bluuebunny/crossref_metadata_2025_split huggingface dataset:
Control of Parametrically Excited Systems via Time-Invariant Methods
Authors: Joseph Paul , Sinha S. C. 
Published: March 2021

Abstract
A new technique in the design of controllers for linear dynamic systems with periodically varying coefficients is presented. The idea is to utilize the well known Liapunov-Floquet (L-F) transformation such that the original time-varying system can be reduced to a form suitable for the application of standard time-invariant methods of control theory. For this purpose, a procedure for computing the L-F transformation matrices for general linear periodic systems is outlined. In this procedure the state transition matrices are expressed in terms of Chebyshev polynomials which permits the computation of L-F transformation matrices as explicit functions of time. Further, it is shown that controllers can be designed in the transformed domain via full state or observer based feedback using principles of root locus, pole placement and/or optimal control theory. The effectiveness of the proposed technique is demonstrated through three examples. The first example is a single mass inverted pendulum while in the second example a triple inverted pendulum subjected to a periodic follower load is considered. The third example chosen is a simply supported smart Euler-Bernoulli elastic column subjected to a periodic loading. It is found that time-invariant techniques can be employed effectively to achieve vibration control of parametrically excited linear systems.
Stable and Unstable Quasiperiodic Oscillations in Robot Dynamics
Authors: Stépán G. , Haller G. 
Published: March 2021

Abstract
Delays in robot control may result in unexpectedly sophisticated nonlinear dynamical behavior. Experiments on force controlled robots frequently show periodic and quasiperiodic oscillations which cannot be explained without including the time lag and/or the sampling time of the system in our models. Delayed systems, even of low degree of freedom, can produce phenomena which are already well understood in the theory of nonlinear dynamical systems but hardly ever occur in simple mechanical models. To illustrate this, we analyze the delayed positioning of a single degree of freedom robot arm. The analytical results show typical nonlinear behavior in the system which may go through a codimension two Hopf bifurcation for an infinite set of parameter values, leading to the creation of two-tori in the phase space. These results give a qualitative explanation for the existence of self-excited quasiperiodic oscillations in the dynamics of force controlled robots.
Non-Stationary Vibrations of Rotor Systems With Non-Symmetric Clearances
Authors: Ganesan R. , Sankar T. S. 
Published: March 2021

Abstract
The investigation considers the behaviour of rotor-dynamic systems subjected to non-symmetric clearance effects based on a Jeffcott rotor model. Only the undamped case is treated. Free nonlinear vibrations as well as resonant oscillations are analyzed using the method of multiple scales. Particular attention is paid to the “normal-loose” rubbing condition due to the bearing clearance effects and a discontinuous radial stiffness model is employed to analytically model this problem. General expressions for the amplitude and phase modulating functions characterizing the non-stationary oscillations of orthogonal components of the displacement vector are obtained. Further, an associated stability analysis is performed for the nonlinear steady state rotor motions by considering the singular points. A numerical study encompassing the different effects of the system parameters is also presented.
Computing the Number of Fixed Joints on Poincare Map in Nonlinear Mathieu Equation
Authors: Fujisaka Hisato , Sato Chikara 
Published: March 2021

Abstract
A numerical method is presented to compute the number of fixed points of Poincare maps in ordinary differential equations including time varying equations. The method’s fundamental is to construct a map whose topological degree equals to the number of fixed points of a Poincare map on a given domain of Poincare section. Consequently, the computation procedure is simply computing the topological degree of the map. The combined use of this method and Newton’s iteration gives the locations of all the fixed points in the domain.
Application of Preview Control to Contour-Following Using a Force-Controlled Industrial Robot
Authors: Yong Boojoong , Starr Gregory P. 
Published: March 2021

