Haptic perception serves as one of our primary interfaces to the physical world. Without it, our ability to understand and respond to a world full of objects and physical beings would be profoundly impaired.
This dissertation addresses how we reconstruct perceptual representations from the mechanical inputs that occur during haptic interactions. It focuses on the behaviorally relevant information that allows the somatosensory system to achieve its goals, such as enabling the exploration and dexterous manipulation of objects.
The dissertation covers fundamental concepts related to the emergence of stable haptic percepts and presents a series of experimental studies spanning topics from contact detection, through texture and material perception, to the perception of time during haptic interactions. The studies reveal several fundamental mechanisms in haptic perception: an intensity metamer in impact detection where duration and amplitude trade off, the role of propagating vibratory waves for roughness perception, and roughness metamers where different combinations of elasticity and surface features produce identical percepts.
Using a novel dual-property stimulus database and local anesthesia techniques, the work further highlights the crucial role of cutaneous information in softness perception and shows how the lack of cutaneous information can influence the perceived timing of haptic interactions.
Together, the studies uncover essential cues and mechanisms used to perceptually reconstruct different haptic interactions. ... Read more

An integral part of creating compelling and useful immersive virtual environments is the presence of haptic feedback, where both kinesthetic and cutaneous feedback convey unique information critical to object handling and manipulation. State-of-the-art haptic gloves are broadening the workspace and degrees of freedom for hand motion in VR, adding force and vibrotactile feedback to the user's hand and fingers. The effect of each feedback modality to task performance remains unclear. In the current proof-of-concept study we added high-frequency vibrotactile actuators onto a resistive force-feedback glove, to illustrate how our proposed analysis method might contribute to the field of human factors studies. We aim to identify improvements to a haptic glove by isolating the contribution of both haptic feedback modalities, that is the force and vibrotactile feedback. Haptic gloves are used to train the fine motor control skills for assembly operations, allowing the users to grasp objects in an natural manner. By tracking the Finger Indentation -- the distance that a fingertip travels into the virtual surface of the grasped object -- we can capture the grasping realism achieved by each haptic condition. This approach allows us to explore the differences between expected physical world behavior and corresponding behavior in a virtual environment. To determine if our proposed metric provides insights into human behavior, we perform a within-subject comparison of a simplified assembly task in virtual reality with 3 participants. Participants are asked to perform a pick-and-place task for 4 conditions: no feedback, vibrotactile feedback, force feedback, and combined feedback. Performance is judged by analysing task completion time, finger indentation, and subjective measurements. The results of this proof-of-concept study suggest that the combined feedback condition performs better in terms of lower thumb indentations and higher usefulness and satisfactory scores than the no feedback and vibrotactile feedback conditions. It is notable that the vibrotactile feedback condition did not seem to out-perform the no-feedback condition. Regardless, the finger indentation metric seems to be a valid method to compare feedback modalities for grasping performance in a full-sized human factors study. ... Read more

Arthur C. Clarke said: “Any sufficiently advanced technology is indistinguishable from magic,” and cutting edge Virtual Reality (VR) certainly is quite the illusion. VR opens to us a near infinite set of worlds and possibilities. Comprehensive, Immersive, Virtual Environments (IVEs) will change the way we shop, explore, love and live. They’ll close the gap between our digital imaginations and our physical limitations. The barrier to this vision is that right now, IVEs don’t feel real. We may have breathtaking, high resolution displays, and compelling comprehensive spatial audio, but when we reach out and touch the digital world of an IVE, we’re left holding nothing. In this thesis, I propose a solution to this challenge, redesigning one of the most common VR ecosystems -- Oculus -- to contain cutting edge vibrotactile effects and actuators. The following pages lay out a narrative for a product -- the Oculus inTouch controller -- that balances performance, comfort, immersion and realism; yet remains accessible, flexible, and compelling. More than a product, I introduce an approach -- Interaction Centric Design -- to take haptics from the intangible world of psychophysics, and the nuanced and intricate world of the engineer, placing it within the grasp of the designer. I define a new theory -- Haptic Cuing -- predicated on guiding user behavior through the careful selection of haptic signal to avoid producing haptic noise. Over these next pages, I outline my journey into and through the world of haptics. I explain my process, my theory, and my path to designing what I hope is a foundational piece of haptic interfaces to come. ... Read more

