bluuebunny/crossref_metadata_2025 huggingface dataset:
Five Pad Tilting Pad Bearing Design and Lateral Vibration Characteristics of Small Gas Turbine Supported by It and Roller Bearing
Authors: Ha Jin Woong , Myung Ji Ho , Suk Jhin Ik
Published: June 2012

In tilting pad bearing design process, the selection of the proper configuration type of either a Load-Between-Pad (LBP) or Load-On-Pad (LOP) as well as preload and pivot offset conditions is to be carefully considered. Also the bearing needs to be designed in order to be suited for the rotor-bearing system and operating condition. In this paper, it is observed that the static and dynamic characteristics of a five pad tilting pad bearing for the LBP and LOP configurations are influenced by the variation of preload and pivot offset. In this context, rotor dynamic analysis of the 5 MW industrial gas turbine supported by the tilting pad bearing at the front and roller bearing at the rear is carried out based on the dynamic coefficients of the tilting pad bearing investigated. The result shows that two rigid body critical modes experience various changes according to the influence of the tilting pad bearing uniquely applied to one side of this machine. Mainly, the second critical speed, the rigid body mode of conical shape with high whirling in the tilting pad bearing, is significantly changed by preload and pivot offset regardless of the LBP and LOP configurations. And the first critical mode, the rigid body mode of conical shape with high whirling in the roller bearing, is sensitively affected by preload applied to the LOP configuration and by its asymmetric dynamic properties.
Traction Control Using an Anthropomimetic Approach
Authors: Kirchner William T. , Southward Steve C.
Published: June 2012

Human expert drivers have the unique ability to combine correlated sensory inputs with repetitive learning to build complex perceptive models of the vehicle dynamics as well as certain key aspects of the tire-ground interface. This ability offers significant advantages for navigating a vehicle through the spatial and temporal uncertainties in a given environment. Conventional traction control algorithms utilize measurements of wheel slip to help insure that the wheels do not enter into an excessive slip condition such as burnout. Unfortunately, this approach has significant restrictions such as an implicit requirement that the tire-ground interface be uniform and fairly well known. In this paper, a novel approach to traction control is developed using an anthropomimetic control synthesis strategy. The proposed anthropomimetic traction control algorithm operates on the same correlated input signals that a human expert driver would in order to maximize traction; however, this is a very different strategy than any conventional traction control algorithms based on regulating wheel slip. A gradient ascent approach is at the heart of the proposed anthropomimetic control algorithm, and a real-time implementation is described using linear operator techniques, even though the tire-ground interface is highly non-linear. Performance of the proposed anthropomimetic traction control algorithm is demonstrated using a simple longitudinal traction case study.
Improvement of Positioning Error on a Ball Screw Drive System by Liquid-Cooling
Authors: Xu Zhezhu , Zhang Qi , Lyu Sungki
Published: June 2012

The demand for higher productivity and tight part tolerances requires machine tools to have faster and more accurate feed drive system. As tried and tested technology, ball screw drive systems are still used in majority of machine tools due to their low cost and high stiffness. A high speed ball screw drive system natually generates more heat and results in greater positioning error, adversely affecting the accuracy of machined parts. In order to estimate the positioning error of the ball screw system and effectiveness of the liquid-cooling system, all possible heat gain-loss sources were analyzed and calculated as calculation factors. The following paper also presents degree of positioning error improvement which employed circulation liquid-cooling system and forced liquid-cooling system. Comparing the experimental results and the forcasts, it shows that sensational cooling performance and high consistency of reality and prediction are displayed.
Towards Enabling Visual Design Exploration Involving Multiple Abstractions of Design Descriptions
Authors: Devanathan Srikanth , Ramani Karthik
Published: June 2012

Designers use several visual tools for exploring and understanding design problems and solutions. House of Quality (HoQ), function-structure, Morphological matrices, concept selection tables, 2D drawings are some of the visual tools and representations used in mechanical design. In this article we attempt to connect these visual tools and their underlying models to support exploration in early design using a representation called the working knowledge model (WKM). We identify two key aspects in design that are important for establishing such connections: different abstractions are used to describe the same design element, and several alternatives are considered during exploration. The constituent elements of the visual tools such as engineering characteristics (ECs) in a HoQ are described using classes of the information model. A simple wiki-based implementation is described that allows the user to tag the wiki text with WKM classes, which is then extracted to populate a database. This information is used by visual tools that can be embedded within a wiki page; the decisions taken by the user using these visual tools are then incorporated back into the WKM database and the wiki is updated if needed. A case study of the design of an automotive flow control valve is described to demonstrate the prototype.
Service Information Database for Consumer Acceptance
Authors: Iino Kenji , Nakao Masayuki , Hayashi Tsukasa
Published: June 2012

