bluuebunny/crossref_metadata_2025 huggingface dataset:
Theoretical and Experimental Analysis of a Cycloidal Speed Reducer
Authors: Davoli Piermaria , Gorla Carlo , Rosa Francesco , Longoni Claudio , Chiozzi Franco , Samarani Alessandro
Published: May 2009

Compared with common speed reducers, the cycloidal ones (also known as cycloid drives) cover a wider range of transmission ratios, have a higher load-carrying capacity, are smaller, exhibit a smoother running and a good efficiency. These characteristics make them attractive for industrial applications, especially for robotics applications, machine tools and linear axis positioning in assembly machinery. In this paper, a theoretical and experimental investigation on an innovative cycloidal speed reducer will be presented. The typical cycloid drive has a planet wheel, the profile of which is the inner offset of an epitrochoid, meshing with cylindrical rollers connected to the case. This reducer, on the contrary, has an external ring gear, the transverse profile of which is the external offset of an epitrochoid, and engages with the planet wheel by means of cylindrical rollers. This paper will investigate the structural characteristics and the kinematical principles of this type of reducer. A theoretical approach based on the envelope theory (following Litvin’s approach) will be developed and compared with a development of Blanche and Yang’s approach. Furthermore, a simplified procedure to calculate force distribution on cycloid drive elements, as well as its power losses and theoretical mechanical efficiency will be presented. The effects of design parameters on the values of the forces will be studied, for an optimal design of this type of reducer. The theoretical model will be then tuned using the results of tests on a specific rig. As a result of the experimental tests, the reducer mechanical efficiency dependency on speed and torque will be described. The aim of this work is to perform the fine tuning of a theoretical model in order to predict the operating behavior of the cycloid drive, and to improve its design procedure.
Time Varying Approaches to Dynamic Analysis of a Planetary Gear System Using a Discrete and a Continuous Models
Authors: Huang K. J. , Liang C. C. , Chen J. Y.
Published: May 2009

Two time varying approaches are executed in analyzing dynamics for an involute planetary gear system, which respectively use a conventional discrete model of the equivalent mass-damping-spring elements and a continuous geometry model by the finite element method. In the discrete approach, the tooth number, position, and phasing difference of the meshing tooth pairs are described by time varying and nonlinear meshing stiffnesses. Natural frequencies, deformations, meshing forces, fillet stresses, and dynamic factors can be calculated by using the Jacobi transformation and the Runge-Kutta integration. In the continuum approach, dynamics of the planetary gear system is analyzed using the software, LS-DYNA. The approach of the continuous geometry model can incorporate the time varying properties intrinsically. In this continuum study, not CAD models, high quality mesh elements of the planetary gear system are automatically generated directly using the derived tooth profile equations. After assigning initial and boundary conditions, dynamic responses for the planetary gear system are solved. Natural frequencies and fillet stresses of the both approaches are verified by each other comparison. Potentially, the continuum approach can extensively and sophistically analyze dynamics problems of the planetary gear systems.
Gearmotors With a Planetary Eccentric Gear Train for Service and Mechatronic Systems
Authors: Starzhinsky Victor E. , Mardosevich Elena I. , Basinyuk Vladimir L. , Ossipenko Sergei A.
Published: May 2009

Investigation results are cited in the field of developing super-light gearmotors based on high-torque motors, eccentric single-stage gear transmissions of planetary type with gear ratios between 80 and 120. These include the gears of aluminum alloys with working surfaces coated by micro-arc oxidation. Peculiarities of their design are presented as well as computation of geometrical parameters of the main elements, material choice and hardening techniques exerting most favorable effect on the lifetime and output-input ratio of the drive.
Scuffing Performance of a Hard Coating Under EHL Conditions at Sliding Speeds Up to 16 m/s and Contact Pressures Up to 2.0 GPa
Authors: Snidle R. W. , Dhulipalla A. K. , Evans H. P. , Cooper C. V.
Published: May 2009

Scuffing experiments were conducted using 76 mm diameter disks both with and without a metal-containing, carbon-based hard coating. The operating conditions in the experiments were severe with sliding speeds up to 16 m/s and maximum Hertzian contact pressures up to 2.0 GPa. The disks were of alloy steel which was case-carburised and hardened followed by axial grinding. Four different surface conditions were investigated as follows: ground/un-coated; ground/coated; superfinished/uncoated; superfinished/coated. Experiments were also carried out in which ground/coated disks were run against ground/uncoated disks. The results of the experiments show that the addition of the hard coating to the ground disks significantly improved both their scuffing resistance and frictional behavior, but the coating was less effective in producing an improvement in the durability and friction of the superfinished disks.
Minimised Gear Lubrication by a Minimum Oil/Air Flow Rate
Authors: Ho¨hn Bernd-Robert , Michaelis Klaus , Otto Hans-Philipp
Published: May 2009

