Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Function Generation Synthesis of Planar Mechanisms as a Mixed Problem of Correlation of Crank Angles and Dead-Center Design(Izmir Institute of Technology, 2022) Kadak, Tarık; Kiper, GökhanKinematic synthesis of mechanisms is generally divided into three groups. One of them is function synthesis. In function synthesis, the design of correlation of crank angles and dead dead-center position stand out. These problems have been clearly defined and solved separately. But in some cases, problems may be encountered that require both correlation of crank angles and dead dead-center design. Such problems are called mixed function generation problems. In this thesis, an overview of these mixed function generation problems has been given and many problems have been solved analytically or semi-analytically. The solutions of all problems including three positions for the four-bar mechanism and the solution of a problem including four positions for a four-bar mechanism have been addressed. A problem including 3 positions and a problem including 4 positions for a slider-crank mechanism have been addressed. All solutions have been reduced to univariate equation and a fast solution has been found. Thus, link lengths can be found quickly by changing the problem inputs. Numerical solutions of all problems have been demonstrated using Excel.Master Thesis Design and Experimental Evaluation of a Dynamically Balanced Over-Constrained Planar 6r Parallel Manipulator(Izmir Institute of Technology, 2019) Özkahya, Merve; Kiper, Gökhan; Dede, Mehmet İsmet CanWith the development of the industry, the number of robots used in the production line is increasing day by day. Particularly, it is known that parallel robots are better in terms of positioning accuracy compared to serial robots based on the stretching of robot arms. In parallel mechanisms, there are many factors such as calibration, stability and dynamic balancing of the mechanism affecting positioning accuracy. The aim of this thesis is to dynamically balancing parallel mechanisms to improve positioning accuracy. In high acceleration applications, the shaking force and moment are the factors that cause vibration in the base of the mechanism. These vibrations can be reduced by designing dynamically balanced mechanisms. In this thesis, over- and simply constrained 6R mechanisms are designed for dynamic balancing studies and prototypes are produced. The counter mass method was used to balance the mechanism dynamically. The design of the masses was made according to the mass information received from the model designed in the computer aided drawing program and the parts of the mechanisms were updated according to their actual mass values after they were produced. The design of the masses is designed according to the mass information from CAD model and the parts of the mechanisms are updated according to their actual mass values after they are produced. Dimensional measurements were taken by FARO Prime Arm device due to faults that may arise from the production in the parts of the mechanism after production. Then the mechanism was assembled. Before carrying out the balancing tests, calibration studies affecting the positioning accuracy of the over-constrained mechanism were carried out. Finally, the mechanism is activated balanced and unbalanced and the acceleration effect of the 6-axis accelerometer is obtained experimentally.Master Thesis Design of a 2r1t Mechanism With Remote Center of Motion for Minimally Invasive Transnasal Surgery Applications(Izmir Institute of Technology, 2018) Yaşır, Abdullah; Kiper, Gökhan; Dede, Mehmet İsmet CanIn minimally invasive surgery, use of robotic manipulators is becoming more and more common in order to have more precise operations and better post-operative processes. Such operations are often performed through an incision port (a pivot point) on the patient’s body. Since the manipulator should move about the pivot point, it should have a remote center of motion. In this regard, the main objective of this thesis is designing a 3-dof (degrees-offreedom) surgical robotic arm that is capable of 2R1T (R: rotation, T: translation) motion pattern and is structured as a remote center of motion mechanism for minimally invasive surgery applications. First, the structural synthesis of a 3-dof manipulator with 2R1T motion pattern is performed. The synthesized structures also can be used for any kind of 2R1T-type applications. Then, the manipulators with various kinematic structures are evaluated for a transnasal surgery according to several evaluation criteria such as feasibility of construction for a remote center of motion mechanism, ease of balancing, number of links, structural symmetry, decoupling of the joint inputs and the output motion of the platform and the number of actuators connected to the base. The best option is evaluated as a parallel manipulator with two 1 F0-system and one 1 F0-1 F∞-system leg structures. Afterwards, kinematic analysis of the spatial parallel manipulator is formulated with a simplified kinematic model consisting of three intersecting planes so that dimensional design is done for a desired dexterous workspace. Finally, constructional design is completed and a prototype is manufactured and tested.Master Thesis Kinematic Design of Scissor Linkages(Izmir Institute of Technology, 2018) Karagöz, Cevahir; Kiper, GökhanThe primary objective of this thesis is to propose a design method for linkages simulating the transformation of a planar curve from an initial form to a final form. First, the topologies of fundamental loops are examined using symmetry patterns. Design methodologies for the hence obtained mechanisms are formulated. The