bluuebunny/crossref_metadata_2025 huggingface dataset:
Control System Simulators for Gas-Liquid Cylindrical Cyclone Separators
Authors: Wang Shoubo , Mohan Ram S. , Shoham Ovadia , Marrelli Jack D. , Kouba Gene E.
Published: July 2002

The control system performance of gas liquid cylindrical cyclone (GLCC©) separators can be considerably improved by adopting suitable control strategy and optimizing the design of the controller PID settings. Dynamic simulators have been developed in this study, based on Matlab/Simulink® software for evaluation of several different GLCC control philosophies for two-phase flow metering loop and bulk separation applications. Detailed analysis of the GLCC control system simulators indicates that for integrated liquid level and pressure control strategy, the level control loop compliments the operation of the pressure control loop, and vice versa. This strategy is ideal for reducing the pressure fluctuations in the GLCC. At severe slugging conditions, the integrated liquid level control is more desirable because of its faster response. However, there is no control of the GLCC pressure fluctuations. The results also show that the simulators are capable of representing the dynamic behavior of real physical systems. [S0195-0738(00)00504-5]
A Gain Scheduled Sliding Mode Control Scheme Using Filtering Techniques With Applications to Multilink Robotic Manipulators
Authors: Xu Jian-Xin , Pan Ya-Jun , Lee Tong-Heng
Published: July 2002

In this paper, a gain scheduled sliding mode control (SMC) scheme is proposed for tracking control tasks of multilink robotic manipulators. In the new scheme, filtering techniques play the key role in acquiring equivalent control signals and scheduling the switching control gain automatically. Once the system enters the sliding motion, two classes of low-pass filters are introduced to work concurrently for the purpose of acquiring equivalent control, reducing the switching gain effectively, and as a result eliminating chattering. By virtue of equivalent control theory, one class of filters is designed to capture the “average” profile of the switching quantity, which is in proportion to the desired control input. Meanwhile, another class of low-pass filters is added to scale down the gain of the switching control. The convergence property of the proposed control scheme is rigorously analyzed in time domain and the frequency domain knowledge can be easily incorporated into the construction of the two classes of filters. Excellent tracking performance is achieved with the direct manipulation of switching control input using filtering technology and with the integration of both time domain and frequency domain system knowledge in controller design. [S0022-0434(00)01604-X]
On the Modal Testing of Microstructures: Its Theoretical Approach and Experimental Setup
Authors: Chou Yuan-Fang , Wang Li-Chung
Published: July 2002

Small and lightweight structures have very high natural frequencies and small elastic displacement compared to ordinary structures. Due to limited excitation bandwidth and relatively large size of pick up devices, conventional modal testing facilities are not feasible for testing MEMS structures. A modal testing system based on the base excitation principle was developed in this research. In the meantime, the associated mathematical model for frequency response functions was derived as well. Testing structures are mounted on a rigid platform that can move essentially with only one translational degree of freedom. An electric discharge pulse strikes the platform to provide a very wide band excitation. Laser Doppler vibrometers are used to pick up both input and output signals. Since these signals are picked up without contacting structures, the structural dynamic characteristics remain intact without any distortion. With this system, modal parameters of a miniature structure can be extracted, and the receptance functions are synthesized successfully.
Dynamical Adaptive First and Second-Order Sliding Backstepping Control of Nonlinear Nontriangular Uncertain Systems
Authors: Scarratt J. C. , Zinober A. , Mills R. E. , Rios-Bolı´var Miguel , Ferrara A. , Giacomini L.
Published: July 2002

In this paper combined algorithms for the control of nontriangular nonlinear systems with unmatched uncertainties will be presented. The controllers consist of a combination of Dynamical Adaptive Backstepping (DAB) and Sliding Mode Control (SMC) of first and second order. In order to solve a tracking problem, the DAB algorithm (a generalization of the backstepping technique) makes use of virtual functions as well as tuning functions to construct a transformed system for which a regulation problem has to be solved. The new state is extended by an n−ρth order subsystem in canonical form where n is the order of the original system and ρ is the relative degree. The role of the sliding mode control is to replace the last step of the design of the control law to obtain more robustness toward disturbances and unmodeled dynamics. The main advantages of the second-order sliding mode algorithm are the prevention of chattering, higher accuracy, and a significant simplification of the control law. A comparative study of these first and second order sliding controllers will be presented. [S002-0434(00)02604]
Fatigue Fracture of the Stem–Cement Interface With a Clamped Cantilever Beam Test
Authors: Heuer D. A. , Mann K. A.
Published: July 2002

