bluuebunny/crossref_metadata_2025 huggingface dataset:
A Novel Method for Input Selection for the Modeling of Nonlinear Dynamic Systems
Authors: Jiang Li , Latronico Elizabeth , Ni Jun
Published: July 2009

In order to handle increasingly complex engineering applications with highly nonlinear behaviors, various advanced system identification algorithms have been developed for control and diagnostic purposes. Since the performance of these algorithms depends significantly on the selection of input variables, a systematic input selection methodology is needed to identify the nonlinear relation between the input variables and system outputs, even in the presence of high correlation among the candidate input variables. The methodology proposed in this paper converts the problem of selecting appropriate input variables for the identification of a nonlinear dynamic system into one of a set of properly linearized models. In order to enable the approximation of the nonlinear system behavior with a set of linear models, a growing self-organizing map is employed to appropriately partition the system operating region into sub-regions via unsupervised learning. Evaluated based on the minimum description length principle, a model with its most related input variables is then selected using a genetic algorithm so that the computational burden can be reduced. The effectiveness of this methodology has been demonstrated with two simulation examples and a real-world example of modeling the air mass flow rate and intake manifold pressure in a diesel engine airflow system.
Experimental Calibration and Validation of Fault Diagnosis and Prognosis Algorithms for Automotive Electric Power Generation and Storage System
Authors: Li Weiwu , Suozzo Chris , Onori Simona , Rizzoni Giorgio , Salman Mutasim A. , Zhang Frank
Published: July 2009

This paper is a continuation of the work on the model-based fault diagnosis for the automotive electric power generation system (EPGS) presented in [5]. Based on the previous work on the subject, a new and optimized fault diagnosis algorithm for the EPGS system is developed. In this paper, the thresholds for the diagnosis algorithm are selected and calibrated based on experimental data. The test bench used for the calibration and validation process is discussed. Finally the effectiveness of the fault diagnosis algorithm and threshold selection is validated using experimental data collected from the test bench.
A Quasi-Newton Algorithm for LQG Controller Design With Variance Constraints
Authors: Conway Richard , Horowitz Roberto
Published: July 2009

In this paper, we present a new algorithm for solving the LQG control problem with variance constraints which utilizes derivative information about the relevant ℋ2 costs to achieve quasi-Newton convergence. Using a lifting procedure, this algorithm is then generalized to work with linear periodically time-varying systems. This algorithm is then applied to the design of controllers for hard disk drives in order to assess the limits of performance of a particular setup. It is demonstrated that just by utilizing multirate sampling and actuation characteristics (i.e. without changing the hardware), the performance of this particular setup can improved by more than 39%.
Efficient and Reliable Operation of Air-Side Economizers Using Extremum Seeking Control
Authors: Li Pengfei , Li Yaoyu , Seem John E.
Published: July 2009

For the heating, ventilating, and air conditioning (HVAC) systems for commercial buildings, there has been a greater demand for reducing energy consumption. The economizers have been developed as a class of energy-saving HVAC devices that may increase the energy efficiency by taking advantage of outdoor air during cool or cold weather. However, many economizers do not operate in the expected manner and waste even more energy than before installation, mostly due to the unreliable sensors and actuators in practice. Better control strategy is needed for optimal and robust operation. In this paper, an extremum seeking control (ESC) based self-optimizing strategy is proposed to minimize the energy consumption, with the feedback of chilled water supply command rather than the temperature and humidity measurements. The mechanical cooling load is minimized by seeking the optimal outdoor-air damper opening in real time. Such scheme does not need temperature and humidity sensors and depends much less on the knowledge of economizer model. Simulation was performed on a Modelica based transient model of a single-duct air-handling unit (AHU) developed with Dymola and AirConditioning Library. The simulation results demonstrated the potential of using ESC to achieve the minimal mechanical cooling load in a self-optimizing manner. In addition, an anti-windup ESC scheme is proposed to handle the ESC windup due to actuator (damper) saturation. The simulation results validated the effectiveness of the proposed anti-windup ESC.
Design and Control of a Shape Memory Alloy Actuated Robotic Catheter
Authors: Veeramani Arun S. , Crews John H. , Buckner Gregory D. , Owen Stephen B. , Cook Richard C. , Bolotin Gil
Published: July 2009

This paper details the development of a Neural Network (NN) controller for a Shape Memory Alloy (SMA) actuated catheter, with potential application to tele-operated cardiac ablation procedures. The robotic catheter prototype consists of a central tubular structure actuated by four SMA tendons. A dual-camera imaging system provides position feedback of the catheter tip. Open loop bending responses are obtained and associated nonlinearities are identified. A NN controller is designed using time-shifted input-output maps generated from randomized open loop measurements. The tracking performance of this NN controller is compared with PI/PID controllers for various reference trajectories.
Highway Evaluation of Terrain-Aided Localization Using Particle Filters
Authors: Dean Adam J. , Vemulapalli Pramod K. , Brennan Sean N.
Published: July 2009

