bluuebunny/crossref_metadata_2025 huggingface dataset:
A Versatile Design Platform for a Walking Robot in Harsh Environments
Authors: Lupien Simon , Lessard Patrick , Demers Jean-Christophe , Lambert Guillaume , Bigras Pascal , Sankar Thiagas S.
Published: November 2020

In a previous paper [1] on the design of Capra — a quadruped robot with improved agility, we had presented the main design avenues that were to be considered for the development of an agile mobile walking robot, Capra. The objective of achieving full and autonomous robot agility in harsh environments has always been predominant in our research program on robot design for improved capabilities and applications potential. In this follow-up paper, we report the design results to meet another level of objectives that we had previously determined and currently are incorporating in the Capra hierarchy. Systematic design methodologies that were developed for the robotic machine structure also enable one to consider the Capra robot as not only an agile walking-machine but also as a versatile design platform. It can be deployed for retrofit in many automation applications or for specific uses in harsh environments involving critical design constraints. This design approach has resulted in the development and integration of many of Capra’s fundamental sub-systems by means of a range of modules and prototypes. This paper addresses all the different design issues involved in the development of a versatile design platform for a truly mobile robot. The design methodologies to support the various capabilities are presented here as independent systems, which can be fitted, integrated and retrofitted for any mobile robot configuration. Several design results are presented as examples of the design process.
Incorporating Lifecycle Costs Into Product Architecture Decisions
Authors: Dahmus Jeffrey B. , Otto Kevin N.
Published: November 2020

The partitioning of a product into modules has a large impact on the design and manufacture of a product. It also has a large impact on lifecycle concerns such as repair and service. Previous work has developed product architecting rules using function structures to partition a product into modules. Straight application of these rules determines maximal modules. Often, however, subsets of these modules have varying failure rates, handling difficulties, and part costs. We develop here equations to incorporate these serviceability concerns into the architecting process. The service cost of any candidate module must incorporate part costs, labor costs, and failure rates. With this information, comparative service costs can be calculated for different modularization schemes. Examples are shown from document systems.
Comparison of Combined Embodiment Design and Control Optimization Strategies Using Optimality Conditions
Authors: Reyer Julie A. , Fathy Hosam K. , Papalambros Panos Y. , Ulsoy A. Galip
Published: November 2020

Optimal embodiment design and control systems can be solved using several different strategies. This paper considers whether those strategies will find the true system optimum.

Optimality conditions determine whether a point is an optimum of a system. This paper presents a development and comparison of the optimality conditions for several methods of optimizing fully coupled embodiment design and control systems. The results demonstrate that the methods do not possess the same optimality conditions and therefore will not converge to the same optimal solutions, often leading to sub-optimal solutions. Since these strategies have been used successfully to solve various examples, criteria are developed to determine when the various methods will find the true system optimum.
A Decision-Support Design Tool for Thermoplastic Feature Design for Dimensional Stability
Authors: Patrick Jeff , Stauffer Larry A.
Published: November 2020

We present a decision-support tool that will assist engineers with the design of thermoplastic parts for improved dimensional stability. The tool addresses performance issues that cause significant deformation of the plastic part during its life cycle and thus changes in critical dimensions. The degradation of dimensional stability has a direct influence on the quality of the part and its cost is estimated by applying the Taguchi Loss Function. In this way, the quality cost can be combined with the manufactured cost of the part for a total part cost. The tool helps estimate these manufacturing and quality costs early in the product-development process where changes can be made relatively easily. In this paper we present the design analysis process of the tool, a description of the software, and a case study of its use in an industrial application.
Spatial Mechanism Design in Virtual Reality With Networking
Authors: Kihonge John N. , Vance Judy M. , Larochelle Pierre M.
Published: November 2020

Mechanisms are used in many devices to move a rigid body through a finite sequence of prescribed locations in space. The most commonly used mechanisms are four-bar planar mechanisms that move an object in one plane in space. Spatial mechanisms allow motion in three-dimensions (3D). Spatial 4C mechanisms are two degree of freedom kinematic closed-chains consisting of four rigid links simply connected in series by cylindrical (C) joints. A cylindrical joint is a two degree of freedom joint which allows translation along and rotation about a line in space. This paper describes a synthesis process for the design of 4C spatial mechanisms in a virtual environment. Virtual reality allows the user to view and interact with digital models in a more intuitive way than using the traditional human-computer interface (HCI). The software developed as part of this research also allows multiple users to network and share the designed mechanism. Networking tools have the potential to greatly enhance communication between members of the design team at different industrial sites and therefore reduce design costs.
Aesthetic Design of Machine Systems Using Evaluation Maps
Authors: Yoshimura Masataka , Horie Satoshi
Published: November 2020