A clamped cantilever beam test was developed to determine the fatigue crack propagation rate of the CoCr alloy/PMMA cement interface at high crack tip phase angles. A combination of finite element and experimental methods was used to determine the fatigue crack growth rates of two different CoCr alloy/PMMA cement surfaces. A crack tip phase angle of 69 deg was found, indicating that loading at the crack tip was mixed-mode with a large degree of in-plane shear loading. The energy required to propagate a crack at the interface was much greater for the plasma-sprayed CoCr surface when compared to the PMMA-precoated satin finish p<0.001. Both interface surfaces could be modeled using a Paris fatigue crack growth law over crack propagation rates of 10−4 to 10−9 m/cycle.[S0148-0731(00)01306-6]
Moisture Diffusion in Epoxy Molding Compounds Filled With Particles
Authors: Uschitsky M. , Suhir E.
Published: July 2002

Mechanical reliability of epoxy molding compounds in plastic packages of integrated circuits (IC) is greatly affected by the compound ability to absorb moisture. Accordingly, the objective of the study is to evaluate the effect of moisture sorption on the mechanical properties of the compound. Experimental studies were conducted to evaluate the moisture diffusion in compounds with different, from moderate to high, concentration of silica and alumina nitride fillers. The weight-gained analysis indicated that the moisture diffusion was of non-Fickian type and depended mainly on the specimen’s relative humidity and the filler concentration. We found that although the hygro-thermal stresses, caused by moisture diffusion, were relatively low, such diffusion led to an appreciable decrease in the compound’s strength. Moisture diffusion can result also in a substantial increase in the material’s plasticity. The obtained results can be helpful in the analysis of the mechanical behavior of molding compounds employed in electronic packaging. These results can be used to better understand and to improve the reliability of plastic packages of IC devices.
A Numerical Calculation of the Contact Area and Pressure of Real Surfaces in Sliding Wear
Authors: Liu Zhiqiang , Neville Anne , Reuben R. L.
Published: July 2002

A numerical simulation technique based on elastic asperity deformation is presented to analyze real surface contact and pressure distributions in sliding wear. The calculations have been applied to experimentally produced surfaces whose topography has been determined using an atomic force microscope. A variational approach is applied to minimize the stored energy in the contact, which determines contact area without additional iteration. Two-dimensional FIR digital filter techniques are used and an FFT procedure is used to improve the efficiency of the filter implementation. The model is used to obtain the pressure distribution, real contact area, and the distribution of real contact area under sliding conditions either parallel or perpendicular to the grinding lay. The calculated results of real contact stress at different stages of wear are given. The calculated and experimental results suggest that the stress distribution of real contact follows an exponential function. The contact stress distribution index β governs the stress distribution form and reflects the performance of the frictional components in sliding wear. The proportion of plastic contact deformation ψ is also related to β; therefore, reflecting the frictional property in sliding wear. The experimental and calculated results show that the smaller frictional coefficient and more homogeneous distribution of stress occur when the sliding direction is parallel rather than perpendicular to the grinding-lay direction.
On the Interior Stress Problem for Elastic Bodies
Authors: Helsing J.
Published: July 2002

The classic Sherman-Lauricella integral equation and an integral equation due to Muskhelishvili for the interior stress problem are modified. The modified formulations differ from the classic ones in several respects: Both modifications are based on uniqueness conditions with clear physical interpretations and, more importantly, they do not require the arbitrary placement of a point inside the computational domain. Furthermore, in the modified Muskhelishvili equation the unknown quantity, which is solved for, is simply related to the stress. In Muskhelishvili’s original formulation the unknown quantity is related to the displacement. Numerical examples demonstrate the greater stability of the modified schemes. [S0021-8936(00)01304-0]
Development of Reliability and Moldability on Fine Pitch Ball Grid Array by Optimizing Materials
Authors: Aihara Takashi , Ito Shingo , Sasajima Hideaki , Oota Ken
Published: July 2002

The market for BGA packages is expanding all over the world, owing to the ease of its mounting onto the PC boards. On the other hand, BGA packages possess certain shortcomings compared to QFPs. Anti-solder crack performance on Fine Pitch BGA (=FPBGA) and warpage on Mold Array Package-BGA(=MAP-BGA) are significant disadvantages. To improve the performance of BGA packages, we studied various combinations of materials used for BGA package including molding compounds, die attach pastes, and substrates.
Development of Glass-Free Metal Electrically Conductive Thick Films
Authors: Liu Zongrong , Chung D. D. L.
Published: July 2002

Air-firable glass-free metal electrically conductive thick film pastes of different compositions were developed by using a titanium alloy component, and tin and zinc metal substitutes for glass frit used in traditional thick film pastes. The effect of different components on the electrical resistivity and bonding between the thick film and the alumina substrate was investigated. Thick films with low electrical resistivity and good bonding to the alumina substrate were obtained by using silver, zinc, tin, and TiCu alloy powders in the pastes. The addition of zinc at a small proportion (<0.5 wt.%) to a thick film paste enhanced the adhesion between the thick film and the alumina substrate with negligible increase in the electrical resistivity. The use of titanium alloy powder instead of pure titanium powder is preferred. Better composition distribution, and consequently, better wetting and bonding are expected by using active metal particles of a smaller size.
Augmentation of Stagnation Region Heat Transfer Due to Turbulence From a DLN Can Combustor
Authors: Van Fossen G. James , Bunker Ronald S.
Published: July 2002

