IEEE Transactions on Haptics Posters
16:30 – 18:00, Colonial Ballroom
The Application of Tactile, Audible, and Ultrasonic Forces to Human Fingertips using Broadband Electroadhesion
(Northwestern University, USA)
We report an electroadhesive approach to controlling friction forces on sliding fingertips which is capable of producing vibrations across an exceedingly broad range of tactile, audible, and ultrasonic frequencies. Vibrations on the skin can be felt directly, and vibrations in the air can be heard emanating from the finger. Additionally, we report evidence from an investigation of the electrical dynamics of the system suggesting that an air gap at the skin/surface interface is primarily responsible for the induced electrostatic attraction underlying the electroadhesion effect. We developed an experimental apparatus capable of recording friction forces up to a frequency of 6 kHz, and used it to characterize two different electroadhesive systems, both of which exhibit flat force magnitude responses throughout the measurement range. These systems use custom electrical hardware to modulate a high frequency current and apply surprisingly low distortion, broadband forces to the skin. Recordings of skin vibrations with a laser Doppler vibrometer demonstrate the tactile capabilities of the system, while recordings of vibrations in the air with a MEMS microphone quantify the audible response and reveal the existence of ultrasonic forces applied to the skin via electronic friction modulation. Implications for surface haptic and audio-haptic displays are briefly discussed.
ToH Poster A1
eShiver: Lateral Force Feedback on Fingertips through Oscillatory Motion of an Electroadhesive Surface
(Northwestern University, USA)
We describe a new haptic force feedback device capable of creating lateral shear force on a bare fingertip—the eShiver. The eShiver creates a net lateral force from in-plane oscillatory motion of a surface synchronized with a “friction switch” based on Johnsen-Rahbek electroadhesion. Using an artificial finger, a maximum net lateral force of ± 300 mN is achieved at 55 Hz lateral oscillation frequency, and net force is shown to be a function of velocity and applied voltage, as well as the phase between them. A second set of experiments is carried out on a human finger, and a lateral force of up to ± 450 mN is achieved at a lateral oscillation frequency of 1,000 Hz. This force is reached at a peak lateral surface velocity of 400 mm/s and a peak applied voltage of 400 V. We develop a simple lumped parameter model of the eShiver, and a time domain simulation of the artificial finger is shown to agree with the experimental results. Three distinct zones of operation are found, which predict the limitations of force generation and which may be used for optimization. The human finger is found to be similar to the artificial finger in its dependence on actuation parameters, suggesting that the same lumped parameter model may be applied, albeit with different parameters. Curiously, the friction force due to Johnsen-Rahbek electroadhesion is found to increase substantially over time as the finger remains in contact with the surface. Considerations for optimizing the performance of the eShiver are discussed.
ToH Poster A2
Towards Universal Haptic Library: Library-Based Haptic Texture Assignment using Image Texture and Perceptual Space
(Kyung Hee University, South Korea; KOREATECH, South Korea)
In this paper we focused on the building a universal haptic texture models library and automatic assignment of haptic texture models to any given surface from the library based on image features. It is shown that a relationship exists between perceived haptic texture and its image features, and this relationship is effectively used for automatic haptic texture model assignment. An image feature space and a perceptual haptic texture space are defined, and the correlation between the two spaces is found. A universal haptic library was built, using 84 real life textured surfaces, by training a multi-class support vector machine with radial basis function kernel. The perceptual space was classified into perceptually similar clusters using K-means. Haptic texture models were assigned to new surfaces in a two step process; classification into a perceptually similar group using the trained multi-class support vector machine, and finding a unique match from within the group using binarized statistical image features. The system was evaluated using 21 new real life texture surfaces and an accuracy of 71.4 % was achieved in assigning haptic models to these surfaces.
ToH Poster A3
Evaluation of Piano Key Vibrations among Different Acoustic Pianos and Relevance to Vibration Sensation
Matthias Flückiger, Tobias Grosshauser, and Gerhard Tröster
(Electronics Laboratory, Switzerland; ETH Zurich, Switzerland)
Recent studies suggest that vibration of piano keys affect the perceived quality of the instrument, as well as the dynamic control and timing in piano playing. However, the time signals of piano key vibrations and its physical properties have not been analyzed and compared to the threshold of vibration sensation in a real-life playing situation yet. This study investigates piano key vibrations and explores the diversity of vibrations among different pianos with a laser Doppler vibrometer. A pianist was performing single keystrokes, note sequences, and a music piece excerpt on four concert grand pianos, five grand pianos, and two upright pianos. The measurements showed peak displacement levels up to 80 um and the frequency spectrum of the vibrations is dominated by frequencies lower than 500 Hz. Finally, a frequency weighting filter is introduced to show that vibration displacement time signals exceed the threshold of human vibration sensation for all evaluated instruments, when a note sequence is played in the bass to mid range with a single hand at forte level. The conducted experiments demonstrate that the vibration characteristics vary distinctively among the investigated pianos.
ToH Poster A4
Analog Haptic Control: Advantages and Challenges
Ryan Schindeler and Keyvan Hashtrudi-Zaad
(Queen's University, Canada)
Haptic simulation systems, which typically implement virtual environments in the discrete-time domain, present an inherent trade-off between stability, sampling frequency and the range of implementable environment dynamics. Previous research has demonstrated the potential of analog feedback for expanding the range of environment dynamics that result in a stable haptic interaction. In this paper, the effect of various system parameters on the environment dynamic range is analytically and experimentally investigated in the sense of uncoupled stability. In addition, Multilayer Decomposition, which enables a simple analog PD controller to implement nonhomogeneous or multilayer virtual environment dynamics, will be presented and evaluated.