The benefits of including aesthetic factors in the design of mechanical systems have been receiving increasing attention and study. Designs that successfully incorporate aesthetic considerations are more likely to create positive impressions in users, while offering increased usability and improved ergonomics. However, mechanical system design methods that successfully integrate the simultaneous evaluation of aesthetic factors with other parameters are not yet widely used. This paper presents a total design method that specifically includes aesthetic factors in the design process. The proposed method consists of three parts: (1) the analysis of the aesthetic factors; (2) the analysis of other factors (e.g. cost, function, mechanical characteristics, and so on); and (3) the evaluation of the overall system, using evaluation maps that include all system information. The use of evaluation maps allows other mechanical system factors to be treated concurrently with those of aesthetic importance. This method is applied to the design of a service robot that will offer a cup of beverage to a person.
Comprehensive Satisfactory Design Method for Product Designs
Authors: Adachi Eiji
Published: November 2020

Actual product designs aim to fulfill all product requirements of market needs and wants, which are technical or non-technical, logical or illogical, objective or subjective, and quantitative or qualitative. The actual product designs are objective-aiming designs and can be supposed to be multi-objective satisfactory designs with heterogeneous objective functions and dimensional design variables. To realize computer-aided product designs which can obtain rational and satisfactory solutions, we classify the objective functions and contrive methods to deal with non-theoretical, non-technical, subjective, or illogical objective functions as well. This paper shows all of our methods, including an expression of heterogeneous objective functions which consists of objective and evaluated values, a satisfactory design method by simultaneous equations which searches solutions sequentially, identification methods of non-theoretical or non-technical objective functions and sensitivity coefficients for the simultaneous equations, a decision-making method of promising solutions to fulfill product requirements, and also numerical applications of these methods to actual product designs.
Incorporating Manufacturing Cycle Time Cost in New Product Development
Authors: Chincholkar Mandar M. , Herrmann Jeffrey W.
Published: November 2020

Manufacturing cycle time (the time that elapses from work order release to completion) affects the cost of developing and manufacturing a product. However, most cost models consider only the setup and processing times and ignore the move times and queue times, which form most of the manufacturing cycle time. This paper discusses the economic impact of manufacturing cycle time. It presents methods for estimating the manufacturing cycle time of a new product that will be made in a manufacturing system that makes other products as well. It identifies the benefits of reducing manufacturing cycle time and shows how those benefits yield increased profitability.
High Production Manufacturing Considerations for Metallic Compliant Mechanisms With Long Thin Beams
Authors: Herring Aaron , Magleby Spencer , Howell Larry , Todd Robert
Published: November 2020

The long thin beams commonly used in compliant mechanisms (CMs) present a challenge when manufacturing metallic CMs at high production rates. This paper discusses the difficulty of forming one-piece metallic CMs at high production rates. This is followed by a discussion of possible joining methods for assembling these mechanisms, and a selection criteria for choosing between various joining methods. This is followed by several examples of how to implement the selection criteria. Finally a list of manufacturing process choices and design factors is given, and the conclusions from the research are outlined.
Understanding Perceptual Gaps in Integrated Product Development Teams
Authors: Cagan Jonathan , Vogel Craig M. , Weingart Laurie R.
Published: November 2020

An in-depth study identifying perceptual gaps between diverse disciplines within a product development process is presented. The gaps have profound impact on the design process, identifying differing goals and leading to unhealthy conflict in the process.
Evolving a Functional Basis for Engineering Design
Authors: Hirtz Julie M. , Stone Robert B. , McAdams Daniel A. , Szykman Simon , Wood Kristin L.
Published: November 2020

All products and artifacts are designed for a purpose. There is some intended reason behind their existence: the product or artifact function. Functional modeling provides an abstract, yet direct, method for understanding and representing an overall product or artifact function. Function modeling also provides a strategy for problem decomposition, physical modeling, product architecting, concept generation, and team organization. A formal function representation is needed to support function modeling, and a standardized set function-related terminology is necessary to achieve repeatable and meaningful results from such a representation. We refer to this representation as a functional basis; in this paper, we seek to reconcile and integrate two independent research efforts into a significantly evolved functional basis. These efforts include research from the National Institute of Standards and Technology (NIST) and two U.S. universities, and their industrial partners. The overall approach for integrating the functional representations is developed, in addition to the final results. The integration process is discussed relative to differences, similarities, insights into the representations, and product validation. Based on the results, a more versatile and comprehensive design vocabulary is obtained. This vocabulary will greatly enhance and expand the frontiers of research in design repositories, product architecture, design synthesis, and general product modeling.
Affordance: The Fundamental Concept in Engineering Design
Authors: Maier Jonathan R. A. , Fadel Georges M.
Published: November 2020

