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    Dynamic Modeling and Adaptive Controller design for Cooperative Flexible Manipulators to Grasp and Manipulation of an Object

    , M.Sc. Thesis Sharif University of Technology Hejrati, Mahdi (Author) ; Sayyaadi, Hassan (Supervisor)
    In a world where energy conservation is a critical topic, cooperative flexible manipulators will play an important role. Conventional robotic manipulators have been designed to have maximum stiffness to achieve both minimum vibration and good positioning accuracy of the end-effector, which causes more power consumption and reduced efficiency. Due to the high inertia of such arms, interaction with humans or sensitive environments is hazardous. On the other hand, Flexible Link Manipulators are designed to be lightweight, using lower energy and producing higher efficiency. Unfortunately, the link's flexibility increases vibrations and decreases the accuracy of the end-effector. Since, the... 

    Timoshenko versus Euler-Bernoulli beam theories for high speed two-link manipulator

    , Article Scientia Iranica ; Volume 20, Issue 1 , 2013 , Pages 172-178 ; 10263098 (ISSN) Zohoor, H ; Kakavand, F ; Sharif University of Technology
    In this paper, a two-link flexible manipulator is considered. For a prescribed motion, Timoshenko and Euler-Bernoulli beam models are considered. Using the Galerkin method, nonlinear equations of motion are solved. The Runge-Kutta method is employed for the time response integration method. A comparative study is made between the Euler-Bernoulli and Timoshenko beam models, with and without foreshortening effects. It is demonstrated that for two-link manipulators, both theories provide good models, and the results for both theories are very similar for all ranges of slenderness ratio. The findings suggest that for two-link manipulators with relatively high slenderness ratios, there is a... 

    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) Zohoor, H ; Khorsandijou, S. M ; Sharif University of Technology
    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... 

    Decentralized control of reconfigurable robots using joint-torque sensing

    , Article International Conference on Robotics and Mechatronics, ICROM 2015, 7 October 2015 through 9 October 2015 ; 2015 , Pages 581-585 ; 9781467372343 (ISBN) Yazdi Almodaresi, S. M ; Sharif University of Technology
    In this paper, a decentralized controller for trajectory tracking of modular and reconfigurable robot manipulators is developed. The proposed control scheme uses joint-torque sensory feedback; also sliding mode control is employed to make both position and velocity tracking errors of robot manipulators globally converging to zero. Proposed scheme also guarantees that all signals in closed-loop systems will be bounded. In contrast to some of prior works in this scheme, each controller uses a smooth law to achieve its purposes. In this method, each controller uses only local information for producing control law hence separated controller can be used to control each module of manipulator and... 

    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) Viliani, N. S ; Zohoor, H ; Kargarnovin, M. H ; Sharif University of Technology
    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... 

    A novel approach for robust control of single-link manipulators with visco-elastic behavior

    , Article 10th International Conference on Computer Modelling and Simulation, EUROSIM/UKSim2008, Cambridge, 1 April 2008 through 3 April 2008 ; 2008 , Pages 685-690 ; 0769531148 (ISBN); 9780769531144 (ISBN) Torabi, M ; Jahed, M ; Sharif University of Technology
    Overwhelming number of control laws has been studied for control of robot manipulators with rigid links and joints. However controllers designed under this assumption may not accurately control the manipulator link due to visco-elastic properties that appear in the link behavior. In this study, a novel approach for robust control of a single-link manipulator is presented to force the link to have rigid motions, while it has visco-elastic behavior. In this regard, initially robot dynamics is extracted, followed by the design of four appropriate controllers through the loop-shaping approach. The obtained model is first represented in state space, however later converted to transfer function... 