ToH Poster A5
Evaluating Approaches to Rendering Braille Text on a High-Density Pin Display
Valerie Morash, Alexander Russomanno, R. Brent Gillespie, and Sile O'Modhrain
(Smith-Kettlewell Eye Research Institute, USA; University of Michigan, USA)
Refreshable displays for tactile graphics are typically composed of pins that have smaller diameters and spacing than standard braille dots. We investigated configurations of high-density pins to form braille text on such displays using non-refreshable stimuli produced with a 3D printer. Normal dot braille (diameter 1.5 mm) was compared to high-density dot braille (diameter 0.75 mm) wherein each normal dot was rendered by high-density simulated pins alone or in a cluster of pins configured in a diamond, X, or square; and to blobs that could result from covering normal braille and high-density multi-pin configurations with a thin membrane. Twelve blind participants read MNREAD sentences displayed in these conditions. For high-density simulated pins, single pins were as quickly and easily read as normal braille, but diamond, X, and square multi-pin configurations were slower and/or harder to read than normal braille. We therefore conclude that as long as center-to-center dot spacing and dot placement is maintained, the dot diameter may be open to variability for rendering braille on a high density tactile display.
ToH Poster B1
A Three Revolute-Revolute-Spherical Wearable Fingertip Cutaneous Device for Stiffness Rendering
(Aarhus University, Denmark; CNRS, France; University of Siena, Italy)
We present a novel 3RRS wearable fingertip device for the rendering of stiffness. It is composed of a static upper body and a mobile end-effector. The upper body is located on the nail side of the finger, supporting three servo motors, and the mobile end-effector is in contact with the finger pulp. The two parts are connected by three articulated legs, actuated by the motors. The end-effector can move toward the user's fingertip and rotate it to simulate contacts with arbitrarily-oriented surfaces. Moreover, a vibrotactile motor placed below the end-effector conveys vibrations to the fingertip. The proposed device weights 25 g for 35×50×48 mm dimensions. To test the effectiveness of our wearable haptic device and its level of wearability, we carried out two experiments. The first experiment tested the capability of our device in differentiating stiffness information, while the second one focused on evaluating its applicability in an immersive virtual reality scenario. Results showed the effectiveness of the proposed wearable solution, with a JND for stiffness of 208.5 ± 17.2 N/m. Moreover, all subjects preferred the virtual interaction experience when provided with wearable cutaneous feedback, even if results also showed that subjects found our device still a bit difficult to use.
ToH Poster B2
Evaluation of Wearable Haptic Systems for the Fingers in Augmented Reality Applications
(Sapienza University of Rome, Italy; CNRS, France; Aarhus University, Denmark; IIT, Italy; University of Siena, Italy)
Although Augmented Reality (AR) has been around for almost five decades, only recently we have witnessed AR systems and applications entering in our everyday life. Representative examples of this technological revolution are the smartphone games “Pokémon GO” and “Ingress” or the Google Translate real-time sign interpretation app. Even if AR applications are already quite compelling and widespread, users are still not able to physically interact with the computer-generated reality. In this respect, wearable haptics can provide the compelling illusion of touching the superimposed virtual objects without constraining the motion or the workspace of the user. In this paper, we present the experimental evaluation of two wearable haptic interfaces for the fingers in three AR scenarios, enrolling 38 participants. In the first experiment, subjects were requested to write on a virtual board using a real chalk. The haptic devices provided the interaction forces between the chalk and the board. In the second experiment, subjects were asked to pick and place virtual and real objects. The haptic devices provided the interaction forces due to the weight of the virtual objects. In the third experiment, subjects were asked to balance a virtual sphere on a real cardboard. The haptic devices provided the interaction forces due to the weight of the virtual sphere rolling on the cardboard. Providing haptic feedback through the considered wearable device significantly improved the performance of all the considered tasks. Moreover, subjects significantly preferred conditions providing wearable haptic feedback.
ToH Poster B3
Optimization-Based Wearable Tactile Rendering
(Universidad Rey Juan Carlos, Spain; University of Siena, Italy)
Novel wearable tactile interfaces offer the possibility to simulate tactile interactions with virtual environments directly on our skin. But, unlike kinesthetic interfaces, for which haptic rendering is a well explored problem, they pose new questions about the formulation of the rendering problem. In this work, we propose a formulation of tactile rendering as an optimization problem, which is general for a large family of tactile interfaces. Based on an accurate simulation of contact between a finger model and the virtual environment, we pose tactile rendering as the optimization of the device configuration, such that the contact surface between the device and the actual finger matches as close as possible the contact surface in the virtual environment. We describe the optimization formulation in general terms, and we also demonstrate its implementation on a thimble-like wearable device. We validate the tactile rendering formulation by analyzing its force error, and we show that it outperforms other approaches.
ToH Poster B4
Functional Contour-Following via Haptic Perception and Reinforcement Learning
Randall Hellman, Cem Tekin, Mihaela van der Schaar, and Veronica Santos
(University of California at Los Angeles, USA; Bilkent University, Turkey)
Many tasks involve the fine manipulation of objects despite limited visual feedback. In such scenarios, tactile and proprioceptive feedback can be leveraged for task completion. We present an approach for real-time haptic perception and decision-making for a haptics-driven, functional contour-following task: the closure of a ziplock bag. This task is challenging for robots because the bag is deformable, transparent, and visually occluded by artificial fingertip sensors that are also compliant. A deep neural net classifier was trained to estimate the state of a zipper within a robot's pinch grasp. A Contextual Multi-Armed Bandit (C-MAB) reinforcement learning algorithm was implemented to maximize cumulative rewards by balancing exploration versus exploitation of the state-action space. The C-MAB learner outperformed a benchmark Q-learner by more efficiently exploring the state-action space while learning a hard-to-code task. The learned C-MAB policy was tested with novel ziplock bag scenarios and contours (wire, rope). Importantly, this work contributes to the development of reinforcement learning approaches that account for limited resources such as hardware life and researcher time. As robots are used to perform complex, physically interactive tasks in unstructured or unmodeled environments, it becomes important to develop methods that enable efficient and effective learning with physical testbeds.
