Multimode Proximal Force FBG-Based Sensors With High-Resolution for Catheter Surgical Robots

Proximal force signals are widely used benefiting from the advantage of easy collection and are critical for enhancing the safety of the catheter surgical robot. This article presented two kinds of 3-D printable fiber Bragg grating (FBG)-based sensors for clamping force and axial force sensing. The clamping force sensor can realize the clamping-sensing function integration based on a 45. inclined rod and an arc hinge, while the axial force sensor adopts two symmetrical lamina emergent torsional (LET) joints to enhance the sensitivity and hysteresis characteristic. A data and theoretical model-driven method has been proposed to derive sensitivity models of sensors, and the relative errors compared with the experimental sensitivities are all within 10%. The calibration experiment results demonstrate that the designed sensor has obvious benefits in resolution (<2.5 mN) and sensitivity (>480 pm/N) compared with other similar sensors. In addition, dynamic and durability experiments have been implemented to validate the reliability of the designed sensors. To achieve direct measurement of proximal force and reduce the influence of parasitic movement, the integration mode of two sensors is also carefully considered. A wireless technology-based primary-secondary control system and a fuzzy proportional-integral-derivative (PID) control strategy with overshoot compensation have been constructed, leading to the achievement of automatic adjustment of catheter movement and clamping force. Furthermore, several in vitro experiments have been implemented to verify the vascular protection, primary-secondary hand switching, and grading force control functions of the system. Such merits indicate that the designed proximal force sensors have huge potential in the field of catheter surgical robots.