Development of a High-Sensitivity Proximal Force/Torque Sensor Based on Optical Sensing for Intravascular Robots

This work proposes a proximal force/torque sensor with high sensitivity, adjustable measurement range, and decoupled force and torque detection for intravascular robots. The proposed sensor design primary consists of a force/torque-sensitive flexure that comprises a series of ortho-planar springs and an annulus cross-beam structure, an optical sensing unit with wireless communication. The ortho-planar component demonstrates equivalent functions as a parallel mechanism and achieves an outstanding linear force-displacement relationship along its axial direction. The rotational cross-beam structure has been parallelly arranged to form the torque-sensing component and enhanced sensing range. The utilized optical sensing unit can precisely detect the linear and angular displacement from the sensitive flexure based on a series of coherent CMOS images and support simultaneous detection and decoupling of force and torque. The FEM simulation has been performed for structure design and performance investigation. The prototyped sensor achieved a high force resolution of 8.7 mN within [−2.5, 2.5 N] and 0.13 $\text{N}\cdot $ mm within [−60, 60 $\text{N}\cdot $ mm] for torque, with the corresponding linearity error values of 1.43% and 1.95%. The average crosstalk error values are 0.32% for force detection and 2.8% for torque measurement, indicating excellent anti-interference performance. To investigate the practicability of the proposed sensor, the phantom experiment has been conducted to evaluate its effectiveness for intravascular catheterization.