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mechanical-system
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Mechanical Systems Using Nonlinear State Feedback
, M.Sc. Thesis Sharif University of Technology ; Namvar, Mehrzad (Supervisor)
Abstract
Disturbance is one of the inseparable components of the mechanical systems which cannot be avoided. In these systems a number of inner and outer sources exist which are the cause of disturbance. Abrupt changes in torque, uncertainty in parameters, mechanical impulses and external forces on robot’s parts all can be mentioned as examples which introduce disturbance that affects the output of mechanical and robotic systems. Therefore, disturbance rejection is considered indispensable in robotic control systems. There are number of problems which are associated with disturbance rejection. In several methods, mostly optimization based methods, system fails to completely reject the disturbance and...
Design and Implementation of Nonsmooth Controller for Mechanical Systems under Nonholonomic Constraint
, M.Sc. Thesis Sharif University of Technology ; Namvar, Mehrzad (Supervisor)
Abstract
This thesis works on certain type of underactuated mechanical systems with nonholonomic constrain, namely wheeled robots.Since this robots has different types, this work focuses specifically on three-wheeled robot. At first we know kinematic characteristics of robot system and equations of motion.To control this system, at first we will change equations to chain form, then control it by using known methods. It will be shown that between the known methods for convergence to a fixed point,irregular transformation is the best way for control systems in chain form.Also, with dynamic feedback linearization we can control robot on a trajectory that has a continuous third order derivatives. Then...
Nonlinear Geometric Approach to Fault Detection in Mechanical Systems
, M.Sc. Thesis Sharif University of Technology ; Namvar, Mehrzad (Supervisor)
Abstract
The demand for safety operating systems is growing with the new developments in technology. One of the important and critical issues in system monitoring is the capability of the system to detect probable faults and hazards. In model-based fault detection one specific diagnostic signal called residual should be generated for each fault that is only sensitive to a particular fault and independent of other faults and disturbances. In this thesis we try to investigate the nonlinear geometric approach in fault detection of a class of mechanical systems. After a brief introduction to geometric tool for nonlinear inputaffine systems and conditions in which output is decoupled from input, we...
Heat transfer between micro- and nano-mechanical systems through optical channels
, Article Journal of the Optical Society of America B: Optical Physics ; Vol. 31, issue. 7 , 2014 , pp. 1525-1532 ; ISSN: 07403224 ; Bahrampour, A. R ; Sharif University of Technology
Abstract
In this paper, a new mechanism of heat transfer is introduced. It is shown that, without emission and absorption of photons, light can operate as a channel of heat transfer between nano- or micro-mechanical oscillators. We consider the dynamics of two vibrating mirrors coupled through one optical cavity mode in an optomechanical system. It is shown that light mediates heat transfer between two micro-mirrors. When the detuning frequency of the mechanical resonators is low, fluctuations flow through the light channel from the high temperature vibrating mirror toward the low temperature one. This behavior is named the resonance heat transfer effect. The rate of heat flow between the mechanical...
Fano resonance in optomechanical systems with two movable mirrors
, Article Optics InfoBase Conference Papers ; 18- 20 March , 2014 ; ISSN: 21622701 ; ISBN: 9781557529954 ; Bahrampour, A ; Sharif University of Technology
Abstract
We investigate the Fano profile in an optomechanical system with two vibrating mirrors. The detuning between their mechanical frequency, leads to the occurrence of double Fano resonances. The Fano profile can be controlled by adjusting the cavity parameters
Investigation of thermal effects on machining chatter based on FEM simulation of chip formation
, Article CIRP Journal of Manufacturing Science and Technology ; Vol. 7, issue. 1 , 2014 , p. 1-10 ; Movahhedy, M. R ; Moradi, H ; Sharif University of Technology
Abstract
In this paper, thermo mechanical finite element analysis of orthogonal machining process with a flexible tool is carried out to study the dynamic behaviour of the machining system and its stability against chatter vibration. By combining the simulation of chip formation in metal cutting with the dynamic phenomena leading to chatter development, the influence of various phenomena, including thermal effects resulting from friction and plastic deformations on the stability of the process are investigated. The novelty of this model is in its ability to evaluate the effect of temperature rise in the cutting zone on the stability of cutting process. Process stability is analyzed and compared for...
