Wireality: Complex Tangible Geometries in VR with Worn Multi-String Haptics
Virtual reality (VR) systems (such as the Oculus Quest and HTC Vive) use controllers for tracking the hands, capturing buttoned input, and delivering basic vibrotactile haptic feedback. The latter is insufficient to produce immersive physical interactions with virtual objects. More critically, large obstacles like walls, railings, and furniture (key elements in most VR worlds) are not simulated at all. The current state-of-the-art in consumer VR systems is a vibration alert when a hand intersects a virtual object or obstacle, falling far short of any reality.
This shortcoming has long been recognized, and researchers have looked into ways to bring rich haptics to VR experiences for many decades. As we will review in greater detail, most systems have focused on hand haptics, such that virtual objects feel as though they are being held and are able to be moved in space. Less common are systems that attempt to arrest the hands and arms to simulate immovable objects, such as walls. To achieve this effect, systems often use mechanical exoskeletons or fixed infrastructure in the environment, neither of which is particularly practical for consumer use.
We set out to design a new VR haptic system that was entirely self-contained and mobile. This implied a worn system, which in turn, meant our approach needed to be both lightweight and battery-powered. To simulate interactions with heavy or fixed objects, we needed a system that was both fast-acting and able to provide large arresting forces. Finally, in order to be a plausible consumer accessory, it should cost no more than $50 in volume production.
In this paper, we present our work on Wireality, which meets the above design criteria. Our system is comprised of modular, spring-loaded cables, which we can programmatically lock with a ratchet gear and a solenoid-driven pawl. This locking action takes under 30ms, provides up to 180N of arresting force, and yet only consumes 0.024mWh of energy (allowing our approach to be battery powered and mobile). Each module is responsible for limiting one degree of freedom on the hand. With many modules acting together as a unit, Wireality enables interactions with complex geometries as users reach out towards, e.g., virtual walls, railings, and other objects. Our prototype weighs 273g in total, though only 11g is worn on the hands (making it considerably lighter than, e.g., an HTC Vive controller at 203g).
Fang, C., Zhang, Y., Dworman, M. and Harrison, C. 2020. Wireality: Enabling Complex Tangible Geometries in Virtual Reality with Worn Multi-String Haptics. In Proceedings of the 38th Annual SIGCHI Conference on Human Factors in Computing Systems. CHI '20. ACM, New York, NY.