Abstract
It is often useful in automation tasks to make a robot manipulator follow along a workpiece surface while maintaining contact. With a typical position-controlled industrial robot, the contact force must be sensed and used to control the robot. The tracking speed and force regulation of this type of system can be improved using preview control, that is, the use of measured surface position information a fixed distance ahead of the point of contact.
To realize preview control, a discrete-time state-space model of the robot and environment was identified. A wrist force sensor provides a measurement of the contact force. The complete controller consists of both feedback and feedforward preview controllers. Stability is determined solely by the feedback controller. A Kalman filter was used to produce optimal state estimates. Experimental evaluation of the surface-following system using preview control showed substantial improvement when compared to a linear controller.
Flexibility Effects in a Single Link Robotic Manipulator
Authors: Nataraj C. 
Published: March 2021

Abstract
A single link robotic manipulator is modeled as a rotating flexible beam with a rigid mass at the tip and accurate energy expressions are derived. The resulting partial differential equations are solved using an approximate method of weighted residuals. From the solutions, coupling between axial and flexural deformations and the interactions with rigid body motions are rigorously analyzed.
The emphasis in the current paper is not on an exhaustive analysis of existing systems but it is rather intended to compare and highlight the various flexibility effects in a relatively simple system. Hence, a nondimensional parametric analysis is performed to determine the effect of several parameters (including the rotating speed) on the errors and the individual interaction effects are discussed. Comparison with previous work in the field shows important phenomena often ignored or buried in large scale numerical analyses. Future work including application to multi-link robots is outlined.
A “Smart” Electrorheological Fluid Dynamic Vibration Absorber
Authors: Dimarogonas Andrew D. , Kollias Alexander 
Published: March 2021

Abstract
As “smart” are characterized materials which have properties that can be changed in real time by a way of an external control action. Electrorheological (ER-) fluids are such materials since their apparent viscosity can be altered substantially under a controllable electric field. ER-fluids consist of a dispersion of fine dielectric powder, usually strongly hydrophile, into a fluid lubricant.
An ER-fluid is used to fill the gap between two parallel sets of circular, concentric plates assembling the “smart” vibration dynamic absorber as part of a rotor system. One set of plates is resiliently connected to a rotor but the other is rigidly attached to it. The effect of the ER-fluid activation by an external electric field on the relative motion of the plates results in a controllable damping force of viscous and friction type.
Numerical simulations of the rotor vibrations are carried out for a range of speeds including resonance and for several electric field levels. Increasing the electric field in the absorber yields in rotor amplitude reduction up to a threshold electric field which sticks the plates. Substantial improvement in the absorber efficacy is obtained by active control of the electric field using a feedback control scheme which optimizes the electric field input for maximum energy dissipation.
Forced Harmonic Response of a Continuous System Displaying Eigenvalue Veering Phenomena
Authors: Ginsberg Jerry H. , Pham Hoang 
Published: March 2021

Abstract
Prior studies of self-adjoint linear vibratory systems have extensively explored the phenomenon of veering of eigenvalue loci that depict the dependence of natural frequencies on a system parameter. The present work is an exploration of the effect of such phenomena on the response of a continuum to harmonic excitation. The focus of the analysis is the prototypical system of a two-span beam with a strong torsional spring at the intermediate pin support. The results of an exact eigenvalue analysis, not previously disclosed, are used to perform a modal analysis of the steady-state response of the beam to a harmonic concentrated force applied to the middle of one span. The analysis is used to identify situations in which the forced response is localized to one span, as well as the degree to which the location and magnitude of the peak displacement displays parameter sensitivity.
On the Free Vibration of Mono-Coupled Periodic Distributed Parameter Systems
Authors: Lueschen Gerhard G. G. , Bergman Lawrence A. 
Published: March 2021

Abstract
A new approach to the exact solution is given for the free vibration of a periodic structure comprised of a multiplicity of identical linear distributed parameter substructures, closely coupled through identical linear springs. The method used is an extension of a classical result for periodic discrete systems.
Commissioning of a High Speed Composite Rotor With Hydrostatic Dampers and Ceramic Rolling Element Bearings
Authors: Headifen Ross N. , Fuller Robert L. , Kitzmiller Jon R. 
Published: March 2021

