Unident: Providing Impact Sensations on Handheld Objects via High-Speed Change of the Rotational Inertia

Several virtual reality (VR) proxies have been developed that can emulate impact sensations by generating actual forces on the hand. Although these proxies contribute to increasing the reality of VR, they still have some limitations, such as high latency, high power consumption, and low frequency to provide impact sensations. To overcome these limitations, we first propose a method to provide an impact sensation without actual force generation by quickly changing the rotational inertia of a handheld proxy while users are swinging it. Then, we developed Unident, a handheld proxy capable of changing its rotational inertia by moving a weight along one axis at a high speed. Two experiments were conducted to evaluate the ability of Unident to provide users with impact sensations. In the first experiment, we demonstrate that Unident can physically provide an impact sensation applied to a handheld object by analyzing the pressure on the user's palm. The second experiment shows that Unident can provide an impact sensation with various magnitudes depending on the amount of rotational inertia to be changed. Finally, we present an application that can be enabled by Unident.