its multiple harmonics. It is well known that passive approaches have poor performance at low frequencies and for this reason a number of active control technologies have been developed. For discrete frequencies disturbance rejection Harmonic Control (HC) techniques provide excellent performance. In the general case of variable speed engines or motors, the disturbance frequency changes with time, following the rotational speed of the engine or motor. For such applications, an important requirement for the control system is to converge to the optimal solution as rapidly as possible for all variations without altering the system's stability. For a variety of applications this may be difficult to achieve, especially when the disturbance frequency is close to a resonance peak and a small value of convergence gain is usually preferred to ensure closed-loop stability. This can lead to poor vibration isolation performance and long convergence times. In this paper, the performance of two recently developed HC algorithms are compared (in terms of both closed-loop stability and speed of convergence) in a vibration control application and for the case when the disturbance frequency is close to a resonant frequency. In earlier work it has been shown that both frequency domain HC algorithms can be represented by Linear Time Invariant (LTI) feedback compensators each designed to operate at the disturbance frequency. As a result, the convergence and stability analysis can be performed using the LTI representations with any suitable method from the LTI framework. For the example mentioned above, the speed of convergence provided by each algorithm is compared by determining the locations of the dominant closed-loop poles and stability analysis is performed using the open-loop frequency responses and the Nyquist criterion. The theoretical findings are validated through simulations and experimental analysis.

Tuning the vibration of a rotor with shape memory alloy metal rubber supports

The paper describes a novel smart rotor support damper with variable stiffness made with a new multifunctional material – the shape memory alloy metal rubber (SMA-MR). SMA-MR gives high load bearing capability (yield limit up to 100MPa and stiffness exceeding 1e8N/m), high damping (loss factor between 0.15 and 0.3) and variable stiffness (variation of 2.6 times between martensite and austenite phases). The SMA-MR has been used to replace a squeeze film damper and combined with an elastic support. The mechanical performance of the smart support damper has been investigated at room and high temperatures on a rotor test rig. The vibration tuning capabilities of the SMA-MR damper have been evaluated through FEM simulations and experimental tests. The study shows the feasibility of using the SMA-MR material for potential applications of active vibration control at different temperatures in rotordynamics systems.

An electromagnetic vibration absorber with harvesting and tuning capabilities

This paper describes the development of an electromagnetic vibration absorber (EVA) with energy recovery and frequency tuning control capabilities. The essential component of the EVA is an electromagnetic transducer, interfacing between electrical and mechanical domains, connected to an external electrical circuit. So far, the use of electromagnetic devices in vibration-control applications has been driven by energy-harvesting applications. In these works, the electromagnetic transducer acts as a damper in the mechanical domain by connecting a resistance across the terminals of the device. By emulating the resistive components, some of the power that would have been dissipated in the resistor can be converted into usable power. The use of electromagnetic devices also opens the door (i) to the synthesis of more complex networks in the electrical domain, most of them impractical or too complicated to be synthesized mechanically and (ii) to the development of frequency tuning networks. We consider the possibility of using an EVA along with a resistance emulator to give a self-powered adaptive EVA. We explore the switching in of different elements across the terminals of the electromagnetic transducer in order to be able to derive new low-powered control schemes for better vibration absorption. With the underlying goal to develop high performance, energy-efficient vibration-control devices, a small scale EVA device was tested, coupled with a virtual host structure. The results presented here demonstrate the potential for self-tuning of such a device. Copyright © 2015 John Wiley & Sons, Ltd.

