Graduate School of Engineering and Science
Permanent URI for this communityhttps://hdl.handle.net/10679/8952
Browse
Browsing by By Publication Category "International"
Now showing 1 - 7 of 7
- Results Per Page
- Sort Options
Conference ObjectPublication Metadata only 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, AlihanThis 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.Conference ObjectPublication Open Access The effect of interface gradient distribution on unrealistic flow in 3D droplet simulations(Europe, Institute for Liquid Atomization and Spray Systems, ILASS, 2021-08-31) Yılmaz, Anıl; Kayansalçik, Gökhan; Ertunç, Özgür; Mechanical Engineering; ERTUNÇ, Özgür; Yılmaz, Anıl; Kayansalçik, GökhanThe purpose of this study is to investigate the origin of the parasitic current to provide accurate prediction of droplet surface interactions in Volume of Fluid (VOF) framework. The deformation of the droplet due to parasitic current has been the most important problem in 3D simulations. Parasitic current is influenced by curvature and surface normal estimation in the Continuum Surface Force (CSF) model. It has been shown that the number of neighboring cells of the central cell influences the gradient calculations regarding the generation of parasitic current. It has been observed that the polyhedral cell structure delivers a smoother interface gradient distribution than the cartesian cell structure. To examine the dynamics in different physical conditions, we compared simulations with base experiments to understand whether those models work. We then simulated droplet cases on stationary and moving wall conditions, and simulation results were consistent with experimental results.Conference ObjectPublication Metadata only Effects of agent's embodiment in human-agent negotiations(ACM, 2023-09-19) Çakan, Umut; Keskin, Mehmet Onur; Aydoǧan, Reyhan; Computer Science; AYDOĞAN, Reyhan; Çakan, Umut; Keskin, Mehmet OnurHuman-agent negotiation has recently attracted researchers’ attention due to its complex nature and potential usage in daily life scenarios. While designing intelligent negotiating agents, they mainly focus on the interaction protocol (i.e., what to exchange and how) and strategy (i.e., how to generate offers and when to accept). Apart from these components, the embodiment may implicitly influence the negotiation process and outcome. The perception of a physically embodied agent might differ from the virtually embodied one; thus, it might influence human negotiators’ decisions and responses. Accordingly, this work empirically studies the effect of physical and virtual embodiment in human-agent negotiations. We designed and conducted experiments where human participants negotiate with a humanoid robot in one setting, whereas they negotiate with a virtually embodied replica of that robot in another setting. The experimental results showed that social welfare was statistically significantly higher when the negotiation was held with a virtually embodied robot rather than a physical robot. Human participants took the negotiation more seriously against physically embodied agents and made more collaborative moves in the virtual setting. Furthermore, their survey responses indicate that participants perceived our robot as more humanlike when it is physically embodied.Conference ObjectPublication Metadata only An integrated design approach for a series elastic actuator: Stiffness formulation, fatigue analysis, thermal management(IEEE, 2017-12-22) Yıldırım, Mehmet Can; Şendur, Polat; Bilgin, Onur; Gülek, Berk; Yapıcı, Güney Güven; Uğurlu, Regaip Barkan; Mechanical Engineering; YAPICI, Güney Güven; UĞURLU, Regaip Barkan; ŞENDUR, Polat; Yıldırım, Mehmet Can; Bilgin, Onur; Gülek, BerkThis paper presents an integrated mechanical design approach for the long-Term and repetitive use of series elastic actuators (SEAs). Already, computational models for series elastic actuator design have been developed in order to address the challenging weight and volume targets. However, an integrated design method in which the coupling effects between various interacting requirements that are explored at every stage of the design cycle does not exist. In particular, the interactions between the torsional stiffness, strength, fatigue life and thermal performance are not analyzed in-depth. To this end, we propose a comprehensive design approach in which the aforementioned requirements (FEA, stiffness formulation, fatigue analysis, and thermal management) are integrated in a complementary manner. Computer-Aided analyses and experimental results verified the effectiveness of our design approach. The proposed approach is employed to manufacture our SEA module CoEx-SEA.Conference ObjectPublication Metadata only Photon statistics effects on a QRNG of vacuum fluctuations(Optica Publishing Group, 2020-09-14) Dandaşi, Abdulrahman; Özel, Helin; Durak, Kadir; Electrical & Electronics Engineering; DURAK, Kadir; Dandaşi, Abdulrahman; Özel, HelinOptical scattering enhances randomness characteristics, increases the chaotic behavior of coherent sources, broadens the distribution of photon statistics and makes it super-Poissonian which allows faster sampling compared to Poissonian.Conference ObjectPublication Open Access Two-part bio-based self-healing repair agent for cement-based mortar(International Center for Numerical Methods in Engineering, 2020) Tezer, Mustafa Mert; Bundur, Zeynep Başaran; Civil Engineering; BUNDUR, Zeynep Başaran; Tezer, Mustafa MertFactors affecting durability of concrete structures are generally associated with each other. Due to its brittle nature, concrete can crack under stress and these cracks are one of the main reasons for a decrease in service life in concrete structures. Therefore, it is crucial to detect and recover microcracks, then to repair them as they were developed to wider cracks. Recent research in the field of concrete materials suggested that it might be possible to develop a smart cement-based material that is capable of remediate cracks by triggering biogenic calcium carbonate (CaCO3) precipitaton. This paper summarizes a study undertaken to investigate the self-healing efficiency of Sporosarcina pasteurii (S. pasteurii) cells immobilized on both diatomaceous earth and pumice, to remediate flexural cracks on mortar in early ages (28 days after mixing). To obtain a two-phase bio additive, half of the minerals were saturated with a nutrient medium consisting of urea, corn-steep liqueur(CSL) and calcium acetate and the cells with immobilized to the other half without nutrients. Screening of the healing process was done with ultrasonic pulse velocity (UPV) testing and stereomicroscopy. With this approach, the cracks on mortar surface were sealed and the water absorption capacity of the so-called self-healed mortar decreased compared to its counterpart cracked mortar samples.Conference ObjectPublication Open Access Validation and comparison of 2D and 3D numerical simulations of flow in simplex nozzles(Europe, Institute for Liquid Atomization and Spray Systems, ILASS, 2021-08-31) Bal, M.; Kayansalçik, Gökhan; Ertunç, Özgür; Böke, Y. E.; Mechanical Engineering; ERTUNÇ, Özgür; Kayansalçik, GökhanNumerical simulations of pressure swirl atomizers are computationally expensive due to transient and multiphase flow behavior. In this study, 2D and 3D VOF simulations are performed for a geomerty which has high swirl chamber length-to-diameter ratio of 1.33. discharge coefficient (CD) and spray angle values are compared to the experimental data. Moreover, a benchmark study is conducted between 2D and 3D methods in terms of accuracy, computational cost and flow variables such as orifice exit axial and tangential velocity. The simulations are performed using a hybrid RANS-LES approach, IDDES model. It is observed that 2D simulation has lower accuracy in the validation parameters such as discharge coefficient and spray angle as compared to the 3D simulation. The main reason for 2D simulation inaccuracy might be the tangential port inlet effects and wrong estimation of the loss of swirl inside the swirl chamber. On the other hand, 2D simulations have approximately 1000 times lower computational cost than 3D simulations.