In an effort to ground the art and practice of design, especially engineering design, in a formal science, there is a need to identify the core, fundamental concepts on which such a science should be based. Popular engineering design guides have long emphasized the importance of function as a fundamental concept. In this paper we argue that another concept, that of affordance, a term coined by the perceptual psychologist James J. Gibson to describe how animals perceive objects in their environment, is a more fundamental and in fact more powerful concept than function. Accepting affordance as a fundamental concept in design leads to a novel view of the design process, in which the designer’s task is to find a system that possesses specific desired affordances, but does not possess other, undesired affordances. The concept of affordance also lends a unifying framework to a variety of disparate approaches to design, while suggesting new metrics and methods of decomposition to the design process in general.
Closest–to–Desired Methods of Multi-Objective Optimization: Some Comments and Questions
Authors: Lin JiGuan G.
Published: November 2020

The intent of this paper is to:

1. Classify various multi-objective optimization methods that are based on trying to attain certain desired values.

2. Make some critical comments on each class as a whole, and illustrate by simple graphically visualizable examples the potential problems or drawbacks pertinent to the general nature of each class.

3. Make some questions that could possibly “provoke” some further investigation.

As a result, the relative advantages and disadvantages of each class of these methods become apparent.
The Development and Adoption of VIDEEO (Virtual Development Enterprise for Europe) in European Wide Product Development Projects
Authors: Thomson A. I. , Ion W. J. , Temple B. K. , Allan M. , Kemohan N. , Davidson S.
Published: November 2020

VIDEEO which is an acronym of VIrtual Development Enterprise for EurOpe is a web-based environment which supports both students and tutors in the creation and execution of multidisciplinary, distributed, product development projects. One of the main aims of VIDEEO is to provide a teaching and learning environment which provides an appropriate balance between technical and vocational study. The VIDEEO project was funded by SOCRATES and was completed by a team of partners from eight european institutions. The objective of this paper is to provide an overview of the lifecycle of the VIDEEO project from development through to evaluation and usage.
Global Engineering Design Team (GEDT): A Business View on Structuring Undergraduate Projects
Authors: Baxter Jim , Henderson Mark , Barnes Cathy , Bourdo Tom , de Pennington Alan , Wells Valana
Published: November 2020

The Global Engineering Design Team (GEDT) is an experience sponsored by University of Leeds and Arizona State University to give qualified undergraduates an international non-collocated design team assignment. This is the third year of the programme and in this document, it is examined with respect to the 9 areas of the European Foundation for Quality Management’s (EFQM) Business Excellence Model (BEM), a framework commonly used in business self-evaluation in the UK. The 9 areas reviewed are: leadership, policy and strategy, people, partnerships and resources, processes, people results, customer results, society results and key performance results. The overall evaluation shows how the GEDT has made strides in all 9 areas, yet still needs some specific improvements for effectiveness in the future.
Web-Based Collaborative Product Design Review in Extended Enterprises
Authors: Huang G. Q. , Shen J. Y. , Mak K. L.
Published: November 2020

This paper reports on the development of a web-based framework supporting collaborative product design review between partners in the extended enterprise. On the one hand, the product design team can use the system to upload all the relevant design documents onto the web site. On the other hand, the design review committee members can use the system to download the subject product design, and organize and conduct the design review sessions. Individual members can continuously submit their comments and suggestions about a design. Review meetings can be arranged for the members to simultaneously collate and discuss individual opinions. A common workspace is shared among the members with the support of a VRML (Virtual Reality Modelling Language) 3D display of the product. Such a web-based design review framework is expected to greatly improve the effectiveness and efficiency of the design review process.
A Wavelet-Logarithmic Decrement to Identify Damping in MDOF Systems: Theory and Applications
Authors: Lamarque C. H. , Pernot S.
Published: November 2020

A wavelet-based formula similar to the logarithmic decrement formula is introduced to estimate damping in multi-degree-of-freedom systems from time-domain responses. The new formula is then validated upon both numerical and in-situ experiments.
A Component Mode Synthesis Look at Planar Beam Elements
Authors: Meijaard J. P. , Schwab A. L.
Published: November 2020

This paper deals with the improvement in efficiency of simulations in flexible multibody system dynamics. On the basis of concepts from component mode synthesis techniques some improved elements for planar beams which are hinged at one or both ends are developed. These elements show a considerable increase in accuracy, or alternatively allow a reduction of the number of elements, with respect to a standard element with cubic polynomial interpolation. The use of the elements is demonstrated in two examples: a planar slider-crank mechanism with a flexible connecting rod and a cantilevered beam in a spin-up motion.
Modeling of Overactuated Closed-Loop Mechanisms With Singularities: Simulation and Control
Authors: Ganovski Latchezar L. , Fisette Paul , Samin Jean-Claude
Published: November 2020

