Carbon nanotube/glycerol embedded low cost flexible sensor for large deflection sensing of continuum manipulators

Large deflection sensing is highly crucial for proper positioning and control of continuum robots during robot assisted minimally invasive surgery. Existing techniques suffer from eletromagnetic noise susceptibility, harmful radiation exposure, limited range, bio-incompatibility and necessity of expensive instruments. In the present study, we propose a Multi-Walled Carbon Nano-Tube (MWCNT)/polyglycerol based low cost, flexible and biocompatible sensor which could allow safer, faster and accurate angular deflection measurement of continuum robots for biomedical applications. Experimental results demonstrate that the sensor is stretchable upto 100% , provides a gauge factor upto 11.65, have response time around 8 ms, durability of -0.14% for cyclic loading and unloading and show very small creep upto ±0.0008 ( ±2.88%). Furthermore, the sensor can measure continuum robot deflection upto ±150 o with a sensitivity of 666.67 ohms/degree, with a maximum error of 1.67% and maximum hysteresis of 1.41%. Thus, wide range, low cost, fast response, and biocompatibility justify the potential of the proposed sensor for large deflection sensing of continuum robots during robot assisted minimally invasive surgery.

Variable Curvature Modelling Method of Continuum Robots with Contraints

The inherent compliance of continuum robots holds great promise in the fields of soft manipulation and safe human-robot interaction. This compliance reduces the risk of damage to the manipulated object and the surroundings. However, continuum robots have theoretically infinite degrees of freedom, and this high flexibility usually leads to complex deformations with external forces and positional constraints. How to describe this complex deformation is the main challenge for modelling continuum robots. In this study, we investigated a novel variable curvature modeling method for continuum robots, considering external forces and positional constraints. The robot configuration curve is described by the developed mechanics model, and then the robot is fitted to the curve. To validate the model, a 10-section continuum robot prototype with a length of 1 m was developed. The ability of the robot to reach the target points and track complex trajectories with load verified the feasibility and accuracy of the model. The ratio of the average position error of the robot endpoint to the robot length was less than 2.38%. This work may serve a new perspective for design analysis and motion control of continuum robots.

From Theoretical Work to Clinical Translation: Progress in Concentric Tube Robots

Continuum robots can traverse anatomical pathways to intervene in regions deep inside the human body. They are able to steer along 3D curves in confined spaces and dexterously handle tissues. Concentric tube robots (CTRs) are continuum robots that comprise a series of precurved elastic tubes that can be translated and rotated with respect to each other to control the shape of the robot and tip pose. CTRs are a rapidly maturing technology that has seen extensive research over the past decade. Today, they are being evaluated as tools for a variety of surgical applications, as they can offer precision and manipulability in tight workspaces. This review provides an exhaustive classification of research on CTRs based on their clinical applications and highlights approaches for modeling, control, design, and sensing. Competing approaches are critically presented, leading to a discussion of future directions to address the limitations of current research and its translation to clinical applications. Expected final online publication date for the Annual Review of Control, Robotics, and Autonomous Systems, Volume 5 is May 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.