Mechanical Engineering / Makina Mühendisliği

Permanent URI for this collectionhttps://hdl.handle.net/11147/4129

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2012 - 20185

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  • Conference Object
    A Continuously Variable Transmission System Designed for Human-Robot Interfaces
    (IFToMM, 2018) Mobedi, Emir; Dede, Mehmet İsmet Can
    Continuously Variable Transmission (CVT) systems are being used for many applications such as automotive transmissions, robotics, aerospace. In an ideal condition, these systems have the potential to provide continuously varying power transmission within a predefined limit. This transmission is accomplished with the help of friction, belt or gear systems. CVT can find application in a human-robot interface if design criteria such as backdrivability, independent output position and impedance variation, shock absorbing and low mass and inertia can be satisfied. Even if there are various CVT designs in the literature for human-robot interfaces, the primary limitation of the two-cone drive CVT designs is that the output torque and the output position cannot be altered independently. The reason for this problem is that the friction wheel, which is designed to transmit the torque from the input cone to the output cone, gives rise to remarkable longitudinal friction force along the linear way. In order to overcome this problem, a sphere is used in this work for the CVT design as the transmission element. In addition, it is stated in the literature that common CVT drive systems do not have the capability to be used in cyclic bidirectional motion. In the presented CVT design, a second sphere is added to the system with two springs from the lower part of the cones for pre-tension in order to solve the bidirectional transmission problem. In this paper, the working principle and conceptual design details of the novel two-cone CVT drive are presented. Experimental results showed that the novel CVT has the capacity to transmit bidirectional power with some accuracy.
  • Conference Object
    Citation - Scopus: 1
    Trajectory Planning for a Redundant Planar Laser-Cutting Machine With Macro-Micro Manipulation
    (IFToMM, 2015) Uzunoğlu, Emre; Dede, Mehmet İsmet Can; Kiper, Gökhan
    Kinematic redundancy in robots provide the control designer with infinite number of possibilities for improving the process for a selected target optimization criterion. A special type of kinematic redundancy is devised by using kinematically different two mechanisms with different advantages. In this case, the control design including the trajectory planning should be devised taking into account the distinct advantages of both mechanisms. In this work, a macro mechanism with larger workspace is used along with a micro mechanism that has higher dynamics and lower inertia. A trajectory planning algorithm integrated with the control structure making use of the previously defined advantages of both mechanisms is explained in this paper. A case study is provided to validate the developed algorithm.
  • Conference Object
    Citation - WoS: 1
    Citation - Scopus: 7
    Use of Hidden Robot Concept for Calibration of an Over-Constrained Mechanism
    (IFToMM, 2015) Kiper, G.; Dede, M. I. C.; Uzunoglu, E.; Mastar, E.
    Overconstrained mechanisms prove useful in applications where high stiffness and low weight is required against high amount of forces while keeping high precision. This study issues a planar two degrees-of-freedom overconstrained parallel manipulator for positioning the end-effector with high acceleration values (>5g) with a positioning precision in the order of 30 inn. Since the manufacturing errors were compatible with the end-effector positioning errors, it was required to perform some system identification before the precision and repeatability tests. For the system identification, the end-effector position and motor input values are recorded. However, since the mechanism is overconstrained, the link lengths could not be obtained due to the lack of analytical inverse kinematics solution. In order to cope with this problem, the hidden robot concept is utilized in order to fit a simple kinematic model between the task space and the joint space of the manipulator. Further calibration studies are carried out using the error correction matrix. The test results are presented.
  • Conference Object
    Numerical Analysis of Planar Cam Follower Mechanisms
    (IFToMM, 2012) Kiper, Gökhan; Huang, Chintien; Söylemez, Eres
    Given planar cam profiles and follower types, this paper analyzes their displacement diagrams numerically. The algorithm is based on the concept that a cam and its follower must have a common normal at the contact point. Instead of using kinematic inversion, this paper directly calculates contact points in the fixed coordinate system. This paper demonstrates a straightforward approach for motion analysis when discrete cam profile data points and link lengths are available. We implement the method by using the spreadsheet program Microsoft Excel®, which is well-suited for dealing with discrete data points. The results given in this paper can easily be employed in reverse engineering applications and adapted in undergraduate curriculum.
  • Article
    Function Generation Synthesis of Planar 5r Mechanism
    (IFToMM, 2013) Kiper, Gökhan; Bilgincan, Tunç; Dede, Mehmet İsmet Can
    This paper deals with the function generation problem for a planar five-bar mechanism. The inputs to the mechanism are selected as one of the fixed joints and the mid-joint, whereas the remaining fixed joint represents the output. Synthesis problem of the five-bar mechanism is analytically formulated and an objective function is expressed in polynomial form. Function generation synthesis is performed with equal spacing and Chebyshev approximation method. The four unknown construction parameters and the error are evaluated by means of five design points and the coefficients of the objective function are determined by numerical iteration using four stationary and one moving design point. Stationary points are placed at the boundaries of the motion and the moving point is re-selected at each iteration as the point corresponding to the extremum error. Iterations are repeated until the values are stabilized. The stabilization usually occurs at the third iteration. By this method, the maximum error values are approximately equated, hence the total error is bounded at certain limits. Finally the construction parameters of the mechanism are determined.