bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of Low-Cycle Bending Fatigue of AISI 9310 Steel Spur Gears
Authors: Handschuh Robert F. , Krantz Timothy L. , Lerch Bradley A. , Burke Christopher S.
Published: May 2009

An investigation of the low-cycle bending fatigue of spur gears made from AISI 9310 gear steel was completed. Tests were conducted using the single-tooth bending method to achieve crack initiation and propagation. Tests were conducted on spur gears in a fatigue test machine using a dedicated gear test fixture. Test loads were applied at the highest point of single tooth contact. Gear bending stresses for a given testing load were calculated using a linear-elastic finite element model. Test data were accumulated from 1/4 cycle to several thousand cycles depending on the test stress level. The relationship of stress and cycles for crack initiation was found to be semi-logarithmic. The relationship of stress and cycles for crack propagation was found to be linear. For the range of loads investigated, the crack propagation phase is related to the level of load being applied. Very high loads have comparable crack initiation and propagation times whereas lower loads can have a much smaller number of cycles for crack propagation cycles as compared to crack initiation.
Interactions Between Backlash and Bearing Clearance Nonlinearity in Geared Flexible Rotors
Authors: Gu¨rkan N. Ersan , O¨zgu¨ven H. Nevzat
Published: May 2009

In this study, the interactions between backlash, bearing clearance and bearing flexibility are studied in geared flexible rotors. For this purpose, the non-linear mathematical model developed in a recent previous study for geared rotors on flexible bearings is extended further to handle clearance nonlinearity in bearings. The model consists of elastic shafts on elastic bearings with clearance, and coupled by a non-linear gear mesh interface. Shafts are modeled by using finite elements. The mathematical model includes the axial loading on shafts, rotary inertia, material damping of shafts, backlash nonlinearity of gear mesh and flexible bearings with clearances nonlinearity. The model considers also the effects of gear errors and profile modifications. The excitation effect of time varying mesh stiffness is indirectly included into the analysis through a periodic displacement representing loaded static transmission error (STE). STE input is modeled by the highest n harmonic terms of the Fourier series representation of the measured or calculated data. The model developed is believed to be one of the most advanced ones: It includes several linear and non-linear effects and capable of handling various different gear-rotor-bearing configurations. Through several case studies, the combined effects of backlash, bearing clearance, and bearing flexibility on dynamic mesh force and bearing loads are studied.
Energy Regenerative and Active Control of Automobile Suspension
Authors: Okada Yohji , Suzuki Ken-Ichi , Kondo Ryou
Published: May 2009

A new energy regenerative and active control of automobile suspension is introduced. It is intended to improve vibration reduction capability using the regenerated energy. A PM type linear AC motor is used as an energy regenerative and active control suspension. This idea is applied to a quarter-car model and vibration control is performed. Energy regenerative and active control modes can not operate at the same time. A new control law is introduced to switch control modes and to follow the ideal force. The ideal force is calculated using the LQ control theory. The PWM switches are driven in proportion to the difference between the ideal control force and the actuator force using the modulation circuit. Experimental setup is made to confirm the proposed technique and the damping capability is tested.
The Effect of Density on the Bending Fatigue of Powdered Metal Gears
Authors: Alven David A. , Imbrogno Peter G.
Published: May 2009

The bending fatigue properties of powder metal (P/M) gears as a function of density were investigated. SAE-AISI 4600 based steel gears were manufactured using various powdered metal processes. The processes used were press and sinter, double press and double sinter, surface densify, and powder forge (P/F). The resulting gears were then subjected to single tooth bending fatigue testing and compared with 4600 based wrought gears. It was found that the density of the P/M part had a significant influence on the bending fatigue properties. When compared to the wrought material, a P/M gear of equivalent density was found to have similar bending fatigue properties.
Domains and Types of Aeroelastic Instability of Slender Beam
Authors: Na´prstek Jirˇi´
Published: May 2009

Slender structures exposed to a cross air flow are prone to vibrations of several types resulting from aeroelastic interaction of a flowing medium and a moving structure. Aeroelastic forces are the origin of nonconservative and gyroscopic forces influencing the stability of a system response. Conditions of a dynamic stability loss and a detailed analysis of a stability domain has been done using a linear mathematical model. Response properties of a system located on a stability boundary together with tendencies in its neighborhood are presented and interpreted from physical point of view. Results can be used for an explanation of several effects observed experimentally but remaining without theoretical explanation until now.
Integrated Excitation Models of the Helical Gear System
Authors: Nishino Takayuki
Published: May 2009

