Makine Mühendisliği Bölümü Tezleri

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/371

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    Citation Count: ALDULAİMİ, H. (2015). Design and analysis of an overconstrained manipulator for rehabilitation. Yayımlanmamış yüksek lisans tezi. Ankara: Çankaya Üniversitesi Fen Bilimleri Enstitüsü
    Design and analysis of an overconstrained manipulator for rehabilitation
    (2015-04) Aldulaimi, Hassan; Çankaya Üniversitesi, Fen Bilimleri Ensitütüsü, Makine Mühendisliği Bölümü
    A parallel manipulator is a closed loop kinematic chain mechanism that is attached to the base by at least two limbs in parallel. Compared with the serial, the parallel manipulator has higher load-carrying capacities, higher accuracy, higher stiffness and lower inertia. Due to these advantages the parallel manipulator become viable alternative for wide applications, therefore it have been the subject of study of many research during the recent three decades. However, these kinematic closed loops also have some disadvantages, such as limited workspace, complicated forward kinematics, high cost and complicated structures. To overcome these disadvantages parallel manipulators with less than 6-DoF can be used. Also, designing a parallel manipulator with less than six degree of freedom for a subspace can relatively reduce the complexity.This thesis deals with one of the applications of parallel manipulator as a rehabilitation robot. This device is an over –constrained parallel manipulator 5 degree of freedom with 3 legs. This manipulator consists of a moving platform which is connected to a fixed base via three legs. Each leg is made of RRR(RR) (revolute) joints where the first three joint in all legs are parallel and the recent two joint are intersecting .Inverse kinematics of this device including position velocity and acceleration are studied. In addition, the workspace of the parallel manipulator is analyzed. A design optimization is conducted for the prescribed workspace of the device. Finally, this thesis also deals with the dynamic modeling the manipulator using an approach of the principle of virtual work. The equations of motion of the manipulator are derived by considering its motion characteristics. To reduce computations, inverse Jacobian matrices for manipulators are derived to give relations between input and output variables.
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    Citation Count: ZİYARA, A.A.İ. (2015). Optimization of the fabrication processes of microfluidic chips by hot embossing. Yayımlanmamış yüksek lisans tezi. Ankara: Çankaya Üniversitesi Fen Bilimleri Enstitüsü
    Optimization of the fabrication processes of microfluidic chips by hot embossing
    (2015-02) Ziyara, Abbas Ali İbrahim; Çankaya Üniversitesi, Fen Bilimleri Enstitüsü, Makine Mühendisliği Bölümü
    Currently, the advent of microfluidics offers promising tools, especially in life sciences, with applications ranging from biological or chemical sensors to organs on chips. Although, this technology contains various other advantages such as reduction in sample and reagent consumption, decrease in reaction times, and improved accuracy, there are still a few number of commercially available microfluidic devices. One of the reasons hampering commercialization of microfluidics is its fabrication cost. Lithography based techniques are commonly used for microfluidic fabrication owing to the high precision. However in lithography based microfluidic fabrication methods manufacturing lead times are often high. Design-to-device period may reach up to several days. Here, micro scaled conventional methods such as micro milling, micro injection molding, or hot embossing are more prominent. In these methods, the cycle time reduces down to hours or even minutes. This in turn reduces the cost per device considerably. This thesis aims to design and construct a low cost hot embossing press and optimize the process parameters for fabrication of microfluidic chips. The hot embossing press was designed as a low cost device, having material cost as low as 224 TL. For testing purposes, we fabricated a mold made of brass using micro milling process. We proved that, we can obtain 200 m wide channels on polymethylmethacrylate (PMMA) substrates, by applying 240 bars or pressure for 6 min. under 180 oC temperature, total cycle time per one chip is found to be 11 min.