bluuebunny/crossref_metadata_2025 huggingface dataset:
On the Behaviour of Steamwhirl and Nonlinear Rotor-Bearing Systems
Authors: Gómez-Mancilla Julio C. , Dimarogonas Andrew D.
Published: March 2021

The problem of steamwhirl is the technological limit which now prohibits the development of power generating turbomachinery substantially above 1 GW. Due to the steam flow, self excited vibrations develop at high loads, above the onset of instability of the linearized system, in the form of stable limit cycles which, at even higher loads, deteriorate to chaotic vibration.

The bearing nonlinearity is introduced in the form of high order coefficients of a Taylor expansion of the perturbation forces for fixed-arc slider bearing and employing non-linear pad functions for the tilting pad bearings. The flow excitation is introduced in the form of radial and tangential force gradients related to the flow and power generated.

The study of stable and unstable limit cycles and stability of the system in the large, beyond the linear analysis currently utilized, is done analytically for the DeLaval rotor and numerically with Finite Element analysis of typical turbomachinery rotors.

The range of loads for which limit cycles exist was found to be substantial. This is important for the operation of large machinery because such limit cycles permit the operation at loads much higher than the ones which correspond to the onset of instability of the linearized system. The conditions for the limit cycle deterioration into chaotic orbit is studied. Analytical expressions have been obtained for the different thresholds for the DeLaval rotor.
Frequency Response Characteristics of a Revolute Impact Pair
Authors: Wang Y.
Published: March 2021

Clearances in mechanical joints have deteriorating effects on the dynamic behavior of a machine in increasing noise and vibration and reducing the performance. In order to properly characterize these effects and to develop analytical techniques for machine design, it is necessary to investigate the dynamics associated with basic models of impacting systems. In this paper, we develop a method of harmonic balance to study a revolute impact pair. We focus on the characteristics of nonlinear frequency response of the system for a single frequency excitation. These characteristics include multiply-valued steady state response, multiple jump resonances, and existence and stability of these solutions. The effectiveness of the harmonic balance method combined with the Fast Fourier Transform technique is shown through numerical examples.
The Nonstationary Effects in Asymmetric, Angle-Ply Laminated Composite Plates
Authors: Evan-Iwanowski Ross M. , Nayfeh J. F. , Lu C. H.
Published: March 2021

The system in the title has been subjected to a parametric, nonstationary (NS) linear v(t) = v0 + βt, and cyclic v(t) = v0 ± γ sin βt excitations. The NS linear responses settle on the initial, constant values for extended values of the excitation frequencies, thus they stabilize the stationary (ST) response. This is true for the initial conditions taken on the stationary curve, and for different ply-angles. For the initial conditions (I.C.) beyond the ST plots, the NS responses stay also near the initial conditions, but they have the wavy forms, which increase slightly for the lower values of the forcing frequencies. For the cyclic parametric excitations, the NS responses are cyclic contained within the ranges of the excitation amplitudes ±β and (finite) response amplitudes above the ST initial values, raising up and down within these limits. It appears that they cover the whole area within the above described constraints. The decisive effect of the cyclic NS inputs, i.e., almost instantaneous cyclic responses replacing the ST responses regardless of the I.C. and ST responses, is a bench mark of the cyclic NS. This behavior is distinctly different from the NS cyclic responses of the composite columns.
Probabilistic Failure Prediction of SCS-6/Ti-15-3 MMC Ring
Authors: Holland Frederic A. , Zaretsky Erwin V. , Melis Matthew E.
Published: March 2021

Two-parameter Weibull analysis was used to predict the fracture strength and fatigue life of an SCS-6/Ti-15-3 MMC ring from coupon sample data. The fracture strength and fatigue life of the ring were assumed to be volume dependent. The predicted fracture strengths were determined in terms of maximum allowable ring internal pressure. Two methods were used. One simple method was to calculate an effective volume for an idealized ring on the basis of a theoretical solution approximating the stress distribution. The fracture strength and fatigue life of the coupon samples were then scaled to the effective volume of the ring. The other method utilized finite-element analysis to determine a more realistic stress distribution in the actual, geometrically imperfect ring. The total reliability of the ring was then determined by the product of the elemental reliabilities with coupon samples used as a gage. These approaches were compared with experimental fracture strength results. No fatigue data for the ring were available for comparison. Preliminary results indicate that Weibull analysis of coupon samples shows promise in predicting the fracture strength of metal-matrix composite structures.
Complimentarity Problems of Stick-Slip Vibrations
Authors: Pfeiffer Friedrich
Published: March 2021

Multibody systems with many friction contacts not being decoupled by some force laws afford a special treatment with respect to the uniqueness of the solution after a contact event. This problem can be solved by an optimization techniques including unequality constraints which corresponds exactly to the physical properties of stick-slip vibrations. The theoretical background to this complementarity problem is presented and illustrated by examples from machine dynamics.
Interpolated Mapping System Identification From Time Series Data
Authors: Bursal Faruk H. , Tongue Benson H.
Published: March 2021

In this paper, a system identification algorithm based on Interpolated Mapping (IM) that was introduced in a previous paper is generalized to the case of data stemming from arbitrary time series. The motivation for the new algorithm is the need to identify nonlinear dynamics in continuous time from discrete-time data. This approach has great generality and is applicable to problems arising in many areas of science and engineering.