The vibration of the helical gear system is generated by three kinds of excitation. The first cause is a displacement excitation due to the tooth surface error. The second is a parametric excitation by the periodical change of the tooth mesh stiffness. The third is a moving load on the tooth surface during the progress of mesh of the teeth. In mesh of a pair of helical gears, the composite load of the distributed load along a contact line moves its operating location from one end of face width to the other end during the process of mesh progress. This moving load causes fluctuation of bearing load that excites the housing. Therefore, it is important to treat gear mesh excitation as a moving load problem. For this purpose, two kinds of mesh models, in which the three different types of excitations above are incorporated, are proposed. In the first model, a pair of gear tooth is represented by the multiple springs and the moving load can be taken into account by the multiple mesh excitation forces that have the phase differences from each other. The second one incorporates the excitation moment into the single tooth spring model. Then, response analysis is done for a simple gear-shaft model. As the result, the moving load causes vibration with non-coupled or independent modes between the drive and driven shaft. Thus, the effectiveness of the proposed method is established.
Study on the Application of Magnetorheological Damper in Chaotic Vibration Control
Authors: Liu Shuyong , Zhu Shijian , Yu Xiang , Wang Jingjing
Published: May 2009

The nonlinear vibration isolation system works in a chaotic state when its parameters are in chaotic range. Under single frequency harmonic excitation, the output of this system is broad spectrum response, and thus the chaotic vibration isolation system is applied to control line spectra of the warship water-born noise. The passive vibration isolation system, however, cannot change the parameters when the work condition of isolated equipments is varied, and it is difficult to ensure that the system is in chaotic state. In order to adjust the system parameter on line, the magnetorheological damper can be used to control chaos in nonlinear vibration isolation systems. The system model with magnetorheological damper is presented in this paper, and then the simulation is carried out. Results show that the magnetorheological damper can be used to reduce the amplitude of the chaotic vibration when voltage is applied to the MR. When the voltage is increased, the system can exhibit period behaviour. This is a new method for chaos control.
Study on the Mechanism for Line Spectrum Reduction in Nonlinear Vibration Isolation System
Authors: Wang Jing-Jing , Zhu Shi-Jian , Liu Shu-Yong
Published: May 2009

The chaotic response and mechanism for line spectrum reduction in nonlinear vibration isolation system are studied. The harmonic balance method is applied to uncover the interaction between different harmonics. It is clear that the considerable energy transfers from the fundamental harmonic to the others by the nonlinear interactions, and thus the energy at the dominant frequency is reduced greatly. When the nonlinear vibration isolation system is in a chaotic state, the response is characteristic of the broadband spectrum, and thus the energy is distributed to all the frequency components. Chaotic attractor is different from the point, limit cycle and so on, and the fractal dimension can be applied to describe its characteristic. Furthermore, the chaotic signal is distinguished from the random one by the saturation of the correlation dimension. The former approaches to saturation with the increasing embedding dimension, but the latter does not. The phase space reconstruction based on wavelet transform can achieve the study of both the geometry and frequency characteristics of the chaos, so that provides a new way to study chaotic response.
A Desktop VR Based Modular Fixture Design Training System
Authors: Peng Gaoliang , Liu Wenjian
Published: May 2009

Modular fixtures are one of the important aspects of manufacturing. This paper presents a desktop VR system which provides a training environment that allows participants to interact naturally with digital objects and configure fixture system instructively. The modular fixture design procedure is proposed. It assists the trainees to make the feasible design decisions and master the necessary principles involved in modular fixture design as well. A hierarchical data model is proposed to represent the modular fixture assembly. Based on this representation, the user can manipulate the virtual models precisely in VE during the design and assembly processes. The assembly relationship between fixture elements is analyzed and the assembly operation process is discussed. Moreover, a Case Based Reasoning (CBR) approach for useful cases retrieval is presented. It provides the trainee with design references to achieve a better design. The case study has demonstrated the functionality of the proposed training system.
Isomorphism Identification of Graphs of Kinematic Chains
Authors: Ding Huafeng , Huang Zhen
Published: May 2009

Isomorphism identification of graphs is one of the most important and challenging problems in the fields of mathematics, computer science and mechanisms. This paper attempts to solve the problem by finding a unique representation of graphs. First, the perimeter loop of a graph is identified from all the loops of the graph obtained through a new algorithm. From the perimeter loop a corresponding perimeter graph is derived, which renders the forms of the graph canonical. Then, by relabelling the perimeter graph, the canonical perimeter graph is obtained, reducing the adjacency matrices of a graph from hundreds of thousands to several or even just one. On the basis of canonical adjacency matrix set, the unique representation of the graph, the characteristic adjacency matrix, is obtained. In such a way, isomorphism identification, sketching, and establishment of the database of common graphs, including the graphs of kinematic chains, all become easy to realize. Computational complexity analysis shows that, in the field of kinematic chains the approach is much more efficient than McKay’s algorithm which is considered the fastest so far. Our algorithm remains efficient even when the links of kinematic chains increase into the thirties.
On the Relationship Between the Ratio of Crack-Length to Plate-Width and the Stress Intensity Factor of a Plate Containing a Single Through-the-Thickness Edge Crack
Authors: Tongele Tongele N.
Published: May 2009

