Loading...
Search for:
flexible-structures
0.007 seconds
Total 42 records
Multi-Scale Numerical Modeling of Two Phase Flow over Flexible Surface Micro-Structures
, Ph.D. Dissertation Sharif University of Technology ; Javadi, Khodayar (Supervisor)
Abstract
The present thesis investigates the micro-droplet dynamics in an inclined channel covered with flexible structures. For this purpose, the DPD (dissipative particle dynamics) method is used to study the behavior of particles present in the flow, including the droplet, the fluid around the droplet, and polymeric structures. This model leads to a more accurate representation of flow hydrodynamics and indicates the way for exploring and understanding complex fluid properties in real flows. The first part of the thesis deals with the dynamics of rising bubbles attached to a vertical wall under different wettability conditions. Even though bubbles rising freely in a liquid have extensively been...
Fractional Order Sliding Mode Controller (FOSMC) Design for Attitude Control of a Satellite with Coupled Rigid–Flexible Structures Using Fractional Order Transfer Function
, M.Sc. Thesis Sharif University of Technology ; Fathi Jegarkandi, Mohsen (Supervisor)
Abstract
With the development of fractional order calculus and more accurately modeling of physical phenomena, the problem of controlling these systems, by considering the uncertainties in the system, will become necessary and inevitable. In this thesis, the fractional order transfer function model of a satellite with Coupled rigid-flexible structures is used as the reference work of the research. To control this dynamical system, sliding mode control method, which is one of the robust control methods, has been used. It is clear that it is not possible to directly design a sliding mode controller for a transfer function. For this reason, a fractional order pseudo-state space model is first obtained...
Dynamic model of a mobile robot with long spatially flexible links
, Article Scientia Iranica ; Volume 16, Issue 5 B , 2009 , Pages 387-412 ; 10263098 (ISSN) ; Khorsandijou, S. M ; Sharif University of Technology
2009
Abstract
Using some agent variables, the general structure of the dynamic model of a spatial mobile robot with N long spatially flexible links and N revolute joints has been exposed. It is composed of a set of 5N + 6 nonlinear coupled partial differential motion equations under the influence of the boundary conditions. Non-conservative forces/moments have been neglected. While being considered, the general structure of the dynamic model will not change, but a few exciting/damping terms will arise within the agent variables. The base of the robot is an unconstrained rigid body in space and the links as 3D Euler-Bernoulli beams undergo tension-compression, torsion and two spatial bendings while elastic...
Inverse design of supersonic diffuser with flexible walls using a Genetic Algorithm
, Article Journal of Fluids and Structures ; Volume 22, Issue 4 , 2006 , Pages 529-540 ; 08899746 (ISSN) ; Ziaei-Rad, M ; Sharif University of Technology
2006
Abstract
An efficient algorithm for the design optimization of the compressible fluid flow problem through a flexible structure is presented. The methodology has three essential parts: first the behavior of compressible flow in a supersonic diffuser was studied numerically in quasi-one-dimensional form using a flux splitting method. Second, a fully coupled sequential iterative procedure was used to solve the steady state aeroelastic problem of a flexible wall diffuser. Finally, a robust Genetic Algorithm was implemented and used to calculate the optimum shape of the flexible wall diffuser for a prescribed pressure distribution. © 2006 Elsevier Ltd. All rights reserved
Precise position control of shape memory alloy actuator using inverse hysteresis model and model reference adaptive control system
, Article Mechatronics ; Volume 23, Issue 8 , December , 2013 , Pages 1150-1162 ; 09574158 (ISSN) ; Sayyaadi, H ; Sharif University of Technology
2013
Abstract
Position control of Shape Memory Alloy (SMA) actuators has been a challenging topic during the last years due to their nonlinearities in the governing physical equations as well as their hysteresis behaviors. Using the inverse of phenomenological hysteresis model in order to compensate the input-output hysteresis behavior of these actuators shows the effectiveness of this approach. In this paper, in order to control the tip deflection of a large deformation flexible beam actuated by an SMA actuator wire, a feedforward-feedback controller is proposed. The feedforward part of the proposed control system, maps the beam deflection into SMA temperature, is based on the inverse of the generalized...