The objectives of the research project were to investigate the limits concerning possible reduction of lubricant quantity in gears without detrimental influence on the load carrying capacity. The investigations covered the influence of the oil level in dip lubricated systems as well as the oil flow rate in spray lubricated systems namely oil-air supply systems on power loss, heat generation and load carrying capacity. The load carrying capacity in terms of characteristic gear failure modes was determined and was compared to the results using conventional lubricant volumes with dip lubrication. Therefore in back-to-back gear tests the parameters speed, load and oil quantity were varied for examination of the four main gear flank damages: scuffing, wear, pitting and micropitting. The investigations showed the application potential of oil/air lubrication also for heavy duty transmissions nevertheless there exists a natural limitation for lowering the oil quantity in transmissions without detrimental influence on the load carrying capacity.
Geometry of Tooth Profile and Fillet of Face-Hobbed Spiral Bevel Gears
Authors: Zhang Yi , Wu Zhi
Published: May 2009

The determination of the geometry for the whole tooth profile, including the meshing profile and the tooth fillet, is important for tooth contact analysis and the mesh generation for FEM analysis of gear pairs. This paper presents a systematic approach for the determination of the complete tooth geometry of face-hobbed hypoid and spiral bevel gears. The detailed mathematical formulation for the generation of gear tooth surface and the equations for the tooth surface coordinates are provided in the paper. The surface coordinates and normal vectors are calculated at grid points selected based on the gear blank dimension. Using the machine tool settings as input, the computer model simulating the gear generation process precisely calculates the tooth geometry parameters on the selected grid. A numerical example is included in the paper to illustrate the presented approach.
Study on Application of Neural Network in Chaotic Vibration Isolation System
Authors: Liu Shuyong , Zhu Shijian , Yu Xiang , Wang Jing-Jing
Published: May 2009

The paper studies the application of neural network in chaotic vibration isolation system. Because the dynamical characteristics of the isolation system change with working state of the isolated object, the control system must have the ability to adjust the system parameters online to obtain the designated target. During the controlling process, chaotic vibration signal identification is the first step. New technology, however, is needed to identify the category of the signals because the traditional methods such as Lyapunov exponent and correlation dimension are time-consuming. The incompact wavelet neural network is trained to classify different signals effectively in this paper, and it is beneficial to adjust the nonlinear isolation system parameters timely. Hence the system works in a chaotic state, and the linear spectrum in the waterborne noise can be reduced.
Control of a Projectile Smart Fin Using an Inverse Dynamics-Based Fuzzy Logic Controller
Authors: Trabia Mohamed B. , Yim Woosoon , Weinacht Paul , Mudupu Venkat
Published: May 2009

The objective of this paper is to explore a method for the design of fuzzy logic controller for a smart fin used to control the pitch and yaw attitudes of a subsonic projectile during flight. Piezoelectric actuators are an attractive alternative to hydraulic actuators commonly used in this application due to their simplicity. The proposed cantilever-shaped actuator can be fully enclosed within the hollow fin with one end fixed to the rotation axle of the fin while the other end is pinned at the trailing edge of the fin. The paper includes a dynamic model of the system based on the finite element approach. The model includes external moment due to aerodynamic effects. This paper presents a novel approach for automatically creating fuzzy logic controllers for the fin. This approach uses the inverse dynamics of the smart fin system to determine the ranges of the variables of the controllers. Simulation results show that the proposed controller can successfully drive smart fin under various operating conditions.
A Constitutive Equation for Linear Viscoelastic Thermoset Materials Undergoing Compression
Authors: Ramirez Lynnette E. S. , Coimbra Carlos F. M.
Published: May 2009

A constitutive equation for linear viscoelasticity is presented. The equation is formulated using a Variable-Order (VO) integro-differential operator, in which the order of the derivative q(t*) is allowed to be a function of the dependent or independent variables. We propose a relationship in which the stress is related to the q-th derivative of strain, where q(t*) and the normalized time t* characterize the viscoelastic response of the material. We assume that the function q(t*) is a measure of the rate of change of disorder within the material and develop a statistical mechanical model. The resulting model correlates well with experimental results for strain rate values varying over eight orders of magnitude. Using experimental data for a carbon/epoxy composite and an epoxy resin undergoing constant rate compression in the linear range, we derive a semi-empirical functional relationship with the normalized time that is used in a VO constitutive equation to model the viscoelastic deformation in time. The resulting dimensionless constitutive equation requires a much smaller number of empirically determined coeffcients to adequately represent the data.
Passive Targeted Energy Transfers and Strong Modal Interactions in a Thin Plate With Strongly Nonlinear End Attachments of Different Configurations
Authors: Georgiades F. , Vakakis A. F.
Published: May 2009

