bluuebunny/crossref_metadata_2025 huggingface dataset:
Zero Assignment in Vibration: With and Without Time Delay
Authors: Singh Kumar Vikram , Datta Biswa Nath , Tyagi Mayank
Published: May 2009

Control of the vibrating structures is desirable in various engineering applications for preventing fatigue and failure. It can be achieved by passive means using dynamic absorbers or by active means using sensors and actuators. In some cases, it is also not practical to apply a desirable control force in those locations at which dynamics of the structure to be controlled. In recent years, nodal control or dynamic absorption schemes are investigated in which control strategies to absorb a steady state motion of a desired location in the structure have been developed. Unlike conventional full-state feedback control which requires all the states of the system to be measured, nodal control strategy requires least numbers of sensors and actuators (depending upon the number of dynamic absorption points) for estimating the control gains and hence it may provide economical engineering solution. Nodal control problems are essentially a zero assignment problems in which a desired control is achieved by assigning zeroes to the prescribed locations in the structure. However while applying nodal control strategy by active means, small time delay from the sensors and actuators in the feedback loop is unavoidable and they influence the control gains as well as the stability of the system. In this paper we have developed nodal control strategy and obtained control gains for systems with and without time delays. Some examples related to conservative and nonconservative systems as well as realistic distributed parameter systems are presented to demonstrate the nodal control strategy and the effects of time delay on control gains.
Application of Gears With Asymmetric Teeth in Turboprop Engine Gearbox
Authors: Novikov Alexander S. , Paikin Alexander G. , Dorofeyev Vladislav L. , Ananiev Viacheslav M. , Kapelevich Alexander L.
Published: May 2009

This paper describes the research, development of the first in the world production gearbox with asymmetric tooth profiles for the TV7-117S turboprop engine. The paper also presents numerical design data related to development this gearbox.
Motorcycle Local Stability Analysis Under Acceleration and Braking by Model Linearization and Eigenproblem Solution
Authors: Catania Giuseppe , Mancinelli Nicolo`
Published: May 2009

A study on the dynamic stability of a motorcycle under severe acceleration and braking conditions is presented. The purpose is to analyze the experimentally observed oscillatory behavior, such as wheel bounce or chatter and rear suspension pitch. This phenomenon greatly affects the handling performance and the safety of sports motorcycles. A plane motion lumped parameter model of the vehicle is defined by the variational virtual work approach. Tire longitudinal forces are modeled using Pacejka’s nonlinear equations for quasi steady states; the kinematical model of the chain drive system is also included. The obtained nonlinear system of second order ordinary differential equations is linearized in symbolic form and transformed into the state space. The same equations of motion are numerically integrated in a commercial multibody code to compute the time histories simulating different maneuvers at quasi constant values of vehicle longitudinal acceleration. Local stability is evaluated via the model eigenvalues that are computed with respect to instantaneous equilibrium points evaluated by numerical integration. Root locus plots are traced to evaluate the graphical representation of damping and frequency associated with previously obtained eigenvalues, under different operating conditions. Coupling of standard key vehicle modes (front/rear wheel hop and suspension pitch) are also visualized by eigenvector animations. The influence of tire characteristics on the damping values of these key motorcycle modes is pointed out. The sensitivity of structural parameters on the stability of the lightly damped and critical modes is then discussed in detail.
Concepts for Achieving Multi-Stability in Compliant Rolling-Contact Elements
Authors: Halverson Peter A. , Howell Larry L. , Jensen Brian D. , Magleby Spencer P.
Published: May 2009

This paper describes the design of a novel multi-stable compliant mechanism capable of large angle deflections. The multi-stable COmpliant Rolling-contact Element (CORE), reduces friction, allows for large angular displacements, and requires no external force to remain in its multiple equilibrium positions. This paper develops and discusses seven methods to create multi-stable mechanisms from the CORE. These seven methods have different characteristics and advantages.
Probabilistic Analysis for Comparing Fatigue Data Based on Johnson-Weibull Parameters
Authors: Vicek Brian L. , Hendricks Robert C. , Zaretsky Erwin V.
Published: May 2009

Probabilistic failure analysis is essential when analysis of stress-life (S-N) curves is inconclusive in determining the relative ranking of two or more materials. In 1964, L. Johnson published a methodology for establishing the confidence that two populations of data are different. Simplified algebraic equations for confidence numbers were derived based on the original work of L. Johnson. Using the ratios of mean life, the resultant values of confidence numbers deviated less than one percent from those of Johnson. It is possible to rank the fatigue lives of different materials with a reasonable degree of statistical certainty based on combined confidence numbers. These equations were applied to rotating beam fatigue tests that were conducted on three aluminum alloys at three stress levels each. These alloys were AL 2024, AL 6061, and AL 7075. The results were analyzed and compared using ASTM Standard E739-91 and the Johnson-Weibull analysis. The ASTM method did not statistically distinguish between AL 6010 and AL 7075. Based on the Johnson-Weibull analysis confidence numbers greater than 99 percent, AL 2024 was found to have the longest fatigue life, followed by AL 7075, and then AL 6061. The ASTM Standard and the Johnson-Weibull analysis result in the same stress-life exponent p for each of the three aluminum alloys at the median or L50 lives.
A Survey of Positive Engagement, Continuously Variable Transmissions
Authors: Andersen Brian S. , Dalling Ryan R. , Todd Robert H.
Published: May 2009