Abstract
A high speed (25,000 rpm) routing machine with a 300 lb rotor was designed and manufactured. To accommodate the high shaft speed, 2.6 million DN, rolling element bearings were used with ceramic balls and inner races. In order to control the magnitude of the vibration, damping was incorporated into the system using nonrotating hydrostatic dampers. The journal for the dampers was a cylindrical cartridge that had the rolling element bearings clamped inside of it. Extensive analysis was performed on this system. A computer program was written that could model the orbit path of the lumped mass shaft in the damper over the full speed range. A second program was also written that calculated the damper nonlinear stiffness and damping coefficients, and incorporated them in with a one-dimensional beam, finite element rotordynamics model of the system. Analysis results are presented along with experimental run data from the machine. Balancing problems encountered during commissioning have limited the results to 16,500 rpm to date. The last of which is currently being remedied.
Predicting the Vibrations of a Spinning Inflated Membrane
Authors: Segalman Daniel J. , Slavin Adam M. 
Published: March 2021

Abstract
The dynamics of flexible bodies spinning at rates near or above their first natural frequencies is a notoriously difficult area of analysis. Recently, a method of analysis, tentatively referred to as a method of quadratic modes, has been developed to address this sort of problem. This method restricts consideration to configurations in which all kinematic constraints are automatically satisfied through second order in deformation. Besides providing robustness, this analysis method reduces the problem from one that would otherwise require the reformulation of stiffness matrices at each time step to one of solving only a small number of nonlinear equations at each time step. A test of this method has been performed, examining the vibrations of a rotating, inflated membrane.
Dynamic Characteristics of TEHD Tilt Pad Journal Bearing Simulation Including Multiple Mode Pad Flexibility Model
Authors: Kim Jinsang , Palazzolo Alan 
Published: March 2021

Abstract
An approach for incorporating the heat transfer and elastic deformation effects into dynamic coefficient calculation is presented. A global analysis method is used, which finds the equilibrium pad tilt angles at each eccentricity position and includes cross-film variable viscosity, heat transfer effects in the lubricant, elastic deformation, heat conduction effects in the pads, and elastic deformation effect in the pivots. Deflection modes are used to approximate deformation of the top surface of the pads. The dynamic coefficients of a single pad are calculated at the equilibrium state of the bearing, based on numerical perturbation with respect to the bearing degrees of freedom. These include journal position, pad rotation, pivot deformation, and modal coordinates. The stiffness and damping coefficients are calculated and show very good agreement with experimental and numerical results from the existing literature.
Analysis of Self-Excited Longitudinal Vibration of a Moving Tape
Authors: Wickert Jonathan A. 
Published: March 2021

Abstract
Longitudinal vibration of a moving magnetic tape can be excited by frictional contact with a recording head, or with a guide that defines the path of the tape. The friction force depends on the velocity, relative to a stationary observer, of the tape element that is instantaneously located at the point of contact. The response of a moving tape under such nonlinear dissipation is determined using new methods for the vibration analysis of axially-moving materials. In a particular transport speed range, longitudinal motion of the tape is self-excited through negative (unstable) damping for small amplitude vibration and positive (stable) damping for large amplitudes. Independent of the initial conditions, almost all solutions are attracted to a stable limit cycle, the amplitude of which is sensitive to the transport speed and to the axial location of contact. Parameter combinations that reduce, or eliminate altogether, the self-excited motion are identified. Some of the conclusions differ from those of previous analyses that neglect the effects of convection on the tape’s velocity and acceleration.
A Discussion of Objective Functions in Structure-Control Simultaneous Optimum Design
Authors: Iwatsubo Takuzo , Kawamura Shozo , Adachi Kazuhiko 
Published: March 2021

