bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamic Modeling of a Non-Redundant Spatial Mobile Manipulator
Authors: Stiles James M. , Chung Jae H. , Velinsky Steven A. 
Published: November 2020

Abstract
Mobile manipulators are comprised of robot manipulators mounted upon mobile platforms which allow for both high mobility and dexterous manipulation ability. Although much research has been performed in the area of motion control of mobile manipulators, previous developed models are typically simplified and assume only planar motion and/or holonomic constraints. In this work, the equations of motion of a three dimensional non-redundant wheeled-vehicle based mobile manipulator system are developed using a Newton-Euler formulation. This model incorporates a complex tire model which accounts for tire slip and is thus applicable to high speed and high load applications. The model is systematically exercised to examine the dynamic interaction effects between the mobile platform and the robot manipulator, to illustrate the effects of wheel slip on system performance, and to establish bounds on the efficacy of the simplified existing kinematic models.
Nonlinear Behavior of an Inclined Cable: Experimental and Analytical Investigations
Authors: Berlioz A. , Lamarque C. H. , Malasoma J.-M. 
Published: November 2020

Abstract
Vibrations of an inclined cable subjected to external sinusoidal excitation are experimentally investigated and via a simplified model with one degree-of-freedom: external excitation looks like the loading that should be exerted on the cable by the superstructure of a bridge. The nonlinear one dof model is studied via the multiple scales method. Numerical and experimental results are compared.
An Analytical Approach to Model Disc Brake System for Squeal Prediction
Authors: Chowdhary Harsh V. , Bajaj Anil K. , Krousgrill Charles M. 
Published: November 2020

Abstract
The squeal noise arising due to friction-induced vibrations in brakes continues to be a major challenge for automotive manufacturers. To predict one of the mechanisms behind disc brake squeal, an analytical model is developed for the disc brake system. The brake rotor is represented by a thin plate of equivalent modal characteristics and the backing plates are modeled as thin annular sector plates using Rayleigh-Ritz approach. The two structural models are then coupled using linear elastic springs and Coulomb friction at the interface, and Lagrangian approach is used to derive the equations of motion of the coupled system. The resulting linear equations are solved by using complex eigenvalue analysis. The study shows that squeal is a flutter-type instability caused by coupling between the modes of structural components with very close natural frequencies. The sensitivity to friction material stiffness and the influence of hydraulic cylinder stiffness at backing plates are also discussed.
Out-of-Plane Vibrations of a Stepped Euler-Bernoulli Beam Clamped to a Rotating Hub
Authors: Naguleswaran S. 
Published: November 2020

Abstract
This paper is concerned with the vibrations of an Euler-Bernoulli stepped cantilever, clamped to a hub rotating at a constant speed. The system parameters are: the speed of rotation of the hub, the position of the step, the ratio of the mass per unit length of the two portions of the beam and the ratio of the flexural rigidity. Analytical solution of the mode shape differential equations for out-of-plane vibrations (normal to the plane of rotation) is developed. The frequency equation is expressed as a 4th order determinant equated to zero. A scheme is presented to derive the natural frequencies. The first three frequencies are tabulated for various combinations of the system parameters. Published results (which were obtained via finite element procedure) are compared with the analytical results.
Analysis of Degenerate Bifurcation in Machining Using a Nonlinear Model
Authors: Fofana M. S. , Bukkapatnam Satish 
Published: November 2020

Abstract
We present a two degrees of freedom model of machining dynamics that compactly captures the nonlinear effects of regeneration, tool wear and plowing under orthogonal machining. Extensive simulation experiments show that the solutions to the governing equations of the model bear distinct similarities to signals from our earlier experiments, as reflected by both visual state portraits as well as the values of the quantifiers of a steady state dynamic system. Governing equations of the model lead to nonlinear delay differential equations, which we reduce to ordinary differential equations using Hopf bifurcation theorem and centre manifold theorem. Despite the ongoing efforts by the authors of this paper to quantify the simulations results analytically and experimentally, we strongly believe that our proposed model will be found to be amenable for studying and analyzing bifurcations that can lead to chatter in machining.
Twinkling Phenomena in Snap-Through Oscillators
Authors: Feeny Brian F. , Diaz Alejandro R. 
Published: November 2020