Heat transfer measurements have been made in the stagnation region of a flat plate with a circular leading edge. Electrically heated aluminum strips placed symmetrically about the leading edge stagnation region were used to measure spanwise-averaged heat transfer coefficients. The maximum Reynolds number obtained, based on leading edge diameter, was about 100,000. The model was immersed in the flow field downstream of an approximately half-scale model of a can-type combustor from a low NOx, ground-based power-generating turbine. The tests were conducted with room temperature air; no fuel was added. Room air flowed into the combustor through six vane-type fuel/air swirlers. The combustor can contained no dilution holes. The fuel/air swirlers all swirled the incoming airflow in a counterclockwise direction (facing downstream). A five-hole probe flow field survey in the plane of the model stagnation point showed the flow was one big vortex with flow angles up to 36 deg at the outer edges of the rectangular test section. Hot-wire measurements showed test section flow had very high levels of turbulence, around 28.5 percent, and had a relatively large axial-length scale-to-leading edge diameter ratio of 0.5. X-wire measurements showed the turbulence to be nearly isotropic. Stagnation heat transfer augmentation over laminar levels was around 77 percent and was about 14 percent higher than predicted by a previously developed correlation for isotropic grid-generated turbulence.
Correcting Inflow Measurements From Wind Turbines Using a Lifting-Surface Code
Authors: Whale J. , Fisichella C. J. , Selig M. S.
Published: July 2002

In order to provide accurate blade element data for wind turbine design codes, measured three-dimensional (3D) field data must be corrected in terms of the (sectional) angle of attack. A 3D Lifting-Surface Inflow Correction Method (LSIM) has been developed with the aid of a vortex-panel code in order to calculate the relationship between measured local flow angle and angle of attack. The results show the advantages of using the 3D LSIM correction over 2D correction methods, particularly at the inboard sections of the blade where the local flow is affected by post-stall effects and the influence of the blade root. [S0199-6231(00)00604-3]
On the Kinematic Error in Harmonic Drive Gears
Authors: Ghorbel Fathi H. , Gandhi Prasanna S. , Alpeter Friedhelm
Published: July 2002

Harmonic drive gears are widely used in space applications, robotics, and precision positioning systems because of their attractive attributes including near-zero backlash, high speed reduction ratio, compact size, and small weight. On the other hand, they possess an inherent periodic positioning error known as kinematic error responsible for transmission performance degradation. No definite understanding of the mechanism of kinematic error as well as its characterization is available in the literature. In this paper, we report analytical and experimental results on kinematic error using a dedicated research Harmonic Drive Test Apparatus. We first show that the error referred to in the literature as kinematic error actually consists of a basic component, representing “pure” kinematic error, colored with a second component resulting from inherent torsional flexibility in the harmonic drive gear. The latter component explains the source of variability in published kinematic error profiles. The decomposition of the kinematic error into a basic component and a flexibility related component is demonstrated experimentally as well as analytically by matching a mathematical model to experimental data. We also characterize the dependence of the kinematic error on inertial load, gear assembly, and rotational speed. The results of this paper offer a new perspective in the understanding of the mechanism of kinematic error and will be valuable in the mechanical design of harmonic drive gears as well as in the dynamic modeling and precision control of harmonic drive systems.
Waveform Dependence of Pulsatile Flow in a Stenosed Channel
Authors: Liu H. , Yamaguchi T.
Published: July 2002

Blood flow in arteries often shows a rich variety of vortical flows, which are dominated by the complex geometry of blood vessels, the dynamic pulsation of blood flow, and the complicated boundary conditions. With a two-dimensional model of unsteady flow in a stenosed channel, the pulsatile influence on such vortical fluid dynamics has been numerically studied in terms of waveform dependence on physiological pulsation. Results are presented for unsteady flows downstream of the stenosed portion with variation in the waveforms of systole and diastole. Overall, a train of propagating vortex waves is observed for all the cases, but it shows great sensitivity to the waveforms. The generation and development of the vortex waves may be linked to the presence of an adverse pressure gradient within a specific interval between two points of inflection of the systolic waveform. The adverse pressure gradient consists of a global pressure gradient that is found to be closely related to the dynamics of the pulsation, and a local pressure gradient, which is observed to be dominated by the nonlinear vortex dynamics.
Iterative Learning Control for Nonlinear Nonminimum Phase Plants1
Authors: Ghosh Jayati , Paden Brad
Published: July 2002

