Lateral Touch and Frictional Vibrations of Human Fingerprints

In this report, we experimentally show that human fingerprints play a significant role in the lateral touch vibratory mechanisms and that direction of movement results in differ-ent dynamic strains on the pulp. Sources that generate sound at the interface are first empiri-cally identified and a spherical model of the index finger is proposed to forecast the radiated fields. Then, haptic sounds are recorded using a miniature microphone placed in the near field. Results are compared with vibrometric measurements carried out in quite similar conditions to assess of the results relevance. Results show that fingerprints can?t be neglected in the tri-bologic interaction. Finally, this research provide a useful information for tactile displays de-signers and offers future investigations perspectives in many research fields linked with the haptic science

Unstable Sense of Agency under Consistent Force Feedback

The present study undertakes an ecological approach to haptic interfaces grounded in the sense of agency that accompanies human action. The study had two aims. The first aim was to investigate the effect of two top-down cues (perceived initiation of action and presence of action options) on sense of agency in haptic interfaces. The second aim was to investigate the consistency of the sense of agency and answer the question whether consistent force feedback (bottom-up cue) is sufficient to grant stable experience of agency. The results of the study suggest that while high number of action options can be associated with stronger agency, low numbers of action options are unlikely to produce such effect, and that the cue of task completion might be critical for the sense of agency. The study also showed that sense of agency was relatively inconsistent, with the main source of uncertainty being computer-attributed agency. The discussion addresses issues of joint human-computer agency and the contribution of multiple sources of information to agency experience

Tactile perception of spatially distributed vibratory stimuli on the fingerpad

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.Includes bibliographical references (p. 86-87).Using a pin-array type tactile display as a stimulator of the finger pad, a psychophysical study was conducted on the vibrotactile perception. The passive touch with vibratory stimuli in the low frequency could be an alternative of the active touch for the presented stimuli: polygons, round shapes and gratings. As for the effect of frequency on the texture discrimination, the high correct answer proportions corresponded to the most sensitive frequency ranges of each mechanoreceptor. The spatial acuity decreased as the frequency of the stimuli increased when the stimuli presented by the equal number of contactors. As an analogy between color vision and tactile perception, a spatial configuration of the multiple contactors was proposed to deliver the intermediate pitch using the compound waveform defined as a sinusoidal stimulus which was presented by four contactors vibrating with 30Hz and 240Hz. The subjects felt qualitatively different the compound waveform and the pure-tone.(cont.) When the high frequency component had 3 times the intensity of the other component, the perceived frequency of the compound waveform was about 120Hz which was much lower than the component frequency 240Hz. The experimental results were explained by the hypothesis of a ratio code, neural mechanism signaling the frequency of vibratory stimuli based on the ratio of the one-to-one activated population of mechanoreceptors. In addition, the intensity of the components also affected the overall perceived frequency.by Minseung Ahn.S.M

Design and fabrication of flexible tactile sensing and feedback interface for communication by deafblind people