Modeling of a nonlinear Euler-Bernoulli flexible beam actuated by two active shape memory alloy actuators
, Article Journal of Intelligent Material Systems and Structures ; Volume 22, Issue 11 , 2011 , Pages 1249-1268 ; 1045389X (ISSN) ; Salehi, H ; Sayyaadi, H ; Sharif University of Technology
2011
Abstract
There are two different ways of using shape memory alloy (SMA) wire as an actuator for shape control of flexible structures: it can be either embedded within the composite laminate or externally attached to the structure. As the actuator can be placed at different offset distances from the beam, external actuators produce more bending moment and, consequently, considerabnle shape changes with the same magnitude of actuation force compared with the embedded type. Such a configuration also provides faster heat transfer rate owing to convection, which is very important in shape control applications that require a highfrequency response of SMA actuators. Although combination and physics-based...
Analysis of a flexible beam actuated by two active SMA wires
, Article ASME 2010 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, SMASIS 2010, 28 September 2010 through 1 October 2010 ; Volume 1 , October , 2010 , Pages 661-672 ; 9780791844151 (ISBN) ; Sayyaadi, H ; Aerospace Division ; Sharif University of Technology
2010
Abstract
There are two ways of using SMAs as actuators for shape control of flexible structures; they can be either embedded within composite laminates or externally attached to the structures. Since the actuator can be placed at different offset distances from the beam, external actuators produce more bending moment and, consequently, more shape change. Such a configuration also allows introduction of fast convection cooling, very important in shape control applications that require a high-frequency response of SMA actuators. Although combination and modeling of externally-attached SMA actuator wires and strips have been widely considered by some researchers, these studies have some weaknesses that...
Numerical modeling of sloshing frequencies in tanks with structure using new presented DQM-BEM technique
, Article Symmetry ; Volume 12, Issue 4 , 2020 ; Feng, J ; Ghalandari, M ; Maleki, A ; Abdelmalek, Z ; Sharif University of Technology
MDPI AG
2020
Abstract
The sloshing behavior of systems is influenced by different factors related to the liquid level and tank specifications. Different approaches are applicable for the assessment of sloshing behavior in a tank. In this paper, a new numerical model based on the differential quadrature method and boundary element approaches is adopted to investigate the sloshing behavior of a tank with an elastic thin-walled beam. The model is developed based on small slope considerations of the free surface. The main assumption of fluid modeling is homogeneity, isotropy, inviscid, and only limited compressibility of the liquid. Indeed, the formulation is represented based on the reduced-order method and then is...
Vibration analysis of a new type of compliant mechanism with flexible-link, using perturbation theory
, Article Mathematical Problems in Engineering ; Volume 2012 , February , 2012 ; 1024123X (ISSN) ; Zohoor, H ; Kargarnovin, M. H ; Sharif University of Technology
2012
Abstract
Vibration analysis of a new type of compliant parallel mechanism with flexible intermediate links is investigated. The application of the Timoshenko beam theory to the mathematical modeling of the intermediate flexible link is described, and the equations of motion of the flexible links are obtained by using Lagrange's equation of motion. The equations of motion are obtained in the form of a set of ordinary differential equations by using assumed mode method theory. The governing differential equations of motion are solved using perturbation method. The assumed mode shapes and frequencies are to be obtained based on clamped-clamped boundary conditions. Comparing perturbation method with...
Speed control of servo drives with a flexible couplings using fractional order state feedback
, Article PEDSTC 2014 - 5th Annual International Power Electronics, Drive Systems and Technologies Conference ; 2014 , p. 25-30 ; Moghadam, B. E ; Sharif University of Technology
Abstract
Using elastic couplings in servo motor drives may lead to torsional oscillations which are usually extinguished by reducing the bandwidth of the control system as a countermeasure. A high performance servo drive however needs fast dynamic characteristics. The conventional controllers, such as PI controllers, may not be able to improve the dynamic response while keeping the system stable. Fractional order modeling offers a good framework for flexible structures such as two mass servo drives. In this paper, the dynamic response and stability of two-mass servo drive is improved using a fractional order controller. The fractional order controller allows increasing the phase margin of the system...
