bluuebunny/crossref_metadata_2025 huggingface dataset:
KADS2: A Next Generation Knowledge Aided Design System
Authors: McVea William M. , Haghighi Kamyar
Published: February 2021

Research has been conducted in the areas of design methodology, automation and use of knowledge based systems as a tool to improve the design efficiency, accuracy and consistency for mechanical power transmissions. The research capitalized on previous work related to component level design synthesis and analysis. The next logical step in the research progression was to look into system development and integration of design synthesis and analysis tools. Deliverables from this research include new knowledge acquisition techniques, a more complete model of design information flow and development and a knowledge based design assistant system, capable of integrating multiple discrete and disparate design tools.
A Feature Free Approach to 5-Axis Tool Path Generation
Authors: Laxmiprasad Putta , Sarma Sanjay
Published: February 2021

In recent years, CAD/CAM integration for machining has been based on the concept of manufacturing features. In this paper we present an overview of an alternative scheme to integrate CAD with CAM. Instead of decomposing the design into manufacturing features, we generate tool paths directly from the shape of the workpiece using visibility and accessibility arguments. This approach builds on the work of a number of previous efforts to bring concepts from robotic path planning into the realm of NC planning. We present a hardware approach for computing visibility rapidly. This information is then used to determine the “principal directions”, or setups, around which the search will be conducted to remove material from the workpiece. The machining is conducted in two stages. The first stage, global roughing, is performed for each principal direction. The bulk of the material is removed through 5-axis roughing tool paths. Algorithms have been developed to generate these tool paths in an efficient way. The removal volume is first stratified into “4−1/2D machining pockets”, for which tool paths are generated with simple “space filling 2D curves based on the Voronoi Diagram. After global roughing, the surface of the part can be finished with “face based finishing.” In this step, each face is independently machined to the required finish and accuracy using a face-oriented, rather than feature-oriented, approach. The primary concern is to meet accessibility constraints for each face while generating tool paths individually. Once toolpaths have been generated, we simulate them and correct residual intersection problems before outputting final NC code. Since this is an overview paper that attempts to summarize current and future research in an ongoing project, we concentrate on some key issues such as accessibility, while only summarizing other individual ideas briefly. We also present some experimental results through illustrations.
Toward Hybrid Variant/Generative Process Planning
Authors: Elinson Alexei , Herrmann Jeffrey W. , Minis Ioannis E. , Nau Dana S. , Singh Gurdip
Published: February 2021

This paper describes our ongoing work on a hybrid approach to process planning, that attempts to combine the best characteristics of both variant and generative process planning while avoiding the worst limitations of each. Our approach uses a database of designs and process plans that are classified using design signatures, graphical structures based on detailed product design attributes that are more meaningful and accurate than GT codes and can be computed automatically from the designs stored in the database. We are developing ways to use design signatures to classify and retrieve “slices” of designs and plans, so that when a process plan is needed for a new design, we will be able to retrieve the plan slices that are most relevant, and combine them and modify them to produce a plan for the new design.
OSCAP: An Environment for Manufacturing Planning of Mechanical Products
Authors: Yang Zhi-Xin , Joneja Ajay
Published: February 2021

This paper describes an open-architecture system for computer-aided process planning called OSCAP. The system is different in architecture from traditional integrated process planning systems, since it is designed specifically to integrate with existing partial planning software with little effort. It does provide all functions of design and process planning for machining of mechanical parts on 3-axis machining centers. Special features of the system include a sophisticated feature recognition system, an optimal machining planner, automated fixture synthesis, setup planning with operation sequencing, and a knowledge based system organizer called the OSCAP core which orchestrates the functioning of all modules. The system can be arbitrarily extended or collapsed by adding or removing functional modules.
Knowledge-Based Design Tool to Support Integrated Manufacturing
Authors: Allada Venkat
Published: February 2021

Advanced CAD design tools that facilitate designers to produce manufacturable designs right the first time are needed to compress product realization cost and time. Such tools must facilitate artifact diagnosis regarding its manufacturability during early design stages. This study focuses on identifying the major issues in the development of a knowledge-based design tool to evaluate artifact manufacturability. A prototype integrated design and manufacturing (IDM) system has been developed for conducting machined part evaluation. The IDM system is implemented on a SunSparc 20 workstation using the ACIS v1.7 geometric modeler, the C++ programming language, and MOTIF. The concepts of feature flexibility and feature importance introduced in this study can be used to provide appropriate context-sensitive “intelligent” repair (redesign) advice to the designer after identifying portions of a design artifact that are difficult/impossible to manufacture. A preliminary discussion on the issue of ranking of redesign solutions based on designer’s objective functions is also presented.
FixtureNet II: Interactive Redesign and Force Visualization on the Web
Authors: Anderson Charles , Zhuang Yan , Goldberg Ken
Published: February 2021

Digital communication over the Internet offers advantages in terms of speed, efficiency and automation. Fortunately, new geometric algorithms for design, simulation, and manufacturing have been developed and reported in the research literature. Unfortunately, the impact of these advances on the manufacturing community has been limited since implementations are difficult to port from one platform to another.