Humans generally interact and communicate using five basic sensory modalities and mainly through vision, touch and audio. However, this does not work for deafblind people as they have both impaired hearing and vision modalities, and hence rely on touch-sensing. This necessitates the development of alternative means that allows them to independently interact and communicate. To do this requires a solution which has the capability for tactile sensing and feedback. Therefore, tactile interface becomes a critical component of any assistive device usable by deafblind people for interaction and communication. Given that existing solutions mainly use rigid and commercial components, there is a need to tap into the advancements in flexible electronics in order develop more effective and conformable solutions. This research involves the development of flexible tactile communication interface usable in assistive communication devices for deafblind people. First, commercial sensors and actuators were utilised as a proof-of-concept and then four novel tactile interfaces were explored which include two similar touch-sensitive electromagnetic actuators, one capacitive tactile sensing array, and a facile flexible inductance-based pressure sensor. The two fabricated touch-sensitive electromagnetic actuators (Type 1 and 2) are both based on electromagnetic principle and capable of simultaneous tactile sensing and feedback. Each comprises of a tandem combination of two main modules - the touch-sensing and the actuation module, with both modules integrated as a single device in each case. The actuation module employs a flexible planar spiral coil and a Neodymium magnet assembled in a soft Polydimethylsiloxane (PDMS) structure, while the touch-sensing module is a planar capacitive metal- insulator-metal structure of copper. The flexible coil (~17µm thick and with 45 turns) was fabricated on a Polyimide sheet using Lithographie Galvanoformung Abformung (LIGA) process. The results of characterisation of these actuators at frequencies ranging from 10Hz to 200Hz, shows a maximum displacement (~ 190µm) around 40Hz. Evaluation of this by 40 (20 deafblind and 20 sighted and hearing) participants show that they can feel vibration at this range. Another tactile interface fabricated is an 8 x 8 capacitive tactile sensing array. The sensor was developed on a flexible Polyvinyl Chloride (PVC) sheet with column electrodes deposited on one side and row electrodes on the reverse side. It is intended for use as an assistive tactile communication interface for deafblind people who communicate using deafblind manual alphabets as well as the English block letters. An inductance-based pressure sensor was also designed, fabricated and characterised for use as an input interface for finger Braille as well as other tactile communication methods for deafblind people. It was realised with a soft ferromagnetic elastomer and a 17µm-thick coil fabricated on a flexible 50 µm-thick polyimide sheet. The ferromagnetic elastomer acts as the core of the coil, which when pressed, sees the metal particles moving closer to each other, leading to changes in the inductance. The coil, with 75µm conductor and 25µm pitch, was also realised using LIGA micromolding technique. Seven different sensors were fabricated using different ratios (1:1, 1:2, 1:3, 1:5, 2:1, 3:1, and 5:1) of Ecoflex to Iron particles. The performance of each sensor was investigated and generally, sensors with higher Iron particles gave better sensitivity, linear as well as dynamic range. In comparison with all other fabricated sensors, the sensor made with 1:5DD was recommended for application as a tactile interface

