bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Analysis of a Haptic Interface Design for Endosurgery
Authors: Faraz Ali , Payandeh Shahram , Salvarinov Andon
Published: January 2022

In Endosurgery, tissue manipulation is performed by long graspers which have poor force-reflection property, i.e. they do not reflect the grasping force to the hand of the surgeon. In this paper, a novel design of electro-mechanical system is considered which can enhance the force-reflecting capability of endosurgical graspers. The type synthesis of such a haptic interface have led to the application of tunable spring. The design of tunable spring is optimized based on the haptic and surgical requirements. Moreover, by using suitable control laws, it is shown that the primary requirements of the design application can be met. Simulation and experimental results are presented using a prototype model of such haptic interface[6] to demonstrate the practicality of such design concept.
Recent Progress in Mixed Objective Control Synthesis With ℓ1 and ℋ2 Norms
Authors: Salapaka Murti V. , Khammash Mustafa , Dahleh Mohammed
Published: January 2022

In this paper recent progress in the design of controllers that meet multiple criteria is reviewed. It is well-known that optimization with respect to a single measure may compromise other important closed-loop properties. The ℋ2 norm has been successfully used to design controllers with good nominal performance, and ℓ1 has been very effective in addressing time-domain and robustness requirements. Therefore, the ℋ2/ℓ1 robust synthesis problem combines the features of these two norms and can be very effective as a design tool. In this paper we survey the different approaches to this problem. A new efficient solution method for designing optimal ℋ2/ℓ1 controllers is presented. Also the status of the robust performance problem in this setting is given.
Robust Performance Repetitive Control Design Using Structured Singular Values and its Implementation
Authors: Li Jianwu , Tsao Tsu-Chin
Published: January 2022

This paper converts the design of robust repetitive controller into a standard problem. In order to handle the large delay in the internal model structure of repetitive controller, a new framework, which utilizes Structured Singular Values method (μ synthesis) for solution, is proposed. It is shown that the μ value of the new framework is a tight upper bound of the μ value of the standard problem. Under this framework, the conditions of robust stability and robust performance can be incorporated and analyzed. The designed repetitive controller preserves a special low-order filter structure for efficient real-time implementation. The robust performance can be achieved not only to the periodic signals of the fundamental frequency and its harmonics as the existing repetitive controller did, but also to asynchronous periodic and non-periodic signals by choosing appropriate performance weighting function. The design procedure is more systematic and less conservative than conventional methods. A robust repetitive controller designed using this method is implemented on a hydraulic servo for noncircular cutting. Experimental results are presented to illustrate the control system synthesis procedure and performance.
Discrete Variable Structure Control for Linear Multivariable Systems: The Output Feedback Case
Authors: Tang Choon Yik , Misawa Eduardo A.
Published: January 2022

This paper presents an observer-based discrete variable structure controller for linear multivariable systems with unmatched additive uncertainties, an extension of the results reported in [12] to the output feedback case. It is shown that the incorporation of a prediction observer with uncertainty estimation into the controller guarantees the attractiveness and invariance of the estimated boundary layer, which is dynamic and parallel to the sliding hyperplane, after a transient. As in the state feedback case1, linear control design strategies are applicable to the tracking error dynamics design inside the estimated boundary layer under an eigenvalue constraint. A numerical example is used to illustrate the proposed technique.
Reconfigurable Software for Servo-Controlled Motion
Authors: Birla Sushil K. , Shin Kang G.
Published: January 2022

The motivation for this research is to reduce the cost of servo-motion control software through efficient reuse, adaptation, and integration of generic components across a variety of applications, subject to a variety of reconfigurations over their useful life, e.g., reconfigurable manufacturing systems for machining automotive powertrain components. Future configurations (changes and add-ons) cannot always be identified and designed into the initial configuration, and hence the system design and architecture must have flexibility and adaptability in anticipation. This experimental research explores the application of two well-known paradigms in computer science, object-orientation and finite state machines, in a domain-specific software architecture, to understand the effectiveness of the software engineering approach. The software approach was applied to a laboratory testbed machine tool consisting of multiple servo-controlled axes of motion, with focus on investigating software issues in controlling individual axes.
An Analytical Stability Solution for the Turning Process With Depth-Direction Dynamics and Corner-Radiused Tooling
Authors: Ozdoganlar O. Burak , Endres William J.
Published: January 2022

An analytical stability solution is developed for the turning process. The solution allows the dominant structural vibration mode to be misaligned relative to the feed direction. It also accounts for the effects of corner radius and lead angle on the chip area to which the process force is proportionally modeled. A general form of the chip area is derived to include overlap factors for each of the feed and depth directions. Mapping the feed and depth directions into the single vibration mode of interest yields the usual form of the equation of motion having a single overlap factor and process gain. The final solution for limiting depth of cut is, unlike past solutions, an explicit function of feed rate, corner radius, lead angle and mode orientation. The analytical solution is validated through comparison to numerical simulation and then exercised to clearly demonstrate the important influence of these four parameters, the presence of which are characteristic of most real turning processes.
Optimal Control of FES Assisted Standing-up in Paraplegia Using Genetic Algorithms
Authors: Davoodi Rahman , Andrews Brian J.
Published: January 2022