A necessity in driving simulation testing is to understand and attenuate simulator sickness in urban environments to reduce the number of undesired drop-outs. This final thesis explains a 6 degree-of-freedom simulator sickness prediction model based on observer theory including the visual system. The model incorporates state-of-the-art knowledge of human spatial orientation perception and qualitative theories that try to explain motion sickness. Predictions are made regarding the simulator sickness incidence and expected rotary and translational motions for different motion and sensory paradigms. A between-subjects experiment was conducted to verify the model. Furthermore, the effect of adding scaled, but veridical, yaw motion to a simulator on the sickness incidence and severity while driving in urban environments was investigated. Participants were required to indicate a misery scale score every minute and to fill in the simulator sickness questionnaire prior to and after the experiment. Additionally, the perceived motion incongruence was measured together with head movements. Three cases were considered; a no-motion case, a case with a scaled yaw movement and a case with a scaled yaw movement together with pitch and roll motions. A significant relationship has been found between the simulator sickness prediction model outputs and the experimental outputs. Therefore, the model with the implemented visual system could be used to better understand
and predict simulator sickness. A significant relationship has also been found between the measured perceived motion incongruence and the simulator sickness incidence. This perceived motion incongruence can be used to quantify a part of the qualitative sensory rearrangement theory. Furthermore, humans that indicated lower sickness scores, moved their head significantly more along with the direction of the curve. Head movement strategies can be taught to participants of simulator studies to attenuate simulator sickness symptoms. Finally, significantly less participants dropped out in the cases that included simulator motion when driving in urban environments. The findings in this final thesis could assist in attenuating the number of drop-outs during driving simulation testing in urban scenarios. ... Read more

This document details a lab study into bimanual synchronised haptics, followed by the design of a product that can be used in combination with the SenseGlove to provide their wearer with haptic feedback based on how they operate a steering mechanism in Virtual Reality. The Dutch Ministry of Defense approached SenseGlove B.V., a company specialised in haptic gloves, to develop a Proof of Principle of the potential of haptic gloves in combination with Virtual Reality as a replacement for their high fidelity combat vehicle simulators. This project was split into two parts, a kinematic arm that can block the user’s motions so a person can no longer more their physical hands through digital objects, and a tactile palm strap that provides haptic feedback to the palm of the user to convey the motion of a digital steering mechanism. The kinematic arm was designed internally, and the tactile palm strap was taken as the focus of this graduation project.

An explorative Literature Study was conducted to find the ideal locations for haptic feedback on the human palm, as well as their corresponding types. These feedback locations and types were evaluated using a method called Interaction Prototyping. Based on the results of this study, a Lab Study was set up to evaluate three types of haptic feedback on the palm of the user. For this Study, a prototype haptic interface was made that could provide all three types of haptic feedback.

The outcome of the Lab Study was inconclusive because of a low sample size and many confounding factors. While the results were unsuitable to base a feedback choice on, the confounding factors resulted in valuable Design Challenges. The choice to go for vibrotactile feedback was made based on other factors such as cost, ease of production and company preference. The design challenges formed the basis for the Ideation Phase.

Product Ideas were generated using various creative techniques, and a Morphological Chart was made to condense the ideas into three Product Concepts. One Concept inspired by competitive gloves, one Concept inspired by damping materials, and one Concept inspired by the fingers of the user. Through the aid of a Harris Profile, the choice was made to further embody the concept inspired by the fingers of the user: The Finger Folds.

