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2006 ASME International Mechanical engineering Congress and Exposition, IMECE2006

作者： Tafti, Sayyed Rouhollah Jafari Radparvar, Yousha Salarieh, Hassan Alasty, Aria Center of Excellence in Design Robotics and Automation School of Mechanical Engineering Sharif University of Technology P.O.Box 11365-9567 Tehran Iran

ISBN: (纸本)0791837904

In this paper, a new method for tracking a desired path in nonlinear chaotic systems is presented. This method is based on using fuzzy gain scheduling in designing PID controller and Lead compensator. Using two standard controllers, PID and Lead, instead of complicated and costly nonlinear controllers is the main advantage of the proposed control system. PID controller has a stabilizing role whereas Lead compensator improves the performance of the system to track the desired path properly. To determine the PID and Lead gains, the nonlinear system is linearized around some working points which are the points of the desired path in specified times, and the gains are designed for each linearized system. Using a Sugeno system as a fuzzy gain scheduler, PID and Lead gains are determined in each time and are applied to the control system to make the nonlinear system track the desired path. To verify the presented method, Duffing equation as a chaotic system is considered to be controlled to which the proposed procedure is applied. Simulation results show the effectiveness of fuzzy gain scheduling in making the nonlinear system track different desired paths more smoothly. Copyright © 2006 by ASME.

关键词： Three term control systems

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Online prediction of plate deformations under external forces using neural networks

Online prediction of plate deformations under external force...

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2006 ASME International Mechanical engineering Congress and Exposition, IMECE2006

作者： Ahmadian, M.T. Mobini, A. Center of Excellence in Design Robotics and Automation School of Mechanical Engineering Sharif University of Technology P.O. Box 11365-9567 Tehran Iran

ISBN: (纸本)0791837904

Recently online prediction of plate deformations in modern systems have been considered by many researchers, common standard methods are highly time consuming and powerful processors are needed for online computation of deformations. Artificial neural networks have capability to develop complex, nonlinear functional relationships between input and output patterns based on limited data. A good trained network could predict output data very fast with acceptable accuracy. This paper describes the application of an artificial neural network to identify deformation pattern of a four-side clamped plate under external loads. In this paper the distributed loads are approximated by a set of concentrated loads. An artificial neural network is designed to predict plate deformation pattern under external forces. Results indicate a well trained artificial neural network reveals an extremely fast convergence and a high degree of accuracy in the process of predicting deformation pattern of plates. Additionally this paper represents application of neural network in inverse problem. This part illustrates the capability of neural networks in identification of plate external loads based on plate deformations. Load identification has many applications in identification of real loads in machineries for design and development. Copyright © 2006 by ASME.

关键词： Neural networks

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Dynamic finite element modeling of electrostatical actuated micro structures considering squeeze film damping effect

Dynamic finite element modeling of electrostatical actuated ...

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2006 ASME International Mechanical engineering Congress and Exposition, IMECE2006

作者： Ahmadian, M.T. Borhan, Hoseinali Moghimi Zand, M. Sharif University of Technology Center of Excellence for Design Robotics and Automation School of Mechanical Engineering P.O. BOX 11365-9567 Tehran Iran

ISBN: (纸本)0791837904

Developing a transient fully-meshed model of coupled-domain microsystems is of paramount importance not only for accurate simulation and design but also for creating more accurate low-order or macro dynamic models. So in this paper, a complete nonlinear finite element model for coupled-domain MEMS devices considering electrostatic and squeeze film effects is presented. For this purpose, we use the Galerkin weighted-residual technique for developing the finite element model that capture the original microsystem's nonlinear behaviors, such as the structural dynamics, the squeeze-film damping, the electrostatic actuation and the geometric nonlinearity caused by inherent residual stresses. In addition, using the Newmark's nonlinear solution technique, the extracted dynamic equilibrium equations are discretised and simulated. The system dynamic behavior is successfully modeled by using the developed nonlinear finite element model and finally some simulated results of electrostatic micro-actuator behaviors are verified with experimental findings and are in very good agreement. Copyright © 2006 by ASME.

关键词： Thin films

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Closed-loop finite element modeling for analysis of smart structures in ansys environment

Closed-loop finite element modeling for analysis of smart st...

