A Compact FBG-Based Triaxial Force Sensor With Parallel Helical Beams for Robotic-Assisted Surgery

Force sensing is important for surgical robotics in order to realize surgical palpation and ensure surgical safety. In this article, we design a compact triaxial force sensor based on fiber Bragg gratings (FBGs). The force sensor is composed of an elastic structure, two supporting disks, and four fibers. To achieve a good balance between the axial resolution and radial resolution, the elastic structure has parallel helical beams and the structure parameters of the sensor are optimized. The mechanical model of the sensor is proposed and the influence of temperature is also considered. The force sensor has the advantages of compact structure, easy assembly, and good scalability. An experimental setup is used to calibrate and evaluate the force sensor. The performance of the force sensor under dynamic force with different frequencies is also evaluated. The resolutions for the axial force and radial force are, respectively, 0.01 and 0.012 N with a range of 0–5 N. In addition, the sensor is fixed on a robot arm to further evaluate its palpation ability. The experimental results show that the sensor can recognize different materials with different stiffnesses and the position of the rigid body in a silica model can also be determined.