A Robotic System for Transanal Endoscopic Microsurgery: Design, Dexterity Optimization and Prototyping

This paper proposes a master-slave operated robotic system that features the novel slave manipulator with a modular distal continuum section to address the shortcomings of traditional transanal endoscopic microsurgery (TEM). The slave manipulator consists of two 7-DoF surgical instruments and a 5-DoF endoscopic arm that are designed with distal continuum structures and unfolded with a Y configuration after inserting through a transanal port to enhance hand-eye coordination and instrument triangulation. The proposed robot is designed for adaptation in narrow and shallow rectal spaces, facilitating intuitive hand-eye coordination and enhanced operational dexterity with reduced obstruction of the field of view. A novel hybrid coaxial continuum unit (HCCU) has been designed to offer excellent bending characteristics and structural stiffness. This unit has been developed as a modular design and supports different connection configurations to form the multi-DoF surgical instruments and endoscopic arm. FEA-based structure optimization has been implemented to improve the mechanical performances of the HCCU unit. Dexterity optimization under anatomical constraints is proposed to improve the maneuverability of the multi-DoF distal continuum section. Experimental investigations on bending and anti-twisting performances on the designed HCCU joint are carried out. The average error value of distal positioning within [- 100°, 100°] does not exceed 1.10%, and the torsional stiffness is 6.86 mNm/°. The payload capability of the surgical instrument has been investigated to demonstrate a maximum value of 5 N. The robotic system is prototyped and the trajectory tracking experiments have been performed to validate its positioning accuracy. The user study has been investigated, and the simulated operation tasks that include grape peeling and suturing operations as well as apricot suturing and threading operations, have been performed. The experimental results demonstrate its potential to be utilized in TEM surgery with an extensive surgical field of view and excellent maneuverability.