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Sharif University of Technology
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  • Welcome to the Center of Excellence in Design, Robotics, and Automation (CEDRA).

    CEDRA is the premier applied research, education and technology center in IRAN.

    The main goal of this group is to develop the relationship between university and industry and it tries to fill the existent gap between them. Therefore the main activity of this team has been focused on researches about designing and manufacturing of industrial grade rescue robots.
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  • Research Projects

  • Minimum Control Effort Trajectory Planning and Tracking Control for Brachiation Robot

  • Seyyed Mohammad Hosseini Lavasani, Mohsen Norouzi and Ali Meghdari

    Abstract–The Brachiation robot is a kind of mobile robot that imitates the movement of a long-armed ape swinging from branch to branch. Unlike other robots where the gravity force is one of the difficulties which reduce the stability of the system, it helps this robot to use minimum control effort to move from a branch to another. Here, the brachiation robot is considered as a two degree of freedom underactuated system. The control of underactuated mechanical systems is a research topic that has been studied extensively during the past years.

    Here, as a new innovation, Pontryagin's minimum principle is used to obtain the optimal trajectories for two different problems. The first problem is “Brachiation between fixed branches with different distance and height” and the second is “Brachiating and catching the moving target branch”. Theoretical results show that the control effort in the proposed method is reduced by 25% in comparison with the “Target Dynamics” method which was proposed in prior articles for this robot. Two kinds of controllers, the PD and the Adaptive Robust, are investigated for tracking the proposed trajectories. These controllers have the capability to be used in systems which have uncertainty in the inertial parameters. Lastly, experimental results are included to validate the proposed controller for the CEDRA brachiation robot.
    • Swarm robotics
    • CEDRA brachiation robot.

    • Swarm robotics
    • The continuous movement of CEDRA brachiation robot between symmetric intervals.

    • Robot swarm
    • The movement of CEDRA brachiation robot on Ladder with Irregular Branches.

  • Swarm Robotic: an Experimental Investigation

  • Alireza Nemati, Mehdi Farshchi, Ali Meghdari

    In this study, an adaptive control scheme for multi-agent formation control is proposed. This control method is based on artificial potential functions integrated with adaptive fuzzy sliding mode control technique. We consider fully actuated mobile agents with completely unknown dynamics. An adaptive fuzzy logic system is used to approximate the unknown system dynamics. Sliding Mode Control (SMC) theory is used to force agents’ motion to obey the dynamics defined by the simple inter-agent artificial potential functions. Stability proof is given using Lyapunov functions, which shows the robustness of controller with respect to disturbances and system uncertainties. Simulation results are demonstrated for a multi-agent formation problem, illustrating the effectiveness of the proposed method. Experimental results are included to verify the applicability of the scheme for a test-bed of six real mobile robots.
    • Swarm robotics
    • Swarm of autonomous robots acting together

    • Robot swarm
  • Simulations of Surface Defects Characterization Using Force Modulation Atomic Force Microscopy

  • Hossein Nejat Pishkenari and Ali Meghdari

    Using FFM-AFM, characterization of sample defects by a recently developed gold coated AFM probe in air is investigated. In this research, an online imaging simulation of the probe and surface is performed, and the effects of the horizontal scan speed, and effective frequency set-point on the resulting images are illustrated. The excitation force amplitude adjustment based on the value of the effective oscillation frequency was made through a PID controller. The research results are beneficial in providing data on the mechanisms of sample damage and also on the relative stiffness of the different surface regions.
    • View of the model used in the construction of the tip-sample interaction force

    • The topography difference of the simulated Ag sample (with vacancy, Cu and Pb atoms) and a pure Ag sample

    • The effect of scan speed on the topography

    • The effect of set-point frequency on the topography

  • A Dynamic Object Manipulation Approach to Dynamic Biped Locomotion

  • Borhan Beigzadeh, Ali Meghdari (Advisor) and Majid Nili Ahmadabadi (Co-advisor, University of Tehran )

    In this study, we aim at an integrated approach to Dynamic Biped Walking (DBW) and Dynamic Object Manipulation (DOM) at an abstract level. To this end, we offer a unified and abstract concept with a dual interpretation as a DOM and as a DBW system. We validate the proposed approach by using a set of simulations on an illustrative case study and show how it can be used in modeling as well as design of planning and control algorithms for DOM and DBW systems.

