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    Design and experimental development of hexapod robot with fiberglass-fibercarbon composite legs

    , Article 6th RSI International Conference on Robotics and Mechatronics, IcRoM 2018, 23 October 2018 through 25 October 2018 ; 2019 , Pages 439-444 ; 9781728101279 (ISBN) Kebritchi, A ; Havashinezhadian, S ; Rostami, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2019
    Abstract
    Over the last few years, the universal number of legged robots has increased astonishingly in outdoor environments. In this paper, the design, and control of a new RHex robot named IRHex with innovative Fiberglass-Fiber carbon composite legs are described. IRHex is a six-legged robot-one actuator located at each hip-achieving mechanical uncomplicatedness that provides a reliable performance. In this investigation, the new material used for building IRHex legs was discovered after several tests on the effect of sequence and orientation of laminates in the composite. IRHex achieves robust locomotion using a computer board analyzing the data sent by the sensors and communicating to the ground... 

    An approximate method for the surge response of the tension leg platform

    , Article Journal of Marine Science and Application ; Vol. 13, issue. 1 , March , 2014 , p. 99-104 Shoghi, R ; Tabeshpour, M. R ; Sharif University of Technology
    Abstract
    The solution for the Duffing equation in a nonlinear vibration problem is studied in this paper. Clearly, in the case of the perturb parameter being a larger value, the traditional perturbation method is no longer valid but the Homotopy Perturbation Method (HPM) is applicable usually. HPM is used to solve the weak and strong nonlinear differential equations for finding the perturbed frequency of the response. The obtained frequencies via HPM and the approximate method have good accordance for weak and strong nonlinear differential equations. Additionally, the calculated responses by use of the approximate method are compared with the responses obtained from the Numerical method in the time... 

    Six-leg AC-AC fault tolerant converter with reduced extra-sensor number

    , Article International Review of Electrical Engineering ; Volume 6, Issue 1 , 2011 , Pages 132-138 ; 18276660 (ISSN) Shahbazi, M ; Poure, P ; Zolghadri, M. R ; Saadate, S ; Sharif University of Technology
    Abstract
    In order to prevent further damage and to provide the continuity of service of six-leg converter in case of open-switch fault, it is mandatory to perform fast fault detection and converter reconfiguration schemes. Extra sensors are needed to detect the faults rapidly. In this paper, a very fast FPGA-based fault detection scheme is presented that minimizes the number of additional voltage sensors. A six-leg fault tolerant converter topology without redundancy and with bidirectional power flow is studied. First simulations are carried out to evaluate the proposed fault detection principle and the fault tolerant converter topology. The fully digital control and the fault detection are... 

    Investigation of pitch motion portion in vertical response at sides of a Tension-Leg Platform

    , Article Journal of Marine Science and Application ; Volume 15, Issue 2 , 2016 , Pages 175-181 ; 16719433 (ISSN) Tabeshpour, M. R ; Malayjerdi, E ; Sharif University of Technology
    Harbin Engineering University 
    Abstract
    Tendons vertically moor Tension-Leg Platforms (TLPs), thus, a deep understanding of physical tendon stresses requires the determination of the total axial deformation of the tendons, which is a combination of the heave, pitch, and surging responses. The vertical motion of the lateral sides of the TLP is coupled with surge and constitutes a portion of the pitch motion. Tendons are connected to the sides of the TLP; hence, the total displacement of the lateral sides is related to the total deformation of the tendons and the total axial stress. Therefore, investigating the total vertical response at the sides of the TLP is essential. The coupling between various degrees of freedom is not... 

    Stability analysis of a CALM floating offshore structure

    , Article International Journal of Non-Linear Mechanics ; Volume 36, Issue 6 , 2001 , Pages 917-926 ; 00207462 (ISSN) Esmailzadeh, E ; Goodarzi, A ; Sharif University of Technology
    2001
    Abstract
    It has been shown that there exists the necessary and sufficient condition for the existence of stable periodic response for a type of catenary anchor leg mooring system, (CALM). The mathematical model shows that the governing equation of motion for the system is a non-linear parametric second-order ordinary differential equation. The above-mentioned conditions have been obtained using the Schauder's fixed-point theorem. The validity of the assumptions has been fully demonstrated by analyzing a few examples. © 2001 Elsevier Science Ltd  

