Researcher:
Başdoğan, Çağatay

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Çağatay

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Başdoğan

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Başdoğan, Çağatay

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Now showing 1 - 10 of 90
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    Publication
    Effect of finger moisture on tactile perception of electroadhesion
    (Institute of Electrical and Electronics Engineers, 2024) Lefevre, Philippe; Martinsen, Orjan Grottem; Department of Mechanical Engineering; Department of Mechanical Engineering; Aliabbasi, Easa; Muzammil, Muhammad; Şirin, Ömer; Başdoğan, Çağatay; Graduate School of Sciences and Engineering; College of Engineering
    We investigate the effect of finger moisture on the tactile perception of electroadhesion with 10 participants. Participants with moist fingers exhibited markedly higher threshold levels. Our electrical impedance measurements show a substantial reduction in impedance magnitude when sweat is present at the finger-touchscreen interface, indicating increased conductivity. Supporting this, our mechanical friction measurements show that the relative increase in electrostatic force due to electroadhesion is lower for a moist finger.
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    Experimental estimation of gap thickness and electrostatic forces between contacting surfaces under electroadhesion
    (Wiley, 2024) Martinsen, Orjan Grottem; Pettersen, Fred-Johan; Colgate, James Edward; Department of Mechanical Engineering; Department of Mechanical Engineering; Aliabbasi, Easa; Başdoğan, Çağatay; Graduate School of Sciences and Engineering; College of Engineering
    Electroadhesion (EA) is a promising technology with potential applications in robotics, automation, space missions, textiles, tactile displays, and some other fields where efficient and versatile adhesion is required. However, a comprehensive understanding of the physics behind it is lacking due to the limited development of theoretical models and insufficient experimental data to validate them. This article proposes a new and systematic approach based on electrical impedance measurements to infer the electrostatic forces between two dielectric materials under EA. The proposed approach is applied to tactile displays, where skin and voltage-induced touchscreen impedances are measured and subtracted from the total impedance to obtain the remaining impedance to estimate the electrostatic forces between the finger and the touchscreen. This approach also marks the first instance of experimental estimation of the average air gap thickness between a human finger and a voltage-induced capacitive touchscreen. Moreover, the effect of electrode polarization impedance on EA is investigated. Precise measurements of electrical impedances confirm that electrode polarization impedance exists in parallel with the impedance of the air gap, particularly at low frequencies, giving rise to the commonly observed charge leakage phenomenon in EA. A novel and systematic approach is introduced, leveraging electrical impedance measurements to infer electrostatic forces between two dielectric materials under electroadhesion (EA). This innovative approach holds promise for diverse applications spanning robotics, automation, space missions, textiles, and tactile displays. Furthermore, this study sheds light on the physics of EA, offering valuable insights with implications for the design of electroadhesive devices.
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    Contact mechanics between the human finger and a touchscreen under electroadhesion
    (Natl Acad Sciences, 2018) Scaraggi, Michele; Persson, Bo N. J.; N/A; N/A; Department of Mechanical Engineering; Department of Mechanical Engineering; Ayyıldız, Mehmet; Şirin, Ömer; Başdoğan, Çağatay; Researcher; PhD Student; Faculty Member; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; 125489
    The understanding and control of human skin contact against technological substrates is the key aspect behind the design of several electromechanical devices. Among these, surface haptic displays that modulate the friction between the human finger and touch surface are emerging as user interfaces. One such modulation can be achieved by applying an alternating voltage to the conducting layer of a capacitive touchscreen to control electroadhesion between its surface and the finger pad. However, the nature of the contact interactions between the fingertip and the touchscreen under electroadhesion and the effects of confined material properties, such as layering and inelastic deformation of the stratum corneum, on the friction force are not completely understood yet. Here, we use a mean field theory based on multiscale contact mechanics to investigate the effect of electroadhesion on sliding friction and the dependency of the finger-touchscreen interaction on the applied voltage and other physical parameters. We present experimental results on how the friction between a finger and a touchscreen depends on the electrostatic attraction between them. The proposed model is successfully validated against full-scale (but computationally demanding) contact mechanics simulations and the experimental data. Our study shows that electroadhesion causes an increase in the real contact area at the microscopic level, leading to an increase in the electrovibrating tangential frictional force. We find that it should be possible to further augment the friction force, and thus the human tactile sensing, by using a thinner insulating film on the touchscreen than used in current devices.