Learning control is a very effective approach for tracking control in processes occurring repetitively over a fixed interval of time. In this paper a robust learning algorithm is proposed for a generic family of nonlinear, nonminimum phase plants with disturbances and initialization error. The “stable-inversion” method of Devasia, Chen and Paden is applied to develop a learning controller for linear nonminimum phase plants. This is adapted to accommodate a more general class of nonlinear plants. The bounds on the asymptotic error for the learned input are exhibited via a concise proof. Simulation studies demonstrate that in the absence of input disturbances, perfect tracking of the desired trajectory is achieved for nonlinear nonminimum phase plants. Further, in the presence of random disturbances, the tracking error converges to a neighborhood of zero. A bound on the tracking error is derived which is a continuous function of the bound on the disturbance. It is also observed that perfect tracking of the desired trajectory is achieved if the input disturbance is the same at every iteration.
A Finite-Element-Based Method to Determine the Spatial Stiffness Properties of a Notch Hinge
Authors: Zhang Shilong , Fasse Ernest D.
Published: July 2002

Notch hinges are flexural hinges used to make complex, precise mechanisms. They are typically modeled as single degree-of-freedom hinges with an associated joint stiffness. This is not adequate for all purposes. This paper computes the six degree-of-freedom stiffness properties of notch hinges using finite element methods. The results are parameterized in terms of meaningful design parameters.
Periodic, Multi-Step Tracking Control for a Weather Satellite Scanning Mirror1
Authors: Broberg Hal , Lin Paul , Predina Joe
Published: July 2002

Weather satellite scan mirror performance often demands high pointing accuracy, rapid reposition times, and low peak power consumption. This work addresses and compares various techniques for optimizing these specific performances when the scan pattern is repetitive. We find that a technique combining open and closed-loop control in a timed sequence can often lead to the lowest pointing error in the shortest time interval while minimizing peak power. The technique applies equally well to applications such as robotics, automated manufacturing or any other electromechanical control system where quick, accurate response is needed while minimizing peak power.
Robotic Surface Finishing Processes: Modeling, Control, and Experiments
Authors: Pagilla Prabhakar R. , Yu Biao
Published: July 2002

Control of robotic surface finishing processes such as deburring, grinding, chamfering, and polishing is considered in this paper. A complete dynamic model that describes the dynamic behavior of the robot for surface finishing tasks is developed. A complete surface finishing task is divided into three phases (free motion phase, transition phase, and constrained motion phase) depending on the location of the robot end-effector with respect to the constraint surface. Stable control algorithms are developed for each phase. Emphasis is given to the transition phase and constrained motion phase, where surface finishing takes place. An experimental platform for performing robotic surface finishing operations is developed. The robotic surface finishing system consists of a planar robot with a force sensor and a deburring tool on its end-effector, and a fixture to hold the constraint surface. Extensive experiments based on the proposed control design were conducted for both surface following and surface finishing. Results of surface following and surface finishing experiments are shown and discussed.
Effect of Constant Heat Flux Boundary Condition on Wall Temperature Fluctuations
Authors: Mosyak A. , Pogrebnyak E. , Hetsroni G.
Published: July 2002

An experimental study of the wall temperature fluctuations under different thermal-wall boundary conditions was carried out. Statistics obtained from the experiments are compared with existing experimental and numerical data. The wall temperature fields are also examined in terms of the coherent thermal structures. In addition the effect of the thermal entrance region on the wall temperature distribution is also studied. For water flow in a flume and in a rectangular channel, the mean spacing of the thermal streaks does not depend on the thermal entrance length and on the type of thermal-wall boundary conditions. The wall temperature fluctuations depend strongly on the type of wall thermal boundary conditions. Overall, the picture that emerges from this investigation confirms the hypothesis that moderate-Prandtl-number heat transfer at a solid wall is governed by the large-scale coherent flow structures.
A Numerical Study of Flow and Heat Transfer in a Smooth and Ribbed U-Duct With and Without Rotation
Authors: Lin Y.-L. , Shih T. I.-P. , Stephens M. A. , Chyu M. K.
Published: July 2002

Computations were performed to study the three-dimensional flow and heat transfer in a U-shaped duct of square cross section under rotating and non-rotating conditions. The parameters investigated were two rotation numbers (0, 0.24) and smooth versus ribbed walls at a Reynolds number of 25,000, a density ratio of 0.13, and an inlet Mach number of 0.05. Results are presented for streamlines, velocity vector fields, and contours of Mach number, pressure, temperature, and Nusselt numbers. These results show how fluid flow in a U-duct evolves from a unidirectional one to one with convoluted secondary flows because of Coriolis force, centrifugal buoyancy, staggered inclined ribs, and a 180 deg bend. These results also show how the nature of the fluid flow affects surface heat transfer. The computations are based on the ensemble-averaged conservation equations of mass, momentum (compressible Navier-Stokes), and energy closed by the low Reynolds number SST turbulence model. Solutions were generated by a cell-centered finite-volume method that uses second-order flux-difference splitting and a diagonalized alternating-direction implicit scheme with local time stepping and V-cycle multigrid.
Integrated Switching and Feedback Control for Mold Filling in Resin Transfer Molding
Authors: Barooah Prabir , Berker Berna , Sun J. Q.
Published: July 2002