The modeling and control of redundantly actuated closed-loop mechanical systems is considered in the present work an illustrated with a planar four-bar mechanism and a 3-D parallel manipulator. A specific trajectory involving singular configurations is generated and then followed using the overactuation. To generate the trajectory, four-degree polynomial functions are considered. The loop constraint equations are solved by means of the Newton-Raphson numerical algorithm. In order to describe the dynamics of the systems, the Lagrange multiplier technique is used. The multipliers are eliminated via the coordinate partitioning method. To overcome the underdetermined state of the system induced by the overactuation, additional equations that represent a specific condition for smoothly passing through the singularities are applied. Further, to control the redundantly actuated mechanisms a feed-forward controller is chosen. The robustness of the controller is investigated through several cases of simulation including random noise applied to the controller input and instantaneous loading.
Motion and Vibration Analysis of a Roller Coaster
Authors: Fujita Katsuhisa , Kimura Tetsuya , Yamamoto Yoshinori
Published: November 2020

Motion and vibration analysis of a roller coaster running in a 3D trajectory is carried out. The equation of motion of the roller coaster is derived in which the restriction in the trajectory is dealt with by using differential-algebraic equations (DAE) method. The effects of a parameter variation of the roller coaster to the vibration of the passenger are investigated in simulation analysis. The simulation result shows that when the parameter associated with the stiffness of the wheels of the roller coaster decreases, the passenger’s vibration increased. In addition, it shows that the discontinuity of the rate of increment of the trajectory induces large vibration.
Power Demand of Actively Controlled Multibody Systems
Authors: Schiehlen Werner O. , Guse Nils
Published: November 2020

Flexible manufacturing systems are characterized by machines and mechanisms with some or all mechanical degrees of freedom actively controlled resulting in the prescribed motion necessary for the production process or rheonomic constraints, respectively. Due to the high nonlinearity of large displacement motions inverse dynamics is a standard control concept well established in manufacturing, robotics and walking machines. It is shown that inverse dynamics results in high energy consumption and requires large power supply. For autonomous robots and walking machines the power supply adds to the weight, and additional weight needs more power again. Finally, actively controlled walking machines are very heavy devices not comparable to the light weight design of passive walking mechanisms. It is proposed to use local energy storage by springs to overcome the drawback of inverse dynamics. The design principles for reduced energy consumption are outlined with simple mechanical models and include nonlinear characteristics of the springs, too, to improve further the local energy storage capacity.
Modeling Controlled Articulated Flexible Systems Using Assumed Modes: Part II — Numerical Investigation
Authors: Mordfin Theodore G. , Tadikonda Sivakumar S. K.
Published: November 2020

Guidelines are sought for generating component body models for use in controlled, articulated, flexible multibody dynamics system simulations. In support of this effort, exact truth models and linearized large-articulation models are developed in a companion paper. The purpose of the truth models is to aid in evaluating the use of various types of component body assumed modes in the large-articulation models. The assumed mode models are analytically evaluated from the perspectives of both structural dynamics and multibody dynamics. In this paper, component body assumed modes are tested in a linearized large-articulation model. The numerical behavior of the model and its performance in the presence of parameter variation is investigated and explained. The results show that high accuracy, high simulation efficiency, and numerical robustness cannot be simultaneously achieved. However, in many cases, satisfactory levels of all three are achievable. Guidelines are proposed for modeling the flexible bodies in controlled-articulation flexible multibody dynamic systems.
Inverse Dynamics of Musculo-Skeletal Systems Using an Efficient Min/Max Muscle Recruitment Model
Authors: Damsgaard Michael , Rasmussen John , Christensen Søren T.
Published: November 2020

This paper presents an efficient criterion for solving the redundancy of the muscle recruitment problem in inverse dynamics of musculo-skeletal systems. It is a minimum fatigue criterion that is formulated as a min/max optimization problem. The criterion is briefly reviewed in comparison to other criteria and its implementation for large and complex system, such as the human body, is explained in detail. The optimization problem is solved numerically by means of linear programming, providing a very efficient, final algorithm. It is shown that special care must be taken of systems with groups of sub-maximally loaded muscles and methods to deal with this automatically are presented. The algorithms are implemented into a software system called AnyBody, and examples involving up to 100 muscles are demonstrated. Even models of this size are solved in fractions of a second for a single time step on a standard PC.
Parametric Identification and Fault Detection in Vehicle Models With Nonlinear Suspension
Authors: Metallidis P. , Verros G. , Natsiavas S. , Papadimitriou C.
Published: November 2020

Systematic methodologies are applied for performing parametric identification and fault detection in nonlinear vehicle systems. The dynamic response of the vehicle models examined is caused by road excitation. In these models, the nonlinearities arise due to the function of the suspension dampers, which assume a different damping coefficient in tension and in compression. This leads to oscillator models with parameter discontinuities. First, emphasis is put on investigating some issues of fundamental importance, by employing a classical two degree of freedom quarter-car model. Since the dominant nonlinearities are due to switches between constant damping coefficients, appropriate methodologies are applied for obtaining exact motions of these models. Moreover, a statistically based methodology is applied for parametric identification and fault detection in vehicle suspensions with nonlinear characteristics, using dynamic test data. This methodology is then extended and applied to more involved and complete vehicle models. The numerical results presented demonstrate that this methodology provides an effective and practical way of detecting the type, location and severity of faults in vehicle suspensions.
Periodic Solutions of an Inhomogeneous Second Order Equation With Time-Dependent Damping Coefficient
Authors: Hartono  , van der Burgh A. H. P.
Published: November 2020

