Multidimensional Force Illusion using Asymmetric Vibrations

Haptic devices simulate a "sense of touch" to enhance realism and provide an immersive experience in various applications like tactile displays, neurorehabilitation, and enabling vibratory feedback in cellular devices. In addition, haptics has found significance in pedestrian guide systems, allowing users to identify directions without the need for visual displays. Haptic technologies are also implemented in virtual and augmented reality devices to provide improved user experiences. While there are several techniques to create kinesthetic and tactile haptic feedback, creating multidimensional force feedback with a portable form factor has been a challenge due to the difficulty of generating forces without requiring it to be offset by clamping devices to high walls, floors, etc. in the environment.

This work introduces a novel method of creating multidimensional force feedback without grounding by using asymmetric vibrations, which utilizes the nonlinear characteristics of human perception to create the illusion of virtual force. This eliminates the need for large actuators creating actual forces and enables miniaturization with the use of small voice coil actuators, making it easier for a user to carry and use at any place. They enable the development of ungrounded haptic devices that are portable creating opportunities for mobile use cases that can be embedded in various applications. In this work, a handheld prototype that provides 2D haptic feedback was designed and implemented using a unique actuation mechanism with a single voice coil actuator to generate virtual force in eight directions using asymmetric vibrations. Our user study indicates that this device is capable of generating distinct 2D force feedback in eight directions. Users were able to distinguish directional cues over 37% of the time and over 66% of the time when one interval errors are regarded as correct responses. Furthermore, we demonstrate the feasibility of using asymmetric vibration with a spherical prototype that can be held in any orientation in hand to provide 3D haptic feedback. A pilot study with the prototype device showed promising results with a correctness percentage of 83.75% among six directions.