Two recent advances in controlling flow progression in RTM are the sequential logic control and the optimal feedback control. Both methods have powerful features as well as limitations. However, they complement each other very well. In this paper we propose an integrated control scheme combining both of them. In this paper the theory of the sequential logic control and the optimal control for flow progression manipulation in RTM is reviewed first. An integrated control approach is then proposed. Simulation results show that the control authority of the system is considerably expanded by the combination of the two. The integrated switching and feedback controller gives excellent performance of mold filling even in the presence of wide variations of the preform properties.
Modeling and Detection of Localized Tooth Defects in Geared Systems
Authors: El Badaoui M. , Cahouet V. , Guillet F. , Danie`re J. , Velex P.
Published: July 2002

The early detection of failures in geared systems is an important industrial problem which has still to be addressed from both an experimental and theoretical viewpoint. The proposed paper combines some extensive numerical simulations of a single stage geared unit with localized tooth faults and the use of several detection techniques whose performances are compared and critically assessed. A model aimed at simulating the contributions of local tooth defects such as spalling to the gear dynamic behavior is set up. The pinion and the gear of a pair are assimilated to two rigid cylinders with all six degrees of freedom connected by a series of springs which represent gear body and gear tooth compliances on the base plane. Classical shaft finite elements including torsional, flexural and axial displacements can be superimposed to the gear element together with some lumped stiffnesses, masses, inertias, … which account for the load machines, bearings and couplings. Tooth defects are modeled by a distribution of normal deviations over a zone which can be located anywhere on the active tooth flanks. Among the numerous available signal processing techniques used in vibration monitoring, cepstrum analysis is sensitive, reliable and it can be adapted to complex geared system with several meshes. From an analytical analysis of the equations of motion, two complementary detection techniques based upon acceleration power cepstrum are proposed. The equations of motion and the contact problem between mating flanks are simultaneously solved by coupling an implicit time-step integration scheme and a unilateral normal contact algorithm. The results of the numerical simulations are used as a data base for the proposed detection techniques. The combined influence of the defect location, depth and extent is analyzed for two examples of spur and helical gears with various profile modifications and the effectiveness of the two complementary detection methods is discussed before some conclusions are drawn.
Optimal Path Planning for Helical Gear Profile Inspection with Point Laser Triangulation Probes
Authors: Smith Kevin B. , Zheng Yuan F.
Published: July 2002

New commercial Point Laser Triangulation (PLT) probes enable Coordinate Measuring Machines (CMMs) to take faster, noncontact, accurate measurements. In this paper, we address how to apply this technology to inspect helical gears. Traditionally, gears are inspected with slow, costly, and dedicated machines. The proposed flexible inspection system with a fast measuring probe can significantly reduce capital equipment costs and inspection times. Integrating PLT probes on CMMs has been limited partly because of the difficulty in generating optimal inspection paths, and partly because of the highly reflective gear surfaces. Complex sensor-to-surface orientation and obstacle-avoidance requirements of these unique probes are the main cause of the difficulty. This paper presents a geometrical approach for obtaining an optimal path plan for helical gear profile inspection with PLT probes. Models for the orientation parameters and the allowable operating regions for the PLT probe are developed. A collision avoidance strategy is also presented. Although this new method was developed and demonstrated while creating an optimal path plan for inspecting helical gears, the developed models and principles can also be applied to optimal inspection plan generation for other parts.
On the Mechanical Threshold Stress of Aluminum: Effect of the Alloying Content
Authors: Puchi-Cabrera Eli S. , Villalobos-Gutie´rrez Crisanto , Castro-Farin˜as Gonzalo
Published: July 2002

The mechanical behavior of aluminum with different alloying contents up to 1 wt percent, deformed under hot-working conditions, has been analyzed in terms of the exponential saturation equation proposed by Voce for the description of the evolution of the mechanical threshold stress, σ^, and the model advanced by Kocks for the description of the ratio, sε˙,T, between the flow stress at any strain rate and temperature and σ^. It has been determined that the increase in the alloying content of aluminum gives rise to an increase in the mechanical threshold stress mainly due to the effect of the solute content on the saturation stress, σ^s and less markedly on the athermal stress, σ^a. On the contrary, it has been found that the increase in the alloying content gives rise to a decrease of the Stage II or athermal work-hardening rate, θ0. Also, it has been concluded that the increase in the solute content of the material gives rise to a significant increase in the parameters ε˙K and g0 that enter into the expression of sε˙,T. Therefore, the dependence of the flow stress at any temperature and strain rate with the alloying content evolves from the dependence of both sε˙,T and σ^ on solute concentration. Also, it has been found that, for the present analysis, the factor sε˙,T derived from Kocks model is more satisfactory than that derived from the Follansbee and Kocks model since the latter predicts negative values of the flow stress below approximately 10 MPa, that is to say, under conditions of elevated deformation temperatures and low strain rates.
New Iterative Scheme in Computer Simulation of Positive Displacement Compressors Considering the Effect of Gas Pulsations
Authors: Zhou W. , Kim J. , Soedel W.
Published: July 2002