Hardly any engineering product is free of trouble and it has to go through service work, corrective or preventive. Fixing a mechanical pencil with a jammed lead is relatively an easy task for a mechanical engineer, whereas maintaining a power plant requires thorough planning, material handling, work order processing, and huge workforce. Naturally service work for large structures require a well designed database. The authors have shown [1] the importance of feeding service information back to the designer for authorization so the serviceperson will not “invent” maintenance work that may lead to product failure. This paper further suggests opening the whole service process to the public. The idea is especially valuable for some industries that need public acceptance, e.g., nuclear power generation. Nuclear power generation is often a subject of debate for public acceptance. This paper discusses two incidents of cover-ups by utility companies that caused large setback in their public acceptance, one case of overreaction triggered by the media showing dramatic accident scenes without explaining what was going wrong, and an example of poor management that cost a utility company its credence with the public. Up to the time of these incidents utility companies, out of the mindset of “Public do not understand our highly technical operation so telling them what is going on just creates confusion,” tended not to fully explain events that may have affected the public. Thanks to the way information flows around the world these days, even though we may not follow the “techy” words, there are those that understand the phenomena and are good at rephrasing the information so we can easily understand them. The utility company in the poor management case, Chugoku Electric Power Company (ENERGIA), in its efforts to recover the public trust, started a new service information system on the web that opens information about troubles and nonconformance in their plants to the public. This paper explains this new system that is currently in operation. It is a total change in the way a utility company interacts with the public. The courageous step by ENERGIA raises the public knowledge and awareness of nuclear power generation and assures security and safety to the society. The INTERNET is making it harder for companies, administration, educational institutions or any other entities to operate without public acceptance. Opening information is a way we all have to get used to in the coming years.
Micro-Scale Surface Texture Design for Improved Scuffing Resistance in Gear Applications
Authors: Greco Aaron , Ajayi Oyelayo , Erck Robert
Published: June 2012

The reliability and durability of gear components are critical issues especially in advanced power transmissions subject to increased power density and extreme operating conditions. In general the three main tribological failure modes present in gear tooth contact are: wear, contact fatigue/pitting, and scuffing. The present work investigates the influence of surface texturing in the form of micro-scale dimples as a method to enhance scuff resistance. Flat H13 steel samples were micro-dimpled using a laser surface texturing process. For scuffing and wear evaluation the flats were tested in point contact under lubricated linear reciprocating sliding. A threefold increase in scuffing resistance was observed for textured surfaces over comparable non-textured flats, however, for prolonged operation at high loads an increase wear rate of the counterface is observed. For gear application the design and location of surface texture requires careful consideration to balance scuffing resistance with potential influence to increased wear and fatigue pitting.
GPU-Friendly Preconditioners for Efficient 3-D Finite Element Analysis of Thin Structures
Authors: Mishra Vikalp , Suresh Krishnan
Published: June 2012

A serious computational bottle-neck in finite element analysis today is the solution of the underlying system of equations. To alleviate this problem, researchers have proposed the use of graphics programmable units (GPU) for fast iterative solution of such equations. Indeed, researchers have shown that a GPU-implementation of a double-precision sparse-matrix-vector multiplication (that underlies all iterative methods) is approximately an order of magnitude faster than that of an optimized CPU implementation. Unfortunately, fast matrix-vector multiplication alone is insufficient… a good preconditioner is necessary for rapid convergence. Furthermore, most modern preconditioners, such as incomplete Cholesky, are expensive to compute, and cannot be easily ported to the GPU. In this paper, we propose a special class of preconditioners for the analysis of thin structures, such as beams and plates. The proposed preconditioners are developed by combining the multi-grid method, with recently developed dual-representation method for thin structures. It is shown, that these preconditioners are computationally inexpensive, perform better than standard pre-conditioners, and can be easily ported to the GPU.
Synthesizing Parallel Flexure Concepts That Mimic the Complex Kinematics of Serial Flexures Using Displaced Screw Systems
Authors: Hopkins Jonathan B.
Published: June 2012

The aim of this paper is to introduce the theory necessary to synthesize a new type of parallel flexure system that mimics the complex kinematics of serial flexure systems using a comprehensive library of geometric shapes that represent systems of screws. By displacing these shapes far from the system’s motion stage, designers may rapidly visualize every parallel flexure concept that possesses degrees of freedom (DOFs), which approximate DOFs only achievable by serial flexure systems for small motions. In this way, designers may generate every flexure concept that utilizes the advantages of both parallel and serial flexure systems. This paper’s impact is most significant to the design of precision motion stages, optical mounts, microscopy stages, and general purpose flexure bearings. Two case studies are provided to demonstrate the utility of this theory.
A Modified Formulation for Automatic Synthesis of Planar Linkage Mechanisms
Authors: Jang Gang-Won , Nam Sang Jun , Kim Yoon Young
Published: June 2012