This work evaluates a real-time algorithm to localize a vehicle on a highway in the direction of travel without the use of GPS. The algorithm uses a particle filter to estimate vehicle position along a map of road grade using real-time pitch measurements from an in-vehicle pitch sensor as the input. Experiments over 60 kilometers along Interstate I-80 and US Route 220 in Pennsylvania are used to demonstrate the algorithm, observe the speed of convergence, and evaluate several methods of implementation. The results indicate that the method can localize a vehicle with a position accuracy of 5 meters after traveling about 1 kilometer within the 60 kilometer map.
Robust Controller Interpolation via Parameterization
Authors: Hencey Brandon , Alleyne Andrew
Published: July 2009

Arbitrarily fast switching or blending among controllers often leads to reduced performance and possible instability. This paper presents a controller interpolation framework for robustly transitioning among controllers with respect to the H∞ norm. The framework leverages a robust controller parameterization, analogous to a Youla parameterization of nominally stabilizing controllers, to greatly simplify the robust controller interpolation problem. In addition, an explicit construction is provided for the robust interpolated controller. A practical example is presented in the form of a robust interpolated controller implemented on an electro-hydraulic test bed.
On-Off Control for Low-Power Servo Control in Piezoelectric Micro-Robotics
Authors: Oldham Kenn , Hahn Bongsu , Park Peter
Published: July 2009

Autonomous micro-systems require extremely strict power budgeting to provide useful battery lifetime and functionality. To produce bio-inspired terrestrial micro-robots, this power budget must encompass servo control of a set of robotic leg joints. Piezoelectric actuators can provide high-force actuation necessary for such an application, but driving circuitry for piezoelectric actuator control can consume excessive power. On-off control can reduce actuator power consumption by eliminating analog amplification and minimizing the number of on-off transitions required to perform a given leg joint motion, as compared to conventional PWM controllers. A sample on-off controller designed to require a limited number of on-off transitions from a prototype system is described, and trade-offs to motion accuracy and robustness as power consumption is reduced are discussed. Experimental tests are conducted on a macro-scale piezoelectric test-bed.
Discretized Lyapunov-Krasovskii Functional for Systems With Multiple Delay Channels
Authors: Li Hongfei , Gu Keqin
Published: July 2009

Many practical systems have a large number of state variables but only a few components have time delays. These delay components are often scalar or low dimensional, and involve single time delay in each component. A coupled differential-difference equation is well suited to formulate such systems. It is known that such a formulation is very general. Systems with multiple related or independent delays can be transformed into this standard form. Similar to regular time-delay systems, the existence of a quadratic Lyapunov-Krasovkii functional is necessary and sufficient for stability. This article discusses the discretization of such a quadratic Lyapunov-Krasovskii functional. Even for time-delay systems of retarded type, the formulation has significant advantage over the traditional formulation, as the size of the resulting linear matrix inequalities are drastically reduced for such systems. Indeed, the computational effort needed for checking stability of such a large system with a few low dimensional delays is quite reasonable.
Explanation for Low-Speed Stability Increases in Machining: Application of a Continuous Delay Model
Authors: Khasawneh Firas A. , Mann Brian P. , Insperger Tama´s , Ste´pa´n Gabor
Published: July 2009

This paper investigates the analysis of delay integro-differential equations to explain the increased stability behavior commonly observed at low cutting speeds in machining processes. In the past, this improved stability has been attributed to the energy dissipation from the interference between the workpiece and the tool relief face. In this study, an alternative physical explanation is described. In contrast to the conventional approach, which uses a point force acting at the tool tip, the cutting forces are distributed over the tool-chip interface. This approximation results in a second order delayed integro-differential equation for the system that involves a short and a discrete delay. A method for determining the stability of the system for an exponential shape function is described, and temporal finite element analysis is used to chart the stability regions. Comparisons are then made between the stability charts that use the conventional point force and those that use the distributed force model for continuous and interrupted turning.
The Motion of Solid Bodies in Potential Flow With Circulation: A Geometric Outlook
Authors: Vankerschaver Joris , Kanso Eva , Marsden Jerrold E.
Published: July 2009

The motion of a circular body in 2D potential flow is studied using symplectic reduction. The equations of motion are obtained starting from a kinetic-energy type system on a space of embeddings and reducing by the particle relabelling symmetry group and the special Euclidian group. In the process, we give a geometric interpretation for the Kutta-Joukowski lift force in terms of the curvature of a connection on the original phase space.
Automotive Powertrain Control Problems Involving Time Delay: An Adaptive Control Approach
Authors: Yildiz Yildiray , Annaswamy Anuradha , Yanakiev Diana , Kolmanovsky Ilya V.
Published: July 2009