In the original formulation, a map defined on a regular grid in the state space of a dynamical system was assumed to be given. For the formulation to become practically viable, however, the requirement of initial conditions being taken from such a regular grid needs to be dropped. In particular, one would like to use time series data, where the time interval between samples is identified with the mapping time step T. This paper is concerned with the resulting complications. Various options for extending the formulation are examined, and a choice is made in favor of a pre-processing algorithm for estimating the FS map based on local fits to the data set. The suggested algorithm also has smoothing properties that are desirable from the standpoint of noise reduction.
Control of Parametrically Excited Systems via Time-Invariant Methods
Authors: Joseph Paul , Sinha S. C.
Published: March 2021

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.
The Use of Condition Number of a FRF Matrix in Mechanical Parameter Identification
Authors: Wang Jhy-Horng , Liou Chen-Sung
Published: March 2021

A new identification algorithm is proposed in this work to identify the parameters of mechanical joints. The method considers the whole structure as two substructures which are connected by the joints to be identified. The frequency response functions of the whole structure and substructures are used to extract the joint parameters. In contrast to the traditional methods, only a FRF matrix is needed to inverse in the proposed method. Therefore, it is possible to calculate the condition number of the FRF matrix before the identification. The condition number is defined as the ratio of the maximum singular value divided by the minimum one of a matrix. The condition number of noise contaminated FRF matrix can be used to indicate the sensitivity of the FRF matrix to measurement noise. Therefore, the condition number can be used to avoid the ill-conditioned problem by eliminating the ill-conditioned FRF in some frequency ranges before identification. The simulated results show that the proposed method can significantly improve the accuracy of identification.
Prediction of the Frequency and Time Responses of Composite Structures: Application to Skis
Authors: Ulrich C. , Ferraris G. , Lalanne M. , Lacroix J.
Published: March 2021

The prediction of the dynamic behavior of composite structures composed of several viscoelastic materials is investigated. The material characteristics are a function of frequency and temperature which here will be kept constant and some material may be orthotropic. The method proposed is an extension of the pseudo-modal method presented previously Improvements have been obtained in the prediction of the natural frequencies and of the damping factors. Time response has also been developed. The pseudo-modal method uses a very low number of modes and thus allows a drastic reduction of the degrees of freedom, from several thousands to tens. The equations obtained are very efficient in predicting the frequency response and the time response.

The applications presented concern measurements and predictions using a finite element computer program. The initial test was based on a relatively simple example: a layered damped beam. Then an alpine ski was studied. Prediction and measurement correspond well.
Concurrent Optimization of Product Design and Manufacturing Coping With Demand Variability
Authors: Yoshimura Masataka , Takeuchi Atsushi
Published: March 2021

A user-oriented product design methodology for integrating design, manufacturing and marketing is proposed and the practical design optimization procedures are constructed and presented. First, market demand analyses are conducted by dividing users into groups based on similarities of users’ needs. The product satisfaction level of each group is formulated using the users’ satisfaction levels for product attributes. Next, in order to obtain optimum design solutions effectively in the integrated decision making processes of design, manufacturing and marketing (which include an enormous number of decision variables), multiphase procedures of design optimization are constructed according to simplicity levels of shape modelings with structural characteristics and manufacturing costs which can be evaluated. Then, practical design decision making procedures from the extraction of design alternatives through the determination of detailed decision variables are described corresponding to multiphase modeling starting with simplified models and advancing to detailed models. Here, the objective function of decision making is to maximize the satisfaction level of product user. Finally, the proposed integrated design optimization method is applied to industrial robots for demonstrating the effectiveness of the method.
An Area Preserving Transformation Algorithm for Press Forming Blank Development
Authors: Nair Nirmal K. , Oliver James H.
Published: March 2021