A continuously variable transmission (CVT) is a type of transmission that allows an infinitely variable ratio change within a finite range, allowing the engine to continuously operate in an efficient or high performance range. A brief history of CVT’s is presented, including the families under which they can be categorized. A new family of CVT’s, with the classification of positive engagement, is presented. Three different published embodiments of CVT’s of the positive engagement type are presented describing a meshing problem that exists apparently regardless of the embodiment in this family. The problem is called the non-integer tooth problem and its occurrences are detailed in each of the three embodiments. Specific solutions to the problem, as embodied in each case, are presented. Two additional embodiments of the positive engagement type are also presented for comparison. These last embodiments rely on less efficient methods of power transmission but are not subject to the non-integer tooth problem.
Calculations Related to Municipal Solid Waste MSW Burning Under High Temperature Air Combustion HiTAC Conditions
Authors: Lilley David G.
Published: May 2009

New “high temperature air combustion” HiTAC technologies are evolving for the incineration of municipal solid waste for energy production and minimal pollution. As a contribution to this area of current research interest, a calculation procedure has been developed that permits rapid generation of general fuel-air combustion with many parameter variations. The program calculations are via Excel/VBA with immediate graphics of the parameter effects on the results. Thus, an extensive range of parameter effects may be quickly investigated and assessed. The very-general fuel is specified by way of its C-H-O-N-S content and additional water content and the “air” by way of the volume percent of oxygen, and the other component of “air” (nitrogen and/or carbon dioxide), each specified by the user. The temperature of each inlet (fuel and “air”) is specified by the user. The methodology and computer code takes as input also the equivalence ratio. Then, results of adiabatic flame temperature are calculated along with the equilibrium product species both with and without dissociation. Alternatively, the products temperature may be specified and the heat transfer in the combustor is then calculated. The computer code is very user friendly, with automatic nested loops for parameter variation and automatic generation of graphs, which are particularly useful in assessing the particular process under consideration. The application now is to incineration of municipal solid waste for energy production and minimal pollution. The waste may consist of a variety of specified components, including plastics and non-plastics, cellulose, cardboard, wood, etc. In the developed computer code, the choice of which components and their relative amounts is easily specified by the user.
Nonlinear Dynamics of a Gear Transmission System: Part I — Mechanism of Impacting Chatter With Stick
Authors: Luo Albert C. J. , O’Connor Dennis
Published: May 2009

In this paper, an investigation on nonlinear dynamical behaviors of a transmission system with a gear pair is conducted. The transmission system is described through an impact model with possible stick between the two gears. From the theory of discontinuous dynamical systems, the motion mechanism of impacting chatter with stick is investigated. The onset and vanishing conditions of stick motions are developed, and the condition for maintaining the stick motion is achieved as well. The corresponding physics interpretation is given for a better understanding of nonlinear behaviors of gear transmission systems. Furthermore, such an understanding may be very helpful to improve the efficiency of gear transmission systems.
Modeling and Prediction of Great Salt Lake Elevation Time Series Based on ARFIMA
Authors: Sun Rongtao , Chen YangQuan , Li Qianru
Published: May 2009

The elevation of Great Salt Lake (GSL) has a great impact on the people of Utah. The flood of GSL in 1982 has caused a loss of millions of dollars. Therefore, it is very important to predict the GSL levels as precisely as possible. This paper points out the reason why conventional methods failed to describe adequately the rise and fall of the GSL levels — the long-range dependence (LRD) property. The LRD of GSL elevation time series is characterized by some most commonly used Hurst parameter estimation methods in this paper. Then, according to the revealed LRD, the autoregressive fractional integrated moving average (ARFIMA) model is applied to analyze the data and predict the future levels. We have shown that the prediction results has a better performance compared to the conventional ARMA models.
Great Salt Lake Surface Level Forecasting Using FIGARCH Model
Authors: Li Qianru , Tricaud Christophe , Sun Rongtao , Chen YangQuan
Published: May 2009

In this paper, we have examined 4 models for Great Salt Lake level forecasting: ARMA (Auto-Regression and Moving Average), ARFIMA (Auto-Regressive Fractional Integral and Moving Average), GARCH (Generalized Auto-Regressive Conditional Heteroskedasticity) and FIGARCH (Fractional Integral Generalized Auto-Regressive Conditional Heteroskedasticity). Through our empirical data analysis where we divide the time series in two parts (first 2000 measurement points in Part-1 and the rest is Part-2), we found that for Part-2 data, FIGARCH offers best performance indicating that conditional heteroscedasticity should be included in time series with high volatility.
Practical Tuning of Fractional Order Proportional and Integral Controller (II): Experiments
Authors: Bhaskaran Tripti , Chen YangQuan , Bohannan Gary
Published: May 2009