    Nonlinear robust adaptive Cartesian impedance control of UAVs equipped with a robot manipulator

    , Article Advanced Robotics ; Volume 29, Issue 3 , Feb , 2015 , Pages 171-186 ; 01691864 (ISSN) Sharifi, M ; Sayyaadi, H ; Sharif University of Technology
    Robotics Society of Japan  2015
    In this paper, a new nonlinear robust adaptive impedance controller is addressed for Unmanned Aerial Vehicles (UAVs) equipped with a robot manipulator that physically interacts with environment. A UAV equipped with a robot manipulator is a novel system that can perform different tasks instead of human being in dangerous and/or inaccessible environments. The objective of the proposed robust adaptive controller is control of the UAV and its robotic manipulators end-effector impedance in Cartesian space in order to have a stable physical interaction with environment. The proposed controller is robust against parametric uncertainties in the nonlinear dynamics model of the UAV and the robot... 

    Prescribed-time control for perturbed euler-lagrange systems with obstacle avoidance

    , Article IEEE Transactions on Automatic Control ; 2021 ; 00189286 (ISSN) Shakouri, A ; Assadian, N ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2021
    This paper introduces a class of time-varying controllers for Euler-Lagrange systems such that the convergence occurs at an arbitrary finite time, independently of initial conditions, and free of chattering. The proposed controller is based on a mapping technique and is designed in two steps: First, a conventional (obstacle avoidance) asymptotically stable controller is specified for the nominal system; then, by a simple substitution, a prescribed-time (obstacle avoidance) controller is achievable for the perturbed system. It is proved that the proposed scheme is uniformly prescribed-time stable for unperturbed systems and prescribed-time attractive for perturbed systems as it rejects... 

    Adaptive impedance control of UAVs interacting with environment using a robot manipulator

    , Article 2014 2nd RSI/ISM International Conference on Robotics and Mechatronics, ICRoM 2014 ; Oct , 2014 , p. 636-641 Sayyaadi, H ; Sharifi, M ; Sharif University of Technology
    In this paper, a nonlinear adaptive impedance controller is proposed for UAVs equipped with a robot manipulator that interacts with environment. In this adaptive controller, by considering the nonlinear dynamics model of the UAV plus the robot manipulator in Cartesian coordinates, all of model parameters are considered to be completely uncertain and their estimation is updated using an adaptation law. The objective of the proposed adaptive controller is the control of manipulator's end-effector impedance in Cartesian coordinates to have a stable physical interaction. The adjustable Cartesian impedance is a desired dynamical relationship between the end-effector motion in Cartesian... 

    High-precision impedance control method for flexible base moving manipulators

    , Article Advanced Robotics ; Volume 23, Issue 1-2 , 2009 , Pages 65-87 ; 01691864 (ISSN) Salehi, M ; Vossoughi, G. R ; Sharif University of Technology
    The general problem 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 (FBMMs) is rather new and is being considered. The dynamic of the manipulator is decomposed into slow and fast dynamics using the singular perturbation method. A new sliding mode impedance control (SMIC) method using an element on the end-effector is proposed for high-precision impedance control of FBMMs. The SMIC method as a robust impedance control law is derived for the slow dynamics. The asymptotic... 

    Adaptive multi-model sliding mode control of robotic manipulators using soft computing

    , Article Neurocomputing ; Volume 71, Issue 13-15 , 2008 , Pages 2702-2710 ; 09252312 (ISSN) Sadati, N ; Ghadami, R ; Sharif University of Technology
    Elsevier  2008
    In this paper, an adaptive multi-model sliding mode controller for robotic manipulators is presented. By using the multiple models technique, the nominal part of the control signal is constructed according to the most appropriate model at different environments. Adaptive single-input-single-output (SISO) fuzzy systems or radial basis function (RBF) neural networks, regarding their functional equivalence property, are used to approximate the discontinuous part of control signal; control gain, in a classical sliding mode controller. The key feature of this scheme is that prior knowledge of the system uncertainties is not required to guarantee the stability. Also the chattering phenomenon in... 