This paper describes applications of the Adaptive Posicast Controller (APC) to Idle Speed Control (ISC) and Fuel-to-Air Ratio (FAR) control problems in automotive engines. The APC is an adaptive controller with explicit delay compensation built upon the ideas of the classical Smith Predictor, finite spectrum assignment and adaptive control. Experimental results are reported, which demonstrate improved performance compared to existing baseline controllers and effective handling of time delays and uncertainties in these applications. Aspects important to implementation and to reduction in calibration time and effort, including the selection of initial parameter values and their adaptation rates, preventing parameter drift and accounting for time-varying delay, are addressed.
The Von Neumann Threshold of Self-Reproducing Systems
Authors: Kabamba Pierre T.
Published: July 2009

This paper is devoted to the study of systems of entities that are capable of generating other entities of the same kind and, possibly, self-reproducing. The main technical issue addressed is to quantify the requirements that such entities must meet to be able to produce a progeny that is not degenerate, i.e., that has the same reproductive capability as the progenitor. A novel theory that allows an explicit quantification of these requirements is presented. The notion of generation rank of an entity is introduced, and it is proved that the generation process, in most cases, is degenerative in that it strictly and irreversibly decreases the generation rank from parent to descendant. It is also proved that there exists a threshold of rank such that this degeneracy can be avoided if and only if the entity has a generation rank that meets that threshold — this is the von Neumann rank threshold. Based on this threshold, an information threshold is derived, which quantifies the minimum amount of information that must be provided to specify an entity such that its descendants are not degenerate. Furthermore, a complexity threshold is obtained, which quantifies the minimum length of the description of that entity in a given language. Examples that illustrate the theory are provided.
Optimal Foraging Theory: Lessons and Application to Adaptive Engineering Systems
Authors: Lehman John T.
Published: July 2009

In biological systems, optimal strategy is generally defined as optimizing fitness, measured as reproductive value (RV), the expectation of producing surviving offspring from time t onward, given that an organism is in state S(t). Any action can be associated with an expectation of immediate reproductive success. Maximum RV results from the action that maximizes the sum of immediate and future surviving offspring. Adaptive biological behavior is the product of historical experience, heritability, individual variation, and differential fitness among individuals. Foraging tasks are a standard test bed for robot research because of their applicability to many problems. Optimal foraging theory offers explanations and predictions with direct applicability to engineering problems. Much theory development involves optimal solutions based on complete information about the system, but animals do not always conform to predictions of such models. Adaptive approximations to optimality in biological systems offer models for design of engineered systems.
Robust Absolute Vibration Suppression Controller
Authors: Peled Irit , Halevi Yoram
Published: July 2009

This paper considers the problem of controlling flexible systems, such as rotating shafts and gantry cranes, whose dynamics are described by the wave equation. In previous works, infinite dimension transfer functions with a special structure and an Absolute Vibration Suppression (AVS) linear controller were derived. The controller eliminates the infinite spectrum and results in a closed loop transfer function that has a low order rational part plus delay. The robustness properties of the AVS controller are investigated by using the Nyquist stability criterion. It is shown that in some cases it can be very sensitive to feedback, i.e. measurement and computation delays. A Robust AVS controller (RAVS), which is robust to feedback delays, is derived. The absolute suppression in AVS is only approximated in RAVS, but its performance compares favorably with that of other controllers.
The Combined Force/Position Control Systems for Manipulators
Authors: Filaretov Vladimir F. , Zuev Alexandr V.
Published: July 2009

In this paper, a new synthesis method of force/position control systems of robot manipulators is proposed. The control systems synthesized on the basis of this method without using force/moment sensors and other additional devices provide simultaneous dynamically accurate control of both the position of robot’s end-effector and the force (may be variable) exerted by end-effector on surfaces (object of work) along which it moves. The results of simulation of the manipulator with 3 degrees of freedom are presented. They confirm efficiency of the proposed method. Realization of synthesised control systems does not have large difficulties. These control systems can be realized with the help of a serial microprocessors.
Experimental and Finite Element Analysis of the Thermal-Electric Process in Monopolar Electrosurgical Thermal Management
Authors: Gee Jacob S. , Dodde Robert E. , Geiger James D. , Shih Albert J.
Published: July 2009

