Research on high-sensitivity joint bending angle and direction detection sensor based on multi-fiber end-face coupling

Abstract

In the fields of biomedical engineering and intelligent sensing, accurate detection of joint flexion angles and directions holds significant application value. A bending angle detection scheme based on the coupling of single-fiber and multi-fiber within a tube is proposed to achieve simultaneous detection of bending angle and direction. The experimental results show that the output optical power of the optical fiber changes with the bending of the tube, and there is still optical output at the bend angle of 180°. Additionally, the output optical power of the output fiber is correlated with the bending direction, with lower optical loss observed for the output fiber located at the -x direction of the fiber core center. Therefore, the bending direction of the tube can be determined by comparing the output optical loss between fibers. On the other hand, the bending angle can be obtained from the total loss of all output fibers. Experimental results indicate that the sensor possesses high sensitivity of up to 0.181dB/° for the angle range from 0° to 180°, and a linear regression coefficient R² of 0.993. Additionally, experiments conducted with motors and finger joints have demonstrated the excellent reversibility and rapid response capabilities of the proposed angular sensor, thereby indicating its potential as an effective solution for precise monitoring of joint movements.