bluuebunny/crossref_metadata_2025 huggingface dataset:
Use of Measured Mobility to Improve SEA Predictions in the Mid-Frequency Range
Authors: Manning Jerome E.
Published: February 2021

Statistical energy analysis provides a technique to predict acoustic and vibration levels in complex dynamic systems. The technique is most useful for broad-band excitation at high frequencies where many modes contribute to the response in any given frequency band. At mid and low frequencies, the number of modes contributing to the response may be quite small. In this case SEA predictions show large variability from measured data and may not be useful for vibroacoustic design. This paper focuses on the use of measured data to improve the accuracy of the predictions. Past work to measure the SEA coupling and damping loss factors has not been successful for a broad range of systems that do not have light coupling. This paper introduces a new hybrid SEA technique that combines measured mobility functions with analytical SEA predictions. The accuracy of the hybrid technique is shown to be greatly improved at mid and low frequencies.
Time Lag in Handling Responses of Automobiles Induced by Steering/Suspension Compliance or Hysteresis
Authors: Park Jungho , Pan Zhijie
Published: February 2021

This study presents the effect of steering/suspension compliance and hysteresis on the time lag in handling responses of automobiles. A multi-body modeling approach is used to construct the tire, steering, and combined subsystem models. The tire subsystem model focuses on the tire lateral compliance induced time lag. The steering subsystem model focuses on steering/suspension compliance and hysteresis effect on the time lag. The combined model, which is an integration of the tire and steering subsystem models, is to show the combined effect of the subsystems. The simulation results show that the compliance and hysteresis in the steering and/or suspension subsystems are the sources of time lag in responses and that the hysteresis significantly increases the initial time lag.
Low Order Vibration Models for Tracked Vehicles
Authors: Scholar C. , Perkins N. C. , Ma Z.-D.
Published: February 2021

A vehicle track model is developed with the objective of providing new capabilities in modeling track vibration response. Understanding track vibration is essential to evaluating the durability of track components, the vibration energy transmitted to the vehicle, and the acoustic emission from the vehicle. A new element model is derived herein that represents a track span as a continuous elastic member with distributed inertia. This model captures the effects of static track sag. static and dynamic track tension, track translation speed, and the coupling of longitudinal and transverse track vibration. Results from a companion experimental study on a section of track support the use of this continuum approximation. The track element model is extended to describe an entire track circuit for an example military vehicle. An eigenanalysis of this circuit model leads to the system vibration modes that are subsequently employed in a low-order model for forced response. The forced response characteristics resulting from two major excitation sources, roadarm motion and polygonal action, are described. The modal content of the track response is then examined to determine the minimum size model required to describe track vibration. It is concluded that low-order system models may be developed as efficient alternatives to established large degree-of-freedom multi-body track models.
The Application of Non-Linear Boundary Conditions to a Linearly Elastic Model to Achieve Multi-State Structural Behavior in a Large-Displacement Mechanical System Simulation
Authors: McConville James B.
Published: February 2021

Structural elasticity is increasingly perceived as vital to the fidelity of Mechanical System Simulation (MSS) analyses of complex systems under-going large motion. The use of modal elastic system components subject to non-linear loading has become commonplace. An additional use of nonlinear boundary conditions is that of altering the linear elastic behavior of the system structure(s) to achieve multi-state elastic behavior from a single, linear structure. The method is used in this paper to simulate with ADAMS® the effect of an aircraft experiencing a partial structural failure as a result of a hard landing.
Elastic Forces and Coordinate Systems in the Finite Element Formulations
Authors: Berzeri Marcello , Campanelli Marcello , Shabana A. A.
Published: February 2021

The equivalence of the elastic forces of finite element formulations used in flexible multibody dynamics is the focus of this investigation. Two conceptually different finite element formulations that lead to exact modeling of the rigid body dynamics will be used. These are the floating frame of reference formulation and the absolute nodal coordinate formulation. It is demonstrated in this study that different element coordinate systems, which are used for the convenience of describing the element deformations in the absolute nodal coordinate formulation, lead to similar results as the element size is reduced. The equivalence of the elastic forces in the absolute nodal coordinate and the floating frame of reference formulations is shown. The result of this analysis clearly demonstrates that the instability observed in high speed rotor analytical models due to the neglect of the geometric centrifugal stiffening is not a problem inherent to a particular finite element formulation but only depends on the beam model that is used. Fourier analysis of the solutions obtained in this investigation also sheds new light on the fundamental problem of the choice of the deformable body coordinate system in the floating frame of reference formulation. A new method is presented and used to obtain a simple expression for the elastic forces in the absolute nodal coordinate formulation. This method, which employs a nonlinear elastic strain-displacement relationship, does not result in an unstable solution when the angular velocity is increased.
Quasi Exact Solutions for Some Elastodynamics Problems
Authors: Barraco André , Gilbert Marguerite
Published: February 2021

