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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/3
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Item Metadata only Tactile perception of coated smooth surfaces(Institute of Electrical and Electronics Engineers Inc., 2023) 0000-0002-2443-8416; N/A; 0000-0002-6382-7334; Sezgin, Alperen; Er, Utku; Turkuz, Seniz; N/A; N/A; Department of Mechanical Engineering; Aliabbasi, Easa; Aydıngül, Volkan; Başdoğan, Çağatay; PhD Student; Master Student; Faculty Member; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; 125489Although surface coating is commonly utilized in many industries for improving the aesthetics and functionality of the end product, our tactile perception of coated surfaces has not been investigated in depth yet. In fact, there are only a few studies investigating the effect of coating material on our tactile perception of extremely smooth surfaces having roughness amplitudes in the order of a few nanometers. Moreover, the current literature needs more studies linking the physical measurements performed on these surfaces to our tactile perception in order to further understand the adhesive contact mechanism leading to our percept. In this study, we first perform 2AFC experiments with 8 participants to quantify their tactile discrimination ability of 5 smooth glass surfaces coated with 3 different materials. We then measure the coefficient of friction between human finger and those 5 surfaces via a custom-made tribometer and their surface energies via Sessile drop test performed with 4 different liquids. The results of our psychophysical experiments and the physical measurements show that coating material has a strong influence on our tactile perception and human finger is capable of detecting differences in surface chemistry due to, possibly, molecular interactions.Publication Metadata only 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; 125489The 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.Publication Metadata only Effect of waveform on tactile perception by electrovibration displayed on touch screens(IEEE Computer Soc, 2017) Guclu, Burak; N/A; Department of Mechanical Engineering; Department of Mechanical Engineering; Vardar, Yasemin; Başdoğan, Çağatay; PhD Student; Faculty Member; Graduate School of Sciences and Engineering; College of Engineering; N/A; 125489In this study, we investigated the effect of input voltage waveform on our haptic perception of electrovibration on touch screens. Through psychophysical experiments performed with eight subjects, we first measured the detection thresholds of electrovibration stimuli generated by sinusoidal and square voltages at various fundamental frequencies. We observed that the subjects were more sensitive to stimuli generated by square wave voltage than sinusoidal one for frequencies lower than 60 Hz. Using Matlab simulations, we showed that the sensation difference of waveforms in low fundamental frequencies occurred due to the frequency-dependent electrical properties of human skin and human tactile sensitivity. To validate our simulations, we conducted a second experiment with another group of eight subjects. We first actuated the touch screen at the threshold voltages estimated in the first experiment and then measured the contact force and acceleration acting on the index fingers of the subjects moving on the screen with a constant speed. We analyzed the collected data in the frequency domain using the human vibrotactile sensitivity curve. The results suggested that Pacinian channel was the primary psychophysical channel in the detection of the electrovibration stimuli caused by all the square-wave inputs tested in this study. We also observed that the measured force and acceleration data were affected by finger speed in a complex manner suggesting that it may also affect our haptic perception accordingly.Publication Metadata only Perception of skin stretch applied to palm: effects of speed and displacement(Springer International Publishing Ag, 2016) Provancher, William R.; N/A; Department of Mechanical Engineering; Department of Mechanical Engineering; Güzererler, Ahmet; Başdoğan, Çağatay; Researcher; Faculty Member; KU Arçelik Research Center for Creative Industries (KUAR) / KU Arçelik Yaratıcı Endüstriler Uygulama ve Araştırma Merkezi (KUAR); N/A; College of Engineering; N/A; 125489Skin stretch is a powerful haptic effect with a great potential as a feedback mechanism for digital gaming applications. For example, it has been shown to communicate directional information accurately to game players. However, the existing devices apply stretch to the tip of index finger except the Reactive Grip game controller by Tactical Haptics, which applies skin stretch to a user's palm and finger pads. We have designed a compact hand-held haptic device that applies skin stretch to the palm via an actuated tactor. Compared to the fingertip, the palm is slightly less sensitive to skin stretch but affords larger stretch area. The stretch area of the palm enables us to control both tactor displacement and speeds for a broader range, resulting in richer haptic feedback. Using this device, we conduct experiments with 8 participants to investigate the effects of tactor displacement, speed, direction and hand orientation on perceived magnitude of skin stretch. The results of the study show that not only the tactor displacement but also the speed has a significant effect on the perceived intensity of skin stretch and the mapping function between them is nonlinear. Moreover, it appears that the tactile sensitivity of human palm to skin stretch is not homogeneous and stretch