ToH Poster B5
Evaluation of the Perceptual Characteristics of a Force Induced by Asymmetric Vibrations
(University of Tsukuba, Japan)
This paper describes the properties of proprioceptive sensations induced by asymmetric vibration using a vibration speaker-type non-grounded haptic interface. We confirm that the vibration speaker generates a perceived force that pulls or pushes a user's hand in a particular direction when an asymmetric amplitude signal that is generated by inverting a part of a sine wave is input. In this paper, to verify the system with respect to various factors of force perception caused by asymmetric vibration, we conducted six experiments and the following results were obtained. (1) The force vector can be controlled by reversing the asymmetric waves. (2) By investigating the physical characteristics of the vibration, asymmetric vibration was confirmed. (3) The presentation of vibration in the shear direction on the finger pad is effective. (4) The point of subjective equality of the perceived force can be controlled by up to 0.43 N by changing the amplitude voltage of the input signals. (5) The minimum stimulation time required for force perception is 66.7 ms. (6) When the vibration is continuously presented for 40 to 50 s, the perceived force decreases because of adaptation. Hence, we confirmed that we can control both the direction and magnitude of the reaction force by changing the input signal of the vibration speaker.
ToH Poster B6
Characterizing and Imaging Gross and Real Finger Contacts under Dynamic Loading
Serena Bochereau, Brygida Dzidek, Mike Adams, and Vincent Hayward
(Sorbonne University, France; University of Birmingham, UK)
We describe an instrument intended to study finger contacts under tangential dynamic loading. This type of loading is relevant to the natural conditions when touch is used to discriminate and identify the properties of the surfaces of objects-it is also crucial during object manipulation. The system comprises a high performance tribometer able to accurately record in vivo the components of the interfacial forces when a finger interacts with arbitrary surfaces which is combined with a high-speed, high-definition imaging apparatus. Broadband skin excitation reproducing the dynamic contact loads previously identified can be effected while imaging the contact through a transparent window, thus closely approximating the condition when the skin interacts with a non-transparent surface during sliding. As a preliminary example of the type of phenomenon that can be identified with this apparatus, we show that traction in the range from 10 to 1000 Hz tends to decrease faster with excitation frequency for dry fingers than for moist fingers.
IEEE Transactions on Haptics Best Paper Award
ToH Poster C1
KiloHertz Bandwidth, Dual-Stage Haptic Device Lets You Touch Brownian Motion
Tianming Lu, Cecile Pacoret, David Hériban, Abdenbi Mohand-Ousaid, Stéphane Régnier, and Vincent Hayward
(Sorbonne University, France; University of Geneva, Switzerland; Percipio Robotics, France; University Bourgogne Franche-Comté, France; UFC, France; CNRS, France; ENSMM, France)
This paper describes a haptic interface that has a uniform response over the entire human tactile frequency range. Structural mechanics makes it very difficult to implement articulated mechanical systems that can transmit high frequency signals. Here, we separated the frequency range into two frequency bands. The lower band is within the first structural mode of the corresponding haptic device while the higher one can be transmitted accurately by a fast actuator operating from conservation of momentum, that is, without reaction forces to the ground. To couple the two systems, we adopted a channel separation approach akin to that employed in the design of acoustic reproduction systems. The two channels are recombined at the tip of the device to give a uniform frequency response from DC to one kHz. In terms of mechanical design, the high-frequency transducer was embedded inside the tip of the main stage so that during operation, the human operator has only to interact with a single finger interface. In order to exemplify the type of application that would benefit from this kind of interface, we applied it to the haptic exploration with microscopic scales objects which are known to behave with very fast dynamics. The novel haptic interface was bilaterally coupled with a micromanipulation platform to demonstrate its capabilities. Operators could feel interaction forces arising from contact as well as those resulting from Brownian motion and could manoeuvre a micro bead in the absence of vision.
ToH Poster C3
Effect of Electrostatic Tactile Feedback on Accuracy and Efficiency of Pan Gestures on Touch Screens
Guohong Liu, Xiaoying Sun, Dangxiao Wang, Yue Liu, and Yuru Zhang
(Jilin University, China; Beihang University, China; Beijing Institute of Technology, China)
Recently, many studies examined electrostatic tactile feedback on touch screens to enrich interaction experience. However, it is unclear as to whether added tactile feedback during a sliding process increases the accuracy of pan gestures with velocity constraints. In this study, a custom-designed electrostatic tactile display was considered. Initially, the accuracy and efficiency of pan gestures were compared under two conditions, namely with and without electrostatic tactile feedback. This was followed by exploring the evolution of completion time (CT) with different indices of difficulties (ID). Experimental results with twelve participants indicated that the accuracy and completion time of pan gestures with added tactile feedback significantly exceeded those without tactile feedback. Furthermore, the relationship between CT and ID satisfied Fitts' Law with a correlation coefficient exceeding 0.9. Based on the findings, a “Tactile Fruit Sorting” game was designed, and subjective and objective evaluations were conducted. The results confirmed that the added tactile feedback enhanced both user performance and interest with respect to the game.