In this paper we examine Targeted Energy Transfers (TETs) and nonlinear modal interactions occurring in a thin cantilever plate lying on an elastic foundation with strongly nonlinear lightweight attachments of different configurations. Under shock excitation of the plate we systematically study, nonlinear modal interactions and passive broadband targeted energy transfer phenomena between the plate and attachments of the following configurations: a single ungrounded, strongly (essentially) nonlinear single-degree-of-freedom (SDOF) NES; multiple SDOF attachments attached at different points of the plate; and a single multi-degree-of-freedom (MDOF) attachment with multiple essential stiffness nonlinearities. We perform parametric studies by varying the parameters and location of the attachments, in order to optimize TETs from the plate to the NES. We examine in detail the underlying mechanisms influencing TETs by means of Hilbert-Huang Transforms in combination with Wavelet Transforms. These transforms enable one to systematically study the strong modal interactions between the essentially nonlinear attachments and different plate modes. The efficacy of using this type of essentially nonlinear attachments as passive absorbers of broadband vibration energy is discussed.
Dynamic Analysis of a Pneumatic Mounting System for Marine Propulsion Engines
Authors: Xu Wei , He Lin , Lv Zhi-Qiang
Published: May 2009

To reduce the vibration and noise level in ships, marine propulsion engines are conventionally supported by rubber mounts. But the design of a rubber mounting system for medium- and low-speed propulsion engines could be very complicated due to the large stiffness and rubber creep of rubber mounts. Air spring, which is superior in many respects to rubber mount, can be used as the propulsion engine mounting system. The superiority and potential of pneumatic mounting system is discussed in this paper. The pneumatic system’s loading and stiffness characteristics, which are distinct from rubber system, are analyzed. And an optimized air pressure distribution among air springs is given. The system natural frequencies and force transmissibility are calculated based on a fictitious propulsion engine model. The results show that the pneumatic mounting system can effectively attenuate the dynamic force transmitted to the ship floor, and the system characteristics are not apparently affected by the air pressure distribution.
Modeling Expected Wear in Revolute Joints With Clearance in Multibody Mechanical Systems
Authors: Flores P. , Ambro´sio J. , Claro J. C. P. , Lankarani H. M.
Published: May 2009

The main goal of this work is to develop a methodology for studying and quantifying the wear phenomenon in revolute clearance joints. In the process, a simple model for a revolute joint in the framework of multibody systems formulation is presented. The evaluation of the contact forces developed is based on a continuous contact force model that accounts for the geometrical and materials properties of the colliding bodies. The friction effects due to the contact in the joints are also represented. Then, these contact-impact forces are used to compute the pressure field at the contact zone, which ultimately is employed to quantify the wear developed and caused by the relative sliding motion. In this work, the Archard’s wear model is used. A simple planar multibody mechanical system is used to perform numerical simulations, in order to discuss the assumptions and procedures adopted throughout this work. Different results are presented and discussed throughout this research work. From the main results obtained, it can be drawn that the wear phenomenon is not uniformly distributed around the joint surface, owing to the fact that the contact between the joint elements is wider and more frequent is some specific regions.
Higher-Order Tooth Flank Form Error Correction for Face-Milled Spiral Bevel and Hypoid Gears
Authors: Fan Qi , DaFoe Ronald S. , Swanger John W.
Published: May 2009

The increasing demand for low noise and high strength leads to higher quality requirements in manufacturing spiral bevel and hypoid gears. Due to heat treatment distortions, machine tolerances, variation of cutting forces and other unpredictable factors, the real tooth flank form geometry may deviate from the theoretical or master target geometry. This will cause unfavorable displacement of tooth contact and increased transmission errors, resulting in noisy operation and premature failure due to edge contact and highly concentrated stresses. In the hypoid gear development process, a corrective machine setting technique is usually employed to modify the machine settings, compensating for the tooth flank form errors. Existing published works described the corrective machine setting technique based on the use of mechanical hypoid gear generators, and the second order approximation of error surfaces. Today, Computer Numerically Controlled (CNC) hypoid gear generators have been widely employed by the gear industry. The Universal Motion Concept (UMC) has been implemented on most CNC hypoid generators, providing additional freedoms for the corrections of tooth flank form errors. Higher order components of the error surfaces may be corrected by using the higher order universal motions. This paper describes a new method of tooth flank form error correction utilizing the universal motions for spiral bevel and hypoid gears produced by the face-milling process. The sensitivity of the changes of tooth flank form geometry to the changes of universal motion coefficients is investigated. The corrective universal motion coefficients are determined through an optimization process with the target of minimization of the tooth flank form errors. A numerical example of a face-mill completing process is presented. The developed new approach has been implemented with computer software. The new approach can also be applied to the face-hobbing process.
Curvature-Based Finite Element Method for Euler-Bernoulli Beams
Authors: Kuo Y. L. , Cleghorn W. L.
Published: May 2009

This paper presents a new method called the curvature-based finite element method to solve Euler-Bernoulli beam problems. An approximated curvature distribution is selected first, and then the approximated transverse displacement is determined by double integrations. Four numerical examples demonstrate the validity of the method, and the results show that the errors are smaller than those generated by a conventional method, the displacement-based finite element method, for comparison based on the same number of degrees of freedom.
NMR Measurements of Anomalous Diffusion Reflect Fractional Order Dynamics
Authors: Magin Richard L. , Baleanu Dumitru
Published: May 2009

