Magnetically-Connected Modular Reconfigurable Mini-robotic System with Bilateral Isokinematic Mapping and Fast On-site Assembly towards Minimally Invasive Procedures

This paper presents a modular and reconfigurable mini-robotic system with 5 degrees of freedom (DoFs) towards minimally invasive surgery (MIS). The mini-robotic system consists of two modules, a 2-DoFs rotational end-effector, and a 3-DoFs positioning platform. The 2-DoFs rotational end-effector is based on a spring-spherical joint mechanism, whose rotation is controlled by Bowden-cable. The 3-DoFs positioning platform is based on the linear Delta parallel mechanism. Magnetic spherical joints are adopted to replace the traditional spherical joint. The magnetic joint connections enable fast assembling and disassemble of the end platform and kinematic chains. Different surgical instruments can be installed without changing the driver and control system. A flexible shaft actuates the 3-DoFs positioning platform to arrange the motors away from the manipulator side. Based on these structure characteristics, the 3-DoFs positioning platform's size is dramatically reduced. The outer diameter of the current prototype is 32.5 mm. The single-axis positioning accuracy of the 3-DoFs positioning platform is within -1 mm to 0.85 mm. Three axes tracking experiments are also carried out, with the positioning errors of ± 1.2 mm for cylindrical curves and -1.5 mm to 2 mm for spherical helix curves. Static and dynamic load capabilities are also tested. Finally, the feasibility of the proposed system is demonstrated.