High-Precision Hollow Triaxial Force Sensor for Cannulation in Minimally Invasive Surgery

Cannulation is a common procedure in minimally invasive surgery. Force sensing during this procedure is essential for its safety and effectiveness. Achieving high-precision force sensing remains challenging due to the dimensional constraints of catheters and the need for hollow channels. This study presents a hollow triaxial force sensor based on fiber Bragg gratings, featuring a double-layer beam configuration that achieves both compact size and balanced stiffness. We develop an evolutionary design process of the sensor using the Freedom and Constraint Topology method. We also establish a mechanical model of the sensor, and optimize structural parameters through the condition number of the mapping matrix to suppress error amplification. In addition, we propose an improved tree Parzen estimator optimized random forest algorithm, integrated with temperature compensation, to enhance the precision of triaxial force sensing. The sensor achieves root mean square errors of 0.0214 and 0.0225 N for radial force components$F_{x}$and$F_{y}$with measurement ranges of$\pm$2N, and 0.0170N for axial force component$F_{z}$with measurement range of 0–2N. An ex vivo tissue experiment validates that the sensor effectively detects dynamic force variations and facilitates compliant operation with surgical instruments in a porcine duodenal papilla.