The idea of automatic mechanism synthesis is to find an optimal linkage type as well as its geometric dimensions for a given problem without using any pre-determined linkage type. As the first step towards the automatic mechanism synthesis, the authors proposed the use of unified planar linkage consisting of rigid blocks connected by stiffness-varying zero-length springs and formulated the synthesis problem as the iterative design optimization problem. In this investigation, we extend the automatic mechanism synthesis idea to more realistic large-sized problems by resolving several numerical difficulties observed in the earlier formulation such as instable convergence and many local optima. In particular, the objective and constraint functions in the optimization formulation are newly selected. The rationale for choosing such functions is given and the effectiveness of the proposed problem formulation is verified by designing planar mechanisms of complete paths.
Failure Mode and Effects Analysis of Compressor Blades of Aeroengines Using Dempster-Shafer Evidence Theory
Authors: Yang Jianping , Huang Hong-Zhong , He Li-Ping , Wen Dunwei , Zhu Shun-Peng
Published: June 2012

Compressor blades are a major component of an aeroengine. Failure mode and effects analysis (FMEA), especially, the risk priority order of failure modes, is essential in its design. The risk priority number (RPN) has been extensively used to the risk priority order of failure modes. When multiple experts give their different risk evaluation information to one failure mode, which may be imprecise and uncertain, the traditional RPN cannot deal with the problem. In this paper, the modified Dempster-Shafter (D-S) is adopted to aggregate the different evaluation information by considering multiple experts’ evaluation opinions, multiple failure modes and three risk factors respectively. The simplified discernment frame is proposed according to the practical application. Moreover, the mean value of the new RPN is used to risk priority order of multiple failure modes. Finally, the method is used to deal with the risk priority evaluation of the failure modes of compressor blades of an aeroengine under multiple sources of different and uncertain evaluation information. The consequence of the method is rational and efficient.
A Study on Planetary Gear Dynamics With Tooth Profile Modification
Authors: Bahk Cheon-Jae , Parker Robert G.
Published: June 2012

This study investigates the impact of tooth profile modification on planetary gear dynamic response. Micro-scale geometric deviations from an involute gear tooth profile add an additional excitation source, potentially reducing gear vibration. In order to take account of the excitation, tooth profile modification is included in an analytical planetary gear model. Nonlinearity due to tooth contact loss is considered. Time-varying mesh stiffness and both rotational and translational gear motions are modeled. The accuracy of the proposed model for dynamic analysis is correlated against a benchmark finite element analysis. Perturbation analysis is employed to obtain a closed-form approximation of planetary gear dynamic response with tooth profile modification. Mathematical expressions from the perturbation solution allow one to easily estimate the peak amplitude of resonant response using known parameters. Variation of the peak amplitude with the amount and the length of profile modification illustrates the effect of tooth profile modification on planetary gear dynamic response. For a given external load, the tooth profile modification parameters for minimal response are readily obtained. Static transmission error and dynamic response are minimized at different amounts of profile modification, which contradicts common practical thinking regarding strong correlation between static transmission error and dynamic response. Contrary to the expectation of further reduced vibration, the combination of the optimum sun-planet and ring-planet mesh tooth profile modifications that minimizes response when applied individually increases dynamic response.
Comparison of Finite Element Solutions of Non-Rational B-Spline and ANCF Elements in the Analysis of Flexible Multibody Systems
Authors: Yamashita Hiroki , Sugiyama Hiroyuki
Published: June 2012

In this investigation, comparison of finite element solutions obtained using the B-spline approach and the absolute nodal coordinate formulation (ANCF) is performed. Furthermore, equivalence of the two formulations with different orders of polynomials and degrees of continuity is demonstrated by several numerical examples. The degree of continuity can be easily controlled in B-spline elements by changing knot multiplicities, while continuity conditions associated with higher order derivatives need to be imposed to achieve C2 and higher continuities in ANCF elements. In order to compare element performances of the third and quartic B-spline and ANCF elements, the three-node quartic ANCF beam element is developed. It is demonstrated in several numerical examples that use of B-spline and ANCF elements with same orders and continuities leads to identical results. Furthermore, effects of polynomial orders and continuities on the accuracy and numerical convergence are demonstrated.
Multi-Pulse Chaotic Dynamics of a Cantilever Plate by Using Extended Melnikov Method
Authors: Zhang Wei , Huang Yutong
Published: June 2012

The nonlinear dynamic behavior of a laminated composite cantilever plate is investigated in this paper. The extended Melnikov method is employed to predict the multi-pulse chaotic motions of the cantilever plate. The model is based on the wing flutter of the airplane. The cantilever plate is considered to be subjected to the in-plane and transversal excitations. The Reddy’s high-order shear deformation theory as well as von Ka´rma´n type equations are used to establish the equation of motion for the cantilever plate. Applying the Galerkin procedure to the partial differential governing equations of motion for the system, we obtain equations of transverse displacement. Then the method of multiple scales is used to obtain the averaged equations. Finally, the extended Melnikov method is used to analyze the nonlinear behavior in the cantilever plate system. The theoretical result shows that there exists multi-pulse jumping movement. The numerical results also reveal such chaotic phenomenon.
Preventing Misuse of Consumer Products
Authors: Nakao Masayuki , Miyamura Toshio , Tsuchiya Kensuke , Iino Kenji
Published: June 2012

