bluuebunny/crossref_metadata_2025_split huggingface dataset:
Frequency Domain Structural Optimization of a Flexible Manipulator Incorporating a PD Controller in the Design Stage
Authors: Chang Yong Hoon , Seireg Ali 
Published: February 2021

Abstract
This study investigates the potential advantages of integrated design strategies for flexible manipulators that utilize a controller in the process of optimizing the structural design.
Clamped free and clamped mass beam models are considered in the investigation for the structural optimization with respect to natural frequencies and mass. A PD controller is utilized in the design process with several objective functions that incorporate weighted combinations of the mass of the structure, modal mass, modal stiffness, and the natural frequency of the rigid mode and the dominant natural frequency of the flexible mode. The results show that the objective function, which minimizes the mass and the product of the modal mass and modal stiffness of the rigid mode and maximize the natural frequency of the flexible mode with appropriate weighting factors, gave the best dynamic performance.
Although a two link tubular planar manipulator with a PD controller and assumed beam models for the links is considered in the optimization based on modal parameters, the reported approach can be extended to time domain optimization of multi-link spacial robots with complex structures designed to perform particular tasks.
Analysis of Hyper-Redundant Manipulators
Authors: Asl Farshid Maghami , Ashrafiuon Hashem , Nataraj C. 
Published: February 2021

Abstract
A new approach to solve the inverse kinematic problem for hyper-redundant planar manipulators following any desired path is presented. The method is singularity free and provides a robust solution even in the event of mechanical failure of some of the robot actuators. The approach is based on defining virtual layers and dividing them into virtual/real three-link or four-link sub-robots. It starts by solving the inverse kinematic problem for the sub-robot located in the lowest virtual layer, which is then used to solve the inverse kinematic equations for the sub-robots located in the upper virtual layers. An algorithm is developed which provides a singularity-free solution up to full extension through a configuration index. The configuration index can be interpreted as the average of the determinants of the Jacobians of the sub-robots. The equations for the velocities and accelerations of the manipulator are solved by extending the same approach where it is realized that the value of configuration index is critical in maintaining joint velocity continuity. The inverse dynamic problem of the robot is also solved to obtain the torques required for the robot actuators to accomplish its task. Computer simulations of several hyper-redundant manipulators using the proposed method are presented as numerical examples.
A Virtual Body and Joint for Constrained Flexible Multibody Dynamics
Authors: Bae D. S. , Han J. M. , Choi J. H. 
Published: February 2021

Abstract
A convenient implementation method for constrained flexible multibody dynamics is presented by introducing virtual rigid body and joint. The general purpose program for rigid and flexible multibody dynamics consists of three major parts of a set of inertia modules, a set of force modules, and a set of joint modules. Whenever a new force or joint module is added to the general purpose program, the modules for the rigid body dynamics are not reusable for the flexible body dynamics. Consequently, the corresponding modules for the flexible body dynamics must be formulated and programmed again. Since the flexible body dynamics handles more degrees of freedom than the rigid body dynamics does, implementation of the module is generally complicated and prone to coding mistakes. In order to overcome these difficulties, a virtual rigid body is introduced at every joint and force reference frames. New kinematic admissibility conditions are imposed on two body reference frames of the virtual and original bodies by introducing a virtual flexible body joint. There are some computational overheads due to the additional bodies and joints. However, since computation time is mainly depended on the frequency of flexible body dynamics, the computational overhead of the presented method could not be a critical problem, while implementation convenience is dramatically improved.
Dynamical Simulation of Flexible Multibody System by Using a Rigid Body Model
Authors: Pascal M. , Gagarina T. 
Published: February 2021

