  Tactile sensors, which provide information about the physical properties of
objects, are an essential component of robotic systems. The visuotactile
sensing technology with the merits of high resolution and low cost has
facilitated the development of robotics from environment exploration to
dexterous operation. Over the years, several reviews on visuotactile sensors
for robots have been presented, but few of them discussed the significance of
signal processing methods to visuotactile sensors. Apart from ingenious
hardware design, the full potential of the sensory system toward designated
tasks can only be released with the appropriate signal processing methods.
Therefore, this paper provides a comprehensive review of visuotactile sensors
from the perspective of signal processing methods and outlooks possible future
research directions for visuotactile sensors.