In a typical computer simulation of positive displacement compressors, the mathematical equations that model the compressor process are integrated in the time domain starting from a set of assumed initial conditions. The simulation has to be continued for enough iterations for the results to converge. The pulsation pressures in the suction and discharge cavities, which are assumed constant in the beginning, are calculated at the end of each iteration and used for the calculation in the next iteration. However, when this scheme is actually applied to fractional horsepower reciprocating compressors, it is found that the suction cavity pressure does not converge well, while all other parts of the results converge relatively quickly. The cause of this problem is explained qualitatively by the characteristics of the simulation method. A unique iteration scheme for the simulation was developed in this work to overcome this problem. In the new scheme, the updating rate of the pulsation pressures is adjusted based on the convergence trend of the previous iterations. A practical example is used to demonstrate the convergence of the simulation results and practicality of the simulation program.
A Neuro-Fuzzy System for Tool Condition Monitoring in Metal Cutting
Authors: Mesina Omez S. , Langari Reza
Published: July 2002

A neuro-fuzzy system is used to predict the condition of the tool in a milling process. Specifically the relationship between the sensor readings and tool wear state is first captured via a neural network and is subsequently reflected in linguistic form in terms of a fuzzy logic based diagnostic algorithm. In this approach, the neural network serves as an interpolative mechanism for the generation of data that is consistent with the behavior of the process, whereas fuzzy logic provides a transparent view of the relationship between the measured variables and the tool wear state. The methodology used in this paper incorporates an error-based, density-driven adaptation scheme in conjunction with a neural network based reference model to adapt the fuzzy membership functions associated with the tool condition monitoring algorithm to ensure that the rule set reflects the true nature of the inter-relationship between the sensor readings and the tool condition. Experimental results show that the proposed fuzzy mechanism correctly predicts the condition of the tool in 97 percent of the cases where it is applied.
Design of a Lyapunov Controller for an Electro-hydraulic Actuator During Contact Tasks
Authors: Niksefat Navid , Wu Christine Q. , Sepehri Nariman
Published: July 2002

In this paper, an algorithm is developed for contact task control of electro-hydraulic actuators. The goal is to design and experimentally evaluate a robust controller that allows a hydraulic actuator to follow a free space trajectory and then make and maintain contact with the environment for exerting a desired force. First, the dynamic model of a hydraulic actuator interacting with an environment is described. Then, a Lyapunov-based controller is designed, which regulates the actuator’s position and upon contact with the environment switches to a force controller. Extended Lyapunov’s second method is used for stability analysis of the developed control system, which consists of nonsmooth dynamics. The stability of the system is guaranteed by using a smooth Lyapunov function under the condition of existence and uniqueness of Filippov’s solution. The efficacy of the proposed nonlinear controller is verified via experiments. The experiments are performed on an industrial hydraulic actuator equipped with a servovalve and include motion through free space, contact with the environment and the transition between the two.
Learning Input Shaping Technique for Non-LTI Systems
Authors: Park Juyi , Chang Pyung-Hun
Published: July 2002

It is well known that conventional Input Shaping Technique (IST) is not very effective in suppressing residual vibrations for non-LTI systems, such as substantially nonlinear or time-varying systems. In an effort to increase the effectiveness such systems, this paper presents Learning Input Shaping Technique (LIST) which iteratively updates the parameters of IST from previous trials. Simulations are presented for four different cases: (1) when the natural frequency or damping of a system is not estimated well; (2) when a system has time varying vibration; (3) when a system has nonlinear flexibility; and (4) when a closed-loop system includes a saturation element in the loop. LIST is experimented on a six D.O.F industrial robot to evaluate its effectiveness. The results of the simulations and the experiment show that the residual vibrations become considerably smaller as iteration goes on, thereby demonstrating the effectiveness of LIST.
Multiple Simultaneous Specification (MSS) Control of a High-Speed Linear Positioning System Driven by a Brushless D. C. Motor
Authors: Cho David M. K. , Ng W. T. , Mills James K.
Published: July 2002

This paper addresses the design of closed-loop controllers, which simultaneously satisfy multiple conflicting performance specifications, to Brushless DC (BLDC) motors. In this paper, a linear stage, driven with a BLDC motor directly coupled to a lead screw, is modelled with a linear second-order linear dynamic system. The limitations of the linear model are discussed. A controller is designed to simultaneously satisfy three conflicting performance specifications. The robustness of the controller to parameter uncertainty is investigated. Experimental results demonstrate the validity of the proposed approach. A design example is carried throughout the paper, to illustrate the work.
Exponential Stabilization of a Transversely Vibrating Beam by Boundary Control Via Lyapunov’s Direct Method
Authors: Fard Mehrdad P. , Sagatun Svein I.
Published: July 2002

