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Haptics Symposium 2018 – Proceedings

Contents - Abstracts - Authors

Front Matter

Title Page


Organizing Committee

Program Committee

WIP Editorial Board


Sponsor Organizations

Technical Papers

Oral Session 1: Cutaneous Contact

EIS: A Wearable Device for Epidermal Pressure Sensing
Zijie Zhu, Ruya Li, and Tingrui Pan
University of California at Davis, USA
The development of epidermal electronics provides an enabling means for continuous monitoring of physiological signals and physical activities without affecting the quality of life. Such devices require high sensitivity for low-magnitude signal detection, noise reduction for motion artifacts, wearability for long-term comfort, and low-cost production for scalable manufacturing. However, the current epidermal pressure sensing devices, usually involving complex multilayer structures, have not fully addressed the aforementioned challenges. In this paper, we have presented a novel epidermal iontronic sensing (EIS) device, that is, a novel wearable pressure sensor with a single-sided configuration and reversible attachability to human skin. Notably, incorporating skin as part of the sensing architecture, the EIS devices offer an excellent pressure sensitivity (5 nF/kPa), an ultrafast mechanical response (in a sub-millisecond range), and a good long-term stability (>10,000) for both internal (body) and external (environment) mechanical stimuli. Demonstrations of its versatile application to wearable scenarios include measuring blood pressure pulsations, monitoring respiration rates, tracking muscle activities, and digitalizing hand palpation and gripping.

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Imaging the 3-D Deformation of the Finger Pad When Interacting with Compliant Materials
Steven C. Hauser and Gregory J. Gerling
University of Virginia, USA
To accurately reproduce a sense of compliance in tactile displays, we must understand the physics of how the finger pad skin deforms. To this end, we developed a stereo imaging technique to visualize the skin through optically clear stimuli. The method achieves a 3-D spatial resolution of 60-120 microns and temporal resolution of 30 frames per second. With human subjects, we measured the skin’s deformation over a range of compliances (61-266 kPa), displacements (0-4 mm), and velocities (1- 15 mm/s). The method can differentiate patterns of skin deformation between compliances, as defined by new metrics such as surface penetration depth.

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Ferro-Fluid Based Portable Fingertip Haptic Display and Its Preliminary Experimental Evaluation
Harsimran Singh, Bhivraj Suthar, Syed Zain Mehdi, and Jee-Hwan Ryu
KOREATECH, South Korea
Numerous studies have been conducted to develop a tactile device for providing convincing tactile feedback. However, most of the devices are limited in portability, and restricted to delivering either texture information with vibration cues or contact orientation with force feedback. To the best of our knowledge, there has been no wearable tactile display, which can display texture information together with contact orientation. In this paper, we propose a ferro-fluid based tactile display, which is lightweight and wearable and can replicate convincing contact orientation together with texture information. New design principle of introducing ferro-fluid and minimizing moving actuator components and replacing them with permanent magnet, allows the device to be compact and increases its portability. This also enables it to provide both contact orientation and texture cues. Preliminary experimental evaluation for force profile on finger nail and finger tip has been carried out. In addition, experiments for curvature discrimination and cuing simultaneous orientation and vibrational information by using an experimental prototype have also been conducted.

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Separating Haptic Guidance from Task Dynamics: A Practical Solution via Cutaneous Devices
Evan Pezent, Simone Fani, Joshua Bradley, Matteo Bianchi, and Marcia K. O'Malley
Rice University, USA; University of Pisa, Italy
There is much interest in using haptic feedback for training new skills or guiding human movement. However, the results of studies that have incorporated haptic guidance to train new skills are mixed, depending on task complexity and the method by which the haptic guidance is implemented. Subjects show dependency on the guidance forces and difficulty in discerning which aspects of the haptic feedback are related to the task dynamics and which are meant to convey task completion strategies. For these reasons, new methods to separate haptic cues for guidance from haptic feedback of task dynamics are needed. In this experiment, 30 subjects completed a trajectory following task using a wrist exoskeleton which also rendered task forces. To assist subjects, guidance cues were provided in one of three forms: (1) cutaneous forces from a wearable skin-stretch device on the ipsilateral forearm and (2) contralateral forearm, and (3) kinesthetic forces from a kinematically similar wrist exoskeleton operated by the contralateral arm. The efficacies of each guidance condition are compared by examining subject performance and learning rates. The results indicate that cutaneous guidance is nearly as effective as kinesthetic guidance, making it a practical and cost-effective alternative for spatially separated assistance.

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A Skin Stretch Tactor for Sensory Substitution of Wrist Proprioception
Oguz Kayhan, A. Kemal Nennioglu, and Evren Samur
Boğaziçi University, Turkey
This paper presents a novel sensory feedback device and an original method aiming to provide skin stretch feedback of three degree-of-freedom wrist movements, which are extension-flexion, radial-ulnar deviation and pronation-supination, to prosthetic hand users. In order to evaluate the performance of the device, a test setup is built. A user study with able-bodied participants is conducted. Confusion matrices are created from the experimental data, and the results are analyzed in terms of correct identification of the intended stimulations. Analysis shows that the proposed design together with the sensory feedback method is a viable option for proprioceptive feedback lacking in robotic prosthetic hands.

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A Social Haptic Device to Create Continuous Lateral Motion using Sequential Normal Indentation
Heather Culbertson, Cara M. Nunez, Ali Israr, Frances Lau, Freddy Abnousi, and Allison M. Okamura
Stanford University, USA; University of Southern California, USA; Facebook, USA
Touch is an essential method for communicating emotions between individuals. Humans use a variety of different gestures to convey these emotions, including squeezes, pats, and strokes. This paper presents a device for creating a continuous lateral motion on the arm to mimic a subset of the gestures used in social touch. The device is composed of a linear array of voice coil actuators that is embedded in a fabric sleeve. The voice coils are controlled to sequentially press into the user's arm to create the sensation of linear travel up the arm. We evaluate the device in a human-subject study to confirm that a linear lateral motion can be created using only normal force, and to determine the optimal actuation parameters for creating a continuous and pleasant sensation. The results of the study indicated that the voice coils should be controlled with a long duration for each indentation and a short delay between the onset of indentation between adjacent actuators to maximize both continuity and pleasantness.

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Oral Session 2A: Control of Haptic Devices

Dynamic Model of Cable-Conduit Actuation for Interaction with Non-passive Environments
Andrew Borowski, Alexander Metz, and Fabrizio Sergi
University of Delaware, USA
In this paper, we present a new computational model for cable-conduit systems that describes interaction with non-passive environments. Unlike previous models, our model features bi-directional propagation of motion within the cable-conduit system. This allows for simulation of human-interacting systems where both the human and the robot have the capability to impose motion or force. Because of this feature, the developed model is applicable to a wide range of physical systems. The model is validated in a physical prototype through experiments involving physical interaction with a human subject. We show that our model accurately predicts behaviors observed in the experimental system.