Failure characterization of fracture toughness of a plate containing a single through-the-thickness edge crack and subjected to a tensile stress is investigated. The relationship between the varying ratio of crack length to plate width and the stress intensity factor is examined and compared for elastic, elastic-plastic and nonlinear conditions. Using a numerical illustration, it was found that an increasing ratio increases the stress intensity factor and a decreasing ratio decreases the stress intensity factor regardless of the condition. Hence, the ratio of crack length to plate width can be used as a design parameter that affects the fracture toughness and as a tool of predicting condition for failure.
Optimization of a Vehicle Space Frame Under Ballistic Impact Loading
Authors: Sakaray Umakanth , Trabia Mohamed B. , O’Toole Brendan J. , Thota Jagadeep
Published: May 2009

Shock from impact loading may risk the lives of the occupants of a military vehicle and damage the sensitive electronic components within it. A finite element model (FEM) for a space-frame based military vehicle is presented in this paper. An approach is developed to optimize the design of the joints within the space frame structure to reduce the mass of the vehicle while maintaining its structural integrity. The process starts by creating a parametric FEM of the vehicle. The optimization variables are the lengths of joint branches. The effect of joint location within the space frame is also explored. The problem is subject to geometry and stress constraints. Results show that a mass reduction can be achieved without adversely affecting integrity of the vehicle.
An Experimental Investigation of the Static Transmission Error and Torsional Mesh Stiffness of Nylon Gears
Authors: Chi Chuan Wen , Howard Ian , Wang Jian De
Published: May 2009

This paper details an investigation of the relationship between the static individual torsional mesh stiffness and the static transmission error of gears in mesh. The investigations of the individual torsional mesh stiffness are one of the fundamental concepts in gear analysis and behaviour that have been used in recent years for predicting transmission error. The research work for this paper has two main parts. The first part involved measuring the static transmission error of gears through a series of experiments. An existing test rig was used for the experimental investigation where a nylon gear was placed in mesh with a fixed aluminium gear under various torques. Measurements of the rotation of the nylon gear at precise angular positions throughout the mesh cycle were used as a basis for determining the torsional mesh stiffness and the static transmission error. The second part involved the use of numerical analysis tools (FEA) to calculate the theoretical static transmission error and the individual torsional mesh stiffness in the same conditions as the experiments. The validity of the theory of individual torsional mesh stiffness was investigated, through a comparison between the experimental results and the FEA modelling results. The work included experiments, finite element analysis modelling, and statistical data analysis. The final results of this paper showed that individual torsional mesh stiffness theory can effectively predict transmission error in gear transmission systems, however some improvements need to be made to both the theory and the experiments.
Modification of an Involute Gearing and Its Effect on a Loading Capacity
Authors: Dejl Zdenek , Moravec Vladimir
Published: May 2009

A modification of an involute gearing is presented by a modification of an involute and a longitudinal modification along the face width. In the contribution both of the modifications are presented and theoretical and practical methods for determination of their parameters are shown. Experimental methods of setting up of input data for design of modifications are brought in then. These data are prepared on the basis of measuring of deformations of gearwheels bodies, shafts and shafts supports. An attention is given to the influence on a size and position of a zone of contact of meshing teeth. A separate part deals with the appreciation of an influence of modification on a size of a noise and vibrations of involute gears. As far as a loading capacity of modified involute gearings, the attention is first given to the loading capacity in a contact stress between teeth faces. The comparison is made between loading capacity of an involute gearing with no modification and a gearing modified by various types of modifications. This comparison is made both by using a FEM and by experiment. Experiment is based on lifetime test of these gearing.
Kinematics Analysis and Solving Active Forces of a Plane Symmetry 3-SPR Parallel Manipulator
Authors: Lu Yi , Shi Yan
Published: May 2009

A plane symmetry 3-SPR parallel manipulator with 3 active limbs is proposed. The analytic formulae for solving forward/inverse displacement, velocity and acceleration are derived, the workspace and singularity poses are determined; the active forces are solved by using the virtual work theory. All of the solved results are verified by a simulation mechanism. This project is supported by NSFC (Nature Science Fund of China) 50575198.
Design of Wheeled Mobile Robots With Advanced Drives
Authors: Chen Chao , Angeles Jorge
Published: May 2009

The dual-wheel transmission is a novel drive for wheeled mobile robots; it provides unique features: symmetric structure; load distribution; unlimited steering capacity; and self-rotation while keeping the platform stationary. This paper discusses alternative prototypes of mobile robots with dual-wheel transmissions. We find the conditions of the design parameters in each prototype to achieve isotropic designs, which guarantee optimum maneuverability.
A Systematic and General Approach to Kinematic Position Errors Due to Manufacturing and Assemble Tolerances
Authors: Flores P. , Claro J. C. P.
Published: May 2009

