bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multi-Dimensional Directional Spectrograms and Campbell (ZMOD) Diagrams for Rotating Machinery
Authors: Bucher I. , Ewins D. J. , Robb D. A. , Schmiechen P. 
Published: March 2021

Abstract
A new method for decomposition of vibration signals measured on rotating machinery is presented in this paper. The method uses a signal measured from a number of sensors to decompose the spatial response according to the direction of the progression of motion, the frequency content and the various wavelengths. For the simple case of shaft vibration, two sensors, horizontal and vertical, are used to separate the vibration pattern into forward and backward progressing components. For the case of a rotating disc, more sensors are required to further decompose the response into different wavelengths. This allows one to monitor and to identify potentially dangerous vibration patterns exhibiting large backward components. The method is shown to provide better resolution in the time-frequency (speed of rotation) and spatial domains by separating several, usually overlapping patterns. Several analytical and experimental results demonstrate the usefulness of the proposed method.
Determination of Rotating Assembly Synchronous Response Characteristics Using Blade Tip-Timing Techniques
Authors: Heath Steve , Imregun Mehmet 
Published: March 2021

Abstract
This paper presents an improved analysis method for the interpretation of the vibration data measured at turbomachinery blade tips using optical laser probes. A multi-degree-of-freedom numerical simulator, which includes the structural and geometric properties of the bladed-disk assembly, the external forcing terms and the characteristics of the optical probe, has been developed to assess the reliability of the various data processing techniques to identify the natural frequencies and mode shapes of bladed-disk assemblies. It has been demonstrated that the Zablotsky-Korostelev single parameter technique, which is a de-facto standard in the aerospace industries, has inherent limitations associated with it. An improved and more rigorous method is presented for deriving the blade arrival times and a non-linear solution technique is suggested for their numerical determination. Finally, the effect of blade mistuning on the accuracy of the proposed method is also investigated.
Application of ESPI in the Vibration Analysis of Turbine Blading
Authors: Wang Robert X. , Chapman Graham M. 
Published: March 2021

Abstract
This paper reports on the application of Electronic Speckle Pattern Interferometry (ESPI) technique in vibration measurement of turbine blading. Using the time-averaged mode of ESPI, the first six modes of a turbocharger blade with airfoil profile were identified. The effect of the complicated profile of the blade was established by studying simplified model blades. Coupled modes were identified and successfully separated. Experimental results are compared with those obtained using finite element analysis.
Adaptive Virtual Autobalancing for a Magnetic Rotor With Unknown Mass Imbalance: Part II — Dynamic Balancing
Authors: Lum Kai-Yew , Bhat Sanjay P. , Bernstein Dennis S. , Coppola Vincent T. 
Published: March 2021

Abstract
In Lum et al. (1995), an adaptive control algorithm for the stabilization of a rigid, statically unbalanced rotor moving in the plane was proposed. The control strategy consisted in emulating a mechanical autobalancer using magnetic actuation so as to directly cancel the effects of static mass imbalance. In this present paper, this strategy is extended to the case of a rigid, dynamically unbalanced rotor in six degree-of-freedom motion. The state equations of the controller are based on the equations of motion of a multiple-plane autobalancer, and the control forces partially emulates the interaction between rotor and autobalancer. It is shown in simulation that the adaptive virtual autobalancing control can achieve stabilization of rotor motion as well as adaptation to changes in imbalance.
Transient Vibration of Gyroscopic Systems With Unsteady Superposed Motion
Authors: Wickert J. A. 
Published: March 2021

Abstract
The equations of motion for a gyroscopic system with unsteady superposed motion are derived for the prototypical problem in which motion of an oscillating particle is measured relative to a non-inertial frame. The resulting coefficient matrices are time-dependent, and skew-symmetric acceleration terms are present both as Coriolis acceleration and as a component of net stiffness. Such mathematical structure is also demonstrated in the context of other unsteady gyroscopic systems, including flexible media that translate with time-dependent speed. Following the asymptotic approach of Krylov, Bogoliubov and Mitropolsky, a perturbation method is developed for the case in which the superposed motion varies slowly when viewed on the time scale of the natural periods of oscillation. First-order approximations for the modal amplitude and phase are obtained in closed form. The method is illustrated through two examples of technical interest: a two degree-of-freedom model of a rotating shaft, and a distributed parameter model of a moving tape.
Generalized Characteristic Method for Orthotropic Media
Authors: Su Shigong , Su Xianzhong 
Published: March 2021

