Fibre Bragg Grating (FBG)-based force and pose sensing for endoscopic robotic systems

• Main Author: Lai, Wenjie
• Other Authors: Phee Soo Jay, Louis
• Format: Thesis-Doctor of Philosophy
• Language: English
• Published: Nanyang Technological University 2021
• Subjects: Engineering::Mechanical engineering::Surgical assistive technology; Engineering::Mechanical engineering::Robots
• Online Access: https://hdl.handle.net/10356/150542
• Institution: Nanyang Technological University

Haptic feedback and motion tracking are still absent in the Robotic Minimally Invasive Surgery (RMIS). The non-transparency between the master-slave system affects the surgeon's situation awareness and safety assessment during an operation. Therefore, there is a demand for developing miniature sensors to detect the tool-tissue interaction in surgical robotics. Due to tighter space constraints in the flexible endoscopic robot, it becomes much more challenging to advance sensors in such a robotic system. The research aims to develop novel and practical solutions to realize force sensing and pose sensing for flexible endoscopic surgical robots. A single-axis force sensor (two versions), an integrated sensor-model approach, a three -axial force sensor have been proposed to capture the distal force in an endoscopic surgical robot driven by Tendon-Sheath Mechanisms (TSMs). The single-axis force sensor was integrated with the actuation mechanism, measuring the distal tension force in real-time, with a sensitivity of 34.14 pm/N. The integrated sensor-model approach has been validated in a 5-DoF (Degree of Freedom) grasper in both in-vitro tests and an animal study (in a live porcine). This approach saves cost and space while maintaining the robustness of the sensing system. Another three-axial force sensor has been further explored to reflect the tool-tissue interaction forces, with a lateral force sensitivity up to 1757.438 pm/N. Validation tests have been conducted to show its measurement capability of pulling force (0 N to 6 N), steering force (-3.5 N to 3 N), and lifting force (-4.5 N to 4.5 N). Besides, real-time forces have been displayed on the surgeon's hand through the haptic device, Omega7. In addition, a rotation angle sensor (RAS) has been developed to detect a pivot joint's rotation angle in the articulated surgical grasper, with a broad measurable range of angles [-47.8°, 39.1°] and a small bending radius down to 6.9 mm. Apart from flexible endoscopic robots, the single-axis force sensor and the integrated sensor-model approach can also be applied in TSM-driven or tendon-driven robotic fingers/hands, wearable devices, surgical catheters, and rehabilitation devices. The three-axial force sensor can also be shifted to a laparoscopic robot or a catheter, not limited to the flexible endoscopic surgical robot. The RAS can also be used in continuum robots or soft robots to detect the large bending deflection.