ToH Poster C4
Localization Performance of Multiple Vibrotactile Cues on Both Arms
Dangxiao Wang, Cong Peng, Naqash Afzal, Weiang Li, Dong Wu, and Yuru Zhang
(Beihang University, China; Beijing Sports University, China)
To present information using vibrotactile stimuli in wearable devices, it is fundamental to understand human performance of localizing vibrotactile cues across the skin surface. In this paper, we studied human ability to identify locations of multiple vibrotactile cues activated simultaneously on both arms. Two haptic bands were mounted in proximity to the elbow and shoulder joints on each arm, and two vibrotactile motors were mounted on each band to provide vibration cues to the dorsal and palmar side of the arm. The localization performance under four conditions were compared, with the number of the simultaneously activated cues varying from one to four in each condition. Experimental results illustrate that the rate of correct localization decreases linearly with the increase in the number of activated cues. It was 27.8% for three activated cues, and became even lower for four activated cues. An analysis of the correct rate and error patterns show that the layout of vibrotactile cues can have significant effects on the localization performance of multiple vibrotactile cues. These findings might provide guidelines for using vibrotactile cues to guide the simultaneous motion of multiple joints on both arms.
ToH Poster C5
Effects of Concurrent and Delayed Visual Feedback on Motor Memory Consolidation
Dangxiao Wang, Teng Li, Gaofeng Yang, and Yuru Zhang
(Beihang University, China)
In many domains, it's important to understand the ways in which humans learn and develop new motor skills effectively and efficiently. For example, in dental operations, the ability to apply a weak force with a required tolerance is a fundamental skill to ensure diagnostic and treatment outcome, but acquiring such a skill is a challenge for novices. In this paper, we focus on motor memory for producing normally applied force by a hand-held probe and we compare the effects of two feedback methods on motor memory consolidation. Fourteen participants were randomly assigned to two groups: a Concurrent Group and a Delayed Group. Participants in the Concurrent Group were trained to apply a target force with concurrent visual feedback, while those in the Delayed Group were trained with delayed visual feedback. The task included two phases: a Training/Testing Phase, and a Retention Phase. The results indicated that participants in the Delayed Group obtained more effective learning outcomes and better retention effects. These findings provide a new perspective to explore the relationship between feedback methods and the cognitive process of motor skill learning, and open a new way to train motor skill using more effective methods than the traditional concurrent feedback approaches.
ToH Poster C6
Multimodal Evaluation of the Differences between Real and Virtual Assemblies
(German Aerospace Center, Germany)
What are the technological bottlenecks in virtual assembly simulations with haptic feedback? To tackle this question, we present an evaluation study in which real feedback modalities are gradually replaced by synthetic ones. In particular, the effects of the following factors on the user performance and perception during virtual assemblies are analyzed: (i) a visual feedback system consisting of an nVisor head-mounted display, (ii) our haptic device HUG suited for unscaled upper-body movements, and (iii) our novel six-DoF constraint-based haptic rendering algorithm. Besides of that, the influence of (iv) real collision sounds is also examined to a lesser extent. The experimental assembly scenario consisted of three variations of peg-in-hole tasks which were performed by a total of N = 24 participants in a within-design study. The mentioned three synthetic factors (i)-(iii) gradually replaced in five degrees or steps the real feedback sources, ending up in completely virtual assembly simulations. For each of the degrees, three objective variables (completion time, collision forces, and muscular effort) and five subjective ratings (related to the perception of realism and the workload) were recorded and statistically analyzed. In order to explain subjective perception also with objective measures, reaction times of a secondary audio task performed in parallel with the assembly exercises were recorded, too. While previous works have mainly focused on differences of completion time between real and virtual manipulations, our results show how all of the mentioned twelve performance and perception indicators are influenced by each of the four varied feedback factors, building a multi-modality relationship function that maps our or similar systems and expected user responses. In general, the haptic feedback modality turned out to have the largest impact on the dependent variables, particularly the HUG interface, whereas audio cues seemed to be less significant. We quantify these previous and further qualitative statements within the domain defined by the used systems. Moreover, the relationship of our insights with related other work is discussed, and their projections are outlined.
ToH Poster C7
Force-Rate Cues Reduce Object Deformation Necessary to Discriminate Compliances Harder Than the Skin
(University of Virginia, USA)
Grasping and manipulating an object requires us to perceive its material compliance. Compliance is thought to be encoded by relationships of force, displacement and contact area at the finger pad. Prior work suggests that objects must be sufficiently deformed to become discriminable, but the utility of time-dependent cues has not been fully explored. The studies herein find that the availability of force-rate cues improve compliance discriminability so as to require less deformation of stimulus and finger pad. In particular, we tested the impact of controlling force-rate and displacement-rate cues in passive touch psychophysical experiments. An ink-based method to mark the finger pad was used to measure contact area per stimulus, simultaneously with displacement and force. Compliances spanned a range harder and softer than the finger pad. The results indicated harder compliances were discriminable at lower peak forces when the stimulus control mode was displacement-rate (0.5 N) compared to force-rate (1.3 N). That is, when displacement-rate was controlled to be equal between the two compliances, the resultant force-rate psychophysical cues could be more readily discriminated. In extending prior studies, while some magnitude of finger pad deformation may be sufficient for discriminability, temporal cues tied to force afford more efficient judgments.
ToH Poster C8
Shape Localization and Recognition using a Magnetorheological-Fluid Haptic Display
Rocco Rizzo, Antonino Musolino, and Lynette A. Jones
(University of Pisa, Italy; Massachusetts Institute of Technology, USA)
Smart materials such as magnetorheological fluids (MRF) offer an interesting technology for use in haptic displays as changes in the magnetic field are rapid, reversible and controllable. These interfaces have been evaluated in a number of medical and surgical simulators where they can provide cues regarding the viscoelastic properties of tissues. The objective of the present set of experiments was first to determine whether a shape embedded in the MRF could be precisely localized and second whether ten shapes rendered in a MRF haptic display could be accurately identified. It was also of interest to determine how the information transfer associated with this type of haptic display compares to that achieved using other haptic channels of communication. The overall performance of participants at identifying the shapes rendered in the MRF was good with a mean score of 73% correct and an Information Transfer (IT) of 2.2 bits. Participants could also localize a rigid object in the display accurately. These findings indicate that this technology has potential for use in training manual palpation skills and in exploring haptic shape perception in dynamic environments.