In this paper we will study the periodic solutions of an inhomogeneous second order equation with time-dependent damping coefficient:(1)x..+(c+ϵcos⁡2t)x.+(m2+α)x+Acos⁡ωt=0 where c, α, ϵ, A are small parameters and m, ω positive integers. Physically, the phenomenon of a time-dependent damping coefficient can occur in a special electrical circuit (RLC-circuit), or in a model equation for the study of rain-wind induced vibrations of a special oscillator. Because of the presence of a number of small parameters in equation (3) we will use the averaging method (up to third order) for the construction of approximations for the periodic solutions. The parameters c, α and A are considered to be small implying that they are expressed in the characteristic small parameter ϵ of the problem:(2)c=ϵc1+ϵ2c2+ϵ3c3,α=ϵα1+ϵ2α2+ϵ3α3,A=ϵA1+ϵ2A2+ϵ3A3, where ci, αi and Ai, i = 1, 2, 3 are of O(1).

For m, ω ∈ {1, 2, 3}, it will be shown that an O(1)-periodic solution exists if m = ω and if m ≠ ω the periodic solution is of order ϵ. Further, if c = O(ϵ), α = O(ϵ), and A = O(ϵ), for m = ω = 1 both stable and unstable periodic solutions exist but for m = ω = 2, 3 only stable periodic solutions are found. For the case that c = O(ϵ2), α = O(ϵ2), and A = O(ϵ2), for m = ω = 2, 3 only stable periodic solutions are found. But for m = 3 and α = (g/64)ϵ2 + O(ϵ3), c = O(ϵ3), A = O(ϵ3) both stable and unstable periodic solution exist. The stability of the periodic solutions follows from a new stability diagram related to equation (3) with A ≡ 0.
Generalized Harmonic Oscillators: Velocity Dependent Frequencies
Authors: Mickens Ronald E.
Published: November 2020

Preliminary results are given on a new class of nonlinear oscillator equations that generalize those of the usual linear harmonic case. These equations take the form ẋ = f(x)y and ẏ = −g(y)x, where f(x) and g(y) are continuous with first derivatives, and f(0) > 0, g(0) > 0. Of interest is the fact that these equations have a first-integral, i.e., there exists a function H(x,y) such that along a particular trajectory in the (x,y) phase space, H(x,y) = constant. We work out several general results related to this system of equations and illustrate them with several special cases that correspond to models of physical systems.

The work reported here was supported in part by research grants from DOE and the MBRS-SCORE Program at Clark Atlanta University.
Nonlinear Adaptive Vibration Absorber for the Control of Plate Vibrations
Authors: Ashour Osama N. , Nayfeh Ali H.
Published: November 2020

A nonlinear adaptive vibration absorber to control the vibrations of flexible structures is investigated. The absorber is based on the saturation phenomenon associated with dynamical systems possessing quadratic nonlinearities and a two-to-one internal resonance. The technique is implemented by coupling a second-order controller with the structure’s response through a sensor and an actuator. Energy is exchanged between the structure and the controller and, near resonance, the structure’s response saturates to a small value.

Experimental results are presented for the control of a rectangular plate and a cantilever beam using piezoelectric ceramics and magnetostrictive alloys as actuators. The control technique is implemented using a digital signal processing board and a modeling software.

The control strategy is made adaptive by incorporating an efficient frequency-measurement technique. This is validated by successfully testing the control strategy for a non-conventional problem, where nonlinear effects hinder the application of the nonadaptive controller.
Confinement and Suppression of Structural Vibrations
Authors: Choura Slim , Yigit Ahmet S.
Published: November 2020

A feedback strategy, aiming at confining and suppressing simultaneously the vibratory motion in flexible structures, is proposed. It is assumed that the structure consists of parts that are sensitive to vibration. The proposed strategy makes use of control inputs whose number is less than or equal to that of the dimension of the discretized model. The design objective is to devise a feedback scheme that leads to transferring the vibrational energy from the sensitive parts to the remaining parts of the structure. In order to keep away from the build-up of transferred energy in the nonsensitive parts, the feedback scheme considers, along with the confinement, the suppression of vibration in both the sensitive and non-sensitive parts. The proposed strategy also accounts for the presence of persistent excitations. A finite element model of a cantilever beam is used to show the viability of the proposed strategy.
Active Control of Radiated Sound From a Vibrating Plate
Authors: Hong Jin-Seok , Shin Kihong , Lee Choong-Hwi , Oh Jae-Eung
Published: November 2020

