Haptic Interfaces: Collocation and Coherence Issues

Multi-modality, collocation and immersive VE nowadays represents the break-trough barrier of human computer interaction. Typical VE systems synthesize the information to be presented to the user by means of different algorithms and present them using different interfaces. On the other hand the human perceptive system is strongly integrated and “fatigues” to interpret these stimuli as belonging to a unique information source. Collocation and coherence issues may be noticed in any kind of multimodal integration: “visual and audio”, “visual and vestibular”, “audio and haptic”, “visual and haptic”, ... The present chapter deals with two specific kinds of multimodal integration: “visual and haptic” and “haptic and haptic”. The coherence problem of synchronizing several haptic devices is analyzed and an optimized solution is proposed. The proposed solution has been tested on a dual point HI, behaving a wide workspace realized at PERCRO. More specifically the present chapter will present a novel algorithm to achieve the absolute coordination of multiple HI working in the same VE. The system performances have been assessed and compared to those of existing solutions. The achieved results have been exploited for the EU project GRAB. The GRAB project investigates to which extent a purely haptic environment can be employed from sightless users.