Researcher:
Çaldıran, Ozan

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Ozan

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Çaldıran

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Çaldıran, Ozan

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2018 - 20203

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Researcher Of Publications: search.filters.isAuthorOfPublication.39891988-beb8-4ed4-b8e5-5d963a5858fa

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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; Başdoğan, Çağatay; Aydın, Yusuf; Şirintuna, Doğanay; Çaldıran, Ozan; Faculty Member; PhD Student; PhD Student; PhD Student; Department of Mechanical Engineering; 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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    An investigation of haptic perception of viscoelastic materials in the frequency domain
    (IEEE Computer Society, 2018) N/A; Department of Mechanical Engineering; Çaldıran, Ozan; Başdoğan, Çağatay; PhD Student; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 125489
    Although we hardly interact with objects that are purely elastic or viscous, haptic perception studies of deformable objects are mostly limited to stiffness and damping. Psychophysical investigation of materials that show both elastic and viscous behavior (viscoelastic materials) is challenging due to their complex, time and rate dependent mechanical behavior. In this study, we provide a new insight into the investigation of human perception of viscoelasticity in the frequency domain. In the frequency domain, the force response of a viscoelastic material can be represented by its magnitude and phase angle. Using this framework, we estimated the point of subjective equality (PSE) of a Maxwell arm (a damper and a spring in series) to a damper and a spring using complex stiffness magnitude and phase angle in two sets of experiments. A damper and a spring are chosen for the comparisons since they actually represent the limit cases for a viscoelastic material. We first performed 2I-2AFC adaptive staircase experiments to investigate how the perceived magnitude of complex stiffness changes in a Maxwell arm for small and large values of time constant. Then, we performed 3I-2AFC adaptive staircase experiments to investigate how the PSE changes as a function of the phase angle in a Maxwell arm. The results of our study show that the magnitude of complex stiffness was underestimated due to the smaller phase lag (with respect to a damper's) between the sinusoidal displacement applied by the participants to the Maxwell arm and the force felt in their finger when the time constant was small, whereas no difference was observed for a large time constant. Moreover, we observed that the PSE values estimated for the lower bound of the phase angle were significantly closer to their actual limit (0°) than those of the upper bound to 90°.
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    Visuo-haptic discrimination of viscoelastic materials
    (Institute of Electrical and Electronics Engineers (IEEE), 2019) Tan, Hong Z.; Department of Mechanical Engineering; Başdoğan, Çağatay; Çaldıran, Ozan; Faculty Member; Department of Mechanical Engineering; College of Engineering; Graduate School of Sciences and Engineering; 125489; N/A
    In our daily lives, we interact with different types of deformable materials. Regarding their mechanical behavior, some of those materials lie in a range that is between purely elastic and purely viscous. This range of mechanical behavior is described as viscoelasticity. In certain types of haptic interactions, such as assessment of ripeness of fruit, firmness of cheese, and consistency of organ tissue, we rely heavily on our haptic perception of viscoelastic materials. The relationship between the mechanical behavior of viscoelastic materials and our perception of them has been investigated in the field of psychorheology. However, our knowledge on how we perceive viscoelastic materials is still quite limited though some research work has already been done on purely elastic and purely viscous materials. History- and frequency-dependent behavior of viscoelastic materials result in a complex time-dependent response, which requires relatively more sophisticated models to investigate their behavior than those of purely elastic and viscous materials. In this study, we model viscoelasticity using a "springpot" (i.e., fractional-order derivative element) and express its behavior in the frequency domain using two physical parameters-"magnitude" and "phase" of complex stiffness. In the frequency domain, we are able to devise signal detection experiments where we can investigate the perception of viscoelastic materials using the perceptual terms of "firmness" and "bounciness," corresponding to the physical parameters of "magnitude" and "phase." The results of our experiments show that the just-noticeable difference (JND) for bounciness increases linearly with increasing "phase," following Webers law, while the JND for firmness is surprisingly independent of the level of "phase."