Performance Hierarchy of Piezoelectric Materials for Active Vibration Control Application

This article deals with selection and performance evaluation of various piezoelectric materials for active vibration control (AVC) application. Finite element method is used to assess the relative importance of materials properties (Young's Modulus (E), piezoelectric constants (e31), dielectric constant (ε), density (ρ) and Poisson's ratio (υ)) for sensor and actuator applications which are eventually used in active vibration control. Analytical hierarchy process (AHP) is finally used to assign weights to all the properties understudy. Rankings made by multiple attribute decision matrix (MADM) approach show good agreement with finite element (FE) simulation results. The numerical simulations reveals the superior performance of K0.5Na0.5NbO3-LiSbO3-CaTiO3(KNN-LS-CT (1 wt. %)) as sensor followed by KNN-LS-CT (2 wt. %) and K0.475Na0.475Li0.05 (Nb0.92Ta0.05Sb0.03) O3 (KNLNTS). For actuator, Pb [ZrxTi1−x] O3 (PZT1) demonstrates the superior performance followed by KNLNTS and KNN-LS-CT (1 wt. %). The lead-free piezoelectric materials are potential candidate to replace lead-based piezoelectric materials for active vibration control application.

A 3-D Quasi-Zero-Stiffness-Based Sensor System for Absolute Motion Measurement and Application in Active Vibration Control

A novel 3-D quasi-zero-stiffness (3DQZS) system is proposed to construct a 3-D sensor system for absolute motion measurement in vibration systems. The 3DQZS system is achieved by employing a predeformed scissor-like structure. With mathe- matical modeling and the harmonic balance method, the nonlinear dynamic response of the 3-D sensor system is deeply analyzed. It is shown that this novel 3DQZS-based sensor system is very effective and reliable in 3-D absolute motion measurement in vi- bration systems. A case study in active vibration control using the proposed 3-D sensor indicates that much better vibration control performance can be readily achieved compared with conventional methods using a similar linear feedback controller. This novel sen- sor system should provide an alternative or much better solution to many vibration control problems in various engineering practices. Index Terms—Active vibration control, nonlinear system, quasi- zero stiffness (QZS), scissor-like structure (SLS), vibration sensor.

Identification of High-Tech Motion Systems: An Active Vibration Isolation Benchmark

The benchmark Active Vibration Isolation System (AVIS) in this paper is a complex high-tech industrial system used in vibration and motion control applications. The system is complex in the sense of high order exible dynamics and multiple inputs and outputs. The aim of this benchmark is to compare difierent black box, linear time invariant system identification algorithms. Difierent large data sets are provided, enabling the use of both frequency domain and time domain identification approaches. The idea of the benchmark is to investigate both model accuracy and numerical reliability of the computational steps. Several reference solutions are provided, which demonstrate the challenging aspects of this benchmark already in the singleinput single-output case. The benchmark data and additional info are available on the website of Tom Oomen.

Frequency Response based Adaptive Vibration Control of Nonlinear Systems

The problem of active vibration control for a class of nonlinear mechanical system is addressed. A recently developed nonlinear frequency response analysis technique is utilized for the vibrational analysis and controller design. Unlike the linear case, the nonlinear system oscillations are complex, which can be observed via the nonlinear Frequency Response Function (FRF). In order to achieve a satisfactory vibration attenuation, an adaptive tuning method based on the FRF, for selecting the controller gains is proposed. The proposed algorithm performs sufficiently well for a given range of input excitation magnitudes and frequencies. A physically motivated example is given to demonstrate the application of these results. Finally, the feasibility of the proposed algorithm in a satellite vibration control application has been examined.

Negative impedance shunted electromagnetic absorber for broadband absorbing: experimental investigation

The traditional tuned mass absorber is widely employed to control the vibration of a primary structure by transferring the vibrating energy to the absorber. However, the working band of the absorber is very narrow, which limits the application of broadband vibration control. This study presents a novel broadband electromagnetic absorber by first introducing two negative impedance shunts to improve broadband damping of the absorber. The electromagnetic absorber is modeled, and the corresponding electromagnetic coupling coefficient is tested. A cantilever beam is employed to verify the broadband vibration absorption of the negative resistance (NR) shunted electromagnetic absorber (NR absorber) and the negative inductance NR shunted electromagnetic absorber (NINR absorber). The governing equations of the beam with two absorbers are derived, and the experiments are set up. The results point out that the NR and NINR absorbers can attenuate the broadband vibration. The proposed absorbers do not need the feedback system and the real-time controller compared to the active absorber; hence, they have great application potential in aerospace and in submarine applications, as well as in civil and mechanical engineering.