This paper aims to apply the practical tuning procedure for fractional order proportional and integral controller (FO-PI) to two experimental platforms. The first platform is Quanser’s Heat Flow Experiment (HFE) and the second platform is the Quanser’s Rotary Flexible Joint (RFJ) Module. The fractional controllers in both cases have been digitally implemented using Oustaloup’s recursive approximation. The second system however can also be controlled with the Fractroller which uses the novel element Fractor. Practical issues are introduced and discussed and interesting experimental results are reported that could serve as sample applications of the proposed FO-PI tuning rules.
Studies on FEM Geometrical Model of Gear Machined by Pre-Grinding Hob With Protuberance
Authors: Tang Jinyuan , Zhou Changjiang , Wu Changde
Published: May 2009

Conjugate curves are cut by the different parts of a pre-grinding hob with protuberance, appearing in subsection nonlinearly, which makes the combined fillet curves difficult to describe with explicit equations and makes the tooth profile complex. Due to the complex tooth profile, the general CAD/CAE methods of geometrical modeling and structure analysis are rarely applied in the strength calculation and transmission performance study. Based on the generating principle, conjugate curve equations of the gear, cut by the pre-grinding hob, are derived. These conjugate curves cut by the different parts of the hob are solved, compressed, linked and synthesized numerically, and then the shape of complex tooth profile are calculated exactly. Combined by strong numeric calculating performance of MATLAB and the facility of ANSYS’S APDL, compositely modeling program with MATLAB full-text data files and APDL is developed based, then FEM (Finite Element Method) geometrical model of tooth profile machined by pre-grinding hob accurately established. According to the built gear model, the relations of bending strength to grinding allowance are researched. The studies show that the grinding allowance of the optimum bending strength is not in allowance value recommended by the pre-grinding JB/T Standard 7968.1-95. The surface quality of gear ignored, less pre-grinding allowance usually leads to more optimal bending strength.
System of Hobs Unification for Gear-Wheel Cutting of Worm-Type Gears
Authors: Goldfarb Veniamin I. , Trubachov Eugene S. , Lunin Stepan V.
Published: May 2009

Unlike spur and helical gears, manufacturing of worm gears typically requires unique hob cutters for each design. The proposed method allows using the same hob cutter for different designs. The method is supported by tooth-cutting and tooth-contact simulation software. It has been applied to worm, worm face and high ratio hypoid gears. Using the method during design stage provides digital optimization of the tooth contact and prediction of allowable misalignments. The authors are presenting practical methodology and examples of using the software. In practice the proposed method can be described in simple words: Never buy a new worm hob cutter again if you already have a set of unified cutters and the software. Small and middle size companies will gain the most economical advantage if to use the proposed method and software. Larger companies can also benefit from the method by significant reduction of the product development time.
On the Coupling Between Torsional and Lateral Vibrations in a Rotor Dynamic System With Set-Valued Friction
Authors: van de Wouw N. , Nijmeijer H. , Mihajlovic´ N.
Published: May 2009

In this paper, we analyze the interaction between friction-induced vibrations and self-sustained lateral vibrations caused by mass-unbalance in an experimental rotor dynamic set-up. This study is performed on the level of both numerical and experimental bifurcation analyses. The results show that a higher level of mass-unbalance, which generally increases the lateral vibrations, can have a stabilizing effect on the torsional dynamics, i.e. friction-induced limit cycling can disappear. Moreover, the analyses provide insight in the fundamental mechanisms causing self-sustained oscillations in rotor systems with flexibility, mass-unbalance and discontinuous friction which supports the design of such flexible rotor systems.
Geometry and Kinematic Analysis of a Redundantly Actuated Parallel Mechanism for Rehabilitation
Authors: Saglia Jody A. , Dai Jian S.
Published: May 2009

This paper presents the geometry and the kinematic analysis of a parallel manipulator developed for ankle rehabilitation, as the beginning of a control system design process. First the geometry of the parallel mechanism is described, secondly the equations for the inverse and the forward kinematics are obtained, then the forward kinematics is analyzed in order to define all the possible configurations of the moving platform. Finally the Jacobian matrix of the rig is obtained by differentiating the position equations and the singularities are investigated, comparing the non-redundant and redundant type of mechanism.
The Generalized-α Scheme as a Linear Multistep Integrator: Towards a General Mechatronic Simulator
Authors: Bru¨ls Olivier , Arnold Martin
Published: May 2009