Abstract
A new method is developed to solve two dimensional transient problems of elastodynamics in orthotropic media. The real solutions of the characteristic equation for the Navier equations in orthotropic media can be analytically continued to the complex domain in which they are called generalized characteristics. The generalized characteristics are employed to prove that a set of algebraic equations of the velocity components is equivalent to the Navier equations. To illustrate how to use the present method in elastodynamics for orthotropic media, the problems of time domain Green’s functions in an unbounded medium, and Lamb’s problem for a buried concentrated line force are solved by applying the derived algebraic equations. The reflection coefficients and Snell’s law on the surface of a half-space are obtained for incident non-plane transient waves. The direct waves, reflected waves, and head wave in a half-space are analyzed directly in terms of generalized characteristics. Finally, some numerical results for the particle displacement at receivers (on and below the surface) are shown for four typical crystals and composite materials.
Shape Optimization of Unconstrained Beam and Plate Damping Layers
Authors: Lumsdaine Arnold , Scott Richard A. 
Published: March 2021

Abstract
The aim of this paper is to determine the optimum shape of a symmetric unconstrained viscoelastic damping layer for a laminated composite structure undergoing harmonic excitation. The objective is to minimize the peak displacement at the first damped natural frequency. The material loss factor is monitored to determine the improvement in performance. Beam and plate structures are examined for several boundary conditions. The common assumption of constant viscoelastic material properties is investigated by comparing optimization results for cases with constant properties to those with varying properties. ABAQUS finite element code is used to model the structures. The optimization code uses a Sequential Quadratic Programming algorithm. Results show dramatic improvement in the loss factor for optimized shapes. In addition, the use of frequency dependent viscoelastic properties is insignificant in the cases examined. Finally, results indicate that minimizing the displacement at one frequency may cause significantly worse performance at other frequencies.
Active Vibration Absorption Using Delayed Resonator With Relative Position Measurement
Authors: Olgac Nejat , Hosek Martin 
Published: March 2021

Abstract
A novel active vibration absorption technique, the Delayed Resonator, has been introduced recently as a unique way of suppressing undesired oscillations. It suggests a control force on a mass-spring-damper absorber in the form of a proportional position feedback with a time delay. Its strengths consist of extremely simple implementation of the control algorithm, total vibration suppression of the primary structure against a harmonic force excitation and full effectiveness of the absorber in a semi-infinite range of disturbance frequency, achieved by real-time tuning. All this development work was done using the absolute displacements of the absorber in the feedback. These displacement measurements may be difficult to obtain and for some applications impossible. This paper deals with a substitute and easier measurement: the relative motion of the absorber with respect to the primary structure. Theoretical foundations for the Delayed Resonator (DR) are briefly recapitulated and its implementation on a single-degree-of-freedom primary structure disturbed by a harmonic force is introduced utilizing both absolute and relative position measurement of absorber mass. Methods for stability range analysis and transient behavior are presented. Properties acquired for the same system with these two different feedback are compared. Relative position measurement case is found to be more advantageous in most applications of the Delayed Resonator method.
Digital Optimal Multivariable Control of a Smart Structure Featuring Piezoelectric Sensors and Actuators
Authors: Sannah Muhammad , Smaili Ahmad , Lahdhiri Tarek 
Published: March 2021

Abstract
In this paper, a digital regulator is designed and experimentally implemented for a smart structure featuring piezoelectric sensors and actuators using optimal multivariable control techniques. The controller consists of a linear quadratic regulator with output weightings and a state estimator, Luenberger observer. The structure is a cantilever beam synthesized with two sets of sensor/actuator PZT ceramic piezoelectric plates bonded to the beam surface at the high strain locations corresponding to the first and second vibration modes. Equations of motion of the beam are developed using finite beam element model. The model includes the mass and rigidity of the PZT ceramics. Experimental results of two regulators differing in the number of modes considered are presented and discussed. The results proved the applicability of the concept and the stability and robustness of the control algorithm.
Effects of Desired Transmissibility Functions on the Performance and Design of Control Systems for Microgravity Isolation Systems
Authors: Tsai N.-C. , Sinha A. 
Published: March 2021

Abstract
This paper examines the performance of active isolation systems for micrograviry space experiments as a function of desired transmissibilities which are chosen to be either much below or close to what can be tolerated. The control system utilizes two feedback signals: absolute acceleration and relative displacement of the mass. The controller transfer function for acceleration feedback is chosen to avoid marginally stable pole-zero cancellations. The controller transfer function for relative displacement feedback is determined to achieve the desired transmissibility function. The issue of stability and properness of this controller transfer function are addressed. The required input forces and “equivalent” closed-loop stiffness are examined for various examples of desired transmissibilities.
Chaotic Response of a Hard Duffing Type Vibration Isolator With Combined Coulomb and Viscous Damping
Authors: Leung A. Y. T. , Ravindra B. , Mallik A. K. , Chan C. W. 
Published: March 2021

