This paper presents a three-dimensional (3-D) force sensor based on fiber Bragg grating (FBG) for robot plantar force measuring. A classical Maltese-cross beam with multiplexed FBGs has been designed for 3-D force sensing. Strain distribution characteristics and dynamic performance of the Maltese-cross elastomer have been investigated by using finite element analysis. Through ingenious design, 3-D forces of Fx, Fy, and Fz have been measured by only five sensitive elements of FBG, meanwhile, decoupling and temperature compensation have also been realized, which greatly reduces the number of sensitive element compared with the traditional resistance strain gauge based multi-axis force sensor. Comprehensive performance test has been carried out, and the experimental results demonstrate that the sensor possesses good linearity, weak coupling, and creep resistance.

This paper presents a fiber Bragg grating (FBG)-based six-dimensional (6-D) force/torque (F/T) sensor that can be mounted on robot joints for the detection of comprehensive force/torque 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 force/torque-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 existing 6-D force/torque 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 Nm, ±1.56 Nm, ±1.56 Nm, ±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 force/torque sensor.

Fiber Bragg grating (FBG) based accelerometer technology receives much attention from various research communities. In this paper, we investigated a FBG accelerometer with high resonant frequency for mechanical equipment. A special steel tube-mass block elastic structure with two FBGs embedded has been designed for axial vibration sensing. The steel tube was fixed on the mass block and threaded pipe in the sensor by sintering and pre-stretched to serve as a spring element. Then, a sensor prototype has been manufactured and fully tested. Experimental results show that the sensor provides a high resonant frequency of 3806 Hz with a wide flat response region up to 1200 Hz, which is consistent with the theoretical value of 3993 Hz. The sensitivity of the sensor is 4.01 pm/g with a fitting linear correlation coefficient of 0.9997. Temperature change test and excitation test along the working direction and transverse direction have been carried out, which confirmed excellent anti-interference ability and temperature compensation ability of the sensor.