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Rendering Mass using Model Matching Framework
Indrajit Desai, Abhishek Gupta, and Debraj Chakraborty
IIT Bombay, India
This paper presents a model matching based controller design technique to render mass using a haptic interface. The main hindrance in stably rendering mass through the open loop impedance control is the noise added to the acceleration signal due to twice differentiation of the position signal. We show that using model matching framework we can stably and accurately render desired mass. In addition, we present that effects of inherent dynamics such as damping present in the system can be minimized using the model matching framework. Further, we perform experiments on a single degree of freedom haptic device to validate our claim.

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The Impact of High-Frequency Haptic Device Behavior on Perception
Emma Treadway and R. Brent Gillespie
University of Michigan, USA
Haptic rendering is typically done through either impedance or admittance devices, which exist at opposite ends of a spectrum from light direct-drive to non-backdrivable highly geared. The device hardware necessarily influences what the user will feel, particularly at high frequencies. While human motion is generally limited to 10Hz, virtual environments with contact transitions have the potential to excite a wider frequency spectrum.
We employ the effective impedance decomposition to discuss the effects of hardware and controller selection outside of the rendering bandwidth. We also introduce an analysis of the admittance and impedance controllers with respect to sensitivity to load cell noise. Using a reconfigurable admittance/impedance device and a perceptual experiment, we explore these effects. We find that higher effective mass outside the rendering bandwidth leads to more confusion in discriminating springs in an admittance device than an impedance device.

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Performance and Stability Limitations of Admittance-Based Haptic Interfaces
Chembian Parthiban and Michael Zinn
University of Wisconsin-Madison, USA
In this paper, we describe an analytical model developed to investigate the performance limitations of admittance-based haptic interfaces. The model is used to investigate the effects that position control bandwidth and outer loop delay have on the stability and rendering range of an admittance-based interface. We show that the performance, as defined by both the minimum renderable mass and the rendering frequency range, is directly related to the closed-loop bandwidth of the inner-position loop and the amount of additional delay in the outer rendering loop. In addition, we show that the minimum renderable mass is directly proportional to the damping provided by the user which implies a stronger grip, with a higher damping, decreases the stable rendering region of the admittance-based haptics device as opposed to an impedance-based device where increased damping enhances stability Our results are validated using a one degree-of-freedom admittance-based device.

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The Effect of Discretization Techniques on Uncoupled Stability of Haptic Simulation Systems
Daniel Cleveland and Keyvan Hashtrudi-Zaad
Queen's University, Canada
Haptic simulation systems allow human users to kinesthetically interact with virtual environment models through a robotic mechanism known as a haptic interface. The range of environment dynamics that can be stably rendered in a haptic simulation system is determined by a number of factors, including the method by which the virtual environment is implemented in discrete-time domain. Uncoupled stability, the stability of the system when it is not interfaced to any user, is regarded as one of the most stringent stability conditions for impedance-type interfaces. In this work, we analytically and experimentally investigate the system uncoupled stability conditions for various discrete implementation of damper-spring environments when position or velocity is sampled. The results point at different ranges of environment dynamics suitable for various applications.

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Model-Reference Model-Mediated Control for Time-Delayed Teleoperation Systems
Leonam S. D. Pecly, Marcelo L. O. Souza, and Keyvan Hashtrudi-Zaad
National Institute for Space Research, Brazil; Queen's University, Canada
Time delays in bilateral teleoperation systems can degrade the transparency and result in instability. For large delays, model predictive control or impedance reflective methods in which the operator interacts with the slave and environment model, can help overcome this issue. An important key to the success of these systems is to have the local virtual slave model synchronized with the slave. This is especially important when the slave gets into contact with hard environments, resulting in rapid contact force build up and slave chattering. In this paper, we propose a model-reference model-mediated teleoperation control architecture that provides enhanced synchronization between the slave and virtual slave models and keeps both the master and slave responsive. The proposed architecture is evaluated against through simulations and experiments carried out on a 1-DOF master-slave testbed.

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Oral Session 2B: Actuation and Sensing

Improvement in Stiffness Performance of Force Feedback Devices with Ultrasonic Motors
Jian Song, Yuru Zhang, Hongdong Zhang, Dangxiao Wang, and Weiliang Xu
Beihang University, China; University of Auckland, New Zealand
In the design of a haptic device, it is difficult to achieve simultaneously high stiffness and low friction and inertia. In our previous research, we proposed a co-actuation method to overcome this difficulty. The method uses a physical constraint to simulate hard contact and allows the device move freely in free motion space by keeping a clearance between the physical constraint and the link of the device. A stiffness of 40N/mm and back-driving friction of less than 0.3N have been achieved in a co-actuation module of one degree-of-freedom (DOF) using an electromagnetic motor and gear reducer. However, the stiffness is not high sufficient (10N/mm) at the initial contact due to the backlash in the transmission. In this paper, we explore the possibility to use an ultrasonic motor (USM) for solving this problem. Compared with the electromagnetic motor used in the early design, the USM is able to generate a larger resistant torque without gearbox, at a fast rate. We develop a model to determine the maximum clearance between the physical constraint and the link. We verify the clearance model and the force feedback performance using a one DOF haptic device. The experimental results show that the device achieves a stiffness of 61.5N/mm and back-driving friction less than 0.4N, which implies that the USM is promising for achieving both high stiffness and low friction and inertia required by the haptic application.

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Combination of Cathodic Electrical Stimulation and Mechanical Damped Sinusoidal Vibration to Express Tactile Softness in the Tapping Process
Vibol Yem and Hiroyuki Kajimoto
University of Electro-Communications, Japan
A damped sinusoidal vibration is generally used to reproduce the sensation of tapping. However, the type of actuator generally used in the field of tactile display cannot produce very low-frequency vibrations, and thus cannot activate Merkel cells to produce the sensation of cutaneous pressure. In this study we propose a method that combines cathodic electrical stimulation, which produces a pressure-like sensation, with a mechanical damped sinusoidal vibration. Our experiment demonstrated that the cutaneous pressure sensation produced by cathodic electrical stimulation mostly affects the perception of softness, allowing our method to reproduce sensations of softness/hardness over a wider range than when using mechanical vibration alone. Most participants felt that the combination of these two stimulations provided a more realistic tapping sensation.

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Object Surface Exploration using Low-Cost Rolling Robotic Fingertips
Yoav Golan, Amir Shapiro, and Elon Rimon
Ben-Gurion University of the Negev, Israel; Technion, Israel
Tactile sensors are numerous and varied, and the data they provide has proven advantages in industrial and consumer products. Despite this fact, these sensors are not used to their full potential. This illustrates the need for low-cost, versatile tactile sensors. In this paper we introduce novel robotic fingertips that use low-cost components coupled with mechanical ingenuity in order to attain important and high-quality tactile data. Our robotic fingertips contain a rolling mechanism, and can sense the force applied to an object, the normal direction of the contact point, as well as parallel movement along the object's surface. We show three main uses for this fingertip. Firstly, we demonstrate how the fingertips can be used for the detection of soft or lightweight objects by applying extremely small forces to them. Secondly, we present a method of full-perimeter definition (location and normal direction) of rigid objects by tracing. Lastly, we explain how our sensors can be used to detect stiffness and stiffness anomalies in soft objects, such as organic tissue.