A systematic and general methodology for kinematic position errors analysis of multibody systems is investigated throughout this work, taking into account the influence of the manufacturing and assemble tolerances on the performance of planar mechanisms. The generalized Cartesian coordinates are used to mathematically formulate kinematic constraints and equations of motion of the multibody systems. Thus, the systems are defined by set of generalized coordinates, which represents the instantaneous positions of all bodies, together with a set of generalized dimensional parameters that defines the functional dimensions of the system. These generalized dimensional parameters take into account the tolerances associated with the lengths, fixed angles, diameters and distance between centers, among others. This paper highlights the relation among kinematic constraints, dimensional parameters and output kinematic parameters. Based on the theory of dimensional tolerances, the variation of the geometrical dimensions is regarded as a tolerance grade with an interval associated with each dimension and, consequently, a kinematic amplitude variation for the bodies’ position. The methodology presented is implemented in a computational code developed for kinematic analysis of general multibody systems, capable of automatically generating and solving the equations of motion for general multibody systems. Finally, a slider-crank mechanism is used as a numerical example to demonstrate the accuracy of the presented methodology, as well as to discuss the main assumptions and procedures adopted in this work.
A Model-Driven Development Approach to Integrating Requirements, Design and Simulations in the Early Stages of Product Development
Authors: Zeng Sai , Gomes Jose´ , Singh Man-Mohan , Balmelli Laurent , Boier-Martin Ioana M.
Published: May 2009

Decisions made in the early stages of the product development lifecycle have significant impact on the downstream activities. However, existing tools supporting decision-making and product verification at these stages are very limited. One of the obvious reasons is the lack of a common understanding between the system-level design activity and the design activities within the various participating engineering disciplines. In this paper, we propose a collaboration solution which we have developed and commercialized based on the model-driven development platform that allows numerous engineers from heterogeneous engineering disciplines to collaborate on the development of a complex system, such as an automobile. It helps engineers apprehend the system holistically and collectively thus make better architectural decisions. More specifically, this solution connects discipline-specific designs and simulations with the system-level requirements that trigger them in order to facilitate the integration of development efforts and to enable system-level evaluation of the design concepts early in the product development processes. Our approach provides an effective way to trace and analyze the impact of requirements and design changes, facilitates reuse of simulation artifacts for the optimization of future product designs, and supports decision-making activities at the system level. We illustrate our approach in the context of a automotive use case involving mechanical, requirement and safety engineers respectively using their own authoring environments but collectively in synch on the total system thanks to an SOA (Service-Oriented Architecture) based integration between their authoring environments.
Delay Differential Equations in the Dynamics of Gene Copying
Authors: Verdugo Anael , Rand Richard H.
Published: May 2009

We analyze a model of gene transcription and protein synthesis which has been previously presented in the biological literature. The model takes the form of an ODE (ordinary differential equation) coupled to a DDE (delay differential equation), the state variables being concentrations of messenger RNA and protein. The delay is assumed to depend on the concentration of mRNA and is therefore state-dependent. Linear analysis gives a critical time delay beyond which a periodic motion is born in a Hopf bifurcation. Lindstedt’s method is applied to the nonlinear system, resulting in closed form approximate expressions for the amplitude and frequency of oscillation.
On the Sensitivity of Non-Generic Bifurcation of Non-Linear Normal Modes
Authors: Pak C. H. , Choi Y. S.
Published: May 2009

It is shown that a non-generic bifurcation of non-linear normal modes may occur if the ratio of linear natural frequencies is near r-to-one, r = 1, 3, 5 ·······. Non-generic bifurcations are explicitly obtained in the systems having certain symmetry, as observed frequently in literatures. It is found that there are two kinds of non-generic bifurcations, super-critical and sub-critical. The normal mode generated by the former kind is extended to large amplitude, but that by the latter kind is limited to small amplitude which depends on the difference between two linear natural frequencies and disappears when two frequencies are equal. Since a non-generic bifurcation is not generic, it is expected generically that if a system having a non-generic bifurcation is perturbed then the non-generic bifurcation disappears and generic bifurcation appear in the perturbed system. Examples are given to verify the change in bifurcations and to obtain the stability behavior of normal modes. It is found that if a system having a super-critical non-generic bifurcation is perturbed, then two new normal modes are generated, one is stable, but the other unstable, implying a saddle-node bifurcation. If the system having a sub-critical non-generic bifurcation is perturbed, then no new normal mode is generated, but there is an interval of instability on a normal mode, implying two saddle-node bifurcations on the mode. Application of this study is discussed.
Statistical Response of a Simplified Nonlinear Fluid Model Under Random Parameters
Authors: Chang T-P.
Published: May 2009