Abstract
Numerical simulations of the response of a harmonically excited mass on an isolator with a cubic, hard, non-linear restoring force and combined Coulomb and viscous damping are presented. For a base-excited system, the inclusion of a Coulomb damper with a suitable break-loose frequency can suppress the secondary resonances and chaotic motion. However, for a force-excited system, the introduction of Coulomb damping does not alter the bifurcation structure. Transmissibility indices have been defined for the solution obtained by numerical integration and the role of the subharmonic resonances and chaotic motion on the performance of the system is pointed out.
Energy Flow Control of Interconnected Structures: I — Modal Subsystems
Authors: Kishimoto Yasuo , Bernstein Dennis S. , Hall Steven R. 
Published: March 2021

Abstract
Dissipative energy flow controllers are designed for inter-connected modal subsystems. Active feedback controllers for vibration suppression are then viewed as either an additional subsystem or a dissipative coupling. These controllers, which are designed by the LQG positive real control approach, maximize energy flow from a specified modal subsystem.
Spherical Compliant Model for Vibration Estimation and Control
Authors: Thompson Thomas J. 
Published: March 2021

Abstract
Proposed space missions involve large structures which must maintain precise dimensional tolerances during dynamic maneuvers. In order to attenuate disturbances in the many modes of vibration of such structures, active and passive vibration control has been proposed. Passive control is to be achieved by placing viscous or viscoelastic members in a structure to absorb energy, while active control similarly could involve structural members (struts) capable of sensing axial displacement and exerting axial control force.
With conventional modal analysis, the effect of a control element on a system is computed by summing its influence on many immutable modes. Since changes in mode shape must be described by this summation, truncation of higher modes results in inaccuracies.
The compliant model of vibration to be presented accurately accounts for the effects of locally-acting control elements without inclusion of high-frequency modes. The motion of each spring-mass system representing a structural mode is modified by a control element in series with another stiffness inherent to the structure for that mode and control position. In order to predict the influence of several control elements or dampers on closely-spaced modes, the compliant models for those modes are integrated into a spherical model in which one lumped mass is acted upon by orthogonal modal stiffnesses. In the spherical model, control elements influent the lumped mass from orientations determined by mode participation factors. The resulting equations of motion are stated in standard state-space form.
To test accuracy, the compliant model is used to predict eigenvalue shifts due to springs and dampers acting upon an axially-vibrating rod, and the spherical model is used to predict damping accurately in a lumped-mass system with closely-spaced modes.
Hybrid Vibration Control of a Cable-Stayed Bridge
Authors: Bell Mark , Shoureshi Rahmat A. 
Published: March 2021

Abstract
Hybrid vibration control, involving the combined use of feedforward and feedback control, is developed for a cable-stayed bridge using passivity-based control. The control objective is to reject all disturbances that cause unwanted motion in the bridge structure, namely seismic activity, wave loading and wind loading, while keeping energy consumption at a very low level. An experimental bridge prototype has been developed and simulations involving an analytical model derived from real data are presented. A three dimensional finite element model was developed of the bridge for verification purposes. A multiple time step ahead estimator is also developed using neural networks that is used in the feedforward loop to predict future bridge motion using past values of disturbance and output. Simulation results of the neural estimator are presented.
Tuning of a Rear Electronic Control Engine Mount
Authors: Galvin Daniel D. 
Published: March 2021

Abstract
This paper refers to mathematical tuning, by the sinusoidal steady-state transfer function method, of an adjustable hydraulic rear engine mount for reduction of perceived vibration during engine idle situations. The problem being addressed, in particular, is the reduction of “idle shake”. The accuracy of this method is confirmed by individual component testing along with in situ vibration measurements.
During this work, a general approach to transfer function calculation is given by evaluating the system components with the linear-graph system of modeling. This is complemented by component verification and curve-fitting to arrive at the final transfer function which reveals the inherent tendencies of the overall system. Secondary measurements are then employed to rectify the contradiction between mathematical values and subjective results.
Development of V-Shaped Hybrid Mass Damper and its Application to High-Rise Buildings
Authors: Imazeki Masanori , Tanida Koji , Mutaguchi Masao , Koike Yuji , Murata Tamotsu , Kobori Takuji , Yamada Tosikazu , Tagami Jun , Sasaki Katsuyasu , Ohrui Satoshi 
Published: March 2021