Diffusion weighted MRI is often used to detect and stage neurodegenerative, malignant and ischemic diseases. The correlation between developing pathology and localized diffusion measurements relies on the design of selective phase encoding pulses that alter the intensity of the acquired signal according to biophysical models of spin diffusion in tissue. The most common approach utilizes a bipolar or Stejskal-Tanner gradient pulse sequence to encode the apparent diffusion coefficient as an exponential, multi-exponential or stretched exponential function of experimentally-controlled parameters. Several studies have investigated the ability of the stretched exponential to provide an improved fit to diffusion-weighted imaging data. These results were recently analyzed by establishing a direct link between water diffusion, as measured using NMR, and fractal structural models of tissues. In this paper we suggest an alternative description for stretched exponential behavior that reflects fractional order dynamics of a generalized Bloch-Torrey equation in either space or time. Such generalizations are the basis for similar anomalous diffusion phenomena observed in optical spectroscopy, polymer dynamics and electrochemistry. Here we demonstrate a correspondence between the detected NMR signal and anomalous diffusional dynamics of water through the Riesz fractional order space derivative and the Caputo form of the fractional order Riemann-Liouville time derivative.
Closed-Form Equilibrium Analysis of Planar Tensegrity Structures
Authors: Bayat Jahan , Crane Carl D.
Published: May 2009

This paper presents a closed-form analysis of a series of planar tensegrity structures to determine all possible equilibrium configurations for each device when no external forces or moments are applied. The equilibrium position is determined by identifying the configurations at which the potential energy stored in the springs is a minimum. The degree of complexity associated with the solution was far greater than expected. For a two-spring system, a 28th degree polynomial expressed in terms of the length of one of the springs is developed where this polynomial identifies the cases where the change in potential energy with respect to an infinitesimal change in the spring length is zero. Three and four spring systems are also analyzed. These more complex systems were solved using the Continuation Method. Numerical examples are presented.
Re-Shaping Semi-Active Structural Response Via Simple Applications of Embedded Computation, Sensors and Valves
Authors: Chase J. Geoffrey , Mulligan Kerry J. , Mander John B. , Rodgers Geoffrey W. , Chen XiaoQi
Published: May 2009

Semi-active dampers and actuators hold significant promise for their ability to add supplemental damping and reduce structural response, particularly under earthquake loading. Novel devices utilizing off the shelf components and control systems are used to modify structural response. Devices are presented from design, modeling, analysis and validation via hybrid testing and experimental shake table results. All cases are compared with independent analytical predictions based on first principles analysis.
Reconstruction of Mesh Surface With Sharp-Edges From Binary Volume Models
Authors: Wang Charlie C. L.
Published: May 2009

This paper presents an approach to automatically recover mesh surfaces with sharp-edges for solids from their binary volumetric discretizations (i.e., voxel models). Our method consists of three steps. The topology singularity is first eliminated on the binary grids so that a topology correct mesh M0 can be easily constructed. After that, the shape of M0 is refined and its connectivity is iteratively optimized into Mn. The shape refinement is governed by the duplex distance-fields derived from the input binary volume model. However, the refined mesh surface lacks sharp edges. Therefore, we employ an error-controlled variational shape approximation (VSA) algorithm to segment Mn into nearly planar patches, and then recover sharp edges by applying a novel normal-based trilateral filter to the surface. Using the technique presented in this paper, smooth regions and sharp edges can be automatically recovered from raw binary volume models without scalar field or Hermite data. Comparing to other related surface recovering methods on binary volume input, our algorithm needs less heuristic coefficients.
Differential Evolution Applied to the Design of a Three-Dimensional Vehicular Structure
Authors: Viana Felipe Antonio Chegury , Oliveira Fernando Ce´sar Gama de , Borges Jose Antonio Ferreria , Steffen Valder
Published: May 2009

The purpose of this paper is to demonstrate the application of Differential Evolution to a realistic design optimization test problem. The present contribution regards the improvements implemented to the original basic algorithm as well as the application of a new algorithm for dealing with the unique challenges associated with real world optimization problems. The selected example is a three-dimensional vehicular structure optimization problem modeled using the commercial Finite Element software ANSYS® that has a combination of continuous and discrete design variables. The use of traditional gradient-based optimization algorithms is thus not practical. The numerical results presented indicate that the Differential Evolution algorithm is able to find the optimum design for the proposed problem. The algorithm is robust in the sense that it is capable of dealing with the numerical noise involved in the modeling of the system and to manipulate discrete design variables, accordingly.
Automatic Synthesis of a Planar Linkage With a Stiffness-Varying Spring Connected Rigid Block Model
Authors: Nam Sang Jun , Jang Gang-Won , Park Jung Hun , Hun Jin Sub , Yi Yong Sub , Kim Yoon Yong
Published: May 2009