As an example of how the Web can facilitate interactive design, we focus on one specific application area: modular fixture design. We have substantially extended our previous fixture design service, FixtureNet (Wagner et al., 1996), and added interactive tools to allow the user to build a deeper, more intuitive understanding of the fixtures found by FixtureNet. The first tool allows the user to simulate the effects of forces applied to the part in the fixture. Our second tool enables the user to consider changes to a part and verify in real-time that the fixture will still immobilize the modified part.

Our tools balance the tasks between the Web client and a central server, performing fast user interactions in the client while running compute-bound fixture design jobs on the server.

The implementation of this work can be found online at: http://riot.ieor.berkeley.edu/riot/Applications/FixtureNet.
Non-Verbal Transfer of Skill
Authors: Fukuda Shuichi , Matsuura Yoshifusa , Takahashi Tokiko , Wongchuphan Premruedee
Published: February 2021

It is becoming more and more important to consider how we should integrate our knowledge of skills into design, if we really wish to integrate design and manufacturing, because skills play very important roles in manufacturing. Although there are many design systems available, most of them deal only with the symbolic representation of our knowledge and even such media as TV, video, etc. which are considered to be good for skill representation are still in most cases one way from a teacher to a student. To really learn a skill, feedback from a student to a teacher should be established and more interactiveness secured.

We developed a prototype system with the simple example of learning the skill of penmanship for the purpose of clarifying the problems of skill representation and with the hope of integrating skill knowledge into design in the future.
Networkcentric Buddy System for Collaboration
Authors: Fukuda Shuichi , Matsuura Yoshifusa , Kandie Kigen , Nakajima Yoshiyuki
Published: February 2021

With the increasing diversification, complexity and globalization of our society, distance learning is gathering wide attention because it is expected it will provide a very flexible learning environment.

But most of the conventional distance learning systems are still of such presentation types as TV, Video, etc, which passes information only from a teacher to students, and they are developed without any consideration to the interaction among students. Thus, although the system may be described as being the system for one to many relation, the fact is that a teacher has to take care of each student independently so that the burden of a teacher increases tremendously with the increase of the number of students.

Although TV conferencing type systems have been introduced into the area of distance learning recently, the consideration of the interaction among students is still poor.

In the conventional classroom, at least in Japan, not only teacher-student relation is important, but also student-student relation is none the less important, because it will constitute a buddy system among themselves and they learn interactively by playing the role of a teacher from time to time. And this serves a great deal in letting them find important points by themselves and raise new questions.

This has an advantage on the part of a teacher, too, because it will greatly reduce his or her burdens, and make it possible for him or her to adapt to each classroom situation and change their pace or contents of teaching.

Therefore, we developed a networkcentric prototype system for interactive distance learning, considering not only interaction between a teacher and a student but also among students. This system will largely reduce the burden of a teacher because it will facilitate the collaboration in learning among students and because it is developed based on a client/server approach and by evaluating the progress of each student.

The introduction of a client/server approach makes it possible to manage the personal records of each student’s achievement level on a server and to construct a hierarchical structure automatically based upon them. Thus, well advancing students can play the role of a teacher when needed and students can learn very interactively and very collaboratively, thus reducing the burden of a teacher to a great extent.

It should be stressed that the same kind of problems arise between a designer and manufacturing engineers. Up to now, our information flow is one way from designer to manufacturing engineers and although concurrent engineering succeeded in realizing interactions between designers and manufacturing engineers, the interaction between manufacturing engineers are still very poor so that it will eventually increase the burden of designers which will result in poor quality design or in poor decision making at the earlier stages.
Enabling Virtual Reality for Large-Scale Mechanical CAD Datasets
Authors: Varshney Amitabh , El-Sana Jihad , Evans Francine , Darsa Lucia , Costa Bruno , Skiena Steven
Published: February 2021

Reconciling scene realism with interactivity has emerged as one of the most important areas in making virtual reality feasible for large-scale mechanical CAD datasets consisting of several millions of primitives. This paper surveys our research and related work for achieving interactivity without sacrificing realism in virtual reality walkthroughs and flythroughs of polygonal CAD datasets. We outline our recent work on efficient generation of triangle strips from polygonal models that takes advantage of compression of connectivity information. This results in substantial savings in rendering, transmission, and storage. We outline our work on genus-reducing simplifications as well as real-time view-dependent simplifications that allow on-the-fly selection amongst multiple levels of detail, based upon lighting and viewing parameters. Our method allows multiple levels of detail to coexist on the same object at different regions and to merge seamlessly without any cracks or shading artifacts. We also present an overview of our work on hardware-assisted image-based rendering that allows interactive exploration of computer-generated scenes.
Real-Time Particle Simulation for Virtual Environments
Authors: Assadi Armand D. , Oliver James H.
Published: February 2021