This paper discusses the boundary stabilization of a beam in free transverse vibration. The dynamics of the beam is presented by a nonlinear partial differential equation (PDE). Based on this model a nonlinear control law is constructed to stabilize the system. The control law is a nonlinear function of the slopes and velocity at the boundary of the beam. The novelty of this article is that it has been possible to exponentially stabilize a free transversely vibrating beam via boundary control without restoring to truncation of the model. This result is achieved while the coupling between longitudinal and transversal displacements has been taken into account.
Fully Coupled Rigid Internal Combustion Engine Dynamics and Vibration—Part I: Model Development
Authors: Hoffman D. M. W. , Dowling D. R.
Published: July 2002

Robust predictions of engine vibration are important for preliminary design of new engines and new vehicles, and in setting component tolerances. Vibration modeling of internal combustion engines is commonly based on a one-way-coupling assumption between the engine’s moving internal components and the vibrating engine block. This assumption causes Coriolis and gyroscopic interactions to be neglected, and leads to a vibration model that does not properly conserve energy. This paper presents a new seven-degree-of-freedom model for low frequency engine vibrations that does not utilize the one-way-coupling assumption. The model is based on fully coupled rigid-body dynamics for the pistons, connecting rods, crankshaft, flywheel, and engine block. Predictions from the new model are compared to those from an equivalent one-way-coupled model for poorly balanced (one-cylinder) and well-balanced (inline six-cylinder) engines. Predicted mount forces are dissimilar for the poorly balanced engine but are nearly the same for the well-balanced engine. In addition, the new model is found to properly conserve energy and account for gravitational forces.
Fatigue Crack Growth Behavior of Titanium Alloy Ti-6Al-4V and Weldment
Authors: Salama Mamdouh M.
Published: July 2002

Optimization of weight, cost, and performance of deepwater offshore structures demands the increased utilization of high strength, light weight, and corrosion resistant materials such as titanium alloys. Titanium alloy Ti-6Al-4V has been considered for several critical components such as risers and taper joints. Because of the novelty of use of titanium alloys in the offshore industry, there is currently no standard governing design of titanium components for offshore structures. Since these structural components are subjected to a complex spectrum of environmental loading, assessment of defect tolerance using fatigue crack growth analysis is generally considered an important design parameter. In this paper, more than 60 crack growth data sets from 20 independent laboratories were collected and analyzed to develop crack growth rate equations for use in defect assessment. These data include the results of fatigue testing of both base material and welded joints in air and seawater with and without cathodic protection and at different R-ratios and test frequencies. The results suggest that for crack growth rates above 10−7 in./cycle, crack growth of Ti-6Al-4V appears to be independent of testing condition and materials processing. At the low crack growth rate (below 10−7 in./cycle), the review revealed that data are very limited. These limited data, however, suggest that the crack growth threshold is dependent on the R-ratio and slightly dependent on material processing. Comparison between crack growth rates of steel and titanium alloy (Ti-6Al-4V) showed that the two materials have very similar behavior.
Applying Anand Model to Represent the Viscoplastic Deformation Behavior of Solder Alloys
Authors: Wang G. Z. , Cheng Z. N. , Becker K. , Wilde J.
Published: July 2002

A unified viscoplastic constitutive law, the Anand model, was applied to represent the inelastic deformation behavior for solders used in electronic packaging. The material parameters of the constitutive relations for 62Sn36Pb2Ag, 60Sn40Pb, 96.5Sn3.5Ag, and 97.5Pb2.5Sn solders were determined from separated constitutive relations and experimental results. The achieved unified Anand model for solders were tested for constant strain rate testing, steady-state plastic flow and stress/strain responses under cyclic loading. It is concluded that the Anand model can be applied for representing the inelastic deformation behavior of solders at high homologous temperature and can be recommended for finite element simulation of the stress/strain responses of solder joints in service.
Using Porous Fins for Heat Transfer Enhancement
Authors: Kiwan S. , Al-Nimr M. A.
Published: July 2002

This work introduces a novel method that enhances the heat transfer from a given surface by using porous fins. The thermal performance of porous fins is estimated and compared with that of the conventional solid fins. It is found that using porous fin of porosity ε may enhance the performance of an equal size conventional solid fin and, as a result, save 100 ε percent of the fin material. The effect of different design and operating parameters on the porous fin thermal performance is investigated. Examples of these parameters are Ra number, Da number, and thermal conductivity ratio. It is found that more enhancement in the porous fin performance may be achieved as Ra increases especially at large Da numbers. Also, it is found that there is an optimum limit for the thermal conductivity ratio beyond which there is no further improvement in the fin performance.
The Effect of Grinding Machine Stiffness on Surface Integrity of Silicon Nitride
Authors: Yang Fulun , Zhang Bi , Wang Jiexin , Zhu Zhenqi , Monahan Richard
Published: July 2002

