Design And Master-slave Control Strategy Of A Single-port Surgical Robot With Controllable Stiffness Manipulation Arms

The limitation of single-port access puts a higher technical requirement for the development of single-port surgical robot.Single-port surgical robot has to integrate more degrees of freedom(DOFs)in a more limited range,provide adequate operational accuracy and operational force in a more restricted space,provide the ability of handeye coordination consistency in a highly integrated system.Based on the above needs and aiming at the national major project strategy and scientific frontier,this paper has conducted the complete development of a single-port robotic system which could meet the requirements of minimally invasive surgery,including the surgeon console system,slave robot system,vision system,control system,controllable stiffness manipulation arms and robot-assisted anastomosis system.The method of integrating controllable stiffness function into the manipulation arm is proposed.The main work of the thesis includes the following sections: 1.The design method of the controllable stiffness single-port surgical robot is proposed.Based on the analysis of clinical operation mode,access mode of single-port operation and the analysis of "Y" configuration of single-port surgical robot,the key design requirements including DOFs layout,clinical geometric parameters and operation forces are put forward.Based on the clinical requirements,the configuration type of controllable stiffness manipulator arm,controllable stiffness principle,coupled wire-driven method and integration design method of the manipulation arm are analyzed.Moreover,the mechanical model of the flexible joint is analyzed to provide the theoretical basis for the selection of key design parameters.2.The kinematic analysis method for the controllable stiffness single-port surgical robot is established.Based on the configuration of the controllable stiffness manipulation arm developed in this paper,the kinematic model and general analysis method are established.The kinematics and instantaneous kinematics of the manipulation arm constructed by flexible-articulated hybrid joints,are deduced using the screw theory and the exponential product formula.The mapping relationship between the triple space is analyzed.3.The master-slave control strategy for the controllable stiffness single-port surgical robot is established.The intuitive mapping strategy of "seeing and moving" is realized and the proportional incremental control method is realized to promote the precision of control.Aiming at key safety issues during operation using the single-port robot,a control method of improving the safety of the operation is put forward.The overall control flow is developed,and the hardware and software system architecture are analyzed.4.A robot-assisted stapler for soft tissue anastomosis is developed as a specified manipulation arm for the single-port surgical robot,and anastomosis quality is optimized.By the intelligent control method,the key process parameters in the soft tissue anastomosis process can be effectively controlled,thus improving the quality of intestinal tissue anastomosis.The mechanical model of soft tissue anastomosis,the finite element model(FEM)and geometric model of the stapled staple are established.The optimization method of soft tissue anastomosis is established based on the scoring method.5.A complete experimental study on the controllable stiffness single-port surgical robot is carried out.The experimental results show that the shortest rigid/soft switching time is 5s.The stiffness of the manipulation arm in rigid state is 3.02 to 4.12 times higher than that in the soft state,and the ultimate payload of the manipulation arm is 10 N.Positioning accuracy experiment and master-slave mapping experiment verify the correctness of theoretical analysis of kinematics and mater-slave control strategy,and that the stability of the manipulation arm in the rigid state is obviously higher than that in the soft state.The ex-vivo animal tissue experiment shows that the single-port surgical robot can provide good rigidity,stability and sufficient extraction force in the rigid state,and can provide good dexterity and flexibility in the soft state.The controllable stiffness single-port surgical robot and its anastomotic instrument developed in this paper can meet the requirements of typical operation tasks of minimally invasive surgery.