Development Of A Soft Robotic System For Minimally Invasive Cardiac Surgery

At present, China, which has a huge population, is entering an aging society. With thedeterioration of environment and the fast pace of modern life, the disease’s threat isgrowing and medical resources are getting more strained than ever. Against thisbackground, minimally invasive surgery platforms begin to get people’s attention. Just asits name implies, minimally invasive surgery is a new surgical technique that the doctorsuse micro surgical tools to reach specific location in patient’s body for operations justthrough some minimal wounds. Compared with the traditional surgery it has theadvantages of little trauma, less pain, quick recovery and short time in hospital.However, new technology also has its deficiency, and defects of the minimallyinvasive surgery are gradually exposed with the increase of patients. At present, theexisting tool is difficult to handle and the operation relies on doctor’s experience.Furthermore, surgical instruments are now all rigid structures, which always make thepatients feel uncomfortable and the security can not get guaranteed. To solve the aboveproblems, this thesis will focus on the development of a soft minimally invasive surgeryrobotic system for cardiac ablation.The main contents are summarized as follows.The environment of human’s heart is very special and the traditional rigid robotscannot satisfy the requirement of security. So this thesis first introduces several classicsurgical robots and soft robots, analyzing the advantages and disadvantages of each. Then,through combing the key technologies of surgery robot and existing insufficiency, hugeadvantages of soft surgery robots in security and flexibility are highlighted. On the otherhand we also point out that the actual clinical application may meet with many difficultiesin the modeling and control.Then the thesis introduces the system design. The main body, made of soft siliconematerial, is non-toxic, and will not react with human body’s tissues. By reference to thetrunk’s physiological structure, the main body is embedded with several cables in differentpositions inside, and in the center there are ablation tools and a micro camera. The bottomconnects to the feeding station which mainly provides driving force for the whole system,including the upper and underlying systems. The upper system contains eight steeringgears and a rotating movement system. The underlying system mainly consists of a linear motion system.Robot’s control system also can be divided into two parts, the upper computer and thebottom control panel. The upper one mainly receives operation instructions and feedbackinformations, which can be displayed on the human-computer interaction interface. Uppersystem will send motor commands to the bottom board according to the instructions, andthe bottom board will distribute them according to the communication protocols. Also weintroduce two operating modes: manual mode and automatic mode. Manual mode issimilar to the operation mode of traditional platforms, but the workload is huge. Automaticmode is mainly designed to reduce the workload.As the model is very important for robot system control in the automatic mode, thisthesis briefly analyzes the modeling of soft surgical robot and combes several keyproblems. There is no systematic modeling theory for soft robot currently and thetraditional method is not suitable to the robot that has no support structures, as theinfluences of gravity and environment are always ignored. From the perspective of controlwithout model, this thesis has explored a new method by analyzing the behavior of softanimals, especially the octopus tentacles and trunks. We define several basic movements ofour robot and design a few behaviors to complete some simple tasks. Through theexperiments it is proved that the control strategy is practical.At last, a large number of experiments are carried out to prove the the flexibility andcontrollability of our system and the control modes. It can be concluded that this systemhas a good performance in the crowded environment and is able to reach the target pointthrough manual and automatic modes. For the disturbance of heart beating, in addition tothe material characteristics, the soft robotic system can also compensate it by active control.Further more these experiments show that soft robots have a better balance between safetyand control which means a better prospect in the clinical application.As the research time and resources are limited, the main work is focused on systemdevelopment, the modeling method and the control strategy have not been researchedin-depth. Along with the project, it is believed that this soft surgical robotic system canmake greater achievements in the field of minimally invasive cardiac surgery.