Fiber Bragg Grating-Based Triaxial Force Sensor With Parallel Flexure Hinges

During cardiac surgery, the excessive or insufficient contact force between the tip of catheter and heart tissue will lead to the cardiac penetration or noneffective ablative lesion. Usually, the surgeon can only estimate the force at the distal end roughly from their experience by operating the catheter's proximal handle. In this paper, we design a fiber Bragg grating-based triaxial force sensor with parallel flexure hinges to sense the contact force. The proposed mechanism integrated with parallel flexure hinges is capable of achieving an excellent lateral and axial stiffness balance to guarantee the resolution at each direction with the same order of magnitude. The mathematical model is built to design a suitable stiffness configuration and validate the design reasonability. The model-based and model-free methods are adopted to decouple lateral and axial force components. Experimental results demonstrate that the developed 8 French size force sensor can successfully achieve the triaxial force prediction with <1 g resolution using both decoupling methods. And the model-free method can accomplish a higher accuracy with RMS error <1% of full scale of [-100 g, 100 g] along the lateral direction and [0 g, 100 g] along the axial compression direction.