AUTD3: Scalable Airborne Ultrasound Tactile Display

Through nonlinear effects, airborne ultrasound phased arrays enable mid-air tactile presentations, as well as auditory presentation and acoustic levitation. To create workplaces flexibly, we have developed a scalable phased array system in which multiple modules can be connected via Ethernet cables and controlled from a PC or other host device. Each module has 249 transducers and the software used can individually specify the phase and amplitude of each of the connected transducers. Using EtherCAT for communication, the system achieves high accuracy synchronization among the connected modules. In this article, we describe the details of the hardware and software architecture of the developed system and evaluate it. We experimentally confirmed the synchronization of 20 modules within an accuracy of
$0.1~\mathrm{{\mu }s}$
and the phase and amplitude can be specified at
$8~\mathrm{bits}$
resolution. In addition, using nine modules, we confirmed that we could make a focal point of the size consistent with the theory at
$500~\mathrm{mm}$
above the array surface.