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SAE 2012 World Congress and Exhibition

作者： Ghazanfari, Amir Assempour, Ahmad Center of Excellence in Design Robotics and Automation Department of Mechanical Engineering Sharif University of Technology Azadi Avenue Tehran Iran

Major forming limit prediction models and calibration methods are reviewed briefly and their advantages and disadvantages are discussed. Two modified Marciniak-Kuczynski (M-K) models and one modified NADDRG (Keeler-Brazier) model are also presented which have some advantages over conventional models. In the first modified M-K model, material non-homogeneity has been substituted for geometrical non-homogeneity to reduce the sensitivity of the traditional model to variations of the initial non-homogeneity. Using this important advantage, a semi-empirical relation is proposed to predict the value of the initial material non-homogeneity. In the second modified M-K model, the conventional calibration method (which requires an experimental point, corresponding to plain strain condition, to find the initial non-homogeneity and calibrate the model) is revised and the uniaxial tensile point, which is easily obtained, is proposed to be used in the calibration process. Finally, a modified NADDRG relation is suggested which predicts the Forming Limit Curve (FLC) much more accurately and for various types of materials (i.e. not only low carbon steel). This new relation uses the value of strain rate sensitivity index. The results obtained from these models and calibration methods are compared with experimental results. The proposed modifications are very easy to implement;could be applied to various materials;require few and easily measurable parameters and are in good agreement with experiments. Copyright © 2012 SAE International.

关键词： Low carbon steel

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A new calibration method for FLCs in the M-K frame-work

A new calibration method for FLCs in the M-K frame-work

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2011 2nd International Conference on Material and Manufacturing Technology, ICMMT 2011

作者： Ghazanfari, Amir Assempour, Ahmad Center of Excellence in Design Robotics and Automation Department of Mechanical Engineering Sharif University of Technology Azadi Avenue Tehran Iran

ISBN: (纸本)9783037852521

The main drawback of the method proposed by Marciniak and Kuczynski for prediction of the limit strains in sheet metal forming processes is requirement of an experimental point of the forming limit curve (FLC) in order to calibrate the curve. The purpose of this work is to introduce a new method to calibrate the FLC using the M-K model in which no experimental data is needed. To achieve this goal, many experimental FLCs were collected from the literature and the values of the initial inhomogeneity factors were determined for them with trial and error aproach. Using these data, an empirical law was developed to predict the value of inhomogeneity factor. The resultant curves show good agreement with the experiments. © (2012) Trans Tech Publications, Switzerland.

关键词： Sheet metal

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Determination of geometrical parameters of the dead metal zone and exit curvature profile in the extrusion process of non-symmetrical flat dies

Determination of geometrical parameters of the dead metal zo...

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SAE 2012 World Congress and Exhibition

作者： Rastegar, Meysam Assempour, Ahmad Ghazanfari, Amir Center of Excellence in Design Robotics and Automation Department of Mechanical Engineering Sharif University of Technology Azadi Avenue Tehran Iran

To determine the curvature of the exit profile in the extrusion process of non-symmetrical flat dies, the dead metal zone profile was predicted using the energy minimization method. The dead zone is a natural non-linear die for the process and it is pragmatic to use this non-linear die to estimate the value of the exit profile curvature and the required bearing length for reducing this deviation. The velocity field is calculated based on Hermite cubic spline and some additional assumptions. In non-symmetrical dies the entrance section of the deformation region is not flat. Considering this fact, axial velocity decreases with increasing the distance to die center line which is in agreement with experiment. After determination of the velocity field, the strain rates in different directions are calculated. Subsequently, the required power for the process is estimated using the upper bound method. Since the material tends to consume less energy, to determine the profile of the dead zone, the coefficients of the curve are set so as to minimize the consumed power. Finally, using this curve, the value of the exit profile curvature is estimated. Dead metal zone for different angles of the deformation region at entry and different friction constant coefficients was determined and compared with the results of simulations of the finite element software (ABAQUS v6.9). Additionally, the deviation calculated from theoretical method was verified with the results of the commercially available bulk forming simulation software (Deform-3D v5). This method does not depend on the exit section and is applicable to non-symmetrical dies as well. The analytical results for non-symmetrical T-die are in good agreement with results of the finite element simulations. Copyright © 2012 SAE International.

关键词： Velocity

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Fault Diagnosis and Fault Tolerant Control Methods for Manned and Unmanned Helicopters: A Literature Review

Fault Diagnosis and Fault Tolerant Control Methods for Manne...

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Conference on Control and Fault-Tolerant Systems

作者： Xin Qi Didier Theilliol Juntong Qi Youmin Zhang Jianda Han Dalei Song Ling Wang Yong Xia State Key Laboratory of Robotics Shenyang Institute of Automation (SIA) in Chinese Academy of Sciences (CAS) University of Lorraine Faculte des Sciences et Techniques Department of Mechanical and Industrial Engineering Concordia Institute of Aerospace Design and Innovation (CIADI) Concordia University Benxi Power Supply Company Liaoning Electric Power Company

ISBN: (纸本)9781479928569

With the development of unmanned helicopters, the dependability of helicopters have attracted more and more attention of many researchers. In order to deal with these problems, fault diagnosis and fault tolerant control methods were used for manned or unmanned helicopter platforms. This paper presents an overview of the existing works on fault diagnosis, including analytical/model-based, signal processing-based and knowledge-based techniques, and passive/active fault tolerant control approaches for helicopters mainly with single rotor. Before the main part of the review, a short description of fault classification is presented. Compared with the former work, this review contains some in-depth discussion of various fault diagnosis techniques and a survey for fault tolerant control methods.