applied to the radial aspect of palm (towards the thumb) results in higher intensity than that of ulnar aspect.Publication Metadata only Recognition of haptic interaction patterns in dyadic joint object manipulation(IEEE Computer Society, 2015) KucukYılmaz, Ayse; N/A; Department of Computer Engineering; Department of Mechanical Engineering; Department of Computer Engineering; Department of Mechanical Engineering; Madan, Çığıl Ece; Sezgin, Tevfik Metin; Başdoğan, Çağatay; Master Student; Faculty Member; Faculty Member; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; N/A; 18632; 125489The development of robots that can physically cooperate with humans has attained interest in the last decades. Obviously, this effort requires a deep understanding of the intrinsic properties of interaction. Up to now, many researchers have focused on inferring human intents in terms of intermediate or terminal goals in physical tasks. On the other hand, working side by side with people, an autonomous robot additionally needs to come up with in-depth information about underlying haptic interaction patterns that are typically encountered during human-human cooperation. However, to our knowledge, no study has yet focused on characterizing such detailed information. In this sense, this work is pioneering as an effort to gain deeper understanding of interaction patterns involving two or more humans in a physical task. We present a labeled human-human-interaction dataset, which captures the interaction of two humans, who collaboratively transport an object in an haptics-enabled virtual environment. In the light of information gained by studying this dataset, we propose that the actions of cooperating partners can be examined under three interaction types: In any cooperative task, the interacting humans either 1) work in harmony, 2) cope with conflicts, or 3) remain passive during interaction. In line with this conception, we present a taxonomy of human interaction patterns; then propose five different feature sets, comprising force-, velocity-and power-related information, for the classification of these patterns. Our evaluation shows that using a multi-class support vector machine (SVM) classifier, we can accomplish a correct classification rate of 86 percent for the identification of interaction patterns, an accuracy obtained by fusing a selected set of most informative features by Minimum Redundancy Maximum Relevance (mRMR) feature selection method.Publication Metadata only Tactile roughness perception of virtual gratings by electrovibration(IEEE Computer Society, 2020) Vardar, Yasemin; N/A; Department of Mechanical Engineering; Department of Mechanical Engineering; İşleyen, Aykut; Başdoğan, Çağatay; Master Student; Faculty Member; Graduate School of Sciences and Engineering; College of Engineering; N/A; 125489Realistic display of tactile textures on touch screens is a big step forward for haptic technology to reach a wide range of consumers utilizing electronic devices on a daily basis. Since the texture topography cannot be rendered explicitly by electrovibration on touch screens, it is important to understand how we perceive the virtual textures displayed by friction modulation via electrovibration. We investigated the roughness perception of real gratings made of plexiglass and virtual gratings displayed by electrovibration through a touch screen for comparison. In particular, we conducted two psychophysical experiments with ten participants to investigate the effect of spatial period and the normal force applied by finger on roughness perception of real and virtual gratings in macro size. We also recorded the contact forces acting on the participants' finger during the experiments. The results showed that the roughness perception of real and virtual gratings are different. We argue that this difference can be explained by the amount of fingerpad penetration into the gratings. For real gratings, penetration increased tangential forces acting on the finger, whereas for virtual ones where skin penetration is absent, tangential forces decreased with spatial period. Supporting our claim, we also found that increasing normal force increases the perceived roughness of real gratings while it causes an opposite effect for the virtual gratings. These results are consistent with the tangential force profiles recorded for both real and virtual gratings. In particular, the rate of change in tangential force (dF(t)/dt) as a function of spatial period and normal force followed trends similar to those obtained for the roughness estimates of real and virtual gratings, suggesting that it is a better indicator of the perceived roughness than the tangential force magnitude.Publication Metadata only Effect of waveform in haptic perception of electrovibration on touchscreens(Springer International Publishing Ag, 2016) Guclu, Burak; N/A; Department of Mechanical Engineering; Department of Mechanical Engineering; Vardar, Yasemin; Başdoğan, Çağatay; PhD Student; Faculty Member; Graduate School of Sciences and Engineering; College of Engineering; N/A; 125489The perceived intensity of electrovibration can be altered by modulating the amplitude, frequency, and waveform of the input voltage signal applied to the conductive layer of a touchscreen. Even though the effect of the first two has been already investigated for sinusoidal signals, we are not aware of any detailed study investigating the effect of the waveform on our haptic perception in the domain of electrovibration. This paper investigates how input voltage waveform affects our haptic perception of electrovibration on touchscreens. We conducted absolute detection