A fractional order model for steer-by-wire systems
, Article IECON Proceedings (Industrial Electronics Conference) ; 2009 , Pages 4161-4166 ; Afshang, H ; Sharif University of Technology
Abstract
The steer by wire system for vehicles has attracted much attention in recent years. Steer by wire systems provide many benefits in terms of functionality and at the same time present significant challenges too. It is essential to investigate the stability of steer by wire systems using a more sophisticated model rather than common approximated models. Fractional order modeling offers a good modeling framework for complex dynamical systems involving flexible structures such as multi-mass drives. In this paper a nonlinear fractional order model for steer by wire systems is presented
Position control of shape memory alloy actuator based on the generalized Prandtl-Ishlinskii inverse model
, Article Mechatronics ; Volume 22, Issue 7 , 2012 , Pages 945-957 ; 09574158 (ISSN) ; Zakerzadeh, M. R ; Sharif University of Technology
2012
Abstract
Hysteresis and significant nonlinearities in the behavior of Shape Memory Alloy (SMA) actuators encumber effective utilization of these actuator. Due to these effects, the position control of SMA actuators has been a great challenge in recent years. Literature review of the research conducted in this area shows that using the inverse of the phenomenological hysteresis models can compensate the hysteresis of these actuators effectively. But, inverting some of these models, such as Preisach model, is numerically a complex task. However, the generalized Prandtl-Ishlinskii model is analytically invertible, and therefore can be implemented conveniently as a feedforward controller for compensating...
Nonlinear analysis of a flexible beam actuated by a couple of active SMA wire actuators
, Article International Journal of Engineering, Transactions A: Basics ; Volume 25, Issue 3 , 2012 , Pages 249-264 ; 17281431 (ISSN) ; Zakerzadeh, M. R ; Sharif University of Technology
2012
Abstract
There are two different ways of using SMA wires as actuators for shape control of flexible structures; which can be either embedded within the composite laminate or externally attached to the structure. Since the actuator can be placed at different offset distances from the beam, external actuators produce more bending moment and, consequently, considerable shape changes with the same magnitude of the actuation force comparing to the embedded type. Such a configuration also provides fast convection which is very important in shape control applications that require a high-frequency response of SMA actuators. Although combination and modeling of externally-attached SMA actuator wires and...
Experimental parametric identification of a flexible beam using piezoelectric sensors and actuators
, Article Shock and Vibration ; Vol. 2014, Issue. 1 , 2014 ; ISSN: 1070-9622 ; Nobahari, H ; Kordkheili, S. A. H ; Sharif University of Technology
Abstract
Experimental system identification of a flexible beam based on sweep square excitation is studied. For the purpose of nonparametric identification, an excitation signal is conducted to evaluate the frequency response of the system. The experiment is designed to excite the beam using a piezo actuator, in a way to raise the chance of exciting first three natural modes. In order to find the best linear representation of the real system, two different identification methods are applied. First, autoregressive moving average eXogenous method is employed to identify the transfer function of the beam. Then, the identification is carried out using the subspace identification method to obtain the...
Utility of probability density evolution method for experimental reliability-based active vibration control
, Article Structural Control and Health Monitoring ; Volume 25, Issue 8 , 2018 ; 15452255 (ISSN) ; Pourtakdoust, S. H ; Sharif University of Technology
John Wiley and Sons Ltd
2018
Abstract
The utility of probability density evolution method for reliability-based active vibration control of a cantilevered flexible beam is experimentally investigated. In this respect, an optimal linear quadratic regulator (LQR) is utilized together with an observer to design an online full-state feedback controller. In order to design a well-performing controller and to simulate the controller performance, a system model is obtained via identification techniques. Reliability tests are consequently performed to verify the effectiveness of the presented reliability assessment method as a foundation for reliability-based control. Subsequently, a hybrid metaheuristic optimization scheme of...