A genetic algorithm (GA) optimization method was used to automate the task of tuning the controller parameters in FES assisted standing-up in paraplegia. The method can be applied to any controller with adjustable parameters but we used it to design fuzzy logic (FL) and gain scheduling PID controllers of the knee and hip joint muscles during sit-to stand motion. The genetic algorithm designed controllers, GA-FL and GA-PID were found effective in coordinating volitional and FES control according to formulated criteria. The latter was based on the deviations from the desired trajectory of the knee and hip joints and the magnitude of the voluntary arm forces. The new controllers had improved performance and safety over the standard PID control and the open-loop control commonly practiced in FES clinics.
Neural Network Model of the Voluntary Arm Forces During FES Assisted Standing-up in Paraplegia
Authors: Davoodi Rahman , Andrews Brian J. , Kamnik Roman , Bajd Tadej
Published: January 2022

To gain insight into the way paraplegic subjects voluntarily control their arms during the FES assisted standing-up, we developed a neural network model to predict the arm forces.

The training data were collected from eight paraplegic subjects during the FES-assisted standing-up and divided into two categories for training and validation. In all the cases, it was possible to develop models that followed closely the observed behavior of the subjects. The test on validation data showed that the models could generalize well to the unseen situations. It also proved that each subject has developed a unique voluntary control strategy, which is consistent. The subjects with more experience in the use of FES were more consistent in the use of their arms from trial to trial when compared to older, heavier or high lesion subjects. Comparison of the models in different subjects showed that in addition to the unique features adopted by each subject, there are also general rules that are common in the control strategies adopted by all the subjects.
Measuring Deflection Rate With an Array of Strain Sensors
Authors: Sumali Hartono
Published: January 2022

This paper presents a simple measurement technique for measuring the translational and rotational velocities of flexible continuous structures. The technique uses segments of strain-sensitive materials as transducers. The proposed sensor measures velocity with very little loading compared to conventional means such as linear variable differential transformers (LVDT’s). This technique can be much less costly more practical than other translational velocity measurement.

In one realization, segments of piezoelectric film convert strains on the surface of a beam into electrical outputs. These outputs are connected to signal conditioners with very low impedance. The resulting spatially-discrete signals are then interpolated with a weighting vector that incorporates Lagrange polynomials, specified boundary conditions, and the desired location(s) of measurement. The whole signal processing can be done with a simple analog circuit. Numerical simulations show that the circuit can be used to estimate translational and rotational velocities very accurately.
A Simplified Piston-Ring Assembly Friction Model
Authors: Stanley Richard E. , Taraza Dinu , Henein Naeim A. , Bryzik Walter
Published: January 2022

This paper presents a simplified and efficient piston ring assembly (PRA) friction model of the piston ring pack. The model, which considers both mixed and hydrodynamic lubrication, uses the Reynold’s equation as a governing equation and simplified assumptions to include mixed lubrication. Unique Stribeck curves are generated for a given ring’s geometry and inter ring starvation effects are introduced by varying the boundary conditions, as appropriate. The model is validated by measurements made on a single cylinder diesel engine.
Longitudinal Control of Platoon Treated as One Dynamic System
Authors: Omae Manabu , Fujioka Takehiko
Published: January 2022

In this paper, longitudinal control for a platoon as one dynamic model is investigated by simulation. Difficulty of treating a platoon as one dynamic model is due to non-linearity and uncertainty included in the characteristic of tractive and brake force. A robust model-matching controller is developed for solving the above problem. The characteristic of the tractive and brake force is equivalent to those of a specific transfer function by the model-matching controller. A longitudinal controller for platooning is developed with assumption that the model-matching controller works on each constituent of the platoon. Velocity of the leading vehicle and each spaces between the constituents can be controlled independently and smoothly by the longitudinal controller. The proposed control system is suitable for changing space as well as fixing space, and enables the platoon to execute intelligent tasks according to the various kinds of situations.
Design and Simulations of a Traffic-Friendly Adaptive Cruise Control Algorithm
Authors: Liang Chi-Ying , Peng Huei
Published: January 2022

This paper presents a synthesis method for the design of Adaptive Cruise Control (ACC) algorithms. The control design is obtained on the premise that individual vehicle’s maneuver should produce minimum negative impact on surrounding vehicles. This traffic-friendliness characteristic is achieved by considering the performance of the whole vehicle string. The performance of the proposed ACC algorithm is examined on a microscopic simulation program, the architecture and basic functions of which will also be described in this paper. Both time-domain signals and statistical data are presented.
Integrated Safety Management and Work Smart Standards
Authors: Sturdivant Maggie , Carnes William E.
Published: January 2022