A real-time interactive environment for particle simulation is presented with specific attention given to fluid flow from a fountain system. The complex Navier-Stokes equations from fluid dynamics theory give way to simple dynamic equations of motion for systems of independent particles from particle theory. Due to the ease of integration of the dynamic linear first order differential equations, compared to the nonlinear second order partial differential equations of Navier-Stokes, a real-time rate was achieved for a visually aesthetic model of fluid flow. The primary contribution is that interactive changes made by the user are perceived to occur simultaneously in the environment. There is no need to resolve a predetermined set of equations when making the changes.
Creative Design Methodology and the SIT Method
Authors: Horowitz Roni , Maimon Oded
Published: February 2021

The paper presents SIT (Structured Inventive Thinking) — a structured method for enhancing creative problem solving in engineering design. The method is a three step procedure: problem reformulation, general search strategy selection, and an application of idea provoking techniques. The most innovative part of the method is the problem reformulation stage. The given problem is modified through the application of objectively defined and empirically tested set of sufficient conditions for creative solutions. The paper describes the sufficient conditions and the empirical study that demonstrates their appropriateness. Then the whole SIT mechanism is presented with illustrative examples.
Application of Interaction and Functional Coupling Rules in Configuration Design
Authors: Johannesson Hans L.
Published: February 2021

In this work a procedure to identify and characterize functional couplings, previously proposed by this author, has been applied in configuration design of an expansion container of an automotive cooling system. The procedure is based on axiomatic design theory, function-means structure modelling techniques, the interaction characterization scheme proposed by Pimmler and Eppinger and two functional coupling definitions proposed by this author.

The presented case study illustrates the use of the proposed procedure to identify and characterize functional couplings in configuration design. The result of the procedure is a function-means model of the design with interaction and functional coupling relations included in the model.

When the functional couplings are known the structure model can be used as an aid for different purposes such as feasibility analysis according to the axiomatic design theory and design task planning.
Functional Analysis: A Fundamental Empirical Study for Reverse Engineering, Benchmarking and Redesign
Authors: Little Aaron D. , Wood Kristin L. , McAdams Daniel A.
Published: February 2021

At a basic level, product design composes three primary tasks: specification development, conceptual and configuration design, and product refinement. Customer needs analysis, product benchmarking, and business case analysis are fundamental to specification development, whereas conceptual design and product refinement entail functional analysis, the generation of solution principles and product geometry, concept selection, mathematical modeling, prototyping, and Taguchi analysis for variability. In this paper, we focus on an advanced method for functional analysis. This method demonstrates clear ties to customer needs, and is based on an empirical study of 58 household consumer products. As part of this study, a common vocabulary for product functions and flows is developed and applied to the consumer products. House of Quality results are then used to correlate customer importance to the product functions. Data from these correlations provide a basis for determining critical functions and flows across all products and within important product domains, such as material processors and beverage brewers. From this study, we discuss how the results can be applied to product testing and benchmarking, design by analogy, the identification of functional groups and dependencies, and design education.
The Role of Simulation Software in an Ideal Learning Environment
Authors: Reamon Derek T. , Sheppard Sheri D.
Published: February 2021

For years, computers have promised to revolutionize education. Educators crave and skeptics demand justification for the large outlay of resources required to introduce information technology into the curriculum. Engineering educators have drawn upon the work of education theorists, computer scientists and communication experts to explore the effectiveness of this promising technology in their curricula.

This paper analyzes three pairs of students using various solution techniques to solve a mechanical engineering design problem. We will focus on the use of a computer-based simulation tool and its effect on the students’ process of solving the problem. We will use two learning theories to explore the learning environment and draw conclusions about the effectiveness of the computer simulation for teaching engineering.
Part Nesting As a Plastic Snap-Fit Attachment Strategy
Authors: Luscher Anthony F. , Bonenberger Paul R.
Published: February 2021

Traditional snap-fit design methods focus exclusively on design of an individual locking feature such as a cantilever hook or an annular lock. Location and orientation of other significant features on the two joined parts are not considered. This paper presents: (1) a comprehensive design methodology for nesting plastic parts via snap-fits and, (2) the concept of a part nesting table to encourage good design practices.

