Color-Coded Fiber-Optic Tactile Sensor for an Elastomeric Robot Skin

Abstract

The sense of touch is essential for reliable mapping between the environment and a robot which interacts physically with objects. Presumably, an artificial tactile skin would facilitate safe interaction of the robots with the environment. In this work, we present our color-coded tactile sensor, incorporating plastic optical fibers (POF), transparent silicone rubber and an off-the-shelf color camera. Processing electronics are placed away from the sensing surface to make the sensor robust to harsh environments. Contact localization is possible thanks to the lower number of light sources compared to the number of camera POFs. Classical machine learning techniques and a hierarchical classification scheme were used for contact localization. Specifically, we generated the mapping from stimulation to sensation of a robotic perception system using our sensor. We achieved a force sensing range up to 18 N with the force resolution of around 3.6 N and the spatial resolution of 8 mm. The color-coded tactile sensor is suitable for tactile exploration and might enable further innovations in robust tactile sensing.

Tactile Image Sensors Employing Camera: A Review

“…The surface pattern of the contact object is seen through the transparent elastomer, and force is evaluated based on the shape and displacement of the image of the eight conical feet, captured through a light conductive plate. In [92,93], multiple color filters and multiple LEDs with different colors were used, respectively, to obtain the deformation of sensor skin as color changes. In [92], a subtractive color mixing process using yellow and magenta translucent markers placed at different depths in the transparent elastomer body was used to estimate the three-dimensional displacement field.…”

Deep Vibro-Tactile Perception for Simultaneous Texture Identification, Slip Detection, and Speed Estimation

“…Some of the existing methods build upon one dimensional (1D) measurements of FIVs, e.g., using accelerometers embedded in robot fingertips [17,18] and in hand prostheses [19]. Others, rather, indirectly use two dimensional (2D) camera images, e.g., optical sensing [20] embedded in a robot end-effector.…”

ShadowSense

“…The performance of sensors is shown to attain submillimeter accuracy, and the technique shows promise to have real-world applications in tactile perception, manipulation, and exploration. Kappassov et al [18] developed a color-coded optical tactile sensing array, incorporating plastic optical fibers inside silicone rubber. When the skin gets compressed after contact with an object, the scattering pattern of the light in the optical fibers changes, thus allowing for the measurement of force and the localization of the object.…”