Nonlocal and strain gradient based model for electrostatically actuated silicon nano-beams
, Article Microsystem Technologies ; Vol. 21, Issue 2 , 2014 , pp. 457-464 ; Online ISSN: 1432-1858 ; Yousefi-Koma, A ; Pishkenari, H. N ; Sharif University of Technology
Abstract
Conventional continuum theory does not account for contributions from length scale effects which are important in modeling of nano-beams. Failure to include size-dependent contributions can lead to underestimates of deflection, stresses, and pull-in voltage of electrostatic actuated micro and nano-beams. This research aims to use nonlocal and strain gradient elasticity theories to study the static behavior of electrically actuated micro- and nano-beams. To solve the boundary value nonlinear differential equations, analogue equation and Gauss–Seidel iteration methods are used. Both clamped-free and clamped–clamped micro- and nano-beams under electrostatical actuation are considered where...
Functional process capability analysis in mechanical systems
, Article International Journal of Advanced Manufacturing Technology ; Vol. 73, issue. 5-8 , July , 2014 , p. 899-912 ; 02683768 ; Movahhedy, M. R ; Sharif University of Technology
Abstract
Functional quality in the mechanical products is governed mainly by the degree of satisfaction of the design requirements, which itself depends on the variations in the effective variables. The functional parameters cannot be easily measured in mass production, and thus, are not usually considered as a direct inspection objective. Process capability indices are useful tools for evaluating the ability of a process to produce the dependent variables of a product that meet certain specifications. In this paper, the conventional process capability concept is extended to develop a computational tool for analysis of the functional quality of a mechanical product. Through defining new proper...
Operation of an opto-mechanical system using a double-cell design for liquid color recognition
, Article Optics and Lasers in Engineering ; Volume 51, Issue 7 , July , 2013 , Pages 848-855 ; 01438166 (ISSN) ; Sharif University of Technology
2013
Abstract
Design and operation of an opto-mechanical system employing a double-cell is reported here for the color liquid reflection studies. The reported system consists of a double-fiber optical design and an electro-mechanical scanning system. In this arrangement one fiber transmits the source light to the object surface and the second one transmits the light reflected from the sample to a photodetector. By scanning the double-fiber assembly in one-direction reflection properties of different color liquids are investigated. Reflection signals depend on the cell surface structure and the cell filled material. Two sets of flat/cylindrical cells made of almost similar glass materials are used for this...
Effects of optical parametric amplifier pump phase noise on the cooling of optomechanical resonators
, Article Journal of the Optical Society of America B: Optical Physics ; Volume 30, Issue 7 , 2013 , Pages 1898-1904 ; 07403224 (ISSN) ; Bahrampour, A. R ; Sharif Univeristy of Technology
2013
Abstract
In this paper, the effect of parametric amplifier pump phase noise on the cooling of a micromirror in an optomechanical system with an optical parametric amplifier inside the optical cavity is investigated theoretically. It has been demonstrated that the photon number distribution of a parametric amplifier near the threshold of instability leads to improved cooling of the micromirror. But due to the presence of the parametric amplifier, there is a resonance detuning frequency for transferring noise energy to the potential and kinetic energy fluctuations of the mirror which causes the mirror mechanical oscillation mode temperature to increase. In low quality factor cavities, this effect...
