  Acoustic Soft Tactile (AST) skin is a novel sensing technology which derives
tactile information from the modulation of acoustic waves travelling through
the skin's embedded acoustic channels. A generalisable data-driven calibration
model maps the acoustic modulations to the corresponding tactile information in
the form of contact forces with their contact locations and contact geometries.
AST skin technology has been highlighted for its easy customisation. As a case
study, this paper discusses the possibility of using AST skin on a custom-built
robotic end effector finger for strawberry handling. The paper delves into the
design, prototyping, and calibration method to sensorise the end effector
finger with AST skin. A real-time force-controlled gripping experiment is
conducted with the sensorised finger to handle strawberries by their peduncle.
The finger could successfully grip the strawberry peduncle by maintaining a
preset force of 2 N with a maximum Mean Absolute Error (MAE) of 0.31 N over
multiple peduncle diameters and strawberry weight classes. Moreover, this study
sets confidence in the usability of AST skin in generating real-time tactile
feedback for robot manipulation tasks.
