FW-Touch: A Finger Wearable Haptic Interface with a MR Foam Actuator for Displaying Surface Material Properties on a Touch Screen

The haptic interface plays an increasingly important role in enhancing the realism and immersion of the user's interaction with the touch screen. Inspired by the wearable haptic system, this paper proposes a finger wearable device called FW-Touch for touch screen interaction. The device provides normal force, lateral force, and vibrotactile feedback for the interaction of the finger and the touch screen through three internally integrated actuators. By displaying the hardness, friction, and roughness of a virtual surface, the device is capable of simulating the active exploration and sensing process of the finger on a real surface. This paper describes the design and specifications of the FW-Touch, and details the design process of a magnetorheological (MR) foam actuator that uses a Hall sensor to correct the output force. Through physical measurements and psychophysical experiments, we comprehensively evaluated the force feedback performance of the FW-Touch and its ability in displaying the stiffness and friction of the virtual surface. The results show that improving the accuracy of force feedback is necessary for virtual stiffness display, and the accuracy and effectiveness of the FW-Touch in displaying virtual surface features can be confirmed from the measured stiffness and friction Weber fractions.