experiments using square wave and sinusoidal input signals at seven fundamental frequencies (15, 30, 60, 120, 240, 480 and 1920 Hz). Experimental results depicted the well-known U-shaped tactile sensitivity across frequencies. However, the sensory thresholds were lower for the square wave than the sinusoidal wave at fundamental frequencies less than 60 Hz while they were similar at higher frequencies. Using an equivalent circuit model of a finger-touchscreen system, we show that the sensation difference between the waveforms at low fundamental frequencies can be explained by frequency-dependent electrical properties of human skin and the differential sensitivity of mechanoreceptor channels to individual frequency components in the electrostatic force. As a matter of fact, when the electrostatic force waveforms are analyzed in the frequency domain based on human vibrotactile sensitivity data from the literature [15], the electrovibration stimuli caused by square-wave input signals at all the tested frequencies in this study are found to be detected by the Pacinian psychophysical channel.Publication Metadata only An investigation of haptic perception of viscoelastic materials in the frequency domain(IEEE Computer Society, 2018) N/A; Department of Mechanical Engineering; Department of Mechanical Engineering; Çaldıran, Ozan; Başdoğan, Çağatay; PhD Student; Faculty Member; Graduate School of Sciences and Engineering; College of Engineering; N/A; 125489Although 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°.Publication Metadata only Exploration strategies for tactile graphics displayed by electrovibration on a touchscreen(Academic Press Ltd- Elsevier Science Ltd, 2022) Ayyıldız, Mehmet; N/A; Department of Mechanical Engineering; Department of Mechanical Engineering; Sadia, Büshra; Sadıç, Ayberk; Başdoğan, Çağatay; PhD Student; Faculty Member; Graduate School of Sciences and Engineering; College of Engineering; N/A; 125489Advancements in surface haptics technology have given rise to the development of interactive applications displaying tactile content on touch surfaces such as images, signs, diagrams, plots, charts, graphs, maps, net-works, and tables. In those applications, users manually explore the touch surface to interact with the tactile data using some intuitive strategies. The user's exploration strategy, tactile data's complexity, and tactile rendering method all affect the user's haptic perception, which plays a critical role in designing and prototyping of those applications. In this study, we conducted experiments with human participants to investigate the recognition rate and time of five tactile shapes (i.e., triangle, square, pentagon, hexagon, and octagon) rendered by electro-vibration on a touchscreen using three different methods (electrovibration was active inside, on the edges, or outside the shapes), and displayed in prototypical orientations and non-prototypical orientations (i.e., 15 degrees CW and CCW to the prototypical orientation). The results showed that the correct recognition rate of the shapes was higher when the haptically active area (area where electrovibration was on) was larger. However, as the number of edges was increased, the recognition time increased and the recognition rate dropped significantly, arriving to a value slightly higher than the chance rate of 20% for non-prototypical octagon. Moreover, the recognition time for inside rendering condition was significantly shorter compared to edge and outside rendering conditions, and edge rendering condition led to the longest recognition time. We also recorded the participants' finger movements on the touchscreen to examine their haptic exploration strategies. Based on our temporal analysis, we classified six exploration strategies adopted by participants to identify the shapes, which were different for the prototypical and non-prototypical shapes. Moreover, our spatial analysis revealed that the participants first used global scanning to extract the coarse features of the displayed shapes, and then they applied local scanning to identify finer details, but needed another global scan for final confirmation in the case of non-prototypical shapes, possibly due to the current limitations of electrovibration technology in displaying tactile stimuli to a user. We observed that it was highly difficult to follow the edges of shapes and recognize shapes with more than five edges under electrovibration when a single finger was used for exploration.Publication Metadata only The future of books and reading in HCI(Association for Computing Machinery (ACM), 2016) Wozniak, Pawel W.; Lischke, Lars; Billinghurst, Mark; Department of Mechanical Engineering; Department of Media and Visual Arts; Department of Mechanical Engineering; Department of Media and Visual Arts; Obaid, Mohammad; Alaca, Ilgım Veryeri; Undergraduate Student; Faculty Member; College of Engineering; College of Social Sciences and Humanities; N/A; 50569Technology is fundamentally changing the reading experience and book design. While the invention of industry-scale printing transformed books into a mass product, interactive technology enables new types of engagement during reading. Books can have multifarious form factors; their visual representation can change in accordance to the environment and user needs. The aim of the workshop is to discuss emerging interactive book-related technologies (e.g. Augmented Reality or Tangible Interfaces) and elaborate on methodologies that can be used to evaluate content and the interplay between form and content. The workshop will investigate how novel technologies can inspire, support and enrich the reading experience.