Six-Dimensional Force/Torque Sensor Based on Fiber Bragg Gratings with Low Coupling

In this article, we present a fiber Bragg grating (FBG) based 6-D force/torque (F/T) sensor that can be mounted on robot joints for the detection of comprehensive F/T information. The sensor is designed based on a new concept of multilayer measurement in which the elastic structure is divided into four layers. A single optical fiber inscribed with 12 FBGs is symmetrically attached to the elastic structure to sense F/T-induced strains by means of differential measurements. Because of the mechanical decoupling function of the structure and the reasonable arrangement of the FBG sensing elements, the designed sensor possesses a great advantage of low cross coupling compared with the existing 6-D F/T sensors, which simplifies the calibration and maintenance of the sensor. Calibration experiments demonstrate high resolutions of 7.8 N·mm, 7.2 N·mm, 15.8 N·mm, 0.0067 N, 0.0066 N, and 0.0825 N within the range of ±1.56 N·m, ±1.56 N·m, ±1.56 N·m, ±10 N, ±10 N, and ±25 N for the detection of Mx, My, Mz, Fx, Fy , and Fz , respectively. Dynamic performances of the designed sensor have been evaluated in comparison with a commercial F/T sensor.