A Hollow FBG-Based 3-Axis Force Sensor for Surgical Robots

The ability to perceive forces is crucial for surgical robots to perform operations safely and achieve effective treatment. This paper presents the design of a hollow force sensor based on fiber Bragg gratings (FBGs) to detect 3-Axis forces between the instrument and tissue. The sensor, consisting of an elastic body and four optical fibers with FBGs, is designed for convenient integration into instruments. Unlike most previous force sensors proposed by researchers, which fail to balance sensitivity across axes and have a hollow structure, the sensor designed in this paper positions the optical fibers away from the center to reserve sufficient space for the instrument channel. Additionally, the proposed elastic body comprises both an outer tube of flexible deformable beams and inner support pillars that enhance radial stiffness. This design ensures sensitivity along the axis while increasing stiffness against bending deformation radially. Furthermore, the force sensor is manufactured using 3D printing, making assembly simple and enabling easy interchangeability of instrument tips for various surgical instruments. Finite element simulations and experiments were conducted to verify the sensor’s excellent linearity. The measurement range for each axis extends from 0 to 4 N. The axial resolution is 6 mN, while the radial resolution is 3.1 mN. At last, temperature compensation was implemented for the sensor environment to mitigate temperature-induced interference, ensuring precise measurements of three-Axis forces. The sensor is expected to be integrated into surgical robots to ensure surgical safety and enhance surgical quality.