In this paper we develop the formulation for large displacement, large rotation, but small strain, for Timoshenko beam. The so-called “finite rotation vector” is used. Rather to use a finite element formulation we solve the exact semi-local differential equations, written in the actual configuration, using a space (finite difference method) and time (Runge Kutta method) integration scheme. This method is restricted to geometrically simple structures but is developed to validate FEM codes. We present a static and dynamic example.
A Hybrid Highly Parallelizable Algorithm for the Dynamics of Rigid Body Chain Systems
Authors: Duan Shanzhong , Anderson Kurt S.
Published: February 2021

The paper presents a new hybrid parallelizable low order algorithm for modeling the dynamic behavior of multi-rigid-body chain systems. The method is based on cutting certain system interbody joints so that largely independent multibody subchain systems are formed. These subchains interact with one another through associated unknown constraint forces f¯c at the cut joints. The increased parallelism is obtainable through cutting the joints and the explicit determination of associated constraint loads combined with a sequential O(n) procedure. In other words, sequential O(n) procedures are performed to form and solve equations of motion within subchains and parallel strategies are used to form and solve constraint equations between subchains in parallel. The algorithm can easily accommodate the available number of processors while maintaining high efficiency. An O[(n+m)Np+m(1+γ)Np+mγlog2Np](0<γ<1) performance will be achieved with Np processors for a chain system with n degrees of freedom and m constraints due to cutting of interbody joints.
Dynamics of Washing Machines: Mechanical Model and Simulation
Authors: Wagner Falk , Pfeiffer Friedrich
Published: February 2021

This paper deals with the dynamical behavior of washing machines. Due to large unbalance forces of the laundry during the spinning process a mechanical model has been established from d’Alambert’s principle that considers both the rigid body motion and the elastic vibrations. According to the complexity of the machine parts the results of a finite element mode shape analysis are used to describe the elastic behavior. The distinct bodies of the system are linked together through linear and nonlinear force elements resulting in the excitation of several machine orders. In order to verify the model, simulation results are compared with measurements.
Recursive Formalism With a Minimal Dynamic Parameterization for the Identification and Simulation of Multibody Systems
Authors: Chenut Xavier , Fisette Paul , Samin Jean-Claude
Published: February 2021

This paper proposes a recursive formalism to obtain the equations of motion of multibody systems, using a minimal dynamic parameterization. The use of a minimum set of parameters allows its identification, and the recursivity allows to deal with MBS of any size. A semi-explicit form of the equations for subsequent simulation of the MBS is also introduced.

Firstly, a symbolic recursive Newton-Euler formalism in barycentric parameters for open tree-like structures is established. It can be shown that the barycentric parameters appear linearly in these equations which can thus be easily derived with respect to the parameters, leading to the corresponding identification matrix.

However, in the general case, the barycentric parameters do not form a minimal set of parameters for the MBS. As a consequence, the identification matrix can never be made full rank, whatever the excitation trajectory, preventing us from correctly identifying the parameters. Therefore, a minimal set of parameters is obtained using recursive rules that can be applied systematically to any open MBS. These new parameters are then fed into the Newton-Euler equations which conserve their linearity with respect to them.

Finally, a semi-explicit form of the equations of motion is established, using the minimal parameter set, allowing subsequent simulation of the identified MBS.

As regards the applications, the initial motivation of these developments is lying in the field of biomechanics, where knowledge of the dynamic parameters of the human body is of great importance. Based on motion data and reaction force/torques data, a minimal set of parameters for the human body can be identified. Simulation results will be shown during the oral presentation.
A Poisson-Based Formulation for Frictional Impact Analysis of Open and Closed-Loop Multibody Mechanical Systems
Authors: Lankarani Hamid M. , Ayyagari Murthy
Published: February 2021

Frictional impact analysis requires a friction model capable of correct detection of all possible impact modes such as sliding, sticking, and reverse sliding. Conventional methods for frictional impact analysis have either shown energy gain or not developed for jointed mechanical system, and especially not for closed-chain multibody systems. This paper presents a general formulation for the analysis of impact problems with friction in both open- and closed-loop multibody mechanical systems. The Poisson’s hypothesis is used for the definition of the coefficient of restitution, and thus the energy gains inherent with the use of the Newton’s hypothesis are avoided. A canonical form of the system equations of motion using Cartesian coordinates and Cartesian momenta is utilized. The canonical momentum-balance equations are formulated and solved for the change in the system Cartesian momenta using an extension of Routh’s graphical method for the normal and tangential impulses. The velocity jumps are calculated by balancing the accumulated system momenta during the contact period. The formulation is shown to recognize all modes of impact; i.e., sliding, sticking, and reverse sliding. The impact problems are classified into seven cases, and based on the pre-impact system configuration and velocities, expressions for the normal and tangential impulses are derived for each impact case. Examples including the impact of a falling rod on the ground, the tip of a double pendulum impacting the ground, and the impact of the rear wheel and suspension system of an automobile executing a very stiff bump are analyzed with the developed formulation.
Defining the Coefficient of Restitution for the Impact Between Free and Constrained Bodies
Authors: Escalona J. L. , Mayo J. M. , Domínguez J.
Published: February 2021

