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12th International Congress on Sound and Vibration 2005, ICSV 2005

作者： Yiakopoulos, Christos Antoniadis, Ioannis National Technical University of Athens Department of Mechanical Engineering Machine Design and Control Systems Section P.O. Box 64078 Athens 15710 Greece

ISBN: (纸本)9781627481496

Vibration response of rotating machines is typically mixed and corrupted by a variety of interfering sources and noise, leading to the necessity for the isolation of the useful signal components. A relevant frequently encountered industrial case is the need for the separation of the vibration responses of the same type of bearings inside the same machine. For this purpose, a Blind Source Separation procedure has been successfully applied, based on the maximization of the information transferred in a neural network structure. Thus, a key element for the success of the proposed procedure is the non-linear function used in this single layer Neural Network structure. For this reason, since the vibration response of defective rolling element bearings is characterized by signals with super-Gaussian distributions, a flexible form of this function is used in this paper. The results from an experimental test rig indicate that the performance of the method is insensitive to the form of this function.

关键词： Roller bearings

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Robust payload vibration suppression in rotary cranes by pre-filtering the commanded inputs

Robust payload vibration suppression in rotary cranes by pre...

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12th International Congress on Sound and Vibration 2005, ICSV 2005

作者： Glossiotis, George Antoniadis, Ioannis National Technical University of Athens School of Mechanical Engineering Machine Design and Control Systems Section P.O. Box 64078 Athens 15710 Greece

ISBN: (纸本)9781627481496

A method is proposed for the suppression of the sway of rotary crane payloads. The proposed method is based just on the preprocessing of all the commanded crane inputs by a properly designed FIR filter. A four-Degrees-Of- Freedom (4-DOF) model for the rotary crane system is considered, incorporating both the hoisting and the slewing motions, and is thus able to handle also cases where hoisting can be simultaneously applied to the rotary motion. Although the resulting dynamic system is strongly non-linear and time varying, the method is shown to effectively suppress in a quite robust, time and energy efficient way, both the transient as well as the residual sway of the payload. Moreover, additional advantages of the proposed method are that no dynamic modeling of the crane is required, and that the applicability of the method is quite easy and general, without the necessity of any additional instrumentation and control equipment.

关键词： Cranes

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Pre-operative planning of dental implant therapy: Optimum implant axis allocation

Pre-operative planning of dental implant therapy: Optimum im...

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3rd IASTED International Conference on Medical engineering 2005

作者： Galanis, Christos C. Sfantsikopoulos, Michael M. Koidis, Petros T. Kafantaris, Nikolaos M. Mpikos, Pavlos G. National Technical University of Athens School of Mechanical Engineering Mechanical Design and Control Systems Division Iroon Polytechneiou 9 15780 Athens Greece Department of Fixed Prosthesis and Implant Prosthodontics University Campus Aristotle University of Thessaloniki 54124 Thessaloniki Greece

ISBN: (纸本)0889864780

Preoperative planning of the therapy with oral endosseous implants is a complicated procedure with many parameters to be taken into account. In this work, a method based on processing of CT images is presented, that contributes to the automatic and optimum allocation (position and orientation) of an implant's axis. Respective optimization criteria are established in conjunction with the geometrical structure and quality of the hosting bone. The aesthetical result of the prosthesis is also considered, requiring from the patient to wear a scan template. An application example of the developed Imfix algorithm is discussed.

关键词： Dental prostheses

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Recursive backstepping stabilization of a wheeled mobile robot

Recursive backstepping stabilization of a wheeled mobile rob...

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作者： Mnif, F. Yahmadi, A.S. Intelligent Control Design and Optimization of Complex Systems Tunisia Department of Electrical and Computer Engineering Sultan Qaboos University Muscat Oman Department of Mechanical and Industrial Engineering Sultan Qaboos University Muscat Oman Department of Electrical Engineering College of Engineering Sultan Qaboos University PO Box 33 Muscat 123 Oman

This research is aimed at the development of a dynamic control to enhance the performance of the existing dynamic controllers for mobile robots. System dynamics of the car-like robot with non-holonomic constraints were employed. A backstepping approach for the design of a discontinuous state feedback controller is used for the design of the controller. It is shown that the origin of the closed-loop system can be made stable in the sense of Lyapunov. The control design is made on the basis of a suitable Lyapunov function candidate. The effectiveness of the proposed approach is tested through simulation on a car-like vehicle mobile robot. © IMechE 2005.