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The Study of Sensor Structure to Sense a Surface Information for Intelligent Tactile Sensor
Kwonsik Shin, Minkyung Sim, Hyunchul Park, Yuljae Cho, Jung Inn Sohn, Seung Nam Cha, and Jae Eun Jang
Daegu Gyeongbuk Institute of Science and Technology, South Korea; University of Oxford, UK
A study of the human sense of touch has attracted much interest for a long time. Various kinds of sensors have been studied with various technologies for the sensing of external stimuli. Tactile sensors using capacitive, piezoresistive, piezoelectric and pyroelectric mechanism have been suggested to sense pressure, vibration and temperature. Unfortunately, it is rare to find a studying results of tactile sensor related with a surface information detection in comparison with pressure and temperature sensing. The ability to sense a surface information is the important factor to distinguish surface feelings such as roughness and smoothness. In this paper, a sensor array using piezoelectricity is demonstrated with a sliding motion to sense surface information such as the pitch and width of surface features. The suggested sensor array has a high spatial resolution(500um) and detected the variable sliding speeds thanks to the excellent dynamic response of the piezoelectric material. The reconfigured surface information had high accuracy compared to actual one. The demonstrated sliding speed sensing, high spatial resolution and the pitch and width of surface features measurement capabilities allow the sensor to be utilized as an intelligent artificial tactile sensor.

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Development of a Miniaturized Thermal Module Designed for Integration in a Wearable Haptic Device
Massimiliano Gabardi, Daniele Leonardis, Massimiliano Solazzi, and Antonio Frisoli
Scuola Superiore Sant'Anna, Italy
This work presents the development of a novel thermal display for transient heat rendering in virtual environments. The design of the fingertip device focused on the low weight and compactness in order to achieve a high level of wearability and high performance in thermal rendering. The device is intended for integration with the Haptic Thimble device, in order to develop a novel interface for thermal and haptic rendering of virtual surfaces. An iterative Finite Elements (FE) procedure has been performed within the design process in order to numerically validate the final design of the thermal module. Finally, a thorough experimental characterization has been performed in order to evaluate the dynamic thermal capabilities of the prototype, considering also the finger contact response and the temperature uniformity of the plate in contact with the finger.

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Harold's Purple Crayon Rendered in Haptics: Large-Stroke, Handheld Ballpoint Force Feedback
Soheil Kianzad and Karon E. MacLean
University of British Columbia, Canada
Inspired by needs for haptic support of large motions on a surface (in embodied conceptual learning, commercial design, and 2D virtual / augmented reality), we present the ballpoint drive. This novel approach circumvents conventional constraints by imposing a new one: motion restricted to rolling on an arbitrary two dimensional surface, and grounding forces generated through friction. We analyze the ballpoint's design considerations in the context of our framing applications, describe a first prototype and its performance, and assess its potential for further development.

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Oral Session 3: Perception and Action

Perceptual Dimensionality of Manual Key Clicks
Quan Liu, Hong Z. Tan, Liang Jiang, and Yulei Zhang
Purdue University, USA; AAC Technologies, China
The present study investigated the perceptual dimensions associated with manual key clicks, with the goal of developing realistic haptic key-click feedback signals for virtual keys. We first harvested eight adjective pairs for describing the haptic feel of button and key presses from native English speakers. We then conducted the main experiment where participants provided adjective ratings and grouping data for twenty-three buttons and keys. An MDS analysis of the grouping data led to either a 2-D or 3-D solution. By projecting adjective ratings onto the MDS solution spaces, we found the 2-D perceptual space to be an adequate representation of human perception of manual key clicks. The two perceptual dimensions are determined to be shallow-deep and rough-smooth. Future work will explore the physical parameters corresponding to the perceptual dimensions and ways to simulate realistic key clicks by designing feedback signals using the relevant parameters.

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Evaluation of a Digital Grand Piano for Vibrotactile Feedback Experiments and Impact of Finger Touch on Piano Key Vibrations
Matthias Flückiger, Tobias Grosshauser, and Gerhard Tröster
ETH Zurich, Switzerland
Pianists usually pay little attention to piano key vibrations but it was shown that they influence the perceived quality of an instrument and it was suggested that they might play a role for the precise timing and dynamic control in piano playing. To objectively measure and understand the influence of vibrotactile feedback in the pianist-piano interaction, we plan experiments with a digital hybrid grand piano - the Yamaha AvantGrand N3X - that simulates piano key vibrations with a rendering system. In this paper, we evaluate piano key vibrations of this instrument with a laser Doppler vibrometer and compare the vibrations to measurements with an acoustic grand piano. The peak levels of both instruments (13 to 35 um for the acoustic grand piano and 16 to 25 um for the AvantGrand) are comparable but the rendering system has limitations outside the frequency range from 150 to 400 Hz. Furthermore, the perceptibility of the vibrations at the left and right hand playing positions is investigated. Finally, the impact of the finger on the vibrations during different stages of a key press is analyzed and it is demonstrated that the finger influences the displacement levels and the spectral weighting of the piano key vibrations.

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Comparing Proprioceptive Acuity in the Arm between Joint Space and Task Space
Sean M. Sketch, Amy J. Bastian, and Allison M. Okamura
Stanford University, USA; Johns Hopkins School of Medicine, USA
Proprioception—the sense of one's body position and movement, without the aid of vision—plays a critical role in human motor control, allowing us to adeptly move our bodies through a high-dimensional task space. The relationship between joint space and task space with regard to proprioception has not been studied in the general population. This work begins to explore the relationship between proprioceptive acuity—the combination of accuracy and precision—in joint space and task space, focusing on the elbow, shoulder, and hand of the arm in single-joint (joint-space) and integrated multi-joint (task-space) active position-matching tests with a planar, robotic arm support. Our results reveal a strong correlation between joint-space proprioception at the shoulder and elbow and task-space proprioception at the hand. However, when joint-space proprioceptive error is propagated through a model of the arm's planar kinematics, it agrees poorly with the proprioceptive error measured explicitly in task space. Task-space proprioception exhibits greater accuracy than joint-space proprioception, as would be expected given the greater biological relevance of a planar reach compared to an isolated joint movement. Task-space and joint-space proprioception also differ in directional precision, exhibiting the greatest variance along nearly orthogonal axes, approximately aligned with the sagittal and frontal body planes. These findings have implications for the diagnosis of sensorimotor impairment and the development of movement therapies following neurological injury.

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Where Are My Fingers? Assessing Multi-Digit Proprioceptive Localization
Bharat Dandu, Irene A. Kuling, and Yon Visell
University of California at Santa Barbara, USA; VU University Amsterdam, Netherlands
The proprioceptive sense is an important component in the sensory system, providing position estimates for the parts of our body that are needed in order to guide behavior. While prior work has characterized proprioceptive localization of the upper limb as a whole, few studies have investigated the proprioceptive localization of individual digits, despite their central role in tactile exploration and fine manipulation. In this study, we asked subjects to report the perceived positions of the endpoints of each finger by means of a virtual reality and multi-finger tracking system, and we investigated the magnitude and variability of the proprioceptive localization errors that ensued. We found the errors to be large, averaging 4.3 cm per digit, even when the location of the wrist was disclosed to participants. This error magnitude is comparable to those that have been reported for whole limb localization, and represents a significant fraction of the length of an entire digit. Localization accuracy is greatest for the thumb and smallest for the little finger, reflecting in all cases, significant biases in perceived locations. The precision of localization was similar for each finger, with uncertainties on the order of several centimeters. The posture of the hand and specific location of the finger both affected errors. The specific error patterns for each subject were idiosyncratic, and the results suggest an underlying proprioceptive hand representation in which the fingers are distorted from the true shape of the hand. These results may have implications for understanding the role of position sensing in tactile exploration and fine manipulation, and suggest that an improved understanding of sensorimotor integration of proprioceptive information from the fingers is needed.