This nesting approach is based on relatively new methodologies and guidelines for arranging features on a plastic part. The authors advocate a nesting which is a statically determinate assembly and minimizes the use of snap-fit features. The advantages of such an assembly include robustness with respect to tolerance and warpage concerns, maximum utilization of existing “natural” part features, and a reduction in the number of locking features needed. The entire process is presented as an improved paradigm for attachment design and assembly.

It presents the concept of a part nesting table to help designers produce nested plastic assemblies. In this approach, degrees-of-motion to be removed are represented as columns in a table, and individual features are entered as rows. Advantages of this structured approach include recognition of under constrained and weakly constrained assemblies, identification of over constrained assemblies, and first-level optimization of lock location and assembly direction. Work is continuing on computer implementation of this approach so that force and moment values can be deduced at the feature level.
Concurrent Engineering Design of Sheet Stamping by Using an Inverse FE Approach
Authors: Yang Shiyong , Nezu Kikuo
Published: February 2021

An inverse finite element (FE) algorithm is proposed for sheet forming process simulation. With the inverse finite element analysis (FEA) program developed, a new method for concurrent engineering (CE) design for sheet metal forming product and process is proposed. After the product geometry is defined by using parametric patches, the input models for process simulation can be created without the necessity to define the initial blank and the geometry of tools, thus simplifying the design process and facilitating the designer to look into the formability and quality of the product being designed at preliminary design stage. With resort to a commercially available software, P3/PATRAN, arbitrarily three-dimensional product can be designed for manufacturability for sheet forming process by following the procedures given.
Robust Passive-Active Mounts for Machinery and Equipment
Authors: Su J. Hannsen
Published: February 2021

Conventional vibration isolation mounts are not as effective as expected on a practical foundation whose resonant frequencies normally are within the bandwidth of interest. In addition, the low frequency enhancement is a characteristic of the passive mounts. Applying inertia actuators to the bottom attachment plate of the conventional mounts overcomes these shortcomings and enhances their performance significantly. This design concept has universal application since it is applicable to any dynamic system. It requires very little power and force capacity, i.e., a small percentage of the disturbance force, from the actuators to be effective for frequencies higher than the resonant frequency of the mount itself. The effectiveness of the proposed mounts for the machinery is demonstrated on the load transmissibility reduction at the foundation support (fixed end) due to disturbance from machinery above mounts. On the other hand, the vibration magnitude reduction of equipment above mounts due to disturbance from the foundation is used for evaluating the equipment isolation effectiveness. There is no stabilty or degradation problem when a number of the passive-active mounts are used on the same foundation. Furthermore, the more of this type of mounts used on a foundation the more effective the vibration suppression and the smaller actuator force requirement for each passive-active mount.
Micro-Dynamic Stiction Model and Control of a Hub-Appendage System
Authors: Hsieh Chen , Lin Jong-Ching
Published: February 2021

A hub-beam system driven by a DC torque motor is studied. The motor is mounted on two ordinary ball bearings. Therefore, static friction is significant in this system. Traditionally, in modeling a flexible structure system, people treat static friction as a force equal but opposite to the applied force. Furthermore, there is no displacement once the system is stuck by the static friction. With this dead zone type static friction concept, it is theoretically very hard to control the line of sight (L. O. S) of the flexible beam with very high precision due to the residue deviation of hub angle and small vibration that remain when the system is stuck by static friction.

However, based on a large amount of experimental results, more detail of static friction behavior has been revealed. It turns out that the static friction behavior can be summarized in several simple rules. A new static friction model that is described elsewhere is hence developed according to these rules. In this paper, this new friction model is applied to the hub beam system to describe the motion of the system during stiction phase. This micro dynamic stiction model is experimentally proved. It is shown that, after linearization, the stiction force is equivalent to a spring force with high stiffness together with a damping force. With the help of this new model, we successfully point the L. O. S. of the beam to the target with arc-second level precision.
Active Noise Control With the Active Muffler in Automotive Exhaust Systems
Authors: Oh Jae-Eung , Kim Heung Seob , Hong Jin Seok , Shin Joon , Song Jin Ho
Published: February 2021

This study experimentally demonstrates the use of an active muffler attached to an automotive exhaust system to reduce exhaust noise. For improving the signal to noise ratio in the process of estimating secondary path transfer functions, an on-line algorithm in which conventional inverse modeling is combined with an adaptive line enhancer is used as the control algorithm. The active muffler is designed so that the primary noise and the control sound are propagated as a plane wave in the outlet. Therefore, the error microphone could be placed outside the high temperature centers of the tail pipe, and the noise radiating to the outside could be reduced in the whole area around the outlet.