Abstract
A hybrid mass damper system has been developed with a view to counteracting wind- and earthquake-excited vibrations of large high-rise building structures. In order to eliminate the large space needed to accommodate a pendulum-type mass damper adapted to the long period of high-rise building, mechanism has been devised for suspending the auxiliary mass on a V-shaped rail sliding on rollers. The base angle of the V-shaped rail is varied for adjusting the natural period of the mass damper system. A suboptimal algorithm based on the minimum norm method has been adopted for designing the auxiliary mass driving system. Three units of this damper system, each equipped with auxiliary mass weighing 110 tons, have been installed on a 52-story building. Satisfactory performance conforming in all practical aspects with design has been verified from vibration test on actual building after installation. As sequel, the functioning of the system during the first year of service is also reported.
Hydraulic Actuator Tuning in the Control of a Rotating Flexible Beam Mechanism
Authors: Panza Michael J. , Mayne Roger W. 
Published: March 2021

Abstract
The end point position and vibration control of a rotating flexible beam mechanism driven by a hydraulic cylinder actuator is considered. An integrated nonlinear system model comprised of beam dynamics, hydraulic actuator, control valves, and control scheme is presented. Control based on simple position feedback along with a hydraulic actuation system tuned to suppress beam vibration over a wide range of angular motion is investigated. For positioning to small to moderate mechanism angles, a linear system model with the actuator tuned for good open loop performance is developed. Actuator tuning is accomplished by varying the system hydraulic resistance according to a dimensionless parameter defining the interaction between the actuator and flexible beam. Simulation results for a closed loop system indicate that this simple tuned control provides comparable performance and requires less control effort than an untuned system with a more complex state feedback optimal controller. To compensate for geometric nonlinearities that cause instability when positioning to large mechanism angles, an active actuator tuning scheme based on continuous variation of hydraulic resistance is proposed. The active variable resistance controller is combined with simple position feedback and designed to provide a constant dimensionless actuator-flexible beam interaction parameter throughout the motion. Simulation results are presented to show the stabilizing effect of this control strategy.
Hybrid Feedback-Feedforward Control for Vibration Suppression
Authors: De Man P. , Preumont A. 
Published: March 2021

Abstract
This paper evaluates a hybrid feedback-feedforward controller for vibration suppression. The feedback controller uses colocated actuator and sensor and a fixed compensator with guaranteed stability. The feedforward controller uses the same actuator as the feedback one. The x-filtered LMS algorithm is used to adapt the FIR filter coefficients. For the application considered in this paper, the hybrid controller enjoys the advantages of both types of controllers.
A Design Method of Robust Controller for a Flexible Structure Using H∞/μ Control Theory
Authors: Watanabe Toru , Yoshida Kazuo 
Published: March 2021

Abstract
This paper discusses about robust vibration control of a flexible structure that has transverse and torsional vibration modes. A design method of a controller taking account of the parameter variations and the residual dynamics is presented. The transverse-torsional coupling is translated into parameter variations, and other model errors of structural dynamics of the system are interpreted as frequency-shaped weighting functions. The H∞/μ control theory is applied to synthesize controller and these perturbations are formulated in the generalized plant. To examine the capability of the obtained controller, computer simulations and control experiments are carried out and the effectiveness of the presented method is verified.
Vibration Control Using Combined Independent Modal Space Control and Fuzzy Logic
Authors: Asdigha Mehran , Greif Robert 
Published: March 2021

Abstract
Independent Modal Space Control (IMSC) is an established technique in active suppression of vibrations, in which the control law is developed exclusively in the modal space, allowing for independent design of the modal control forces. These forces can be transformed to the physical domain through modal transformation. The resulting controller is fixed-gain, with the active damping introduced to the system determined independently for each mode and is a function of the velocity for the under-damped case. In this work we propose to modify IMSC using fuzzy reasoning. The result is a new non-linear control law, embedding fuzzy reasoning and an implicit fuzzy rule-base that transforms the traditional algorithm from a fixed-gain to a variable-gain controller. The algorithm uses information about the displacement profile across the sensed locations to distribute the active damping rationally among the modal controllers. This new algorithm complements the “local” view of the traditional algorithm in the modal space, with a “global” view of the displacements in the physical space. The results show significant improvement in the settling time as the performance criterion.
Experimental Verification of Time-Varying Impulse Shaping for a Two-Link Flexible Manipulator
Authors: Cho Jung-Keun , Park Youn-sik 
Published: March 2021

Abstract
Input shaping is a method to reduce the motion-induced vibration in a flexible system. A kind of input shaping method (time-varying impulse shaping) has been proposed previously which is applicable to vibration reduction of time-varying systems. This paper presents experimental results of time-varying impulse shaping with a two-link flexible manipulator. The flexible manipulator has two revolute joints and moves on a vertical plane under gravity. A dynamic model was developed to provide a basis for the shaping, and the model was proved through some experiments. The reference trajectories commanded to the system are shaped by using the suggested time-varying impulse shaping. Implemented to the two-link flexible manipulator, test results demonstrate that the link vibration can be greatly suppressed during and after a point-to-point motion, and the residual vibration reduction was observed more than 90% with this shaping.