Sharif Digital Repository

In this paper, the general research of impedance control is addressed for a robotic manipulator with a moving flexible base. Impedance control imposes a relation between force and displacement at the contact point with the environment. The concept of impedance control of flexible base moving manipulators (FBMM) is rather new and is being considered. The dynamic of manipulator is decomposed into slow and fast dynamics using singular perturbation method. New sliding mode impedance control method (SMIC), using an element on the end effector is proposed for high precision impedance control of FBMM. The sliding mode impedance control method as a robust impedance control law is derived for the... 

Flapping motions of flexible wings generate dynamic forces. These forces include aerodynamic forces and inertial forces due to angular acceleration of wing mass, that cause aeroelastic deformation of wings. In this thesis a method is presented by use of a software and some experimental test conditions to study elastic behaviors and aerodynamic forces of flexible wings. A high speed camera records motion of wings in hovering condition and then these images is processed with software to recognize deformations (such as deflection, torsion, etc.) and aerodynamic forces due to them. Afterwards aerodynamic model and deformations is combined for better modeling. Finally we can compare results with... 

In this work, we want to gain and analyze the dynamic equations of an open four bar mechanism with two flexible links and three flexible hinges. In continue, one of the applications of a 3-RRR mechanism has been mentioned and dynamic equations and angles behavior have been analyzed. The effect of hinge stiffnesses and their sequence has been investigated by using Hamilton principle. In addition, The behavior of the mechanism with flexible links has compared to the mechanism with non-flexible. At last, the results have been validated by ADAMS software.

 

Liquefaction-induced lateral spreading is a known cause of severe damages to deep foundations during past earthquakes. Lateral spreading often takes place in gently sloping grounds which consisted of saturated loose cohesionless soil deposits. Several researchers during recent years have been studying the behavior of piles and soil-pile interaction under lateral spreading but there are still many unknowns in this regard. Also with observing catastrophic damages during past earthquakes caused by lateral spreading, developing proper mitigation measures for existing vulnerable piles against this phenomenon is a necessary act. In the present research, the behavior of a 3x3 flexible pile group... 

Flapping wing vehicles produce aerodynamic forces through the flapping motion of their wings. A sample flapping wing mechanism is studied in this project, which propulsion system consists of a battery, a DC motor, a gearbox, a flapping mechanism and a flexible membrane wing. The purpose of this study is simulation of the whole propulsion system through identification and simulation of each sub-system. In the current research, after an introduction to the flapping wing vehicles, literature of the flapping vehicles is reviewed. By studying relevant articles, lack of a comprehensive simulation of all sub-systems is observed. So the goal of this research is obtaining an appropriate tool for... 

The land market is one of the most important markets in the economy. Land is a factor of production, store of value, and a major part of household’s portfolio. Although price of land is an essential information for institutions like municipalities whom tax the landlords, or for financial intermediaries like banks whom use the land as collateral, studies about price of land and its spatial and time variations are scrace in Iran. Furthermore, most of studies in other countries are usually based on inflexible OLS estimators. Thus, this study has two main contributions. First, to analyze the usefulness of hedonic modeling in explaining the price of land, utilizing a unique dataset for Tehran... 

One of the most efficient methods in stiffening tall buildings to withstand lateral loads such as wind loading is to link the shear resisting core to the exterior columns using outrigger trusses. Many tall buildings such as Taipei 101 have benefited from outriggers. In this system, the outriggers force the perimeter frame to take part in resisting the bending moment of the lateral load acting on the structure by developing axial restraining forces in the windward and the leeward columns of the perimeter frame and forming a resisting moment.Most of the present analytical methods have studied the performance of outrigger braced structures neglecting shear deformation of the shear wall core and... 

Considerable research work has been dedicated to the development of structural control systems to improve the performance of structures and reduce the casualties resulting from earthquakes. It is generally accepted that semi-active control systems result in better structural performance compared to what can be achieved using passive systems. However, it has been observed that the majority of the performance improvement obtained from semi-active control systems stems from the reduction of brace flexibility effects, rather than the control algorithm used. In this study, it is attempted to utilize this fact to improve the performance of passive control systems, or develop simple semi-active... 

In this thesis, the equations of motion of a beam with tip mass on flying support, based on Euler-Bernoulli and Timoshenko beam theories is derived. To attempt for having accurate model in high rotational speeds, stretch variable is considered and employed in the equations of motion. For a planar and a spatial rotating beam, equations of motion are lineralized and simulated. Finite Element Method and Newmark direct integration scheme are employed for the analysis of the governing equations. To support the numerical results, an experimental setup is designed and based on which different tests are performed. A cantilever beam on a flying support free to vibrate in three dimensions is... 

Flapping is one of the most usual solutions to produce aerodynamic lift and propulsive force in natural flights, in low Reynolds number. A sample flapping wing mechanism in which propulsion system consists of a battery, two very small DC electrical motors, two gearboxes, a flapping mechanism and flexible beams as wings is studied in this project.Different methods have been proposed to derive the governing equations of motion and simulate the flapping wing system. The main disadvantage of the previous proposed works is the lack of a comprehensive dynamical analysis of the complete system including its components.Therefore, the main objective of the present research is to propose an efficient... 