Abstract
The aim of this work is to show the possibility of using any dynamical codes devoted to rigid multibody systems in which the motion equations are obtained from d’Alembert Principle, for the simulation of flexible multibody systems in which the flexible components are discretized by a Rayleigh-Ritz procedure. The obtained results are a generalization of the work done in Botz and Hagedorn (1990) for planar elastic mechanisms. An application of the method is done using, as in Botz and Hagedorn (1990), the symbolic dynamical code AUTOLEV (Schaechter, Levinson and Kane 1988).
Identification of Free-Free Modes From Constrained Vibration Data for Flexible Multibody Models
Authors: Yi Tong Y. , Nikravesh Parviz E. 
Published: February 2021

Abstract
This paper presents a method for identifying the free-free modes of a structure by utilizing the vibration data of the same structure with boundary conditions. In modal formulations for flexible body dynamics, modal data are primary known quantities that are obtained either experimentally or analytically. The vibration measurements may be obtained for a flexible body that is constrained differently than its boundary conditions in a multibody system. For a flexible body model in a multibody system, depending upon the formulation used, we may need a set of free-free modal data or a set of constrained modal data. If a finite element model of the flexible body is available, its vibration data can be obtained analytically under any desired boundary conditions. However, if a finite element model is not available, the vibration data may be determined experimentally. Since experimentally measured vibration data are obtained for a flexible body supported by some form of boundary conditions, we may need to determine its free-free vibration data. The aim of this study is to extract, based on experimentally obtained vibration data, the necessary free-free frequencies and the associated modes for flexible bodies to be used in multibody formulations. The available vibration data may be obtained for a structure supported either by springs or by fixed boundary conditions. Furthermore, the available modes may be either a complete set; i.e., as many modes as the number of degrees of freedom of the associated FE model is available, or it can be an incomplete set.
Seismic Responses of Large Flexible Structure Including Contact Problem
Authors: Kuribara Hiroshi , Kobayashi Nobuyuki 
Published: February 2021

Abstract
A modeling method for the seismic response of large movable flexible structures including the contact problem between wheels attached at the bottom ends of the structure and a rail, such as a container crane and an unloader, is developed. The contact configuration and the contact force between the wheel attached at the structure and the ground, that significantly affect to the seismic response of the structure, are classified and calculated according to geometric relationships between contact judging markers defined on the wheel and the rail. From the numerical simulation using proposed method, it is clarified that the presented modeling method simulates quite well the nonlinear seismic response of the container crane including the uplifting and derailment behavior of the wheel that is obtained by results of the large scale model shaking tests.
A Numerical Algorithm for Solving Stiff ODEs and DAEs in Multibody Mechanics
Authors: Pasic Hajrudin 
Published: February 2021

Abstract
Presented is an algorithm suitable for numerical solutions of multibody mechanics problems. When s-stage fully implicit Runge-Kutta (RK) method is used to solve these problems described by a system of n ordinary differential equations (ODE), solution of the resulting algebraic system requires 2s3 n3 / 3 operations. In this paper we present an efficient algorithm, whose formulation differs from the traditional RK method. The procedure for uncoupling the algebraic system into a block-diagonal matrix with s blocks of size n is derived for any s. In terms of number of multiplications, the algorithm is about s2 / 2 times faster than the original, nondiagonalized system, as well as s2 times in terms of number of additions/multiplications. With s = 3 the method has the same precision and stability property as the well-known RADAU5 algorithm. However, our method is applicable with any s and not only to the explicit ODEs My′ = f(x, y), where M = constant matrix, but also to the general implicit ODEs of the form f (x, y, y′) = 0. In the solution procedure y is assumed to have a form of the algebraic polynomial whose coefficients are found by using the collocation technique. A proper choice of locations of collocation points guarantees good precision/stability properties. If constructed such as to be L-stable, the method may be used for solving differential-algebraic equations (DAEs). The application is illustrated by a constrained planar manipulator problem.
A Dynamic Performance Evaluation Model for Target Capture by Robot Mechanisms, With the Consideration of Structural Flexibility
Authors: Kövecses J. , Cleghorn W. L. , Fenton R. G. 
Published: February 2021

