Design and Control of a Flexible Tube Manipulator for Optical Irradiation of a Superficial Tumor

Abstract

Flexible manipulators have proven their potential in medical applications like minimally invasive surgeries, endoscopies, laparoscopies, colonoscopies, etc. One of the promising areas in medicine where flexible manipulators are required, is cancer treatment through targeted thermal therapy. The treatment method involves irradiation of a targeted superficial tumor in different orientations for prolonged sessions that requires manipulation of a flexible tube-like medical optical fiber bundle by a surgeon. The manual manipulation of the flexible tube makes the treatment process tiring for the surgeon who is accustomed to human error. Thus, an automated solution is required that can actively manipulate the flexible tube around the targeted tumor and thereby, increase the effectiveness of the therapy. This thesis provides the required basis for developing a flexible tube manipulator (FTM) with trajectory control for use in tumor irradiation procedures. To develop the FTM, shape memory alloy (SMA) actuators are selected due to their low weight and size, ease of installation, and excellent biocompatibility. First, the displacement generation capabilities of different SMA actuator configurations like SMA wire-bias spring, antagonistic SMA wires, SMA spring bias spring and antagonistic SMA springs are investigated. In this direction, numerical implementation of SMA wire-bias spring actuator model is independently carried out by three iterative solvers: Newton-Raphson, implicit differential equation solver, and trust-region-dogleg algorithm and through a comparative evaluation, the implicit differential equation solver (IDES) is found as the most suitable solver. Next, the displacement generation capability of a two-way actuator i.e. antagonistic SMA wire actuator is calculated through the mathematical model. The reported results indicate low displacement generation capabilities of SMA wire actuators. As SMA is a path-dependent material, it is important to include the history of traveled paths in the modeling scheme