The control experiment for reducing exhaust noise with an active muffler is implemented during run-up at no load. Compared with the conventional off-line method, it can be seen from the experimental results presented the proposed online method is capable of acquiring a reduction of more than 5 dB of exhaust noise in overall sound power level.
Active Vibration Isolation Control for a Multi-Degree-of-Freedom Structure With Uncertainties of its Base
Authors: Nishimura Hidekazu , Kojima Akihito
Published: February 2021

This paper proposes a design method for an active vibration isolation controller for a multi-degree-of-freedom structure with uncertainties of its base. It is demonstrated that a controller which has a desired performance can be designed even if we don’t precisely know the base dynamics by using the criterion function for the purpose of suppression of the interaction between the controlled structure and its base. In order to minimize this interaction we select the acceleration of the lowest mass of the controlled structure and the relative displacement between the lowest mass and its upper mass as the controlled variables. By simulations and experiments it is verified that the designed controller improves both the control performances and the robust performance under the existence of the base dynamics with uncertainties.
Structural Vibration Control for Bridge Towers and its Effect Under Wind Excitation Using a Wind Tunnel
Authors: Doi Fumio , Seto Kazuto , Ren Mingzhang , Gatate Yuzi
Published: February 2021

In this paper we present an experimental investigation of active vibration control of a scaled bridge tower model under artificial wind excitation. The control scheme is designed on the basis of a reduced order model of the flexible structures using the LQ control theory, with a collocation of four laser displacement sensors and two hybrid electro-magnetic actuators. The experimental results in the wind tunnel show that both the bending and the twisting vibrations covering the first five modes of the structure are controlled well.
LMI Based Controller Design for a Bridge Tower Under Construction
Authors: Kar I. N. , Seto K. , Doi Fumio
Published: February 2021

This paper presents a simple method to design a robust controller for a bridge tower under construction using static state and output feedback. The parameter variations due to the constructional progress are considered to be system uncertainties and taken into account in the time of design. System uncertainties of the bridge tower are represented by a set of linear systems and each system corresponds to a particular stage of work. With in the framework of quadratic stabilization, controller which guaranteed a specified damping are obtained by solving a set of Linear Matrix Inequalities (LMI). Controller is shown to be robust with the changes of bridge tower by constructional progress through simulation studies.
Active Vibration Control of Bridge Tower Under Construction
Authors: Tamaki Toshihiro , Kagaya Hiroaki , Sakai Fujikazu , Ogawa Kazushi , Nishi Yoshikazu , Sasaki Masatoshi , Yamaguchi Kazunori
Published: February 2021

In large structures such as towers of suspension bridges or cable-stayed bridges, we often need to suppress the wind-induced vibration for their safety. Especially in the construction stage, the structures are more flexible than the completed ones. This paper discusses the active dampers used to suppress the wind-induced vibration of a tower of a suspension bridge (The Kurushima Bridge 3P Tower) during the construction. The active damper was used to suppress the wind-induced vibration in multiple modes predicted by wind-tunnel test. The controller design of the dampers is based on an H∞ robust control theory. At each erection step, we measured the dynamic properties of the towers to adjust the parameters of the controller using the active dampers as vibration exciters. The measured dynamic properties of the active controlled structures are compared with those of a non-controlled structure. The analysis of free vibration shows the suppression performance of active damper as expected in the controller design.
Fuzzy Logic Control of Time Periodic Mechanical Systems
Authors: Boghiu Dan , Sinha S. C. , Marghitu Dan B.
Published: February 2021

The fuzzy logic control of mechanical systems with periodic coefficients is considered. The controller design is illustrated through two examples, which include linear as well as nonlinear systems. For the linear case, a controller is designed such that a single inverted pendulum with a time periodic follower force is stabilized in the vertical position. As an example of the nonlinear system, the flap motion of a parametrically excited rotating elastic beam is considered. The controller is designed such that the deflection of the beam tip vanishes in a short period of time.
Computation of Nonlinear Response of Hydraulically Actuated Structures
Authors: Burton T. D. , Baker C. P. , Lew J. Y.
Published: February 2021