This study develops a thermal management system for the most commonly used energy-based surgical instrument: the monopolar electrosurgical device. Monopolar electrosurgery, using the same principle as the electrical discharge machining, is widely used to cut or remove tissue by sparks during surgical operations. This study develops a thermal management system consists of cooling channels placed around the active electrode to reduce the thermal damage to the tissue. Finite element modeling (FEM) was performed to analyze temperature distribution in biological tissue subject to heat generation by a commonly used monopolar electrosurgical device. The mathematical model was verified by comparing FEM predicted temperature distribution with experimental measurements. Exvivo experiments were performed with bovine liver tissue heated by a monopolar pencil electrode. The experimental data for 1 mm distance from the electrode is seen to fit within 1% of the predicted temperature values by the FEM simulation. The accuracy of the model decreases at further distances from the electrode. The inaccuracies are believed to be due to unaccounted temperature-dependent thermal conductivity. The addition of the cooling channels shows a reduction of the radial thermal damage of the tissue in both FEM simulations and ex-vivo experimental procedures.
Nanostructuring Pure Zr by Severe Plastic Deformation
Authors: Pe´rez-Prado M. T. , Zhilyaev A. P. , Jiang L. , Kassner M. E. , Ruano O. A.
Published: July 2009

Severe plastic deformation (SPD) techniques have now successfully been applied to fabricate a large number of nanostructured metals and alloys. Most studies have so far focused on fcc materials, although some studies on Ti and Mg also exist. In this work we describe the nanostructures resulting from processing pure Zr by high pressure torsion (HPT) and accumulative roll bonding (ARB).
Work Output Enhancement of Ferromagnetic Shape Memory Micro Actuators
Authors: Ganor Yaniv , Shilo Doron
Published: July 2009

Ferromagnetic shape memory (FSM) alloys are a class of materials which are both ferromagnetic and capable of undergoing a structural phase transformation. FSM alloys have significant advantage over conventional shape-memory temperature-based actuators because they can be remotly actuated by fast alternating magnetic fields. Therefore, FSM alloys attract keen attention as promising candidates for a variety of MEMS applications, as they can provide large strokes using small components. The most commonly used FSM alloy is Ni2MnGa and its off-stoichiometric alloys, which are used in commercial cm-scale FSM actuator. However, at the current stage, no experiments of the magneto-mechnical behavior of micro-scale actuators were conducted. Overall, the behavior of FSM alloys involves motion of twin boundaries and is significantly influenced by its microstructure. Based on a theoretical model, we have shown that down-scale specimens have finer twin boundary microstructure that consequently may increase the blocking stress characteristic such that it will enhance the output work for actuation. In light of this, a novel experimental method was realized to establish this conjecture and to provide comprehensive information on the behavior of small actuators. A series of tests demonstrated no actuation strain reduction up to extraordinary loads of 10MPa, and thus paves the route for engineering FSM high-power micro actuators by controlling their microstructure.
Modeling and Optimization of Integration Processes Under Severe Uncertainties
Authors: Tahan Meir , Ben-Asher Joseph Z.
Published: July 2009

The integration process of engineering systems frequently involves high uncertainties, such as units’ availability time, integration increment duration, testing costs, etc. In this work the uncertainty effect is investigated by three methods: statistical analysis under the assumption that the mean and variance of the underlying distributions are known, a Monte Carlo based method when the uncertain values can be bounded from below and above by known quantities, and information gap theory when only nominal values and relative weights regarding the unknown variables are given. The optimization is performed by dynamic programming. The modeling methods and the associated optimization are applied to a small tactical missile, examining and comparing the various strategies.
Modeling Micro-Scaffold-Based Implants for Bone Tissue Engineering
Authors: Holdstein Y. , Fischer A.
Published: July 2009

Metabolic bone diseases are at the forefront of scientific and biomedical research worldwide. Diseases such as osteoporosis are characterized by increased bone fragility, which leads to micro-architectural deterioration of bone tissue and eventually to micro fractures. At the micro-structural level, bone is constructed from thin rods known as trabeculae and plates. These rods and plates are arranged in semi-regular, three-dimensional patterns and constitute highly anisotropic and heterogenic material. The bone micro-structure is stochastic in nature and varies according to patient, bone type and location within a specific bone. Diagnostic abilities rely on high technology and advanced methods for 3D micro scanning, modeling and analyzing the bone micro-structure. We propose a novel method for modeling scaffold-based implants that have the stochastic structure of bone and can be customized according to given bone structures. The method for designing these implants is based on a 3D pattern synthesis technique that can be applied to the diseased cavities of a given bone. The implants will replace these cavities in the cancellous bone. Recognizing these cavities is a difficult process, since such bone is characterized by a complex micro-structure composed of thin cylindrical rods and plates. Cavities with this 3D micro-structure will be identified by measuring the volumes of those cavities and comparing them to a specified threshold. The in-filling will be based on a 3D pattern growing scheme that takes the exerted forces into account so that the global directionality of the micro-structure is preserved. Furthermore, the goal is to optimize the topology according to mechanical rules. Due to the complexity of the problem, the approach is initially examined only for 2D medical images. The main contribution of this method is that the structure of the micro-implants will not be the current standard structure (cubes with holes), which lack the characteristics of a given bone structure. Moreover, this method can be used to design and manufacture customized micro-implants according to the specific stochastic micro-structure of a given bone. These customized designed implants can be manufactured using micro-RP technology.
A Novel Evolutionary Method for Synthesis 3D Continuous Structures
Authors: Yogev Or , Shapiro Andrew A. , Antonsson Erik K.
Published: July 2009