This paper revisits the coefficient of restitution involved in the impulse-momentum balance equations for colliding rigid bodies and examines its extension to impacts between flexible bodies. The analytical solution to axial impact on a flexible rod is used to demonstrate that the coefficient of restitution is not inherent in the underlying physical process. In fact, the type of coefficient to be used in each case depends on the particular model employed by the analyst to describe flexibility in the bodies concerned. It is demonstrated that the coefficient of restitution used in the generalized impulse-momentum balance for flexible bodies does not represent a physical magnitude. In any case, as shown in this paper, the ratio between the relative velocities at the contact points or surfaces of the flexible bodies before and after impact is no measure of the local loss of mechanical energy during the process.
Pieced-Interval Modal Response of Elastic Systems With High-Frequency Excitations
Authors: Khulief Y. A.
Published: February 2021

The current technology manifests a great demand for high precision and high positioning accuracy in many engineering applications that range from robot manipulators and high-speed flexible mechanisms to supercritical rotors and the space deployable structures. A reliable dynamic model is crucial to the performance evaluation and precision control of such elastic mechanical systems. The modeling problem becomes even more difficult when higher frequencies of such large scale systems are excited. A pieced-interval modal analysis scheme is introduced to alleviate the problem of handling a system of widespread eignspectrum. A set of energy indices is defined to monitor the energy content in higher modes. The numerical scheme invokes a modal transformation with changeable basis that accounts for higher modes only when they are excited, and picked up more proportional values of the systems total energy. Numerical examples are presented to demonstrate the applicability of the developed method and to display its potential in performing efficient modeling of the dynamic behavior of such systems.
Motion Design by Interference Analysis of Multibody Systems
Authors: Wang Deming , Beale David
Published: February 2021

A new computer aided analysis method for frictionless interference impact problems between two bodies in a constrained multibody system is presented in the paper, which can be used to perform interference analysis and motion design of multibody systems. A virtual contact joint concept is used to detect interference between two bodies and calculate the jump in the body momenta, velocity discontinuities, rebounds and system motion after the interference impact analysis. The interference surfaces can be any geometric element, such as point, line segment, are and circle described by the joint coordinates of the virtual contact joint. The method are very useful to predict and determine the interference time, the types and positions of two impact surfaces. System motion after the interference can be controlled by changing some dynamic parameters in the multibody system.
Development of the Mobile Manipulator Analyzer
Authors: Pitts David T. , Emami M. Reza , Goldenberg Andrew A.
Published: February 2021

This paper presents a simulation package for mobile manipulators that incorporates toolbox software based on commercial dynamic simulation packages, a validation procedure, and an algorithm to tune the system parameters to match the real system. Finally, as an application of the package, an optimization procedure on the design parameters of a commercial robot with results is presented.
Flatness-Based Control of Underconstrained Cable Suspension Manipulators
Authors: Maier Thomas , Woernle Christoph
Published: February 2021

Underconstrained cable suspension manipulators support a load platform in space by less than six spatially arranged cables with independently controllable winches. To control the motion of the platform along desired trajectories in space, the classical inverse kinematic or computed-torque schemes are generalized using the concept of flat systems. For desired trajectories of the load platform and a sufficient number of their time derivatives, the control inputs can be algebraically calculated. Asymptotically stable tracking behaviour is achieved by cascaded feedback of state variables. The application of the method is shown for a planar overhead trolley crane as well as for a novel three-cable suspension manipulator.
A Virtual Body and Joint for Constrained Flexible Multibody Dynamics: A Generalized Recursive Formulation
Authors: Bae D. S. , Han J. M. , Choi J. H.
Published: February 2021

This research extends the generalized recursive formulas for the rigid body dynamics to the flexible body dynamics using the backward difference formula (BDF) and the relative generalized coordinate. When a new force or joint module is added to a general purpose program in the relative coordinate formulations, the modules for the rigid bodies are not reusable for the flexible bodies. Since the flexible body dynamics handles more degrees of freedom than the rigid body dynamics does, implementation of the flexible dynamics module is generally complicated and prone to coding mistakes. In order to overcome the implementation difficulties, a virtual rigid body is introduced at every joint and force reference frames. A virtual flexible body joint is introduced between two body reference frames of the virtual and original bodies. Since the multibody system dynamics are formulated by highly nonlinear algebraic and differential equations and there are many different types of joints, a tremendous amount of computer implementation is required to develop a general purpose dynamic analysis program using the relative coordinate formulation. The implementation burden is relieved by the generalized recursive formulas. The notationally compact velocity transformation method is used to derive the equations of motion in the joint space. The terms in the equations of motion which are related to the transformation matrix are classified into several categories each of which recursive formula is developed. Whenever one category of the terms is encountered, the corresponding recursive formula is invoked. Since computation time in a relative coordinate formulation is approximately proportional to the number of the relative coordinates, computational overhead due to the additional virtual bodies and joints is minor. Meanwhile, implementation convenience is dramatically improved.
Dynamics of Reconfigurable Multibody Systems
Authors: Takahashi Takashi , Matunaga Saburo , Ohkami Yoshiaki
Published: February 2021

