Spherical and non-spherical combined two degree-of-freedom rotational parallel mechanism for a microsurgical robotic system

Microsurgery, often performed for anastomosis of small vessels and nerves, requires micromanipulations of small tissues and thus requires highly specialized surgical skills. Robotic technology has great potential to assist with microsurgical treatments because of the high accuracy provided by robots; however, implementation remains challenging because the technical requirements of robotic surgery are far different from those in industry. One of the greatest challenges is that two surgical tools (e.g., tweezers) must be precisely and deftly moved around the surgical area in seven degrees of freedom (DOF) using one DOF to grasp each tool, and these tools are used in close proximity to each other. Additionally, high accuracy and rigidity at the tool tip are imperative for successful performance of the microsurgical procedure. In this study, we propose a new rotational two-DOF parallel mechanism that has the inherent advantages of a parallel mechanism, namely accuracy and rigidity, within a newly proposed spherical and non-spherical combined parallel structure to prevent collision of the two mechanisms in a dual-arm setup for microsurgery. The prototype was evaluated by performing a series of mechanical tests, and microsurgical suturing was performed by a microsurgical robotic system. The series of evaluations demonstrated the feasibility of the proposed mechanism.