Modeling, design and experiment of a remote-center-of-motion parallel manipulator for needle insertion

In surgical procedures such as brachytherapy, biopsies and drainages, how to precisely place the needle inside the body is crucial for the performance of such surgeries. In last two decades, robot-aided needle placement has gradually been a trend for better security and accuracy. However, existing successful medical robot systems leave some common drawbacks: expensive, bulky, and high operation complexity, which motivates the development of more compact, affordable, and functional robots. This paper introduces a novel robot based on a 2-CRRR-CRR parallel manipulator (PM) for single needle insertion with high accuracy, where C denotes a cylindrical joint and R a revolute joint. Via screw theory, the mobility of the robot is analyzed, which meets the requirement of remote-center-of-motion (RCM). Its kinematic analysis is presented and singular configurations are identified based on the Jacobian matrix. Furthermore, the link dimensions of the robot are optimized by considering motion/force transmissibility and practical limits to generate singularity-free and high-performance workspace around the incision point. The design and feasibility of the proposed robot are validated by preliminary motion experiments with a prototype. The two advantages of the proposed robot are a singularity-free workspace with good motion/force transmissibility and high rigidity due to three fixed linear actuators in parallel architecture.