Multibody dynamics with configuration changes are characterized by changes in the number and/or kind of constraint equations. Configuration changes mean the addition of impacts, changes of friction states, topological changes and so on. When we consider, for example, the capturing and removing process of the damaged satellites by redundant space robots, such a reconfigurable multibody dynamics must be considered. Dynamics of such a system has not been studied well though it is indispensable to develop the well-functioning automatic machines and robots in space as well as on the earth. We introduced the method to express the time-varying system topologies based on the graph theory and the linked-list, and reformulated the efficient dynamics algorithm based on the “order n algorithm” for forward dynamics of closed-loops systems. In this paper, we explain the above algorithms and how to implement a computer program using the object-oriented programming method. Furthermore, we examine how to apply these programs to space systems.
ODE Methods for Solving the Multibody Dynamics With Constraints
Authors: Koganezawa Koichi , Kaneko Kazuomi
Published: February 2021

This paper deals with methods for solving the multi-body dynamics with constraints. The problem is considered in the framework of solving the Lagrange multipliers in addition to the system coordinates in the differential and algebraic equation (DAE) governing the dynamics with holonomic or non-holonoinic constraints. The proposed methods are originally based on Baumgarte’s work for the holonomic constraints but its extensions. First, one considers a Lagrangian which includes the time-differentiated constraint equations in addition to the constraint equations themselves. Applying the Lagrange procedure we have the ordinary differential equations (ODE), not the DAE, including the differential equation with respect to the Lagrange multipliers. This paper also presents a numerically stable method for inverting the system matrix. The numerical solution for the differential equations with respect to the Lagrange multipliers as well as the system coordinates by using the ordinary numerical integration method, e.g. Runge-Kutta method, shows the excellent stability of the constraints, which is superior to the penalty method.
An Analytical Scheme for Stochastic Dynamic Systems Containing Fractional Derivatives
Authors: Agrawal Om P.
Published: February 2021

This paper presents an analytical technique for the analysis of a stochastic dynamic system whose damping behavior is described by a fractional derivative of order 1/2. In this approach, an eigenvector expansion method proposed by Suarez and Shokooh is used to obtain the response of the system. The properties of Laplace transforms of convolution integrals are used to write a set of general Duhamel integral type expressions. The general response contains two parts, namely zero state and zero input. For a stochastic analysis the input force is treated as a random process with specified mean and correlation functions. An expectation operator is applied on a set of expressions to obtain the stochastic characteristics of the system. Closed form stochastic response expressions are obtained for white noise. Numerical results are presented to show the stochastic response of a fractionally damped system subjected to white noise.
State-Space Based Implicit Integration of the Differential-Algebraic Equations of Multibody Dynamics
Authors: Negrut Dan , Haug Edward J.
Published: February 2021

Three methods for the state-space based implicit integration of differential-algebraic equations of multibody dynamics are summarized and numerically compared. In the state-space approach, the time evolution of a mechanical system is characterized using a number of generalized coordinates equal with the number of degrees of freedom of the system. In this paper these independent generalized coordinates are a subset of the Cartesian position coordinates and orientation Euler parameters of body centroidal reference frames. Depending on the method, the independent generalized coordinates are implicitly integrated and dependent quantities (including Lagrange multipliers) are determined to satisfy constraint equations at position, velocity, and acceleration levels. Five computational algorithms based on the proposed methods are used to simulate the motion of a stiff 14-body vehicle model. Results show that the proposed methods deal effectively with challenges posed by stiff mechanical system simulation. A comparison with a state-space based explicit algorithm for the simulation of the same model indicates a speed-up of approximately two orders of magnitude.
Nonlinear Dynamics of Rigid and Flexible Multibody Systems
Authors: Zakhariev Evtim V.
Published: February 2021