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The Effect of Dissociation between Proprioception and Vision on Perception and Grip Force Control in a Stiffness Judgment Task
Stephanie Hu, Raz Leib, and Ilana Nisky
Massachusetts Institute of Technology, USA; Ben-Gurion University of the Negev, Israel
Our sensorimotor system estimates stiffness to form stiffness perception, such as for choosing a ripe fruit, and to generate actions, such as to adjust grip force to avoid slippage of a scalpel during surgery. We examined how temporal manipulation of the haptic and visual feedback affect stiffness perception and grip force adjustment during a stiffness discrimination task. We used delayed force feedback and delayed visual feedback to break the natural relations between these modalities when participants tried to choose the harder spring between pairs of springs. We found that visual delay caused participants to slightly overestimate stiffness while force feedback delay caused a mixed effect on perception; for some it caused underestimation and for some overestimation of stiffness. Interestingly and in contrast to previous findings without vision, we found that participants increased the magnitude of their applied grip force for all conditions. We propose a model that suggests that this increase was a result of coupling the grip force adjustment to their proprioceptive hand position, which was the only modality which we could not delay. Our findings shed light on how the sensorimotor system combines information from different sensory modalities for perception and action. These results are important for the design of improved teleoperation systems that suffer from unavoidable delays.

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Too Hot, too Fast! Using the Thermal Grill Illusion to Explore Dynamic Thermal Perception
Shriniwas Patwardhan , Anzu Kawazoe, David Kerr, Masashi Nakatani, and Yon Visell
George Mason University, USA; University of California at Santa Barbara, USA; William Sansum Diabetes Center, USA; Keio University, Japan
Thermal perception is important in the experience of touching real objects, and thermal display devices are of growing interest for applications in virtual reality, medicine, and wearable technologies. In this paper, we designed a new thermal display, and investigated the perception of spatially varying thermal stimuli, including the thermal grill illusion. The latter is a perceptual effect in which a burning sensation is elicited in response to touching a surface composed of spatially juxtaposed warm and cool areas. Using a computer controlled thermal display, we present experiments in which we measured temporal correlates of the perception of spatially inhomogeneous stimuli, or thermal grills. We assessed the intensity of responses elicited by thermal grill stimuli with different temperature settings, and measured the response time until the onset of burning sensations. We found that thermal grills elicited highly stereotyped responses. The experimental results also indicated that as the temperature difference increases, the intensity increases monotonically, while the response time decreases monotonically. Consequently, perceived intensity was inversely correlated with response time. Under current physiological explanations, responses to thermal stimuli depend on tissue heating, neural processing, and the spatial distribution (or juxtaposition) of surface temperatures. The results of this study could help to inform models accounting for these factors, enabling new applications of the thermal grill illusion.

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Oral Session 4A: Electroadhesive Surfaces

On the Electrical Characterization of Electroadhesive Displays and the Prominent Interfacial Gap Impedance Associated with Sliding Fingertips
Craig D. Shultz, Michael A. Peshkin, and J. Edward Colgate
Northwestern University, USA
We report on the characterization of two variable friction electroadhesive displays using careful electrical and electrochemical impedance measurements. We qualitatively and quantitatively examine the properties of the skin, body, surface coating, and various electrode interface impedances in isolation using different contact interface conditions and measurement types. A lumped series impedance model explains how all impedances are related during normal usage, and the linearity of this model is shown to be valid under certain assumptions, such as high applied frequencies or small applied currents. Speculation as to the physical mechanisms underlying each impedance element is also given. This analysis unambiguously verifies the existence of a previously hypothesized key electrical system parameter: the sliding interfacial impedance (or air gap impedance). This parameter represents the large increase (100-1000 percent) in overall electrical impedance observed when a finger is sliding versus when it is stationary. It is concluded that this impedance increase cannot be explained by other measured electrical impedance elements in the system and that it vanishes again when the finger comes to rest.

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A Study of Tactile Sensation and Magnitude on Electrostatic Tactile Display
Hirobumi Tomita, Satoshi Saga, Hiroyuki Kajimoto, Simona Vasilache, and Shin Takahashi
University of Tsukuba, Japan; Kumamoto University, Japan; University of Electro-Communications, Japan
Touchscreen interfaces have become increasingly popular worldwide. However, few commercial touchscreens enable reactive tactile signals. We use lateral-force-based tactile feedback devices that employ electrostatic force. Our goal is to realize more realistic tactile sensation to the user. Previous researches evaluated by using multiple axes determined by the experimenter, however, intuitive classification of these sensation with onomatopoeic words has not been held. In this research, we focused on evaluating how the user feels about the electrostatic stimulation. Furthermore, we proposed a modeling of magnitude of tactile sensation, and discussed what kind of tactile sensation can be displayed with our system.

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Creating Multi-touch Haptic Feedback on an Electrostatic Tactile Display
Gholamreza Ilkhani and Evren Samur
Boğaziçi University, Turkey
Electrovibration is a promising method used to generate tactile feedback on touch screens. Although the method has recently received considerable attention from tactile display developers, almost all efforts so far have focused on single touch applications. However, extending this technology to apply to multi-touch systems is required to benefit from the rapidly growing touch screen industry. Through the course of this study, we propose a method and present a tactile display prototype that creates multi-touch tactile feedback using electrostatic attraction. The method relies on applying high-voltage AC signals on certain orthogonal electrode lines resulting in perceivable changes of friction at the intersection points. Generated surface friction on the prototype is measured using a planar tribometer. Results reveal that multiple localized friction spots can be generated with the proposed method. A user study is also carried out to test the prototype in a multi-touch scenario where two fingers explore a virtual texture simultaneously. Additionally, quantitative and qualitative analyses demonstrate the feasibility of creating multi-touch haptic feedback on an electrostatic tactile display.

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Data-Driven Rendering of Fabric Textures on Electrostatic Tactile Displays
Jian Jiao, Yuru Zhang, Dangxiao Wang, Yon Visell, Dekun Cao, Xingwei Guo, and Xiaoying Sun
Beihang University, China; University of California at Santa Barbara, USA; Jilin University, China
Due, in part, to the popularity of online shopping, there is considerable interest in enabling consumers to experience material touch via internet connected devices. While there have been several efforts to render texture via electrostatic tactile displays, the textures involved have typically consisted of synthetic patterns, such as shapes, shadings, or gradients of photographic textures. In this paper, we propose a data-driven algorithm for the haptic rendering of fabric textures on an electrostatic tactile display. We measure the friction force, normal force, and displacement during the swiping of a finger across real fabric using a new measurement apparatus introduced here. Using these measurements, we compute friction coefficients derived from the recorded frictional and normal forces. We then reproduce the friction coefficients by controlling the voltage applied to an electrostatic tactile display in order to render the tactile texture of the measured fabric. In order to evaluate this rendering method, we conducted a psychophysical experiment that assessed the visual and haptic similarity of ten real and simulated fabrics. The experimental results show that the virtual textures generated using this electrostatic rendering algorithm were perceptually similar to the corresponding real textures for all fabrics tested, underlining the promise of electrostatic tactile displays for material simulation.