given curves are discretized initially, and the nodes are constructed. Then the side lengths of the loops are obtained in order to obtain the desired transformation between the given curves. Finally, different deployable and transformable linkage examples are presented.Master Thesis Optimal Design of a Kinesthetic Haptic Device Mechanism for Enhancing Its Impedance Characteristics(Izmir Institute of Technology, 2018) Görgülü, İbrahimcan; Dede, Mehmet İsmet Can; Kiper, GökhanIn this work, the optimal design of modified version of 3 degrees of freedom RCUBE mechanism has been studied in order to develop a high-performance haptic device mechanism. A high-performance haptic mechanism is achieved by having high transparency and high-frequency range. These two properties are determined by the mechanical impedance of the mechanism. Hence, to increase the quality of a haptic mechanism, its mechanical impedance performance must be enhanced. This refers to have low inertia, low friction, high back-drivability, high force output, high structural stiffness, and high manipulability for the mechanism. All these properties are designated by kinematic, stiffness, and dynamic properties of the mechanism. Hence, as a first step of this thesis, kinematic, stiffness and dynamic models of the mechanism are analytically procured. The analytical model of stiffness is achieved via the virtual joint method. Then, in order to obtain the objective function for the design procedure, performance metrics affecting the above-mentioned properties are reviewed and produced. Since these metrics have common parameters such as link lengths and the cross-section area of the links, there is a highly non-linear and contradictory relationship between the metrics. In order to deal with the non-linearity and to determine the global optimum design, an evolutionary optimization method, genetic algorithm, is preferred. The optimization time is reduced by investigating the most critical poses of the workspace and reducing the performance metrics to simpler forms. The link lengths and the cross-section areas are optimized. Carbon fiber tubes are used as links. The Pareto-front solution set is obtained as a result of the optimization procedure.Finally, an optimal solution is proposed and evaluated for the design of this modified R-CUBE mechanism to be used in haptic applications.Master Thesis Design of Hybrid Cable-Constrained Parallel Mechanisms for Walking Machines(Izmir Institute of Technology, 2018) Demirel, Murat; Kiper, Gökhan; Demirel, Murat; Kiper, Gökhan; Carbone, GiuseppeThe objective of this thesis study is to propose novel cable-constrained parallel mechanisms for walking machines. According to the literature, hybrid structured parallel mechanisms can overcome mechanical design, control system and workspace limitations compared to other structures. This thesis study introduces two novel hybrid structured leg mechanisms comprising rigid links and passive cables. Kinematic structure of the proposed mechanisms are (UPU-2Pa)-(UPU-2Pa)and (UU-2Pa)-P. Both designs have a hip, a knee and a foot platform. Two rotational constraints about horizontal axes are added to the moving platforms by using parallelograms with passive cables. The rotational constraint about the vertical axis is provided by rigid links and joints. Thus, the proposed designs have pure translational motion. The detailed analysis of the mechanism design with anchored cables is conducted. A CAD model is constructed and a dynamic simulation for human-like gait trajectory is performed in SolidWorks® environment. Once the computed actuator torques and forces are found suitable, a first prototype is built to check the proposed solution. Considering the problems encountered in this first prototype, a second prototype of the (UU-2Pa)-P mechanism is built. The prototype is operated using a real-time PCI controller and experimental results are presented. The mechanisms presented in this thesis is one of the few cable-constrained parallel manipulator designs in the literature. Such a manipulator design is used for a walking machine for the first time. The prototype and test results are quite satisfactory, so hopefully more detailed research can be conducted on this topic in the future.Master Thesis Design of a Deployable Structure To Be Used as Temporary Ramp(Izmir Institute of Technology, 2017) Doğan Kumtepe, Elvan; Kiper, GökhanPortable ramps, used generally by wheelchair users, offer temporary solution to increase accessibility and mobility. It is expected that these ramps should be compact and lightweight in terms of ease of handling and storage. Different types of portable ramps in the market, which can be used by wheelchair users, are generally made of aluminum and their compactness is convenient to be redesigned and developed in the matter of increasing compactness. In this context, the main objectives of the thesis are to determine the wheelchair users’ inclinations and design a product to achieve better compactness and lightness by comparison with similar products in the market. To this end, a case study addresses challenges of designing of a deployable structure to be used as temporary ramp. The design approach and its implementation are described briefly and example of parametric analyses are illustrated in this study. First, the geometrical design is performed considering several alternative forms. The link lengths are optimized for compact rolling. Then load bearing capacity of the assembly is analyzed analytically and also verified with finite-element analyses. Material selection is performed for the composite panels and the panel thickness is determined according to strength of materials calculations. Finally, prototypes are manufactured