Abstract
Oscillatory behavior in a chain of masses connected by continuous, non-monotonic stiffness (snap-through) elements can be induced under quasi-static loading. Insight into the birth of this behavior is obtained from a single mass system. A bifurcation study shows the potential for equilibrium jumps between multiple equilibria. As such, the transients occurring under quasi-static loading do not converge to the static loading case.
Unified Approach for Noisy Nonlinear Mathieu-Type Systems
Authors: Namachchivaya N. Sri , Sowers Richard B. , Van Roessel H. J. 
Published: November 2020

Abstract
The purpose of this work is to develop a unified approach to study the dynamics of a single degree of freedom system excited by both periodic and random perturbations. We consider the noisy Duffing-van der Pol-Mathieu equation as a prototypical single degree of freedom system and achieve a reduction by developing rigorous methods to replace, in some limiting regime, the original complicated system by a simpler, constructive, and rational approximation — a low-dimensional model of the dynamical system. To this end, we study the equations as a random perturbation of a two-dimensional weakly dissipative time-periodic Hamiltonian system. We achieve the model-reduction through stochastic averaging and the reduced Markov process takes its values on a graph with certain glueing conditions at the vertex of the graph. Examination of the reduced Markov process on the graph yields many important results, namely, mean exit times, probability density functions, and stochastic bifurcations.
Nonplanar Motion of a String due to Two-Frequency Excitation
Authors: Yasuda Kimihiko , Kamiya Keisuke 
Published: November 2020

Abstract
It is known that, under certain conditions, a stretched string subjected to a planar harmonic excitation executes nonplanar motions due to the instability of the palanar motion. In recent years, studies on bifurcations of such nonplanar motions to amplitude modulated quasiperiodic motions and chaotic motions have been reported. However no literatures on the problem of nonplanar motions due to a multi-frequency excitation are found.
In this paper, the possibility of nonplanar motions in a string due to a two-frequency excitation is studied. For this purpose two cases are considered, i.e. one in which both components of the excitation are in a plane, and one in which they are perpendicular to each other. In both cases the sum of the frequencies of the components is supposed to near to twice one of the natural frequencies of the string. Theoretical analysis using the perturbation method of multiple scales and numerical simulation are carried out to show that nonplanar motions occur.
Control of Rotary Cranes Using Fuzzy Logic
Authors: Al-mousa Amjed A. , Nayfeh Ali H. , Kachroo Pushkin 
Published: November 2020

Abstract
Rotary cranes (tower cranes) are common industrial structures that are used in building construction, factories, and harbors. These cranes are usually operated manually. With the size of these cranes becoming larger and the motion expected to be faster, the process of controlling them became difficult without using automatic control methods. In general, the movement of cranes has no prescribed path. Cranes have to be run under different operating conditions, which makes closed-loop control preferable.
In this work a fuzzy logic controller is introduced with the idea of split-horizon; that is, fuzzy inference engines (FIE) are used for tracking the position and others are used for damping the load oscillations. The controller consists of two independent controllers: radial and rotational. Each of these controllers has two fuzzy inference engines (FTEs). Computer simulations are used to verify the performance of the controller. Three simulation cases are introduced: radial, compound, and damping. The results from the simulations show that the fuzzy controller is capable of keeping the load-oscillation angles small throughout the maneuvers while completing them in a relatively reasonable time.
Optimal Control of Homoclinic Bifurcation in a Periodically Driven Helmholtz Oscillator
Authors: Lenci Stefano , Rega Giuseppe 
Published: November 2020