A linkage mechanism is a device to convert an input motion into a desired motion in a machine or a robot. The traditional linkage synthesis practice is depended on the experience and intuition of the skilled designer. This practice based on trial and error approach or only size/shape changes of already-available mechanism often results in improper design. This observation has motivated us to develop a so-called “automatic” design methodology that determines the linkage type and dimensions during synthesis process. The synthesis process can be formulated as a minimization problem. However, the process can be extremely difficult and time-consuming unless there is a single unified linkage model that represents any linkage mechanism without complicating kinematic analysis and allows the use of an efficient gradient-based optimizer. The main contribution of this research is to propose a unified planar linkage model consisting of rigid blocks connected by zero-length springs having real-valued variable stiffness. Stiffness controlling variables are the design variable of the minimization problem and a general planar linkage can be simulated by the spring-connected rigid block model if the stiffness value is chosen appropriately. This work shows how new idea works and verifies this new approach on the synthesis of the planar linkages consisting of links and revolute joints.
Theoretical Design and Control Analysis of Reconfigurable Parallel Kinematic Machine Tools
Authors: Zhang Dan , Bi Zhuming , Ge Yunjian
Published: May 2009

This paper introduces the theoretical design and control of reconfigurable parallel kinematic machine tools. First, the general concept of reconfigurable parallel kinematic machine (RPKM) and its growing demand are introduced. Second, the design of reconfigurable parallel kinematic machines is discussed and the geometric modeling of such structures is presented and explained. The potential applications of this type of machine are described. Finally, a case study for one of the proposed structures is conducted, including kinematic/dynamic modeling and control, some results and simulation are demonstrated.
Comparison of Spring Models for Dynamics Simulation of Spring Operating Mechanism for Circuit Breaker
Authors: Sohn Jeong-Hyun , Lee Seung-Kyu , Kim Seung-Oh , Yoo Wan-Suk
Published: May 2009

Since the performance of the circuit breaker depends on the spring operating mechanism, the analysis of the spring operating mechanism is needed. The spring, especially closing spring, stores the deformation energy due to the compression and then accelerates the big loads rapidly in the circuit breaker. To accurately carry out the kinematic and dynamic analysis of the circuit breaker, the accurate modeling of the spring behavior is needed. In this paper, the static stiffness of the spring is captured by using the tester. Sine excitation tests based on several frequencies and amplitudes are performed to find out the spring characteristics. Test results are used to verify the spring modeling. Three types of spring models such as a linear spring model, modal spring model, and nodal spring model are suggested and compared with the experimental results. Numerical results are compared with the experimental results according to the numerical accuracy and the efficiency.
System Identification of the High Performance Drilling Process for Network-Based Control
Authors: del Toro Rau´l M. , Schmittdiel Michael C. , Haber-Guerra Rodolfo E. , Haber-Haber Rodolfo
Published: May 2009

A simple, fast, network-based experimental procedure for identifying the dynamics of the high-performance drilling (HPD) process is proposed and successfully applied. This identification technique utilizes a single-input (feed rate), single-output (resultant force) system with a dual step input function. The model contains the delays of both the network architecture (a PROFIBUS type network) and the dead time related with the plant dynamic itself. Classical identification techniques are used to obtain first order, second order, and third order models on the basis of the recorded input/output data. The developed models relate the dynamic behavior of resultant force versus commanded feed rate in HPD. Model validation is performed through error-based performance indices and correlation analyses. Experimental verification is performed using two different work piece materials. The models match perfectly with real-time force behavior in drilling operations and are easily integrated with many control strategies. Furthermore, these results demonstrate that the HPD process is somewhat non-linear with a remarkable difference in gain due to work piece material; however, the dynamic behavior does not change significantly.
Application of Smart Materials for Noise and Vibration of Hydraulic Systems
Authors: Motlagh Amin M. , Elahinia Mohammad H. , Abuhaiba Mohammad , Olson Walter W.
Published: May 2009

As market demands vehicles with higher performance, lower fuel consumption, and less emission, hybrid vehicles receive increasing attention. Hybrid technologies have been developed for both passenger and heavy-duty vehicles. Hydraulic hybrid is a technology that is specifically suitable for heavy SUVs and trucks. Despite beneficial aspects of hydraulic systems in reducing the fuel consumption and increasing the launch acceleration for these vehicles, hydraulic vibration and noise is barrier in commercializing this technology. Many studies have been performed on noise and vibration problems of hydraulic systems and many solutions have been proposed. This paper, after introducing the hydraulic hybrid vehicle technology and conventional hydraulic systems in vehicles, reviews the state of the art of the solutions developed for hydraulic noise and vibration. The focus is on the sources of hydraulic noise and vibration. Different approaches for reducing the noise and vibration in hydraulic systems have been reviewed with an emphasis on the application of smart materials. These existing solutions are examined and evaluated for mitigating noise and vibration in hydraulic hybrid vehicles.
PI vs Fractional PI for the Control of a Shunt Active Power Filter
Authors: Rico A. , Milane´s M. I. , Romero E. , Vinagre B. M.
Published: May 2009

