Yazar "Karali, Mehmet" seçeneğine göre listele

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    Design optimization of industrial robot arm to minimize redundant weight
    (Elsevier - Division Reed Elsevier India Pvt Ltd, 2019) Bugday, Mustafa; Karali, Mehmet
    In industrial robots, projected torque increases depending on the extending reach length and payload. This requires selection of powerful motors particularly on the second axis. Since arm rigidity becomes more important as the expected positioning precision increases, less flexible materials are used. Therefore, during operation conditions, 70% of motor's energy is used for redundant weight. In this study, analyses conducted on five different robotic arms belong to different brands. Arm's payload distribution in terms of region and amount is examined, alternative designs are analysed and compared with each other. Geometry and materials are changed in alternative designs. In this way, redundant weight is minimized (without increasing the share amount) at the same positioning precision. Results of this study demonstrated a 10% decrease in inert payloads. (C) 2018 Karabuk University. Publishing services by Elsevier B.V.
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    Development of a fuzzy logic-based loading algorithm in the selection of the most appropriate cargo package for cleaning and cosmetic products
    (Editura Acad Romane, 2018) Karali, Mehmet
    Minimum space and maximum capacity based loading algorithms or software products for in-container parcel loading or in-box product placement are very common. These software products, when desired to be used for placing cleaning and cosmetics products in cargo packages, have a number of special constraints and related challenges. Breakage, disintegration or spillage can occur in products that are not placed properly during transportation and transferring of the cargo packages. For some products; there are constraints such as horizontal placement is not allowed, another product cannot be placed on top of them, or tightly placement cannot be done. On the other hand, for some products, there is freedom to put them in every cavity because of their flexible structure. Due to these constraints and freedoms, the placement algorithm needs to have product-based flexibility. In this study, cleaning and cosmetic products which have special restrictions and freedoms are taken as the primary targets. An algorithm has been developed that optimizes the placement of these products in the package. The algorithm is run and tested using the Excel database and macro code. The algorithm is integrated into a private company product line. Thanks to this software automation, which is developed to make package selection at the right size, 14,4 % monthly cargo charge and 10 % labor savings are obtained.
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    The Effect of Rotor Plates on Capacitive Measurement in Capacitive Encoders
    (IEEE, 2020) Yavsan, Emrehan; Karali, Mehmet; Gokce, Baris; Erismis, Mehmet Akif
    The moving plates of the capacitive encoders are called rotors and the fixed plates are called stators. In this study, the effects of the rotor plates on capacitive measurement for capacitive encoders are analyzed. Encoders are used in angular position measurement. They can be preferred especially in most applications where rotational motion occurs in the robotic application areas. The application areas of the encoders can be further extended with the capacitive encoder technology. The capacitive encoder technology is based on measuring the capacitances between the encoder plates. As the capacitances vary depending on the overlapping areas of the encoder plates, the shapes and the patterns of the encoder plates directly affect the capacitive measurement. Therefore, the capacitive encoder plate selections must be made correctly. There are very few studies on the selection of the capacitive encoder plates. It is seen that the current studies generally continue on a similar type rotor patterns. Various rotor plates are proposed in this study for the capacitive encoder that we are in the development process. After the rotor patterns are expressed mathematically and the capacitive encoders using rotors with these patterns are compared. The comparison process was made by calculating the equivalent capacitance between the proposed capacitive encoder plates. The effects of rotors with different materials and patterns on the capacitive measurement were investigated. Thus, a contribution was made to the effective development of similar capacitive sensors.
