IMPLEMENTATION OF TACTILE SENSING VIA CONTROLLABLE SPATIAL RESOLUTION OF A MID-AIR HAPTIC ULTRASONIC ARRAY

초록

This study aims to investigate a controllable focal area by improving an actuation method for a mid-air haptic ultrasound array. While beamforming techniques, particularly the delay-and-sum (DAS) method used in mid-air haptic actuators, have reached a mature stage, there has been limited focus on engineering solutions to control spatial resolution through signal processing. To address this gap, we introduce the Energy Difference Maximization (EDM) method to dynamically control the effective focal area in a 40 kHz mid-air haptic system. The EDM method adjusts the amplitudes and phases of individual ultrasonic elements based on the target location and focal area. By manipulating the control window size and weight factor, the EDM method suppresses the acoustic pressure in off-target areas, enhancing precision. The approach was validated through both acoustic numerical models and physical experiments. Using an in-house 8x8 rectilinear array, the focal area was adjustable within a +/- 21% range, while maintaining a stable maximum pressure output (within +/- 0.5 dB). At the -6 dB focal area, the acoustic pressure exceeded 145 dB, sufficient to trigger tactile sensations.

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