"A⁴": a technique to improve perception of contacts with under-actuated haptic devices in virtual reality

The objective of this paper is twofold. First, it aims at positioning the performance of under-actuated haptic devices as compared to fully-actuated haptic devices and unactuated devices (i.e. input devices) in virtual reality. Second, it proposes a technique - called "A⁴" - to improve the perception of contacts when using an under-actuated haptic device in virtual reality. This technique focuses on point-based haptic exploration. When a contact occurs in the simulation, we suggest to rotate the virtual scene in order to align the contact normal with the direction of the actuated axis (or axes) of the haptic device. With this technique, the virtual scene moves itself automatically to provide a more "realistic" sensation of contact. An experimental evaluation showed first that the performance of under-actuated force-feedback was located between the no-haptic condition (worst performance) and the full-haptic condition (best performance). Second, the use of the A⁴ technique decreased strongly the "penetration" inside virtual objects, and thus globally improved the performance of the participants in situation of under-actuation.