关键词： drone helicopters Fault diagnosis fault-tolerant control Helicopters Control Methods Literature Review MAN Fault class

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COMPUTATIONALLY EFFICIENT METHOD FOR JOINT AZIMUTH-ELEVATION DIRECTION ESTIMATION WITH L-SHAPED ARRAY

COMPUTATIONALLY EFFICIENT METHOD FOR JOINT AZIMUTH-ELEVATION...

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IEEE Workshop on Signal Processing Advances in Wireless Communications

作者： Guangmin Wang Jingmin Xin Nanning Zheng Akira Sano Institute of Artificial Intelligence and Robotics Xi'an Jiaotong University Xi'an 710049 China Department of System Design Engineering Keio University Yokohama 223-8522 Japan

ISBN: (纸本)9781467355766

For overcoming the problems of pairing failure and estimation failure, which are frequently encountered in two-dimensional (2-D) direction-of-arrival (DOA) estimation of multiple signals, we propose a new computationally efficient subspace-based based 2-D DOA estimation with automatic pair-matching method for noncoherent narrowband signals impinging on the L-shaped sensor array structured by two uniform linear arrays (ULAs). In the proposed method the computationally expensive procedures of eigendecomposition in subspace estimation and pair-matching of the estimated azimuth and elevation angles are avoided, while the problems of pairing failure and estimation failure are overcome. The statistical analysis is studied, and the closed-form expressions of the asymptotic mean-square-errors (MSEs) of the elevation and azimuth estimates are derived explicitly. Finally the effectiveness of the proposed method and the theoretical analysis are substantiated through numerical examples.

关键词： METHOD JOINT AZIMUTH-ELEVATION

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HRI Pioneers Workshop 2013 13

HRI Pioneers Workshop 2013

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ACM/IEEE International Conference on Human-Robot Interaction (HRI)

作者： Solace Shen Henny Admoni Caroline Harriott Yunkyung Kim Matt Marge Marynel Vázquez Astrid Rosenthal-von der Pütten Matt Beane Yasuhiko Hato Daniel Lazewatsky Robin Read Steve Vozar Department of Psychology University of Washington Seattle USA Department of Social Psychology University of Duisburg-Essen Duisburg Germany Department of Computer Science Yale University New Haven USA Sloan School of Management Massachusetts Institute of Technology Cambridge USA Department of Electrical Engineering & Computer Science Vanderbilt University Nashville USA Graduate School of Science & Technology Keio University Yokohama Japan Department of Industrial Design Korea Advanced Institute of Science and Technology Daejeon South Korea Industrial & Manufacturing Engineering Oregon State University Corvallis USA Language Technologies Institute Carnegie Mellon University Pittsburgh USA Centre for Robotics & Neural Systems University of Plymouth Plymouth UK Robotics Institute Carnegie Mellon University Pittsburgh USA Department of Mechanical Engineering University of Michigan Ann Arbor USA

ISBN: (纸本)9781467330558

The 2013 Human-Robot Interaction (HRI) Pioneers Workshop, which will be held in conjunction with the 8 th ACM/IEEE International Conference on Human-Robot Interaction, is the premiere venue for student research in the field. This highly selective workshop seeks to foster creativity, communication, and collaboration between the world's top student researchers in the field of human-robot interaction. Pioneers Workshop participants will have the opportunity to learn about the current state of HRI, to present their research, and to network with one another and with select senior researchers in a setting that is less formal and more interactive then the main conference. The theme for this year is Re-envisioning HRI: Dealing With the Elephants in Our Room. The workshop aims to bring forward difficult to discuss issues to help the field achieve more balanced perspectives and a clearer picture of what sort of future we are building.

关键词： Educational institutions Conferences Human-robot interaction Psychology Computer science Service robots

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Tool condition monitoring based on sound and vibration analysis and wavelet packet decomposition

Tool condition monitoring based on sound and vibration analy...