Accidents with consumer products originate from either product defects or misuse. These two explicit causes result from aging degradation, coupled design, or in some cases from causes that are unknown. We analyzed over 600 cases of past accidents with consumer products in the Japanese market. Of the 309 cases of product defects, 51% were caused by aging degradation, and coupled design was responsible for 66% of the 296 cases of misuse. Evaluation, from the viewpoint of axiomatic design, of these coupled design caused misuse cases revealed that over half of them had coupling of the operational functional requirement in the design stage. These cases consist about 38% of the 296 misuse cases. Instead of blaming the user for misuse, if the designer carefully removes such coupling in the design stage, such accidents can be avoided. In the actual design work, changing part configurations, or adding sensors or interlocks can decouple operational functional requirements.
Vibration Suppression for a Flexible Link Robot Using Acceleration and/or Angular Rate Measurements and a Flatness Based Trajectory Control
Authors: Staufer Peter , Gattringer Hubert , Bremer Hartmut
Published: June 2012

This paper focuses on trajectory control of an articulated robot with two flexible links and three joints, for a base, a shoulder and an elbow. The aim of the present contribution is to use angular rate and acceleration sensors for vibration damping instead of strain gauges measurements. Applying strain gauges for the measurements of curvatures on industrial applications is often technically difficult and expensive. Operating with model based control approaches, the equations of motion are the essential prerequisites and therefore various mathematical models and assumptions are introduced. The first model is developed assuming Euler-Bernoulli-Beams and the Ritz approach. Under the condition of small elastic deformations a second model is computed, approximating the beam elasticity with linear springs and dampers. This so called lumped element model is modified in a further step, in order to apply common flatness based approaches. With these preparations a flatness based control, consisting of a feedforward and a feedback part, is shown. The latter one uses angular rate or acceleration measurements. The proposed control strategies are finally validated by several experiments.
Switchability Conditions of Motions in a Nonlinear, Friction-Induced Oscillator
Authors: Luo Albert C. J. , Huang Jianzhe
Published: June 2012

In this paper, the analytical conditions for motion switchability in a nonlinear frictional oscillator are developed. Such analytical conditions provide the motion switching mechanism in such a nonlinear friction oscillator. Periodic motions are presented through phase planes and switching sections for a better understanding of such motion mechanism.
Design Concepts for Shape-Shifting Surfaces
Authors: Lusk Craig , Montalbano Paul
Published: June 2012

This paper presents concepts for Shape-Shifting Surfaces (SSSs), i.e. surfaces that retain their effectiveness as physical barriers while undergoing changes in shape. These shape changes could be motions like expanding, shrinking, twisting, encircling, wiggling, swallowing or constricting that make the surface more effective at performing its function. The SSSs are a novel concept, and are composed of tiled arrays of polygonal cells, each cell consisting of specifically-designed compliant flexures attached to specifically-shaped overlapping thin plates or shells. Applications for such surfaces are anticipated at the micro-scale in cellular engineering and at the macro-scale for biomedical applications, recreational uses, national security, and environmental protection; each will be stem from the foundational concepts described in this paper.
Further Evaluation of Spur Gear Tooth Profile Designs Used in Heavily Loaded Transmissions
Authors: Yıldırım Nihat , I˙s¸c¸i Hakan , Akpolat Abdullah
Published: June 2012

Aerospace applications require special procedures for component design and manufacturing. Spur gears of different designs, because of their simpler geometries, are used in vital units-transmissions of helicopters and alike aerospace vehicles. In this study, performances of various profile designs of previously researched low and high contact ratio spur gears with some realistic design parameters are studied. Effects of the realistic parameters of variable tooth pair stiffness, relief shape, and adjacent pitch error on Transmission Error (TE), tooth loads and root stresses are presented; composition of these parameters determines the efficiency of the gearbox assembly. Detail of minimization of tooth root stress through optimized/proper design of relief is described. More comprehensive comparison of the gear tooth profile design cases is done to be able to guide aerospace transmission designers for practical applications with realistic parameters for each of the design cases. A preference order is done among the design cases, depending on effect of some design parameters on the results such as tooth loads, tooth root stresses, TE curves and peak-to-peak TE values.
State Dependent Riccati Equation (SDRE) Control Method Applied in Cancellation of a Parametric Resonance in a Magnetically Levitated Body
Authors: Chavarette Fa´bio Roberto , Balthazar Jose´ Manoel , dos Reis Ce´lia Aparecida , Peruzzi Nelson Jose´
Published: June 2012

