Modeling of transmission characteristics of tendon sheath system for enhanced performance

• Main Author: Sun, Zhenglong.
• Other Authors: Phee Soo Jay, Louis
• Format: Theses and Dissertations
• Language: English
• Published: 2014
• Subjects: DRNTU::Engineering::Mechanical engineering::Control engineering; DRNTU::Engineering::Mechanical engineering; DRNTU::Engineering::Mechanical engineering::Mechatronics
• Online Access: http://hdl.handle.net/10356/55284
• Institution: Nanyang Technological University

With the growing capabilities in therapeutic endoscopy, endoscopic surgery is becoming a future trend in minimally invasive surgery. It allows the surgeon to perform intra-abdominal surgical procedures that used to require open surgery or laparoscopic surgery in an even less-invasive way; but it is more technical demanding to design and control the surgical instruments endoscopically through a long and winding transmission route. Recent studies have shown that the tendon-sheath mechanism could be an ideal candidate for endoscopic surgery, since it is promising in delivering high power through a compliant and flexible route, while maintaining the size of the end-effectors to be compact and lightweight. However, due to the spatial constraints, it is extremely difficult to integrate any force or position sensors at the tip of the robotic end-effectors. Without sensory feedback, only open loop control is applicable. As a result, due to the flexibility of the transmission route and tendon compliance the system suffers from lacking of direct haptic feedback and inaccurate position control. In this thesis, in order to address these problems, the author presents a system modeling approach on the tendon-sheath mechanism. By modeling the transmission characteristics of the flexible tendon-sheath system with arbitrary configurations, it is proposed to estimate the tool-tissue interaction force and position errors at the distal end by measuring the force and position information at the proximal end. Two generic models have been proposed on the tension transmission and tendon elongation respectively. Discussions have been made on the effects of the flexible route configuration on the transmission characteristics. All models and propositions were validated by experiments on a dedicated platform. Based on the derived models, performance of the proposed system modeling was examined by a single-DoF master-slave system actuated by an antagonistic pair of tendon-sheaths. It is shown that the proposed system modeling approach is capable of delivering improvement with haptic feedback and enhanced position control.