Nonlinear loads connected to electric power systems lead to distortions in the source current waveform. One solution to improve power quality is the use of Shunt Active Power Filters (SAPF), which are able to correct both the harmonics and the unbalance in the load current. Two of the most commonly used control strategies for these devices are the so-called Unity Power Factor (UPF) strategy and the Voltage Synchronization (VS) strategy. In these, the reference currents are obtained by multiplying the source voltages by the equivalent conductance. In VS strategy this conductance is obtained from the tracking error between the measured dc bus voltage and a reference value. To minimize this tracking error, linear controller structures, as PI are used. In the last three decades, Fractional Order Control (FOC) has been used in many robust control problems, and has been applied recently to the control of a Power Electronic Buck Converter. In this line, we here consider the use of a fractional PI controller to obtain the reference current in a SAPF under the VS strategy. Simulation results are given comparing the PI and Fractional PI controllers in order to minimize the ISE and IAE cost functions of the tracking error. They show the improved performance obtained with the PI fractional controller.
Delay-Induced Multistability in a Generic Model for Excitable Dynamics
Authors: Hizanidis Johanne , Aust Roland , Scho¨ll Eckehard
Published: May 2009

Motivated by real-world excitable systems such as neuron models and lasers, we consider a paradigmatic model for excitability with a global bifurcation, namely a saddle-node bifurcation on a limit cycle. We study the effect of a time-delayed feedback force in the form of the difference between a system variable at a certain time and at a delayed time. In the absence of delay the only attractor in the system in the excitability regime, below the global bifurcation, is a stable node. Delay renders the phase space infinite-dimensional and creates multistability of periodic orbits and the fixed point. Homoclinic bifurcations, period-doubling as well as saddle-node bifurcations of limit cycles are found in accordance with Shilnikov’s theorems.
Practical Balancing of Flexible Rotors for Power Generation
Authors: Racic Zlatan , Hidalgo Juan
Published: May 2009

Balancing technology is still relatively new. Thirty years ago it was primarily still part of the skilled trade and was often obscured. Today there is enough reference literature printed during the last 20 years alone on general balancing and balancing of flexible rotors, that could fill a room, (Ref: N. Rieger). The majority of papers and other references deal with theoretical derivation of equations based on Jeffcott rotor model. With the growth of rotor sizes specifically of electric generators in power plants, so grew the need to develop not only a theory, but also the way to practically balance these rotors. The economy of manufacturing required pushing the rotors to more and more slender; lower and lower stiffness (∝ EIxx/L3) designs, in relation to its mass moment of inertia (Im), these rotors were more difficult to balance. The first to encounter the problem of balancing these rotors were the OEMs. On two different shores of the Atlantic Ocean, two basic balancing theories known as balancing in “N”, or in “N+2” balancing planes and operating rotor modes were developed. Later, with the development of the microcomputer the influence coefficient method had gained popularity among the power plant community and despite good experiences from both sides the controversy over which one produces better results was left open. In this paper a review of the “N” and “N+2” methods including notes on influence coefficients (IC) is conducted from a practical standpoint. The conclusion by the Authors is that there is no “better” or “worse” balancing method, only the more or less economical in a given situation, and neither gives a unified method to satisfy every rotor. General guidance is also provided over which method to use for best results in balancing large turbo-generator sets.
On Optimization of 2D Compliant Mechanisms Using Honeycomb Discretization With Material-Mask Overlay Strategy
Authors: Saxena Anupam
Published: May 2009

Novel honeycomb tessellation and material mask overlay methods are proposed in this paper to obtain optimal planar compliant topologies free from checkerboard and point flexure pathologies. A cardinal reason, namely the presence of strain-free rotation regions in rectangular cell based discretization is identified to be a cause in appearance of such singularities. With each hexagonal cell sharing an edge with its neighboring cells, strain-free displacements are not permitted anywhere in the continuum. The new material assignment approach manipulates material within a group of cells as opposed to a single cell thereby reducing the number of variables making optimization efficient. Optimal solutions obtained are free from intermediate material states and can be manufactured directly after design, without requiring any post processing. The proposed procedure is illustrated using two classical examples in 2D compliant mechanisms solved using genetic algorithm.
Robust Approach for Position Control of Hydraulic Differential Cylinder
Authors: Liu Yan , So¨ffker Dirk
Published: May 2009

The paper introduces a robust nonlinear control approach for the position control of hydraulic differential cylinder. The behavior of a hydraulic differential cylinder is highly nonlinear. A perfect model is usually not available. So nevertheless a robust control is required, to guarantee the performance of the cylinder, usually based on an imperfect model. The presented approach combining the classical feedback linearization approach and an extended Luenberger observer technique is robust to model uncertainties or unknown effects acting to the system, for example as unknown load, and can be applied to single-input single-output (SISO) nonlinear systems. It improves the robustness and extends the application area of feedback linearization control. The approach is implemented and tested on a hydraulic differential cylinder test rig. Theoretical proofs and experimental results are presented.
A New Singularity-Free Path-Planning Method for a Class of Fully-Parallel Planar Manipulators
Authors: Paganelli Davide
Published: May 2009

