Development of control algorithm for adjusting the needle insertion path during robot assisted breast biopsy procedure

The MURAB project, created and developed by the RAM group at the university of Twente in the Netherlands, aims to improve the precision and the efficiency of the breast biopsy procedure, reducing as much as possible the intervention time and the discomfort for the patient. In this framework, a lot of studies have been conducted concerning efficient control methods capable of positioning the end effector of a KUKA LBR Med robotic arm at the location where the hypothetical lesion has been individualized. Starting from these methods, the main goal of this Thesis is to develop a control algorithm able to modify the robot trajectory such that it can find and reach the lesion position, even in presence of variations of this target location; caused for example by small patient’s motions. After a brief literature review about the already existing robot assisted breast biopsy procedures, an elaborated study relative to the control strategies adopted in the collaboration and interaction between humans and robotic systems has been presented. This leads to the characterization and implementation of the final controller, defined as an impedance controller with energy and power limitations to increase the safety of the patient and energy tanks to ensure passivity. The validity and the stability of this control approach have been analyzed and tested firstly with a 20 sim simulation and then with experiments in laboratory. The results will show how it is possible to compensate rotational and / or translational errors in the robot end effector’s positioning through a suitable tuning of some parameters, while keeping a good image quality of the determined target and without loosing contact between the probe and the breast phantom / skin. Meanwhile, a proper characterization of the controller’s parameters allows to guarantee the compliance of the manipulator, fundamental to ensure the safety of the patient and of the interaction of the robot with the surrounding environment.