Here, a simplified dynamical model of a magnetically levitated body is considered. The origin of an inertial Cartesian reference frame is set at the pivot point of the pendulum on the levitated body in its static equilibrium state (ie, the gap between the magnet on the base and the magnet on the body, in this state). The governing equations of motion has been derived and the characteristic feature of the strategy is the exploitation of the nonlinear effect of the inertial force associated, with the motion of a pendulum-type vibration absorber driven, by an appropriate control torque [4]. In the present paper, we analyzed the nonlinear dynamics of problem, discussed the energy transfer between the main system and the pendulum in time, and developed State Dependent Riccati Equation (SDRE) control design to reducing the unstable oscillatory movement of the magnetically levitated body to a stable fixed point. The simulations results showed the effectiveness of the (SDRE) control design.
High Speed Algorithm for Computation of Fractional Differentiation and Integration
Authors: Fukunaga Masataka , Shimizu Nobuyuki
Published: June 2012

A high speed algorithm for computing fractional differentiations and fractional integrations in fractional differential equations is proposed. In this algorithm the stored data is not the history of the function to be differentiated or integrated but the history of the weighted integrals of the function. It is shown that, by the computational method based on the new algorithm, the integration time only increases in proportion to n log n, different from n2 by a standard method, for n steps of integrations of a differential integration.
Effects of Assembly Errors on Crossed Beveloid Gear Tooth Contact and Dynamic Response
Authors: Zhu Caichao , Song Chaosheng , Lim Teik C. , Peng Tao
Published: June 2012

It is known that the tooth flank geometry, assembly errors and the operating conditions of a gear pair have significant influence on tooth contact, load distribution and dynamic response. However, the study of the effects of assembly errors on the mesh characteristics and dynamic response for crossed beveloid gears has been limited due to the complicated geometry and time-varying mesh characteristics. In this study, three types of assembly errors including shaft angle, offset and gear axial position error are examined based on a synthesized mesh model and a three-dimensional elastically coupled rigid-body dynamic model. Also, the relation between a dominant geometry design parameter that is the crossed angle between the first principal directions of the tooth surface curvatures (FPD-angle) and the sensitivity of mesh characteristics and dynamic response subject to assembly errors is investigated. Through the sensitivity analysis with different FPD-angles, the shaft angle error is found to be the most sensitive factor affecting the mesh and dynamic behaviors of crossed beveloid gear set. On the other hand, the gear axial position errors have the least influence on the mesh characteristics and dynamic response. In most cases, the influences of assembly errors on mesh characteristics and dynamics become weaker with the increase of FPD-angle.
Performance of Injection-Molded Plastic Helical Gears Finished by Hot Rolling
Authors: Nakamura Morimasa , Katayama Atsushi , Moriwaki Ichiro
Published: June 2012

A hot-roll finishing was proposed as a simple finishing method for plastic gears. In the hot-roll finishing, plastic work gears are finished by meshing with a heated copper die wheel. In the previous study, a hot-roll finishing rig for plastic gears was developed, and it was confirmed that tooth profiles of hobbed plastic gears are improved by the finishing. Thus, the hot-roll finishing could also be effective for injection-molded plastic gears. In the present paper, appropriate hot-roll finishing procedures for injection-molded polyoxymethylene (POM) helical gears were pursued. In the injection molding, an inadequate mold easily allows large slope deviations on a tooth profile and trace. The hot-roll finishing can reduce the slope deviations, but induces form deviations especially on the profile. Tests of injection-molded and hot-roll-finished plastic gears were performed on a self-produced gear roller test rig and a self-produced fatigue rig, and a transmission error and load capacity were estimated. Compared with injection-molded gears, hot-roll-finished plastic gears showed small transmission error, while a load capacity was at the almost same level. As a result, the hot-roll finishing is effective for improving a transmission error of injection-molded plastic gears.
Planning Manipulation and Grasping Tasks With a Redundant Arm
Authors: Gray Steven R. , Romano Joseph M. , Brindza Jordan , Kim Soonkyum , Kuchenbecker Katherine J. , Kumar Vijay
Published: June 2012

This paper presents an approach to analysis and planning for autonomous manipulation tasks using a commercially available robotic arm and hand. We discuss hardware implementation, software architecture, and state machine behaviors. The inverse kinematics of the seven-degree-of-freedom manipulator are analytically derived with special attention to deterministically resolving the redundancy at the position level. Appropriate grasps are generated given the perceived position and orientation of the target object. Planning for the arm is accomplished in joint space using an RRT* implementation. Our implementation is able to detect an arbitrarily placed object in the workspace, generate a plan for the arm and hand avoiding obstacles, and execute the planned manipulation task. To show the efficacy of our approach, we present experiments in which the system autonomously grasps a canteen and a flashlight.
Feedback Controlled Optomechanical Force Sensor
Authors: Pratt Jon R. , Wilkinson Paul , Shaw Gordon
Published: June 2012