ToH Poster D2
Haptic Orientation Guidance using Two Parallel Double-Gimbal Control Moment Gyroscopes
(Stanford University, USA)
This paper presents a system of two double-gimbal control moment gyroscopes (CMGs) for providing ungrounded kinesthetic haptic feedback. By spinning a second flywheel opposite the first, and rotating them through opposite trajectories, undesired gyroscopic effects can be eliminated, isolating a single torque axis. This produces a moment pulse proportional to the flywheel spin speed and rotation speed. Rotating the CMG gimbals quickly in one direction, then resetting them more slowly generates repeated torque pulses indicating a clear direction cue. We present the mathematical model for moments produced by this system and verify that the performance of our device matches this model. Using these asymmetric moment pulses, we provide haptic cues to participants in two studies. In the first study, users simply identify the direction of torque cues. In the second study, we use the torque pulses to guide users to target orientations. Performance in both studies shows that this system has the potential to provide useful guidance for applications where ungrounded haptic feedback is desired.
ToH Poster D3
A Multi-finger Interface with MR Actuators for Haptic Applications
Huanhuan Qin, Aiguo Song, Zhan Gao, Yuqing Liu, and Guohua Jiang
(Southeast University, China; China Astronaut Research and Training Center, China)
Multi-finger operations provide realistic and natural methods when interacting with remote or virtual environment. Hence, haptic devices with multi-finger input are highly desirable. MR (Magneto-rheological) actuators are preferable options in haptics, because they can produce larger passive torque and have larger torque-volume ratios than the conventional actuators. Among the existing haptic MR actuators, most of them are still bulky and heavy. If they were smaller and lighter, they would become more suitable for haptics. In this paper, a small-scale yet powerful MR actuator was designed to build a multi-finger interface for the 6 DOF haptic device. The compact structure was achieved by adopting the multi-disc configuration. Based on this configuration, the MR actuator can generate the maximum torque of 480 N.mm with dimensions of only 36 mm diameter and 18 mm height. Performance evaluation showed that it can exhibit a relatively high dynamic range and good response characteristics when compared with some other haptic MR actuators. The multi-finger interface is equipped with three MR actuators and can provide up to 8 N passive force to the thumb, index and middle fingers, respectively. An application example was used to demonstrate the effectiveness and potential of this new MR actuator based interface.
ToH Poster D4
Encountered-Type Haptic Interface for Representation of Shape and Rigidity of 3D Virtual Objects
Naoki Takizawa, Hiroaki Yano, Hiroo Iwata, Yukio Oshiro, and Nobuhiro Ohkohch
(University of Tsukuba, Japan)
This paper describes the development of an encountered-type haptic interface that can generate the physical characteristics, such as shape and rigidity, of three-dimensional (3D) virtual objects using an array of newly developed non-expandable balloons. To alter the rigidity of each non-expandable balloon, the volume of air in it is controlled through a linear actuator and a pressure sensor based on Hooke's law. Furthermore, to change the volume of each balloon, its exposed surface area is controlled by using another linear actuator with a trumpet-shaped tube. A position control mechanism is constructed to display virtual objects using the balloons. The 3D position of each balloon is controlled using a flexible tube and a string. The performance of the system is tested and the results confirm the effectiveness of the proposed principle and interface.
ToH Poster D5
Torque Contribution to Haptic Rendering of Virtual Textures
(University of California at Los Angeles, USA; Carnegie Mellon University, USA; University of Hawaii at Manoa, USA)
Despite the fact that conventional haptic interfaces and rendering algorithms commonly approximate interactions with force only, the dynamic effects of even simple tasks, e.g., writing on a paper, involve both forces and torques. To extend previous algorithms as well as to investigate the effects of torque feedback on human roughness perception, we deployed a novel haptic platform with two probes, fingertip and penhandle. Three torque conditions were examined: 1) Slope Torque, which orients the probe perpendicular to the surface, 2) No Torque, where no active torque is provided by the device, and 3) Stiff Torque, where torque feedback is provided to keep the probe upright. A conventional magnitude estimation experiment was performed. The results indicated that both the torque signals and grasp type mediate human perception of virtual textures. Slope Torque led to greater perceived roughness when the fingertip was used, and the fingertip led to higher roughness ratings than the penhandle with the Slope Torque condition. The Slope Torque algorithm appears to be advantageous for generating rougher surfaces compared to the force-based algorithms which are typically limited by the system stability and actuator saturation.
ToH Poster D6
A Physics-Based Vibrotactile Feedback Library for Collision Events
(POSTECH, South Korea)
We present PhysVib: a software solution on the mobile platform extending an open-source physics engine in a multi-rate rendering architecture for automatic vibrotactile feedback upon collision events. PhysVib runs concurrently with a physics engine at a low update rate and generates vibrotactile feedback commands at a high update rate based on the simulation results of the physics engine using an exponentially-decaying sinusoidal model. We demonstrate through a user study that this vibration model is more appropriate to our purpose in terms of perceptual quality than more complex models based on sound synthesis. We also evaluated the perceptual performance of PhysVib by comparing eight vibrotactile rendering methods. Experimental results suggested that PhysVib enables more realistic vibrotactile feedback than the other methods as to perceived similarity to the visual events. PhysVib is an effective solution for providing physically plausible vibrotactile responses while reducing application development time to great extent.
