As the field of haptics in virtual reality expands, wearable devices are being explored as alternatives to traditional kinesthetic force feedback devices, which are often limited in workspace. Skin deformation feedback offers a user-grounded feedback modality that mimics cutaneous interactions with the real world but can suffer from force-output saturation due to the actuation constraints required to achieve a small form factor. Saturation of haptic devices limits the mechanical properties and interactions that can be rendered in a virtual environment, specifically the weight that can be rendered when a user manipulates a virtual object. We use scaled inertial forces to alter virtual weight perception during a dynamic grasp-lift-and-place task in a virtual environment with haptic feedback via two wearable skin deformation feedback devices. A study was conducted, beginning with an open response exercise to assess how participants interpreted scaled inertial forces when interacting with virtual blocks. Participants then performed a series of trials to measure the Point of Subjective Equality of virtual weight with scaled inertial forces, using a reference of 200 g under the normal (no scaling) condition. PSEs for inertial scaling factors of 2 and 3 were 171 g and 151 g, respectively. These results demonstrate the effectiveness of a unique haptic rendering algorithm that can convey larger weights without saturating the force output of the haptic device.

Virtual and augmented reality systems that immerse users in a 3D environment could benefit from haptic (force and/or tactile) feedback to increase realism and task performance. A canonical task that cannot be achieved compellingly without haptic feedback is the grasp and lift of an object with mass. Traditional kinesthetic (force) feedback devices provide realistic physical interactions with virtual objects, but typically require large actuators, making them bulky and encumbering. In contrast, tactile feedback devices can use smaller actuators and may enable freer movement of a user in a virtual world. One form of tactile feedback, skin deformation feedback, has been previously shown to provide effective haptic feedback of force, stiffness, and friction. Here we compare human perception of mass via kinesthetic feedback and skin deformation feedback in a virtual environment. Participants grasp and lift two virtual blocks and attempt to equalize their masses by the method of adjustments. From the accuracy of this equalization, we determined that the Weber Fraction (the just noticeable difference in proportion to the original stimulus value) of virtual mass during a grasp and lift task was 0.11 for kinesthetic force feedback and 0.35 for skin deformation feedback. In addition, participants exhibited differences in exploratory procedures between the two types of feedback.