关键词： Mobile robots

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Transport of Mars-Crossing Asteroids from the Quasi-Hilda Region

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Physical Review Letters 2005年第23期94卷 231102-231102页

作者： Michael Dellnitz Oliver Junge Martin W. Lo Jerrold E. Marsden Kathrin Padberg Robert Preis Shane D. Ross Bianca Thiere Faculty of Computer Science Electrical Engineering and Mathematics University of Paderborn D-33095 Paderborn Germany Navigation and Mission Design Jet Propulsion Laboratory California Institute of Technology M/S 301-140L 4800 Oak Grove Drive Pasadena California 91109 USA Control and Dynamical Systems California Institute of Technology MC 107-81 Pasadena California 91125 USA Department of Aerospace and Mechanical Engineering University of Southern California Los Angeles California 90089 USA

We employ set oriented methods in combination with graph partitioning algorithms to identify key dynamical regions in the Sun-Jupiter-particle three-body system. Transport rates from a region near the 3∶2 Hilda resonance into the realm of orbits crossing Mars’ orbit are computed. In contrast to common numerical approaches, our technique does not depend on single long term simulations of the underlying model. Thus, our statistical results are particularly reliable since they are not affected by a dynamical behavior which is almost nonergodic (i.e., dominated by strongly almost invariant sets).

关键词： .graph orbits partitioning week ending Asteroids Preis Mars-Crossing Quasi-Hilda

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Weight minimisation of displacement-constrained truss structures using a strain energy criterion

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Computer Methods in Applied Mechanics and engineering 2002年第19-20期191卷 2187-2205页

作者： Makris, Panagiotis A. Provatidis, Christopher G. Department of Mechanical Engineering Mechanical Design and Control Systems Section National Technical University of Athens 9 Heroon Polytechniou Ave Zographou Athens 157 80 Greece

This paper discusses a new method for the solution of the general truss weight-minimisation problem under simultaneous stress and displacement constraints. The method introduces a novel strain-energy-density criterion that refers to the ratio of the virtual strain energy per unit volume in each structural member to its average value on the whole structure. The virtual strain energy comes from the unit-load theorem and it is proportional to the product of the axial member forces due to both the actual loads and a virtual unit load that is applied at the node with the maximum displacement. A simple recursive formula for updating the cross-sectional areas, based on displacement constraints, is presented. A general subsequent algorithm applicable to both single and multiple load cases follows this formula. The results are encouraging since in all test cases the method was found to be robust and generally led to the same weight level as the literature, in both small and large structures. © 2002 Elsevier Science B.V. All rights reserved.

关键词： Trusses

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A time-frequency envelope estimation method for detection of bearing-localized defects

A time-frequency envelope estimation method for detection of...

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ASME 2001 International design engineering Technical Conferences and Computers and Information in engineering Conference, IDETC-CIE 2001

作者： Nikolaou, Nikolaos G. Antoniadis, loannis A. Mechanical Design and Control Systems Division Department of Mechanical Engineering National Technical University of Athens Greece P.O. BOX 64078 Athens15710 Greece

This paper proposes a new method for the estimation of the envelope of signals resulting from rolling element bearing-localized defects, based on the use of a shifted Morlet wavelet family. Using a time-frequency representation of the signal, the method is designed in a way that can exploit the underlying physical concepts of the modulation mechanism, present in the vibration response of bearings with localized defects. Systematic selection criteria for the automated choice of the critical parameters that characterize the Morlet wavelet family are used. The method is evaluated by using actual vibration signals measured from bearings with defects at different locations. © 2001 American Society of mechanical Engineers (ASME). All rights reserved.