    Optimal control of robot manipulators using fuzzy interaction prediction system

    , Article 2006 IEEE International Conference on Robotics and Biomimetics, ROBIO 2006, Kunming, 17 December 2006 through 20 December 2006 ; 2006 , Pages 1071-1076 ; 1424405718 (ISBN); 9781424405718 (ISBN) Sadati, N ; Emamzadeh, M. M ; Sharif University of Technology
    In this paper, a new fuzzy coordination method based on Interaction Prediction Principle (IPP) is presented for the optimal control of robot manipulators. For this purpose, the robot manipulator is considered as a two-level large-scale system where in the first level, the overall system is decomposed into several subsystems. Each subsystem can include one or more consecutive links and joints. In the second level, a fuzzy interaction prediction system is introduced for coordination of the overall system where a critic vector is also used for evaluation of its performance. The simulation results of using the proposed novel approach ,for optimal control of robot manipulators, show its... 

    Optimal configuration of a 4-DOF dual-arm cam-lock manipulator

    , Article 31st Mechanisms and Robotics Conference, presented at - 2007 ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, IDETC/CIE2007, Las Vegas, NV, 4 September 2007 through 7 September 2007 ; Volume 8 PART B , 2008 , Pages 1101-1107 ; 0791848027 (ISBN); 9780791848029 (ISBN); 0791848094 (ISBN); 9780791848098 (ISBN) Osgouie, K. G ; Meghdari, A ; Sohrabpour, S ; Jelodar, M. S ; Sharif University of Technology
    The Dual-Arm Cam-Lock (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. In this paper, the dynamics of the DACL robot is discussed and parametrically formulated. On the other hand, the criteria and implementation of genetic algorithm (GA) to optimize the configuration of DACL robot manipulators at a specific point with the objective to maximize the cooperatively applicable task-space force in a desired... 

    A class of globally convergent velocity observers for robotic manipulators

    , Article IEEE Transactions on Automatic Control ; Volume 54, Issue 8 , 2009 , Pages 1956-1961 ; 00189286 (ISSN) Namvar, M ; Sharif University of Technology
    We present a method for global estimation of joint velocities in rigid manipulators. A class of velocity observers with smooth dynamics are introduced whose structure depend on freely selectable functions and gains giving the flexibility of achieving multiple design objectives at the same time. Unlike most methods, no a priori knowledge of an upper bound for velocity magnitude is used. An adaptive version of the observer is also presented to handle a class of structured uncertainties in manipulator model. Simulation example illustrates low noise sensitivity of the globally convergent observer in comparison with semi-globally convergent observers. © 2009 IEEE  

    Robust control of robotic manipulators based on -synthesis

    , Article 17th International Congress on Sound and Vibration 2010, ICSV 2010, Cairo, 18 July 2010 through 22 July 2010 ; Volume 1 , 2010 , Pages 525-532 ; 9781617822551 (ISBN) Moradi, H ; Bakhtiari Nejad, F ; Sadighi, M ; Ahmadian, M. T ; Sharif University of Technology
    A robotic manipulator is modelled as a cantilever rotating Euler-Bernoulli beam. Two dynamic transfer functions are derived to describe beam tip motion and angular rotation in terms of the desired angular rotation. Torque disturbance, imprecision in the payload mass, unknown properties of the manipulator link are sources of uncertainty. The objective is to achieve a desired angular rotation while the vibration of manipulator tip is suppressed. The control input of the system is an external driving torque. The -synthesis control approach is used and an H optimal robust controller is developed based on the DK-iteration algorithm. Results show that the designed controller guarantees the robust... 

    Active control of robotic manipulators vibration via feedback control

    , Article 17th International Congress on Sound and Vibration 2010, ICSV 2010, 18 July 2010 through 22 July 2010 ; Volume 1 , 2010 , Pages 464-471 ; 9781617822551 (ISBN) Moradi, H ; Bakhtiari Nejad, F ; Sadighi, M ; Alasty, A ; Sharif University of Technology
    In this paper, a robotic manipulator modelled as a cantilever rotating Euler-Bernoulli beam is considered. Control objective is achieving a desired angular rotation of the manipulator tip while its lateral vibration is suppressed. An external driving torque is the control input of the system. Two dynamic transfer functions are derived to describe beam tip motion and angular rotation in terms of the desired angular rotation. After state-space representation of the problem, an observer is designed to estimate state variables of the system. Then, a feedback control is designed for both regulation and tracking objectives. Eigenvalues are chosen such that an appropriate response is achieved while... 

