A 2-Axis Optical Force–Torque Fingertip Sensor for Dexterous Grasping Using Linear Polarizers

Abstract

This paper presents a two-axis force/torque sensor (one force and one torque) that uses light-intensity modulation techniques to measure the contact force and torque between a robotic finger and an object. The sensor has a diameter of 9 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> m and a height of 10 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> m. The sensor incorporates linearly aligned fiber-optic cables, linear polarizers, and nitinol wire strips into a rigid structure made of plastic. The nitinol wire strips allow certain parts of the structure to deform under applied forces. A model of the sensor is presented, and calibration experiments were conducted, validating the model. The sensor was also incorporated into the fingertip of a Barrett Hand, and experiments were conducted on three objects, i.e., a power adapter, a partially filled plastic bottle, and a curved paper punch to identify the sensor's response to different surface profiles. The sensor's data are also compared with data from a Nano17 force and torque sensor, and the results from the two sensors are discussed.