Spatiotemporal modulation for mid-air haptic feedback from an ultrasonic phased array

Abstract

<!--StartFragment-->A tactile sensation can be experienced by focusing airborne ultrasound using a phased array. Nonlinear acoustic pressure alone is difficult to perceive so traditional methods use amplitude modulation in the range of 10–300 Hz to stimulate nerves on the hand most sensitive to those frequencies. We demonstrate that through rapid translation of focus points similar results can be obtained using spatiotemporal modulation. This allows for volumetric sensations to be created using maximum power possible from the array. This is made possible through a solving approach using a pseudo-inverse of the activation matrix followed by a power iteration eigenvalue solution. Advantages versus amplitude modulation and consequences for parametric audio will be discussed.<!--EndFragment-->

Mid-Air Haptic Rendering of 2D Geometric Shapes With a Dynamic Tactile Pointer

“…The method of rendering static and dynamic haptic shapes differ both perceptually and in the way that they are generated. The static stimuli employed spatio-temporal modulation (STM) [33], where a single focus of constant amplitude (intensity = 1) is rapidly moved round the shape perimeter. The rotation frequency causes the human skin to vibrate at the same frequency (and its harmonics [34]) along the entire path trajectory, resulting in the perception of a static tactile sensation, analogous to pressing a cookie cutter against the palm.…”

Investigating the Recognition of Local Shapes Using Mid-air Ultrasound Haptics

“…In fact, a certain number of acoustic radiation pressure oscillation periods is required at a given position and intensity for the user to perceive the haptic stimulus. Spatiotemporal modulation (STM) was introduced by Kappus and Long [16] to address this limitation. In STM, focal points are generated with a fixed frequency (usually the maximum achievable by the device, i.e., 40kHz).…”

PUMAH: Pan-Tilt Ultrasound Mid-Air Haptics for Larger Interaction Workspace in Virtual Reality

“…During the time the cone is displayed, the array attempted to render a small circle (diameter 2cm) centred on the mid-point of the cone vertical axis and in a plane parallel to the array. The circle was rendered using spatiotemporal modulation [19] at a drawing frequency of 100Hz and maximum intensity. Once subjects swiped through the cone, it disappeared and was replaced with a question asking the subjects how strongly they felt tactile feedback at the target, if at all.…”