On-line fault detection and isolation (FDI) for the exhaust path of a turbocharged SI engine
, Article ASME 2013 Dynamic Systems and Control Conference, DSCC 2013 ; Vol. 1 , 2013 ; ISBN: 9780791856123 ; Shahbakhti M ; Alasty, A ; Vossoughi, G ; Sharif University of Technology
Abstract
Detection and isolation of faults in the exhaust gas path of a turbocharged spark ignition (SI) engine is an essential part of the engine control unit (ECU) strategies to minimize exhaust emission and ensure safe operation of a turbocharger. This paper proposes a novel physics-based strategy to detect and isolate an exhaust manifold leakage and a closed-stuck wastegate fault. The strategy is based on a globally optimal parameter estimation algorithm which detects an effective hole area in the exhaust manifold. The estimation algorithm requires prediction of the exhaust manifold's input and output flows. The input flow is predicted by a nonlinear Luenberger observer which is analytically...
On-line fault detection and isolation (FDI) for the exhaust path of a turbocharged SI engine
, Article ASME 2013 Dynamic Systems and Control Conference, DSCC 2013 ; Volume 1 , 2013 ; 9780791856123 (ISBN) ; Shahbakhti, M ; Alasty, A ; Vossoughi, G ; Sharif University of Technology
2013
Abstract
Detection and isolation of faults in the exhaust gas path of a turbocharged spark ignition (SI) engine is an essential part of the engine control unit (ECU) strategies to minimize exhaust emission and ensure safe operation of a turbocharger. This paper proposes a novel physics-based strategy to detect and isolate an exhaust manifold leakage and a closed-stuck wastegate fault. The strategy is based on a globally optimal parameter estimation algorithm which detects an effective hole area in the exhaust manifold. The estimation algorithm requires prediction of the exhaust manifold's input and output flows. The input flow is predicted by a nonlinear Luenberger observer which is analytically...
Electrical equivalent circuit of multi-mode flexible beams with piezoelectric elements
, Article Journal of Intelligent Material Systems and Structures ; Volume 19, Issue 5 , 2008 , Pages 621-627 ; 1045389X (ISSN) ; Meghdari, A ; Sharif University of Technology
2008
Abstract
Surface mounted piezoelectric sensors and actuators on elastic structures are often connected to electrical networks. The coupled equations of motion of the elastic structure with piezoelectric elements are already well known. However, due to complex behavior of some electrical elements in the electrical network, it is not an easy task to obtain the integrated equations of the whole system. A good remedy for this problem is to take advantage of an equivalent electrical circuit (EEC) representation of the mechanical part, leading the entire system to be represented as an electrical circuit. In this study, the authors propose a new method for constructing the EEC. This method is based upon the...
Modeling and identification of highly maneuverable fighter aircraft dynamics using block-oriented nonlinear models
, Article Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering ; Volume 231, Issue 7 , 2017 , Pages 1293-1311 ; 09544100 (ISSN) ; Saghafi, F ; Sharif University of Technology
Abstract
In this paper, a new approach based on block-oriented nonlinear models for the modeling and identification of aircraft nonlinear dynamics is proposed. Some of the block-oriented nonlinear models are regarded as flexible structures, which are suitable for the identification of widely applicable dynamic systems. These models are able to approximate a wide range of system dynamics. In general, aircraft flight dynamics is considered as a nonlinear and coupled system whose dynamics - in addition to pilot control inputs - depend on the flight conditions such as Mach number and altitude, which cause the aircraft dynamics to have various operational points. In this study, three types of...
Hardware-in-the-loop optimization of an active vibration controller in a flexible beam structure using evolutionary algorithms
, Article Journal of Intelligent Material Systems and Structures ; Vol. 25, issue. 10 , 2014 , p. 1211-1223 ; Hosseini Kordkheili, S. A ; Afshari, S. S ; Sharif University of Technology
Abstract
In this study, active vibration control of a cantilevered flexible beam structure equipped with bonded piezoelectric sensor/actuators is investigated. The linear quadratic regulator technique together with an observer is adopted to design the controller as well as to provide the full-state feedback. Two different approaches are subsequently used for simultaneously integrated optimization of the controller and observer parameters. In the first approach, a linear experimental model of the system is obtained using identification techniques, and the optimization is then performed based on a computer simulation of the system. However, in the second approach, a hardware-in-the-loop optimization...