We present a new servo controllable force sensor that exploits photon momentum forces for the identification, calibration, and control of its dynamic properties. The sensor comprises a millimeter-scale glass cantilever, a low-noise fiber interferometer for detection of the cantilever deflection, and a high-power, intensity-modulated fiber laser to apply optical actuation forces. Combined with appropriate digital and analog signal processing, the sensor has been operated as a feedback-cooled low-noise force sensor, and as a self-excited oscillator governed by the familiar Rayleigh equation. Operated in this self-excited Quber mode, it appears well suited for noncontact, frequency modulated force gradient detection such as in atom discrimination. Here, we briefly lay out the principles of the sensor and provide examples of its performance, including the demonstration of feedback cooling and the ability to induce controlled limit cycle oscillations with atomic scale amplitudes.
Quantifying Uncertainty for Planar Pseudo-Rigid Body Models
Authors: Lusk Craig P.
Published: June 2012

The Pseudo-Rigid-Body Model (PRBM) is an important technique for analyzing and synthesizing compliant mechanisms. This paper describes an approach for generalizing the PRBM and for quantifying its accuracy. The Bernoulli-Euler beam equations are solved and the solution is represented using a phase-portrait. It is shown that the slope-curvature relations for all uniform fixed free-beams can be represented on a single phase portrait. This representation allows for data about PRBM representations for each cantilever beam to be efficiently presented, and for broad conclusions to be drawn, e.g. that the relative position error associated with a simple version of the PRBM is never greater than 7%.
Unicycle Lateral Control by Body Positioning
Authors: Schiehlen Werner , Seifried Robert , Glaser Thomas
Published: June 2012

Unicycles are inherently unstable vehicles and require longitudinal and lateral control including pitch and roll motion. The one wheel is propelled by the rider and provides the longitudinal motion and the pitch control of the vehicle as well. The roll control is achieved by balancing carried out by the rider since the nonholonomic constraint does not allow a lateral displacement of the wheel–guideway contact point. Usually, forces and torques are used as control inputs even if human motions are mainly position controlled by visual feedback and not force controlled. In this paper the roll motion of a unicycle is considered. The balancing is obtained by the upper body’s roll motion which is used as control input. It is shown that balancing can be modeled by an inverted double pendulum where the relative acceleration of the upper body is chosen as control variable. Due to the nominal vertical position of the unicycle running straight ahead the balancing is represented by linear equations of motion and linear control theory is applied. It turns out that from simulations and experiments that properly controlled body positioning ensures balancing, too.
On the Use of the Instantaneous Angular Speed Measurement in Non Stationary Mechanism Monitoring
Authors: Andre´ Hugo , Re´mond Didier , Bourdon Adeline
Published: June 2012

Power transmission faults are one important cause of machine downtime many production activities are working to prevail. Vibration monitoring tools have achieved this role on the assumption that the stationary condition hypothesis is maintained. Several industries, including wind energy production, are however demanding to observe mechanical or electrical rotating components behaviour at variable speeds. Instantaneous angular speed measurement has been recently proven able to detect localized faults in bearings using only an encoder close from the source of the defect. This paper presents the results obtained from a large span experiment on a 2MW wind turbine. The uniqueness of the sensor used to monitor the whole line shafting along with the continuous non stationary conditions are so many difficulties cumulated on this attempt. Two basic signal processing tools are theoretically defined and experimentally applied in an original way on the Instantaneous Angular Speed measurement to efficiently tackle these practical issues.
On the Identification of Chaos From Frequency Content
Authors: Wiebe Richard , Virgin Lawrence N.
Published: June 2012

The characterization of chaos as a random-like response from a deterministic dynamical system with an extreme sensitivity to initial conditions is well-established, and has provided a stimulus to research in nonlinear dynamical systems in general. In a formal sense, the computation of the Lyapunov Exponent spectrum establishes a quantitative measure, with at least one positive Lyapunov Exponent (and generally bounded motion) indicating a local exponential divergence of adjacent trajectories. However, although the extraction of Lyapunov Exponents can be accomplished with (necessarily noisy) experimental data, this is still a relatively data-intensive and sensitive endeavor. We present here an alternative, pragmatic approach to identifying chaos as a function of system parameters using response frequency characteristics and extending the concept of the spectrogram.
Investigation of Mechanical Differentials as Continuously Variable Transmissions
Authors: Wells Dax B. , Groen Benjamin C. , Todd Robert H.
Published: June 2012

In recent years the increasing demand for fuel efficient and less pollutant vehicles has stimulated the development of hybrid and electric vehicles. These vehicle platforms often incorporate drivetrains which utilize multiple power sources for vehicle propulsion to increase fuel mileage and reduce emissions. Understanding the torque and RPM relationship within the power transmission device used to combine power sources is fundamental to overcoming the design challenges associated with hybrid/electric vehicle platforms. Results from this research include the fundamental torque and RPM relationships that exist in a multiple-input, single-output power transmission device. Results were deduced from a test incorporating two separate power inputs into a mechanical differential, which produced a single output. Testing showed that a mechanical differential has the ability to function as an infinitely variable transmission (IVT). Additionally, recommendations for overcoming some of the challenges associated with using a mechanical differential as a multiple-input, single-output device were identified.
Simulating Equipment Interaction With Predictive Dynamics
Authors: Choi Jun Hyeak , Bhatt Rajankumar , Chung Hyun-Joon , Arora Jasbir S. , Abdel-Malek Karim
Published: June 2012