In this paper, an experimental study is described for active control of radiation sound from a vibrating plate under a harmonic excitation at a specific point. Two piezoceramic actuators are used to provide control inputs to the structure. The notion of control sensitivity of the plate bending moment is introduced to find the locations of piezoceramic actuators. Each piezoceramic actuator is located at the position that has the largest control sensitivity in order to maximize the control performance. The measurement sensors are two accelerometers whose outputs are processed through an array of linear filters. The impulse response of each filter is constructed from the vibro-acoustic path transfer function by accelerometers and microphones. The active structural acoustic control system is designed to estimate and reduce the radiated sound pressure on the basis of this transfer function. A 2 by 2 Filtered-x LMS algorithm is used, and is implemented on a TMS320C30 DSP board for the real-time control.
Nonlinear Behavior of Piezo-Beam-Systems Subjected to Weak Electric Field
Authors: von Wagner Utz , Hagedorn Peter , Nguyen Minh Nam
Published: November 2020

Experimental studies of piezo-beam systems subjected to weak harmonic electric fields have revealed typical nonlinear effects, e.g. dependence of the resonance frequency on the amplitude, superharmonics in spectra and a nonlinear relationship between excitation voltage and vibration amplitude. In contrast to the well-known nonlinear effects for piezoceramics in presence of strong electric fields, these effects have not been widely described in the literature.

In this paper we attempt a description of these phenomena by nonlinear constitutive relations, in particular by a non-constant elastic modulus Ec and piezoelectric factor d31. The equations of motion for the system under consideration are derived via the Ritz-method using Hamilton’s principle. The ‘nonlinear’ parameters are determined and the numerical results are compared to those obtained experimentally. The effects described herein may have a significant influence whenever structures are excited close to resonance frequencies via piezo-electric elements.
Shape Control of Timoshenko Beams by Shear-Based Piezoelectric Actuation
Authors: Krommer Michael , Irschik Hans
Published: November 2020

The present paper is concerned with the dynamic shape control of force loaded beams by means of the converse piezoelectric effect. We consider smart beams composed of substrate layers bonded to piezoelastic actuation layers with shaped electrodes at both sides. Piezoelastic extension actuators as well as piezoelastic shear actuators are used. We study transient disturbances produced by assigned forces, and we seek for a transient piezoelastic actuation which, when superimposed upon the assigned forces, leads to zero total displacements and cross-sectional rotations of the beams under consideration. In the following, a solution of this dynamic shape-control problem is presented which is exact within the framework of the Timoshenko theory of beams. The required shape-functions of the electrodes for eliminating the dynamic deformations due to the assigned forces are shown to be the quasi-static bending moment and shear force distributions due to the same assigned forces. When the assigned forces have a fixed space-wise distribution with a time-varying intensity, this solution can be easily realized and is felt to be appealing for practical purposes. We furthermore identify nilpotent shape functions, which may be added to the former solutions of the shape control problem without violating their validity.
A Comparative Study on Dynamic Wheel Loads of Multi-Axle Vehicle and Bridge Responses
Authors: Kim Chul Woo , Kawatani Mitsuo
Published: November 2020

To investigate relations between dynamic wheel loads of multi-axle vehicles on highway bridges and dynamic responses of bridge due to the vehicular loading, a three-dimensional dynamic analysis is carried out. Simultaneous differential equations for a coupling vibration of bridge and moving vehicle including roadway roughness are derived by means of modal analysis. The analytical wheel loads of vehicle model and responses of bridges are compared with experimental ones, to verify a validity of presented analytical procedure. Parametric investigations show that there exists resemblance between bounce motion of vehicle and bridge response. It can also be seen that the RMS based dynamic factor of dynamic wheel load can give an important information to predict the variation of impact factor of bridge due to speed condition as well as speed parameter.
Experimental Response of a Preloaded Vibro-Impacting Hertzian Contact
Authors: Rigaud Emmanuel , Perret-Liaudet Joël
Published: November 2020

This paper concerns the non-linear dynamic response of a vibro-impacting Hertzian contact. Sinusoidal and random external normal forces are considered. We focus on the primary resonance and include vibro-impact responses in order to analyze the main characteristics of the system associated to both Hertzian and contact loss non-linearities. Under very small input amplitude, contact exhibits an almost linear resonance. Linearized resonance frequency and damping ratio are identified. Increasing the external input amplitude, the softening behaviour induced by Hertzian nonlinear stiffness is clearly demonstrated for both sinusoidal and random inputs. For higher input amplitude, system exhibits vibro-impacts. The contact loss non-linearity strongly governs the dynamic behaviour of the system.
Measurement and Analysis of Modulated Doublet Mode Response in Mock Bladed Disks
Authors: Chang J. Y. , Wickert J. A.
Published: November 2020