Two severe problems may arise, while planning a path for a parallel manipulator. First, it might be impossible to reach a desired configuration at all, and second, any possible path leading to a desired configuration might cross a parallel singularity, which could provoke the loss of platform control and jeopardize the structural integrity of links and actuators. These two problems are strictly related to the topological properties, connectedness in particular, of the configuration space and of the singularity locus. This paper presents a new numerical method based on differential topology, which is able to identify and count the disjoint regions composing the configuration space, and the disjoint regions into which the configuration space is split by the singularity locus. After this classification, it is always possible to find a path connecting any two configurations, if any exists. This path is singularity-free, if any singularity-free path exists. The method is applied to 3RRR planar manipulators, with actuators on the middle joint of each leg.
Kinematic Analysis of a Variable-Speed Transmission Mechanism
Authors: Pennock Gordon R. , Israr Ali
Published: May 2009

This paper presents a kinematic analysis and a redesign of a variable-speed transmission mechanism. The mechanism is a seven-bar linkage where the rotation of the input crank is converted into the oscillation of the output link. The input crank rotates at a constant speed and the output link consists of an overrunning clutch mounted on the output shaft. The angle through which the clutch oscillates, for each revolution of the input crank, can be adjusted by a control arm. This arm allows a fixed pivot to be temporarily released and moved along a circular arc about a permanent ground pivot. The paper shows how to determine the angle of oscillation of the clutch for a specified position of the fixed pivot. The paper also investigates the extreme positions of the clutch corresponding to the extreme positions of a point on the coupler link. For this reason, the paper investigates the geometry of the path traced by a coupler point. The work shows how to determine the location of the ground pivot of the control arm which will cause the clutch to remain stationary during a complete rotation of the input crank. Then the paper shows how to design the control arm by using these conditions; i.e., the conditions for a redesign of the mechanism are investigated. A novel technique, in which kinematic coefficients are obtained with respect to an independent variable, is presented. This technique decouples the position equations and gives additional insight into the geometry of the mechanism.
Design and Manufacturing of Radio-Controlled Motor Glider for Information System
Authors: Sakamoto Haruo , Takemura Yoshiya , Yanamoto Yukari
Published: May 2009

This research and development aims the development of the disaster information system by the network for the disaster information collected at the time of disasters such as earthquakes, storm, or flood. This system uses a small unmanned aircraft for the aerial photography. The system sends the aerial photography information to the ground. The damage state can be understood by the monitoring television, when the system is established. The radio-controlled motor glider is used as a small unmanned aircraft. The gliding performance can be effectively obtained with small energy, and the flight time expected is to be long. Two small wireless cameras and GPS receivers are loaded as an information collection system. The glider was designed and produced by the materials such as balsa wood and plywood board. The wing length is 2 m long, and the weight of the aircraft body is 813g. The weight of the aircraft body contains about 140 g of the information collection system. A flight experimentation was conducted. The location is the campus of the Kochi University of Technology, where the permission of the flight experiment was obtained there. The information collection system successful worked within half the range of the university campus as a result of the flight experimentation. This research and development concluded that the information collection system in the range of the university campus was possible.
Approximate Motion Synthesis of Spherical Kinematic Chains
Authors: Venkataramanujam Venkatesh , Larochelle Pierre
Published: May 2009

In this paper we present a novel dimensional synthesis technique for approximate motion synthesis of spherical kinematic chains. The methodology uses an analytic representation of the spherical RR dyad’s workspace that is parameterized by its dimensional synthesis variables. A two loop nonlinear optimization technique is then employed to minimize the distance from the dyad’s workspace to a finite number of desired orientations of the workpiece. The result is an approximate motion dimensional synthesis technique that is applicable to spherical open and closed kinematic chains. Here, we specifically address the spherical RR open and 4R closed chains however the methodology is applicable to all spherical kinematic chains. Finally, we present two examples that demonstrate the utility of the synthesis technique.
Experimental and Numerical Analysis of Dynamics of the Rotor-Bearing-Seal System
Authors: Shen Xiaoyao , Jing Jianping , Gong Qimiao
Published: May 2009