Abstract
In this paper a dynamic system consisting of a robot manipulator and a target is analyzed. The target is considered in a general way as a dynamic subsystem having finite mass and moments of inertia (e.g. a rigid body or a second robot). The situation investigated is when the robot establishes interaction with the target in such a way that it intercepts and captures a reference element of the target. The greatest attention is paid to the analysis of the phase of transition from from ‘free’ to constrained motion at the time of interception and capture (impulsive motion). Based on the use of impulsive constraints and the Jourdanian formulation of analytical dynamics, a novel approach is proposed for the modeling of target capture by a robot manipulator. The proposed approach is suitable to handle both finite and impulsive motions in a common analytical framework. Based on the dynamic model developed and using a geometric representation of the system’s dynamics, a detailed analysis and a performance evaluation framework are presented for the phase of transition. Both rigid and structurally flexible models of robots are considered. For the performance evaluation analyses, two main concepts are proposed and corresponding performance measures are derived. These tools may be used in the analysis, design and control of time varying robotic systems. The dynamic system of a three link robot arm capturing a rigid body is used to illustrate the material presented.
A Multibody Loop Constraints Approach for Modelling Cam/Follower Devices: Application in Mobile Robotics
Authors: Fisette Paul , Lipiński Krzysztof , Samin Jean-Claude 
Published: February 2021

Abstract
This paper proposes a formulation for modelling mechanisms with cam/follower type of contact using a multibody approach in relative coordinates. The proposed approach is inspired from the wheel/rail contact model developed in (Fisette, Samin, 1994) but in the present case, possible intermittent contact between the cam and the follower is considered, for generality purposes.
Loop kinematic constraints are introduced to satisfy tangent and punctual contact as long as the bodies lean against each other. The effective presence (or not) of the contact is governed by the sign of the normal constraint force which can be computed thanks to the Lagrange multipliers technique.
The above-mentioned option to kinematically constraint the bodies in their “contact phase” unavoidably leads to shift from one model to another when a contact disappears (or conversely reappears). Indeed, this increases (or decreases) the number of degrees of freedom of the current system. The control of the variable partitioning is thus absolutely necessary and is all the more complex that practical applications can contain several pairs of bodies in intermittent contact.
As regards the applications, a comparison with another multi-body formalism and an experimental validation are discussed at first. Then, the modelling and simulation of universal wheels of an omnimobile mobile robot, developed in our Division, are proposed. The latter model represents a quite original application of the proposed multibody formulation. Computations are now in progress to analyse the complete behaviour of the robot, including control performances.
A Study on the Dynamic Analysis of Flexible and Rigid Link System
Authors: Sugano Naoki , Honke Koichi , Imanishi Etsujiro , Hashimoto Kazuo 
Published: February 2021

Abstract
In this paper, the dynamic analysis of link structures including both flexible and rigid bodies is developed. The model for flexible bodies is based on FEM theory, and geometric nonlinearity effect is taken into account. Moreover, in the flexible rigid link structure, dependent variables are eliminated using topological information. The equation of the total system obtained in this study is in the form of ODE and can be solved efficiently.
Incremental Finite Element Formulations and Flexible Multibody Dynamics
Authors: Berzeri Marcello , Campanelli Marcello , Shabana A. A. 
Published: February 2021

Abstract
In this investigation, the performance of two different large displacement finite element formulations in the analysis of flexible multibody systems is investigated. These are the incremental corotational procedure proposed by Rankin and Brogan [8] and the non-incremental absolute nodal coordinate formulation recently proposed [9]. It is demonstrated in this investigation that the limitation resulting from the use of the nodal rotations in the incremental corotational procedure can lead to simulation problems even when very simple flexible multibody applications are considered.
A Large Displacement Formulation Using Euler’s Angles
Authors: Biakeu G. , Thouverez F. , Laine J. P. , Jezequel L. 
Published: February 2021