The steady-state response of spatially modulated doublet modes that occur in low count flexible bladed disks is investigated for the case in which the structure is driven by a harmonic traveling wave excitation source. Finite element simulation and modal testing of prototypical bladed disk structures demonstrate the presence of particular wavenumbers, beyond the base number of nodal diameters, which contaminate and distort the appearance of certain doublet modes. The manner in which the natural frequency and wavenumber content of such modes shift and split as functions of the number of blades and their span angle is discussed in the light of a companion perturbation analysis for rotationally periodic structures. Resonance conditions are established and verified through simultaneous measurements made with a spin test stand using sensors that are placed in the rotating (structure) and stationary (excitation) frames of reference. The traveling wave response components of a repeated frequency doublet mode are shown to propagate either in the same or opposite direction as the excitation source, depending on whether certain algebraic relationships between the excitation order, the base number of nodal diameters, and the contamination wavenumbers are satisfied. To the extent that such components can travel at different phase speeds and directions relative to one another, the placement of sensors on the structure can be optimized to best measure the response amplitude. Conversely, other placements can result in sub-maximal measurement of peak vibration amplitude over the structure.
Stability of Interrupted Cutting by Temporal Finite Element Analysis
Authors: Bayly P. V. , Halley J. E. , Mann B. P. , Davies M. A.
Published: November 2020

Chatter in milling and other interrupted cutting operations occurs at different combinations of speed and depth of cut from chatter in continuous cutting. Prediction of stability in interrupted cutting is complicated by two facts: (1) the equation of motion when cutting is not the same as the equation when the tool is free; (2) no exact analytical solution is known when the tool is in the cut. These problems are overcome by matching the free response with an approximate solution that is valid while the tool is cutting. This approximate solution is obtained by the application of finite elements in time. The complete, combined solution is cast in the form of a discrete map that relates position and velocity at the beginning and end of each element to the corresponding values one period earlier. The eigenvalues of the linearized map are used to determine stability. Predictions of stability are confirmed by experiment.
Nonlinear Dynamics of the Woodpecker Toy
Authors: Leine Remco I. , Glocker Christoph , van Campen Dick H.
Published: November 2020

This paper studies bifurcations in systems with impact and friction, modeled with a rigid multibody approach. Knowledge from the field of Nonlinear Dynamics is therefore combined with theory from the field of Nonsmooth Mechanics. The nonlinear dynamics is studied of a commercial wooden toy. The toy shows complex dynamical behaviour but can be studied with a one-dimensional map, which allows for a thorough analysis of the bifurcations.
Chaotic Motion in the Vicinity of Separatrix of a Parametrically Driven Duffing Oscillator With a Twin-Well Potential
Authors: Luo Albert C. J.
Published: November 2020

The conditions for the (M:1) and (2M:1) resonances inside and outside of the separatrix of the parametrically driven Duffing oscillator are determined. The onset of such resonance in the vicinity of separatrix is investigated analytically and numerically. The results presented in this article can be applied to the post-buckled structures under parametric excitations.
New Approach of Wavelet Fractal Analysis to Mechanical Fault Diagnosis
Authors: He Zhengjia , Zi Yanyang , Chen Peng , Toyota Toshio
Published: November 2020

Wavelet transform decomposes signals in both time and frequency domains. According to the principle of multi-resolution, irregularities or complexities of decomposed signals in various frequency bands are different, which can indicate mechanical fault. Fractal dimension of decomposed signal is an excellent factor to express the irregularity or complexity. It can make features of mechanical faults remarkable. Based on wavelet fractal dimension, successful diagnosis of looseness fault of bearing bridge for 50MW turbo-generator was obtained.
Can Wavelet Transforms Used for Data Compression Equally Suitable for the Use of Machine Fault Diagnosis?
Authors: Tse Peter W. , He Ling S.
Published: November 2020

Wavelet transforms are capable of separating the raw vibro-acoustic signals into different frequency and time bands. They have exhibited potentials in the detection of fault related impulsive signals by using their multi-resolution time-frequency analyses. To ensure the design of wavelet transforms is simple and the processing is not time intensive, discrete type of wavelet transforms (DWTs) become popular as they are composed of low-pass and high-pass digital filters only, making them easier to implement and processing faster. Recently, a number of publications have applied the similar type of DWTs commonly used for data compression (dyadic type of DWTs) in vibration based machine fault diagnosis. However, the results are not satisfactory. The main reasons are the poor resolution provided by DWTs and the inappropriate design of digital filters causing undesirable frequency aliasings. Without taking care of these problems, they may lead to false alarms in fault diagnosis. In this paper, we present a new family of DWTs, which mainly consists of a series of Butterworth filter banks. They are capable of providing sufficient resolutions in different time and frequency ranges, and minimizing the effect of frequency aliasing. The results have shown that the new types of DWTs are promising in solving the problems and tailor-made for machine fault diagnosis. With the help of the new DWTs, the faults that exhibit non-linear and non-stationary signals can be detected easier and the diagnosis becomes more reliable.
Web and Virtual Instrument Based Machine Remote Sensing, Monitoring and Fault Diagnostic System
Authors: Tse Peter W. , He Ling S.
Published: November 2020