This paper presents a consistent formulation of the generalized-α time integration scheme for mechanical and mechatronic systems. The algorithm can deal with a non-constant mass matrix, controller dynamics, and kinematic constraints. The theoretical background relies on the analogy with linear multistep formulae, which leads to elegant results related with consistency, order conditions for constant and variable step-size methods, as well as global convergence. The algorithm is applied for the simulation of a vehicle semi-active suspension.
Viscoelastic Properties of a Cultured Osteoblast Under Adhesive Condition
Authors: Onishi Takafumi , Shiraishi Toshihiko , Morishita Shin , Takeuchi Ryohei
Published: May 2009

Bone cells are adaptive to surrounding mechanical conditions. Osteoblasts, one of bone cells, have been reported to be sensible to mechanical stimulation and change the generated bone mass. Viscoelastic properties of such cells are predicted to be related to this phenomenon in the view of mechanical dynamics. In order to find the effective stimulation on the bone formation, it is necessary to understand the viscoelastic properties of the cells. Especially in the case of bone cells, it is important to consider their adhesive condition because they attach on surfaces of bone matrices. In this study, we measured tensile, static and dynamic viscoelastic properties of a cultured osteoblast, MC3T3-E1, under adhesive condition. Using these experimental results, we derived a model for viscoelasticity of the cell and identified the value of each element in this model. The cells were seeded on a glass plate in a petri dish. After the cells were cultured for one day and adhered on the glass plate, it was vertically raised and fixed on a piezo actuator. The center of the cell surface was aspirated with an L-shaped micropipette to be held. The glass plate was moved with manual, an electric motor or the piezo actuator according to the types of tests. The load applied to the cell was obtained by measuring the deflection of the micropipette whose spring constant was calibrated after each test. Deflection of the micropipette and elongation of the cell were measured by captured image during the test. As a result, the viscoelasticity of the cells was measured and modeled, and the value of each element in this model was identified.
An Indoor Spread Spectrum Acoustic Ranging System
Authors: Drysdale Graeme R. , Dai Liming , Palmer Ron J.
Published: May 2009

The design of a spread spectrum acoustic ranging system is presented as an alternative for transmitting and receiving positioning information [1]. Six pseudonoise codes, four maximum length and two Gold codes, are tested in a high multipath indoor environment to assess the system’s accuracy. Range measurements are made in 1 m intervals from 1 to 10 m and the results are shown for a maximum length code and a Gold code which is the modulo-2 addition of two maximum length codes. The average errors are bound between 6 and 20 cm. It appears multipath interference provides the largest contribution to the range error.
Synthesis of Perfect Spring Balancers With Higher-Order Zero-Free-Length Springs
Authors: Soethoudt Bram , Herder Just L.
Published: May 2009

Static balancing is a well-known technique in mechanism synthesis to achieve equilibrium throughout the range of motion, for instance to eliminate gravity from the equations of motion. Another application of static balancing is in spring-to-spring balancing where the influence of n springs on the mechanism behavior (e.g. input torque) are balanced by m other springs (n and m both non-zero positive integers). In this category of balanced mechanism, design methodology and examples exist based on zero-free-length springs, i.e. linear extension springs in which the force is proportional to the length of the spring, rather than to its elongation. The present paper will present for the first time the design of perfect spring-to-spring balancers with higher-order zero-free-length springs, i.e. springs in which the force is proportional to a (positive integer) power of its length. A general approach will be given together with four new mechanisms incorporating springs ranging from two third-order springs in the simplest example, to four equal thirteenth order springs plus one first order spring in the most complex example.
Computational Elastic Rod Model Applied to DNA Looping
Authors: Lillian Todd D. , Perkins N. C. , Goyal S.
Published: May 2009

DNA is a long flexible biopolymer containing genetic information. Proteins often take advantage of DNA’s inherent flexibility to perform their cellular functions. Here we present selected results from our computational studies of the mechanical looping of DNA by the Lactose repressor protein. The Lactose repressor resides in the bacterium E. coli and deforms DNA into a loop as a means of controlling the production of enzymes necessary for digesting lactose. We examine this looping process using a computational rod model [1–3] to understand the strain energy and geometry for the resultant DNA loops. Our model captures the multiple looped conformations of the molecule arising from both multiple boundary conditions and geometric nonlinearities. In addition, the model captures the periodic variation of strain energy with base-pair length as suggested by repression experiments (see, for example, [4, 5]).
Equilibrium, Stability, and Robustness in Underactuated Grasping
Authors: Kragten Gert A. , Herder Just L.
Published: May 2009