In the present paper a unified numerical approach for dynamics modeling of multibody systems with rigid and flexible bodies is suggested. The dynamic equations are second order ordinary differential equations (without constraints) with respect to a minimal set of generalized coordinates that describe the parameters of gross relative motion of the adjacent bodies and their small elastic deformations. The numerical procedure consists of the following stages: structural decomposition of elastic links into fictitious rigid points and/or bodies connected by joints in which small force dependent relative displacements are achieved; kinematic analysis; deriving explicit form dynamic equations. The algorithm is developed in case of elastic slender beams and finite elements achieving spatial motion with three translations and three rotations of nodes. The beam elements are basic design units in many mechanical devices as space station antennae and manipulators, cranes and etc. doing three dimensional motion which large elastic deflections could not be neglected or linearised. The stiffness coefficients and inertia mass parameters of the fictitious joints and links are calculated using the numerical procedures of the finite element theory. The method is called finite elements in relative coordinates. Its equivalence with the procedures of recently developed finite segment approaches is shown, while in the treatment different results are obtained. The approach is used for solution of some nonlinear static problems and for deriving the explicit configuration space dynamic equations of spatial flexible system using the principle of virtual work and Euler-Lagrange equations.
Parallel Implementation of a New Algorithm for Dynamics of Multibody Systems
Authors: Duan Shanzhong , Anderson Kurt S.
Published: February 2021

In this paper, the new hybrid parallelizable low order algorithm developed by authors is coded in C and MPI, and is implemented numerically on parallel computing systems. To reduce communication overhead, different parallelisms and parallel solution strategies are used for forming and solving equations of motion and constraint equations. The presented implementation can accommodate the general spatial motion of a chain system allowing rotations and translations between neighboring bodies. Different numbers of key joint separations are used to study the influence of increasing dimension of system constraint equations on the overall computational efficiency of the algorithm. Numerical results for implementations of the spatial chain system show that the cutting of certain user-specified joints rather than every joints offers better computational performance. Comparisons between full sequential recursive implementation and parallel implementation of the same algorithm are presented in the form of speedup. Numerical results show that significant speedup can be obtained.
Efficient Dynamic Analysis Method for Multibody Systems With Constraint Violation Stabilization Method
Authors: Reungwetwattana Apiwat , Toyama Shigeki
Published: February 2021

This paper presents an efficient extension of Rosenthal’s order-n algorithm for multibody systems containing closed loops. Closed topological loops are handled by cut joint technique. Violation of the kinematic constraint equations of cut joints is corrected by Baumgarte’s constraint violation stabilization method. A reliable approach for selecting the parameters used in the constraint stabilization method is proposed. Dynamic analysis of a slider crank mechanism is carried out to demonstrate efficiency of the proposed method.
Optimized Realization of Fault-Tolerant Heteropolar Magnetic Bearings for Active Vibration Control
Authors: Na Uhn Joo , Palazzolo Alan
Published: February 2021

The nature of coupling in the heteropolar magnetic bearings permits other remaining active coils in the stator to assume actions of the failed coils to produce the same force resultants. This fault-tolerant control usually reduces load capacity because the redistribution of the magnetic flux which compensates for the failed coils leads to premature saturation in the stator or journal. Distribution matrix of voltages which consists of redefined biasing voltage vector and two control voltage vectors can be optimized in the manner that peak flux density is minimized. An elegant optimization method using Lagrange Multiplier is presented in this paper. The redistribution matrices calculated with Lagrange Multiplier method were compared with Maslen and Meeker’s solutions, local minima are guaranteed and also the global minimum can be obtained if an effective global minimum searching algorithm is used. The linearized control forces can be realized up to certain combination of 5 poles failed for the 8 pole magnetic bearing. Position stiffness and voltage stiffness are calculated for the fault-tolerant magnetic bearings. Simulations show that fault-tolerant control of the multiple poles failed magnetic bearings with a horizontal flexible rotor can be stabilized with reduced load capacity.
High Cycle Fatigue Cracks at Radial Fan Impellers Caused by Aeroelastic Self-Excited Impeller Vibrations: Part I — Case History, Root Cause Analysis, Vibration Measurements
Authors: Eckert Lothar
Published: February 2021

Hydrogen-cooled two-pole turbogenerators are equipped with one single-stage radial fan for cooling gas ventilation. The impellers with outer diameters of up to 1.5 m operate with 3000 rpm or 3600 rpm. High cycle fatigue cracks have occurred at two radial fan impellers operated at 3000 rpm.

An extensive root cause analysis was performed to identify the cause of these cracks. Impeller vibration measurements in the generator unit finally allowed the successful identification of the root cause. The very strong impeller vibrations were caused by an aeroelastic self-excitation mechanism. By modification of the stationary impeller surrounding the aeroelastic self-excitation was eliminated.
Mode Identification for Rotating Rigid Shaft With Flexible Disks by Mode Splits
Authors: Lee Chong-Won , Ham Jong-Seok
Published: February 2021