In this paper, a simplified spring-dashpot model is proposed to represent the complicated nonlinear response of some viscoelastic materials. Recently, the viscoelastic modeling has been adopted by many researchers to characterize some parts of human body in bioengineering. Among others, the following researchers have already contributed to the development of this field (Weiss et al., [1]; Guedes et al., [2]). Sometimes it is impossible to estimate the constant parameters in the model deterministically, therefore, the damping coefficient of the dashpot and the spring constants of the linear and nonlinear springs are considered as stochastic to characterize the random properties of the viscoelastic materials. The mean value of the displacement of the nonlinear model, subjected to constant rate displacement, can be solved analytically. Based on the closed-form solution, the proposed method produces the statistical responses of the simplified nonlinear fluid model, which is fairly useful in estimating the reliability of the nonlinear system.
Gear Tooth Root Fatigue Assessments by Estimating the Real Stress Cycle
Authors: Jelaska Damir T. , Podrug Srdjan
Published: May 2009

A several kinds of numerical models, including moving force model, for determination the service life of gears in regard to bending fatigue in a gear tooth root, is presented. Finite element method and linear elastic fracture mechanics theories are then used for the further simulation of the fatigue crack growth under a moving load. Moving load produces a non-proportional load history in a gear’s tooth root. The corresponding stress cycle is obtained which enables more precise computing. An approach that accounts for fatigue crack closure effects is developed to propagate crack under non-proportional load. The computational results are compared with other researchers’ numerical results and with service lives of real gears. The fatigue lives and crack paths determined in this paper exhibits a substantial agreement with experimental results and significant improvement compared with the existing numerical models.
Structural Optimization in Multibody Dynamics System With FEM Model on Engine Components
Authors: Hoshino Hiroaki , Shimada Masayoshi
Published: May 2009

This paper describes the structural optimization technique with FEM optimization technology. The design shape of engine components have been optimized with consideration of dynamic effects. In the conventional approach of structural optimization in a Multibody Dynamics (MBD) system, the loads on FEM models of components as boundary conditions for subsequent shape optimization were used to be an output from MBD analysis. When an MBD system was optimized in MBD analysis, the body properties were used to be optimized instead of component shape. In this study a special modeling approach is followed to capture the loads easily and accurately with respect to contact behavior of metal bearings existing in engine components in order to improve the conventional approach with rigid elements. This approach is applied to the piston-crankshaft system of a one-cylinder engine. Topology optimization is performed to detect the effective design parameters of connecting rod (con-rod) shape to reduce weight prior to the shape optimization. Shape optimization of the con-rod results in a 6% weight reduction under the condition of critical compression loading just after the TCD (top dead center) of the combustion process. Furthermore, the structure modification for a piston based on an FE model also inside MBD analysis is performed. The base vectors of FEM morphing technology are used as design variables instead of body properties. These techniques are advanced approaches of structure modification based on FE model for MBD system.
Singularity Analysis of Multi-DOF Planar Mechanisms
Authors: Di Gregorio Raffaele
Published: May 2009

Singular configurations (singularities) are mechanism configurations where the instantaneous kinematics is locally undetermined. Since the indetermination of the instantaneous kinematics causes serious problems both to the static behavior and to the motion control of the mechanism, the research of all the singularities (singularity analysis) is a mandatory step during the design of mechanisms. This paper presents a new approach to implement the singularity analysis of planar mechanisms. The proposed technique extends the use of the instant center properties to the singularity analysis of planar mechanisms with more than one degree of freedom (dof). It exploits the results of previous works by the author in which a geometric and analytic technique has been presented to address the singularity analysis of single-dof planar mechanisms.
Selected Disassembly Planning for Product Maintainability
Authors: Peng Qingjin , Chung Chulho
Published: May 2009

Products are traditionally designed mainly to meet functional requirements with rarely considering maintenance issues for products life-cycle. This paper presents an approach to nondestructive selective disassembly planning for the product maintenance. The approach is based on the part disassemblability analysis. It provides a way to support interactive selective disassembly task planning in dynamic manufacturing environments considering the operation space in applications. To support design at the early stage of product development, this paper also discusses de-manufacturability and maintainability analysis based on the proposed approach. Examples are provided to verify the developed method.
Fractional Order LQR for Optimal Robust Control of a Simple Structure
Authors: Shafieezadeh Abdollah , Ryan Keri , Chen YangQuan
Published: May 2009

This study combines fractional order control with linear quadratic regulator (LQR) for optimal robust control of a simple civil structure. As a first attempt, the purpose of this paper is to demonstrate that, when fractional damping is introduced, additional benefits can be obtained over the best traditional control method. The control problem of this paper can be used as a simple benchmark example to test new control ideas before applying to more complicated models.
Workspace Optimization of a Very Large Cable-Driven Parallel Mechanism for a Radiotelescope Application
Authors: Bouchard Samuel , Gosselin Cle´ment M.
Published: May 2009