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    Investigation on Characterization of GGG 60 Coated with WC/Co by ESD Technique
    (Maik Nauka/Interperiodica/Springer, 2023) Bugday, Mustafa; Karali, Mehmet; Talas, Suekrue
    Hard surface coatings are necessity when the surface of a metallic materials are required to perform better during the service and lower the cost of replacement and labour. In this study, WC/Co coatings were deposited on GGG60 ductile (spherical graphite) cast iron with Electro Spark Deposition technique. The ductile cast iron specimens were non heat treated, heat treated for hardening the surface and subsurface prior to coating. Optimum coating parameters were determined as 132 V and 1230 Hz. Coating characterization was investigated by SEM/EDS and XRD. The surface hardness value of the substrate sample increased from 270 +/- 5.6 HV0.2 to 1330 +/- 12.5 HV0.2. Surface hardness value increased 5 times. The presence of W2C, W and WC1 - x phases in the coatings increased the possibility of decarburization. WC ratio was calculated more in heat treated coated samples compared to other coatings. The mechanical properties of the coatings were tried to be determined by tensile and three-point bending tests. The tensile stress of the heat-treated coated samples was calculated as 780 MPa and the maximum bending stress was calculated as 1581 MPa. The decrease in the C ratio in the coating in the heat treated coated samples made the samples more resistant to thermal stresses.
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    A New Discrete Analog Circuit Solution for Capacitive Rotary Encoders
    (IEEE-Inst Electrical Electronics Engineers Inc, 2022) Kara, Muhammet Rojhat; Yavsan, Emrehan; Karali, Mehmet; Erismis, Mehmet Akif
    In the time of global chip crisis, it is clear that alternative electronic solutions are necessary; particularly for capacitive rotary encoders, or similar capacitive sensors where demodulation techniques are extensively used. In this work, a discrete analog switch based circuit solution is proposed for the capacitive rotary encoders for the first time in the literature to the best of our knowledge. A 3-layer uniquely designed capacitive encoder prototype is used as a capacitive sensor. The analog switch with OPAMP based demodulation configuration designed for this work is both cheaper and it works at higher frequencies than the analog multiplier configuration. Also, unlike ASIC, it does not require high-tech for production. With the established test setup; noise, smallest perceptible capacitance, nonlinearity and temperature analyses of the circuit were made and competing resultswere achieved. The noise levels in terms of degree and voltage are measured as 0.0063 degrees and 36.62 mu V root Hz; respectively. Minimum measurable capacitance achieved with the discrete analog circuit is 2.54 aF root Hz. Nonlinearity was found to be 0.29% which is highly correlated with the mechanical misalignments of the capacitive encoder. Although this particular study is carried out on capacitive encoders, the proposed circuit solution can be used for similar types of sensors.
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    A novel high resolution miniaturized capacitive rotary encoder
    (Elsevier Science Sa, 2021) Yavsan, Emrehan; Kara, Muhammet Rojhat; Karali, Mehmet; Gokce, Baris; Erismis, Mehmet Akif
    In this paper, design and prototyping of a novel, high resolution, and low-cost capacitive encoder were presented. Detailed analysis showed that the number of poles on the rotor should be as high as possible to keep the gain high and to reduce the non-linearity. Moreover, contrary to the common intuition, inter electrode gap is found to have an optimum non-zero value, corresponding to a particular number of poles, in order to maximize the gain. However, increasing number of poles brings practical problems due to manufacturing limits and digital electronic frequency load. As the electronics, micro-controller based digital signal processing is used to keep the cost as low as possible. With miniaturizing the encoder geometry as a design target, the number of plates were increased to three to increase the capacitances. One prototype, which is around 3 cm in diameter could be successfully mounted to an industry oriented DC motor and tested. The tests of this miniaturized encoder showed non-linearity error of 0.12% and resolution of 0.02 degrees. One source of the non-linearity error is the DC motor itself, and we believe that with a better setup, the error could be measured to be even better. (C) 2021 Elsevier B.V. All rights reserved.
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    Performance Comparison of Different Fuzzy Logic Controllers on Vehicle-Caravan Systems
    (Eos Assoc, 2023) Karasahin, Ali Tahir; Karali, Mehmet
    Active control techniques in Vehicle-Caravan (VC) systems are designed to prevent instability modes. This study used Fuzzy Logic Controllers (FLCs), developed using the differential braking method, to prevent instability modes in a VC system and increase yaw stability. Four different FLC-based controllers were designed for the VC system: type-1 Mamdani, type-1 Sugeno, simplified type-2, and Interval Type-2 (IT2). FLC-based controllers are used in VC systems due to nonlinear characteristics. This study showed that unstable situations can be prevented with FLCs according to the inputs obtained from a single IMU sensor placed in the caravan. The performance of the controllers developed in MATLAB/Simulink was assessed using CarSim. Experimental studies showed that the skidding that occurs after the Double Lane Change (DLC) maneuver is prevented by FLC-based controllers and the yaw stability is increased.