The Finger Folds form a modular addition to the SenseGlove that can easily be connected and disconnected from the company’s flagship product. It consists of four modules that each provide haptic feedback to the ideal region on the palm of the user independently of one another. Each module is connected to a finger, which automatically aligns the product and keeps the haptic feedback consistent during use, no matter how extreme holds their fingers or folds their hand. Signal consistency is maintained through constant skin contact. The modules can easily be attached to or detached from a Hub that is located between the SenseGlove and the back of the user’s hand. This Hub handles the information communication between the SenseGlove, Virtual Reality and each of the modules. ... Read more

—Enabling haptic interaction with non-solid materials, such as liquids or sediments, could expand possibilities for exploration of virtual or remote environments, which would e.g enable training divers and astronauts in simulators. To allow application of natural investigation procedures in such scenarios, haptic interfaces with several degrees of freedom (DOF) are necessary, which allow the interaction with a variety of solid objects as well as different surrounding mediums. The goal of this work is to develop an algorithm for a high-DOF hand exoskeleton as haptic interface connected to five points on the human hand, that enables the perception of virtual fluids by rendering the fluids’ prominent proprioceptive characteristic (viscosity). To allow simultaneous rendering of virtual solid objects of varying stiffness, a high update rate should be maintained. To quantify human perception of the rendered fluid, two user studies are carried out. The first investigates the ability to perceive fluids of low viscosity such as water, while the second deals with the discrimination ability for higher viscous virtual fluids. For virtual fluids with low viscosity, it is found that a linear relationship exists between the rendered and perceived viscosity with a scaling factor of 2. Fluids with high viscosity (> 10 Pa s) can be discriminated well, achieving similar values for the Weber fractions (w = 0.3) as are found in real interactions with fluids. The results of both experiments prove that properties of fluids rendered using simplified models to allow high update frequencies (833 Hz) can still be discriminated by human users. ... Read more

This thesis describes the design process to enhance the music festival experience for hearing-impaired people. This assignment was set up to make the MOJO backstage exhibition at Museum Prinsenhof Delft inclusive for hearing-impaired people. First, context mapping research with hearing-impaired and hearing festival visitors shows that inclusiveness at festivals is less present for hearing-impaired. To include hearing-impaired, the focus is to minimize the language barrier and create an independent and equal interaction. Combining the mapping information with desktop research and a sensitizing experiment, resulted in socio-cultural dimension diagrams (Hofstede, 2018) which compare hearing and deaf cultures. Differences conclude that deaf culture is more together, emotionally expressive and contextual. With music experience being one of the main reasons for people to visit festivals, for hearing impaired this is experienced through vibrations, live performances and dancing audiences during a music festival. In current products and theories music characteristics are often literally translated to structures of the tactile and/or visual sense, because they are capable to change over time and have a wide variety. Unfortunately, most of these abstract theories and products are not able to convey the same emotional response as people who hear songs via sound. Therefore, a test with hearing people was performed to find similarities in emotional response to music of hearing and hearing-impaired people. Hearing people were asked to elaborate on Justlin and Vastfall’s (2008) emotional responses to music. Similarities between the answers given in this test and interviews with hearing-impaired, were found within two of the categories; emotional contagion and rhythmic entrainment. During interviews and observations at several festivals, using current solutions like the Lofelt bracelet and signdance shows. It was discovered that rhythmic entrainment is experienced by hearing-impaired people by feeling bass through vibrations of speakers or floors. Emotional contagion is experienced by dance moves and facial expression of a crowd or performers on stage. The goal of this study is to design a product that uses visual dance and vibrations of the bass as means to create an inclusive interaction between hearing-impaired and hearing festival visitors. This is done by an interactive dance game that is played during a live concert. The game is played by mimicking dance moves on the beat, while the beat is felt by vibrations of the bass. A concept test concluded that the game is inclusive because it was played just as well by hearing as hearing-impaired people. Also, bystanders joined the dance game without being an actual participant. This effect is expected to be even bigger in the festival context. Hearing-impaired people mention to feel more independent and confident at a festival when using a product like this. It would be interesting to develop a portable (smartphone) version to be independent of a location. Further research could be done to develop the character into a fully automated (sign) dance character which would make hearing-impaired fully independent of their peers at every location in time.
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