The design of complex structures which benefit the usage of inhomogeneous properties is a very difficult task. In this paper we present a novel approach in which we synthesize the design of structures by mimicking two fundamental processes from biology — Evolution and Development. We will show that by using these two processes in a computational model, we are able to evolve high performance structures. These structures contain a high degree of complexity from a topological aspect and from a materials distribution aspect. This degree of complexity is difficult or even impossible to achieve by ordinary design methods.
Towards Automation of Manual Operations in a High School Chemistry Laboratory
Authors: Verner Igor M. , Revzin Leonid B.
Published: July 2009

This paper proposes a learning environment in which manual operations of school chemistry laboratory experiments, such as titration and aliquoting, are automated by means of computer controlled devices. The educational study focuses on characteristics of learning in the automated laboratory environment. Pilot teaching indicated that using automation devices significantly reduces the performance time of titration laboratory work. The students also noted that automated titration experiments are more simple and accurate. Therefore, automation of manual operations in laboratory practice has been found to provide a very positive learning environment.
Finite Element Analysis of Electromagnetic Effects on Hemispherical Contacts
Authors: Tecker Kelly , Green Itzhak
Published: July 2009

This work presents a three dimensional finite (3D) element analysis (FEA) of electrical contact between two non-conforming hemispheres at various vertical interferences. Items of particular interest include contact forces, current densities, and magnetic forces. The results are normalized to be applicable to micro and macro-scaled contact models. To test the validity of the analysis, the results are compared to another work focusing on contact between a hemisphere and rigid flat.
Training Teams in Managing Projects in a Matrix Structure
Authors: Davidovitch Lior , Parush Avi , Hewett Tom , Shtub Avy
Published: July 2009

Projects are performed in different kinds of organizations: functional structure, project-based structure or matrix structure. The matrix organization is a combination of the functional organization and the “pure” project organization. In a matrix organization, there are usually two chains of command. The chain dealing with issues related to the functional division and the chain dealing with issues related to the project. Due to the split authority between project managers and functional managers, management becomes much more complicated. The cooperation between the project managers is vital for the matrix organization to perform well. Therefore, training teams of project managers in the matrix structure environment is required. A new method for training teams of project managers is presented. The proposed method is based on a real-time simulation called the Project Team Builder (PTB). PTB simulates a dynamic, stochastic multi-project management environment. A project management course for graduate students in systems engineering utilized PTB. The students used the simulator in a multi-user multi-project mode. A class of undergraduate engineering students participated in the same experiment as a control group. The 132 participants were divided into teams of three students (44 teams) which performed repetitive simulation-runs. Three factors were investigated: 1. Previous experience, 2. History recording mechanism, and 3. Team debriefing process. The findings indicate that for the initial learning phase, and for the transfer to different scenario phase, these three independent factors affect the performances. Furthermore, the interactions between the experience and history factors; between the experience and debriefing factors; and between the history and debriefing factors were all significant. Based on these findings a new paradigm for simulation-based team-learning model in a matrix organization structure is presented. The new model includes integration of history mechanism and debriefing procedure in the Kolb’s Team Learning Experience model.
Physical and Psychical Conditions Decline of Older People With Age, Measured by Functional Reach Test and by Mini Mental State Examination
Authors: Costarella Marianna , Monteleone Lucilla , Steindler Roberto , Zuccaro Stefano Maria
Published: July 2009

There are several tests to value the psychophysical characteristics of older people and, among all, the most suitable to this aim are here considered the Functional Reach (FR) test, as an index of the aptitude to maintain balance in upright position, and the Mini Mental State Examination (MMSE), as a global index of cognitive abilities. The sample of older people we have analysed concerns 50 healthy subjects divided into three groups according to the age (15 from 55 to 64 years old, 19 from 65 to 74 years old, and 16 more than 75 years old); they underwent a FR test, which consists first in the measurement of the anthropometric characteristics, then in the execution of the test itself, and finally in the study of the upright posture carried out analysing the Centre of Pressure (COP) trend; they underwent as well a MMSE to value the main areas of the cognitive function concerning the space-temporal orientation, the short-term memory, the attention ability, the calculus ability and the praxis-constructive ability. The results of these tests show, according to the age, a loss both of the physical performances (FR, FR related to height, and COP displacement), and of the cognitive abilities (MMSE); however, in all cases, the only significant changes are those between the first and the other two groups of age. A comparison between the results of male and female subjects inside the three groups, although the results of the males are generally superior to the female ones, is never significant; moreover, the differences of the FR tests, in particular, are completely not significant if compared to the height of the subjects. Finally, a comparison between FR and MMSE shows a quicker decline of the physical performances with regard to the cognitive ones.
Build Sequence Scheduling to Minimize Complexity in Mixed-Model Assembly Lines
Authors: Zhu Xiaowei , Wang Hui , Hu S. Jack , Koren Yoram
Published: July 2009