Abstract
The problem of avoiding the homoclinic bifurcation of the hilltop saddle of the Helmholtz equation by a shrewd choice of the shape of the external excitation is considered. The distance between the perturbed manifolds is computed by means of the Melnikov’s method, and its dependence on the shape of the excitation is emphasized. Successively, it is shown how it is possible to determine a theoretical optimal excitation which maximizes the distance between stable and unstable manifolds for a fixed excitation amplitude or, equivalently, which maximizes the critical amplitude for homoclinic bifurcation.
The practical case of a finite number of subharmonics is considered in detail. The corresponding optimal problems are solved numerically and the related optimal excitations are given. It is shown that when the number of subharmonics increases, the critical threshold for homoclinic bifurcation tends to double with respect to the reference case of harmonic excitation. Some numerical simulations are finally performed to verify the theoretical predictions and the effectiveness of the control procedure.
Control of an Elasto-Plastic Pendulum
Authors: Gerstmayr Johannes , Irschik Hans 
Published: November 2020

Abstract
An elasto-plastic pendulum performing large rigid-body rotations and vibrating in the small-strain regime is studied. Spatial distribution of plastic zones within the beam-type pendulum is taken into account. The problem is described by a differential algebraic system of equations for the flexural coordinates and the rotation of the pendulum. This system of equations can be interpreted as a model for an elastic background pendulum under the action of additional sources, formed by the plastic parts of strain. Since the elastic pendulum is a Hamiltonian system, it is possible to control the motion of the elastic pendulum by means of a collocated PD-controller. Especially, we consider the problem of bringing the tip of the elastic pendulum into its upward (inverted) position by means of a control moment acting at the fixed end. We then apply the controller designed for the elastic pendulum to the elasto-plastic model, assuming that the yield level of the material was lowered considerably by some environmental influences. Since the effect of plasticity is dissipative, the controlled elasto-plastic pendulum turns out to reach an equilibrium position, which however does not exactly coincide with the upward target position. This deviation is due to the permanent deformations induced in the pendulum by plasticity, and it is demonstrated in a numerical study.
Application of a Sliding Mode Observer for Dynamic Positioning of Ships
Authors: Kim Myung-Hyun , Inman Daniel J. 
Published: November 2020

Abstract
A robust nonlinear observer, utilizing the sliding mode concept, is developed for the dynamic positioning of ships. The observer provides the estimates of linear velocities of the ship and bias from slowly varying environmental loads. It also niters out wave frequency motion to avoid wear of actuators and excessive fuel consumption. The main advantage of the proposed observer is in its robustness. In particular, the observer structure with a saturation function makes the proposed observer robust against neglected nonlinearities, disturbances and uncertainties. Since the mathematical model of DP ships is difficult to obtain and includes uncertainties and disturbances, it is very important for the observer to be robust. A nonlinear output feedback controller is derived based on the developed observer using the observer backstepping technique, and the global stability of the observer and control law is shown by Lyapunov stability theory. A set of simulations was carried out to investigate the performance of the proposed observer for dynamic positioning of a ship.
Dynamics of Oscillator With Soft Impacts
Authors: Peterka František 
Published: November 2020

Abstract
The impact oscillator is the simplest mechanical system with one degree of freedom, the periodically excited mass of which can impact on the stop. The aim of this paper is to explain the dynamics of the system, when the stiffness of the stop changes from zero to infinity. It corresponds to the transition from the linear system into strongly nonlinear system with rigid impacts. The Kelvin-Voigt and piecewise linear model of soft impact was chosen for the study. New phenomena in the dynamics of motion with soft impacts in comparison with known dynamics of motion with rigid impacts are introduced in this paper.
The Use of Experimental Tests in the Formulation of Analytical Models for the Finite Forced Dynamics of Planar Arches
Authors: Alaggio Rocco , Benedettini Francesco 
Published: November 2020

Abstract
The role of the experimental analysis in the formulation of reduced analytical models of planar arches under a vertical, sinusoidally varying, concentrated force on the tip is analyzed in this work. After recalling the theory describing the continuous problem for different initial geometries, using a standard Galerkin procedure, two ode’s are derived and used to enlighten all the interesting phenomena exhibited by different prototypes tested in a companion experimental analysis whose results are also used to validate the shape functions used in the discretization procedure. The principal region of instability of the unimodal symmetric solution in which the nonlinear modal coupling excites antisymmetric components is studied analyzing the bifurcation conditions and the post-critical behavior.
Comparison of the Dynamics of Low Immersion Milling and Cutting With Varying Spindle Speed
Authors: Insperger Tamás , Stépán Gábor , Namachchivaya Sri N. 
Published: November 2020