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    Effect of preservation period on the viscoelastic material properties of soft tissues with implications for liver transplantation
    (Asme, 2010) N/A; N/A; N/A; Department of Mechanical Engineering; Department of Mechanical Engineering; Department of Mechanical Engineering; Öcal, Sina; Özcan, Mustafa Umut; Başdoğan, İpek; Başdoğan, Çağatay; Master Student; Master Student; Faculty Member; Faculty Member; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; N/A; N/A; 179940; 125489
    The liver harvested from a donor must be preserved and transported to a suitable recipient immediately for a successful liver transplantation. In this process, the preservation period is the most critical, since it is the longest and most tissue damage occurs during this period due to the reduced blood supply to the harvested liver and the change in its temperature. We investigate the effect of preservation period on the dynamic material properties of bovine liver using a viscoelastic model derived from both impact and ramp and hold experiments. First, we measure the storage and loss moduli of bovine liver as a function of excitation frequency using an impact hammer. Second, its time-dependent relaxation modulus is measured separately through ramp and hold experiments performed by a compression device. Third, a Maxwell solid model that successfully imitates the frequency- and time-dependent dynamic responses of bovine liver is developed to estimate the optimum viscoelastic material coefficients by minimizing the error between the experimental data and the corresponding values generated by the model. Finally, the variation in the viscoelastic material coefficients of bovine liver are investigated as a function of preservation period for the liver samples tested 1 h, 2 h, 4 h, 8 h, 12 h, 24 h, 36 h, and 48 h after harvesting. The results of our experiments performed with three animals show that the liver tissue becomes stiffer and more viscous as it spends more time in the preservation cycle.
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    A variable-fractional order admittance controller for pHRI
    (IEEE Inc., 2020) Patoglu, Volkan; Tokatli, Ozan; Department of Mechanical Engineering; N/A; N/A; N/A; Department of Mechanical Engineering; Başdoğan, Çağatay; Aydın, Yusuf; Şirintuna, Doğanay; Çaldıran, Ozan; Faculty Member; PhD Student; PhD Student; PhD Student; College of Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; 125489; 328776; N/A; N/A
    In today's automation driven manufacturing environments, emerging technologies like cobots (collaborative robots) and augmented reality interfaces can help integrating humans into the production workflow to benefit from their adaptability and cognitive skills. In such settings, humans are expected to work with robots side by side and physically interact with them. However, the trade-off between stability and transparency is a core challenge in the presence of physical human robot interaction (pHRI). While stability is of utmost importance for safety, transparency is required for fully exploiting the precision and ability of robots in handling labor intensive tasks. In this work, we propose a new variable admittance controller based on fractional order control to handle this trade-off more effectively. We compared the performance of fractional order variable admittance controller with a classical admittance controller with fixed parameters as a baseline and an integer order variable admittance controller during a realistic drilling task. Our comparisons indicate that the proposed controller led to a more transparent interaction compared to the other controllers without sacrificing the stability. We also demonstrate a use case for an augmented reality (AR) headset which can augment human sensory capabilities for reaching a certain drilling depth otherwise not possible without changing the role of the robot as the decision maker. © 2020 IEEE.
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    Characterization of frequency-dependent material properties of human liver and its pathologies using an impact hammer
    (Elsevier, 2011) Dogusoy, Gulen; Tokat, Yaman; N/A; N/A; Department of Mechanical Engineering; Department of Mechanical Engineering; Özcan, Mustafa Umut; Öcal, Sina; Başdoğan, Çağatay; Master Student; Master Student; Faculty Member; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; 125489
    The current methods for characterization of frequency-dependent material properties of human liver are very limited. In fact, there is almost no data available in the literature showing the variation in dynamic elastic modulus of healthy or diseased human liver as a function of excitation frequency. We show that frequency-dependent dynamic material properties of a whole human liver can be easily and efficiently characterized by an impact hammer. The procedure only involves a light impact force applied to the tested liver by a hand-held hammer. The results of our experiments conducted with 15 human livers harvested from the patients having some form of liver disease show that the proposed approach can successfully differentiate the level of fibrosis in human liver. We found that the storage moduli of the livers having no fibrosis (F0) and that of the cirrhotic livers (F4) varied from 10 to 20 kPa and 20 to 50 kPa for the frequency range of 0-80 Hz, respectively.
