Emerging virtual and augmented reality technologies can transform human activities in myriad domains, lending tangible, embodied form to digital data, services, and information. Haptic technologies will play a critical role in enabling human to touch and interact with the contents of these virtual environments. The immense variety of skilled manual tasks that humans perform in real environments are only possible through the coordination of touch sensation, perception, and movement that together comprise the haptic modality. Consequently, many research groups are vigorously investigating haptic technologies for virtual reality. A longstanding research goal in this area has been to create haptic interfaces that allow their users to touch and feel plausibly realistic virtual objects. In this progress report, the perspective on this unresolved research challenge is shared, guided by the observation that no technologies can even approximately match the capabilities of the human sense of touch. Factors that have it challenging to engineer haptic technologies for virtual reality, including the extraordinary spatial and temporal tactile acuity of the skin, and the complex interplay between continuum mechanics, haptic perception, and interaction are identified. The perspective on how these challenges may be overcome through convergent research on haptic perception, mechanics, electronics, and material technologies is presented.
Recent advances in extended reality (XR) technologies make seeing and hearing virtual objects commonplace, yet strategies for synthesizing haptic interactions with virtual objects continue to be limited. Two design principles govern the rendering of believable and intuitive haptic feedback: movement through open space must feel “free” while contact with virtual objects must feel stiff. Herein, a novel multisensory approach that conveys proprioception and effort through illusory visual feedback and refers to the wrist, via a bracelet interface, discrete and continuous interaction forces that would otherwise occur at the hands and fingertips, is presented. Results demonstrate that users reliably discriminate the stiffness of virtual buttons when provided with multisensory pseudohaptic feedback, comprising tactile pseudohaptic feedback (discrete vibrotactile feedback and continuous squeeze cues in a bracelet interface) and visual pseudohaptic illusions of touch interactions. Compared to the use of tactile or visual pseudohaptic feedback alone, multisensory pseudohaptic feedback expands the range of physical stiffnesses that are intuitively associated with the rendered virtual interactions and reduces individual differences in physical‐to‐virtual stiffness mappings. This multisensory approach, which leaves users' hands unencumbered, provides a flexible framework for synthesizing a wide array of touch‐enabled interactions in XR, with great potential for enhancing user experiences.
- NSF-PAR ID:
- 10396579
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Intelligent Systems
- Volume:
- 5
- Issue:
- 5
- ISSN:
- 2640-4567
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
Abstract -
more » « less
Abstract The goal of the field of haptics is to create technologies that manipulate the sense of touch. In virtual and augmented reality, haptic devices are for touch what loudspeakers and RGB displays are for hearing and vision. Haptic systems that utilize micromotors or other miniaturized mechanical devices (e.g., for vibration and pneumatic actuation) produce interesting effects, but are quite far from reproducing the feeling of real materials. They are especially deficient in recapitulating surface properties: fine texture, friction, viscoelasticity, tack, and softness. The central argument of this progress report is that in order to reproduce the feel of everyday objects, molecular control must be established over the properties of materials; ultimately, such control will enable the design of materials which can change these properties in real time. Stimuli‐responsive organic materials, such as polymers and composites, are a class of materials which can change their oxidation state, conductivity, shape, and rheological properties, and thus might be useful in future haptic technologies. Moreover, the use of such materials in research on tactile perception could help elucidate the limits of human tactile sensitivity. The work described represents the beginnings of this new area of inquiry, in which the defining approach is the marriage of materials science and psychology.
