A force sensing structure with orthogonal optical fiber loops for robot fingers

Abstract The force sensing is of great importance to robot fingers. In this paper we proposed a novel force sensing structure only composed of an elastic ring and dual orthogonal fiber loops, where the external force was detected by using the differential-variation relationship between macro-bending losses of two orthogonal optical fiber loops. A sensing model was established to elucidate the sensing mechanism, and numerical calculations and associated experiments were implemented to test the performance of the proposed structure. The experimental results show that the proposed sensing structure has a good linear response to the external force ranging from 0 to 2.60 N for compression and from 0 to 2.40 N for tension. The overall sensitivity of 15.598 dB/N, i.e., the resolution of approximately 0.2 dB per 0.01 N, was achieved. By comparison with the existing optical-based force sensing structures, the proposed force sensing structure is lower-cost and can be fabricated more easily but more precisely. Furthermore, we further explored its applications for contact detection, grasping and manipulation, and some special occasions with strong electromagnetic interference, high temperature and humidity, demonstrating its greatly promising prospects in robot fingers.