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2006 ASME International Mechanical engineering Congress and Exposition, IMECE2006

作者： Mahboobi, Seyed Hanif Shahidi, Alireza Abedian, Ali Meghdari, Ali Center of Excellence in Design Robotics and Automation School of Mechanical Engineering Sharif University of Technology Tehran Iran School of Mechanical Engineering Sharif University of Technology Tehran Iran Department of Aerospace Engineering Sharif University of Technology Tehran Iran

ISBN: (纸本)0791837904

It would be promising if one can simulate the closed-loop behavior of a smart system in an available FEM software such as "ANSYS". The ANSYS/Multiphysics software has the ability of coupling different physical domains and also modeling smart materials such as piezoelectric and piezoresistives, i.e. it has the capability of modeling smart structures. The dynamic modeling of the controlled structures is then realized by the ANSYS programming tool. This aspect highly facilitates the overall system behavior analysis and at the same time various control methods can be tested without noticing the time consuming structural analysis involved. In this research work, it is tried the mentioned idea to be implemented and some control strategies for the structural active damping to be examined. Copyright © 2006 by ASME.

关键词： Intelligent structures

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Vibrational Analysis of Multi Layer Microplates Considering Nonlinear Squeeze Film Damping and Electrostatic Actuation

Vibrational Analysis of Multi Layer Microplates Considering ...

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The second Asia-Pacific International Conference on Computational Methods in engineering（ICOME2006）

作者： M.T.Ahmadian M.Moghimi Zand M.Bonakdar Center of Excellence in Design Robotics and Automationschool of mechanical engineeringSharif University of Technology

This paper presents a model to analyze vibrational behavior of multi layer microplates. First-order shear deformation theory is used to model dynamical system using finite element method, While finite difference method is applied to solve nonlinear Reynolds equation of squeeze film damping .Using this model, dynamic and static Pull- in analysis of multi layer microplates are studied. Vibrational behavior of single layer and multi layer microplates are analyzed to compute resonance frequencies and mode shapes of the system. Also, under the actuation of step- input voltage, response frequencies of the dynamic system is calculated considering nonlinear squeeze film damping. Results for simplified single layer microplates are validated and in good agreement with the published literature. This investigation can be implemented in the design of multi layer microplates.

关键词： Vibration Squeeze Film Damping Pull-in Multi Layer Microplates Electrostatic

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Intelligent Control of Powered Exoskeleton to Assist Paraplegic Patients Mobility using Hybrid Neuro-Fuzzy ANFIS Approach

Intelligent Control of Powered Exoskeleton to Assist Paraple...

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IEEE International Conference on robotics and Biomimetics

作者： A. Selk Ghafari A. Meghdari G.R. Vossoughi Center of Excellence in Design Robotics and Automation (CEDRA) School of Mechanical Engineering Sharif University of Technology Tehran Iran

Integrating humans and robotics technology into one system offers multiple opportunities for creating assistive technologies that can be employed in biomechanical, industrial, and aerospace applications. The present study deals with employing the adaptive neuro-fuzzy inference system (ANFIS) approach in rule base derivation for powered exoskeleton intelligent control to assist paraplegic patient mobility. By employing the hybrid learning algorithm, optimal distributed membership functions to describe the mapping relation in the input and output parameters of the gait cycle were derived. As the proposed control strategy was unaffected by changing human dynamics, the reliability and robustness of the controller for safe interaction with humans were increased.

关键词： Intelligent control Exoskeletons Humans Aerospace industry Service robots Electrical equipment industry Industrial relations Adaptive systems Programmable control Adaptive control

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Parameterization of All Stabilizing Hc. Static State-Feedback Gains: Application to Output-Feedback Design

Parameterization of All Stabilizing Hc. Static State-Feedbac...

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IEEE Conference on Decision and Control

作者： J. Gadewadikar F. Lewis L. Xie V. Kucera M. Abu-Khalaf Automation and Robotics Research Institute Arlington USA Electrical Engineering Automation and Robotics Research Institute Arlington USA School of Electrical and Electronic Engineering Nanyang Technological University Singapore Center for Applied Cybernetics Control Engineering Czech Technical University Prague Czech Republic Adjunct Instructor Electrical Engineering Automation and Robotics Research Institute Arlington USA

This paper presents a simplified parameterization of all H infin static state feedback controllers in terms of a single algebraic Riccati equation and a free parameter matrix. As a special case, necessary and sufficient conditions for the existence of an H infin static output feedback gain are given. An efficient computational algorithm is given. No initial stabilizing output feedback gain is needed. The technique is used to design an H infin lateral-directional command augmentation system for the F-16 aircraft

关键词： Riccati equations Output feedback robotics and automation Nonlinear equations State feedback Optimal control Vehicle dynamics Aerodynamics Symmetric matrices Control systems

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Dynamical stress distribution analysis of a non-uniform cross-section beam under moving mass

Dynamical stress distribution analysis of a non-uniform cros...