An efficient algorithm is presented to determine the blank shape necessary to manufacture a surface by press forming. The technique is independent of material properties and instead uses surface geometry and an area conservation constraint to generate a geometrically feasible blank shape. The algorithm is formulated as an approximate geometric interpretation of the reversal of the forming process. The primary applications for this technique are in preliminary surface design, assessment of manufacturability, and location of binder wrap. Since the algorithm exhibits linear time complexity, it is amenable to implementation as an interactive design aid. The algorithm is applied to two example surfaces and the results are discussed.
Simultaneous Kinematic and Dynamic Synthesis in the Preliminary Design of a Linkage
Authors: Krishnamachari Ramprasad , Vadde Srinivas , Allen Janet K. , Mistree Farrokh
Published: March 2021

In the early stages of project initiation, all aspects of system design may not be clearly defined. Some information might be uncertain (imprecise or vague). However, important design decisions need to be made in these stages in the presence of uncertainty. Fuzzy sets offer a useful method to represent the imprecision in such situations. Fuzzy compromise Decision Support Problems (DSPs) involving fuzzy membership functions are found to be effective in modeling this uncertainty and making decisions in such situations. A hat-shaped, piecewise linear membership function is introduced which is especially useful when the design space is not well understood. The use of a fuzzy compromise Decision Support Problem in the preliminary design synthesis of mechanical systems is illustrated using a case study involving the synthesis of a four-bar linkage.
An Efficient Technique for Computing the Sensitivities of Reciprocating Engine Dynamics to Dimensional Tolerances
Authors: Sinha A. , Gilmore B. J. , Kohli V.
Published: March 2021

An efficient method has been developed to determine the steady state response of an internal combustion engine, which is governed by a nonlinear differential equation with discontinuous forcing function due to the nature of the pressure-volume (P-V) diagram. Unlike previously reported methods for dynamically driven mechanical systems, this approach can accurately and efficiently predict the sensitivities of an engine’s output to dimensional tolerances. Hence, this technique is well suited for the development of an optimal tolerance allocation scheme based on nonlinear programming. The validity of this method which is based on the alternating frequency/time (AFT) domain technique has been established by comparison with results from numerical integration of differential equation of motion. This method directly yields the mean crank speed and Fourier coefficients of temporal variations in engine’s outputs such as crank’s speed and the driving torque.
XBB: A Blackboard System for Vehicle Suspension Tuning
Authors: Wang Nanxin , Fagan Daniel J. , Staley Scott M.
Published: March 2021

A design problem-solving system which uses Blackboard technology to couple previously independent application software packages into a common control and database structure is described. One application that has been investigated is the suspension tuning process. The process of suspension tuning is currently manpower intensive and involves trade-offs between desirable handling characteristics, noise, vibration and harshness (NVH) and packaging constraints. This paper reviews general blackboard concepts and presents an application of blackboard systems to the suspension tuning process. An application is described which couples the generic blackboard architecture with the symbolic dynamics package to help the engineer specify performance measures and constraints, and control the overall analysis process.
Using Engineering Models to Control Variability: Feasibility Robustness for Worst-Case Tolerances
Authors: Emch Gary , Parkinson Alan
Published: March 2021

Engineering models can and should be used to understand the effects of variability on a design. When variability is ignored, brittle designs can result that fail in service. By contrast, robust designs function properly even when subjected to off-nominal conditions. There is a need for better analytical tools to help engineers develop robust designs.

In this paper we present a general method for developing designs that are robust to variability induced by worst-case tolerances. The method adapts nonlinear programming techniques in order to determine how a design should be modified to account for variability. We show how this can be done with second order, or even exact, worst-case tolerance models. Results are given for 13 test cases that span a variety of problems. The method enables a designer to understand and account for the effects of worst-case tolerances, making it possible to build robustness into an engineering design.
Five-Axis Constrained and Optimal Orientation Planning
Authors: Haghpassand Khorssand
Published: March 2021

The five-axis constrained and optimal orientation planning is formulated as a design optimization problem that incorporates the process machine’s kinematic constraints with the workpiece and tool geometry, to obtain a constrained setup orientation which exploits the maximum capabilities of existing machines. This work will introduce this problem, and will obtain the setup orientation for two different types of rotation structures, i.e., tool rotation and table rotation in O(N) time. Further, the obtained constrained setup orientation, will be augmented to incorporate the workpiece surface magnitude, along with different machine rotation structures, to obtain an optimal setup orientation for different machine rotation structures. The drilling process is also introduced and formulated as additional constraints to the optimization problem.