    A fuzzy based model coordination for two-level optimal control of robot manipulators

    , Article Proceedings - International Conference on Tools with Artificial Intelligence, ICTAI, 9 November 2015 through 11 November 2015 ; Volume 2016-January , 2016 , Pages 1122-1128 ; 10823409 (ISSN) ; 9781509001637 (ISBN) Mollaie Emamzadeh, M ; Sadati, N ; Sharif University of Technology
    IEEE Computer Society  2016
    In this paper, a new fuzzy based Model Coordination (F-MC) strategy is proposed for hierarchical control of large-scale systems (LSS). To solve the overall problem with a two-level optimal control strategy, we first decompose the system into several sub-systems at the first level. Then, at the second level, a fuzzy coordinator will be used to predict the interaction between subsystems. The proposed fuzzy based coordination approach is applicable to all types of LSS. Although in this paper, an optimal control of a 2DOF robot manipulator, as a LSS, will be considered. The obtained results are compared with the centralized optimization  

    Fault diagnosis in robot manipulators in presence of modeling uncertainty and sensor noise

    , Article Proceedings of the IEEE International Conference on Control Applications, 8 July 2009 through 10 July 2009, Saint Petersburg ; 2009 , Pages 1750-1755 ; 9781424446025 (ISBN) Mohseni, S ; Namvar, M ; Sharif University of Technology
    In this paper, we introduce a new approach to fault detection and isolation for robot manipulators. Our technique is based on using a new simplified Euler-Lagrange (EL) equation that reduces complexity of the proposed fault detection method. The proposed approach isolates the faults and is capable of handling the uncertainty in manipulator gravity vector. It is shown that the effect of uncalibrated torque sensor measurement is asymptotically rejected in the detection process. A simulation example is presented to illustrate the results. © 2009 IEEE  

    An optimization-based approach to control of robotic manipulators

    , Article Proceedings - IEEE International Conference on Robotics and Automation, 12 May 2009 through 17 May 2009, Kobe ; 2009 , Pages 3347-3352 ; 10504729 (ISSN); 9781424427895 (ISBN) Mohajerin Esfahani, P ; Karimi-Ghartemani, M ; Namvar, M ; Sharif University of Technology
    This paper proposes a method to suboptimally tune the control parameters in a conventional Lyapunov-Based method which shares the same concept of control design with sliding mode approach as applied to the robot manipulators. Optimal tuning of such parameters involves handling of nonlinearities in system dynamics and cost functions, which makes the problem challenging. We propose a step-by-step numerical algorithm that select suboptimal parameters while ensuring system stability. The controller is, suboptimal due to the facts that (1) it is in the form of a Slotine-type sliding mode control, (2) the numerical recursive algorithm might fall into a local minimum, and (3) the controller... 

    On the first-order decoupling of dynamical equations of motion for elastic multibody systems as applied to a two-link flexible manipulator

    , Article Multibody System Dynamics ; Volume 5, Issue 1 , 2001 , Pages 1-20 ; 13845640 (ISSN) Meghdari, A ; Fahimi, F ; Sharif University of Technology
    An improved method for deriving elastic generalized coordinates is considered. Then Kane's equations of motion for multibody systems consisting of an arbitrary number of rigid and elastic bodies is presented. The equations are in general form and are applicable for any desired holonomic system. Flexibility in choosing generalized speeds in terms of generalized coordinate derivatives in Kane's method is used. It is shown that proper choice of a congruency transformation between generalized coordinate derivatives and generalized speeds leads to equations of motion for holonomic multibody systems consisting of an arbitrary number of rigid and elastic bodies. These equations are decoupled in...