-
Tactile sensing has been increasingly utilized in robot control of unknown objects to infer physical properties and optimize manipulation. However, there is limited understanding about the contribution of different sensory modalities during interactive perception in complex interaction both in robots and in humans. This study investigated the effect of visual and haptic information on humans’ exploratory interactions with a ‘cup of coffee’, an object with nonlinear internal dynamics. Subjects were instructed to rhythmically transport a virtual cup with a rolling ball inside between two targets at a specified frequency, using a robotic interface. The cup and targets were displayed on a screen, and force feedback from the cup-andball dynamics was provided via the robotic manipulandum. Subjects were encouraged to explore and prepare the dynamics by “shaking” the cup-and-ball system to find the best initial conditions prior to the task. Two groups of subjects received the full haptic feedback about the cup-and-ball movement during the task; however, for one group the ball movement was visually occluded. Visual information about the ball movement had two distinctive effects on the performance: it reduced preparation time needed to understand the dynamics and, importantly, it led to simpler, more linear input-output interactions between hand and object. The results highlight how visual and haptic information regarding nonlinear internal dynamics have distinct roles for the interactive perception of complex objects.more » « less
-
Haptic interfaces can be used to add sensations of touch to virtual and augmented reality experiences. Soft, flexible devices that deliver spatiotemporal patterns of touch across the body, potentially with full-body coverage, are of particular interest for a range of applications in medicine, sports and gaming. Here we report a wireless haptic interface of this type, with the ability to display vibro-tactile patterns across large areas of the skin in single units or through a wirelessly coordinated collection of them. The lightweight and flexible designs of these systems incorporate arrays of vibro-haptic actuators at a density of 0.73 actuators per square centimetre, which exceeds the two-point discrimination threshold for mechanical sensation on the skin across nearly all the regions of the body except the hands and face. A range of vibrant sensations and information content can be passed to mechanoreceptors in the skin via time-dependent patterns and amplitudes of actuation controlled through the pressure-sensitive touchscreens of smart devices, in real-time with negligible latency. We show that this technology can be used to convey navigation instructions, to translate musical tracks into tactile patterns and to support sensory replacement feedback for the control of robotic prosthetics.more » « less
-
Madden, John D. ; Anderson, Iain A. ; Shea, Herbert R. (Ed.)Ras Labs makes Synthetic Muscle™, which is a class of electroactive polymer (EAP) based materials and actuators that sense pressure (gentle touch to high impact), controllably contract and expand at low voltage (1.5 V to 50 V, including use of batteries), and attenuate force. We are in the robotics era, but robots do have their challenges. Currently, robotic sensing is mainly visual, which is useful up until the point of contact. To understand how an object is being gripped, tactile feedback is needed. For handling fragile objects, if the grip is too tight, breakage occurs, and if the grip is too loose, the object will slip out of the grasp, also leading to breakage. Rigid robotic grippers using a visual feedback loop can struggle to determine the exact point and quality of contact. Robotic grippers can also get a stuttering effect in the visual feedback loop. By using soft Synthetic Muscle™ based EAP pads as the sensors, immediate feedback was generated at the first point of contact. Because these pads provided a soft, compliant interface, the first point of contact did not apply excessive force, allowing the force applied to the object to be controlled. The EAP sensor could also detect a change in pressure location on its surface, making it possible to detect and prevent slippage by then adjusting the grip strength. In other words, directional glide provided feedback for the presence of possible slippage to then be able to control a slightly tighter grip, without stutter, due to both the feedback and the soft gentleness of the fingertip-like EAP pads themselves. The soft nature of the EAP fingertip pad also naturally held the gripped object, improving the gripping quality over rigid grippers without an increase in applied force. Analogous to finger-like tactile touch, the EAPs with appropriate coatings and electronics were positioned as pressure sensors in the fingertip or end effector regions of robotic grippers. This development of using Synthetic Muscle™ based EAPs as soft sensors provided for sensors that feel like the pads of human fingertips. Basic pressure position and magnitude tests have been successful, with pressure sensitivity down to 0.05 N. Most automation and robots are very strong, very fast, and usually need to be partitioned away from humans for safety reasons. For many repetitive tasks that humans do with delicate or fragile objects, it would be beneficial to use robotics; whether it is for agriculture, medical surgery, therapeutic or personal care, or in extreme environments where humans cannot enter, including with contagions that have no cure. Synthetic Muscle™ was also retrofitted as actuator systems into off-the-shelf robotic grippers and is being considered in novel biomimetic gripper designs, operating at low voltages (less than 50 V). This offers biomimetic movement by contracting like human muscles, but also exceeds natural biological capabilities by expanding under reversed electric polarity. Human grasp is gentle yet firm, with tactile touch feedback. In conjunction with shape-morphing abilities, these EAPs also are being explored to intrinsically sense pressure due to the correlation between mechanical force applied to the EAP and its electronic signature. The robotic field is experiencing phenomenal growth in this fourth phase of the industrial revolution, the robotics era. The combination of Ras Labs’ EAP shape-morphing and sensing features promises the potential for robotic grippers with human hand-like control and tactile sensing. This work is expected to advance both robotics and prosthetics, particularly for collaborative robotics to allow humans and robots to intuitively work safely and effectively together.more » « less
