Adaptive control of a master-slave system for teleoperated needle insertion under MRI-guidance

This paper presents the control of a master-slave system for teleoperated needle insertion under guidance by Magnetic Resonance Imaging (MRI). The primary aim of our research is the robot-assisted laser ablation of liver tumors. The master-slave system consists of a master unit that sits next to the operator, outside the scanner room, and of a slave unit located inside the cylindrical MRI scanner. The needle insertion force is measured with a specially designed fiber optic force sensor mounted on the slave unit. Pneumatic actuation is employed in both master and slave in order to minimize the interference with the MRI environment. Accurate position control of the slave unit is achieved with a Time Delay Control scheme (TDC). Differently from previous designs, the force feedback on the master unit is provided by an adaptive controller that compensates the friction of the pneumatic actuator. The advantages over a baseline force controller are demonstrated with experiments on silicone rubber phantoms.