Electromechanical resonator based on electrostatically actuated graphene-doped PVP nanofibers
, Article Nanotechnology ; Volume 24, Issue 13 , 2013 ; 09574484 (ISSN) ; Mohammadi, S ; Zad, A. I ; Sarvari, R ; Shariat Panahi, S. P ; Jokar, E ; Sharif University of Technology
2013
Abstract
In this paper we present experimental results describing electrical readout of the mechanical vibratory response of graphene-doped fibers by employing electrical actuation. For a fiber resonator with an approximate radius of 850 nm and length of 100 m, we observed a resonance frequency around 580 kHz with a quality factor (Q) of about 2511 in air at ambient conditions. Through the use of finite element simulations, we show that the reported frequency of resonance is relevant. We also show that the resonance frequency of the fiber resonators decreases as the bias potential is increased due to the electrostatic spring-softening effect
Treatment of the small time instability in the finite element analysis of fluid structure interaction problems
, Article International Journal for Numerical Methods in Fluids ; Volume 71, Issue 6 , 2013 , Pages 756-771 ; 02712091 (ISSN) ; Movahhedy, M. R ; Sharif University of Technology
2013
Abstract
In this paper, the fluid-structure interaction problem in mechanical systems in which a high frequency vibrating solid structure interacts with the surrounding fluid flow is considered. Such a situation normally appears in many microelectromechanical systems like a wide variety of microfluidic devices. A different implementation of the residual-based variational multiscale flow method is employed within the arbitrary Lagrangian-Eulerian formulation. The combination of the variational multiscale method with appropriate stabilization parameters is used to handle the so-called small time step instability in the finite element analysis of the fluid part in the coupled fluid-structure interaction...
Quantum optomechanics in the bistable regime
, Article Optics InfoBase Conference Papers, 6 June 2011 through 8 June 2011, Ottawa ; 2011 ; 21622701 (ISSN) ; 9781557529282 (ISBN) ; Kleckner, D ; Pepper, B ; Bahrampour, A ; Bouwmeester, D ; Simon, C ; Sharif University of Technology
2011
Abstract
We have studied the simplest optomechanical system close to and in the bistable regime. We find that Optomechanical entanglement is particularly strong in this regime for large enough detuning. The robustness of entanglement against temperature is also studied
Two-level control scheme for stabilisation of periodic orbits for planar monopedal running
, Article IET Control Theory and Applications ; Volume 5, Issue 13 , Sept , 2011 , Pages 1528-1543 ; 17518644 (ISSN) ; Dumont, G. A ; Hamed, K. A ; Gruver, W. A ; Sharif University of Technology
2011
Abstract
This study presents an online motion planning algorithm for generating reference trajectories during flight phases of a planar monopedal robot to transfer the configuration of the mechanical system from a specified initial pose to a specified final one. The algorithm developed in this research is based on the reachability and optimal control formulations of a time-varying linear system with input and state constraints. A two-level control scheme is developed for asymptotic stabilisation of a desired period-one orbit during running of the robot. Within-stride controllers, including stance and flight phase controllers, are employed at the first level. The flight phase controller is a feedback...
Comparison of LMPs' Sensitivity under Payment Cost Minimization and Offer Cost Minimization Mechanisms
, Article IEEE Systems Journal ; Volume 9, Issue 4 , January , 2015 , Pages 1507-1518 ; 19328184 (ISSN) ; Hosseini, S. H ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015
Abstract
There are different choices for auction and settlement mechanisms in electricity markets; however, selecting the appropriate mechanisms is too hard. Traditionally, the offer cost minimization (OCM) mechanism that minimizes the total offer cost is used as the clearing mechanism, and payments are calculated based on locational marginal prices (LMPs). Under this setup, the clearing and settlement mechanisms are inconsistent, since the minimized cost is different from the total payment cost. Some recent studies have proposed the payment cost minimization (PCM) mechanism. However, the discussion is still open, and different aspects of these mechanisms are yet needed to be analyzed. This paper...
Study of nonlinear dynamics and chaos in MEMS/NEMS resonators
, Article Communications in Nonlinear Science and Numerical Simulation ; Volume 22, Issue 1-3 , May , 2015 , Pages 611-622 ; 10075704 (ISSN) ; Yousefi Koma, A ; Pishkenari, H. N ; Tajaddodianfar, F ; Sharif University of Technology
Elsevier
2015
Abstract
With the successes in numerous applications from signal filtering to chemical and mass sensing, micro- and nano-electro-mechanical resonators continue to be one of the most widely studied topics of the micro-electro-mechanical systems community. Nonlinearities arising out of different sources such as mid-plane stretching and electrostatic force lead to a rich nonlinear dynamics in the time response of these systems which should be investigated for appropriate design and fabrication of them. Motivated by this need, present study is devoted to analyzing the nonlinear dynamics and chaotic behavior of nano resonators with electrostatic forces on both sides. Based on the potential function and...