This paper investigates the mode splits of the bending coupled modes of a rotating shaft with multiple flexible disks, in which the disks are rigidly attached to the rigid shaft supported by bearings. The bending coupled modes, in which shaft bending modes are coupled with one nodal diameter disk modes, are classified as the balanced and unbalanced modes. The mode splits of the balanced modes are the same as those of pure disk modes since the shaft does not experience any motion. On the other hand, the mode splits between pairs of the forward and backward unbalanced modes are found to be dependent upon the disk/shaft configuration and the shaft support stiffness, as well as the rotational speed and the ratio of polar to diametrical moment of inertia.
Optimum Balancing of Three-Dimensional “RSSR” Mechanisms
Authors: Coelho Tarcisio Antonio Hess , Alves Valter Francisco Arruda
Published: February 2021

The Generalized Reduced Gradient method of numerical optimization is applied in obtaining the reduction of moments and forces transmitted to the frame of a three-dimensional RSSR mechanism. Such a modification of dynamic behavior of the mechanism, or balancing, is achieved by the addition of counterweights attached to the moving links in an off-line position. The evaluation of the obtained optimum configuration is performed by comparing the measured vibration levels of the frame of physical models of the balanced and unbalanced mechanism.
Use of the Campbell Diagram in Rotordynamics
Authors: Lalanne Michel , Ferraris Guy
Published: February 2021

This paper deals with bending in the field of monorotors, such as in compressors and turbines, and co-axial multirotors, such as in jet engines. This presentation concerns the use of the Campbell diagram and highlights some specific cases of its use: symmetric systems and highly damped systems.
Optimum Design of Magnetic Head Slider Under Static and Dynamic Operation Conditions of Hard Disk Drive
Authors: Hattori Yasuhisa , Hashimoto Hiromu , Ochiai Masayuki
Published: February 2021

The aim of this paper is to develop the general methodology for the optimum design of magnetic head slider for improving the spacing characteristics between head slider and disk surfaces under the static and dynamic operation conditions of hard disk drive and to present an application of the methodology to IBM 3380-type slider design. In the optimum design, the objective function is defined as the weighted sum of minimum spacing, maximum difference of spacing due to variation of radial location of head and maximum amplitude ratio of slider motion. Slider rail width, taper length, taper angle, suspension position and preload are selected as the design variables. Before the optimization of magnetic head slider, the effects of these five design variables on the objective function are examined by the parametric study, and then the optimum design variables are determined by applying the hybrid optimization technique combining the direct search method and the successive quadratic programming (SQP). From the results obtained, the effectiveness of optimum design on the spacing characteristics of magnetic head slider is clarified.
A Method for Analyzing Electromagnetic-Force-Induced Vibration and Noise From Motors
Authors: Shiohata Koki , Nemoto Kanako , Kobayashi Takashi
Published: February 2021

Electromagnetic force calculated by 2-dimensional analysis is transformed into exciting force for 3-dimcnsional structural-vibration analysis. And a procedure for modeling a vibrating structure is developed. Furthermore, a space-modal-resonance criterion, which relates electromagnetic force to structural vibration or noise, is introduced. In the structural-vibration analysis, the finite clement method is used; and in the noise analysis, the boundary element method is used. And vibration and noise of an induction motor are evaluated by using this criteria. Consequently, high-accuracy modeling is achieved and calculated noise almost completely coincides with that measured by experiments. And it is clarified that the-space-modal resonance criterion is effective on numerical simulation.
Vibration Analysis of Rotor-Bearing Systems With Internal Damping and Torsional Effects
Authors: Mohiuddin M. A. , Khulief Y. A. , Al-Juruf R. S.
Published: February 2021

This paper extends the model of the linearly tapered Timoshenko shaft finite element developed by the authors to include the effect of internal viscous and hysteretic damping. The resulting model accounts, in addition to internal damping, for bending, rotary inertia, gyroscopic moments, transverse shear deformations and torsion. The developed model has been programmed in a fairly general way to be applicable to a general rotor-bearing system where both anisotropic bearings and internal damping are present. Numerical results of modal characteristics as well as dynamic responses are generated.
A Model for Thermal Bending in Overhung Rotors
Authors: Balbahadur A. C. , Kirk R. G.
Published: February 2021

An approximate model for thermal bending caused by viscous lubricant shearing in overhung rotors has been developed. This model has been tested against a published theoretical model and an experimental study. It was found that the current model agreed well with both the other theoretical model and the experimental data.
Multi-Objective Optimum Design of Rotor-Bearing Systems With Dynamic Constraints Using Immune-Genetic Algorithm
Authors: Choi Byung-Gun , Yang Bo-Suk
Published: February 2021

An immune system has powerful abilities such as memory, recognition and learning how to respond to invading antigens, and is applying to many engineering algorithms in recent year. In this paper, the combined optimization algorithm (Immune-Genetic Algorithm: IGA) is proposed for multi-optimization problems by introducing the capability of the immune system that controls the proliferation of clones to the genetic algorithm. The new combined algorithm is applied to minimize the total weight of the shaft and the resonance response (Q factor), and to yield the critical speeds as far from the operating speed as possible. These factors play very important roles in designing a rotor-bearing system under the dynamic behavior constraints. The shaft diameter, the bearing length and clearance are chosen as the design variables. The dynamic characteristics are determined by applying the generalized FEM. The results show that the combined algorithm can reduce the weight of the shaft and improve the critical speed and Q factor with dynamic constraints.
Object Trajectory Tracking Control for Flexible-Link Multiple Manipulators
Authors: Sun Qiao
Published: February 2021