This paper aims to develop a performance measure for underactuated grasping devices, which is useful in making design decisions to obtain an optimally performing device. Underactuated fingers, defined as having more degrees of freedom than degrees of actuation, intrinsically adapt their shape to the object. However, the equilibrium configuration and grasp forces of these fingers are not fully controllable, which may limit their performance. The grasp performance measure defined in this paper consists of three aspects: (1) the ability to grasp objects, which is limited by the equilibrium conditions and constraints of both the underactuated fingers and the freely movable object; (2) the grasp stability, which takes the passive compliance of the fingers into account; (3) the ability to oppose disturbance forces on the grasped object by passively adapting the frictional grasp forces. This measure was applied to optimize a planar grasping device with two underactuated fingers, each consisting of two phalanges, able to grasp freely moving circular objects.
A Hybrid Fuzzy Logic Approach for 8-Bit Embedded Control Applications
Authors: Mountain Jeffrey R.
Published: May 2009

The real-time implementation of fuzzy logic algorithms in embedded systems typically uses two approaches: employ fuzzy specific processing hardware or adapt standard embedded controllers to implement the fuzzy logic inference process. While high speed applications may require using the more sophisticated hardware, most embedded control applications do not have such processing speed demands, nor can they justify the added expense associated with the fuzzy enhanced processing engines. A review of embedded controller fuzzy logic implementations indicates a preference for 16-bit architectures; devoting significant processing resources to perform fuzzification, rule application, and defuzzification during real-time operation. While these approaches remain faithful to the foundations of fuzzy logic control, devoting processor resources to fuzzy specific tasks can limit a controller’s ability to handle peripheral tasks, such as man-machine I/O interface. This paper describes a simplified, hybrid approach suitable for standard 8-bit microcontrollers. The generic nature of the approach allows the methodology to be readily applicable to many single input, single output systems. This paper describes the hybrid fuzzy logic approach, which is placed in context using a proof-of-concept motor speed application. System performance data and notable limitations of the prototyped system are also described.
Supervised Bayesian Models to Carry Out Kansei Engineering of Car Dashbaords
Authors: Ben Ahmed Walid , Yannou Bernard
Published: May 2009

The issue of this paper is the use of perceptual evaluations of products as a simulation platform for improving decision making in the design process of a new product. In previous work, we proposed bayesian kansei models using unsupervised learning of relationship between perceptual evaluation of a family of similar products and technical characteristics of these products. We showed the main advantages of such bayesian models compared to other techniques in that they are not opaque to the designer and they can be easily used in compound analysis/synthesis scenarios. The objective of this paper is to show the limits of such unsupervised bayesian kansei models and to propose the use of complementary supervised bayesian kansei models. We show that these models are more accurate to carry out a local optimization of a design.
Compliant Mechanisms Formed From Shaped Wire
Authors: Pendleton Tyler M. , Jensen Brian D.
Published: May 2009

This paper presents an alternative to fabrication methods commonly used in compliant mechanisms research. This method integrates torsional springs made of formed wire into compliant mechanisms. In this way the desired force, stiffness, and motion can be achieved from a single piece of formed wire. Two techniques of integrating torsion springs are fabricated and modeled: helical coil torsion springs and torsion bars. Because the mechanisms are more complex than ordinary springs, simplified models, which aid in design, are presented which represent the wireform mechanisms as rigid body mechanisms using the pseudo-rigid-body model. The method is demonstrated through the design of a mechanically tristable mechanism. The validity of the simplified models is discussed by comparison to finite element models and, in the case of the torsion bar mechanism, to experimental measurements.
Reverse Engineering of Geometric Surfaces Using Tabu Search Optimization Technique
Authors: Youssef Ayman M. A. , Nassef Ashraf O. , Metwalli Sayed M.
Published: May 2009

Creating unavailable geometric models from existing parts plays an important role in the process of reverse engineering, for which the accuracy and fitting time of the created models are important factors. This paper proposes the use of Tabu Search (TS) technique in the optimal fitting of NURBS (Non Uniform Rational B-Spline) surfaces to laser-scanned point clouds of free-form surfaces for existing parts. The fitting process involves the initial estimation of the NURBS surface control points using least-squares approximation, followed by optimization of NURBS weights to minimize fitting error. Optimization is performed using a hybrid coding scheme, namely; Modified Continuous Reactive Tabu Search (M-C-RTS), in which a combinatorial optimization component, based on Reactive Tabu Search (RTS), co-operates with Sequential Quadratic Programming (SQP), as a local minimizer. The developed fitting algorithm was applied to a number of simulated free-form surfaces in addition to a laser-scanned PC mouse. Implementation was carried out using MATLAB software and the results were compared to those obtained using Genetic Algorithms (GAs) in an earlier publication. The results show the superiority of the proposed algorithm to the GA-based method with respect to the number of objective function evaluations (about 50% reduction). In addition to this time saving achievement, and surprisingly, M-C-RTS proved to be capable of finding better solutions than GAs.
Synthesis of Multi-Stable Equilibrium Compliant Mechanisms Using Combinations of Bi-Stable Mechanisms
Authors: Oh Young Seok , Kota Sridhar
Published: May 2009