ToH Poster D7
Improving 3D Shape Recognition with Electrostatic Friction Display
(POSTECH, South Korea; Electronics and Telecommunications Research Institute, South Korea)
Electrovibration technology has the potential for seamless integration into ordinary smartphones and tablets to provide programmable haptic feedback. The aim of this work is to seek effective ways to improve 3D perception of visual objects rendered on an electrovibration display. Utilizing a gradient-based algorithm, we first investigated whether rendering only lateral frictional force on an electrovibration display improves 3D shape perception compared to doing the same using a force-feedback interface. We observed that although users do not naturally associate electrovibration patterns to geometrical shapes, they can map patterns to shapes with moderate accuracy if guidance or context is given. Motivated by this finding, we generalized the gradient-based rendering algorithm to estimate the surface gradient for any 3D mesh and added an edge detection algorithm to render sharp edges. Then, we evaluated the advantages of our algorithm in a user study and found that our algorithm can notably improve the performance of 3D shape recognition when visual information is limited.
ToH Poster D8
Intermanual Apparent Tactile Motion and Its Extension to 3D Interactions
(Carnegie Mellon University, USA; Disney Research, USA)
Information provided by sensory systems is inherently ambiguous as to its source in the physical world. To arrive at a coherent representation, perception deploys heuristic rules and multimodal input, which potentially produce errors such as illusions. The current work uses these effects to create apparent tactile motion and illusory depth motion using sparse vibrotactile stimulation across the hands. Experiment 1 showed the effects of vibrotactile duration and temporal separation between the hands on the quality of perceived illusory linear motion. Experiment 2 indicated a compressed linear relation between the visual and tactile speeds, and established a linear function relating visual size to perceived tactile intensity at three durations. Experiment 3 introduced an “M-filter” algorithm that varies tactile stimulus amplitude by a parabolic function based on visual looming and receding. It demonstrated that the M-filters, accompanied by visual depth cues, can induce tactile motion in depth. Experiment 4 showed the M-filter algorithm is necessary to create tactile perception in depth, as opposed to apparent tactile motion. The current research has value for a basic understanding of haptic perception, as well as haptic applications that digitally generate perceptual representations of the distal world on small-sized devices in the space between the hands.
ToH Poster E1
Effect of Waveform on Tactile Perception by Electrovibration Displayed on Touch Screens
Yasemin Vardar, Burak Güçlü, and Cagatay Basdogan
(Koç University, Turkey; Boğaziçi University, Turkey)
In this study, we investigated the effect of input voltage waveform on our haptic perception of electrovibration on touch screens. Through psychophysical experiments performed with eight subjects, we first measured the detection thresholds of electrovibration stimuli generated by sinusoidal and square voltages at various fundamental frequencies. We observed that the subjects were more sensitive to stimuli generated by square wave voltage than sinusoidal one for frequencies lower than 60 Hz. Using Matlab simulations, we showed that the sensation difference of waveforms in low fundamental frequencies occurred due to the frequency-dependent electrical properties of human skin and human tactile sensitivity. To validate our simulations, we conducted a second experiment with another group of eight subjects. We first actuated the touch screen at the threshold voltages estimated in the first experiment and then measured the contact force and acceleration acting on the index fingers of the subjects moving on the screen with a constant speed. We analyzed the collected data in the frequency domain using the human vibrotactile sensitivity curve. The results suggested that Pacinian channel was the primary psychophysical channel in the detection of the electrovibration stimuli caused by all the square-wave inputs tested in this study. We also observed that the measured force and acceleration data were affected by finger speed in a complex manner suggesting that it may also affect our haptic perception accordingly.
ToH Poster E2
Vibration Feedback Latency Affects Material Perception during Rod Tapping Interactions
Taku Hachisu and Hiroyuki Kajimoto
(University of Tsukuba, Japan; University of Electro-Communications, Japan)
We investigated the effect of vibration feedback latency on material perception during a tapping interaction using a rod device. When a user taps a surface, the perception of the material can be modulated by providing a decaying sinusoidal vibration at the moment of contact. To achieve this haptic material augmentation on a touchscreen, a system that can measure the approach velocity and provide vibration with low latency is required. To this end, we developed a touchscreen system that is capable of measuring the approach velocity and providing vibration feedback via a rod device with latency of 0.1 ms. Using this system, we experimentally measured the human detection threshold of the vibration feedback latency adopting a psychophysical approach. We further investigated the effect of latency on the perception of the material using a subjective questionnaire. Results show that the threshold was around 5.5 ms and the latency made the user feel that the surface is soft. In addition, users reported bouncing and denting sensations induced by the latency.
ToH Poster E3
The Role of Direct and Visual Force Feedback in Suturing using a 7-DOF Dual-Arm Teleoperated System
Ali Talasaz, Ana Luisa Trejos, and Rajni Patel
(Stryker, USA; CSTAR, Canada; Lawson Health Research Institute, Canada)
The lack of haptic feedback in robotics-assisted surgery can result in tissue damage or accidental tool-tissue hits. This paper focuses on exploring the effect of haptic feedback via direct force reflection and visual presentation of force magnitudes on performance during suturing in robotics-assisted minimally invasive surgery (RAMIS). For this purpose, a haptics-enabled dual-arm master-slave teleoperation system capable of measuring tool-tissue interaction forces in all seven Degrees-of-Freedom (DOFs) was used. Two suturing tasks, tissue puncturing and knot-tightening, were chosen to assess user skills when suturing on phantom tissue. Sixteen subjects participated in the trials and their performance was evaluated from various points of view: force consistency, number of accidental hits with tissue, amount of tissue damage, quality of the suture knot, and the time required to accomplish the task. According to the results, visual force feedback was not very useful during the tissue puncturing task as different users needed different amounts of force depending on the penetration of the needle into the tissue. Direct force feedback, however, was more useful for this task to apply less force and to minimize the amount of damage to the tissue. Statistical results also reveal that both visual and direct force feedback were required for effective knot tightening: direct force feedback could reduce the number of accidental hits with the tissue and also the amount of tissue damage, while visual force feedback could help to securely tighten the suture knots and maintain force consistency among different trials/users. These results provide evidence of the importance of 7-DOF force reflection when performing complex tasks in a RAMIS setting.