The maneuvering and motion control of large flexible structures are often performed hydraulically. The pressure dynamics of the hydraulic subsystem and the rigid body and vibrational dynamics of the structure are fully coupled. The hydraulic subsystem pressure dynamics are strongly nonlinear, with the servovalve opening x(t) providing a parametric excitation. The rigid body and/or flexible body motions may be nonlinear as well. In order to obtain accurate ODE models of the pressure dynamics, hydraulic fluid compressibility must generally be taken into account, and this results in system ODE models which can be very stiff (even if a low order Galerkin-vibration model is used). In addition, the dependence of the pressure derivatives on the square root of pressure results in a “faster than exponential” behavior as certain limiting pressure values are approached, and this may cause further problems in the numerics, including instability. The purpose of this paper is to present an efficient strategy for numerical simulation of the response of this type of system. The main results are the following: 1) If the system has no rigid body modes and is thus “self-centered,” that is, there exists an inherent stiffening effect which tends to push the motion to a stable static equilibrium, then linearized models of the pressure dynamics work well, even for relatively large pressure excursions. This result, enabling linear system theory to be used, appears of value for design and optimization work; 2) If the system possesses a rigid body mode and is thus “non-centered,” i.e., there is no stiffness element restraining rigid body motion, then typically linearization does not work. We have, however discovered an artifice which can be introduced into the ODE model to alleviate the stiffness/instability problems; 3) in some situations an incompressible model can be used effectively to simulate quasi-steady pressure fluctuations (with care!). In addition to the aforementioned simulation aspects, we will present comparisons of the theoretical behavior with experimental histories of pressures, rigid body motion, and vibrational motion measured for the Battelle dynamics/controls test bed system: a hydraulically actuated system consisting of a long flexible beam with end mass, mounted on a hub which is rotated hydraulically. The low order ODE models predict most aspects of behavior accurately.
Thickness-Optimization of Piezoceramic Transducers for Energy Transfer
Authors: Wolf Kai , Frese Stephan , Hagedorn Peter , Seemann Wolfgang
Published: February 2021

For the ultrasonic travelling wave motor, the energy-based definition of the electromechanical coupling factor (EMCF) is utilized to adapt the thickness of the piezoceramic layer, which is bonded to the stator of the motor, for maximal energy transfer. A Bernoulli-Euler model for the electromechanical field variables is used to derive the equations of motion and to determine the EMCF for a steady-state solution. The EMCF, depending on the thickness of the piezoceramic layer, is then maximized to optimize the sandwich structure for energy transmission. Results are compared with numerical simulations of the dynamical behavior, obtained by the ANSYS FE-code.
Dynamics of a Vibratory Feeder
Authors: Wolfsteiner Peter , Pfeiffer Friedrich
Published: February 2021

The most common devices used to feed small parts in an automatic assembly framework are vibratory feeders. They are used to store, feed, orientate and isolate the parts. Due to the complex mechanics of the feeding process the design of the feeders is still depending on trial and error. This paper presents a complete dynamical model of the transportation process including unilateral constraints and multiple impacts, both with coulomb friction. Some simulation results, computed with a three dimensional model, explain the practical benefit of the proposed tool.
Eigenstrain-Based Algorithm for Viscoelastic Uniaxial Wave Propagation due to Impact
Authors: Irschik Hans , Belyaev Alexander K. , Raschl Peter
Published: February 2021

A numerical algorithm for uni-axial inelastic wave propagation due to impact-type loading is presented. The algorithm is based on the linear-elastic multiple-field formulation, in which inelastic parts of strain are considered as eigenstrains acting upon a linear-elastic background structure. The solution thus can be consistently found by superposition of altogether elastic waves, where the fictitious eigenstrains are calculated from the inelastic constitutive equations by numerical integration. Due to the physical background of the method, the procedure turns out to be both, computationally accurate and numerically stable. In the present contribution, the algorithm is realized in C++ and applied to the loading-unloading problem of a semi-infinite rod of Maxwell material. The accuracy of the algorithm is demonstrated by comparing to an analytic solution which is derived in the form suitable for comparison.
Shell Transformations and Distributed Sensing/Control Characteristics
Authors: Taou H. S. , Bao Y. , Venkayya V. B. , Bahrami H.
Published: February 2021

Adaptive and controllable shapes and geometries of shells are desirable in many engineering applications, such as antenna dishes, rotor blades, airplane wings, nozzles, etc. In this paper, detailed sensing and control behavior of an adaptive shell panel are investigated. The shell panel changes its geometry from an open shallow shell (30°) to a deep cylindrical shell (150°). Natural frequencies, distributed sensing and damping control characteristics associated with the curvature changes are investigated. Mathematical modeling is presented first, followed by solution procedures. Membrane and bending contributions in sensing and control are evaluated. It is observed that natural frequencies of lower natural modes increase and those of higher modes decrease in the process of curvature transformation from 30° to 150°. Analytical solutions suggest that the membrane sensitivity becomes increasingly important when the curvature increases. The damping controllability of lower modes decreases as the shell curvature increases, however, that of higher modes still increases.
Gain-Scheduled Hyperplane Design for Sliding Mode Control via LMI
Authors: Sivrioglu Selim , Nonami Kenzo
Published: February 2021

This study is concerned with design of a sliding mode hyper-plane for a class of linear parameter-varying (LPV) plants whose state-space matrices are affine function of time-varying physical parameters. The proposed hyperplane involving linear matrix in-equality (LMI) approach has continuous dynamics due to scheduling parameters and provide stability and robustness against parametric uncertainties. We have designed gain-scheduled sliding mode hyperplane for a rotor-magnetic bearing system with gyroscopic effect which can be considered LPV plant due to parameter dependence to rotational speed. The obtained hyperplane is continuously scheduled with respect to rotational speed. We successfully carried out experiment using a commercial use turbo-molecular pump system and results were reasonable and good.
Nonlinear Modal Analysis of a Cracked Beam
Authors: Chati M. , Rand R. H. , Mukherjee S.
Published: February 2021