This paper presents a mathematical approach to synthesizing a multi-stable behavior by combining multiple bi-stable equilibrium mechanisms in series. Behavior of a bi-stable compliant mechanism, in general, is highly non-linear. Combinations of such non-linearities to capture the behavior of multi-stable (more than two stable positions) mechanisms can be very challenging. We present a simplified mathematical scheme to capture the essential parameters of bi-stability such as force-thresholds that cause the jump to next stable position etc. to derive multi-stable behavior. This mathematical simplification enables us to characterize bi-stable mechanisms using piecewise lower-order polynomials and synthesize multi-stable mechanisms through combination of bi-stable behaviors in series. We present two case studies of combinations of two and three bi-stable behaviors to generate mechanisms with four and five stable positions respectively. A design example of a quadri-stable equilibrium rotational compliant mechanism consisting two bi-stable sub-mechanisms is presented to demonstrate the effectiveness of the approach.
On the Dynamic Characterization for Flywheel Touchdown Bearing System Design
Authors: Sun Guangyoung , Jansen Ralph , Duffy Kirsten
Published: May 2009

NASA Glenn Research Center has been developing efficient flywheel batteries for a variety of space power applications, which provide the advantages of higher energy density, longer life span, and lower maintenance over electrochemical batteries as a next-generation energy storage device. As a component of enhancing the reliability of a flywheel module, the touchdown bearing system plays a crucial role in case of the malfunction or failure of magnetic bearings. In this paper, a design for touchdown support system has been proposed, a mathematical model for characterizing the dynamic behavior for the touchdown bearing system developed and then the numerical analysis using key design parameters followed. Transient simulations for the flywheel 1G delevitation onto the touchdown bearings suggest a design guide for the touchdown system, which maximizes the minimum air gap at the magnetic bearings and minimizes the dynamic loading as well as allows a safe flywheel rotor landing.
Kinematics, Dynamics and Control of a Planar 3-DOF Tensegrity Robot Manipulator
Authors: Vasquez Rafael E. , Correa Julio C.
Published: May 2009

In this paper the kinematic and the dynamic analysis, and a nonlinear control strategy for a planar three-degree-of-freedom tensegrity robot manipulator are addressed. A geometric method is used to obtain the set of equations that describe the position analysis. Initially, solutions to the problems concerning forward and reverse kinematic analysis are presented; then, the forward velocity coefficients matrix is obtained analytically. The Lagrangian approach is used to deduce the dynamic equation of motion and its main properties are described using the nonlinear control system theory. Finally, a feedback-linearization-based nonlinear control scheme is applied to the mechanism to follow a prescribed path in the Cartesian coordinate system. The obtained results show that lightweight mechanisms which incorporate tensegrity systems could be used in a positioning problem.
Experimental Validation of Nonlinear Compliant Contact Force Models
Authors: Zhang Yuning , Sharf Inna
Published: May 2009

Contact dynamics modeling continues to be an intensive research area with new applications of contact dynamics simulation arising in engineering practice. One approach to normal contact force modeling that has gained significant popularity is the compliant model in which the contact force between two objects is defined explicitly as a function of local deformation and its rate. Probably the most well-known model in this category is the Hunt and Crossley model, which employs a nonlinear damping term to model the energy dissipation during contact, with the damping coefficient related to the coefficient of restitution. This model prompted several investigations on how to evaluate the damping coefficient, in turn resulting in several variations on the original Hunt-Crossley model. In this paper, the authors aim to experimentally validate the Hunt-Crossley type of nonlinear contact force models and furthermore, to compare the experimental results to the model predictions obtained with different values of the damping coefficient. The paper reports our findings from the sphere to plate impact experiments, conducted for a range of initial impacting velocities, with measurements of impact forces and accelerations. The experimental forces are compared to those predicted from the contact dynamics simulation of the experimental scenario. The experiments, in addition to generating novel impact measurements, provide a number of insights into both the study of impact and the impact response.
Modeling and Control of Nonlinear Series Elastic Actuator
Authors: Basafa Ehsan , Salarieh Hassan , Alasty Aria
Published: May 2009

Series Elastic Actuators are force actuators with applications in robotics and biomechanics. In linear Series Elastic Actuators, a large force bandwidth requires a stiff sensor (spring), but the output impedance puts an upper limit on this parameter, therefore selecting the proper spring is difficult in these actuators. In this paper, Series Elastic Actuator is modeled with a nonlinear, stiffening spring and controlled using the Gain Scheduling method. Simulations show that both linear and nonlinear models have similar force bandwidths, but the nonlinear one shows much lower output impedance. Hence, the choice of spring for actuator design is an easier task than that of the linear model. Also, as a force-augmenting device for the knee joint in normal human gait, the nonlinear model acts better in simulations.
Postbuckling and Free Vibrations of Composite Beams
Authors: Emam Samir A. , Nayfeh Ali H.
Published: May 2009