    In the case study, we describe the proposed approach and show its dual interpretation by identifying the relations between 2D dynamic object manipulation of a disc using two planar manipulators and 2D dynamic object locomotion of lower part of a biped robot. More specifically, having obtained the equations of DOM, we change the boundary conditions of the problem in such a way that both radius and mass of the disc tend to infinity. Simultaneously, both size and mass of the manipulators' base, i.e. the planet earth, tend to some values in the order of human's body mass and dimension. Regarding these changes, we can transform DOM into DBW and vice versa.

    To test the proposed approach, a simple control strategy is introduced to handle impact between the manipulators (legs) and the object (the earth). In addition, a motion planning system is designed in such a way that the manipulators (legs) catch and throw the manipulated object (the earth) in appropriate configurations.

    In the simulations, we first simulate the manipulation of a disc both in the presence of disturbance and without any disturbance. Having obtained acceptable results, we then simulate the dynamic walking process. The biped robot is dropped on the ground from the height of 1.25 meter with the initial horizontal velocity of 2 meter per second. The robot finally reaches a semi-steady state of running. It can be observed that the robot's running style is not perfect which was expected as we have put no effort in optimization of the trajectory and the control parameters in this phase of our research. Also the robot cannot tolerate big disturbances ([-350N, 350N]) and falls. See figures below.
    • Manipulation and locomotion from an absolute point of view

    • Planar motion of the disc center | system without disturbance

    • FIG.7: Planar motion of the disc center | system with disturbance

    • Snapshots from one cycle of biped running | system without disturbance

    • Some Snapshots of the robot falling because of large disturbance

  • CEDRA Rescue Robot

  • Ali Meghdari, Hanif Mahboobi, Hossein Nejat Pishkenari, Saeid Bagheri, Amir Lotfi, Reza Karimi, Yaser Khalighi, Ali Baghani, Farshid Amiri

    Intelligent mobile robots and cooperative multi-agent robotic systems can be very efficient tools to speed up search and rescue operations. Rescue robots are also useful to do rescuing jobs in situations that are hazardous for human rescuers. They can enter gaps and move trough small holes that are impossible for humans and even trained dogs. Robots should explore in collapsed structure, extract the map, search for victims and report the location of victims in map and the way that rescue team can reach him/her. It can also place a small package containing food, drugs and a communication device near the victim.

    So the rescue robots for reaching to the above goals should have the following features and capabilities:
    • autonomously navigate through collapsed structures
    • find victims and ascertain their condition
    • produce practical maps of their locations
    • deliver real-time communications
    • identify hazards

    The CEDRA rescue robot has shown it's capabilities in international arenas. It achieved second place in international Robocop competition (in real rescue league) which was held in Padua, Italy. All team members are top and elite students from different departments of Sharif University of Technology (Mechanical, Electrical and Computer Engineering).

    • CEDRA Rescue Robot

    • CEDRA Rescue Robot

    • CEDRA Rescue Robot

    • CEDRA Rescue Robot

  • Molecular Dynamics Assisted Simulation of Nanoscale Effects in Nanomanipulation

  • Hanif Mahboobi and Ali Meghdari

    Nanomanipulation as a new emerging area enables one to precisely change, interact and control the nano-scale phenomena. A main consideration of nanomanipulation is that surface attraction forces are greater than gravitational forces at nanoscale. In other words, surface area properties dominate over volume properties. Currently, the modeling schemes are based on continuum mechanics approaches. Especially at the nano-scale (i.e. manipulation of fine nanoparticles with size of about 5nm) the physical and chemical phenomena have not been completely understood. Thus, the aim of this research is to conduct an atomistic investigation of physical interaction analysis of the manipulation tool (e.g. STM tip), and nano-scale objects for manipulation and positioning tasks. To perform this research Nose-Hoover dynamics and Sutton-Chen interatomic potential will be used to investigate the behavior of tip-particle-substrate system which is made from different transient metals.