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    Role allocation through haptics in physical human-robot interaction
    (Institute of Electrical and Electronics Engineers (IEEE), 2013) N/A; N/A; Department of Computer Engineering; Department of Mechanical Engineering; Department of Computer Engineering; Department of Mechanical Engineering; Küçükyılmaz, Ayşe; Sezgin, Tevfik Metin; Başdoğan, Çağatay; PhD Student; Faculty Member; Faculty Member; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; N/A; 18632; 125489
    This paper presents a summary of our efforts to enable dynamic role allocation between humans and robots in physical collaboration tasks. A major goal in physical human-robot interaction research is to develop tacit and natural communication between partners. In previous work, we suggested that the communication between a human and a robot would benefit from a decision making process in which the robot can dynamically adjust its control level during the task based on the intentions of the human. In order to do this, we define leader and follower roles for the partners, and using a role exchange mechanism, we enable the partners to negotiate solely through force information to exchange roles. We show that when compared to an “equal control” condition, the role exchange mechanism improves task performance and the joint efficiency of the partners.
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    Adaptive human force scaling via admittance control for physical human-robot interaction
    (IEEE Computer Soc, 2021) Aydın, Yusuf; N/A; Department of Mechanical Engineering; Department of Mechanical Engineering; Al Qaysi, Yahya Mohey Hamad; Başdoğan, Çağatay; PhD Student; Faculty Member; Graduate School of Sciences and Engineering; College of Engineering; N/A; 125489
    The goal of this article is to design an admittance controller for a robot to adaptively change its contribution to a collaborative manipulation task executed with a human partner to improve the task performance. This has been achieved by adaptive scaling of human force based on her/his movement intention while paying attention to the requirements of different task phases. In our approach, movement intentions of human are estimated from measured human force and velocity of manipulated object, and converted to a quantitative value using a fuzzy logic scheme. This value is then utilized as a variable gain in an admittance controller to adaptively adjust the contribution of robot to the task without changing the admittance time constant. We demonstrate the benefits of the proposed approach by a pHRI experiment utilizing Fitts' reaching movement task. The results of the experiment show that there is a) an optimum admittance time constant maximizing the human force amplification and b) a desirable admittance gain profile which leads to a more effective co-manipulation in terms of overall task performance.
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    Finite element modeling of a vibrating touch screen actuated by piezo patches for haptic feedback
    (Springer, 2012) N/A; N/A; Department of Mechanical Engineering; Department of Mechanical Engineering; Baylan, Buket; Arıdoğan, Mustafa Uğur; Başdoğan, Çağatay; Master Student; PhD Student; Faculty Member; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; 125489
    The aim of our work is to design a touch screen for displaying vibrotactile haptic feedback to the user via piezo patches attached to its surface. One of the challenges in the design is the selection of appropriate boundary conditions and the piezo configurations (location and orientation) on the screen for achieving optimum performance within the limits of human haptic perception. To investigate the trade-offs in our design, we developed a finite element model of the screen and four piezo actuators attached to its surface in ABAQUS. The model utilizes the well-known Hooke's law between stress and strain extended by piezoelectric coupling. After selecting the appropriate boundary condition for the screen based on the range of vibration frequencies detectable by a human finger, the optimum configuration for the piezo patches is determined by maximizing the vibration amplitude of the screen for a unit micro Coulomb charge applied to each piezo patch. The results of our study suggest that the piezo patches should be placed close to the clamped sides of the screen where the boundary conditions are applied. © 2012 Springer-Verlag.
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    Electroadhesion with application to touchscreens
    (Royal Soc Chemistry, 2019) Ayyıldız, Mehmet; Persson, Bo N. J.; N/A; Department of Mechanical Engineering; Department of Mechanical Engineering; Şirin, Ömer; Başdoğan, Çağatay; PhD Student; Faculty Member; Graduate School of Sciences and Engineering; College of Engineering; N/A; 125489
    There is growing interest in touchscreens displaying tactile feedback due to their tremendous potential in consumer electronics. In these systems, the friction between the user's fingerpad and the surface of the touchscreen is modulated to display tactile effects. One of the promising techniques used in this regard is electrostatic actuation. If, for example, an alternating voltage is applied to the conductive layer of a surface capacitive touchscreen, an attractive electrostatic force is generated between the finger and the surface, which results in an increase in frictional forces acting on the finger moving on the surface. By altering the amplitude, frequency, and waveform of this signal, a rich set of tactile effects can be generated on the touchscreen. Despite the ease of implementation and its powerful effect on our tactile sensation, the contact mechanics leading to an increase in friction due to electroadhesion has not been fully understood yet. In this paper, we present experimental results for how the friction between a finger and a touchscreen depends on the electrostatic attraction and the applied normal pressure. The dependency of the finger-touchscreen interaction on the applied voltage and on several other parameters is also investigated using a mean field theory based on multiscale contact mechanics. We present detailed theoretical analysis of how the area of real contact and the friction force depend on contact parameters, and show that it is possible to further augment the friction force, and hence the tactile feedback displayed to the user by carefully choosing those parameters.