The Department of Energy developed the Work Smart Standards (WSS) concept to provide a work-centered approach for tailored sets of standards to promote improvements in environment, safety and health. As a number of DOE sites were applying the Work Smart approach, the Department also issued requirements for DOE contractors to develop Integrated Safety Management (ISM) Systems. This paper describes how WSS and ISM together are resulting in emerging new understandings about Doing Work Safely. Suggestions are also provided for new ways in which WSS concepts can be applied to implement ISM requirements.
Basaltic Magmatic Intrusion at Yucca Mountain
Authors: Margulies Tim
Published: January 2022

The radiological doses and risks of a probable magmatic event at the Yucca Mountain Nevada waste repository site for spent fuel from commercial power reactors have been estimated. The valuation ($ 2000 per person-rem) of the societal doses with a Poisson stochastic formulation is used to calculate potential resources to avert these risks.
Reasonably Foreseeable Use
Authors: Barnett Ralph L.
Published: January 2022

All technologists design products for an expected use; this use is the goal of the designer. Clearly, the actual use of products by their community of users is broader than the expected use; indeed, the original use contemplated by the designer may be expanded by marketers before the first prototype is finished. Tort law mandates that products be safely designed for their reasonably foreseeable use which includes not only their expected and expanded uses but also their reasonably foreseeable misuses. The concept of reasonably foreseeable use has a literal meaning in technology and this paper explores its impact as a design constraint.
Safety Analysis of Roller Compactors Exposed to Rollover
Authors: Brickman Dennis B. , Barnett Ralph L.
Published: January 2022

Roller compactors exhibit a high resistance to rollover which may be attributed to their low center of gravity, full width rollers, low speed, responsive braking system, high visibility, and operator profile. Tilt table testing of an Ingram pneumatic roller compactor demonstrates that its lateral stability normally exceeds or is comparable to other workplace vehicles. To eliminate or mitigate injuries resulting from roller compactor rollover excursions, a rollover protective structure (ROPS) and seat belt system has been widely debated as a proper countermeasure. Clearly, the roller compactor accident statistics demonstrate the potential of unbelted operators to suffer serious injuries inflicted by the ROPS safety device itself. In the face of reported low seat belt usage, the utilization of the ROPS and seat belt as standard equipment on a roller compactor is not straightforward and value systems are struggling with this dilemma.
Progress in Railroad Freight Car Engineering
Authors: Punwani Swamidas K.
Published: January 2022

The Rail Transportation Division (RTD), American Society of Mechanical Engineers (ASME) annually conducts a survey to document progress in the design, construction and use of freight cars and components. This year’s survey brought responses which indicated that 1998 was not a banner year for new developments. The continued evolution of freight equipment in 1998 focused on flexibility and versatility.
Estimation of Residual Stresses in Railroad Commuter Car Wheels Following Manufacture
Authors: Gordon Jeff , Perlman A. Benjamin
Published: January 2022

A finite element simulation is presented for the prediction of residual stresses resulting from the heat treatment of railroad commuter car wheels during manufacture. The quenching and annealing segments of the wheel manufacturing process are simulated using a decoupled heat transfer and stress analysis. A set of baseline parameters which characterize geometry, material properties and quench characteristics is developed which are representative of current rim-quenching practice. Results indicate the formation of a layer of residual circumferential (hoop) compression to a depth of about 4 cm (1.5 inch) from the tread surface. Variations of these parameters which account for expected ranges in the manufacturing process are shown to have little influence on this finding. The as-manufactured net rim compressive residual stress may be reversed when subjected to service loading in railroad commuter operations. This situation is examined in a companion paper. Tensile stresses at the wheel tread create an environment conducive to the formation of surface cracks that may threaten the safety of train operations. The results of the studies presented in this paper are required to define the initial conditions for analyses of how service conditions may act to change the as-manufactured residual stress state.
Effect of Hollow Worn Railroad Wheels on Fuel Use and Track Damage
Authors: Sawley Kevin J. , Oliva-Maal Diana , LoPresti Joseph
Published: January 2022

The work described contributes to the goal of defining an economic-based criterion for removing or re-profiling hollow-worn railroad wheels. Results from a survey of North American freight car wheels indicates that significant numbers of wheels have hollow-worn treads. The effect of hollow wear on rolling resistance and lateral forces has been investigated using a vehicle dynamics model backed by track tests. Results indicate that hollow wheels impose an economic cost, and, by their effect on lateral track forces, increase the risk of derailment. Prediction and test results have been used as input to an economic model to examine the cost benefits of a removal criterion for hollow-worn wheels. The modeling methods used are general in principle, and are not specific solely to the heavy haul environment.
Effect of Different Thermal Cycles on TBC Spallation Lifetime
Authors: Nusier S. Q. , Newaz G. M. , Chaudhury Z. A. , Chen X. , Khan J. M.
Published: January 2022