Taktile Interaktion auf flächigen Brailledisplays

Für den Zugang zu grafischen Benutzungsoberflächen (GUIs) stehen blinden Menschen so genannte Screenreader und Braillezeilen zur Verfügung. Diese ermöglichen zwar das nicht-visuelle Wahrnehmen textueller Inhalte, allerdings kein effektives Arbeiten mit bildlichen Darstellungen. Neuartige taktile Flächendisplays können eine geeignete Lösung für den interaktiven Zugang zu tastbaren Grafiken darstellen und somit die Interaktionsmöglichkeiten blinder Benutzer im Umgang mit grafischen Anwendungen bereichern. Beispielsweise erlauben derartige Geräte nicht nur das Erkunden räumlicher Anordnungen, sondern darüber hinaus auch die kombinierte Ausgabe von Braille, Grafik und semi-grafischen Elementen. Um die deutlich größere Menge an gleichzeitig darstellbaren Informationen beherrschbar zu machen, sind neben entsprechenden Inhaltsaufbereitungen und Navigationsmechanismen auch geeignete Orientierungshilfen bereitzustellen. Im Rahmen der vorliegenden Arbeit wurde am Beispiel der BrailleDis Geräte der Metec AG, welche eine taktile Ausgabefläche von 120 mal 60 Stiften bereitstellen, untersucht, inwieweit flächige Brailledisplays blinden Menschen eine effektive und effiziente Bedienung grafischer Benutzungsoberflächen ermöglichen. Neben dem Zugang zur GUI selbst sowie dem Lesen von Texten stellt dabei insbesondere das Arbeiten mit Grafiken einen wichtigen Aspekt dar. Um die Bedienung auf einem taktilen Flächendisplay zu erleichtern, ist eine konsistente Organisation der Inhalte hilfreich. Hierfür wurde ein neuartiges taktiles Fenstersystem umgesetzt, welches die Ausgabe nicht nur in mehrere disjunkte Bereiche unterteilt, sondern auch verschiedene taktile Darstellungsarten unterstützt. Zur Systematisierung der Gestaltung und Evaluation derartiger taktiler Benutzungsoberflächen sowie der darin stattfindenden Benutzerinteraktionen wurde zunächst eine Taxonomie erarbeitet. Dabei wurden neben der Interaktion selber, welche durch die Ein-und Ausgabe sowie die Handbewegungen des Benutzers beschrieben werden kann, auch die Benutzerintention in Form von taktilen Elementaraufgaben sowie die technischen Spezifikationen des Geräts mit einbezogen. Basierend auf der Taxonomie wurden anschließend relevante Aspekte identifiziert, welche in mehreren Benutzerstudien mit insgesamt 46 blinden und hochgradig sehbehinderten Menschen untersucht wurden. Die betrachteten Untersuchungsfragen betrafen dabei einerseits die Effektivität der Ausgabe in Form verschiedener taktiler Ansichtsarten sowie die Eingabe und Erkundung durch den Benutzer, andererseits auch Aspekte zur Effizienz konkreter Interaktionstechniken. Als Ergebnis der einzelnen Studien wurden abschließend konkrete Empfehlungen zur Umsetzung von Benutzungsoberflächen auf flächigen Brailledisplays gegeben. Diese beinhalten insbesondere Aspekte zur Ergonomie von taktilen Flächendisplays, zur Anzeige von textuellen Inhalten, zur Darstellung und Interaktion mit grafischen Inhalten sowie zu Orientierungshilfen. Insgesamt konnte mit Hilfe der Benutzerstudien gezeigt werden, dass flächige Brailledisplays blinden Menschen einen effektiven und effizienten Zugang zu grafischen Benutzungsoberflächen ermöglichen. Verschiedene taktile Darstellungsarten können dabei das Lösen unterschiedlicher Aufgaben unterstützen. Generell erfordert die flächige Interaktion vom Benutzer allerdings auch die Erweiterung seiner konventionellen Erkundungs-und Eingabestrategien. Die Bereitstellung neuartiger Interaktionstechniken zur Unterstützung der Orientierung kann die Effizienz zusätzlich steigern.Blind people normally use screen readers as well as single-lined refreshable Braille displays for accessing graphical user interfaces (GUIs). These technologies allow for a non-visual perception of textual content but not for an effective handling of visual illustrations. Novel two-dimensional tactile pin-matrix devices are an appropriate solution to interactively access tactual graphics. In this way, they can enrich the interaction possibilities of blind users in dealing with graphical applications. For instance, such devices enable the exploration of spatial arrangements and also combine output of Braille, graphics and semi-graphical elements. To make the high amount of simultaneously presented information perceivable and efficiently usable for blind users, an adequate preparation of content as well as adapted navigation and orientation mechanisms must be provided. In this thesis the BrailleDis devices of Metec AG, which have a tactile output area of 120 times 60 pins, were used. The goal was to investigate to what extent large pin-matrix devices enable blind people to use graphical user interfaces effectively and efficiently. Access to the GUI itself, reading text, and dealing with graphics are the main aspects of the application area of such devices. To facilitate the operation on a two-dimensional pin-matrix device a consistent organization of the content is helpful. Therefore, a novel tactile windowing system was implemented which divides the output area into multiple disjunctive regions and supports diverse tactile information visualizations. Moreover, a taxonomy was developed to systematize the design and evaluation of tactile user interfaces. Apart from interaction that can be described by input and output as well as hand movements, the taxonomy includes user intention in terms of interactive task primitives and technical specifications of the device. Based on the taxonomy, relevant aspects of tactile interaction were identified. These aspects were examined in multiple user studies with a total of 46 blind and visually impaired participants. The following research topics were considered during the user studies: 1. the effectiveness of diverse tactile view types (output), 2. user input and exploration, and 3. the efficiency of specific interaction techniques. As a result, practical recommendations for implementing user interfaces on two-dimensional pin-matrix devices were given. These recommendations include ergonomic issues of physical devices as well as design considerations for textual and graphical content as well as orientation aids. In summary, the user studies showed that two-dimensional pin-matrix devices enable blind people an effective and efficient access to graphical user interfaces. Diverse tactile information visualizations can support users to fulfill various tasks. In general, two-dimensional interaction requires the extension of conventional exploration and input strategies of users. The provision of novel interaction techniques for supporting orientation can help to increase efficiency even more