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    Uniaxial and biaxial deformation characteristics of AA7075-O friction stir welded joints
    (Springer Heidelberg, 2020) Acar, Dogan; Karali, Mehmet; Cora, Omer Necati; Burford, Dwight; Koc, Muammer
    The formability of friction stir welded (FSW) AA7075-O aluminum alloy sheet specimens was tested under a range of warm uniaxial and biaxial loading conditions. To study the effect of FSW process conditions on formability, four groups of specimens were prepared using a range of FSW parameters. Two rotational speeds (500 and 1000 rpm), four travel speeds (4.2, 5.1, 8.5, 12.7 mm/s), and four axial force levels (6895, 7006, 7117, 7346 N) were included in the test matrix. Each specimen had a butt joint centrally located and oriented parallel to the sheet rolling direction. Specimens from each of the four groups were then tested under different combinations of uniaxial (e.g., transverse tensile test) and biaxial loading conditions (bulge test), including at two different strain rates (0.0013 and 0.013 1/s) and three different temperature levels (25, 200, and 300 degrees C). From the flow curves obtained from each test combination, the relative effect that FSW parameters (rotational speed, travel speed, and axial force) and forming parameters (temperature and strain rate) had on formability was investigated in detail. Mechanical and structural variations of the weld zone were compared with those of the base material. Tool rotational speed was observed to have a major effect on the yield and tensile strength of FSW blanks, with strengths varying by as much as 20% over the range process and forming parameters tested. Stress-strain curves obtained by using hydraulic bulge tests yielded a 5-10% increase in strain values compared with uniaxial tensile test results. In the bulge tests, the fracture zone was only observed to occur at the apex of the dome along the joint line for specimens tested at 300 degrees C and a strain rate of 0.0013 1/s. Specimens tested under other FSW parameters and process combinations did not fail in this location. In tensile tests, the specimens were only fractured on the welding line under forming conditions of 300 degrees C and at either the low or the high strain rate. Otherwise, the specimens failed away from the joint line. The maximum dome height, as a measure of formability, was obtained under forming conditions of 200 degrees C temperature and at a 0.0013 1/s strain rate. This result correlated well with stress-strain curves obtained from uniaxial tension testing.
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    Wear performance of GGG60 ductile iron rollers coated with WC-Co by electro spark deposition
    (Consejo Superior Investigaciones Cientificas-Csic, 2023) Bugday, Mustafa; Karali, Mehmet; Talas, Suekrue
    Nodular cast irons are used in many industrial applications such as machine frames and body, rollers and engine blocks due to their higher strengths and ductility with good machinability comparable to grey cast irons. In this study, the outer surface of nodular cast irons (GGG-60) was coated with WC/Co using electro spark deposition (ESD). The aim of the study is to improve both the surface quality and wear behaviour with the coatings formed on the surface of the plastic deformation rollers, whose wear resistance decreases over the time due to high stress working conditions. Heat treatment at 950 degrees C for 2 h was applied to the GGG60 specimen rollers and half of the rollers were uncoated and the other half was coated with WC-Co electrodes. The wear behaviour of the heat treated and coated surfaces was measured by ball-on-disc wear method using Al2O3 ball bearing with a diameter of 6 mm for a sliding distance of 250 m at a sliding rate of 6.5 m center dot s-1 under a dry condition, and using a load of 40 N. WC/Co coatings were successfully applied to rollers. In the SEM/EDS images, the presence of W, Fe, C, Co and Al elements in the coated part of the rollers and Fe, C and Al elements in the uncoated region were detected. It was concluded that Coating and heat treatment increased the wear resistance by nearly 5 times and decreased the friction coefficient by 2.13 times.