The effect of different thermal cycle profiles on thermal barrier coating (TBC) spallation lifetime was investigated. Fick’s law was used to describe the thermally grown oxide (TGO) buildup. It was found that Fick’s law can be used to correlate between damage thickness and oxide thickness for different thermal cycle profiles. A critical oxide thickness of 12 μm can be associated with spallation life for the 8 wt% YSZ /PtAl/Rene N5 EB-PVD system. The importance of this correlation is that, for a given thermal cycle profile, the number of cycles to spallation can be predicted analytically using Fick’s law. The effect of maximum temperature, minimum temperature, holding time, and number of cycles were studied. It was found that by using the actual thermal cycle profile, accounting for cumulative oxide buildup throughout the complete cycle, the TBC spallation lifetime can be estimated reasonably well.
Fatigue Behavior and Life Simulation of Torsion Loaded Glass Fiber/Vinylester Tubes
Authors: Himmel Norbert A. , Kienert Michael C.
Published: January 2022

The fatigue characterization of resin matrix composite materials is still quite a demanding subject due to the variety of interacting damage mechanisms including matrix cracking, debonding, delamination and fiber fracture rather than one distinguished damage event as in metals. The subject of the present study was the investigation of the torsion fatigue behavior of filament wound glass fiber/vinylester tubular specimens and its fatigue life estimation. To provide the experimental data constant amplitude tests were carried out under torque ratios R = +0.1, −0.4 and −1.0. Two-step R = −1.0 block loading experiments were performed to investigate potential load sequence effects. Finally, a spectrum load profile derived from a real car drive shaft test was applied to elevated length specimens incorporating a realistic loading situation and a structural size level in the study. Parallel to the experiments fatigue life predictions based on the critical element method, the residual strength degradation concept and the linear damage accumulation rule were carried out. The paper presents the relevant experimental results and the comparison with fatigue life predictions.
Simulation of Fatigue Performance of Polymeric Composites for Infrastructure Applications
Authors: McBagonluri Fred , Foster Glenn , Case Scott , Curtin Bill , Lesko John
Published: January 2022

A simulation model which incorporates a fracture mechanics-based residual strength model for glass fiber in the statistical- and numerical-based Lattice Green Function Local Load Sharing Model has be developed. The simulation of the fatigue of glass fiber-reinforced composites is achieved by replacing the constant stress parameter in the model with a sinusoidal wave function. Recognizing Mandell’s stipulation, that fatigue failure in glass fiber-reinforced polymeric composites is a fiber-dominated mechanism with a characteristic slope of 10%UTS/decade, simulation results are shown consistent with available experimental data. The slopes of simulated S-N fatigue curves at three frequencies namely: 2, 5 and 10 Hz are within 12–14 UTS/decade compared with 10.6–13 UTS/decade for unidirectional glass reinforced composites (epoxy and vinyl ester).
Growth of Face-Sheet Delaminations in Sandwich Beams Under Compression or Bending
Authors: Kardomateas G. A.
Published: January 2022

A bending load on a sandwich beam consisting of two fiber-reinforced sheets separated by a low stiffness core is equivalent to a compressive force on one face and a tensile force on the other. Should an interlayer crack in the composite face sheet (delamination) exist on the compressively loaded face, local buckling and subsequently growth of the interface crack may occur. This may also naturally occur under pure compression. In these cases, the composite face rests on an elastic “foundation” (the core), which imposes reaction forces proportional to the deflection of the “foundation”. In this study, the buckling and initial postbuckling behavior is studied through a perturbation procedure. The solution, derived in closed form, is subsequently used to study the growth of the mixed mode crack during the initial postbuckling phase. To this extent, the energy release rate and the Mode I and II stress intensity factors are obtained in terms of the loading and geometric parameters.
Mold Filling Simulation of Sandwich Composite Structures Manufactured by Liquid Molding
Authors: Nedanov Pavel , Advani Suresh G.
Published: January 2022

The mold filling stage in the manufacturing of sandwich composite structures with fiber reinforced foam core was studied with numerical simulations. Three different geometries of sandwich core reinforcement were considered: in the form of fiber layers forming angle 45° or 90° with the facings or in the form of equally spaced separate strands (webs). The influence of variable core and face reinforcement permeability and location of the injecting edge on the flow front progression and filling time was explored. The results suggest that permeability of the core has a significant influence on filling pattern and mold filling time. Experimental and predicted flow front developments for a case of radial injection were compared.
Circular Cylindrical Sandwich Shells With Midplane Asymmetry Subjected to Axially Symmetric Loads
Authors: Preissner Eric C. , Vinson Jack R.
Published: January 2022