ToH Poster E4
Linkage between Free Exploratory Movements and Subjective Tactile Ratings
Takumi Yokosaka, Scinob Kuroki, Junji Watanabe, and Shin'ya Nishida
(NTT, Japan)
We actively move our hands and eyes when exploring the external world and gaining information about object's attributes. Previous studies showing that how we touch might be related to how we felt led us to consider whether we could decode observers' subjective tactile experiences only by analyzing their exploratory movements without explicitly asking how they perceived. However, in those studies, explicit judgment tasks were performed about specific tactile attributes that were prearranged by experimenters. Here, we systematically investigated whether exploratory movements can explain tactile ratings even when participants do not need to judge any tactile attributes. While measuring both hand and eye movements, we asked participants to touch materials freely without judging any specific tactile attributes (free-touch task) or to evaluate one of four tactile attributes (roughness, hardness, slipperiness, and temperature). We found that tactile ratings in the judgment tasks correlated with exploratory movements even in the free-touch task and that eye movements as well as hand movements correlated with tactile ratings. These results might open up the possibility of decoding tactile experiences by exploratory movements.
ToH Poster E5
Physical-Perceptual Correspondence for Dynamic Thermal Stimulation
Hsin-Ni Ho, Katsunari Sato, Scinob Kuroki, Junji Watanabe, Takashi Maeno, and Shin'ya Nishida
(NTT, Japan; Nara Women's University, Japan; Keio University, Japan)
Thermal displays have been applied in various haptic applications, from material simulation to interpersonal communication; however, there is insufficient knowledge about the temporal processing in human thermal sense to provide a knowledge basis for thermal display design. In this study, we investigated the physical-perceptual correspondence for dynamic thermal stimulation to shed a light on the temporal processing of human thermal sense. In the experiments, participants reported subjective timings of the temperature onset and temperature peak of continuous temperature changes applied to the thenar eminence. We found that the physical-perceptual correspondence was not consistent for warm and cold stimulations. For warm stimulation, the subjective experience always came after the corresponding physical event. On the other hand, for cold stimulation, while the subjective onset always lagged the physical onset, the subjective temperature peak preceded the physical temperature peak. We analyzed these results in the framework of linear systems theory. The results suggest that the senses of warmth and cold have distinct temporal filtering properties, with the sense of cold being more transient than the sense of warmth. These findings advance our knowledge regarding temporal processing in human thermal sense and serve as a basis for thermal display design.
ToH Poster E6
Friction Reduction through Ultrasonic Vibration Part 1: Modelling Intermittent Contact
Eric Vezzoli, Zlatko Virdih, Vincenzo Giamundo, Betty Lemaire-Semail, Frédéric Giraud, Tomaz Rodic, Djordje Peric, and Mike Adams
(University of Lille, France; Arts et Metiers ParisTech, France; HEI, France; L2EP, France; Swansea University, UK; Centre for Computational Continuum Mechanics, Slovenia; University of Birmingham, UK)
Ultrasonic vibration is employed to modify the friction of a finger pad in way that induces haptic sensations. A combination of intermittent contact and squeeze film levitation has been previously proposed as the most probable mechanism. In this paper, in order to understand the underlying principles that govern friction modulation by intermittent contact, numerical models based on finite element (FE) analysis and also a spring-Coulombic slider are developed. The physical input parameters for the FE model are optimized by measuring the contact phase shift between a finger pad and a vibrating plate. The spring-slider model assists in the interpretation of the FE model and leads to the identification of a dimensionless group that allows the calculated coefficient of friction to be approximately superimposed onto an exponential function of the dimensionless group. Thus, it is possible to rationalize the computed relative reduction in friction being (i) dependent on the vibrational amplitude, frequency, and the intrinsic coefficient of friction of the device, and the reciprocal of the exploration velocity, and (ii) independent of the applied normal force, and the shear and extensional elastic moduli of the finger skin provided that intermittent contact is sufficiently well developed. Experimental validation of the modelling using real and artificial fingertips will be reported in part 2 of this work, which supports the current modelling.
ToH Poster F1
Perceived Cooling using Asymmetrically-Applied Hot and Cold Stimuli
Ahmad Manasrah, Nathan Crane, Rasim Guldiken, and Kyle B. Reed
(University of South Florida, USA)
Temperature perception is a highly nonlinear phenomenon with faster rates of change being perceived at much lower thresholds than slower rates. This paper presents a method that takes advantage of this nonlinear characteristic to generate a perception of continuous cooling even though the average temperature is not changing. The method uses multiple thermal actuators so that a few are cooling quickly while the rest of the actuators are heating slowly. The slowly-heating actuators are below the perceptual threshold temperature change and hence are not perceived, while the quickly-cooling actuators are above the perceptual temperature change, hence are perceived. As a result, a feeling of decreasing temperature was elicited, when in fact, there was no net change in the temperature of the skin. Three sets of judiciously designed experiments were conducted in this study, investigating the effects of actuator sizes, forearm measurement locations, patterns of actuator layout, and various heating/cooling time cycles. Our results showed that 19 out 21 participants perceived the continuous cooling effect as hypothesized. Our research indicates that the measurement location, heating/cooling cycle times, and arrangement of the actuators affect the perception of continuous cooling.