    Modeling and Control of One-legged Somersaulting Robot

    , M.Sc. Thesis Sharif University of Technology Zabihi, Mehdi (Author) ; Alasty, Aria (Supervisor)
    Abstract
    Inspired by the agility of animal and human locomotion, the number of researchers studying and developing legged robots has been increasing at a rapid rate over the last few decades. In comparison to multi-legged robots, single-legged robots only have one type of locomotion gait, i.e., hopping, which represents a highly nonlinear dynamical behavior consisting of alternating flight and stance phases. Hopping motion should be dynamically stabilized and therefore, presents challenging control problems. A large fraction of studies on legged robots have focused on modeling and control of single-legged hopping machines. In this research, somersaulting is introduced as a kind of hopping motion for... 

    Second-order perturbation added mass fluctuation on vertical vibration of tension leg platforms

    , Article Marine Structures ; Volume 19, Issue 4 , 2006 , Pages 271-283 ; 09518339 (ISSN) Tabeshpour, M. R ; Golafshani, A. A ; Seif, M. S ; Sharif University of Technology
    2006
    Abstract
    Total motion in waves can be considered as a superposition of the motion of the body in still water and the forces on the restrained body. In this study the effect of added mass fluctuation on vertical vibration of tension leg platforms (TLP) in the case of vibration in still water for both free and forced vibration subjected to axial load at the top of the leg is presented. This effect is more important when the amplitude of vibration is large. Also this is important in fatigue life study of tethers. The structural model used here is very simple. Perturbation method is used to formulate and solve the problem. First- and second-order perturbations are used to solve the free and forced... 

    Surge motion passive control of TLP with double horizontal tuned mass dampers

    , Article International Journal of Acoustics and Vibrations ; Volume 26, Issue 1 , 2021 , Pages 4-8 ; 10275851 (ISSN) Tabeshpour, M. R ; Malayjerdi, E ; Sharif University of Technology
    International Institute of Acoustics and Vibrations  2021
    Abstract
    The tension leg platform (TLP) is comprised of a buoyant hull that holds the platform’s topside. A group of tendons under the columns connect the TLP to the foundation. The TLP is displaced in six degrees of freedom due to environmental loads. Tendons moor the TLP in vertical direction (heave and pitch). Surge amplitude (horizontal displacement) of TLP is greater than other degrees of freedom. Also heave motion is coupled with surge one. Therefore, it is important to introduce and implement a method to control and reduce displacement of the TLP in horizontal direction. In this paper, a passive control system (double horizontal tuned mass damper (TMD)) is used to mitigate the surge motion of... 

    Numerical and experimental study on dynamic responsemitigation of tension leg platform using tuned mass damper

    , Article Journal of Ship Research ; Volume 66, Issue 4 , 2022 , Pages 265-276 ; 00224502 (ISSN) Tabeshpour, M. R ; Nikmehr, L ; Sharif University of Technology
    Society of Naval Architects and Marine Engineers  2022
    Abstract
    Responseamplitudemitigationof theoffshorestructures like tensionlegplatform(TLP) is important since these structures are always exposed to environmental loads such as waves, andin thecaseofTLP, reduction in responseamplitudeofplatformcauses reduction in stress range in tendons; thiswould increase the fatigue life of tendons, and therefore, increases the structural safety. Also providing stable conditions for machinery and crew increases the efficiency and functionality of the platform. This article thus aims to investigate the possibility and effectiveness of applying tuned mass damper (TMD) as a passive structural control systemto suppress the surgemotion of TLP that is exposed to wave... 

    Model Test to Evaluate Behavior of Seastar Platform in Waves

    , M.Sc. Thesis Sharif University of Technology Kiany, Ali (Author) ; Tabeshpour, Mohammad Reza (Supervisor) ; Seif, Mohammad Saeed (Co-Advisor)
    Abstract
    Tension leg platforms (TLP) are vertically moored with reserved buoyancy used for drilling and production in deep waters. Pre-tensioned tendons controls the heave, pitch and roll motions due to marine currents and waves efficiently. Seastar platforms are new generation of tension leg platforms that are similar to spar platforms that has the advantages of TLP besides spar simultaneously. This platform is usually considered as an alternative for large and cost consuming platforms. Seastar has a cylindrical surface piercing hull that creates the required buoyancy along with three submerged additional bodies. Pre-tensioned cables are attached to platform through these three submerged bodies. The... 