Build sequence scheduling is an important topic in mixed-model production. It is to determine the order of products being built in the assembly line. Significant research has been conducted to determine good sequences based on various criteria. For example, in Just-In-Time production systems, optimal sequences are searched to minimize the variation in the rate at which different parts were consumed. This paper discusses the selection of optimal build sequences based on complexity introduced by product variety in mixed-model assembly line. The complexity was defined as the information entropy that operator processes during assembly, which indirectly measures the human performance in making choices, such as selecting parts, tools, fixtures, and assembly procedures in a multi-product, multi-stage, manual assembly environment. In an earlier paper by the authors, a simple version of complexity measure has been developed for i.i.d. (independent identically distributed) sequences. This paper extends the concept and takes into account the sequential dependence of the choices and its impact on build sequence schedules. A model based on Hidden Markov Chain is proposed to model the sequence scheduling problem with the constraints by spacing rules. Methodologies developed in this paper enhance the previous work on modeling complexity, and provide solution strategies for build sequence scheduling to minimize complexity.
Friction and Wear of MoS2 Films on Etched Steel Surfaces
Authors: Perfilyev V. , Moshkovich A. , Lutudjean K. , Rapoport L.
Published: July 2009

Surface texturing is one of modern technologies using for improvement friction and wear properties of rubbed surfaces. The simple and effective methods of surface texturing are mechanical or chemical treatments of friction surfaces. In this work we deal with chemical treatment of steel surfaces with following filling the profile by solid lubricant particles as MoS2. The steel surfaces were etched with phosphoric acid. The effect of time and temperature of etching on the surface roughness parameters was studied. Some standard roughness parameters of etched surface were measured. It was found that the parameters of roughness as Rz and Sm characterizing the depth of valleys and their size can be used for description of etched surfaces. Optimal parameters, Rz and Sm, providing the best tribological properties were determined: Rz = 5 ∼ 7 m and Sm = 50–70 m. The thickness of solid lubricant film was about 1 m. Finally, the tribological properties of MoS2 films on the steel surfaces textured by chemical treatment were performed. The friction coefficient and wear life of solid lubricant films was assessed. Friction and wear properties of MoS2 films on etched surfaces were compared with similar films on virgin steel surface. The wear life of MoS2 films on etched surfaces was 5–7 times larger than for solid lubricant film on mechanically treated steel surface.
Rapid Manufacturing Using Infiltration Selective Laser Sintering
Authors: Bourell David L. , Vallabhajosyula Phani , Stevinson Brooke , Chen Ssuwei , Beaman Joseph J.
Published: July 2009

Selective Laser Sintering (SLS) is tooless, computer-controlled layerwise additive manufacturing using a laser and a powder bed. The scanning laser locally melts the surface of a powder bed selectively, followed by deposition of a fresh layer of powder and repetition of the process. SLS has been developed for plastic powder. Creation of non-metallics and metal parts is more challenging. One approach is to mix the master powder with a transient binder. SLS melts the binder which wets the master powder, creating a green part. Subsequent post-processing is required to either remove the binder or convert it to a usable form. The last step is infiltration with a molten substance. Fundamentals of infiltration theory will be reviewed. A study of dimensional changes associated with various stages of processing reveals that overall linear dimensions vary less than one percent compared to the computer solid model. Several examples demonstrating the utility of an infiltration approach to freeform fabrication will be presented. These include silicon carbide with a phenolic binder, infiltrated with silicon; graphite with a phenolic binder infiltrated with epoxy; and tool steel with a proprietary low-ash binder infiltrated with cast iron.
Towards a Unified Product and Project Lifecycle Model (PPLM) for Systems Engineering
Authors: Perelman Valeria , Sharon Amira , Dori Dov
Published: July 2009

Developing and sustaining complex systems requires collaboration of multidisciplinary teams, coordination of processes, methods and tools, allocation of resources and utilization of adequate facilities within enterprises. The system engineering management comprises three intertwined domains: the product, the project and the enterprise. Despite the obvious links between them, each is carried out using its distinct ontology and toolset. This conceptual separation hinders effective handling of the project and product lifecycle activities within the enterprise. Testing activities of complex products are focused on verifying the performance of increasingly large modules, from software and hardware components, through subassemblies to the entire operational system. What needs to be developed, tested, and delivered is determined by the product requirements, its functions, architecture, components, and their interactions. When each component should and can be developed and tested is determined by the project plan, which is dynamically re-estimated, re-evaluated, and re-planned depending on different parameters such as the project actual status compared with the plan, recourses availability, risks, technological breakthroughs or other impacting issues. Whether carrying out the development mission is feasible is determined by the responsible enterprise, its size, structure, management criteria, other projects running in parallel, commitments, and many other aspects. This paper introduces a unified project-product lifecycle management framework that attempts to address the problems cause by separating the product from the project that is supposed to deliver it within the executing enterprise.
New Development in Computer Aided Electroforming for Rapid Prototyping Applications
Authors: Monzo´n Mario , Herna´ndez Pedro M. , Marrero Mari´a D. , Beni´tez Antonio N. , Ortega Fernando , Socas Ayoze
Published: July 2009