Abstract
The goal of this paper is to present a flexible multi-body formulation involving large displacements. This method is based on a separate discretisation of the kinetic and the internal energies. To introduce flexibility, we discretize the structure in elements (of two nodes): on each element of the beam discretisation, the local frame is defined using Euler’s angles. A finite element formulation is then applied to describe the evolution of these angles along the beam neutral fibre. For the kinetic energy, each element is cut into two rigid bars whose characteristics are given by a first order Taylor factorisation on the general kinetic energy expression. These bars are linked by a nonlinear relation. We obtain the equations of motion by applying the Lagrange’s equations to the system. These equations are solved using the Newmark method in dynamic and a Newton-Raphson technique while looking for a static solution. The method is then applied to very classic problems such as the curved beam problem proposed by authors such as Simo [6, 9], Lee [4] or the rotational rod presented by Avello [1] and Simo [7, 8] etc...
Multirate Integration for Multibody Dynamic Analysis With Decomposed Subsystems
Authors: Kim Sung-Soo , Freeman Jeffrey S. 
Published: February 2021

Abstract
This paper details a constant stepsize, multirate integration scheme which has been proposed for multibody dynamic analysis. An Adams-Bashforth Moulton integration algorithm has been implemented, using the Nordsieck form to store internal integrator information, for multirate integration. A multibody system has been decomposed into several subsystems, treating inertia coupling effects of subsystem equations of motion as the inertia forces. To each subsystem, different rate Nordsieck form of Adams integrator has been applied to solve subsystem equations of motion. Higher order derivative information from the integrator provides approximation of inertia force computation in the decomposed subsystem equations of motion. To show the effectiveness of the scheme, simulations of a vehicle multibody system that consists of high frequency suspension motion and low frequency chassis motion have been carried out with different tire excitation forces. Efficiency of the proposed scheme has been also investigated.
A Nonlinear Magnetic Circuit Analysis of a Permanent Magnet Biased Homopolar Bearing
Authors: Kenny Andrew , Palazzolo Alan 
Published: February 2021

Abstract
A magnetic circuit model for a homopolar magnetic bearing is presented. This model connects the fore and aft circumferential flux paths with axial flux paths through the rotor and back iron. The bias flux is provided by a circumferential permanent magnet in the back iron. Results for an analysis using the nonlinear Hyperco50 B-H curve are presented. These results are compared to the results of a three dimensional magnetostatic finite element analysis. The two analytical methods are in good agreement and show that the control flux in this type of bearing follows both circumferential and axial paths.
Application of Transfer Matrices to Non-Linear Rotor Bearing Systems
Authors: Liew A. , Feng N. S. , Hahn E. J. 
Published: February 2021

Abstract
To obtain the steady state unbalance response of rotor bearing systems, it is common to linearise the hydrodynamic bearing forces about their static equilibrium position. Such linearisation is increasingly approximate with increasing unbalance as it ignores the possibility of typical non-linear phenomena such as sub- and super-harmonic response and multi-stable response. Even in the case of mono-stable synchronous response, the amplitudes are differently attenuated as a result of non-linear effects. This paper shows how the transfer matrix approach, traditionally applied to linear systems, can be extended to evaluate the steady state response of non-linear systems, using harmonic balance to accommodate the various response harmonics. The technique is illustrated using a hydrodynamic journal bearing and a squeeze film damper as the non linear elements.
On Further Improvements in Predicting Rotor Vibration
Authors: Subbiah R. 
Published: February 2021

Abstract
Vibration is one of the primary concerns in rotating machinery. Vibration reduction will help extend turbo-machinery life and is viewed as one of the major winning points for turbine-generator (T-G) manufacturers. To better predict the level of machine vibration requires a great deal of analysis. The success of different analyses mainly rely on reliable models that are accurate and consistently verifiable by testing. Towards this objective, many researchers and businesses spent enormous amount of time and money in the development of accurate and reliable models that closely simulate reality. However, research in rotor dynamic modeling is an on-going effort. In this paper, another new modeling approach that uses strain energy is reported. This modeling technique was successfully applied for rotor torsional and lateral analyses with greater accuracy. Further, a faster and more stable solution method which uses Riccati algorithm is discussed.
On the Natural Frequency Calculation of Rotating Cantilever Uniform Beams With Coriolis Effects: A Dynamic Finite Element (DFE)
Authors: Hashemi S. M. , Richard M. J. 
Published: February 2021