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Oral Session 4B: Wearable Haptics

Feel-a-Bump: Haptic Feedback for Foot-Based Angular Menu Selection
Jan Anlauff, Taeyong Kim, and Jeremy R. Cooperstock
McGill University, Canada
Although diverse foot-based applications have been explored, foot-based menu selection is underexplored given its potential for low-fatigue secondary control input. Here, we are investigating whether the effect of adding haptic modalities can achieve higher performance in a menu selection task. We study the effect of auditory or vibrotactile feedback on selection performance in radial menus consisting of three, six and nine items. We compared no feedback to one auditory and two vibrotactile clicks, one across the foot, one localized to the movement direction. All feedback modalities allowed for rapid completion of menu selections and, while audio was generally preferred and our results suggest a superiority over haptics, the latter are still helpful in increasing selection accuracy. However, we argue that the difference is such that haptics could still be used with comparable performance in noisy environments or by users with auditory disabilities. Finally, we use an analysis of the number of attempts required to select the correct position, coupled with the number of errors, to make design recommendations for foot-based menus.

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Development of a Wearable Haptic Device That Presents Haptics Sensation of the Finger Pad to the Forearm
Taha K. Moriyama, Ayaka Nishi, Rei Sakuragi, Takuto Nakamura, and Hiroyuki Kajimoto
University of Electro-Communications, Japan
While many wearable tactile displays for the fingers, such as fingertip-type and glove-type displays, have been developed, their weight and size typically hinder the free movement of fingers, especially when considering the multi-finger scenario. We propose a method of presenting the haptics sensation of the fingertip on the forearm, not on the fingertip, to address this issue. A five-bar linkage mechanism was adopted to present a two-degree-of-freedom force. We conducted two experiments. In the first experiment, we presented a pressure sensation and a horizontal friction sensation perceived by the index finger to multiple sites of the forearm to search for a proper location of presentation, finding that the volar part of the wrist is optimal. On the basis of this result, we developed a device for the index finger and thumb, and conducted a second experiment to present the grasping force in a virtual reality environment. The realism of the experience in virtual reality was better when using the designed device than for no haptics cue or for vibration conditions.

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A Two-Fingered Force Feedback Glove using Soft Actuators
Yu Zhang, Dangxiao Wang, Ziqi Wang, Yueping Wang, Li Wen, and Yuru Zhang
Beihang University, China
Existing force feedback gloves mainly adopt rigid actuators such as electric motors and pneumatic cylinders, which have limitations including safety issues, heavyweight, and complex transmission mechanisms. In this paper, we introduce a light-weighted force-feedback glove using pneumatic-driven soft actuators. Based on the unilateral deformable features of the strain-limiting layer in the soft actuator, the dorsal-side mounting solution along with a light-weighted linkage mechanism is proposed to produce fingertip force feedback. We applied a pre-deformation of the soft actuator to enable the back drivability and the free space sensation. We then implemented a physical prototype of a two-fingered glove. Experimental results show that the glove could achieve considerable performance in free space with small frictional force (0.58N in maximum). While simulating the constrained space, the fingertip force reaches up to 2.1N. For the future work, we plan to improve the current solution to five fingers with finger position tracking and distributed tactile sensing on the palm.

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The Rice Haptic Rocker: Altering the Perception of Skin Stretch through Mapping and Geometric Design
Janelle P. Clark, Sung Y. Kim, and Marcia K. O'Malley
Rice University, USA
Skin stretch haptic devices are well-suited for transmitting information through touch, a promising avenue in prosthetic research, addressing the lack of feedback in myoelectric designs. Rocker-based skin stretch devices have been proposed for sensory substitution and navigational feedback, but the designs vary in their geometry. Other works create torsional stretch, and utilize nonlinear mappings to enhance perception. This work investigates parameters of rocker geometry and mapping functions, and how they impact user perception. We hypothesize that perceptual changes are dependent on the choice of stretch increment sizes over the range of motion. The rocker geometry is varied with an offset between the rotational and geometric axes, and three rocker designs are evaluated during a targeting task implemented with a nonlinear or linear mapping. The rockers with no offset and a positive offset (wide) perform better than the negative offset (narrow) case, though the mapping method does not affect target accuracy.

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Oral Session 5A: Ultrasonic Surfaces

UltraShiver: Lateral Force Feedback on a Bare Fingertip via Ultrasonic Oscillation and Electroadhesion
Heng Xu, Michael A. Peshkin, and J. Edward Colgate
Northwestern University, USA
We propose a new lateral force feedback device, the UltraShiver, which employs a combination of in-plane ultrasonic oscillation (around 30 kHz) and out-of-plane electroadhesion. It can achieve a strong active lateral force (400 mN) on the bare fingertip while operating silently. The lateral force is a function of pressing force, lateral vibration velocity, and electroadhesive voltage, as well as the relative phase between the velocity and voltage. In this paper, we perform experiments to investigate characteristics of the UltraShiver and their influence on lateral force.

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Determining the Haptic Feedback Position for Optimizing the Targeting Performance on Ultrasonic Tactile Displays
Farzan Kalantari, Edward Lank, Yosra Rekik, Laurent Grisoni, and Frédéric Giraud
University of Lille, France; CNRS, France; Inria, France; University of Waterloo, Canada
Alongside questions of how to create haptic effects on displays via alternative hardware, recent work has explored rendering options with respect to haptic effects, i.e. when and where to provide haptic feedback. In particular, recent work by Zhang and Harrison for electrostatic haptic feedback noted that the optimal technique for haptic feedback during interaction is the Fill technique, where haptic effects are rendered at all times when a user's finger is within the bounds of the target. In this paper, we explore whether this result generalizes to an alternative haptic rendering technology that uses ultrasonic vibrations to create haptic sensations, a technique called the ``Squeeze Film Effect''. In contrast to prior work, our results indicate that positioning the haptic feedback as a discrete linear stimulus centred on the target provides an optimal trade-off between speed, accuracy, and user preference. We highlight the implications of this work to the generalizability of haptic feedback: Haptic feedback can improve time, errors, and user satisfaction during interaction, but only if the correct form of feedback is used for the specific haptic effect generated by the hardware.