The 6-DOF cable-driven mechanism under study in this paper is a feed positioning device for the Large Adaptive Reflector (LAR). The LAR is a concept of a very large orientable radio antenna. The study aims at optimizing the geometry of the cable mechanism to maximize the portion of the desired workspace in which the mechanism can remain in static equilibrium under the predicted external forces and torques. A general test to rapidly compute if the set of external forces and torques can be balanced is developed. This test is applicable to mechanisms with an arbitrary number (minimum six) of cables. Architectures with six to nine cables are optimized and compared. The conclusion of this study is that the prescribed task is unlikely to be achievable by this type of mechanism. Some design guidelines to improve the performance of a large cable-driven mechanism kept under tension by an aerostat are also provided.
Determination of Muscle Fatigue Using Dynamically Embedded Signals
Authors: Slack Paul S. , Ma Xianghong
Published: May 2009

There is concern associated with the duration that a microsurgeon operates. Muscle fatigue can present itself over time and adversely affect the surgeon’s ability to perform appropriately during lengthy procedures. This paper explores a new method of analyzing muscle fatigue within the muscles predominantly used during micro-surgery. The captured Electro-MyoGraphic (EMG) data retrieved from these muscles are analyzed for any defining patterns relating to muscle fatigue. The analysis consists of dynamically embedding the EMG signals from a single muscle channel into an embedded matrix. The muscle fatigue is determined by defining its entropy characterized by the singular values of the Dynamical Embedded (DE) matrix. The paper compares this new method with the traditional method of using mean frequency shifts in EMG signal’s power spectral density. Linear regressions are fitted to the results from both methods, and the coefficient of variation of both their slope and point of intercept are determined. It is shown that the complexity method is more robust in that the coefficient of variation for the DE method has lower variability than the conventional method of mean frequency analysis.
Characteristics of Ramp Load of Hard Disk Drive With Magnetic Bias and Inertia Latch
Authors: Liu Yanning , Kang Sean , Li Bo , Nguyen Tung
Published: May 2009

Hard disk drive (HDD) is a standard component of computer systems for data storage. With the advance of technology, increase of capacity and reduction of price, it is now used more and more in non-traditional computing systems, such as camcorders, portable video and music players, etc. These new applications have different emphasis on HDD performance compared to computers. They might not require very large storage capacity, super fast read access, but need high reliability under operational and non-operational conditions. In particularly, for portable devices, HDD has to survive common non-operational shocks during the daily usage of the devices. One design to improve HDD non-operational shock resistance is to unload read-write heads from media to a ramp after power off instead of leaving them on the medial at a special landing zone. A latch mechanism, such as the pawl latch studied in this paper, is then used to lock them on the ramp. During shock events, all the heads are well separated or limited by the ramp to protect them from hitting each other. Since the heads are off the media, they will not contact the media and cause data loss either. The reliability of load/unload (L/UL) drives, however, does not come free. Other than some design changes, which tend to increase cost, extra care also needs to be taken to load the heads to the media or unload them from the media to the ramp. This paper takes a close look at the inertia/magnetic latch non-operational shock performance and the actuator load process. Mechanical, servo and electronic systems are considered together to create a closed-loop simulation model. The effects of voice coil motor Kt drop off, magnetic latch torque bias, IR sensing circuit on load velocity variation are examined. The physical insights provided in the paper should facilitate the design of HDD.
Hybrid Force/Velocity Control of a Pneumatic Gantry Robot for Contour Tracking: Tuning and Model Validation
Authors: Abu-Mallouh Mohammed , Surgenor Brian
Published: May 2009

The paper examines hybrid force/velocity control of a pneumatic gantry robot for contour tracking. Both experimental and simulation results are presented. The control system is structured to control the contact force and the tangential velocity simultaneously. Controller tuning and model validation results are given for a fixed gain PI-based hybrid force/velocity controller. A simple yet effective model is presented in sufficient detail such that other researchers can perform their own simulations to investigate the utility of their own controller designs. The model is used to demonstrate the negative effects of Coulomb friction. Future work will focus on friction compensation techniques to improve performance.
Practical Tuning of Fractional Order Proportional and Integral Controller (I): Tuning Rule Development
Authors: Bhaskaran Tripti , Chen YangQuan , Xue Dingyu
Published: May 2009