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2012 8th International Symposium on Mechatronics and its Applications, ISMA 2012

作者： Rafezi, Hamed Akbari, Javad Behzad, Mehdi Sharif University of Technology International Campus School of Science and Engineering Kish Island Iran Sharif University of Technology Department of Mechanical Engineering Center of Excellence in Design Robotics and Automation Tehran Iran

ISBN: (纸本)9781467308625

Tool Condition Monitoring (TCM) is a vital demand of advanced manufacturing in order to develop automated unmanned production. Continuing the machining operation with a worn or damaged tool will result in damages to the workpiece. This problem becomes more important in supplementary machining processes like drilling which the workpiece usually has passed a lot of machining processes and any damage to workpiece at this stage results in high production losses. In this research features of sound pressure and vibration signals in drilling process are recorded and analyzed in order to detect tool wear. Signal statistical features are extracted in time domain, and the features trends as the tool becomes worn are extracted. Frequency spectrum of signals is calculated and Wavelet Packet Decomposition (WPD) is applied to focus on specific frequency bands. In this research capability of both sound and vibration signals for drill wear detection are shown and the most informative features of the signals for wear detection are evaluated and introduced. The results showed that the wavelet packets features make a better contrast between the sharp and the worn tool compared to the primary time domain signal. © 2012 IEEE.

关键词： Vibration analysis

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Development of parallel manipulator sit to stand assistive device for elderly people

Development of parallel manipulator sit to stand assistive d...

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IEEE Workshop on Advanced robotics and its Social Impacts, ARSO

作者： Omar Salah Ahmed Asker Ahmed M. R. Fath El-Bab Samy M. F. Assal Ahmed A. Ramadan Salvatore Sessa Ahmed Abo-Ismail Egypt-Japan University of Science and Technology Alexandria Egypt Egypt-Japan University of Science and Technology New Borg-El-Arab Alexandria Egypt El-Bab is with Egypt-Japan University of Science and Technology New Borg-El-Arab Alexandria Egypt Department of production engineering and mechanical design Egypt Tanta University Alexandria Egypt Mechatronics and Robotics dept. Egypt-Japan University of Science and Technology School of Creative Science and Engineering Waseda University Tokyo Japan

This paper describes a novel mobility assistive device under development in the Egypt-Japan University of Science and Technology (E-JUST). The proposed system can help patients who do not have enough physical strength on the lower limbs during sit to stand due to aging, diseases such as polymyositis and myopathy, and joint replacement surgery complications. It can follow the natural pattern of human motion during sit to stand providing assistance force under the shoulder. The overall device is compact and employees a parallel mechanism which provide more stiffness. Several experiments were carried out in a VICON room to calculate the human motion posture while sit to stand motion in addition estimate the trajectory of the end effector during assisting. Computer simulation was built to verify the performance of the proposed system with the reference trajectory.

关键词： Actuators Force Assistive devices Hip Educational institutions Joints End effectors

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Forming limit diagrams of ground St14 steel sheets with different thicknesses

Forming limit diagrams of ground St14 steel sheets with diff...

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SAE 2012 World Congress and Exhibition

作者： Hashemi, Ramin Ghazanfari, Amir Abrinia, Karen Assempour, Ahmad University of Tehran Iran Center of Excellence in Design Robotics and Automation Department of Mechanical Engineering Sharif University of Technology Azadi Avenue Tehran Iran Tehran Univ Iran

The influence of sheet thickness on sheet metal forming limits is a controversial issue;while some investigations indicate the considerable influence of thickness on forming limit diagrams (FLDs), others suggest that it is of negligible importance. In the present work, it has been demonstrated that if the thickness-reduction process is chosen so as not to alter the micro structure of the material, the forming limits do not change with variations of thickness. A material which has extensive usage in sheet metal forming processes of automotive industry (St14) has been provided. The initial thickness of the sheet is 1.5mm and using grinding process (which does not alter the microstructure) the initial thickness is reduced to different thicknesses, namely 1 and 0.5mm. Afterwards, the FLDs for all three thicknesses were determined using standard test methods. The FLDs for specimens which were ground to various thicknesses differ slightly. This small difference is attributed to bending effects resulted from curvature of the punch. Thus, the results strongly support the conclusion that the absolute value of thickness has no influence on forming limits of St14 steel sheet. Copyright © 2012 SAE International.

关键词： Microstructure

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Investigation of Thermal Effects on Machining Chatter Using FEM Simulation of Chip Formation

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Procedia CIRP 2012年 1卷 50-55页

作者： Mohammad S. Hajmohammadi Mohammad R. Movahhedy Centre of Excellence in Design Robotics and Automation Department of Mechanical Engineering Sharif University of Technology Tehran Iran

Chatter vibration is a major cause of limitations in increasing material removal rate in machining. Machining chatter is caused by the interaction between tool and work-piece. Various nonlinear phenomena in the machining process affect the occurrence of chatter. Finite element simulation of chip formation allows for incorporation of various factors in the chip formation process. It can therefore be used to simulate the occurrence of chatter in practical conditions and to predict the conditions that lead to stable cutting. In this paper, a one degree of freedom dynamic model of the cutting tool is used to simulate the interaction of machining dynamics with the thermo-mechanical chip formation in orthogonal conditions. In this way, the effects of various phenomena such as friction, plastic deformation, heat generation and process damping on the occurrence of chatter may be investigated. In particular, the effect of heat rise in the cutting zone is investigated in this paper, which has not been reported in the literature before. It is shown how rising the temperature in the cutting zone can affect occurrence of chatter. Simulation results are presented and stability lobe diagram is obtained from simulation.

关键词： Chatter Finite element method Stability lobe diagram Thermal effects

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