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IEEE International Conference on Sustainable Energy Technologies, ICSET

作者： Zaeem M. Moosavi Hassan Zohoor Faculty of Environment & Energy Sciences & Researches Branch Islamic Azad University Tehran Iran Academy of Sciences of IR Iran Center of Excellence Design Robotics & Automation Sharif University of Technology Tehran Iran

The intermittent nature of solar energy and the energy requirements of buildings necessitate the storage of thermal energy. In this paper a hybrid system of storing solar energy has been analyzed. The suggested hybrid storage system consists of two tanks: a water tank as a SHS medium; and a paraffin tank as a LHS medium. A computing program was used to find the optimized time schedule of charging the storage tanks during each day, according to the solar radiation conditions. The results show that the use of such system can improve the capability of energy gathering comparing to the individual water storage tank during the cold months of the year. Of course, because of the solar radiation angles and shorten daylight in December & January, the performance will be the same as the simple solar water heaters (in the northern hemisphere). But investment analysis shows that because of extra energy stored in November, February, March & April, this modification will be a feasible solution.

关键词： Energy storage Solar energy Solar heating Water storage Phase change materials Heat recovery Water heating Thermal management Material storage Fluid flow control

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New Jacobian matrix and equations of motion for a 6 d.o.f cable-driven robot

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International Journal of Advanced Robotic Systems 2007年第1期4卷 63-68页

作者： Afshari, Ali Meghdari, Ali Center of Excellence in Design Robotics and Automation Department of Mechanical Engineering Sharif University of Technology Tehran Iran

In this paper, we introduce a new method and new motion variables to study kinematics and dynamics of a 6 d.o.f cable-driven robot. Using these new variables and Lagrange equations, we achieve new equations of motion which are different in appearance and several aspects from conventional equations usually used to study 6 d.o.f cable robots. Then, we introduce a new Jacobian matrix which expresses kinematical relations of the robot via a new approach and is basically different from the conventional Jacobian matrix. One of the important characteristics of the new method is computational efficiency in comparison with the conventional method. It is demonstrated that using the new method instead of the conventional one, significantly reduces the computation time required to determine workspace of the robot as well as the time required to solve the equations of motion.

关键词： Mobile robots

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Introducing a new 3 legged 6-DOF ups parallel mechanism for pole climbing applications

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WSEAS Transactions on Systems 2007年第1期6卷 221-228页

作者： Vossoughi, G.R. Abedinnasab, M.H. Aghababai, O. Mechanical Engineering Dept. CEDRA Center of Excellence in Design Robotics and Automation Sharif University of Technology Tehran Iran

In this paper, we propose a new 6-DOF parallel mechanism. Due to the fact that degrees of freedom in this robot outnumber the number of kinematic chains, it is not a fully parallel mechanism. This results in a weight and inertia reduction and better dynamic performance, making it ideal for haptic and pole climbing applications. The fact that the mechanism is open on one side enable it to wrap around a pole from one side minimizing the center of gravity distance from the pole and the resulting gripping moments. Both inverse and forward Kinematic and dynamic analysis of the proposed mechanism is addressed. Workspace of the mechanism is compared to that of the Stewart's mechanism and the results show better performance. Jacobian matrix has also been determined and singular points have been discussed. Finally, the simulation results have also been validated using Matlab's SimMechanics™ Toolbox.

关键词： Robots

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Natural frequencies of stiffened and unstiffened laminated composite plates

Natural frequencies of stiffened and unstiffened laminated c...

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ASME 2007 International Mechanical Engineering Congress and Exposition, IMECE 2007

作者： Ahmadian, M.T. Pirbodaghi, T. Pak, M. Center of Excellence in Design Robotics and Automation School of Mechanical Engineering Sharif University of Technology Tehran11365-9567 Iran

ISBN: (纸本)0791843017

In this study the free vibration of laminated composite plates with and without stiffeners subjected to axial loads is carried out using finite element method. The plates are stiffened by laminated composite strip and Timoshenko beam. The plates and the strips are modeled with rectangular 9 noded isoparametric quadratic elements with three degrees of freedom per node and the Timoshenko beam is modeled with linear 2 noded isoparametric quadratic elements with 2 degrees of freedom per node. The effects of both shear deformation and rotary inertia are implemented in the modeling of plate and stiffener. The governing differential equations are obtained in terms of the mid-plane displacement components and shear rotations using Hamilton's principle. The effects of axial tension and compression loads and stiffeners on the natural frequencies of the plate are investigated. Results indicate the tension loads and stiffeners will increase the natural frequencies while the compression loads reduce the natural frequencies. The buckling force of plate is computed by increasing the absolute value of compressive force until the first natural frequency tends to zero. Results of simple cases are compared with finding in the literature and a good agreement was achieved. Copyright © 2007 by ASME.

关键词： Natural frequencies

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Flexible wheeurail contact model for railway vehicle dynamics without pre-calculation

Flexible wheeurail contact model for railway vehicle dynamic...

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2007 ASME Rail Transportation Division Fall Conference

作者： Durali, Mohammad Salehi, S. Hassan Jalili, Mohammad Mehdi Center of Excellence for Design Robotics and Automation Mechanical Engineering Department Sharif University of Technology PO Box 11365-9567 Tehran Iran

ISBN: (纸本)9780791848005

An advanced method using progressive concept of geometrical correspondence is applied to create a new wheel/rail contact model based on virtual penetration theory. The geometry and contact mechanism are solved simultaneously because of the independency in a defined correspondence. The model takes the penetrated profiles of wheel and rail and also associated creeps as inputs, and produces driving contact forces as output. The advantage of this model is that it doesn't require pretabulation of rigid contact situation. The method allows calculating flexible, non-elliptical, multiple contact patches during integration of the model. Consequently the rails with substructures can vibrate separately from the vehicle in a flexible wheel/rail contact model. The simulation results indicate that this method can be used in various rail vehicle dynamic problems. Copyright © 2007 by ASME.