A theoretical model based on mechanics and machine dynamics is presented to describe the effect of machine stiffness on surface integrity of ground silicon nitride. The model accounts for both the static and dynamic structural loop stiffnesses of a precision-grinding machine. Experimental results are also presented to verify the model. A unique workholder with an adjustable compliance is used to achieve a structural loop stiffness in the range of 5–40 N/μm. Silicon nitride is ground with cup-type diamond wheels of vitrified and cast iron fiber bonds. To effectively stabilize the cutting performance of a cast iron fiber bond wheel, the ELID technique is adopted for in-process dressing. The damage depth of ground workpieces is assessed against machine stiffness. The modeling and experimental results demonstrate that there exists a critical machine stiffness in grinding of ceramics. When machine stiffness is higher than the critical stiffness, no chatter should occur in the grinding process. In this case, damage depth increases with the increase of set depth of cut. In contrast, if machine stiffness is lower than the critical stiffness, chatter can occur in the grinding process that may induce grinding damage. The model can also be used to predict the critical machine stiffness for other types of structural ceramics.
Chatter Stability Analysis of the Variable Speed Face-Milling Process
Authors: Sastry, Sridhar , Kapoor, Shiv G. , DeVor, and Richard E. , Dullerud Geir E.
Published: July 2002

In this study, a solution technique based on a discrete time approach is presented to the stability problem for the variable spindle speed face-milling process. The process dynamics are described by a set of differential-difference equations with time varying periodic coefficients and time delay. A finite difference scheme is used to discretize the system and model it as a linear time varying (LTV) system with multiple time delays. By considering all the states over one period of speed variation, the infinite dimensional periodic time-varying discrete system is converted to a finite dimensional time-varying discrete system. The eigenvalues of the state transition matrix of this finite dimensional system are then used to propose criteria for exponential stability. Predicted stability boundaries are compared with lobes generated by numerical time-domain simulations and experiments performed on an industrial grade variable speed face-milling testbed.
Effectiveness of Haptic Sensation for the Evaluation of Virtual Prototypes
Authors: Volkov Sergei , Vance Judy M.
Published: July 2002

Virtual reality techniques provide a unique new way to interact with three-dimensional digital objects. Virtual prototyping refers to the use of virtual reality to obtain evaluations of designs while they are still in digital form before physical prototypes are built. While the state-of-the-art in virtual reality relies mainly on the use of stereo viewing and auditory feedback, commercial haptic devices have recently become available that can be integrated into the virtual environment to provide force feedback to the user. This paper outlines a study that was performed to determine whether the addition of force feedback to the virtual prototyping task improved the ability of the participants to make design decisions. Seventy-six people participated in the study. The specific task involved comparing the location and movement of two virtual parking brakes located in the virtual cockpit of an automobile. The results indicate that the addition of force feedback to the virtual environment did not increase the accuracy of the participants’ answers, but it did allow them to complete the task in a shorter time. This paper describes the purpose, methods, and results of the study.
Multiple-Sensor Planning and Information Integration for Automatic Coordinate Metrology
Authors: Shen Tzung-Sz , Huang Jianbing , Menq Chia-Hsiang
Published: July 2002

Multiple-sensor integration of vision and touch probe sensors has been shown to be a feasible approach for rapid and high-precision coordinate acquisition [Shen, T. S., Huang, J., and Meng, C. H., 2000, “Multiple-sensor integration for rapid and high-precision coordinate metrology,” IEEE/ASME Trans. Mechatron. 5, pp. 110–121]. However, the automation of coordinate measurements is still hindered by unknown surface areas that cannot be digitized using the vision system due to occlusions. It is identified that the estimation and reasoning of unknown surface areas, and automatic sensor planning using multiple sensors are two key issues. In order to advance multiple-sensor integration technologies toward a fully automatic and agile coordinate metrology, information integration algorithms for estimating and reasoning unknown surface areas, and an automatic multiple-sensor planning environment are developed in this paper. Experimental and simulation results are also demonstrated.
Lapping Control of Hard Disk Drive Heads
Authors: Mei Youping , Stelson Kim A.
Published: July 2002

Bar lapping is a key process in fabricating computer hard disk drive heads. The purpose is to remove a small amount of material so that the transducer stripe height variation across the bar is minimized. In this article a method of simulating the material removal process is established. The Preston model is identified to be a reasonable constitutive relationship relating lapping rate to pressure and relative velocity. A pressure estimation method is established based on the modified beam on elastic foundation model (MBOEF) to incorporate the effect of surface shape. Simulation is conducted based on the proposed constitutive relationship and MBOEF. Results show good agreement with production observations. Hence the simulation model is used as a tool for identifying the structure of the lapping control model. The pressure dynamics of bar lapping is then identified. The process model is constructed based on the pressure dynamics and the Preston model. A controller is then designed using a trajectory following formulation. Simulation of the controller shows that it is robust to parameter uncertainties. This controller is implemented on a Seagate lapping system. Experiment results show that the proposed method is less sensitive than the existing method to the quality of the bar preparation processes prior to lapping. However, the gains should be appropriately adjusted for optimal performance. With good preparation processes and appropriate gains, performance of the proposed and existing methods are statistically comparable. Otherwise, the proposed method performs better. The proposed method is inferior to the existing method only when its gains are improperly adjusted.