DESIGN AND CONTROL OF A ROBOTIC SYSTEM TO ASSIST WITH MRI-GUIDED INTERVENTIONS
Development of medical robots to assist with surgical operations has become an area of significant research interest for the past two decades. These robots are employed in a wide range of applications from prostate needle placement and kidney transplant to brain surgery and artery bypass. As new technologies are introduced and the development of more sophisticated and integrated robotic systems is made possible, more challenging operations are targeted to be enhanced using automated mechanisms. Magnetic Resonance Imaging MRI-guided intracardiac intervention under beating-heart conditions is one of such sophisticated operations, which has attracted lots of attention recently. This dissertation focuses on the design, fabrication and control of an integrated robotic system that is aimed to assist with one specific procedure in this family-aortic valve implantation. One of the challenges involved in cardiac interventions under beating-heart conditions is the disturbances generated by the blood flow patterns inside the heart. To address this issue, an analytic model is generated to predict the flow disturbance generated from the interaction between the blood flow and the surgical tool in the aortic valve replacement procedure. The obtained model of external forces along with other design requirements initiate the development of a parallel structure platform to serve as a slave robot in the master-slave robotic configuration. Benefiting from the features of parallel mechanisms, this four degree-of-freedom (MRI)-compatible patient-mounted and cable-driven manipulator (that we named ROBOCATHETER) seeks to steer cardiac catheters under beating-heart conditions, while suitably addressing the decfiiencies that currently used manipulators vastly suffer from. Following the implementation of a simple ON-OFF and a gain varying PID control schemes to evaluate the performance of the prototyped robot, as one of the main contributions of this dissertation, a gain-scheduling controller is designed and implemented to obtain the desired performance of the slave robot in tracking set points and reference trajectories.The performance of the controller is compared with the variable-gain proportionalderivative-integral (PID) controller. Experimental results show that the proposed control scheme has significant advantages in terms of set point tracking and actuator saturation over the baseline PID controller.
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