    Expected Results and General Achievements:
    • Atomistic simulation of nanoscale interactions in tip-particle-substrate system as a framework for MD modeling of nanomanipulation
    • Better understanding of stick-slip, sliding and rolling behavior of the tip-particle-substrate system and their emergence condition
    • Better understanding of adhesion phenomenon in the tip-particle-substrate system and its feasibility as a nanomanipulation process (including the release approach)
    • Determining the tip and substrate materials' type effects on the success of manipulation process
    • Better understanding of the effects of surface roughness, vacancies and lubricants on nanomanipulation.
    • Improvements of nanomanipulation algorithms for ultra fine nanoparticles
      • Simulation of Nanoscale Effects in Nanomanipulation

    • Dynamic Analysis of a Lower Extremity Exoskeletal System to Assist Paraplegic Motion

    • Ali Selk Ghafari, Ali Meghdari and Gholam Reza Vosoughi

      This research seeks to develop an integrated research and virtual based framework for biomechanical analysis of a robotic exoskeletal system to assist paraplegic motion.

      The four main objectives are to...

      1. ...develop and evaluate a lower extremity musculoskeletal system containing eighteen musculo-tendon actuators per leg to provide biomechanical analysis of human daily activities
      2. an exoskeletal system actuations based on biomechanical analysis of muscle functions
      3. ...develop a dynamical model of the exoskeletal-musculoskeletal system to provide a simulation framework for biomechanical analysis of the augmentation system, and...
      4. ...employing a paraplegic patient conditions to simulate the movement. The proposed model is valuable for developing and testing hypotheses that would be impossible to test experimentally or improve our understanding of the human-machine interactions. The musculoskeletal model developed in this study is illustrated in figure below.
        • The musculoskeletal model

      • Robolens: A Clinical Surgery Assistant Robot

      • Alireza Mirbagheri,Farzam Farahmand and Ali Meghdari

        Laparoscopic surgery is a specific branch of Minimally Invasive Surgery (MIS) that is performed in the abdominal cavity. In this method "ROBOLENS" helps the surgeon by holding and moving the laparoscopic lens (camera) under his/her supervision during the surgical operation and acquires a stable view from the surgical site.

        It can be controlled by Voice commands or by a smart foot switch system.

        The project is accomplished and the robot has passed technical and clinical tests at the Imam Khomeini Hospital Complex, Tehran, Iran.
        • Robolens at the Imam Khomeini Hospital Complex

      • Design and Evaluation of a Novel Triaxial Isometric Trunk Muscle Strength Measurement System

      • Mahmood Reza Azghani, Farzam Farahmand and Ali Meghdari

        Maximal strength measurements of the trunk have been used to evaluate maximum functional capacity of muscles and the potential mechanical overload/overuse of the lumbar spine tissues in order to estimate the risk of developing musculoskeletal injuries. A new triaxial isometric trunk strength measurement system was designed and developed in the present study and its reliability and performance was investigated. The system consisted of three main revolute joints, equipped with torque sensors, which intersect at L5-S1 and adjustment facilities to fit the body anthropometry and accommodate both symmetric and asymmetric postures in both seated and standing positions. The dynamics of the system was formulated to validly resolve the moment generated by trunk muscles in the three anatomic planes. The optimal gain and offset of the system were obtained using dead weights based on the least square linear regression analysis. The R-square results of calibration for all loading courses of all joints were higher than 0.99 which indicated an excellent linear correlation. The results of the validation analysis of the regression model suggested that the mean absolute error and the root mean square error were less than 2% of the applied load. The maximum value of the minimum detectable change was obtained to be 1.63 Nm for sagittal plane torque measurement, 0.8% of the full scale load. The trial-to-trial variability analysis of the device using dead weights provided intraclass correlation coefficients of higher than 0.99, suggesting an excellent reliability. The cross-talk analysis of the device indicated maximum cross talks of 1.7% and 3.4% when the system was subjected to flexion/extension and lateral bending torques, respectively. The trial to trial variability of the system during in-vivo strength measurement tests resulted in good to excellent reliability, with intra-class correlation coefficients ranging from 0.69 to 0.91. The results of the maximum voluntary isometric torques exertion measurements for 30 subjects indicated a good agreement with the previously published data in the literature.
      • Sharif CEDRA Humanoid Robot