Abstract
A Dynamic Finite Element (DFE) for vibrational analysis of rotating assemblages composed of beams is presented in which the complexity of the acceleration, due to the presence of gyroscopic, or Coriolis forces, is taken into consideration. The dynamic trigonometric shape functions of uncoupled bending and axial vibrations of an axially loaded uniform beam element are derived in an exact sense. Then, exploiting the Principle of Virtual Work together with the nodal approximations of variables, based on these dynamic shape functions, leads to a single frequency dependent stiffness matrix which is Hermitian and represents both mass and stiffness properties. A Wittrick-Williams algorithm, based on a Sturm sequence root counting technique, is then used as the solution method. The application of the theory is demonstrated by two illustrative examples of vertical and radial beams where the influence of Coriolis forces on natural frequencies of the clamped-free rotating beams is demonstrated by numerical results.
Measured Torsional Vibration Characteristics of a 100 Megawatt Wind Tunnel Drive Line
Authors: Corliss James M. , Sprysl H. 
Published: February 2021

Abstract
A new 100 MW (135,000 Hp) adjustable speed drive system has recently been installed in the NASA Langley National Transonic Facility. The 100 MW system is the largest of its kind in the world and consists of a salient pole synchronous motor powered by a 12-pulse Load Commutated Inverter variable frequency drive. During system commissioning the drive line torsional vibrations were measured with strain gages and a telemetry-based data acquisition system. The torque measurements included drive start-up and steady-state operation at speeds where the drive motor’s pulsating torques match the drive line’s torsional natural frequency. Rapid drive acceleration rates with short dwell times were effective in reducing torsional vibrations during drive starts. Measured peak torsional vibrations during steady-state operation were comparable to predicted values and large enough to produce noticeable lateral vibrations in the drive line shafting. Cyclic shaft stresses for all operating conditions were well within the fatigue limits of the drive line components. A comparison of the torque measurements to an analytical forced response model concluded that a 0.5% critical damping ratio was appropriately applied in the drive line’s torsional analysis.
Vibration Characteristics of a Rotor-Flexible Disk System: In Case of HDD Spindle-Motor System
Authors: Han D. C. , Choi S. H. , Park K. B. , Jung S. C. 
Published: February 2021

Abstract
In this paper we investigate the vibration characteristics of a rotor system with flexible disks. The coupled vibration mode between rotating shaft and the flexible disk are analyzed for lateral and axial vibrations respectively. Gyro and sheer effects are considered for the modeling of lateral vibrations. An assumed mode method was used for the disk modeling considering gyro effects. For a numerical example hard disk drive is considered. The natural frequencies of the motor-spindle system with flexible disk of hard disk drive was calculated and compared to the experimental data.
A Flexible Rotor on Flexible Bearing Supports: Part I — Stability
Authors: Vázquez José A. , Barrett Lloyd E. , Flack Ronald D. 
Published: February 2021

Abstract
An experimental study of the effects of bearing support flexibility on rotor stability is presented. A flexible roto supported by fluid film bearings on flexible supports was used with fifteen support configurations. The horizontal suppor stiffness was varied systematically while the vertical stiffness was kept constant. The support charactristics were determined experimentally by measuring the frequency response functions of the support structure at the bearing locations. These frequency response functions were used to calculate polynomial transfer functions that represented the support structure. Stability predictions were compared with measured stability thresholds. The predicted stability thresholds agree with the experimental data within a confidence bound for the logarithmic decrement of ±0.01. Predictions for the rotor on rigid supports are included for comparison.