ToH Poster F2
Importance of Matching Physical Friction, Hardness, and Texture in Creating Realistic Haptic Virtual Surfaces
(Stanford University, USA; Max Planck Institute for Intelligent Systems, Germany)
Interacting with physical objects through a tool elicits tactile and kinesthetic sensations that comprise your haptic impression of the object. These cues, however, are largely missing from interactions with virtual objects, yielding an unrealistic user experience. This article evaluates the realism of virtual surfaces rendered using haptic models constructed from data recorded during interactions with real surfaces. The models include three components: surface friction, tapping transients, and texture vibrations. We render the virtual surfaces on a SensAble Phantom Omni haptic interface augmented with a Tactile Labs Haptuator for vibration output. We conducted a human-subject study to assess the realism of these virtual surfaces and the importance of the three model components. Following a perceptual discrepancy paradigm, subjects compared each of 15 real surfaces to a full rendering of the same surface plus versions missing each model component. The realism improvement achieved by including friction, tapping, or texture in the rendering was found to directly relate to the intensity of the surface's property in that domain (slipperiness, hardness, or roughness). A subsequent analysis of forces and vibrations measured during interactions with virtual surfaces indicated that the Omni's inherent mechanical properties corrupted the user's haptic experience, decreasing realism of the virtual surface.
ToH Poster F3
Effects of Grip-Force, Contact, and Acceleration Feedback on a Teleoperated Pick-and-Place Task
(Boston University, USA; University of Pennsylvania, USA; Max Planck Institute for Intelligent Systems, Germany)
The multifaceted human sense of touch is fundamental to direct manipulation, but technical challenges prevent most teleoperation systems from providing even a single modality of haptic feedback, such as force feedback. This paper postulates that ungrounded grip-force, fingertip-contact-and-pressure, and high-frequency acceleration haptic feedback will improve human performance of a teleoperated pick-and-place task. Thirty subjects used a teleoperation system consisting of a haptic device worn on the subject's right hand, a remote PR2 humanoid robot, and a Vicon motion capture system to move an object to a target location. Each subject completed the pick-and-place task 10 times under each of the eight haptic conditions obtained by turning on and off grip-force feedback, contact feedback, and acceleration feedback. To understand how object stiffness affects the utility of the feedback, half of the subjects completed the task with a flexible plastic cup, and the others used a rigid plastic block. The results indicate that the addition of grip-force feedback with gain switching enables subjects to hold both the flexible and rigid objects more stably, and it also allowed subjects who manipulated the rigid block to hold the object more delicately and to better control the motion of the remote robot's hand. Contact feedback improved the ability of subjects who manipulated the flexible cup to move the robot's arm in space, but it deteriorated this ability for subjects who manipulated the rigid block. Contact feedback also caused subjects to hold the flexible cup less stably, but the rigid block more securely. Finally, adding acceleration feedback slightly improved the subject's performance when setting the object down, as originally hypothesized; interestingly, it also allowed subjects to feel vibrations produced by the robot's motion, causing them to be more careful when completing the task. This study supports the utility of grip-force and high-frequency acceleration feedback in teleoperation systems and motivates further improvements to fingertip-contact-and-pressure feedback.
ToH Poster F4
Design and Evaluation of Shape-Changing Haptic Interfaces for Pedestrian Navigation Assistance
Adam J. Spiers and Aaron M. Dollar
(Yale University, USA)
Shape-changing interfaces are a category of device capable of altering their form in order to facilitate communication of information. In this work, we present a shape-changing device that has been designed for navigation assistance. `The Animotus' (previously, `The Haptic Sandwich' ), resembles a cube with an articulated upper half that is able to rotate and extend (translate) relative to the bottom half, which is fixed in the user's grasp. This rotation and extension, generally felt via the user's fingers, is used to represent heading and proximity to navigational targets. The device is intended to provide an alternative to screen or audio based interfaces for visually impaired, hearing impaired, deafblind, and sighted pedestrians. The motivation and design of the haptic device is presented, followed by the results of a navigation experiment that aimed to determine the role of each device DOF, in terms of facilitating guidance. An additional device, `The Haptic Taco', which modulated its volume in response to target proximity (negating directional feedback), was also compared. Results indicate that while the heading (rotational) DOF benefited motion efficiency, the proximity (translational) DOF benefited velocity. Combination of the two DOF improved overall performance. The volumetric Taco performed comparably to the Animotus' extension DOF.
ToH Poster F5
Decision-Making Model for Adaptive Impedance Control of Teleoperation Systems
Javier Corredor, Jorge Sofrony, and Angelika Peer
(University of Pamplona, Colombia; Universidad Nacional de Colombia, Colombia; University of the West of England, UK)
This paper presents a haptic assistance strategy for teleoperation that makes a task and situation-specific compromise between improving tracking performance or human-machine interaction in partially structured environments via the scheduling of the parameters of an admittance controller. The proposed assistance strategy builds on decision-making models and combines one of them with impedance control techniques that are standard in bilateral teleoperation systems. Even though several decision-making models have been proposed in cognitive science, their application to assisted teleoperation and assisted robotics has hardly been explored yet. Experimental data supports the Drift-Diffusion model as a suitable scheduling strategy for haptic shared control, in which the assistance mechanism can be adapted via the parameters of reward functions. Guidelines to tune the decision making model are presented. The influence of the reward structure on the realized haptic assistances is evaluated in a user study and results are compared to the no assistance and human assistance case.
ToH Poster F6
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Open Office Hours on Accessible Technology with Members of LightHouse for the Blind and Visually Impaired
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