An exact solution for the postbuckling configurations of composite beams is presented. The equations governing the axial and transverse vibrations of a composite laminated beam accounting for the midplane stretching are presented. The inplane inertia and damping are neglected, and hence the two equations are reduced to a single equation governing the transverse vibrations. This equation is a nonlinear fourth-order partial-integral differential equation. We find that the governing equation for the postbuckling of a symmetric or antisymmetric composite beam has the same form as that of a metallic beam. A closed-form solution for the postbuckling configurations due to a given axial load beyond the critical buckling load is obtained. We followed Nayfeh, Anderson, and Kreider and exactly solved the linear vibration problem around the first buckled configuration to obtain the fundamental natural frequencies and their corresponding mode shapes using different fiber orientations. Characteristic curves showing variations of the maximum static deflection and the fundamental natural frequency of postbuckling vibrations with the applied axial load for a variety of fiber orientations are presented. We find out that the line-up orientation of the laminate strongly affects the static buckled configuration and the fundamental natural frequency. The ratio of the axial stiffness to the bending stiffness is a crucial parameter in the analysis. This parameter can be used to help design and optimize the composite beams behavior in the postbuckling domain.
Internal Resonances in Microbeam Arrays Subject to Electrodynamical Parametric Excitation
Authors: Gutschmidt Stefanie , Gottlieb Oded
Published: May 2009

The dynamic response of parametrically excited microbeam arrays is governed by nonlinear effects which directly influence their performance. To date, documented theoretical models consist of lumped-mass systems which do not resolve the spatio-temporal interaction of the individual elements and reproduce measured array response only qualitatively. A consistent nonlinear continuum model is derived using the extended Hamilton’s principle to capture the salient dynamic features of an array of N nonlinearly coupled microbeams. The nonlinear dynamic equations of motion are solved analytically using the asymptotic multiple-scales method for the weakly nonlinear system. Stability analysis of the resulting coexisting solutions enables construction of a comprehensive bifurcation structure for the system. Analytically obtained results for the weakly nonlinear limit of two coupled microbeams are verified numerically.
Virtual Studio System and Facial Emotion-Expression
Authors: Aoyama Hideki , Haginoya Ryo , Umezawa
Published: May 2009

Directors of TV programs, commercial programs, etc. usually convey their intentions to actors and production staffs using storyboards. However, it is difficult to perfectly and strictly convey director’s intentions to them since storyboards indicate only moment images of scenes. Directors then need much time to convey their intentions. In order to solve such problems, a system to automatically generate animation storyboards: moving images, have been developed in this study. The system is called “Virtual Studio System”. The system analyzes a scenario written by a director in natural language and automatically creates moving images. The system enables one to easily change the result: moving images, by changing the scenario in natural language. In addition, a method to make facial expressions of characters in the virtual system has been developed. With this system, anyone can easily make and edit animation storyboards representing a scenario.
Virtual Reality Systems: A Method to Evaluate the Applicability Based on the Design Context
Authors: Mengoni Maura , Germani Michele , Bordegoni Monica
Published: May 2009

Virtual Reality (VR) technologies provide novel modes of human computer interaction that can be used to support industrial design processes. The integration can be successful if supported by a method to qualify, select and design the VR technologies according to the company’s requirements in order to improve collaboration in extended enterprises and timesaving. The aim of the present work is the definition of a method to translate the company’s expectations into heuristic values that allow the benchmarking of VR systems. The method has been tested on a real test case.
A New Approach on Object Slippage Control in a Cooperating Manipulators System
Authors: Hadian Jazi Shahram , Keshmiri Mehdi , Sheikholeslam Farid
Published: May 2009

Considering slippage in the end-effectors of a set of two cooperating manipulators grasping an object, this paper presents a new dynamic modeling and control synthesis of grasping phenomenon. This dynamic modeling is based on a new formulation for frictional contact where equality and inequality equations in the standard Coulomb Friction model are converted all to a single second order differential equation with switching coefficients. Accuracy of the friction model is verified by comparing its results with those of SimMech. Then equations of motion are reduced to conventional form for nonconstrained system. Assuming the new reduced order system to be BIBO, internal stability of the whole system is analyzed. In the control synthesis of the system a multi phase controller is utilized to control the trajectory tracking of the object as well as slippage control of the end-effectors on the object surfaces. For the proposed controller, a proof is given for system stability and its performance and robustness are shown numerically. The results show superiority of the method and its desirable and excellent performance.
A Three-Dimensional Generalization of Instant Center Method Using Line Geometry
Authors: Baroon Jasem , Ravani Bahram
Published: May 2009