    Model Test to Evaluate Behavior of Tension Leg Platform in Waves

    , M.Sc. Thesis Sharif University of Technology Razaghian, Amir Hosein (Author) ; Seif, Mohammad Saeid (Supervisor) ; Tabeshpour, Mohammad Reza (Co-Advisor)
    Abstract
    A Tension Leg Platform (TLP) can be difined as a vertically moored, buoyant and compliant platform, where the excess buoyancy of the platform maintains tension in the mooring system (tethers). This platform type is usually used for drilling in deep water and includes the following sections, foundation, tendons, risers, hull and deck which is the most important section in terms of hydrodynamic forces and weight. Enough initial tension can be used to inhibit vertical movement of the structure. one of The main properties of this oil platform is extraction at large oil fields. Body of TLP is consist of vertical column, horizontal circular or rectangular cross section Pantoons and circular... 

    Gait analysis of a six-legged walking robot using fuzzy reward reinforcement learning

    , Article 13th Iranian Conference on Fuzzy Systems, IFSC 2013 ; August , 2013 , Page(s): 1 - 4 ; ISBN: 9781479912278 Shahriari, M ; Khayyat, A. A ; Sharif University of Technology
    IEEE Computer Society  2013
    Abstract
    Free gait becomes necessary in walking robots when they come to walk over discontinuous terrain or face some difficulties in walking. A basic gait generation strategy is presented here using reinforcement learning and fuzzy reward approach. A six-legged (hexapod) robot is implemented using Q-learning algorithm. The learning ability of walking in a hexapod robot is explored considering only the ability of moving its legs and using a fuzzy rewarding system telling whether and how it is moving forward. Results show that the hexapod robot learns to walk using the presented approach properly  

    Spin ladder with anisotropic ferromagnetic legs in a transverse magnetic field

    , Article Journal of Physics Condensed Matter ; Volume 19, Issue 7 , 2007 ; 09538984 (ISSN) Japaridze, G. I ; Langari, A ; Mahdavifar, S ; Sharif University of Technology
    2007
    Abstract
    We have studied the ground-state phase diagram of a two-leg spin ladder with anisotropic ferromagnetic leg couplings under the influence of a symmetry-breaking transverse magnetic field by the exact diagonalization technique. In the case of antiferromagnetic coupling between legs we identified two phase transitions in the plane of magnetic field versus interchain coupling strength. The first corresponds to the transition from the gapped rung-singlet phase to the gapped stripe-ferromagnetic phase. The second represents the transition from the gapped stripe-ferromagnetic phase into the fully polarized ferromagnetic phase. © IOP Publishing Ltd  

    Comprehensive study on the results of tension leg platform responses in random sea

    , Article Journal of Zhejiang University: Science ; Volume 7, Issue 8 , 2006 , Pages 1305-1317 ; 10093095 (ISSN) Tabeshpour, M. R ; Golafshani, A. A ; Seif, M. S ; Sharif University of Technology
    2006
    Abstract
    Compliant offshore structures are used for oil exploitation in deep water. Tension leg platform (TLP) is a suitable type for very deep water. The nonlinear dynamic response of TLP under random sea wave load is necessary for determining the maximum deformations and stresses. Accurate and reliable responses are needed for optimum design and control of the structure. In this paper nonlinear dynamic analysis of TLP is carried out in both time and frequency domains. The time history of random wave is generated based on Pierson-Moskowitz spectrum and acts on the structure in arbitrary direction. The hydrodynamic forces are calculated using the modified Morison equation according to Airy's linear... 

    Simple model for exact heave motion of tension leg platform

    , Article WSEAS Transactions on Mathematics ; Volume 5, Issue 5 , 2006 , Pages 500-506 ; 11092769 (ISSN) Tabeshpour, M. R ; Golafshani, A. A ; Seif, M. S ; Sharif University of Technology
    2006
    Abstract
    In this paper the dynamic response of the leg of a tension leg platform (tether) subjected to the load simulated as ocean wave at the top of the leg is presented. The structural model is very simple but several complicated factors such as foundation effect, buoyancy and simulated ocean wave load are considered. Two continuous models are proposed to present the structural system and the mentioned effects. The problem is solved by means of non-harmonic Fourier expansion in terms of eigenfunctions obtained from a non-regular Sturm-Liouville system  

    Fault-tolerant five-leg converter topology with FPGA-Based reconfigurable control

