Curvature and force measurement of soft manipulator based on stretchable helical optic fibre

Abstract

Abstract The soft surgical manipulator is a scientific frontier in the fields of minimally invasive surgery and robotics, and it is crucial for improving the performance of surgery. However, owing to its narrow and confined environment in minimally invasive surgeries, some existing methods have not solved its problem of accurate measurement, which limits its application. This paper demonstrates the curvature and force measurement of a hyper-elastic soft manipulator with helically embedded stretchable fibre Bragg grating (FBG)-based fibre optic sensor. Unlike a straight FBG embedding configuration, this unique helical configuration prevents sensor dislocation, supports stretchability, and facilitates the detection of various movements of the soft manipulator. First, the design of the soft manipulator embedded with a stretchable helical optic fibre is described. Second, the sensing theory of the soft manipulator was analysed, and the stretchable helical FBG sensing model was established. Finally, to verify the effectiveness of this design and sensing technique based on the stretchable helical optic fibre, some compression and bending experiments of the soft manipulator were conducted. The results showed that the errors between theoretical and experimental measurements are less than 5%, and the helical structure enables 10% of compression in length, thus facilitating in the measurement of tension and bending curvature of the soft manipulator.