Three-Dimensional Force Sensor Based on Fiber Bragg Grating for Medical Puncture Robot

In medical puncture robots, visible light, infrared and ultrasound images are currently used to guide punctures. The lack of information about the interaction forces between the puncture needle and soft tissue in different directions during the puncture process can easily lead to soft tissue being damaged. The current three-dimensional force sensors are large and can only be mounted on the base of the puncture needle, which does not allow for easy integration. Moreover, the force transfer to the base introduces various disturbing forces and the measurement accuracy is low. To reduce the risk of soft tissue being damaged and to enhance the intelligent control strategy of the puncture robot, this paper designs a three-dimensional force sensor based on fiber Bragg gratings. The sensor is very small and can be integrated into the back end of the puncture needle to accurately measure the interaction forces between the puncture needle and the soft tissue in different directions. The puncture needle wall is designed with notched bending of a multilayer continuous beam, which can increase the sensitivity of axial stiffness, while maintaining the sensitivity of the sensor to lateral bending and torsion, and also reduce the crosstalk between the axial and lateral forces. The finite element method is used to optimize its structural parameters, and a BP neural network based on the global optimal fitness function is proposed to solve the decoupling problem between the three-dimensional forces, which effectively improves the detection accuracy of the force sensor. The experimental results show that the measurement error of the sensor is less than 1.5%, which can accurately measure the interaction force between the puncture needle and the soft tissue and improve the safety of the puncture process.