      • Ali Meghdari, Saeed Sohrabpour, Hossein Tamddoni, Farid Jafari, Ali Nezamoddini

        In this project a humanoid robot was designed which could dynamically walk. Furthermore, It had the ability to play football (detect and kick a ball). To synthesize a kicking pattern, various objectives such as retaining its balance even after the kick is done and reducing the undesired angular momentum using both hands and torso were considered. This kick pattern was designed so that a desirable ball velocity was achieved. Also the law of conservation of angular momentum was used to generate a less energy consuming trajectory.
      • CEDRA ROV

      • Principal investigators: G.R. Vossoughi, S. Bagheri Shouraki, A. Alasti
        Research Group: H. Borhan, M.H. Saghafi, H. Fiouz, S.Baiyat, H. Khasteh, B. Taheri

        Nowadays underwater ROVs are vastly used in activities, ranging from underwater monitoring and inspection to installation and repair. In many inspection and monitoring operations high and accurate maneuvering capabilities are required.

        Researching activities on the underwater ROVs at the center of Excellence in Design, Robotics and Automation of Sharif university of Tech. was initiated based on a grant from hi-tech industries center in 2005. The aim of this grant was the design and prototyping of an underwater ROV for inspection with accurate maneuvering capabilities for a depth of operation of 300 meter and a with a payload capability of 10 kg. This ROV is equipped with one thruster for depth control and 4 thrusters for the horizon maneuvers. The thrust-to-weight ratio in the horizontal plane is nearly 0.5. One of the issues in the accurate maneuvering of ROVs is robustness to uncertainties associated with the varying payloads and hydrodynamics behavior of the vehicle and the umbilical. Robust Control algorithms using sliding mode control and adaptive back stepping have been proposed and implemented. More recently a control algorithm for moving this vehicle has been designed which enable it to autonomously track a moving target using visual servoing.
          • CEDRA Climbing Robot

          • Principal investigators: S. Bagheri Shouraki, G.R. Vossoughi
            Research Group: M.R. Zakerzadeh, M. Tavakkoli

            Climbing robots have received much attention in recent years due to their potential applications in the construction and tall building maintenance, agricultural harvesting, highways and bridge maintenance, shipyard production facilities�etc. Research on pole climbing robots at Sharif University of Technology was initiated based on a grant from Tavanir Electric Research Center in 2003. The aim of this grant was the design and prototyping of a robot capable of maintaining the lighting system in the streets and highways. To this end conception, design, modeling, and prototyping of a multi-task pole climbing/manipulating robot capable of traveling along the lighting poles was initiated. The proposed hybrid manipulator consisted of a one-DOF serial mechanism and a 3-DOF planar 3-RPR parallel mechanism. This combination provides 2 translational and 2 rotational degrees of freedom for the pole climbing robot. This architecture provides a good solution for a pole climbing and manipulating robot which can travel along tubular structures with bends, branches and step changes in cross section. It is also able to perform manipulation, repair and maintenance tasks after reaching the target point on the structure. The proposed robots was built and successfully put to test in September 2005.
          • Ball and Plate

          • Mohsen Saadat, Milad Moarref

            The Ball and plate system is a generalization of the famous Ball and Beam benchmark. The latter is a two Degree of Freedom system consisting of a ball that can roll on a rigid beam, while the former is a four DOF system consisting of a ball that can roll freely on a rigid plate. The ball and plate system is an appropriate device for studying and educating modern control strategies at graduate level.