This paper presents a new practical tuning method for fractional order proportional and integral controller (FO-PI). The plant to be controlled is mainly FOPDT (first order plus delay time). The tuning is optimum in the sense that the load disturbance rejection is optimized yet with a constraint on the maximum or peak sensitivity. We generalized MIGO (Ms constrained integral gain optimization) based controller tuning method to handle the FO-PI case, called F-MIGO, given the fractional order α. The F-MIGO method is then used to develop tuning rules for the FOPDT class of dynamic systems. The final developed tuning rules only applies the relative dead time, τ of the FOPDT model to determine the best fractional order α and at the same time to determine the best FO-PI gains. Extensive simulation results are included to illustrate the simple yet practical nature of the developed new tuning rules. In Part (II) of this companion paper, interesting experimental results in two experimental platforms are reported using the tuning rule of this paper. The tuning rule development procedure for FO-PI is not only valid for FOPDT but also applicable for other general class of plants as illustrated.
A CAD Variation Geometric Approach of Solving Active/Constrained Forces of Some Parallel Manipulators With SPR-Type Active Legs
Authors: Lu Yi , Shi Yan , Hu Bo
Published: May 2009

A novel CAD geometric variation approach for solving active-passive forces of some parallel manipulators with SPR-type active legs is proposed. First, some methodical formulae for solving the active/constrained force matrix and active/constrained forces are derived. Second, some basic techniques for constructing the force simulation mechanism are described for solving the force matrix and active/constrained forces. Third, a 3SPR, a 2SPS+2SPR, and a 4SPS+SPR parallel manipulators are presented, respectively, to illustrate how to solve their pose parameters, active/constrained force matrices, and active/constrained forces by the approach. The solving results have been verified by the analytic approach.
Design Optimization of Rigid Body Mechanism Topology
Authors: Sedlaczek Kai , Eberhard Peter
Published: May 2009

Despite modern computer based design tools, the development process of new mechanisms is still based on the engineer’s experience, intuition and ingenuity. The goal of this work is to find a combination of linkage topology and joint types that represent the most suitable mechanism layout for a particular task. Optimization techniques are hardly used for this design problem except for the task of dimensional synthesis of a given mechanism type. This study presents and compares two different approaches to topology or type optimization of planar rigid body mechanisms that can be used to improve the overall design process. The first approach is based on a truss-like ground structure that represents an over-determined system of rigid bars where the most appropriate topology can be extracted from this ground structure by means of gradient based optimization algorithms. In the second approach, we use a genetic algorithm for the intrinsically combinatorial problem of topology synthesis. We explain both approaches and show their capabilities, their advantages and drawbacks.
A Flexible Design Automation System for Toolsets for the Rotary Draw Bending of Aluminium Tubes
Authors: Johansson Joel
Published: May 2009

For parts suppliers in the manufacturing industry, the process of preliminary production preparation and the subsequent calculation of offers are critical business activities. A vital part of production preparation is the design of fixtures and tooling necessary for many processes of metal forming. In order for a company to give quick responses to customer enquiries or changes in prior specifications, it would be highly beneficial with a degree of automation in this design process. This implies the development of a computer based system able to capture existing design procedures and associated knowledge for the classes of tooling required for the forming process. In this work, an implementation for the rotary draw bending of aluminum tubing has been done to exemplify how to develop an automated design system. The system is based on heuristic knowledge developed over many years of practical experience, knowledge analytically derived from fundamental theory found in scientific literature, and rules based on empirical data from trial manufacturing. The system applies knowledge to a given specification that a skilled engineer otherwise would do manually. The system output can be used to evaluate whether a tube is producible. The main idea behind the system is to use knowledge objects containing information on inputs, outputs, constraints and what software are used to implement the knowledge pieces. This approach makes the system highly flexible and allows for multiple types of knowledge that might overlap. When an offering calculation is wanted, the system is set to run applicable knowledge objects for presented input data. Other objects are run when an accurate calculation for detailing is wanted for a more detailed set of input data. The system is built on readily available commercial software packages connected with a simple Visual Basic .Net program. When building a system of this kind, it is essential that the knowledge documentation and structure be such that the functions of the system can be easily understood by the users of the system and by future developers. Aspects of user friendliness, transparency and scalability are addressed in the summary of this paper.
Tolerance Analysis of a Robot Manipulator Having Uncertainties in Joint Clearance and Axis Orientation
Authors: Choi Dong Hwan , Lee Se Jeong , Wickert Jonathan A. , Yoo Hong Hee
Published: May 2009

The operating positional error of a robot manipulator, which develops inevitably because of manufacturing tolerances and assembly clearances, is preferentially maintained within a certain range in order to achieve an acceptable level of performance and accuracy. Because additional cost is incurred when manufacturing tolerances are tightened, an alternative design strategy maximizes the tolerances (so as to reduce the cost) while minimizing positioning error (to satisfy a performance requirement). In this paper, a new joint clearance model is developed for spatial mechanisms that incorporate revolute joints, which in turn are subjected to specified tolerance or uncertainty in the orientation of their axes. Statistical design parameters related to variations of link length and joint axis orientation are identified from the clearance model. The statistical influence of the design parameters on the robot manipulator’s response is investigated through a general multibody dynamics sensitivity formulation. The method offers substantial improvement in computational efficiency when compared to the Monte Carlo procedure. The uncertainty in orientation of a revolute joint’s axis influences the positioning accuracy of the robot manipulator’s response to a greater degree than does uncertainty in the length of a link.
Identification of a Rotor Crack in a Gas Turbine Without Twice Per Revolution Symptoms
Authors: Pennacchi Paolo , Vania Andrea
Published: May 2009