Electroforming enables metallic parts manufacturing with good mechanical properties and high level of accuracy and reproducibility. A thin metallic shell is deposited on a model and later released from it. There are several applications of electroforming combined with rapid prototyping: injection moulds, EDM electrodes, moulds for rotational moulding, complex metallic parts, etc. However the two main disadvantages of electroforming are the non uniform thicknesses distribution and high time of shell manufacturing. The paper focuses on a new development in order to achieve uniform thickness and otherwise a faster shell manufacturing. A new device and software have been developed, named Elecform3D™. The device is an automatic machine controlled by computer and assembled into the electroforming equipment. Otherwise the software not only controls the device but also simulates and calculates the optimal positions of the cathode based in the electrolytic parameters of the bath. The software recommends an automatic program of movements or allows the operator to decide another alternatives programs if necessary. Elecform 3D is an important step beyond electroforming so far. RP 3D printer combined with Elecform 3D is a cheaper alternative for high quality metallic parts manufacturing in comparison with SLS-SLM technologies or high speed machining, mainly for rapid tooling and even rapid manufacturing.
An Innovative Electroforming Process for Oil Heated Rotational Moulding Tools
Authors: Monzo´n Mario , Herna´ndez Pedro M. , Beni´tez Antonio N. , Marrero Mari´a D. , A´lvarez Mari´a A. , Kearns Mark
Published: July 2009

Rotational moulding is a method to produce hollow plastic articles. Heating is normally carried out by placing the mould into a hot air oven where the plastic material in the mould is heated. The most common cooling media are water and forced air. Due to the inefficient nature of conventional hot air ovens most of the energy supplied by the oven does not go to heat the plastic and as a consequence the procedure has very long cycle times. Direct oil heating is an effective alternative in order to achieve better energy efficiency and cycle times. This research work has combined this technology with new innovative design of mould, applying the advantages of electroforming and rapid prototyping. Complex cavity geometries are manufactured by electroforming from a rapid prototyping mandrel. The approach involves conformal heating and cooling channels, where the oil flows into a parallel channel to the electroformed cavity (nickel or copper). Because of this the mould enables high temperature uniformity with direct heating and cooling of the electroformed shell. Uniform heating and cooling is important not only for good quality parts but also for good uniform wall thickness distribution in the rotationally moulded part. The experimental work with the manufactured prototype mould has enabled analysis of the thermal uniformity in the cavity, under different temperatures.
A Quasi-Normal Scale Elimination Theory of Turbulent Flows With Stable Stratification
Authors: Sukoriansky Semion , Galperin Boris
Published: July 2009

The Quasi-Normal Scale Elimination (QNSE) theory is a second order spectral closure capable of dealing with host of complicated factors introduced by nonlinearity and stable stratification. The theory is based upon a mapping of the actual velocity field to a quasi-Gaussian field whose modes are governed by the Langevin equation. The parameters of the mapping are calculated using a systematic process of successive averaging over small shells of velocity and temperature modes that eliminates them from the momentum and temperature equations. Turbulence and waves are treated as one entity and the effect of waves is easily identifiable. The model shows that there exists a range of Richardson numbers, between, approximately, 0.1 and 1, in which turbulence and heat transfer undergo remarkable anisotropization; the vertical mixing becomes suppressed while the horizontal mixing is enhanced. The theory yields analytical expressions for various 1D and 3D kinetic and potential energy spectra that reflect the effects of waves and anisotropy. The model’s results are suitable for immediate use in practical applications. Partial scale elimination gives sub-grid-scale viscosities and diffusivities that can be used in large eddy simulations. The elimination of all fluctuating scales results in RANS models.
Knowledge-Based Design of Services With Application to an After-Sales Service Facility
Authors: Karni Reuven , Kaner Maya
Published: July 2009