Solutions for the displacements and stresses in circular cylindrical shell structures subjected to axially symmetric loads are presented for the cases of the shell construction having a midplane asymmetry. For sandwich constructions this can mean faces of the same material with different thicknesses, faces of different materials, or all of the above. A midplane asymmetry parameter ϕ is used wherein −1 < ϕ < +1 for all physically possible cases, and this parameter facilitates the case of a perturbation solution to the generic problem. By an example it is shown that through such asymmetric construction, bending stresses can be minimized or negated.
Application of Composites in Helicopter Design at Sikorsky Aircraft
Authors: Dobyns Alan L.
Published: January 2022

The history of advanced composites usage at Sikorsky will be discussed, starting with small components in the 1970s up to the present where the structure of the RAH-66 Comanche helicopter is constructed almost entirely of composites. One of the initial composite components developed in the 1970’s was a reinforcing Boron strap for the tail of the UH-54 Skycrane. In the 1980’s the UH-60 Blackhawk and the S-76 production aircraft employed a graphite/epoxy tail rotor flexbeam. In addition a composite rear fuselage was developed for the UH-60 Blackhawk, and an all composite research helicopter was built under Army contract to develop composites technology (the S-75 ACAP). Also, graphite/epoxy composite fuel sponsons were put into production for the MH-53E Super Stallion. In the 1990’s the RAH-66 Comanche attack helicopter was developed, utilizing a graphite/epoxy-honeycomb primary structure. The S-92 Helibus commercial helicopter uses graphite/epoxy fuel sponsons, tail rotor flexbeams, and numerous fairings.
Cumulative Lifetime Loadings for Naval Ships
Authors: Sikora Jerome P.
Published: January 2022

The seaway loadings upon ships are inherently random in nature and can best be described by probabilistic methods. The primary loadings are those that cause a response of the overall hull girder and consist of vertical bending moments, lateral bending moments, and torsional moments. Since it is highly probable that these loads can be severe, it is important to predict the maximum lifetime or extreme values. Of equal concern is the cumulative effect of all of the waves upon the fatigue life of the ship. This paper presents a probabilistic method for predicting both the extreme and fatigue loadings in a unified and consistent manner.

The first part of the seaway loading is the low frequency, wave buoyancy contribution. This loading distribution is obtained by dividing the lifetime of the ship into two thousand stochastic cells defined by operability (probabilities of ship heading and speed) and sea conditions (wave height probabilities and spectral parameters). The ship response in the frequency domain (Response Amplitude Operators, RAO’s) for each operability condition is multiplied by the ocean spectrum for each wave height and spectral shape. The resulting response spectra produce the probability distributions for determining extreme and cumulative wave buoyancy loadings. This paper presents unique algorithms for the bending and torsional RAO’s based upon extensive model test and sea trial data, as well as data validating the probability distributions.

The second part of the seaway loading is the dynamic (high frequency) contribution from slam-induced whip-ping. The probability distributions for the filtered, high frequency responses were determined from model tests and sea trials. Algorithms for predicting the dynamic contributions to vertical and lateral bending are developed as functions of ship geometry, operability, and sea parameters. The whipping distributions are then combined with the wave distributions to form distributions for the total primary load for each cell. The method of combination accounts for the phasing of the slam event with the wave buoyancy cycle and includes algorithms for the hydrodynamic damping. A cumulative lifetime load distribution is then formed from the summation of all of the wave events in all of the cells. The cumulative exceedance load distribution is used for predicting both extreme events and fatigue lives.
Variable Structure Adaptive Force Tracking Control of a Cantilever Beam Using Piezoelectric Actuator
Authors: Yim Woosoon , Singh Sahjendra N.
Published: January 2022

This paper presents a robust force tracking control of a flexible beam using piezoceramic actuator. Based on the variable structure model reference adaptive control theory, a new force tracking control system using only force measurement is designed. For the derivation of the control law, it is assumed that parameters of the beam and contact surface stiffness are unknown. It is shown that in the closed-loop system designed using bounds on uncertain functions, the contact force tracks a given reference trajectory and beam vibration is suppressed. Digital simulations results show that the closed-loop system has a good transient behavior and robustness to uncertainties of beam’s dynamic parameters and unmodeled dynamics as well as contact surface property, which is modeled by a spring.
Stability and Robustness of Time Periodic Systems Under Random Parametric Perturbation
Authors: Sinha S. C. , Liu Jianhui
Published: January 2022

In this study, the stability and robustness of a linear time-periodic system subjected to a random parametric perturbation is investigated. Using the Lyapunov-Floquet (L-F) transformation and Lyapunov’s direct method, the stability/robustness bounds are obtained in terms of the Floquet exponents of the system. Two examples are included to demonstrate the applicability of the method to real engineering problems. The first example consists of a commutative system for which the L-F transformation can be computed in a closed form. In the second example, the stability and robustness of a Mathieu equation under arbitrary parametric perturbation is considered. Limiting mean square values of disturbance are computed to guarantee the almost sure asymptotic stability of the system.
Investigation of Perturbations in the Angle of Incidence for Constant Radius Acoustic Transducers
Authors: Bailo Kelly C. , Brei Diann E. , Grosh Karl
Published: January 2022