This paper addresses the problem of vibrations of a cracked beam. In general, the motion of such a beam can be very complex. This phenomenon can be attributed to the presence of the nonlinearity due to the opening and closing of cracks. The focus of this paper is the modal analysis of a cantilever beam with a transverse edge crack. The nonlinearity mentioned above has been modelled as a piecewise-linear system. In an attempt to define effective natural frequencies for this piecewise-linear system, the idea of a “bilinear frequency” is utilized. The bilinear frequency is obtained by computing the associated frequencies of each of the linear pieces of the piecewise-linear system. The finite element method is used to obtain the natural frequencies in each linear region.

In order to better understand the essential nonlinear dynamics of the cracked beam, a piecewise-linear two degree of freedom model is studied. Perturbation methods are used to obtain the nonlinear normal modes of vibration and the associated period of the motion. Results of this piecewise-linear model problem are shown to justify the definition of the bilinear frequency as the effective natural frequency. It is therefore expected that calculating piecewise mode shapes and bilinear frequencies is useful for understanding the dynamics of the infinite degree of freedom cracked beam.
Feed-Back Numerical Implementations of an Optimal Procedure for Chaos Control in a Two-Well Impact Oscillator
Authors: Lenci Stefano , Rega Giuseppe
Published: February 2021

The problem of controlling the chaotic dynamics of an inverted pendulum is addressed. Starting from the optimal excitation obtained in previous works, which gives satisfactory results but only on one side of the phase space, two different implementations have been developed in order to improve the controlled feature of the system.

The implementations consist in a shrewd alternation of one-side optimal and of harmonic excitation, and in an alternation of right and left optimal excitations. They are aimed at reducing the scattered nature of the response, which has been synthetized by the number of jumps between the two potential wells.

Some numerical simulations have been performed, showing the effectiveness of the proposed procedure. Furthermore, the comparison between the two cases has been discussed on both a local and a global basis.
Toward a Minimal Dynamic Model of a 6-DOF Parallel Robot
Authors: Beji L. , Pascal M. , Joli P.
Published: February 2021

In this paper, an architecture of a six degrees of freedom (dof) parallel robot and three limbs is described. The robot is called Space Manipulator (SM). In a first step, the inverse kinematic problem for the robot is solved in closed form solution. Further, we need to inverse only a 3 × 3 passive jacobian matrix to solve the direct kinematic problem. In a second step, the dynamic equations are derived by using the Lagrangian formalism where the coordinates are the passive and active joint coordinates. Based on geometrical properties of the robot, the equations of motion are derived in terms of only 9 coordinates related by 3 kinematic constraints. The computational cost of the obtained dynamic model is reduced by using a minimum set of base inertial parameters.
Experimental and Numerical Investigation of a Nonlinear Autoparametric System
Authors: Berlioz Alain , Dufour Régis , Sinha Subhash C.
Published: February 2021

Experimental and numerical investigations are carried out on an autoparametric system consisting of a composite pendulum attached to a harmonically base excited mass-spring subsystem. The dynamic behavior of such a mechanical system is governed by a set of coupled nonlinear equations with periodic parameters. Particular attention is paid to the dynamic behavior of the pendulum. The instability threshold of the pendulum is determined from the semi-trivial solution of the linearized equations. The set of nonlinear differential equations is then integrated with respect to time using step-by-step methods. The developed experimental setup makes it possible to analyze the angular displacement of the pendulum using an opto-electronic sensor. The motion of the pendulum is numerically analyzed via phase-plane portraits and Poincaré maps. A subcritical bifurcation is plotted and chaos is observed. The predicted results are experimentally validated.
Experimental Investigation of a Piezoelectrically Actuated Rotating Parts Feeder
Authors: Chang S. H. , Yang T. W.
Published: February 2021

The parts feeder provides both horizontal and vertical forces to transfer the small parts between stations in automated manufacturing processes. In this paper, the dynamic characteristics of a piezoelectrically actuated rotating parts feeder was evaluated. The model of the piezoelectric bimorph, the key component of the parts feeder, is formulated under DC and AC excitation. Experiments using laser interferometer, impedance analyzer and spectrum analyzer were conducted to measure displacement sensitivity, resonance frequencies and antiresonance frequencies of the electrical/mechanical system. Relations between driving frequencies and vibration amplitudes under various driving voltages were reported. From experimental results, the resonance frequencies of the mechanical system were identified at 176.6 Hz and 535 Hz. The first resonance and anti-resonance frequencies of the electrical system were found at 176.0 Hz and 177.5 Hz. The electromechanical coupling coefficient for piezoelectric actuator using Mason formula is 13%. Operating at the first resonance frequency, the parts feeder feeds at 17.66 mm/sec with a vertical vibration amplitude of 14.2 μ m.
Dynamics of Rotor/Bearing System With Flexible Rotor and Flexible Bearing Support
Authors: Muszynska Agnes , Petchenev Alex , Goldman Paul
Published: February 2021