A service is a process comprising a series of more or less intangible activities that normally, but not always, take place in interactions between the customer and service employees and/or physical resources and goods and/or systems of the service provider, and provide solutions to customer problems. We define a service concept in terms of the components of the service package and translate the concept into its constituent parts, such as persons (owners, service providers, service supporters, experts, clients, consultants), tangibles (physical products or parts, facilities, amenities, equipment, furnishings, call center), intangibles (goals, service / external / information environments, service recovery, performance, feedback), and activities (functions, processes, procedures, events) — so that it can be designed, tested, and delivered. The range and diversity of service components is organized in a five-level taxonomy for services, whose major categories encompass customers, goals, inputs, outputs, processes, human operatives, physical and technological resources, information and knowledge, and the environment. This serves as a knowledge base for design, which is carried out through an unguided or guided search down the hierarchy, progressively selecting and incorporating categories, attributes and values into the evolving service concept. The procedure is illustrated through its application to an after-sales service facility.
A Rigid Punch on an Elastic Half-Space Under the Effect of Friction: A Finite Difference Solution
Authors: Dorogoy Avraham , Banks-Sills Leslie
Published: July 2009

The accuracy of the finite difference technique in solving frictionless and frictional advancing contact problems is investigated by solving the problem of a rigid punch on an elastic halfspace subjected to normal loading. Stick and slip conditions between the elastic and the rigid materials are added to an existing numerical algorithm which was previously used for solving frictionless and frictional stationary and receding contact problems. The numerical additions are first tested by applying them in the solution of receding and stationary contact problems and comparing them to known solutions. The receding contact problem is that of an elastic slab on a rigid half-plane; the stationary contact problem is that of a flat rigid punch on an elastic half-space. In both cases the influence of friction is examined. The results are compared to those of other investigations with very good agreement observed. Once more it is verified that for both receding and stationary contact, load steps are not required for obtaining a solution if the loads are applied monotonically, whether or not there is friction. Next, an advancing contact problem of a round rigid punch on an elastic half-space subjected to normal loading, with and without the influence of friction is investigated. The results for frictionless advancing contact, which are obtained without load steps, are compared to analytical results, namely the Hertz problem; excellent agreement is observed. When friction is present, load steps and iterations for determining the contact area within each load step, are required. Hence, the existing code, in which only iterations to determine the contact zone were employed, was modified to include load steps, together with the above mentioned iterations for each load step. The effect of friction on the stress distribution and contact length is studied. It is found that when stick conditions appear in the contact zone, an increase in the friction coefficient results in an increase in the stick zone size within the contact zone. These results agree well with semianalytical results of another investigation, illustrating the accuracy and capabilities of the finite difference technique for advancing contact.
Numerical Simulation of the Drillstring-in-Hole Dynamics at Rotary Drilling
Authors: Tikhonov Vadim S. , Safronov Alexander I.
Published: July 2009

A numerical solution is suggested for the problem of drillstring buckling under the action of compressive load, torque and drillstring rotation in a hole of an arbitrary axial line. This problem is of great practical importance when assessing the pass ability and wear of drillstring. The developed 3D dynamic model of drillstring-in-hole and numerical solution of the problem provide a means to analyze stress-deformed state of the drillstring in contact with the wellbore. The model of normal contact force is based on nonlinear dependence of the contact force on the depth of interpenetration of bodies. The tangential contact is described using a model of modified Coulomb friction. The model of transition of sliding friction to rolling friction is suggested to take account of the effect of drillstring planetary motion. The set of partial differential equations is solved numerically based on the method of lines. A number of examples are presented to analyze the drillstring motion under the action of compressive load, torque and angular velocity, and other parameters.
Design Optimization of a Laser Cutting Machine by Elastodynamic Modeling
Authors: Troncossi Marco , Troiani Enrico , Rivola Alessandro
Published: July 2009

This study deals with the elastodynamic modeling of a laser cutting machine and illustrates the guidelines followed for the design optimization of the machine’s basic structure from the dynamic behavior point of view. A finite element model was set up along with the conceptual design of the new machine, with the aim of performing dynamic simulations. The main purpose is to predict the vibrations arising in the structure that could significantly deteriorate the product quality in order to evaluate different design solutions. The vibrations can be excited by variable forces acting on the moving masses and by the oscillations affecting the machine basement due to external causes. The original modeling of the excitations is presented herein. Modal analysis and forced simulations were performed on the finite element model of the first conceptual design of the machine structure. The analysis of the results indicated some critical parts of the system to be stiffened in order to mitigate the vibrations, that is to improve the cutting quality. Structural modifications to the first conceptual design were therefore suggested and a new model of the machine was developed and simulated. The results of the simulations before and after the design modifications are reported and discussed.
Optimal Linear State Feedback Time-Varying Regulator for a Unicycle Mobile Robot
Authors: Rafikova Elvira , Kurka Paulo R. G. , Rafikov Marat
Published: July 2009

This paper proposes an optimal time-varying linear state feedback control for wheeled mobile robot of the unicycle type. The control law that stabilizes exponentially the motion of the robot to a given desired trajectory is found, after transformation of the cinematic model of the robot into a well-known Brocket integrator [1]. Numerical simulations are presented in order to demonstrate the effectiveness of the proposed control design.