Clearance effects on dynamic behavior of a continuous mechanical system
, Article JVC/Journal of Vibration and Control ; Volume 21, Issue 13 , October , 2015 , Pages 2509-2519 ; 10775463 (ISSN) ; Momeni Massouleh, S. H ; Khorasani, R ; Sharif University of Technology
SAGE Publications Inc
2015
Abstract
An analytical modified method is presented to investigate the clearance effects on the dynamic behavior of cantilever beams. In this work, apart from clearance, all other nonlinearities are avoided to be considered during the analytical solution. The beam is idealized using an equivalent single-degree-of-freedom structure. A tri-linear stiffness system is also adopted to simulate the beam together with the clearance. Subsequently the analytical solution is derived for a cantilever beam structure with and without considering structural damping. The experimental method is employed to verify the results from the presented analytical solutions. It is noted that the results obtained by the...
A speed-dependent variable preload system for high speed spindles
, Article Precision Engineering ; Volume 40 , April , 2015 , Pages 182-188 ; 01416359 (ISSN) ; Movahhedy, M. R ; Sharif University of Technology
Elsevier Inc
2015
Abstract
High speed machine tools are required to operate in a wide range of spindle rotational speeds with high stiffness and high accuracy. The stiffness of the spindle is largely dependent on the axial preload of the angular contact bearings. A large preload is required at lower range of speeds to provide sufficient stiffness for vibration-free heavy cutting. However, at higher speeds, it results in rapid temperature rise and reduces the life of the bearing. For optimum performance, it is essential that the bearing preload is reduced as the rotational speed increases. In this paper, an automatic variable preload system is proposed that changes the preload on the bearings as a function of...
Generation of motional entangled coherent state in an optomechanical system in the single photon strong coupling regime
, Article Journal of Modern Optics ; Volume 62, Issue 19 , Jul , 2015 , Pages 1685-1691 ; 09500340 (ISSN) ; Shakeri, S ; Hamidi, O ; Zandi, M. H ; Bahrampour, A ; Sharif University of Technology
Taylor and Francis Ltd
2015
Abstract
The single-photon strong coupling in the deep-resolved sideband of the optomechanical system induces photon blockade (PB) effect. For the PB cavity, an initial mechanical coherent state evolves into superposition of phonon cat states entangled with the cavity Fock states. Measurement of the cavity photon number states produces phonon even and odd cat states. The information leakage effect of two photon states on the fidelity of cat states is calculated, it is shown that for low average phonon number this effect is negligible and decreases by increasing the two photon cavity state. The Lindblad equation is solved numerically to obtain the environmental effects on the fidelity of cat states
Classification of the nonlinear dynamics in an initially curved bistable micro/nanoelectro-mechanical system resonator
, Article Micro and Nano Letters ; Volume 10, Issue 10 , Oct , 2015 , Pages 583-588 ; 17500443 (ISSN) ; Hairi Yazdi, M. R ; Nejat Pishkenari, H ; Maani Miandoab, E ; Ouakad, H.M ; Sharif University of Technology
Institution of Engineering and Technology
2015
Abstract
The nonlinear dynamics of a bistable micro/nano-electro-mechanical system resonator composed of an arch-shaped microbeam is investigated. The initially curved microbeam is actuated through a combined DC and AC electrostatic parallel plate field. A single degree of freedom model obtained using the Galerkin's decomposition method with distributed electrostatic force is implemented in order to investigate the resonator dynamics near its primary resonance. According to the shape of the potential energy function which depends on the system parameters, the nonlinear dynamics of the system are classified into certain categories. The appearance of various nonlinear phenomena including dynamic...