Abstract
The effect of the objective functions on the results of the structure-control simultaneous optimum design is discussed, comparing the optimum designs obtained by minimizing several different types of objective functions. These objective functions are defined as a linear combination of the structural and the control objective functions. One of the objective functions is a structural weight, another is a feedback gain norm and the others are transient characteristics values which are expressed as the quadratic form. A flexible cantilever beam is designed in the numerical example, and the results indicate that the usefulness of the structure-control simultaneous optimum design depends on the objective function for the example.
Active Vibration Control of Flexible Space Structures by Using Piezoelectric Sensors and Actuators
Authors: Agrawal Brij N. , Bang Hyochoong 
Published: March 2021

Abstract
The application of piezoelectric actuators and sensors in the vibration suppression of flexible structures is demonstrated experimentally. Navy Type II piezoceramic wafers were bonded at the base of a flexible arm to increase damping of its first structural mode at at 0.138 Hz. A Positive Position Feedback (PPF) analog compensator was used for active vibration control. The damping of the first mode was increased from 0.3% to 1.5 % by using the active control.
A Method for State Observer Design in Bilinear Suspension Systems
Authors: Mahajan Sanjay K. , Krishnan Shriram 
Published: March 2021

Abstract
This paper presents a simple technique of designing state observers for bilinear suspension models. A 2-DOF quarter-car automotive suspension is considered. The technique produces observer gains which dynamically depend on the control, and are obtained through observer pole placement in a time-varying system that uses Liapunov transformation. It is shown that the proposed use of this method could be effective in the design of modulated suspension systems, with certain limitations on the control law that is used.
Dynamic Interaction in a Slewing Motor-Beam System: Closed Loop Control
Authors: Sah J. J. , Lin J. S. , Crassidis Agamemnon L. , Mayne Roger W. 
Published: March 2021

Abstract
This paper considers the dynamic interaction between a DC motor and its slewing beam load. The system is described in terms of dimensionless parameters which generalize the results and define the tendency for interaction between the motor and beam. The study focuses on the performance and behavior of the system under closed-loop control. Motor-beam arrangements with differing amounts of dynamic interaction are defined by simple adjustments in gear ratio for a specified motor and beam. Each of these systems is controlled with full state feedback and various forms of output feedback. Controller performance is optimized in each case and the systems are compared to evaluate the effect of motor-beam interaction on the closed-loop system behavior. Systems with an appropriate amount of motor-beam interaction tend to be easier to control and require modest amounts of actuation effort. Systems with little motor-beam interaction are especially prone to beam vibrations and require feedback of beam motions for good closed-loop performance. Those systems with excessive interaction require stabilization efforts to obtain good transient performance and tend to consume increased levels of actuation energy.
Putting Statistics Into the Statistical Energy Analysis of Automotive Vehicles
Authors: Radcliffe Clark J. , Huang Xian Li 
Published: March 2021

Abstract
Sound and vibration transmission modeling methods are important to the design process for high quality automotive vehicles. Statistical Energy Analysis (SEA) is an emerging design tool for the automotive industry that was initially developed in the 1960’s to estimate root-mean-square sound and vibration levels in structures and interior spaces. Although developed to estimate statistical mean values, automotive design application of SEA needs the additional ability to predict statistical variances of the predicted mean values of sound and vibration. This analytical ability would allow analysis of vehicle sound and vibration response sensitivity to changes in vehicle design specifications and their statistical distributions.
This paper will present an algorithm to extend the design application of the SEA method through prediction of the variances of RMS responses of vibro-acoustic automobile structures and interior spaces from variances in SEA automotive model physical parameters. The variance analysis is applied to both a simple, complete illustrative example and a more complex automotive vehicle example. Example variance results are verified through comparison with a Monte Carlo test of 2,000 SEA responses whose physical parameters were given Gaussian distributions with means at design values. Analytical predictions of the response statistics agree with the statistics generated by the Monte Carlo method but only require about 1/300 of the computational effort.
Rotational Response and Slip Prediction of Serpentine Belt Drive Systems
Authors: Hwang S. J. , Perkins N. C. , Ulsoy A. G. , Meckstroth R. J. 
Published: March 2021