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Evaluation of a Friction Reduction Based Haptic Surface at High Frequency
Frédéric Giraud, Tomohiro Hara, Christophe Giraud-Audine, Michel Amberg, Betty Lemaire-Semail, and Masaya Takasaki
University of Lille, France; University of Saitama, Japan
The influence of the vibration frequency on the friction reduction of an ultrasonic haptic surface has been reported in the literature. The models predict that increasing the frequency of the vibration leads to higher friction reduction at constant vibration amplitude, but this has not been reported experimentally. In this paper, we study the friction reduction on a prototype which can vibrate at low (66kHz) and high (225kHz) frequency. By estimating the Point of Subjective Equivalence between a standard at low frequency with a sample at high frequency, we have found that high frequencies can indeed reduce the friction, with the advantage of much smaller vibration amplitude. Moreover, we show that the invariant between the two frequency conditions is not the vibration amplitude. Our conclusion is that the invariant could be the acceleration instead.

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Differentiated Haptic Stimulation by Modal Synthesis of Vibration Field
Ehsan Enferad, Christophe Giraud-Audine, Frédéric Giraud, Michel Amberg, and Betty Lemaire-Semail
University of Lille, France
To date, Several focusing techniques have been proposed to realize localized stimulation on haptic interfaces: phased arrays of actuators with delayed excitation, or time reversal techniques which require a preliminary learning phase. Additionally, these techniques are sensitive to parameters variation and disturbances. Modal decomposition allows to realize arbitrary vibration fields congruent with the boundary conditions and in this paper, Modal decomposition is proposed to realize a desired vibration velocity field in order to have differentiated stimuli. The experimental results validate the ability of the method to approximate satisfactorily a desired reference form. The psychophysical evaluations show that users can differentiate and localize the stimulation while exploring a surface with two fingers.

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Oral Session 5B: Medicine and Neuroscience

An Investigation of Haptic Perception of Viscoelastic Materials in the Frequency Domain
Ozan Caldiran, Hong Z. Tan, and Cagatay Basdogan
Koç University, Turkey; Purdue University, USA
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 degree) than those of the upper bound to 90 degrees.

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EEG Correlates of Motor Control Difficulty in Physical Human-Robot Interaction: A Frequency Domain Analysis
Amirhossein H. Memar and Ehsan T. Esfahani
SUNY Buffalo, USA
This study investigates the relationship between electroencephalogram (EEG) activity and motor control difficulty during physical interaction with an admittance controlled robot. Subjects performed a fine cooperative manipulation task, in which the motor control difficulty was manipulated by altering admittance dynamics. To quantify motor control difficulty, an interaction instability index is proposed based on the spectral information of interaction forces. Regression analysis is then performed to construct a model to estimate motor control difficulty from EEG spectral features. The results indicate the reliability of EEG signals as an indicator of motor control difficulty in pHRI.

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Haptic Stroke Testbed for Pharmacological Evaluation of Dynamic Allodynia in Mouse Models
Jin Lee, Brian J. Atwood, Salim Megat, Gregory Dussor, Theodore J. Price, and Ann Majewicz Fey
University of Texas at Dallas, USA
Dynamic mechanical allodynia is an aggravating neuropathological condition in which light, physical touch leads to pain. Developing pharmaceutical agents to treat this condition requires extensive animal trials using a mouse model, and a laborious process of manually stroking inflicted mouse paws, with a brush or cotton swab, while recording responses to that stimulus. In this paper, we developed an autonomous testing mechanism to create repeatable stroking sensations for mice during dynamic allodynia testing. The chamber consists of a belt driven brush mechanism and light and dark cham- bers. Additionally, we conducted a human subjects study to determine the baseline variability in human-performed dynamic allodynia testing. Our tactile stoke display is capable of stroking a mouse paw between 1-5 mm/s with a repeatable force. In our human subject experiments, the user applied force ranged from 0.1-9.0 gF with a maximum standard deviation of 4.13 gF. In contrast, our device is capable of producing repeatable brush strokes at 0.69 gF (SD = 0.13 gF) and 1.78 gF (SD = 0.16 gF) for two brushes. Preliminary animal studies show that normal mice are not disturbed by the stroking sensation; however, mice afflicted with allodynia move away from it. On average the injured mice spent 90% of their time in a bright, adverse environment to avoid the brush, whereas normal mice only spent 40% of their time in the bright environment.

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Toward Improved Surgical Training: Delivering Smoothness Feedback using Haptic Cues
William H. Jantscher, Shivam Pandey, Priyanshu Agarwal, Sadie H. Richardson, Bowie R. Lin, Michael D. Byrne, and Marcia K. O'Malley
Rice University, USA
Abstract—Surgery is a challenging domain for motor skill acquisition, and compounding this difficulty is the often delayed and qualitative nature of feedback that is provided to trainees. In this paper, we explore the effectiveness of providing real-time feedback of movement smoothness, a characteristic associated with skilled and coordinated movement, via a vibrotactile cue. Subjects performed a mirror-tracing task that requires coordination and dexterity similar in nature to that required in endovascular surgery. Movement smoothness, measured by spectral arc length, a frequency-domain measure of movement smoothness, was encoded in a vibrotactile cue. Performance of the mirror tracing task with smoothness-based feedback was compared to position-based feedback (where the subject was alerted when they moved outside the path boundary) and to a no-feedback control condition. Although results of this pilot study failed to indicate a statistically significant effect of smoothness-based feedback on performance, subjects receiving smoothness-based feedback altered their task completion strategies to improve speed and accuracy, while those receiving position-based feedback or no feedback only improved in terms of increased accuracy. In tasks such as surgery where both speed and accuracy are vital to positive patient outcomes, the provision of smoothness-based feedback to the surgeon has the potential to positively influence performance.

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Oral Session 6: Modeling and Rendering

Toward High-Fidelity Haptic Interaction with Virtual Materials: A Robotic Material Scanning, Modelling, and Display System
Matti Strese and Eckehard Steinbach
TU Munich, Germany
We present a robotic setup for the acquisition of object surface material properties. Our setup is able to collect selected kinesthetic characteristics, such as the surface structure and weight, as well as tactile properties like the friction coefficient and the fine roughness characteristics of the object surface. Additionally, the setup captures the visual appearances of the object. The recorded multimodal sensor data provide all relevant information required to form a haptic model of a material sample. We then use this representation in a standard haptic rendering framework and display the virtual materials using an augmented Phantom Omni device. We conducted a subjective experiment which shows that its participants perceived and rated the rendered virtual materials as similar to the corresponding real materials in a direct comparison test where the users interact simultaneously with the real and the virtual material samples. An overall user rating of 4.3 out of 5.0 is achieved during the subjective experiment.

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A Partial Contact Frictional Force Model for Finger-Surface Interactions
Marco Janko, Zhengqiao Zhao, Moshe Kam, and Yon Visell
Drexel University, USA; New Jersey Institute of Technology, USA; University of California at Santa Barbara, USA
Touching an object with our fingers yields frictional forces that allow us to perceive and explore its texture, shape, and other features. While the relevance of these frictional forces to sensory and motor function in the hand is well established, the way that they reflect the shape and texture of touched objects is not well understood. This lack of knowledge currently constraints the development of haptic rendering algorithms that rely on reproducing frictional forces to mimic the sensation of touching real surfaces. To address this, we created a low order contact mechanics inspired model that accounted for: disconnection between the finger and high relief features of the surfaces, and differences of pressure applied in the contact regions. The output of our model was compared to experimental frictional force measurements of bare-fingers sliding on structured surfaces. The results show high similarity between the measurements and the model output. The model presented can be used to predict frictional forces if the geometry of a touched surface is known together with the coefficient of friction of the untextured surface.