In this paper, we consider the object trajectory tracking control for flexible-link cooperating manipulators. In particular, we develop a stable inversion control law which is commonly known as the inverse dynamics control or the computed torque method for rigid manipulators. Difficulties in applying this method to the control of flexible link manipulators are due to the fact that the inverse dynamics system is generally unstable. As such, bounded actuator torques cannot be guaranteed. For multiple manipulators handling a common object, there are more actuators than the degrees of freedom of the system. Through decomposing the manipulator end-effector wrenches into resultant and internal force components, control laws are designed such that the internal forces are used to stabilize the system zero dynamics. Consequently, nonlinear inversion control can be applied for the object trajectory tracking control.
Time-Varying Cross-Spectra by Harmonic Wavelets for Soil Motion With Damage
Authors: Newland David E. , Butler Gary D.
Published: February 2021

Experimental records of acceleration time-history at several different heights in a centrifuged soil model have been analysed by the harmonic wavelet method to generate time-varying cross-spectra. These cross-spectra are compared with simulated results for a linear model. Local changes in the experimental cross-spectra, both amplitude and phase changes which are not present in the simulated results, are evidence of sudden changes in soil properties during dynamic testing.
The Motion of a Flyline: Part A — Governing Equations
Authors: Hoffmann Jon A. , Reth Peov
Published: February 2021

When fly fishing, a flyline is used to transport and launch a lure to the location of fish. Equations which describe the motion of a level flyline during the forward cast has been developed for the case of line release from the rod. After the work input phase, the cast was considered to be composed of loop formation, line unrolling, loop dissipation and final descent phases. The work-energy equation and Newton’s law were used to generate a finite element computational model for the forward cast in dimensionless form.
Bifurcations in the Dynamics of Two Coupled van der Pol Oscillators With Delay Coupling
Authors: Wirkus Stephen , Rand Richard
Published: February 2021

We investigate the dynamics of a system of two van der Pol oscillators with delayed velocity coupling. We use the method of averaging to reduce the problem to the study of a slow-flow in three dimensions. We study the steady state solutions of this slow flow, with special attention given to the bifurcations accompanying their change in number and stability. Our interest in this system is due to its relevance to coupled laser oscillators.
Order Reduction and Control of Large-Scale Linear Time Periodic Dynamical Systems
Authors: Deshmukh Venkatesh , Sinha S. C.
Published: February 2021

This paper provides methodology for designing reduced order controllers for large-scale, linear systems represented by differential equations having time periodic coefficients. The linear time periodic system is first converted into a form in which the system stability matrix is time invariant. This is achieved by the application of Liapunov-Floquet transformation. Then a system called an auxiliary system is constructed which is a completely time invariant. Order reduction algorithms are applied to this system to obtain a reduced order system. The control laws are calculated for the reduced order system by minimizing the least square error between the auxiliary and the transformed system. These control laws when transformed back to time varying domain provide the desired control action. The schemes formulated are illustrated by designing full state feedback and output feedback controllers for a five mass inverted pendulum exhibiting parametric instability.
A New Strategy for Detecting Gear Faults Using Denoising With the Orthogonal Discrete Wavelet Transform (ODWT)
Authors: Berri Sidi M. , Klosner J. M.
Published: February 2021

This paper investigates a new strategy for early detection of defects in a power transmission pair of spur gears. Sensitivity to local defects is enhanced by processing the signal as follows. The orthogonal discrete wavelet transform (ODWT) of the band-pass filtered averaged signal is first obtained. This is followed by thresholding in the wavelet domain, thereby removing the low amplitude noise contribution. The inverse wavelet transform then essentially reconstructs the component of the signal that is due to the defect. Experimental results demonstrate the efficiency of this procedure.
Point-Wise Dimension Estimate of Nonstationary, Multi-Episode, Time-Series and Application to Gearbox Signal
Authors: Lin D. C. , Augustine B. J. , Golnaraghi M. F.
Published: February 2021

Dimensions of nonstationary time series is studied. The nonstationarity is considered to be due to multiple episode where an episode is a piece of stationary time series. The dimension estimation algorithms in the literature can be naturally extended to study multi-episode time series by restricting the calculation on data segment of pre-determined length. Inevitably, more than one episode will be included in the segment. This work focuses on finding when such dimension estimate has a local interpretation as the dimension of the episode. It was found that the local interpretation is valid if there is a large enough difference in the autocorrelation time of the episodes. This is termed EES. In practice, the average first passage time of the reconstructed “orbit” can be used to determine EES. Numerical evidence of these results are given and the application to the mechanical gearbox signal are shown.
Experimental Investigation of Noise Sources in a Needle Roller Bearing System
Authors: Baldanzini Niccolò , Beraldo Federico , Carfagni Monica
Published: February 2021

