A Tactile Sensing Concept for 3-D Displacement and 3-D Force Measurement Using Light Angle and Intensity Sensing

This article proposes an optical-based tactile sensor design concept, which uses a light angle and intensity sensor to infer force and displacement from deformations of a silicone pillar. The proposed design uses a simple, low-cost fabrication method with an overall small-scale form factor. The sensor can measure 3-D displacement, 3-D force, and vibration. The overall displacement estimation error [mean ± standard deviation (SD)] in the
${X}$
-,
${Y}$
-, and
${Z}$
-axes was
$-10.8\,\,\pm $
52.1, 15.4 ± 66.5, and 1.8
$\pm 17.6 \mu \text{m}$
, respectively, over a full-scale lateral displacement of 1-mm radius in
${X}$
and
${Y}$
and 2.2-mm compression in
${Z}$
. The overall force estimation error (mean ± SD) was
$-8.5\,\,\pm $
47.6,
$-8.5\,\,\pm $
49.0, and
$-28.0\,\,\pm $
92.6 mN for a full-scale force of approximately 2 N in
${X}$
or
${Y}$
, and 6 N in
${Z}$
. Sensitivity to vibrations in the range of 10–950 Hz was also evaluated showing good sensitivity over this entire range. This new sensing approach could be of benefit in robotic manipulation applications, as it could be easily arrayed and/or integrated into the fingers of a robotic gripper to sense slip events and measure load and grip forces and torques.