A Two-Dimensional Deflection Sensor Based on Force Sensing Resistors

A flexible deflection sensor for elastic shaft with the capability of measuring the amplitude and direction of bending is introduced in this paper. A thin force sensing resistors (FSR) film is taken as its basic material, which is sandwiched by an elastomer layer and a printed circuit board (PCB) with detecting electrode grids. Two fix rings are used to fix the three thin components perpendicularly to the longitudinal direction of the flexible shaft. When the shaft bends under forces, the fix rings will generate a normal pressure on FSR, which will cause the change of the resistance. Therefore, the amplitude of bending can be got based on the value of resistance. The electrode grid on the PCB is divided into four detection areas used to estimate the distribution of normal pressure on the FSR; thus the bending direction of shaft can also be obtained. Test results of a prototype (140 mm in length) show that the amplitude of deflection can reach 30 mm and the sensitivities of sensor are 40.37, 32.8, 37.77, and 39.47 mV/mm in the four directions, respectively. The proposed flexible deflection sensor can be applied in continuum robots or other applications, which require rapid measurement of bending amplitude and direction.