An experimental investigation was undertaken to determine the causes of noise emission scatter in hosiery machines. Following the experimental measurement of the sound power levels, the hosiery machine’s mechanical system was assembled and tested with components of various sizes. The results indicated that the source of the noise emissions was a bearing’s outer race. Analysis of the outer race’s roundness profile in relation to vibrations provided accurate predictions of machine behavior. On the basis of a correlation between noise and vibrations, a practical method of online monitoring was developed.
Experimental Characterization Techniques for High Performance Hard Disk Drive Ball Bearing Spindle Motors
Authors: Chong Andrew , Yi Lu , Chen S. X. , Zhang Q. D.
Published: February 2021

The key task for the spindle motor in a hard disk drive is to provide stable, reliable and consistent turning power for many years to allow the hard drive to function properly. As hard disks become more advanced, virtually every component in them is required to do more & perform better, and the spindle motor is no exception. Increasing the rotational speed at which the platters spin means that the data can be read off the disk faster, and also reduces rotational latency, the time that the heads must wait for the correct sector number to come under the head. For this reason, there has been a push to increase the speed of the spindle motor. Since the launching of hydro-dynamic bearing spindle technology for high speed application will not be in due course, current ball bearing technology will still be around for a couple of years provided the spindle speed does not exceed around 15 Krpm. Therefore optimizing the steel balls in the spindle system is an alternative to deal with the ever-increasing performance requirements of the hard disk drive. To accomplish this, we have to understand the failure phenomenon in the spindle, thereby set test requirements to overcome the failure mechanism. These test requirements will help us to understand the performance characteristic and robustness of the spindle motor.

In this paper, the test requirements is set according to modal, load and vibration methods to quantify the hard disk drive ball bearing spindle motor.
Separating the Contributions in Localization Methods: A Technique to Enhance Identification of Damping Related Parameters
Authors: Algrain Hervé , Conti Calogero , Dehombreux Pierre
Published: February 2021

Finite Element Model Updating has for objective to increase the correlation between the experimental dynamic responses of a structure and the predictions from a model. Among different initial choices, these procedures need to establish a set of representative parameters to be updated in which some are in real error and some are not. It is therefore important to select the correct properties that have to be updated to ensure that no marginal corrections are introduced. In this paper the standard localization criteria are presented and a technique to separate the global localization criteria in family-based criteria for damped structures is introduced. The methods are analyzed and applied to both numerical and experimental examples; a clear enhancement of the results is noticed using the family-based criteria. A simple way to qualify the stability of a localization method to noise is presented.
Characterizing Damping and Restitution in Compliant Impacts via Linear Viscoelastic Models
Authors: Butcher Eric A. , Segalman Daniel J.
Published: February 2021

Strategies for characterizing damping and restitution in compliant impacts while eliminating the force discontinuities associated with the standard Kelvin-Voigt model are examined within the framework of linear viscoelasticity. A modification of the Kelvin-Voigt model as well as higher-order (Maxwell and standard linear) models are studied in an effort to satisfy the expected force-displacement boundary conditions. The restitution coefficients, energy losses per cycle, and equivalent linear damping ratios are then obtained analytically as functions of the dimensionless viscoelastic parameters which may be easily related to and obtained from experimentally measured restitution coefficients.
Torsional Vibrations of Laminated Beams: Comparison of Models
Authors: Nouri-Baranger Thouraya , Trompette Philippe , Shakhesi Said
Published: February 2021

Torsional dynamical behavior, natural frequencies and damping ratios of rectangular laminated beams are analysed through different displacement F.E. moderations which use: a semi-analytical finite element, an homogenization theory and a three dimensional analysis. All the results are compared to experimental values.
Thickness Deformation of Constrained Layer Damping: An Experimental Evaluation
Authors: Huang Peter Y. H. , Reinhall Per G. , Shen I. Y. , Yellin Jessica M.
Published: February 2021

Constrained layer damping can be an effective method to control transverse vibration of thin structures. The commonl used equation of motion governing the behavior of constrained layer damped Euler-Bernoulli beams, originally derived b Mead and Markus (1969), does not account for the relative transverse motion between the constraining layer and the base beam. When a soft viscoelastic layer or a stiff constraining layer is used, this relative transverse motion may become significant. To account for this motion, Miles and Reinhall (1986) developed a model that included the thickness deformation of the viscoelastic layer. The purpose of this paper is to demonstrate the existence of the thickness deformation through experiments and to investigate the validity of the Miles and Reinhall model. Experimental results show that the thickness deformation is significant in the high frequency range, and that the inclusion of the thickness deformation improves the accuracy of the analytical model.