The increasing demand for virtual reality applications in several scientific disciplines feeds new research perspectives dealing with robotics, automation, and computer science. In this context, one of the topics is the design of advanced force-feedback devices allowing not only kinesthetic interaction with virtual objects but also locomotion and navigation inside virtual worlds. This has the main advantage to stimulate human vestibular apparatus, thus increasing the overall realism of simulation. Particularly, this paper deals with mobile haptic interfaces (MHIs), built by combining standard force-feedback devices with mobile platforms. We investigated which factors may affect the transparency of this kind of devices, identifying in mobile robot dynamics a possible cause of loss of transparency. Hence, in this paper, we present a method to analyze dynamic performance of an MHI and some basic guidelines to design controller in order to meet desired specifications. Experimental validation of the theoretical results is reported.

In real object manipulation, the deformation of the fingerpads along the contact surfaces provides local information about the geometry of the object the subject is manipulating, even in absence of vision and any exploratory movement. In virtual reality with haptic feedback this kind of stimulation is not available because the haptic devices currently available allow to simulate a contact point force interaction thus preventing the deformation of the fingerpads. The aim of this work is that of proposing a novel contact model to augment the information conveyed during kinesthetic interaction with single-point haptic devices. We extended the classic god-point algorithm by using a pseudo-ellipsoidal force field that creates anisotropic compliance in the neighborhood of the contact point. We performed several experiments in order to verify that such contact model can provide information about contact surface orientation even in absence of vision and of free voluntary exploration. The main finding was that participants could identify the orientation of the contact surface when the compliance was maximum in the tangential plane by using small exploratory movements allowed by the penalty-based contact model.