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Geometry-Based Haptic Texture Modeling and Rendering using Photometric Stereo
Sunghwan Shin and Seungmoon Choi
POSTECH, South Korea
This paper presents an improved approach to geometry-based haptic texture modeling and rendering. We adopt photometric stereo, one of the most accurate algorithms for 3D surface reconstruction, to increase the resolution of captured geometry profiles. This benefit of higher texture resolution can enhance the realism of rendered textures in terms of roughness. To this end, we have designed and constructed a dome-shaped lighting structure for use in the modeling using photometric stereo. With this apparatus and the photometric stereo algorithms, we can achieve very high texture modeling resolution in the order of 10 mm. We also identify the stiffness and friction of real materials using the Hunt-Crossley model and the Dahl model, respectively, for realistic texture rendering. A user study measuring the perceived similarity between real and virtual textures demonstrated that our system can achieve a reasonably high level of realism in rendering textured objects with high compliance or low friction.

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An Inverse Neural Network Model for Data-Driven Texture Rendering on Electrovibration Display
Reza Haghighi Osgouei, Sunghwan Shin, Jin Ryong Kim, and Seungmoon Choi
POSTECH, South Korea; Electronics and Telecommunications Research Institute, South Korea
With the introduction of variable friction displays, new possibilities have emerged in haptic texture rendering on flat surfaces. In this work, we propose a data-driven method for realistic texture rendering on an electrovibration display. We first describe a motorized linear tribometer we developed to collect lateral frictional forces from the textured surfaces under various scanning velocities and normal forces. We then propose an inverse dynamics model of the display to describe its output input relationship using nonlinear autoregressive with external input (NARX) neural networks. Forces resulting from applying a pseudo-random binary signal (PRBS) to the display are used to train each network under the given experimental condition. A comparison between the real and virtual forces in frequency domain shows promising results for recreating virtual textures similar to the real ones and also reveals the capabilities and limitations of the proposed method.

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Enhancing the Pseudo-Haptic Effect on the Touch Panel using the Virtual String
Yuki Ban and Yusuke Ujitoko
University of Tokyo, Japan; Hitachi, Japan
This paper proposes a novel method of enhancing the pseudo-haptic effect on the touch panel. In prior studies to invoke pseudo-haptics on the touch panel, there has been a problem stemming from the difference in position between the finger and the object. We added the virtual string on display which shows a connection between the finger and the object. The user studies showed that the presence of the virtual string was effective to invoke pseudo-haptics, and the setting of string breaks was key to enhance the effect of it.

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Oral Session 7A: Tactile Perception

Haptic Display of Melodic Intervals for Musical Applications
Deborah C. Egloff, Marcelo M. Wanderley, and Ilja Frissen
McGill University, Canada
The focus of this study was to investigate the ability to discriminate between melodic intervals of the equal tempered scale based solely on vibrotactile stimulation. In music, a melodic interval is the musical distance between two pitches, or notes, that are played sequentially. This paper tests the hypothesis that people can detect melodic intervals that are presented to different body sites such as the fingertip of the index finger of the non-dominant hand, as well as to the flank, the lateral region between the ribcage and the hip bone. Vibrotactile stimuli on the flank were displayed through voice coils of different diameters (∅ 13 mm and ∅ 25 mm respectively), while those at the finger were displayed with a ∅ 13 mm diameter voice coil. Six melodic intervals ranging from a minor second (∆f=100 cents) to a perfect fifth (∆f=700 cents) were compared to the reference interval of a perfect prime (∆f=0 cents) at a fundamental frequency (f0) of 65 Hz. Discrimination was significant for intervals as small as a major second (∆f=200 cents; i.e. 8Hz, or 12.3%), depending on the location of the body. Overall, results tend to suggest that larger intervals are less difficult to detect than smaller intervals.

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Single Pitch Perception of Multi-frequency Textures
Rebecca Fenton Friesen, Roberta L. Klatzky, Michael A. Peshkin, and J. Edward Colgate
Northwestern University, USA; Carnegie Mellon University, USA
This study explores people's ability to distinguish spatial complexity in tactile textures, with the eventual goal of reducing the necessary complexity of texture representation for surface display devices. To this end, we tested subjects' ability to perceptually match a reference texture containing two spatial frequency components by adjusting the frequency and amplitude of a single frequency. All textures consisted of spatially varied friction levels on a glass display screen, where friction was modulated via amplitude of ultrasonic vibrations. Resulting chosen single frequencies were systematic, and suggest subjects can identify a single frequency, or tactile pitch, falling somewhere between those of the reference texture. Subject-adjusted frequency is modeled as a function of the reference texture's frequency components and the ratio of their amplitudes.

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Tactile Spatial Acuity of the Neck using a Two-Point Orientation Discrimination Task
Kelly A. Morrow and Mounia Ziat
Northern Michigan University, USA; University of Maryland at College Park, USA
How sensitive is the neck in distinguishing two points of contact? The current study was performed to gain insight about the spatial acuity of the neck in hopes of using this information in future research and development of tactile devices targeting this area of the body. Using a two-point orientation discrimination task, a relatively novel measure of spatial sensitivity, the threshold of eight locations around the circumference of the neck was measured. Results showed uniform sensitivity in seven of the eight locations, with a slightly lower threshold at the very front of the neck. These results indicate that the neck could be a viable location to effectively communicate tactile information in a uniform fashion.

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Tactile Distances Are Greatly Underestimated in Perception and Motor Reproduction
Jasper M. van de Lagemaat, Irene A. Kuling, and Yon Visell
VU University Amsterdam, Netherlands; University of California at Santa Barbara, USA
Tactile distance perception typically requires the integration of tactile speed over time. In this study, we investigated tactile distance perception by comparing subjects’ ability to reproduce tactile distance by moving the hand, and compared this to their ability to estimate the magnitude of sliding distance. This is the first investigation of subjects’ ability to use motor reproduction to reproduce the same tactile distance that was felt during passive sliding contact. To clarify the role of vibrotactile information in sliding distance perception, we investigated tactile distance perception by manipulating tactile mechanical signals in two different ways: by adding mechanical noise to the finger, or by sensing and amplifying vibrotactile signals in the finger. In our experiment, subjects systematically underestimated tactile sliding distance. On average, they reproduced 55% of the actual distance. Responses on the magnitude estimation and the distance reproduction tasks were highly similar. Subjects estimated sliding distance to be significantly longer when tactile signals were manipulated compared to no vibrotactile manipulations, although mechanical noise impaired distance perception accuracy. These results suggest that further research is needed in order to clarify the effect of underestimation of tactile distance on fine motor tasks guided by touch.

