Transducer preselection in ultrasonic phased array to form multiple foci on a non-planar surface

In this study, we propose a method to preselect transducers for tactile presentation using airborne ultrasonic phased arrays. Conventional methods for forming an ultrasonic focal point on a non-planar surface determine the driving signal for the transducer without considering the orientation of the surface, resulting in a weakening of the pressure generated at the desired surface. In the proposed method, only transducers that contribute to focus formation are enabled based on the normal direction of the surface. This transducer preselection method allows each transducer to be used efficiently to generate strong pressure at multiple points in different normal directions. We conducted numerical simulations to confirm that the proposed method contributed to a pressure increase on a mesh model of fingers.