The primary application of the introduced algorithms, is the machining process, where, they can efficiently reduce the number of tool motions and surface finishing processes. However, the solution is very suitable for many manufacturing applications, such as inspection, assembly, robotics, painting, welding, aerospace, electronic surface mount technology, and etc.
Hybrid Approach for Optimal Nesting Using a Genetic Algorithm and a Local Minimization Algorithm
Authors: Fujita Kikuo , Akagi Shinsuke , Hirokawa Noriyasu
Published: March 2021

In layout design problems including blank nesting, the positions and directions of layout elements must be determined so as to minimize the total space. It is difficult and computationally time-consuming to find the optimal solution for such layout problems, because they include a lot of underlying combinational conditions. In this paper, we present an approach for optimal nesting by combining a genetic algorithm and a local minimization algorithm. In the approach, the genetic algorithm is used for handling the combinations which are represented in the string, and the local minimization algorithm is used for determining the embodiment layout under the fixed combinations so as to minimize the scrap volume which is corresponding to the fitness value in the genetic algorithm. And we present an example for showing the effective nesting result produced by this approach.
Computer Aided Product Structure Modeling Using a DBMS
Authors: Johannesson H. L.
Published: March 2021

In the present paper a computer based method for top-down structure modeling of products is presented. A general hierarchical DBMS-based tree structure model is used. It is designed so that it can be connected to separately designed part product models, containing geometric models and references to standard component data bases and manufacturing documents. Together the presented product structure model and the part product models become a complete product model containing structural as well as geometric information.

The structure modeling is meant to be carried out as a first step during the embodiment design phase, before the parts are designed and the standard components are selected. Thus the geometric information is incomplete during the structure modeling phase.

A computer program for product structure modeling has been developed. It allows the number of hierarchical structure levels, as well as the number of objects on each level, to be chosen arbitrarily by the user. The data base management system TORNADO is used by the modeling program for building the structure model data bases. A structure modeling example is given in order to demonstrate the structure modeling procedure and the capabilities of the program.
Profile Determination and Analysis of Cylindrical Cams With Oscillating Roller-Followers
Authors: Tsay Der Min , Wei Hsien Min
Published: March 2021

A simple, integrated procedure for the profile determination and kinematic analysis of cylindrical cams with oscillating conical roller-followers is presented. Based on the theory of envelopes for a one-parameter family of surfaces, the new method can be easily utilized to determine cylindrical cam profiles once the appropriate follower motion curves are given. In addition, the kinematic characteristics such as the contact lines between the cam and the roller surfaces, the pressure angles, and the principal curvatures of the cam surface are analyzed in the design process. To illustrate the accuracy and effectiveness of the proposed design tool, the analytical expressions derived in this study are compared to those obtained by using the principle of contact point. Numerical examples are also given to show the application of this integrated approach.
NURBS Surface Reconstruction From a Large Set of Image and World Data Points
Authors: Theodoracatos Vassilios E. , Bobba Vasudeva
Published: March 2021

In this paper an approach is presented for the generation of a NURBS (Non-Uniform Rational B-splines) surface from a large set of 3D data points. The main advantage of NURBS surface representation is the ability to analytically describe both, precise quadratic primitives and free-form curves and surfaces. An existing three dimensional laser-based vision system is used to obtain the spatial point coordinates of an object surface with respect to a global coordinate system. The least-squares approximation technique is applied in both the image and world space of the digitized physical object to calculate the homogeneous vector and the control net of the NURBS surface. A new non-uniform knot vectorization process is developed based on five data parametrization techniques including four existing techniques, viz., uniform, chord length, centripetal, and affine invariant angle and a new technique based on surface area developed in this study. Least-squares error distribution and surface interrogation are used to evaluate the quality of surface fairness for a minimum number of NURBS control points.
Computations of Dual Numbers in the Extended Finite Dual Plane
Authors: Cheng Harry H.
Published: March 2021

The numerical computational aspects of dual numbers in the CH programming language are presented in this paper. Dual is a built-in data type in CH. Dual numbers and dual metanumbers are described in the extended dual plane and extended finite dual plane. The arithmetic and relational operations, and built-in mathematical functions are defined for both dual numbers and dual metanumbers of DualZero, DualInf, and DualNaN. Due to polymorphism, the syntax of dual arithmetic and relational operations, and built-in dual functions are the same as those for real and complex numbers in the CH programming language. The linguistic features and handling of user’s dual functions and dual arrays, as well as applications of dual numbers in robotics and spatial mechanisms in the CH programming language can be found in (Cheng, 1993c).
A Geometrical Solution for the Inverse Kinematics of Three Revolute Manipulators
Authors: Fichter Eugene F.
Published: March 2021

Points of intersection of a circle and a torus are used to find a solution to the inverse kinematics problem for a three revolute manipulator. Both geometrical and algebraic solution procedures are discussed. The algebraic procedure begins with a third order equation instead of the usual fourth order equation. Since the procedure is basically geometrical it lends itself to a computer implementation which graphically displays each steps in the solution procedure. The potential of this approach for both design and pedagogy is discussed.