Providing robotic fingers with tactile sensation can enable better performance of dexterous manipulation. Identifying a texture by touch can further the ability of grippers to adjust their grip to the object being contacted. This work presents a non-camera-based optical tactile sensor array capable of discriminating between textures. The texture discrimination method uses sensor waveform amplitude, morphological, and spectral features. We show that an array of sensing units helps achieve high classification accuracy. Using the phase difference between sensing unit signals as a feature allows for good classification regardless of the scanning speed.

This paper 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 3D displacement, 3D force, and vibration. The overall displacement estimation error (mean ± SD) in the X, Y, and Z axes was 40.2 µm ± 34.8 µm, 4.0 µm ± 55.3 µm and 13.3 µm ± 11.8 µm, 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 38.3 ± 29.6 mN, 40.1 ± 29.4 mN and 0.074 ±61.9 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.