关键词： Roller bearings

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New embrittled shell element for airframe crash simulation

New embrittled shell element for airframe crash simulation

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Sixth International Conference on Computer Aided Optimum design of Structures - OPTI 2001

作者： Patronelli, L. Langrand, B. Deletombe, E. Markiéwicz, E. Drazétic, P. Department of Solid Mechanics Struct. Resist. and Design Section ONERA Lille France Indust. and Human Automatic Control Mechanical Engineering Laboratory University of Valenciennes France

The paper deals with problem linked to finite element analysis of airframe crash study. Today the limit of Finite Element analysis imposes a minimum shell element size which does not represent local failure due to riveted joints. These local failures are generally critical and it leads the global ruin mode of airframe during crash. It is difficult to find a compromise between computation time (relative to size of model, size of elements, numerical power of tools) and prediction of simulation linked to thin description of geometry which influence generally initiation of crack propagation. In this context a new embrittled shell element is developed. The main topic of this work is to set up a methodology to extract parameters for the characterisation of this new equivalent element. The feasibility of the concept is shown through an example of a punched plate in aluminium alloy. Then, it is proposed under hypothesis to extend this concept to a plate with six holes. The obtained results show interest of the method and ability to improve the representation of a model conserving reasonable computation time.

关键词： Airframes

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Experimental demonstration of input preconditioning for residual vibration suppression using low-pass FIR digital filters

Experimental demonstration of input preconditioning for resi...

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American control Conference (ACC)

作者： D. Economou C. Lee C. Mavroidis I. Antoniadis Mechanical Design and Control Systems Division Department of Mechanical Engineering National and Technical University of Athens Greece Robotics and Mechatronics Laboratory Department of Mechanical and AeroSpace Engineering State University of New Jersey Rutgers Piscataway NJ USA

A method for suppressing residual vibrations in flexible systems is presented and experimentally demonstrated. The proposed method is based on the preconditioning of the inputs to the system using conventional low-pass FIR digital filters. Several classes of FIR filters such as: a) Parks-McClellan; b) window-based method (using Chebyshev window); and c) constrained least squares method, are shown to demonstrate excellent vibration suppression when they are properly designed while they introduce minimum possible delay. In order to ensure maximally robust behavior, the filter stop band is selected to cover all possible variations of the system dynamic parameters. The proposed method does not require modeling of the flexible system, can be used in a variety of systems exhibiting vibrations, is independent of the guidance function, is simple to implement in practical applications and robust to variations of the system dynamic parameters. The method is experimentally verified using a flexible aluminum beam attached at the end-effector of a robot manipulator. The beam is rotated, using one joint of the manipulator, from an initial to a final position. During this motion, vibrations of the beam are excited due to inertial forces. It is shown that the preconditioned inputs to the flexible system induce very little amount of residual vibrations compared to the inputs with no preconditioning.

关键词： Finite impulse response filter Robustness Digital filters Delay control systems mechanical engineering Vibration control Manipulator dynamics Convolution Aerodynamics

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Experiments on robust vibration suppression in mechatronic systems using IIR digital filters

Experiments on robust vibration suppression in mechatronic s...

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IEEE/ASME (AIM) International Conference on Advanced Intelligent Mechatronics

作者： D. Economou C. Mavroidis I. Antoniadis Meohanical Design and Control Systems Division Departmeat of Mechanical Engineering National and Technical University of Athens Athens Greece Robotics and Mechatronics Laboratory Department of Mechanical and Aerospace Engineering State University of New Jersey Rutgers Piscataway NJ USA

ISBN: (纸本)0780367367

In this paper, a method for suppressing residual vibrations in flexible mechatronic systems is proposed and experimentally demonstrated. The proposed method is based on the preconditioning of the arbitrary inputs to the system using infinite impulse response (IIR) digital filters. To ensure robust behavior, the filter stop band is selected to cover all possible variations of the system dynamic parameters. It is shown that some of the IIR filters are capable of suppressing vibrations when they are properly designed.

关键词： Robustness Mechatronics Digital filters IIR filters Vibrations Finite impulse response filter control systems Cranes Convolution mechanical engineering

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