Curved piezoelectric polyvinylidene flouride (PVdF) acoustic transducers have shown promise for use in active noise cancellation and sound generation applications. Much of the past research has concentrated on straight or semi-circular transducer configurations. This work investigates a constant radius PVdF acoustic transducer with angle of incidences varying from 0° (straight) to greater than 90° (semi-circular). Acoustic performance models were developed and experimentally validated. Computer simulations based upon both the models and experiments were used to determine the device sensitivity to variations in the angle of incidence with respect to the fixed constraints. Acoustic sound intensities were found to dramatically increase as the angle of incidence was decreased from semi-circular to a shallow angle. In addition, sound levels increased significantly when the transducer was varied from straight to a shallow curved configuration. By varying the angle, the curved PVdF transducer has the capability to generate high sound intensities (over 100 dB) at distances greater than one meter in the frequency range below 2000 Hz. The optimal angle was observed to vary with transducer geometry and operating frequency.
Optimal Design of a Sensorless Magnetic Suspension System Using a Tuned LC Circuit
Authors: Krause Robert M. , Sinha Alok
Published: January 2022

In the existing literature, a sensorless AC magnetic suspension system which does not require direct damping of the suspended object for stability has been proposed. This is accomplished by suspending the electromagnet with a spring and damper. First, using a linearized transfer function model for the overall suspension system developed by Jin and Higuchi (1994), a study of the system’s stability is presented in this paper. A root locus is then used in order to see how the damping applied to the electromagnet affects stability. Next, optimization methods and results are proposed to determine values for indirect spring stiffness and damping to most effectively stabilize the system. Lastly, results from linearized analyses are compared to those from numerical integration of the nonlinear system of differential equations.
A Comparison of Placement Choice for Piezoelectric Actuator and Generalized Point Actuator in Active Vibration Control
Authors: Zhu Xuegeng , Alberts Thomas E.
Published: January 2022

A cantilevered beam is used to demonstrate the difference in placement index between piezoelectric actuator and generalized point force actuator. Since the effectiveness of the piezoelectric actuator is dependent upon the curvature of the mode shape, the results proposed for generalized actuator placement do not guarantee good performance for the piezoelectric actuator.
Effect of Manufacturing Induced Defects on the Reliability of Flip-Chip Packages
Authors: Wang Jianjun , Zou Daqing , Qian Zhengfang , Ren Wei , Liu Sheng
Published: January 2022

A combined experimental and numerical studies are conducted to investigate whether the reliability of flip-chip solder interconnects are affected by the manufacturing induced defects (non-cleaning situations), in which underfill cannot be completely filled in the corners of the solder balls because contamination like flux residues subsist on those parts after solder reflow. The real-time moiré interferometry technique is used to measure the warpage for the selected “cleaning” and “non-cleaning” flip-chip package specimens during the test. A nonlinear finite element technique, in which the viscoplastic material properties (strain rate-dependent) of solder balls and underfill are considered, is adapted to simulate the corresponding “cleaning” and “non-cleaning” samples to assess the impact on solder interconnect reliability. The non-cleaning test and simulation results are contrast to the cleaning test and simulation results considered by many researchers. The results indicate that there is no obvious difference for the warpage obtained by either the test data or the numerical analyses between the cleaning samples and the non-cleaning samples. However, the simulation results of the stresses (strains) reveal that the non-cleaning situation decreases the mechanical stability and shortens the life time of those flip-chip packages to a level well below the predictions of the cleaning simulations. The fatigue life in some points of the outmost solder joint predicted by using the cleaning FE models is much higher than that predicted by using the non-cleaning FE models. Since it is hard to find perfect filled layers for any real world samples, the cleaning model yield overly conservative results. In addition, the predicted deformation values of the flip-chip package obtained from the finite element analysis are also compared with the test data obtained from the laser moiré interferometry technique. Good agreement is obtained. In particular, the displacement contours of the flip-chip package samples both in the x and y directions obtained from the test show similar distribution patterns compared with those modeled by the finite element method.
Thermal Deformation Analysis of a Plastic Quad Flat Package by Hybrid Moiré and Finite Element Method
Authors: Liu D. S. , Hsu S. C. , Tung Y. C.
Published: January 2022

This paper presented a hybrid computational models that can be use as design tools to study the thermal deformation of a PQFP. A whole field optical testing method moiré interferometry were applied first to detect thermal strain within the packages cut plane with high sensitivity 2400 lines/mm and the effects of temperature change in the range from 80 up to 120 degree °C. Full field strain maps were measured and the effective CTE properties of the materials used in PQFP can also be obtained from the thermal deformations. Next, a three-dimension finite element model of PQFP was built and analyzed with the material constitutive law and the CTE values found by Moiré. The thermal deformation predict by this hybrid FE model was re-compared with Moiré testing data to validate the accuracy of the FE model. Once the FE Model that compare well with Moiré testing data then it can be used for further structural modification studies.
Thermal Characterization of Anisotropic Polymer Films for Electronic Systems
Authors: Kurabayashi K. , Asheghi M. , Touzelbaev M. N. , Goodson K. E.
Published: January 2022