            The main characteristic of our ball and plate system is the novelty of its spatial parallel mechanism, which allows the plate to rotate about two perpendicular axes while maintaining a fixed point at the center of the plain. Moreover, both actuators are located on the base and thus minimize the inertia of the device. Other advantages of our mechanism are its high stiffness and negligible backlash.

            The ball's position is feedbacked by a commercial web-camera. The camera (not visible in the video) is located about 80 cm above the surface of the plate. A data acquisition card is used for transmitting signals between the central computer and sensors/actuators.

            A fuzzy gain scheduling PID controller is used for the experiments demonstrated in the video. The gains are tuned to work under large initial errors, i.e., when the ball bounces on the plate, and when both the position and velocity errors are very large. In the tracking experiment, the radius of the desired circle is 10 cm, the tracking velocity is about 9 centimeters per second, and the average tracking error is less than 1 cm.
          • Haptic Device Application in Virtual Persian Handwriting Training

          • Misagh Mansouri Boroujeni, Ali Meghdari

            Haptic Interfaces have been used as cooperative systems to reproduce and simulate human actions. The Haptic Interface (HI) can be used as a tool capable of interacting dynamically with the operator using haptic technology. By controlling the haptic interface and constraining it to move through the desired trajectory which is required for most of the training systems such as Hand Writing Learning System, Minimally Invasive Surgical Simulation, virtual welding training and gaming applications the users can easily interact with virtual environment through the sense of touch. Haptic device application in virtual Persian handwriting training was investigated in our Robotic Lab (CEDRA) in Sharif University of Technology. Two different modes of learning were chosen in terms of haptic learning system: full guidance and partial guidance. In full guidance the haptic device guides the user to follow recorded trajectory; whereas in partial guidance, a user can freely follow a pre-written path, but if the user deviates significantly, the forces automatically brings him/her back to the optimal displayed path. This system acts in a similar way as a teacher or instructor holding his trainee�s hand. In the first phase of this project after some introductions, partial guidance for virtual handwriting learning system was investigated, for the next phase of this project the trajectory playback using suitable PID and Neural Network controllers were used. Experimental results from the generated softwares also justify the practical methodology which was proposed for virtual handwriting training. The results from the both stages of learning reveal that this method can be useful alphabet learning tool for not only the novice student in the first years of primary school but also as a powerful tool for more advanced training, handicapped and blind people as well.
          • Laboratories

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            • Automatic Control Laboratory

            • Automatic Control Lab in Department of Mechanical Engineering has two main sections: Training Lab and Project Lab.

              Training Lab:
              In Training section a one unit credit course is offered for undergraduate senior students.Following experiment sets are available for design and analysis of control systems:
              • Thermal System Control
              • Process Control Simulator
              • DC Motor position and speed
              • Control set up
              • PID fault detection unit
              • Liquid Level Control
              • Fluid flow control set up
              • Pneumatic and Hydraulic control system kit

              Project Lab:
              In project Lab section, undergraduate and graduate students produce their own experiment set up. The produced test beds are mostly used in design and analysis of advanced control systems. Some of projects performed in this lab are:

              • Twin Propeller System:       Which is a coupled, 2 DOF, MIMO, nonlinear system with a considerable uncertainty in the input channels.
                MIMO Sliding Mode control and nonlinear QFT controls have been applied to this system.
              • Vertical Wind Tunnel:
                Fuzzy height control of a variable shape object in a vertical tunnel has been applied to this set up.
              • 2 DOF x-y Inverted Pendulum
              • Experimental Prototype of Anti-Sway Gantry Crane Control System
              • 4-Legged Walking Robot
              • Training Prototype of a Rotary Vector (RV) Speed Reduction System
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            • Mechatronics Laboratory

            • Mechatronics is the synergistic integration of mechanical engineering with electronics and intelligent computer control in the design and manufacture of products and processes. It is a relatively new concept relating to the design of systems, devices, and products aimed at achieving an optimal balance between basic mechanical structure and its overall control.