Failure of equipment not only leads to loss of production, but also, in some serious situations, causes human casualty. Hence, the need of equipment condition monitoring becomes crucial for reliable operations. Since expensive hardware instruments are needed for condition monitoring, with the current powerful PCs, software based virtual instruments are possible to replace hardware instruments. However, the software must be maintained for each PC, and a technician must still visit the site of the PC and its monitored equipment. By connecting the PC to the Internet, remote sensing and equipment fault diagnosing are possible. As only one copy of software for each type of virtual instrument is required on the server, the maintenance of virtual instrument is much easier and substantial cost of hardware instruments is reduced. Moreover, remote collaborative maintenance becomes feasible as worldwide experts can provide just-in-time advice to technicians via the Web. With the new standards of IEEE 1451.2 for smart transducers, the new sensors are self-Web-ready. Sensor manufacturers, such as Hewlett Packard and Bruel & Kjaer, have proclaimed their next generation sensors are self-Web-ready. Therefore, the development of a Web-based maintenance is a must in the near future. This paper presents the design and development of a solution and a platform for the Web-based remote collaborative diagnosis and maintenance. It consists of remote data sensing and logging, signal analysis using virtual instruments, and intelligent fault diagnosis and prognosis.
Reducing Friction Forces by Means of Applied Vibration
Authors: Bucher Izhak , Wertheim Oded
Published: November 2020

It has been observed that inducing vibration into structures can reduce the friction force between two sliding objects. This phenomenon has been used in positioning systems and recently was investigated in relation to various machining processes. The present paper brings an experimental work where a wide range of vibrating patterns is introduced to a surface on which a rigid mass is forced to slide. It has been observed that the dynamics of the involved mechanical components has an important role in the determination of the friction force. Structural optimization has been used to efficiently convey a large amount of energy to the mechanical surface to a degree that a combination of a squeeze film and the enlargement of the mean gap between the sliding surfaces reduce the friction force by orders of magnitude. Explanation of the involved physical phenomena alongside with experimental evidence will be presented to support the proposed theory.
Sensorless Early Detection of Mechanical Faults: Developments in Smart Rotating Machines
Authors: Parlos Alexander G. , Kim Kyusung , Bharadwaj Raj M.
Published: November 2020

Practical early fault detection and diagnosis systems must exhibit high level of detection accuracy and while exhibiting acceptably low false alarm rates. Such designs must have applicability to a large class of machines, require installation of no additional sensors, and require minimal detailed information regarding the specific machine design. Electromechanical systems, such as electric motors driving dynamic loads like pumps and compressors, often develop incipient failures that result in downtime. There is a large number of such failure modes, with a large majority being of mechanical nature. The precise signatures of these failure modes depend on numerous machine-specific factors, including variations in the electric power supply and driven load. In this paper the development and experimental demonstration of a sensorless, detection and diagnosis system is presented for incipient machine faults. The developed fault detection and diagnosis system uses recent developments in dynamic recurrent neural networks in implementing an empirical model-based approach, and multi-resolution signal processing for extracting fault information from transient signals. The signals used by the system are only the multi-phase motor current and voltage sensors, whereas the transient mechanical speed is estimated from these measurements using a recently developed speed filter. The effectiveness of the fault diagnosis system is demonstrated by detecting stator, rotor and bearing failures at early stages of development and during different levels of deterioration. Experimental test results from small machines, 2.2 kW, and large machines, 373 kW and 597 kW, are presented demonstrating the effectiveness of the proposed approach. Furthermore, the ability of the diagnosis system to discriminate between false alarms and actual incipient failure conditions is demonstrated.
Effects of an 8-Week Whole-Body Electromyostimulation Training on Cycling Performance, Back Pain, and Posture of a 17-Year-Old Road Cyclist
Authors: Berger Joshua , Ludwig Oliver , Becker Stephan , Kemmler Wolfgang , Fröhlich Michael
Published: November 2020

A 17-year-old male road cyclist with unspecific back pain and postural deficiency regarding the depth of the lumbar lordosis (flèche lombaire [fl]) and the upper body tilt (forward trunk tilt [tt]) absolved an 8-week whole-body electromyostimulation (WB-EMS) training to improve performance parameters and health issues. During WB-EMS, muscle groups all over the body are stimulated via external electrodes, thus creating an intensive training stimulus due to the electrically induced involuntary muscle contraction. The athlete’s posture (fl 2.2%, tt 64.3%) and back pain (54%) improved, and trunk strength increased (extension 15.5%, flexion 29.2%). This is the first WB-EMS study of a minor cyclist, suggesting positive effects of WB-EMS as a time-saving strength training method on health and strength parameters.