    , Article IEEE Transactions on Industrial Electronics ; Volume 60, Issue 6 , 2013 , Pages 2284-2294 ; 02780046 (ISSN) Shahbazi, M ; Poure, P ; Saadate, S ; Zolghadri, M. R ; Sharif University of Technology
    2013
    Abstract
    Fast fault detection and reconfiguration of power converters is necessary in electrical drives to prevent further damage and to make the continuity of service possible. On the other hand, component minimized converters may provide the benefits of higher reliability and less volume and cost. In this paper, a new fault-tolerant converter topology is studied. This converter has five legs before the fault occurrence, and after fault detection the converter continues to function with four legs. A very fast fault detection and reconfiguration scheme is presented and studied. Simulations and experimental tests are performed to evaluate the structure requirements, the digital reconfigurable... 

    Perturbation nonlinear response of tension leg platform under regular wave excitation

    , Article Journal of Marine Science and Technology (Japan) ; 2017 , Pages 1-9 ; 09484280 (ISSN) Tabeshpour, M. R ; Shoghi, R ; Sharif University of Technology
    Abstract
    Conceptual discussion on highly nonlinear duffing type equation of surge motion of TLP gives a deep view on structural response under environmental loads with some simplifications. Such analytical response is a simple form that clarifies important points in behavior of the structure. This paper presents the dynamic motion responses of a TLP in regular sea waves obtained by applying three methods in time domain using MATLAB software. Surge motion equation of TLP is highly nonlinear because of large displacement and it should be solved with large perturbation parameter in time domain. In this paper, homotopy perturbation method (HPM) is used to solve highly nonlinear differential equation of... 

    IGBT open-circuit fault diagnosis in a Quasi-Z-source inverter

    , Article IEEE Transactions on Industrial Electronics ; Volume 66, Issue 4 , 2019 , Pages 2847-2856 ; 02780046 (ISSN) Yaghoubi, M ; Shokrollahi Moghani, J ; Noroozi, N ; Zolghadri, M. R ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2018
    Abstract
    In this paper, a fast and practical method is proposed for open-circuit (OC) fault diagnosis (FD) in a three-phase quasi-Z-source inverter (q-ZSI). Compared to the existing fast OC FD techniques in three-phase voltage-source inverters (VSIs), this method is more cost-effective since no ultra-fast processor or high-speed measurement is required. Additionally, the method is independent of the load condition. The proposed method is only applicable to Z-source family inverters and is based on observing the effect of shoot-through (SH) intervals on the system variables during switching periods. The proposed algorithm includes two consecutive stages: OC detection and fault location identification.... 

    Analytical investigation of nonlinear heave-coupled response of tension leg platform

    , Article Proceedings of the Institution of Mechanical Engineers Part M: Journal of Engineering for the Maritime Environment ; 2018 ; 14750902 (ISSN) Tabeshpour, M. R ; Hedayatpour, R ; Sharif University of Technology
    SAGE Publications Ltd  2018
    Abstract
    Having deep view in structural response of tension leg platform is important issue not only for response analysis but also for engineering design. Coupling between surge and heave motions of tension leg platform is such a problem. Here, tension leg platform motions are considered only in surge and heave degrees of freedom without pitch effect. The coupled term of heave is a nonlinear differential equation. Because the focus of this article is on this term, therefore, Duffing equation of motion in the surge direction is linearized. The wave forces are calculated using Airy’s wave theory and Morison’s equation, ignoring the diffraction effects. Current force also can be very important in... 

    Investigation of TLP behavior under tendon damage

    , Article Ocean Engineering ; Volume 156 , 15 May , 2018 , Pages 580-595 ; 00298018 (ISSN) Tabeshpour, M.R ; Ahmadi, A ; Malayjerdi, E ; Sharif University of Technology
    Elsevier Ltd  2018
    Abstract
    Exact calculation of stiffness matrix of TLP is important for investigation of its behavior in intact and tendon damage conditions and it is necessary to design a reliable TLP. A serious attention has been concentrated on this problem in API-RP-2T and various aspects of that such as dynamic and static behavior of TLP, tendon tensions after one tether failure. Also it has introduced safety factors in different loads and healthy conditions. This paper deals with effect of damage tendon condition of TLP on behavior and tensions of tendons in wave frequency range. Equilibrium of TLP is studied and stiffness matrix of TLP is derived in tendon damage condition. Wave loads and hydrodynamic...