Abstract
The stability properties of cutting processes are strongly limited by the so-called regenerative effect. This effect is originated in the presence of a time-delay in the dynamical system of the machine tool. This delay is inversely proportional to the cutting speed. Consequently, conventional cutting with a single-edge tool is modeled by an autonomous delay-differential equation (DDE). In case of milling, the varying number of cutting edges results in a kind of parametric excitation, and the corresponding mathematical model is a non-autonomous DDE. In case of low-immersion milling, this affects the stability boundaries in a substantial way. Cutting with varying spindle speed results non-autonomous DDEs where the time delay itself depends on the time periodically. A new semi-discretization method is proposed to handle the stability of these non-autonomous systems. The stability properties and corresponding bifurcations are compared in the above different cases of machining.
A Unified Framework for the Study of Periodic Solutions of Nonlinear Delay Differential Equations
Authors: Fofana M. S. 
Published: November 2020

Abstract
Periodic solutions of delay differential equations (DDEs) splitting into stable and unstable branches are examined in an infinite-dimensional space for fixed and multiple time delays. The center manifold theorem and the classical Hopf bifurcation theorem for the study of periodic solutions of ordinary differential equations (ODEs) are employed to reduce the infinite-dimensional character of the DDEs to finite-dimensional ODEs. Using integral averaging method, the vector field of the ODEs is converted and averaged into amplitude a and phase φ relations. From these relations bifurcation equations of the form ℑ(a, φ) = 0 for the solution branches are derived.
A Study of Chaotic Motion on Non-Linear Vibration-Isolation System
Authors: Ouyang Qing , Zhu Shi-Jian , Shi Yin 
Published: November 2020

Abstract
This paper deals with the vibration isolation efficiency of non-linear vibration-isolation system in a desired chaotic state. Numerical calculation shows that the response of a non-linear vibration system might have broad frequency band characterization, even though the excitation is a harmonic one if some physical parameters of the system is in certain value regimes, hence the force transferred to the supporting foundation from the isolated body will be a broad frequency band one.
The practical experimental set was designed. In order to control the system in a desired chaotic state, the isolator must be a non-linear one with variable stiffness and damping. The chaotic motion of the system was identified through phase space reconstruction and spectral analysis based on the measured test data. The result shows that it is feasible to decrease the single line spectrum component significantly in the response by means of controlling chaotic vibration.
Vibration of an Asymmetrical Shaft With Gravity and Nonlinear Spring Characteristics
Authors: Ishida Yukio , Inoue Tsuyoshi , Liu Jun , Suzuki Akihiro 
Published: November 2020

Abstract
When an asymmetrical shaft is supported by single-row deep groove ball bearings, nonlinear spring characteristics appear due to clearance of bearings and the stiffness of support at the shaft end differs depending on the direction because the equilibrium position of the shaft center line shifts from the center of the clearance due to gravity and misalignment of assembly. Due to the coexistence of the rotating difference in shaft stiffness, the static difference in stiffness at bearing supports and the nonlinear spring characteristics, various kinds of nonlinear parametric resonances and nonlinear forced resonances occur. In this paper, we studied vibrations of harmonic type and super-combination type. As a result, we clarified the following phenomena, such as, division of unstable range, convergence of an unstable vibration to a limit cycle, resonance curve of a hard spring type, and coexistence of a forward and a backward frequency components.
Influence of Seal Geometry on the Rotordynamic Characteristics of a Round-Hole Pattern Damping Seal
Authors: Darden J. Mark , Earhart Eric M. , Flowers George T. 
Published: November 2020