The paper analyzes, theoretically and experimentally, the lowest four lateral modes of an isotropic rotor/fluid-lubricated bearing system with flexible rotor and flexible bearing support. The parameters of the analytical model of the system are identified using sweep-frequency modal testing of the rotor rig. A nonsynchronous, circular-rotating-force excitation was applied sequentially at the rotor and at the fluid-lubricated bearing casing, in order to generate the response data. The approach used in this study emphasizes the dynamic features of the system which are invariant to the choice of coordinate system.

The system is described using Dynamic Stiffness matrix. This provides an advantage of simplicity, allowing a comprehensive stability study for various system parameters.
Distributed Transfer Function Synthesis of Multi-Body Flexible Rotor Systems
Authors: Yang Bingen , Fang Houfei
Published: February 2021

A distributed transfer function synthesis is proposed for modeling and analysis of rotor systems assembled from multiple flexible and rigid components. The method is capable of treating non-self-adjoint effects, general boundary conditions and multi-body coupling, and delivers exact and closed-form analytical solutions for various problems. The proposed method is illustrated in two numerical examples.
Vibration Analysis of High Speed Stepped Thrust Gas Film Bearings With Inertia Effects
Authors: Ochiai Masayuki , Hashimoto Hiromu
Published: February 2021

Stepped thrust gas film bearings are widely used for high speed rotating machinery because of their simple structure, relatively high load carrying capacity and stability. In such bearings, the gas film inertia forces may play an important role under high speed conditions. In this paper, the vibration analysis of high speed, stepped thrust gas film bearings considering the inertia effects is described. In the numerical analysis, the static and dynamic pressure distributions in pocket and land regions are evaluated from the generalized Reynolds equation considering the centrifugal force. The pressure values at the step are calculated by considering the conservation of mechanical energy and the continuity of gas film flow in pocket and land regions. Moreover, the dynamic response of bearings subjected to impulsive and sinusoidal excitations are analyzed for different values of film thickness ratios. From the numerical results, the effects of gas film inertia on the vibration characteristics of bearings are clarified.
Suppression of Vibration in a Nonlinear Axially Moving String by the Boundary Control
Authors: Shahruz Shahram M.
Published: February 2021

In this note, a nonlinear axially moving string is considered. It is proved that the nonlinear string can be stabilized by the linear boundary control, which is the negative feedback of the transversal velocity of the string at one end.
Static and Dynamic Response of Plates With Curved Boundaries
Authors: Park Duk-Hyun , Yang Bingen
Published: February 2021

A semi-analytical method for analysis of flexible plates with curved boundaries is presented. Through an isoparametric transformation, the original spatial domain of the plate is mapped onto a rectangular region, where the strip distributed transfer functions of the plates are introduced. This transfer function formulation yields closed-form predictions of the displacement, stresses and eigensolutions of the plate. The accuracy and efficiency of the method is verified in numerical examples.
Spatial Modulation of Repeated Vibration Modes in Rotationally Periodic Structures
Authors: Kim Mintae , Moon Joonho , Wickert Jonathan A.
Published: February 2021

When a structure deviates from axisymmetry because of circumferentially varying model features, significant changes can occur to its natural frequencies and modes, particularly for the doublet modes that have non-zero nodal diameters and repeated natural frequencies in the limit of axisymmetry. Of technical interest are configurations in which inertia, dissipation, stiffness, or domain features are evenly distributed around the structure. Aside from the well-studied phenomenon of eigenvalue splitting, whereby the natural frequencies of certain doublets split into distinct values, modes of the axisymmetric structure that are precisely harmonic become contaminated by certain additional wavenumbers in the presence of periodically spaced model features. From analytical, numerical, and experimental perspectives, this paper investigates spatial modulation of the doublet modes, particularly those retaining repeated natural frequencies for which modulation is most acute. In some cases, modulation can be sufficiently severe that a mode shape will beat spatially as harmonics with commensurate wavenumbers combine, just as the superposition of time records having nearly equal frequencies leads to classic temporal beating. A straightforward algebraic relation and a graphical checkerboard diagram are discussed with a view towards predicting the wavenumbers present in modulated eigenfunctions given the number of nodal diameters in the base mode and the number of equally spaced model features.