Recent advances in predictive dynamics allow the user to not only predict physics based human motion simulations but also determine the actuation torques required to achieve those motions. The predictive dynamics approach uses optimization to predict motion while using many task based, physics based, and environment based constraints including the equations of motion. Many tasks have been simulated using this new method of predicting and simulating digital human motion, e.g. walking, running, stair climbing, and box lifting. In this research, we develop a method to predict the motion as well as effect of external equipment hanging on the digital human. The proposed method is tested on a simple case of a two degree of freedom serial chain mechanism with a simple passive system to behave as external equipment. In particular, the passive mass is assumed to be attached to the two links system with a spring and damper. The results of the proposed method are compared with the results obtained by integrating the equations of motion of the full three degree of freedom system.
Sustainable Manufacturing Indicator Repository
Authors: Sarkar Prabir , Joung Che Bong , Carrell John , Feng Shaw C.
Published: June 2012

Sustainable manufacturing promotes manufacturing processes that minimize environmental and social impacts while maintaining economic benefits. To achieve this, manufacturers seek metrics and measurement methods to enable them to track the progress and manage their manufacturing processes and product designs. A number of indicator sets have been devised to analyze and score sustainable manufacturing; however, presence of many indicator sets has created difficulty in selecting the appropriate set. This paper presents a sustainability indicator repository, called Sustainable Manufacturing Indicator Repository (SMIR), an integration and extension of thirteen popular sustainability indicator sets. From an extensive review of publicly available indicator sets, the SMIR is based on five dimensions of sustainability: environmental stewardship, economic growth, social well-being, technological advancement, and performance management. The purpose of the SMIR is to provide an organized set of centralized, Web-based, open, and neutral indicators that can be accessible by small and medium size manufacturing enterprises. The SMIR can be an application as well as educational tool for manufacturers by providing them with necessary information on in-process and off-line sustainability measures.
Reliability and Accuracy of Bootstrap and Monte Carlo Methods for Demand Distribution Modeling
Authors: Razu Swithin S. , Takai Shun
Published: June 2012

Estimation of demand is one of the most important tasks in new product development. How customers come to appreciate and decide to purchase a new product impacts demand and hence profit of the product. Unfortunately, when designers select a new product concept early in the product development process, the future demand of the new product is not known. Conjoint analysis is a statistical method that has been used to estimate a demand of a new product concept from customer survey data. Although conjoint analysis has been increasingly incorporated in design engineering as a method to estimate a demand of a new product design, it has not been fully employed to model demand uncertainty. This paper demonstrates and compares two approaches that use conjoint analysis data to model demand uncertainty: bootstrap of respondent choice data and Monte Carlo simulation of utility estimation errors. Reliability of demand distribution and accuracy of demand estimation are compared for the two approaches in an illustrative example.
Blade Vibration Suppression Using Friction Elements in Shrouding
Authors: Hajzˇman Michal , Byrtus Miroslav , Zeman Vladimi´r
Published: June 2012

The problem of two blades with a friction element is studied in order to analyze the effects of the friction on the undesirable vibration suppression. The simplified contact model between friction planes of the blade shrouding and the friction element is derived to be a fast computational tool comparing with a time-consuming finite element solution. The harmonic balance method is suitable for the linearization of originally nonlinear equations of motion under certain assumptions given on the excitation of the system and on its dynamic response. On the other hand the nonlinear equations of motion can be solved directly by their numerical integration, which is more time-consuming but it is not limited by given assumptions. The comparison of results of the harmonic balance method and of the numerical integration of motion equations is given in the paper.
Effect of Gear Tooth Crack on Spur Gear Dynamic Response by Simulation
Authors: Shao Yimin , Wang Xi , Chen Zaigang , Lim Teik C.
Published: June 2012

Geared transmission systems are widely applied to transmit power, torque and high rotational speed, and as well as change the direction of rotational motion. Their performances and efficiencies depend greatly on the integrity of the gear structure. Hence, health monitoring and fault detection in geared systems have gained much attention. Often, as a result of inappropriate operating conditions, application of heavy load beyond the designed capacity or end of fatigue life, gear faults frequently occur in practice. When fault happens, gear meshing characteristics, including mesh stiffness that is one of the important dynamic parameters, can be affected. This sudden change in mesh stiffness can induce shock vibration as the faulty gear tooth passes through the engagement zone. In this study, a finite element model representing the crack at the tooth root of a spur gear is developed. The theory is applied to investigate the effect of different crack sizes and the corresponding change in mesh stiffness. In addition, a lumped parameter model is formulated to examine the effect of tooth fault on gear dynamic response.
Static Balancing of Translational Parallel Mechanisms
Authors: van Dam Teunis , Lambert Patrice , Herder Just L.
Published: June 2012