For a planar motion of a body, there exists an instantaneous center of zero velocity or what is known as the centrode. In three-dimensions, the same is represented by the instantaneous screw axis. In two dimensions, however, there is a geometric method of construction the instant center by using the velocity vectors of two points of the body. The instant center is the point of intersection of the lines perpendicular to the two velocity vectors. This type of construction, however, did not exist for the instantaneous screw axis. In this paper, we present such a geometric construction for the instantaneous screw axis using line geometry.
Combined Application of Emotional Engineering and System Engineering in the Development of a New Motorcycle Paradigm for 2020
Authors: van der Meer Bastiaan , Horva´th Imre , van der Vegte Wilhelm , Ohta Hiroshi
Published: May 2009

This paper reports on a complex approach to including emotional engineering and system engineering in the development of a concept of a future product. The concrete problem was to develop a new product paradigm and a feasible concept of a branded motorcycle for 2020. The new product paradigm has been developed by considering some trend-setter new developments in the field of driving, moving, and control systems for motorcycles. Emotional engineering was used to include the opinion of the potential users in the formation of the new paradigm and to provide the users with comfort, pleasure, and emotional sensations. System engineering made it possible to find realistic solution elements for the implementation, and to develop a feasible product concept based on this paradigm that fulfils the functional, utility, and emotional expectations of the users. The information and knowledge intensive sub-processes of emotional and system engineering have been supported by design inclusive research. This methodological approach included the evolving product paradigm, and its various representations and prototypes as a research means. Design inclusive research consisted of an exploration research part, a concept and prototype development part, and a confirmative research part. Using this framing methodology, designers can get a better idea of what preferences their target groups have and understand what can be successful on the market. The results achieved are being used as input for further strategic investigation by the concerned companies.
Non-Smooth Flexible Multi-Body Systems With Non-Primitive Contours
Authors: Zander Roland , Ulbrich Heinz
Published: May 2009

This article shows the formulation of flexible multi-body systems for contact dynamics. A short introduction is given on the mathematical formulation of non-smooth multi-body systems, which are marked by jumps within the system velocities. The paper focuses on the geometrical description of flexible components: these can be modeled directly in the system or gained from external pre-processes like for example finite element codes. Since the contact algorithms require contour information, the body shapes need to be interpolated independent from the description used for dynamics within external codes. The interpolation can respond especially on the requirements of contact simulations. Discrete nodes of the external mesh are used as reference and interface for contacts. Two examples show the potential of the formulations: an eccentrically excited machine on elastic ground and a bunch of dice falling into an elastic basin.
A Direct Analysis of Nonlinear Systems With External Periodic Excitations Via Normal Forms
Authors: Gabale Amit P. , Sinha S. C.
Published: May 2009

This study presents a direct methodology for the analysis of nonlinear dynamic systems with external periodic forcing via an application of the theory of normal forms. Rather than introducing a new state variable to reduce the problem to a homogenous one, we apply a set of time-dependant near-identity transformations to construct the normal forms. The proposed method can be applied to time-invariant as well as time varying systems. After discussing the time-invariant case, the methodology is extended to systems with time-periodic coefficients. The time periodic case is handled through an application of the Lyapunov-Floquet (L-F) transformation. It has been shown that all resonance conditions can be obtained in a closed form. Further, for time invariant case, if the superharmonic response is dominant, a simple modification can be made to yield accurate results. An example for each type of system, viz., constant coefficients and time-varying coefficients is included to demonstrate effectiveness of the method. It is observed that the linear parametric excitation term need not be small as generally assumed in perturbation and averaging techniques. The results obtained by proposed method are compared with numerical solutions.
Synthesis of Planar Compliant Mechanisms
Authors: Mengesha Tewodros E. , Lu Kerr-Jia
Published: May 2009

This paper introduces a compliant mechanism design method that guarantees structural connectivity and planarity of the resulting design. The structural connectivity is ensured by a path-representation, while a coin-optimization process is introduced to verify the planarity of the design. A non-planar design can be “planarized” by a coin-repair process, thus all non-planar designs can be effectively excluded from the solution space. The discrete topology optimization problem is incorporated in a genetic algorithm. The resulting topology is further processed through size and shape optimization for improved stress distribution. The results from two benchmarking design examples showed that the proposed method is capable of producing planar mechanisms in a reasonable amount of computing time. The presented design method will be incorporated into an on-going research in the design of biomimetic wings for Micro-Aerial Vehicles (MAVs).
Nonlinear Parametric Resonances in a Stay of the Iroise Cable-Stayed Bridge: Analytical Model and Experiments
Authors: Boujard Olivier , Pernot Ste´phane , Berlioz Alain , Lamarque Claude
Published: May 2009

Recent experimental campaigns led on the Iroise cable stayed bridge near Brest, France, revealed repeated vibratory events in some cable stays likely to provoke durability problems. A spectral analysis emphasized two regimes in which either the fundamental or the third cable mode were excited. Yet, wavelet scalograms of tests allowed to exhibit a global pylon mode excited by traffic environment through deck-cable-tower interaction and which again excites local cable modes by means of a nonlinear parametric resonance mechanism with vertical bending modes of the girder. Preliminary results are introduced as an attempt to explain such a scenario.