and tested according to standards. The final design is 15,1% more compact and has 20,25% less weight compared to the best rival product available in the market. Also the product was tested by some wheelchair users and their opinions about the product are asked. Positive feedbacks are taken.Master Thesis Type Synthesis and Instantaneous Mobilty Analysis of 3-Upu Parallel Manipulators(Izmir Institute of Technology, 2017) Boztaş, Sercan; Kiper, GökhanIn this study, the literature was examined and known derivatives of the 3-UPU parallel manipulator were investigated to reveal the mobility characteristics of the 3-UPU parallel manipulator. For a 3-UPU parallel manipulator, U represents the universal joint, while P represents the prismatic joint. It is a very well-known manipulator that can provide the platform with three degrees of freedom of pure translation, pure rotation or mixed translation and rotation with respect to the base, according to the relative directions of revolute joint axes. For this reason, in this study, alternative joint axis orientations on the platforms and the limbs are examined. The generated joint layouts for the platforms were matched with each other to generate and classify alternative manipulator architectures based on some assumptions. The topological structures of thus obtained parallel manipulators are examined and limb types were determined. These limb types were then analyzed with the help of screw theory. Reciprocal screw sets were analyzed by singular value decomposition method and the instantaneous degrees of freedom of the manipulators and the motion characteristics of the moving platforms are tabulated. The finite mobility analysis of one the parallel manipulators is performed using Solidworks Motion as an example. Among several different 3-UPU parallel manipulator architectures, especially 118 novel 3-UPU parallel manipulators with non-parasitic three degrees-of-freedom are significantly important. The classified 3-UPU parallel manipulators with determined motion characteristics can be used by researchers as a design alternative for a specific design task.Master Thesis Design Modification of a Front Window Mechanism for the Cabin of an Earth Moving Machine(Izmir Institute of Technology, 2017) Jovichikj, Radomir; Kiper, GökhanThis thesis study investigates the front window mechanism used in an earth moving machinery. Since the mechanism is actuated by the operator, the required actuation force for the mechanism needs to be as minimum as possible. The problem of this thesis is defined by Turkey branch of Mecalac Company and the final test of this study are performed in their facility. First, the problem definition and aim of the study is presented. Furthermore, the literature review is also presented. Then, the current mechanism attached on the earth moving machinery is investigated. Firstly, kinematic analysis is performed in order to be able to perform the force analysis. Following that, using three different approaches (Newton-Euler approach, virtual work method and graphical approach), the static force analysis is done. The aim of this analysis to obtain the required actuation force, both for opening and closing the mechanism. By using three different approaches, the result obtained after each method are compared and confirmed. Furthermore, a simulation of the mechanism is prepared in MATLAB/Simulink® environment. This step provided a numerical simulation verification for the resulting actuation forces. Then the work carried out for the minimization of the actuation force is presented. By changing the parameters of the springs attached on the current mechanism, changing the link lengths of the mechanism and changing the application point of the actuation force, the change in the magnitude of the required actuation force is observed and minimized. Among all trials, only changing the spring position led to useful results. Finally, the test setup to measure the performance and experimentally verify the proposed solution is explained and the results are given. The results show that with the modified location of the spring, both of the maximum force requirements and the work requirements are lowered.Master Thesis Modelling and Experimental Setup of a Cable Driven System(Izmir Institute of Technology, 2016) Eraz, Talha; Kiper, Gökhan; Dede, Mehmet İsmet CanThis study is about a single degree of freedom mechanism to be used for human arm rehabilitation purposes and actuated with cable-drive. The purpose of the design is to support rehabilitation motions with a single degree of freedom (dof) mechanism. Design criteria is set based on research and meetings with medical doctors. The desired design is an exoskeleton type system to support human arm on each moving part of it. The first designed four- bar mechanism had actuation problems. Torque requirement was unacceptably high near the singularity of the designed four-bar mechanism. This problem is later overcome by an extra dyad of two additional links. However, the extra dyad solution caused problems of back-drivability near the singularity of new dyad. In order to achieve a back-drivable four-bar mechanism that has a smooth actuation requirement through the motion, a novel cable actuation system is designed. Cable is attached to system on coupler link and the attachment point on the coupler is designed to achieve a straight path for the efficiency of the cable drive. However, a single straight line throughout the motion is not achievable. Therefore, path is divided into subsections of straight line paths. Intermediate pulleys are placed for cable to follow straight line sections. The cable is designed as closed loop. A prototype of the system is built and presented in last chapter.