Linear and nonlinear dynamics and stability of the rotor-bearing-seal system are investigated both theoretically and experimentally. First the system is modeled with the finite element method. The rotordynamic behavior of the journal bearing and the labyrinth seal are represented by eight linearized dynamic force coefficients. An experimental rotor-bearing-seal device is designed and tests are carried out. The experimental system is studied using the developed linear equations. Complex eigenvalues are solved. Corresponding critical speeds and logarithmic decrements to determine the thresholds of instability are calculated. Then the experimental rotor system is simplified as the Jeffcott rotor. The nonlinear oil-film forces are got under the short bearing theory and Muszynska nonlinear seal force model is used. Numerical method is utilized to solve the nonlinear governing equations. Bifurcation diagrams, Poincare´ maps, spectrum plots and rotor orbits are drawn to analyze various nonlinear phenomena and system unstable process. Theoretical results from the linear and nonlinear analysis are in good agreement with results from experiments. Conclusions are drawn and prove that this study will contribute to the further understanding of dynamics and stability of the rotor system with the fluid-induced forces from oil-film bearings and the seals.
A Static and Nonlinear Dynamic Analysis of Resonant Microbeams
Authors: Emam Samir A. , Khater Mahmoud E. , Gad Emil H.
Published: May 2009

An investigation into the response of microbeams to DC and AC electric actuation is presented. The beam is modeled according to the Euler-Bernoulli beam theory and small strains and moderate rotation approximations are assumed. The governing equation is a nonlinear integral-partial-differential equation in space and time. The model accounts for mid-plane stretching, applied axial load, DC electrostatic forces, and AC harmonic forces. A reduced-order model based on the Galerkin discretization technique is introduced to simulate the behavior of microswitches and resonant sensors. The static behavior of the microbeam under electrostatic forces is studied and compared to the results available in the literature. The dynamic behavior of resonant microbeams under AC harmonic forces is investigated. An analytical solution for the vibration modes and natural frequencies of the microbeam around its statically deflected position is obtained. A shooting method is used to numerically integrate the nonlinear discretized equations and obtain periodic orbits of the response. The stability of these periodic orbits is investigated using Floquet theory. The sensitivity of the device to small-amplitude excitations is also investigated.
Auxiliary Axis for Rensselaer’s Geotechnical Centrifuge Center In-Flight Robot: Design Considerations
Authors: Saunders Glenn , Derby Stephen J. , Abdoun Tarek H.
Published: May 2009

Rensselaer’s Geotechnical Centrifuge Center is a resource for conducting research into the behavior of soils, earthen structures and other materials under high g-force conditions. The 3m radius centrifuge can accelerate a roughly 1m × 1m × 1m payload up to as much as 200 g’s. Under such loading, properly prepared soil samples accurately simulate deep soil conditions at 1 g. The system also includes an In-flight Robot that provides the capability to perform experiments while the centrifuge is in operations, as well as a 2–D shaker and associated 2–D Laminar Box that permit earthquake simulations while in flight. However prior to the implementation of the Auxiliary Axis, pilings were limited to a maximum usable length of approximately 15cm. The objective of Auxiliary Axis is to provide the capability to handle long pilings (up to 35cm) in situations where both the 2–D Shaker and 2–D Laminar Box are used. The Aux Axis is attached to the exterior of the in-flight robot when needed, and removed when not. The Aux Axis is designed to perform in a 50 g’s environment which holds some unique engineering concerns. It is designed so that installation and removal is as simple as possible, and can typically be completed in about 30 minutes. The Aux Axis is powered by the existing robot Z axis motor and belt drive system. Consequently, both the Z axis and the Aux Axis move simultaneously when the Aux Axis is installed. The Aux Axis is geared approximately 8.42 times higher than the Z axis so that it moves much further than the Z axis during operation. This permits the pilings; which are attached to the Aux Axis, to be fully inserted into the soil sample before the Z axis has moved far enough to interfere with the top of the 2–D Laminar Box.
Integral Design for Starting a Culture Change in Dutch Building Design Practice
Authors: Zeiler Wim , Quanjel Emile
Published: May 2009

Since 2001 an ‘integral approach’ to building design has been propagated within Dutch building design practice, through continuously developing ‘learning by doing’ workshops. The organization of workshops started during ‘Integral Design’ project in 2000 that was conducted by the Dutch Society for Building Services (TVVL), the Royal Institute of Dutch Architects (BNA) and Delft University of Technology (TUD). The main focus of the project, which ended in 2003, was to raise the awareness of different disciplines about each others positions and problems in relation to building design, and to give an overview of issues influencing design integration and possible solution directions. The used workshops create a setting where the knowledge can be generated and regenerated in relationship to the knowledge development-triangle, in a realistic setting; the Reflexive Practice. In this paper we will explain the results of workshops, give an overview of participants’ assessments (more than 180 professionals took part in TVVL-BNA-TUD workshops) and reflect on preliminary results / conclusions.
Vibration Resonances in a Planetary Gear Ring: Effects of Mesh Phasing and Contact Ratio
Authors: Vangipuram Canchi Sripathi , Parker Robert G.
Published: May 2009

Parametric excitation of a rotating ring subject to moving time-varying stiffnesses have previously been investigated and given as closed form expressions in the system parameters. These conditions are applied to identify ring gear parametric instabilities in a planetary gear system. Certain mesh phasing and contact ratio conditions suppress parametric instabilities, and these conditions are presented with examples.