Abstract
A nonlinear model is developed which describes the rotational response of automotive serpentine belt drive systems. Serpentine drives utilize a single (long) belt to drive all engine accessories from the crankshaft. An equilibrium analysis leads to a closed-form procedure for determining steady-state tensions in each, belt span. The equations of motion are linearized about the equilibrium state and rotational mode vibration characteristics are determined from the eigenvalue problem governing free response. Numerical solutions of the nonlinear equations of motion indicate that, under certain engine operating conditions, the dynamic tension fluctuations may be sufficient to cause the belt to slip on particular accessory pulleys. Experimental measurements of dynamic response are in good agreement with theoretical results and confirm theoretical predictions of system vibration, tension fluctuations, and slip.
A Numerical Approach for the Prediction and Reduction of Structure-Borne Noise During the Design Stage of Ground Vehicles
Authors: Viahopoulos Nickolas , Shalis Edward V. , Latcha Michael A. 
Published: March 2021

Abstract
During the design stage of ground vehicles it is important to reduce the noise emitted from structural components. In commercial applications the reduction of the interior noise for passenger comfort is a concern with increased significance. In military applications noise radiated from the exterior of the vehicle is of primary importance for the survivability of the vehicle. Numerical acoustic prediction software can be used during the design stage to predict and reduce the radiated noise. Two formulations, the Rayleigh integral equation1 and the direct boundary element method2,3 were implemented into software for acoustic prediction. The developed code can accept information from a finite element model with a known input forcing function. Specifically, the predicted velocities on the structural surfaces can be used as input to the acoustic code for predicting the noise emitted from a vibrating structure. Computation of acoustic sensitivities4 was also implemented in the code. This information can identify the portions of the boundary that effect the radiated noise most, and it can be used in an optimization process to reduce the noise radiated from a vibrating structure.
Comparison of Finite Element Models for Predicting Structural Vibration
Authors: Sung Shung H. , Fannin Michael P. , Nefske Donald J. , Chen Francis H. K. 
Published: March 2021

Abstract
Three structural finite-element models of a small aluminum box with moderately thick walls, representative of a powertrain casting structure, are assessed by comparisons with measured vibration data. The finite element models are: (1) a plate element model, (2) a solid element model, and (3) a hybrid model consisting of plate, beam, and rigid elements. Both lumped- and consistent-mass formulations are evaluated. Comparisons are made with the measured velocity vibration response to shaker excitation. The consistent-mass plate model and the lumped-mass solid model are found to be comparable in accuracy, while the hybrid model can be tuned to achieve the greatest accuracy by matching the measured mode frequencies. The study illustrates the difficulty in accurately predicting the narrow-band vibration response of even a relatively simple structure. However, it is shown that all three models predict a similar one-third octave-band response, which is a vibration measure commonly used in practice.
Vibration of an Eccentrically Clamped Annular Plate
Authors: Tseng Jung-Ge , Wickert Jonathan A. 
Published: March 2021

Abstract
Small amplitude vibration of an eccentric annular plate, which is free along its outer edge and clamped along the interior, is investigated through experimental and analytical methods. A disk with this geometry, or a stacked array in which the clamping and symmetry axes of each disk are nominally coincident, is common in data storage and brake systems applications. In the present case, the geometric imperfections on the boundary can have important implications for the disk’s dynamic response. Changes that occur in the natural frequency spectrum, the mode shapes, and the free response under eccentric mounting are studied through laboratory measurements and an approximate discrete model of the plate. The natural frequencies and modes are found through global discretization of the Kamke quotient for a classical thin plate. For the axisymmetric geometry, the natural frequencies of the “sine” and “cosine” vibration modes for a specified number of nodal diameters are repeated. With increasing eccentricity, on the other hand, each pair of repeated frequencies splits at a rate that depends on the number of nodal diameters. Over a range of clamping and eccentricity ratios, the model’s predictions are compared to the measured results.