It is a rather common opinion that one of the most important symptoms of a crack growth in rotating machinery is the change in the twice per revolution vibrational behavior. This derives from the generalization of simple models, like Jeffcott rotors, to real overhung machines and is generally true. Anyhow there exists also cases in which the combination of other facts, like the local stiffness of the rotor in correspondence of the crack position and the presence of coupling misalignment between the rotors that compose the shaft-line, make the twice per revolution vibration practically absent. In this paper, a model based diagnostic methodology is presented that allows to identify the presence of a crack. Its application is proven by the experimental case of a crack in the load coupling of a power plant gas turbine.
Fractional Dynamics: A Statistical Perspective
Authors: Machado J. A. Tenreiro , Galhano Alexandra
Published: May 2009

Fractional calculus is a mathematical paradigm that has been increasingly adopted to describe the dynamics of systems with hereditary characteristics, or that reflect an average of a large population of micro elements. In this line of thought, this article analyzed the statistical dynamics of a system composed of a large number of micro-mechanical masses with backlash and impacts. We conclude that, while individual dynamics of each element has an integer order nature, the global dynamics reveal the existence of both integer and fractional dynamics.
Analytical Modeling of Vibration in MRI Scanners
Authors: Wang Fenglin , Mechefske Chris K.
Published: May 2009

The dynamic behavior of a coil cylinder plays a crucial role in determining the vibro-acoustic characterization of a magnetic resonance imaging (MRI) scanner. An analytical model of a non thin-walled gradient coil cylinder is developed under its working fixation boundary condition. Analytical mode shapes and their numerical and experimental counterparts are obtained and compared by using the modified Love’s governing equations, ANSYS software, and modal testing approaches. The modal testing results validate the analytical modeling. In-situ vibration testing of using a remote laser Vibrometer - PSV 300 further verifies the analytical modal results.
Vibration-Based Monitoring of Automotive Light Assemblies for Failure Detection
Authors: Xie Kongying , Surgenor Brian W. , Mechefske Chris K.
Published: May 2009

As the automotive industry becomes increasingly competitive, parts manufacturers are under extreme pressure to improve the quality of their parts, while at the same time reducing costs. The method currently used to detect failures in automotive light assemblies after vibration endurance testing involves manual inspection only after the test is completed. An adaptable, reliable and low cost real time monitoring and diagnostic system that would interrupt the testing operation at the first onset of a failure is desired. This paper describes an accelerometer based and a microphone based monitoring system for automotive light assembly failure detection during endurance testing. Preliminary results from these two systems show a significant difference between healthy and faulty fog light assemblies can be detected. This suggests that there is potential to develop these and potentially other measures for use in an adaptable, reliable and low cost real time monitoring and diagnostic system that would interrupt the testing operation at the first onset of a failure.
Numerical Simulation on the Effects of van der Waals Forces in Micro-Rotor Systems
Authors: Zhou Jian-Bin , Meng Guang , Zhang Wen-Ming , Chen Jie-Yu
Published: May 2009

As a result of scaling down, surface forces such as van der Waals force and electrostatic force in MEMS devices become dominant. This paper investigates the effects of the van der Waals force on the MEMS based micro-rotor systems in the perspective of rotordynamics. An expression for van der Waals force acting on the micro-rotor is derived. Governing equations describing the dynamical behaviors of the micro-rotor under the effect of van der Waals force are presented. Equilibrium positions of the obtained system and their stabilities are discussed. Numerical simulations show that adhesion occurs once the displacement of the micro-rotor exceeds the stable boundary as a consequence of van der Waals force. Free oscillation and dynamically imbalanced response of the micro-rotor system are investigated using both analytical and numerical methods.
On the Transversal Vibrations of an Axially Moving Continuum With a Time-Varying Velocity: Transient From String to Beam Behavior
Authors: Ponomareva S. V. , van Horssen W. T.
Published: May 2009

In this paper an initial-boundary value problem for a linear equation describing an axially moving stretched beam will be considered. The velocity of the beam is assumed to be time-varying. since the order of magnitude of the bending stiffness terms depends on the vibrations modes and the frequencies involved a that combination of two simplified models (a string equation and a beam with string effect equation) will be used to describe the transversal vibrations of the system accurately. Based on the calculations of the natural frequencies the regions of applicability of these models will be determined. A two time-scales perturbation method will be used to construct formal asymptotic approximations of the solutions. It will be shown that the linear axially moving “string to beam” model already has complicated dynamical behavior.