  This paper aims to present an innovative and cost-effective design for
Acoustic Soft Tactile (AST) Skin, with the primary goal of significantly
enhancing the accuracy of 2-D tactile feature estimation. The existing
challenge lies in achieving precise tactile feature estimation, especially
concerning contact geometry characteristics, using cost-effective solutions. We
hypothesise that by harnessing acoustic energy through dedicated acoustic
channels in 2 layers beneath the sensing surface and analysing amplitude
modulation, we can effectively decode interactions on the sensory surface,
thereby improving tactile feature estimation. Our approach involves the
distinct separation of hardware components responsible for emitting and
receiving acoustic signals, resulting in a modular and highly customizable skin
design. Practical tests demonstrate the effectiveness of this novel design,
achieving remarkable precision in estimating contact normal forces (MAE < 0.8
N), 2D contact localisation (MAE < 0.7 mm), and contact surface diameter (MAE <
0.3 mm). In conclusion, the AST skin, with its innovative design and modular
architecture, successfully addresses the challenge of tactile feature
estimation. The presented results showcase its ability to precisely estimate
various tactile features, making it a practical and cost-effective solution for
robotic applications.