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2006 ASME International Mechanical engineering Congress and Exposition, IMECE2006

作者： Ahmadian, M.T. Esmailzadeh, E. Asgari, M. Center of Excellence in Design Robotics and Automation Sharif University of Technology P.O. Box 11365-8639 Tehran Iran Faculty of Engineering and Applied Science University of Ontario Institute of Technology Oshawa Ont. Canada School of Mechanical Engineering Sharif University of Technology P.O. Box 11365-8639 Tehran Iran

ISBN: (纸本)0791837904

One of the engineers concern in designing bridges and structures under moving load is the uniformity of stress distribution. In this paper the analysis of a variable cross-section beam subjected to a moving concentrated force and mass is investigated. Finite element method with cubic Hermitian interpolation functions is used to model the structure based on Euler-Bernoulli beam and Wilson- direct integration method is implemented to solve time dependent equations. Effects of cross-section area variation, boundary conditions, and moving mass inertia on the deflection, natural frequencies and longitudinal stresses of beam are investigated. Results indicates using a beam of parabolically varying thickness with constant mass can decrease maximum deflection and stresses along the beam while increasing natural frequencies of the beam. The effect of moving mass inertia of moving load is found to be significant at high velocity. Copyright © 2006 by ASME.

关键词： Stress concentration

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Dynamic modeling of geometrically nonlinear electrostatically actuated microbeams (Corotational Finite Element formulation and analysis)

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Journal of Physics: Conference Series 2006年第1期34卷 606-613页

作者： Borhan, H. Ahmadian, M.T. Sharif University of Technology Center of Excellence for Design Robotics and Automation School of Mechanical Engineering Tehran PO Box 11365-9567 Iran

In this paper, a complete nonlinear finite element model for coupled-domain MEMS devices with electrostatic actuation and squeeze film effect is developed. For this purpose, a corotational finite element formulation for the dynamic analysis of planer Euler beams is employed. In this method, the internal nodal forces due to deformation and intrinsic residual stresses, the inertial nodal forces, and the damping effect of squeezed air film are systematically derived by consistent linearization of the fully geometrically nonlinear beam theory using d′Alamber and virtual work principles. An incremental-iterative method based on the Newmark direct integration procedure and the Newton-Raphson algorithm is used to solve the nonlinear dynamic equilibrium equations. Numerical examples are presented and compared with experimental findings which indicate properly good agreement. © 2006 IOP Publishing Ltd.

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Mechanism synthesis for path generation using the curvature based - Deflection based objective function

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WSEAS Transactions on Systems 2006年第12期5卷 2839-2843页

作者： Damangir, Soheil Jafarijashemi, Ghazaleh Mamduhi, Mohammadhossein Aghmioni, Alireza Nazemzadeh Zohoor, Hassan School of Mechanical Engineering Sharif University of Technology Tehran Iran Taylor's College Subang Jaya Kuala Lumpur Malaysia Academy of Sciences of I.R. Iran Center of Excellence in Design Robotics and Automation Sharif University of Technology Tehran Iran

This paper proposed a new curvature based path-description method for path-generation of planar mechanism, in which the position vector of a point on coupler, which follows most closely a predefined path, is directly calculated as a function of coupler motion properties. In addition this curvature based method makes it possible to define an objective function independent of rotation and translation transformations. Therefore, in this method, initial position, orientation, and coupler point vector parameters are not the optimization variable. These five parameters could be calculated as a function of other design parameters and they are found when these optimal values are obtained. Reducing five parameters of the optimal variables leads to a smaller design space and so less computation time to find the optimal result. Application of the method is also shown and its computation time and accuracy are compared with the result reported in the literature. It is found that this method is superior as it converges faster without loosing any accuracy.

关键词： Motion planning

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