Polymer films are playing an important role in the development of fast integrated circuits, novel micromachined sensors and actuators, organic optoelectronic devices, and advanced packaging and underfill structures. The low thermal conductivities of polymer layers yield large temperature rises and temperature gradient magnitudes that strongly influence performance and reliability. This work develops three experimental techniques for measuring both the in-plane and out-of-plane thermal conductivities of spin-coated polyimide films of thicknesses between 0.5 and 2.5 μm and at temperatures between 260 and 360 K. Two of the techniques use transient electrical heating and thermometry in micromachined structrures to isolate the in-plane and out-of-plane components. These techniques are used to establish confidence in a third, simpler technique, which is fully IC compatible micromachining and measures both components independently. The data illustrate anisotropy in the thermal conductivity of the polymide films investigated here, with the in-plane conductivity larger by a factor between 4 and 8 depending on thickness and temperature.
Secondary Flows of a Viscoelastic Fluid in Pipes of Complex Cross-Section Shapes
Authors: Siginer Dennis A. , Letelier Mario F.
Published: January 2022

The transversal flow field in pipes of non-circular cross-section shapes is determined for a Green-Rivlin fluid. An analytical approach is presented, which is applicable to unsteady flows driven by small amplitude pressure gradients. Both the longitudinal flow velocity and secondary velocity components are found by prescribing a pipe contour through a shape factor conveniently defined. Secondary flow patterns are computed for several pipe shapes. Results are presented herein for the specific cases where the shape factor prescribes tube cross-section of approximately triangular, square and pentagonal shapes.
Drag Reduction in Turbulent Flow of Gas-Solid Mixtures
Authors: Buyevich Yuri A. , Kapbasov Shakir K.
Published: January 2022

Well-developed one-dimensional steady turbulent flow of a dilute gas-solid mixture in a vertical pipe is considered on the basis of a closure model that accounts for the Reynolds stresses in both mixture phases and specific pseudoturbulent stresses that arise in the dispersed phase. The model is proven to be in an excellent agreement with experimental data as regards usually observed cross-sectional profiles of mixture concentration and mean velocities of the phases. This model is applied to evaluate a systematic variation in total gas flow rate caused by the insertion of fine particles into pure gas flow under the condition of the overall pressure drop being kept invariable. For this purpose, the ratio of gas flow rate in the pure gas flow to that in a mixture flow was studied as a function of the mixture concentration and other relevant parameters. All other things being equal, this ratio first decreases below unity as the amount of the inserted particles increases, reaches a minimum, and then begins to grow with concentration, eventually assuming values well above unity. This means that a drag reduction effect occurs if the concentration varies within a certain interval of relatively low concentrations, but if gives way to a drag enhancement effect as concentration further increases beyond the said interval.
Periodic Motion in Multiparticle Settling
Authors: Zhu Qinsheng , Clark Peter E.
Published: January 2022

Particle settling in quiescent fluids is important in many industrial processes. Single particle settling in Newtonian fluids has been studied extensively. Less work has been done in non-Newtonian fluids using both single and multiple particles. Two or more particles settling in non-Newtonian fluids exhibit unusual behavior that includes simple interactions to form a coupled pair and periodic motion in which the particles preform a complex “dance” as they move through the fluid. This paper describes some preliminary work on the periodic motion observed in three and four particle systems.
Heat Transfer and Fluid Mechanics of Herschel-Bulkley Fluids
Authors: Vradis George C.
Published: January 2022

A comprehensive review of the heat transfer phenomena related to the flow of purely viscous non-Newtonian fluids exhibiting a yield stress in some simple and complex geometries is presented. Both attached and separated flows of Bingham and Herschel-Bulkley fluids are discussed. The presence of a yield-stress is shown to significantly impact the heat transfer and flow characteristics, as compared to those in the case of a Newtonian fluid, in particular in the cases where separation of the flow would be expected.
Electrorheology of Chitin and Chitosan Suspensions: Conductivity vs Molecular Structure
Authors: Choi Ung-su , Conrad Hans
Published: January 2022

The electrical and rheological properties pertaining to the electrorheological (ER) behavior of chitin and chitosan suspensions in silicone oil were investigated. Chitosan suspension showed a typical ER response (Bingham flow behavior) upon application of an electric field, while chitin suspension acted as a Newtonian fluid. The difference in behavior results from the difference in the conductivity of the chitin and chitosan particles, even though they have a similar chemical structure. The shear stress for the chitosan suspension exhibited a linear dependence on the volume fraction of particles and a 1.18 power of the electric field. The experimental results for the chitosan suspension correlated with the conduction model for ER response.
Secondary Control Technology and Applications
Authors: Wüsthof Peter
Published: January 2022