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Perceptual Dimensions of Vibrotactile Actuators
Lynette A. Jones and Anshul Singhal
Massachusetts Institute of Technology, USA
The objective of the present research was to determine how variations in the signals generated by different vibrotactile actuators are perceived and which features are judged as being distinctive. For this purpose, three different types of actuator were used to generate signals that varied in amplitude, waveform and frequency. Participants were required to judge the degree of similarity-dissimilarity between pairs of stimuli. Multi-dimensional scaling (MDS) techniques were then used as an exploratory data analysis technique to create a spatial map that depicted the relations among the various vibrotactile signals. The first dimension that emerged from the MDS represented a continuum associated with transitions in the amplitudes of the signals, with a smooth sine wave pattern contrasting with the more abrupt transitions in square waves. This may be considered a smooth-rough dimension. The second dimension extracted from the data was more difficult to characterize in that each of the two clusters along this dimension involved signals of varying waveform and frequency. Further work will aim at defining the perceptual qualities of this dimension.

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Six Principal Modes of Vibrotactile Display via Stylus
Ruisi Zhang, Andrew J. Boyles, and Jake J. Abbott
University of Utah, USA
We characterize the detection thresholds of subjects holding a stylus with a precision grasp for six principal modes of vibrotactile display: three orthogonal force directions and three orthogonal torque directions. Subjects are far more sensitive to torque signals about the shaft of the stylus than to torque signals orthogonal to it, subjects are less sensitive at low frequencies to force signals parallel to the shaft than to force signals orthogonal to it, and the thresholds for force and torque signals applied orthogonal to the shaft can be approximately equated by considering the reaction moment felt at the grasp point.

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Oral Session 7B: Designing Interactions

Electrostatic Adhesive Brakes for High Spatial Resolution Refreshable 2.5D Tactile Shape Displays
Kai Zhang and Sean Follmer
Stanford University, USA
We investigate the mechanism, design, modeling and fabrication of a scalable high resolution, low cost and lightweight refreshable 2.5D tactile pin array controlled by electrostatic adhesive brakes. By replacing linear actuators in motorized shape displays with a high voltage solid-state circuit that can be fabricated with printable electronics techniques, we can decrease the cost and complexity of such devices. Electrostatic adhesive brakes, made by patterning interdigital electrodes on high dielectric constant thin films, are used to hold metal pins' positions and provide contact force to the user's fingertip. We present designs of two high resolution brake modules which are 1.7 mm pitch with 0.8 mm width pins and 4 mm pitch with 1.58 mm width pins with a maximum measured dynamic loading force of 76.3 gf and static loading force of 28 gf on an individual pin (for the later size). A small demonstration of 4 x 2 pin array with a 4 mm pitch size within a row and 2.5 mm pitch size between the rows, using 1.58 mm width pins, was created. We also characterized the refresh time to be 37.5 ms for each brake, which enables refreshable actuated pin displays.

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Exploration of Geometry and Forces Occurring within Human-to-Robot Handovers
Matthew K. X. J. Pan, Elizabeth A. Croft, and Günter Niemeyer
University of British Columbia, Canada; Monash University, Australia; Disney Research, USA
This work presents an exploratory user study of human-to-robot handovers. In particular, it examines how changes in a robot behaviour influence human participation and the overall interaction. With a 2x2x2 experimental design, we vary three basic factors and observe both the interaction position and forces. We find the robot's initial pose can inform the giver about the upcoming handover geometry and impact fluency and efficiency. Also we find variations in grasp method and retraction speed induce significantly different interaction forces. This effect may occur by changing the giver's perception of object safety and hence their release timing. Alternatively, it may stem from unnatural or mismatched robot movements. We determine that making the robot predictable is important: we observe a learning effect with forces declining over repeated trials. Simultaneously, the participants' self-reported discomfort with the robot decreases and perception of emotional warmth increases. Thus, we posit users are learning to predict the robot, becoming more familiar with its behaviours, and perhaps becoming more trusting of the robot's ability to safely receive the object. We find these results exciting as we believe a robot can become a trusted partner in collaborative tasks.

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HapticDrone: An Encountered-Type Kinesthetic Haptic Interface with Controllable Force Feedback: Example of Stiffness and Weight Rendering
Muhammad Abdullah, Minji Kim, Waseem Hassan, Yoshihiro Kuroda, and Seokhee Jeon
Kyung Hee University, South Korea; Osaka University, Japan
HapticDrone is our new approach to transform a drone into a force-reflecting haptic interface. While our earlier work proved the concept, this paper concretizes it by implementing accurate force control along with effective encountered-type stiffness and weight rendering for 1D interaction as a first step. To this end, generated force is identified with respect to drone's thrust command, allowing a precise control of force. Force control is combined with tracking of drone and hand, turning the HapticDrone into an ideal end-effector for the encountered-type haptics and making the system ready for more sophisticated physics simulation. Stiffness and weight of a virtual object is our first target of the simulation. Conventional stiffness and gravity simulation is merged into the encountered-type position control scheme, allowing a user to feel the softness and weight of an object. We further confirmed the feasibility by proving that the system fulfills the physical performance requirements commonly needed for an encountered-type haptic interface, i.e., force rendering bandwidth, accuracy, and tracking performance.

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Remotely Displaying Cooling Sensation via Ultrasound-Driven Air Flow
Mitsuru Nakajima, Keisuke Hasegawa, Yasutoshi Makino, and Hiroyuki Shinoda
University of Tokyo, Japan
A midair haptic display that provides a cooling sensation is developed in this study. Although a noncontact heat display using infrared rays has been reported, such an infrared display cannot cool the skin surface. In this study, we generate and control a straight, thin, long, air flow driven by an ultrasound-phased array and transport cold air to a localized spot on the users’ skin. Since the air flow position and direction is electronically steerable, the display area can be controlled freely. A prototype of the proposed display was developed and the cooling performance was evaluated. We confirm that a small cool spot is created and shifted on a user’s forearm based on our observations of the temporal changes in the skin temperature distribution using thermography.

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Data-Driven Thermal Rendering: An Initial Study
Hyejin Choi, Seongwon Cho, Sunghwan Shin, Hojin Lee, and Seungmoon Choi
POSTECH, South Korea
This paper presents a data-driven thermal rendering framework for highly realistic re-creation of the thermal dynamics of real objects in a virtual environment. We begin with a physics-based model for thermal rendering and then extend it to compute the desired temperature of a thermal display without identification of the thermal parameters of real objects. Our approach is data-driven: we collect the thermal responses between hand and object for many different combinations of the initial temperatures of hand and object and then interpolate several real thermal responses to render virtual thermal stimuli with the target initial temperatures. We also present perceptual evaluation results obtained in a discrimination experiment and a (preliminary) identification experiment, which both advocated the adequacy of our data-driven thermal rendering framework.

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Cable Driven Haptic Interface for Co-localized Desktop VR
Justine Saint-Aubert, Stéphane Régnier, and Sinan Haliyo
Sorbonne University, France
Cable haptic devices can produce a large set of forces while being inconspicuous. This paper outlines the design and the implementation of such a device as a desktop virtual environment. It's combined to a stereoscopic 3D display, visualized through a semi-mirror, below which the manipulation space is located. This configuration co-localizes, i.e superimposes, visual and haptic feedbacks for realistic user interaction. The constraint imposed by the reflective surface requires a specific configuration of the cable device. The process to design such a desktop sized virtual reality interface is explicitly exposed here. An over-constraint cable mechanism is proposed. The assembly of the complete co-localized visio-haptic interface is described, as well as a force computation method easy to implement.

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