Static balancing is a technique to create static equilibrium throughout a certain range of motion. Static balancing for spatially moving parallel manipulators tends to result in considerable added complexity which hampers application. This paper presents a simple static balancing technique for the subclass of translational parallel manipulators such as the Delta robot. Mathematically perfect static balance is achieved without addition of links. Only springs need to be added. The concept and the balancing conditions will be presented. A prototype is being manufactured at the time of writing which demonstrates the feasibility of the concept.
Adaptive Virtual Support Vector Machine for the Reliability Analysis of High-Dimensional Problems
Authors: Song Hyeongjin , Choi K. K. , Lee Ikjin , Zhao Liang , Lamb David
Published: June 2012

In this study, an efficient classification methodology is developed for reliability analysis while maintaining the accuracy level similar to or better than existing response surface methods. The sampling-based reliability analysis requires only the classification information — a success or a failure – but the response surface methods provide real function values as their output, which requires more computational effort. The problem is even more challenging to deal with high-dimensional problems due to the curse of dimensionality. In the newly proposed virtual support vector machine (VSVM), virtual samples are generated near the limit state function by using linear or Kriging-based approximations. The exact function values are used for approximations of virtual samples to improve accuracy of the resulting VSVM decision function. By introducing the virtual samples, VSVM can overcome the deficiency in existing classification methods where only classified function values are used as their input. The universal Kriging method is used to obtain virtual samples to improve the accuracy of the decision function for highly nonlinear problems. A sequential sampling strategy that chooses a new sample near the true limit state function is integrated with VSVM to maximize the accuracy. Examples show the proposed adaptive VSVM yields better efficiency in terms of the modeling time and the number of required samples while maintaining similar level or better accuracy especially for high-dimensional problems.
On the S-(nS)PU-SPU and S-(nS)PU-2SPU Under-Actuated Wrists
Authors: Di Gregorio Raffaele
Published: June 2012

In a previous work, this author showed that ten topologies for under-actuated parallel wrists can be generated from the fully-parallel wrist. Three of them are obtained by simply replacing a spherical pair (S) with a nonholonomic spherical pair (nS). The S-(nS)PU-SPU, and S-(nS)PU-2SPU wrists are two of these three. The position analysis of these two wrists is studied in this paper. In particular, all the four position-analysis problems, which are necessary for implementing their path planning, are addressed and solved in closed-form. Despite their different topology, the position-analysis of these two wrists can be practically solved by using the same formulas and algorithms. Based on the deduced formulas, a path-planning algorithm is proposed. The obtained results make the studied wrist topologies able to replace “ordinary” wrists in the manipulation tasks which do not require tracking.
An Inverse Analysis Method for Estimation of Heat Flux and Temperature-Dependence of Heat Transfer Coefficient
Authors: Kubo Shiro , Ioka Seiji
Published: June 2012

Transient thermal stresses develop in pipes during start-up and shut-down. In previous papers the present authors [1–4] proposed an inverse method for determining the optimum thermal inlet liquid temperature history which reduced the maximum transient thermal stress in pipes. The papers considered multiphysics including heat conduction, heat transfer, and elastic deformation. The inverse method used the relationship between inner surface temperature history, transient temperature distribution and transient thermal stresses. The coefficient of heat transfer plays an important role in the evaluation of thermal stress. In this study an inverse method was developed for estimating heat flux and temperature-dependence of the coefficient of heat transfer from the history of the outer surface temperature and the liquid temperature. The method used the relationship between the outer surface temperature and the inner surface temperature. For the regularization of solution the function expansion method was applied in expressing the history of flux on the inner surface. Numerical simulations demonstrated the usefulness of the proposed inverse analysis method. By examining the effect of measurement errors of temperature on the estimation, the robustness of the method was shown.
A Hierarchical, Heterogeneous CAD Modeling Approach
Authors: Rosen David W. , Jeong Namin , Wang Yan
Published: June 2012

Integration of material composition, microstructure, and mechanical properties with geometry information enables many product development activities, including design, analysis, and manufacturing. In this paper, we propose the modeling of part geometry and microstructure by using a new hierarchical modeling method that utilizes a common geometric model for both macro-scale part geometry and material microstructure. A new surfacelet transform is introduced to model microstructure. The application of image processing methods enables multi-resolution representations of microstructure. Combined with methods from computational materials design, low resolution microstructure representations can be used to compute effective mechanical properties at the macro-scale. Wavelet decomposition was used to generate the low resolution representations. The models and methods are demonstrated with two examples, a simple continuous-fiber-reinforced composite and a nanofiber reinforced polymer material.