Graduate School of Engineering and Science

Permanent URI for this communityhttps://hdl.handle.net/10679/8952

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Browsing by Institution Author "BEBEK, Özkan"

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    Automated flow rate control of extrusion for 3D concrete printing incorporating rheological parameters
    (Elsevier, 2024-04) Ahi, Oğulcan; Ertunç, Özgür; Bundur, Zeynep Başaran; Bebek, Özkan; Civil Engineering; Mechanical Engineering; ERTUNÇ, Özgür; BUNDUR, Zeynep Başaran; BEBEK, Özkan; Ahi, Oğulcan
    The use of inline quality assessment technologies is of great importance in meeting the consistent extrusion requirements of 3D concrete printing (3DCP) applications. This paper presents a system to regulate extrusion speed and maintain the flow rate at a target value during 3DCP processes. The system is based on a new equation that combines printing parameters and the material's rheological properties in the printing process. The proposed control strategy is designed to effectively function with various cement-based mixtures. Validation tests demonstrate that the proposed system can maintain an instantaneous flow rate within a certain range and eventually achieve a constant flow rate. During operation, the flow rate is consistently maintained around the targeted value with an average error rate of 6.7 percent. The flow rate control mechanism shows promise as a reliable and efficient solution for achieving precise and constant flow rates, regardless of the cement mix design used.
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    Design and development of a torsion-based series elastic actuator with nested encoders for a wearable exoskeleton robot
    (IEEE, 2022) Kuru, Alihan; Uğurlu, Regaip Barkan; Bebek, Özkan; Mechanical Engineering; UĞURLU, Regaip Barkan; BEBEK, Özkan; Kuru, Alihan
    This paper presents the design of a high torque-to-mass ratio series elastic actuator (SEA) for wearable powered exoskeletons. Nonbackdrivable actuators are ideal for applications that require high torque. Commonly, active exoskeleton robots are powered by actuators that are nonbackdrivable. Due to the high gear ratio, the output mechanical impedance of these actuators is quiet high which renders their force/torque control challenging. To provide torque controllability a custom torsional spring has been produced and placed at the output side of the series elastic actuator. In addition, the measurement of the angular displacement of this elastic element is challenging in terms of mechanical design. To prevent this design challenge a double shaft mechanism was proposed. In this mechanism, the first shaft, which connects the spring and the spring encoder, goes through the second shaft, which is connected to the motor and the motor encoder. This way both encoders are placed on a the same side of the SEA. In addition to explaining this compact spring shaft mechanism, this article presents the results of the cascaded PID controller with a disturbance observer (DoB) applied on the actuator.
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    Development and 3D spatial calibration of a parallel robot for percutaneous needle procedures with 2D ultrasound guidance
    (World Scientific, 2017-12-01) Ahmad, Mirza Awais; Orhan, Sabri Orçun; Yıldırım, Mehmet Can; Bebek, Özkan; Mechanical Engineering; BEBEK, Özkan; Ahmad, Mirza Awais; Orhan, Sabri Orçun; Yıldırım, Mehmet Can
    Robotic systems are being applied to medical interventions as they increase the operational accuracy. The proposed autonomous and ultrasound guided 5-DOF parallel robot can achieve such accuracy for needle biopsies, which particularly demand precise needle positioning and insertion. In this paper, the robot's mechanical design, system identifications, and the design of its controller are explained. A torque computed controller with gravity compensation and friction models, yielding a 0.678mm RMS position error for the needle tip, was used. A novel method was used for 3D space calibration of the images for detecting the volume of interest in the biopsy procedure by a multipoint crosswire phantom with parallel threads. The calibration technique had a validation RMS error of 0.03mm.
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    Topology optimization-based design and development of a compact actuator with a high torque-to-weight ratio for quadrupeds
    (IEEE, 2022) Akın, Barış; Özçınar, Erim Can; Balcı, Barış; Emre, Sinan; Şendur, Polat; Bebek, Özkan; Ünal, Ramazan; Uğurlu, Regaip Barkan; Mechanical Engineering; ŞENDUR, Polat; BEBEK, Özkan; ÜNAL, Ramazan; UĞURLU, Regaip Barkan
    This paper presents the design, development, and testing procedures for a compact actuator with a high torque-to-weight ratio, generally aimed to actuate legged robots, e.g., quadrupeds. The main goal of designing the actuator was to keep its total weight minimum while ensuring a high torque output. Therefore, the following design steps were implemented: i) the actuator was designed in accordance with the torque output requirement and the stress distribution that was mapped on actuator frames, ii) topology optimization was conducted on the initial design and it is modified in accordance with optimization results, and iii) the optima actuator design was built and tested on in a realistic scenario in which it powered an actual quadruped robot for validation. As the result, the proposed actuators could track the desired walking trajectory with a relatively low error. In conclusion, continuous torque output of 48 Nm was obtained via a lightweight (1.6-1.7 kg) actuator design.