              Research and education at the Mechatronics lab help students gain a better understanding of the principals of electronics and to give them experience with instruments and methods used by technicians and electronic engineers. This lab provides the opportunity for the Mechanical Engineering students to experience working with electronic components and circuits and learn about their integration into microprocessor based electro-mechanical systems. FPGA programming, electronic instrumentation, computer (PC and Micro-controller based) interfacing and real-time control are some of the principles, which the students working in this lab are exposed to.


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            • Manufacturing and Measurement Laboratory

            • The CAD/CAE/CAM part of the lab is equipped with a CNC � 3axis milling machine. Some powerful computers provide the students various softwares for modeling of deformation processes as well as cad-cam simulations. A 30-ton hydraulic press provides the opportunity to exercise the physical modeling of metal-forming processes.

              Recent research activities:
              • Physical modeling of extrusion process
              • Determination of load and strain-stress in closed die forging using the Plasticine Technique.
              • Improvement of vibrational characteristics of auto motive parts by using epoxy fiberglass composites.
              • The influence of material properties on the shape and level of the forming limit diagrams.
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            • Robotics Instructional Laboratory

            • This laboratory is developed for instruction of robotics science and technology to undergraduate and graduate students. Laboratory facilities include two articulated 6 D.O.F and 5 D.O.F robot manipulators, vision systems, digital cameras, and various robotic projects designed and fabricated by students.


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            • Robotics Research Laboratory

            • This laboratory is equipped with a number of powerful personal computers running under Windows. All PCs are connected in a local network, and have access to the Internet. A number of major engineering software necessary for mechanical modeling, simulation, and analysis have been installed on these computers.

              Some researches which have been done are:
              • Kinematics /kinetics modeling and analysis of the human knee joints.
              • Force and impedance control of flexible robotics arms.
              • Modeling and simulation of jumping process of a two-legged robot.
              • Modeling and identification of an underwater vehicle equipped with a manipulator arm.
              • Stability analysis of mobile manipulators.
              • Design and fabrication of control system for an underwater ROV equipped with two D.O.F. manipulator.
              • Design and fabrication of a master/slave manipulator.
              • Visual servo control of a robotic arm in an underwater ROV.
              • Attitude control of micro-satellites.
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            • Project Workshop

            • Project workshop is a facility that supports the undergraduate engineering curriculum. This facility is a start-to-finish project center with various electro-mechanical devices and equipments that enables students to take their projects from the initial "idea stage" to the "final product and presentation stage". Students are trained to work in a team in order to complete their projects. Upon finalizing their design plans, the students apply their CAD skills to their project design on state-of-the-art PC�s. Once their design is complete, they use the machine shop to build a scaled model or prototype to test their design. CEDRA believes that it is important for the engineering students to be able to develop intuitive, practical skills through hands-on testing, and gain a feel for practical applications of their ideas. After fabricating and testing their prototypes, students can create their own computer and video presentations, or "burn" their own CD ROMs.
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            • Machine Shop

            • This is a shop dedicated to student use for fabricating design project components. The shop includes a variety of light machining equipment, hand tools, stock materials and hardware.

              The facility is used for fabricating of mechanical parts to be used in various research projects.
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            • Creativity in Design Laboratory

            • This is a unique facility intended to stimulate and help in growth of students� creative design ideas. The lab is used both for design courses and design competitions in undergraduate and graduate levels. The basic lab tools enable the students in realizing their creative ideas in the form of mockups or prototypes. Instructors help students in developing the ideas and also in choosing a proper fabrication method for their machines. The lab has equipments and bench space for 36 students at one time. It has hand and power tools for cutting, shaping, joining of simple work materials, as well as assembling them into the form of simple machines. The lab is also providing a number of working desks for graduate students working on automation projects.
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            • BioRobotics Laboratory 

            • No Description