关键词： Rails

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Finite Element Model of SWCNT Under Hydrostatic Pressure

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AIP Conference Proceedings 2007年第1期929卷 82-88页

作者： A. Sakhaee‐Pour M. T. Ahmadian Center of Excellence in Design Robotics and Automation (CEDRA) Department of Mechanical Engineering Sharif University of Technology Tehran Iran

A finite element technique is used to mimic radial deformation of single‐walled carbon nanotubes under hydrostatic pressure. The elastic deformation of nanotubes is modeled via elastic beams. Properties of the beam element are evaluated by considering characteristics of the covalent bonds between the carbon atoms in a hexagonal lattice. Applying the beam model in a three dimensional space, the elastic properties of the nanotube in the transverse direction are evaluated. The effects of diameter and wall thickness on the radial and circumferential elastic moduli of zigzag and armchair nanotubes are considered. Results are in good agreement with molecular structural mechanics data in the literature.

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Chaos control of a sprott circuit using delayed feedback control: Experimental study

Chaos control of a sprott circuit using delayed feedback con...

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

作者： Kaveh Merat Hoda Sadeghian Hassan Salarieh Aria Alasty Center of Excellence in Design Robotics and Automation Department of Mechanical Engineering Sharif University of Technology Tehran Iran

In this paper a linear delayed feedback control is proposed and experimentally applied to eliminate chaos in a nonlinear electrical circuit which is known as Sprott circuit. The chaotic behavior of the system is suppressed by stabilizing one of its first order unstable periodic orbits (UPOs) by a controller designed based on so-called Pyragas method. The effectiveness of this method, firstly, is numerically investigated by stabilizing the unstable first order periodic orbit and then verified experimentally by a laboratory setup.

关键词： Chaos Feedback circuits Delay Feedback control Chaotic communication Control systems Communication system control Orbits Biological control systems Differential equations

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Genetic algorithm based optimization for Dual-Arm Cam-Lock robot configuration

Genetic algorithm based optimization for Dual-Arm Cam-Lock r...

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

作者： Kambiz Ghaemi Osgouie Ali Meghdari Saeed Sohrabpour Mehdi Salmani Jelodar Center of Excellence in Design Robotics and Automation (CEDRA) Sharif University of Technology Tehran Iran Head of Robotics Department Sepanta Robotics and AI Research Foundation

Cooperative systems have been extensively investigated in literature. Herein the criteria and implementation for finding the optimal configuration of the dual-arm cam-lock (DACL) robot manipulators at a specific point with the objective to optimize the applicable task-space force in a desired direction are addressed. The DACL robot manipulators are reconfigurable arms formed by two parallel cooperative manipulators. Some of their joints may lock into each other. Therefore, the arms normally operate redundantly. However, when higher structural stiffness is needed these two arms can lock into each other in specific joints and loose some degrees of freedom. The dynamics of the DACL robot is discussed and parametrically formulated. At a given point in the robot's workspace, considering the cooperatively applicable force by the arms, the optimum configuration is found under the geometrical constraints of the planar arms using genetic algorithm as a multi-objective optimizer.

关键词： Genetic algorithms Ellipsoids Arm Force measurement robotics and automation Robot kinematics Orbital robotics Manipulator dynamics Robotic assembly Master-slave

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Effect of centrifugal force on frequency characteristic of rotating hollow cylinders using a newly designed cylindrical super element

Effect of centrifugal force on frequency characteristic of r...

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2006 ASME International Mechanical Engineering Congress and Exposition, IMECE2006

作者： Bonakdar, M. Ahmadian, M.T. Center of Excellence in Design Robotics and Automation Sharif University of Technology Tehran Iran

ISBN: (纸本)0791837904

A sixteen node cylindrical super element is presented for evaluating the free vibration characteristics of a rotating laminated cylinder with conventional boundary conditions. It is shown that the natural frequencies are affected considerably when the centrifugal force is also taken into account. The vibration frequencies of rotating finite cylinder, obtained by conventional finite element are used to evaluate the accuracy of this approach. The special case of a stationary cylinder with zero spinning velocity is also considered as a check on this method. Results indicate only few number of cylindrical super elements are capable of predicting the natural frequency of the rotating cylinder within the same limit as many elements used in the conventional finite element method. Copyright © 2006 by ASME.

关键词： Cylinders (shapes)

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Dynamic analysis of orthotropic laminated composite plates under axial load on elastic foundation

Dynamic analysis of orthotropic laminated composite plates u...

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2006 ASME International Mechanical Engineering Congress and Exposition, IMECE2006

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

ISBN: (纸本)0791837904

In this paper, free vibration analysis of laminated composite plates is carried out using first shear deformation theory and finite element method. Effect of axial tension and compression forces on the natural frequencies of the structure is investigated. Applying elastic foundation under the laminated composite plates has enabled us to achieve desired frequencies. The displacements are based C0 - nine plate bending element and each node has three degree of freedom. The equations of motion are derived using Hamilton's principle. Results indicate the tension forces will increase the natural frequency while the compression force reduces the natural frequency. The buckling force of plate is computed by increasing the absolute value of compressive force until the natural frequency tends to zero. Dynamic of moving mass in a circular path on the laminated composite plate is also investigated. Displacement of plate center reveals a sinusoidal pattern in time. Copyright © 2006 by ASME.

关键词： Plates (structural components)

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