Smooth vibrotactile flow generation using two piezoelectric actuators

This paper proposes a method for generating a smooth directional vibrotactile flow on a thin plate. While actuating two piezoelectric actuators spatially across the plate, temporal sweeping of the input excitation frequency from zero to the first mode of the resonance frequency can smooth the perceived directional vibrotactile flow, as compared to a vibrotactile flow generated by conventional apparent tactile movement and phantom sensation methods. In order to ascertain important factors in the excitation pattern, a user study was conducted for three factors (amplitude (constant versus modulated), frequency (constant versus swept), and ending shape (sharp versus smooth)). The results showed that frequency sweeping in addition to amplitude modulation and smooth ending were the most important factors in smoothing vibrotactile flows. Moreover, an excitation signal with a smooth ending shape was important for generating nonspiky flows at the midpoint. In this study, a vibration isolation design is also proposed in order to substantially decrease the transmission of the actuator vibration to the mockup housing. As such, it is expected that the proposed vibrotactile flow generation method and vibration isolation design may be useful in applications including generating directional information in navigation maps or for identifying callers in mobile devices.