Abstract
In the design of high-speed rotating machinery, engineers are seeking ways to enhance rotordynamic stability margins while minimizing vibration levels. An attractive option to improve stability margins is the use of annular seals. These seals are versatile because they are effective sealing elements, possess both stiffness and damping characteristics, and are easily incorporated into a pump. Design of an effective seal requires insight into the parameters that can influence its rotordynamic characteristics. Analysis indicates that changes in clearance and taper can significantly affect direct stiffness as well as other seal characteristics. With this in mind, test results are presented for seals with identical round-hole pattern stator surface treatments at two constant radial clearances and one tapered-seal configuration. Testing is performed with a realistic, high inlet fluid preswirl condition that enables an evaluation of a given seal’s stabilizing capacity. All test results presented are for a centered seal condition at multiple shaft speeds and pressure levels. Experimental trends are consistent with theory in that gains in direct stiffness are realized with both a decrease in a seal’s radial clearance and with a convergent-taper. Also, the stabilizing capacity of the seals was significantly influenced by the configurations tested.
Driving Characteristics of Traveling Wave Ultrasonic Motor: Effect of Rotor Vibration
Authors: Nakashima Takeshi , Yoshizawa Masatsugu , Kuno Hitoshi , Tsukui Michio , Takatsuka Koro , Akuto Tsuneo 
Published: November 2020

Abstract
The rotor of a traveling wave ultrasonic motor was treated just only as a rigid or flexible body until now. However we examine the effects of the rotor vibration on the driving characteristics of the motor, under the assumption that the bending vibration of the rotor is induced by the stator vibration. Consequently, it is clarified theoretically that the rotor vibration produces six contact patterns between the rotor and the stator. Furthermore the experiments confirm the main theoretical results.
Friction, Instability and Parametric Studies of a Nonlinear Model for an Aircraft Brake Whirl Analysis
Authors: Sinou Jean-Jacques , Thouverez Fabrice , Jezequel Louis , Mazet Guy-Bernard 
Published: November 2020

Abstract
This paper presents a research devoted to the study of instability phenomena in non-linear model with a constant brake friction coefficient. The condition of stability is based on the resolution of a generalized eigenvalue problem and the limit cycle amplitude are determined by the center manifold reduction. A model is presented for the analysis of whirl mode vibration in aircraft braking systems.
In this study, a non-linear material behaviour of the brake heat stack is considered. This non-linearity is expressed as a polynomial. The model does not require the use of brake negative damping and predicts that instability can occur with a constant brake friction coefficient.
The center manifold approach is used to obtain equations for the limit cycle amplitude. The brake friction coefficient is used as unfolding parameter of the fundamental Hopf bifurcation point. The analysis shows that stable and unstable limit cycles can exist for a given constant brake friction coefficient.
Transient Dynamic Analysis of Friction Induced Vibration in Aircraft Brakes
Authors: Glaznieks Dene , Trustee Carl 
Published: November 2020

Abstract
This paper discusses a transient dynamic finite element approach to the investigation of aircraft brake vibration. Specific to this paper, a single wheel and brake model has been used to demonstrate the effectiveness of this approach in the prediction and resolution of brake whirl. The methodology behind this technique is discussed including the modelling of contact interface friction and brake hydraulics.
Design of a Scaled Model for a High Rise, High Speed Elevator
Authors: Zhu W. D. , Teppo L. J. 
Published: November 2020

Abstract
A novel scaled model is developed to simulate the linear lateral dynamics of a hoist cable with variable length in a high rise, high speed elevator. The dimensionless groups used to formulate the scaling laws are derived through dimensional analysis. The model parameters are selected based on the scaling laws subject to space and hardware constraints. It is demonstrated that while it is almost impossible to obtain a fully scaled model unless the model is extremely tall, a reasonably sized model can be constructed with sufficient accuracy. The scaling laws that are not satisfied can be rendered to have a minimal effect on the scaling between the model and prototype. In conjunction with the model design, an analysis of model tension in a closed cable loop is developed. A new movement profile, which ensures a continuous jerk function during the entire period of motion, is derived. Practical considerations that occur in the design of the model are addressed. The methodology can be used to investigate the vibration of a very long cable in other applications.