Secondary control is the definition for a variable displacement rotary hydrostatic drive working with constant pressure. The controlling element of the system is the swivel angle of the hydraulic drive, normally an axial piston unit. If a load change occurs, the secondary control reacts immediately by accelerating or decelerating the process, thus maintaining a constant speed. Compared to conventional hydrostatic drives the secondary control is a dynamic drive.
A Comparison of a PID Controller to a Neural Net Controller in a Hydraulic System With Nonlinear Friction
Authors: Qian W. , Burton R. , Schoenau G. , Ukrainetz P.
Published: January 2022

Neural networks have been applied to a wide spectrum of applications in the last decade, including the fluid power area. The popularity of neural networks can be attributed, in part, to their ability to deal with nonlinear systems. Their use as a controller, however, poses many interesting problems, especially when trying to apply them to practical systems. In hydraulics, PID controllers have been used with some degree of success; however, when it comes to highly nonlinear systems, this established method encounters some difficulties.

This paper considers the applied problem of a hydraulic servovalve controlling a actuator with nonlinear friction characteristics. A neural net controller is pre-trained to the performance of a special PID controller which has been tuned to a specific waveform. The plant is a model of a hydraulic servovalve and a linear actuator with slip-stick friction characteristics. The neural net controller replaces the PID controller and shows superior performance for waveforms that it was not trained for. The addition of a “kicker” signal reduced the distortion of velocity (a consequence of nonlinear friction) when the velocity was near zero. It is concluded that in certain applications, a neural net controller does show potential for use in nonlinear systems, but many other issues such as stability, reliability, and adaptability must be addressed in the future.
Nonlinear Robust Control of an Electro-Hydraulic Positioning System
Authors: McLain Timothy W. , Beard Randal W.
Published: January 2022

In this paper, a novel approach for the formulation of nonlinear H∞ control laws is applied to the position control of an electro-hydraulic servo system. These robust controllers are obtained by numerically approximating the solution to the Hamilton-Jacobi-Isaacs (HJI) equation and result in nonlinear control laws in feedback form. The approximation is accomplished by a two-step successive Galerkin approximation strategy. The application of this approach to the control of a hydraulic positioning system with uncertain fluid bulk modulus and density is described.
Theoretical and Experimental Research on Sliding Mode Control for an Electrohydraulic Servosystem
Authors: Liu Y. , Handroos H.
Published: January 2022

The present paper discusses a sliding mode control method suitable for controlling a hydraulic position servo with a flexible load. Due to the requirements of the control system, the reference model is designed for case of a flexible load. The core of sliding mode control is switching surfaces which are specially defined for the system according to the mathematical model and control goal. A novel algorithm is developed, and the simulated and experimental results of the control system are shown. The results show the extremely good robustness of the proposed method.
Dual Electrohydraulic Servo Motors Synchrodrive System Using Adaptive Neural Control Strategy
Authors: Xingwu Fu , Keding Zhao , Qinghe Liu
Published: January 2022

The adaptive neural control strategy is employed for the characteristics and specifications of the middle gimbals synchrodriven by the dual electrohydraulic servo motors in the simulator with three axes, the decoupling is implemented. Simulation results show that this strategy, because of it’s self-learning and inherent nonlinear, etc.[1], makes the system present superior dynamic performance and adaptability, the superior synchromotion performance of the system has been obtained.
Transient Flow Force Estimation on the Pilot Stage of a Hydraulic Valve
Authors: Borghi M. , Milani M. , Paoluzzi R.
Published: January 2022

The effect of flow forces on the spool equilibrium of hydraulic components is well known, and a number of methods have been developed in order to estimate their effect. They span from analytical expression, to experimental evaluation, to CFD analysis. This last approach is usually considered too demanding to the purpose of hydraulic component design, however a careful approach to the problem statement can lead to the collection of a complete set of data, starting from a limited number of numerical runs. A further extension to transient flow is made possible by the acceptance of further approximations on the effect of fluid compressibility, leading to a computational technique able to extend the amount of information extracted from a single model.
Several Aerospace Applications of Computational Aeroacoustics
Authors: Long Lyle N. , Morris Philip J. , Ahuja Vineet , Hall Chris M. , Liu Jingmei , Scheidegger Thomas E. , Shieh Chingwei M.
Published: January 2022

This paper describes some recent Computational Aeroacoustics (CAA) simulations of problems of practical importance. Many previous CAA studies have emphasized the development of algorithms and their application to relatively simple model problems. Examples of computational aeroacoustic calculations are given for ducted fans, rotors, cavities, engine inlet liners, and jets. The need for three-dimensional, non-linear simulations and the feasibility of such solutions on high performance parallel computers is emphasized.