In this thesis, free vibration of composite conical sandwich panel with a flexible is presented. Simply supported boundary condition are applied on the face’s edge only. Hamilton principle and energy method are used to derive equilibrium equations. In the mathematical formulation higher-order sandwich panel theory (HSAPT) was used. First shear deformation theory (FSDT) is used for faces.
Core displacement in various directions is modeled by polynomial function with indeterminate coefficient. It is assumed that the core is able to sustain shear and in-plane stresses. Temprature and humidity effects are neglected. Equations solved using generalized differential quadrature (GDQ) method.... 

Nowadays, small and big businesses do their best to automate their business process by using a workflow management system. Therefore, these systems play a key role in IT. By expansion of the business and ever-changing rules and procedures of organization, the need for consecutive changes to workflow management systems arises. The most challenging part of this change is the state of running instances. Previous solutions put the challenges of migrating instances, dealing with their inconsistencies and runtime errors on the users. It is worth noting that there are a few tools which consider instance migrations, but most of them lack a comprehensive viewpoint. Related solutions are often based... 

By comparing the control systems, researcherstypically believe that the active systems of control have better performance than passive ones. However, the high costs and the required technology for their erection and maintenance have limited the use of active control systems. In order to improve the control system performance at lower costs, semi-active control systems were also considered. Their performance is based on creating the desired control force by changing the instrument characteristics.Moreover, recent researches have shown that the improved performance of these instruments in structures compared to passive control systems, are typically due to reducing the flexibility of the... 

Environmental flows are seldom independent of plants impact. Aquatic canopies are mostly submerged and flexible; this causes a significant impact on Hydrodynamics of flow and mixing structure. Experimental and analytical investigation of vertical mixing in vegetation canopies with flexible submerged vegetation is the aim of this study. Most of the previous studies on flexible submerged vegetation were conducted to study the transverse and longitudinal mixing. In this study, flexible submerged vegetation in the density range of 2.8% to 4.2% was used to study the vertical mixing.The concentration profiles at four separate stations were obtained by image processing. The results for the... 

In this thesis a model of mixed integer programming to find the optimal solution of bi-objective facility layout problem in flexible bay structure according to uncertainty in flow material among departments and closeness rating is represented. In a facility layout problem based on flexible bay structure, departments with unequal areas are allocated to parallel bays. Also each department can only be allocated in one bay. The Goals are to minimize material handling cost and to maximize closeness rating. Uncertainty in flow material and closeness rating are modeled by fuzzy numbers. Due to the high complexity of the presented model, exact methods are only able to respond to maximize of 9... 

Aeroelasticity analysis and prediction of wind turbines sturcture deformations are fundamental parts in their design. Increasing the size of wind turbine blades and development of Mega-watt sized wind turbines have enhanced the importance of these studies. In this study, the aeroelasticity analysis of a wind turbine blade has been done based on flexible multibody dynamics method. For this purpose, the modal approach has been used for modeling blade structure which has been considered as a flexible beam with bending and torsion degrees of freedom. The unsteady vortex lattice method has been used to calculate aerodynamic loads in order to combine with wind turbine blade structure model. Using... 

Control of two-arm flexible robot is studied in this research. The goal is to control the robot in order to carry a fluid tank installed in the top of the last arm, while the vibration of fluid must be damped. The equations governing the system are extracted by the energy method while Euler-Bernoulli beam is selected to model the elastic members. In order to develop the equations, all of the potential and kinematic energies due to rigid and elastic motions are calculated, then a proper controller is designed for the system to accomplish the considered missions. Since the system is classified as an under-actuated system, the exact feedback linearization method is not practical to control the... 

In this study, an effective method is developed for design of passive control systems using viscous fluid dampers, considering the flexibility of braces used for installation of dampers. Using control design spectra, this approach provides a way to easily determine the optimum properties of the control system without complicated calculations or iterations.In the fist part of this study, it is attempted to find the optimum damping ratio of system by using the input energy spectra of ground motions. First, the relations among the dissipated energy in viscous dampers the strucutre and control system properties and structural response is evaluated.A theorically exact relation is established... 

In the present study, the buckling of conical sandwich panel with composite faces and flexible core is investigated. At first, the nonlinear differential equations based on Donnell and Novozhilov theories with relevant boundary conditions for conical shells are derived using energy method and Hamilton principle. In the following, by applying adjacent-equilibrium criterion, the equations are linearized and the equations of conical shell are obtained. Then, the results obtained from these theories are compared, and based on the benefits and application domain of the theories, Novozhilov theory is selected to model composite faces of the sandwich panel. High-order sandwich theory is used for... 

Cogeneration technologies such as Combined Heat and Power (CHP) have promising features for providing the electrical energy that various industries require while reducing the emissions and other environmental impacts of these industries. Investments in CHP systems require substantial implementation costs followed by a relatively long period of recovering the invested capital through savings in utilities bills. Appropriate timing of CHP system investments can reduce capital expenses and enhance returns on investments. An appropriate investment valuation method is needed to identify the appropriate time to implement a given CHP system and to find the values of properly scheduled investments....