Enhancing weight perception in virtual reality: an analysis of kinematic features

This study investigates weight perception in virtual reality without kinesthetic feedback from the real world, by means of an illusory method called pseudo-haptic. This illusory model focuses on the dissociation of visual input and somatosensory feedback and tries to induce the sensation of virtual objects' loads in VR users by manipulating visual input. For that, modifications on the control-display ratio, i.e., between the real and virtual motions of the arm, can be used to produce a visual illusionary effect on the virtual objects' positions as well. Therefore, VR users perceive it as velocity variations in the objects' displacements, helping them achieve a better sensation of virtual weight. A primary contribution of this paper is the development of a novel, holistic assessment methodology that measures the sense of the presence in virtual reality contexts, particularly when participants are lifting virtual objects and experiencing their weight. Our study examined the effect of virtual object weight on the kinematic parameters and velocity profiles of participants' upward arm motions, along with a parallel experiment conducted using real weights. By comparing the lifting of real objects with that of virtual objects, it was possible to gain insight into the variations in kinematic features observed in participants' arm motions. Additionally, subjective measurements, utilizing the Borg CR10 questionnaire, were conducted to assess participants' perceptions of hand fatigue. The analysis of collected data, encompassing both subjective and objective measurements, concluded that participants experienced similar sensations of fatigue and changes in hand kinematics during both virtual object tasks, resulting from pseudo-haptic feedback, and real weight lifting tasks. This consistency in findings underscores the efficacy of pseudo-haptic feedback in simulating realistic weight sensations in virtual environments.